| judtoff |
| Thanks for posting, I read the post in the collaborative thread and found it interesting. Keep us informed! |
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| zobsky |
I thought your were going to put this together in an hour :)
Seriously though, let us know when you have this project up and running, .. I have two of those MCM drivers working in different "Tuba" horns. |
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| Patrick Bateman |
| quote: | Originally posted by zobsky
I thought your were going to put this together in an hour :)
Seriously though, let us know when you have this project up and running, .. I have two of those MCM drivers working in different "Tuba" horns. |
I built a clone of the Autotuba too. That's a fun sub box. Used it in my old Accord for about six months. When I bought a new one I made a new sub, using the same driver, but tweaked it so that it would play deeper.
Because the Autotuba's response falls so quickly, it has a lot of "slam" and efficiency, but lacks the deep bass that carfi guys know so well. You might get the best of both worlds if you used EQ to "cut" the midbass though. I was a bit concerned about frying the driver, because I was feeding it about 800 watts! (it's rated for 100 IIRC :) |
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| Patrick Bateman |
Bad news - I had second thoughts about the viability of this, so I went back to the drawing board.
Good news - I solved the problem.
Here's how I did it.
Anytime you're building a horn, you're juggling a bunch of variables. If you want efficiency, you have to sacrifice extension. If you want to make it smaller, the response gets ragged. You can smooth the response with careful use of a taper, but that makes the box harder to build.
Building horns is tricky.
In the design I posted, with a single woofer, I felt the response was too ragged. It was easy to build, but I was worried it wouldn't sound good. I tried fixing that by reducing it's efficiency. Reducing the efficiency smooths the response of a horn. I reduced the box efficiency by adding a second driver in the same horn, basically halving the airspace for each one. That worked well, but the efficiency wasn't much better than a bandpass.
Then I tried a trick Dan Wiggins recommends. I added a resistor to the circuit, which raises the QES (and the QTS.) That worked great! By raising the QTS FROM .24 TO .60, the response of the tapped horn was much smoother. Of course efficiency suffers, but I'll take smooth response over efficiency any day! Another bonus is that you could adjust the QTS value by changing the resistor value. Even better, this gives me an easy load for my amp to drive, which is particularly important since I intend to use three or four subwoofers (per Geddes.)
The resistor value is five ohms; I intend to use two 10ohm resistors in parallel, which you can get from any ol' Radio Shack. |
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| Eva |
| Consider modifying your amplifier to simulate 5 ohms output impedance. |
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| Patrick Bateman |
In case anyone's curious, here's how you model the size of the resistor.
http://www.diysubwoofers.org/dipole/design.htm
To increase the Qts to the target value, we can use a series resistor Rs, and calculate its value as follows:
Qes'=Qts'*Qms/(Qms-Qts')
Qes' = 1.75*7/(7-1.75)
Qes' = 12.25/5.25
Qes' = 2.33
Rs = Re*(Qes'-Qes)/Qes
Rs = 2*(2.33-1.30)/1.30
Rs = 2*1.03/1.30
Rs = 1.6 ohms
As we plan to drive the system with 100W of power, assuming 10:1 differences between average and peak levels, we can use a 10W or greater resistor for Rs. |
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| Patrick Bateman |
Here's the math for figuring out the resistor with the MCM speakers. In a nutshell you need a 5.67ohm resistor - I just rounded down to 5ohm since they're easy to find at
First, here are the specs of an MCM 55-2421:
John Krutke posted these specs a few years back; I have personally measured half a dozen of my woofers, and they're in sync with his measurements.
Fs=30.95 hz
Qms=12.2863
Qes=0.2365
Qts=0.2320
Vas=23.88 l
SPL=86.59 1w/1m
Re=3.4
Le=2.42
BL=13.15
Xmax=16mm P-P
To increase the Qts to the target value, we can use a series resistor Rs, and calculate its value as follows:
Qes'=Qts'*Qms/(Qms-Qts')
Qes' = 0.6*12.28/(12.28-0.6)
Qes' = 7.37/11.68
Qes' = 0.63
Rs = Re*(Qes'-Qes)/Qes
Rs = 3.4*(0.63-0.2365)/0.2365
Rs = 3.4*0.3935/0.2365
Rs = 5.657 ohms |
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| Patrick Bateman |
Here's my original post, from months ago. NOTE I've modified it to reflect the new design, which is 25% longer. In all other respects, it's identical to my original proposal.
This is my design for a tapped horn using the MCM 55-2421, which I still believe is one of the best horn drivers available. The fact that it's $25 is a bonus.
The goals of this design were different than what a lot of you guys are going for. This one is optimized to be as small as possible. It's also INCREDIBLY simple to build. It's a eight foot tall sonotube, with a plywood divider running down the middle. There isn't even a taper! Because it's efficiency is lower than most tapped horns (about 96db) you don't get a lot of ripple.
I think this tapped horn would be great for car stereo too, but you'd have to come up with a novel folding scheme. (Unless you can figure out a way to squeeze an eight foot long subwoofer into your car!!)
So here's how to build it:
1. Get a 8ft tall sonotube that's 10" across
2. Get a piece of plywood, cut it to 10" x 90"
3. Cut out a 7.5" hole for the woofer. The location of the hole is very important. The centerpoint of the hole must be 18" from the end of your 90" piece of plywood.
4. Put the two MCM woofers in the hole
5. Put the plywood divider right inside the sonotube
6. Cap one end of the sonotube completely. Leave a 5" gap between the end cap and your piece of plywood
7. Put a cap on the other end that covers up one HALF of the sonotube
8. That's it! |
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| Patrick Bateman |
Before I post my design I gotta warn ya'.
You guys have seen some of the crazy outrageous I've done - I'm a big fan of crazy waveguide projects that take ages to finish.
But this sub project is S-I-M-P-L-E.
Yes, I could have made it flatter. Yes, I could have made it play lower. But to do that, I would have made it a LOT more difficult to build. And I need at least three of these, and I really don't want to spend my entire Summer building subwoofers.
So...
It's not perfect.
But IMHO, you're not going to find a tapped horn that's easier to build, and you sure as hell aren't going to find a subwoofer that can be built for $50 that can outperform this monster.
Yes, FIFTY BUCKS kids. The driver is $25, the sonotube will set you back about ten bucks, throw in another $15 for wire, wood, carpet and terminals.
FIFTY BUCKS.
IF you want to make it better, go right ahead. Increasing the taper will flatten the response, but will also raise the F3 and make it MUCH harder to build. You can double the power handling by adding a second woofer, but then you'll have to tweak the resistor to lower the QTS of the system.
Without further ado, I present The Tapped Horn for Dummies |
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| PeteMcK |
Patrick, I tried this a few years ago with 6" plastic pipe & 4" drivers, I put a 'Karlson slot' at the 'output' end. I made the pipes 1.2m high in the hope of getting down to 40Hz.
Now I have a bit more knowledge & a 2m length of 12"pipe, I was thinking of trying again with better drivers.
I'm interested to understand why you see this as a 'tapped horn' rather than a transmission line?
Cheers,
Pete McK |
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| GM |
| quote: | Originally posted by Patrick Bateman
There isn't even a taper! Because it's efficiency is lower than most tapped horns (about 96db) you don't get a lot of ripple. |
This is a tapped PIPE (or TL if you prefer) as I've suggested and shown a few designs of on the tapped horn thread (see links for one of them) and I assume since you put two drivers in one hole that it's an isobaric TP.
As for the ripple, the ones I did sure simmed a lot of HF 'hash', though never having built one I don't know how bad it is in reality.
Note too that Al (pinkmouse) built one I did for him and it performed/measured very poorly, though there seemed to be some question as to how airtight it was, so he was going to get back to us, but that was months ago and he's been MIA on the thread ever since.............
http://www.diyaudio.com/forums/show...597#post1391597
http://www.diyaudio.com/forums/show...598#post1391598
GM |
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| Patrick Bateman |
There's a glitch in my post. I went back and forth between using one woofer and two. I'm using ONE woofer for the project.
The MCM woofer is designed for such a tiny box - when you use a single woofer there's a lot of ripple in the response due to this.
The resistor flattens out the response quite a bit by raising the QTS of the woofer. (A higher QTS requires a bigger box or horn.) |
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| Patrick Bateman |
| quote: | Originally posted by GM
This is a tapped PIPE (or TL if you prefer) as I've suggested and shown a few designs of on the tapped horn thread (see links for one of them) and I assume since you put two drivers in one hole that it's an isobaric TP.
As for the ripple, the ones I did sure simmed a lot of HF 'hash', though never having built one I don't know how bad it is in reality.
Note too that Al (pinkmouse) built one I did for him and it performed/measured very poorly, though there seemed to be some question as to how airtight it was, so he was going to get back to us, but that was months ago and he's been MIA on the thread ever since.............
http://www.diyaudio.com/forums/show...597#post1391597
http://www.diyaudio.com/forums/show...598#post1391598
GM |
Thanks for the heads up. I was going to build three right off the bat; maybe I'll build one and measure it before I commit to a set. |
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| Patrick Bateman |
| quote: | Originally posted by GM
This is a tapped PIPE (or TL if you prefer) as I've suggested and shown a few designs of on the tapped horn thread (see links for one of them) and I assume since you put two drivers in one hole that it's an isobaric TP.
As for the ripple, the ones I did sure simmed a lot of HF 'hash', though never having built one I don't know how bad it is in reality.
Note too that Al (pinkmouse) built one I did for him and it performed/measured very poorly, though there seemed to be some question as to how airtight it was, so he was going to get back to us, but that was months ago and he's been MIA on the thread ever since.............
http://www.diyaudio.com/forums/show...597#post1391597
http://www.diyaudio.com/forums/show...598#post1391598
GM |
Well I don't want to build junk, so I did a bit of redesigning. I still want to keep it simple, but integrated a taper by putting the center panel a bit off center. This basically creates two sides of the pipe, one that's double the size of the other.
Voila! Two to one taper.
I also found that Home Depot and Lowes have Sonotubes that are 9.5" in diameter. That's what I'm using instead of ten inch. The reduction in diameter flattens out the response further, since these MCM woofers really want a small box.
Parameters attached. |
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| Patrick Bateman |
| frequency response |
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| GM |
| quote: | Originally posted by Patrick Bateman
The resistor flattens out the response quite a bit by raising the QTS of the woofer. (A higher QTS requires a bigger box or horn.) |
Yeah, there's 'no replacement for displacement' down low and it takes a minimum box size for a given ~flat gain BW, so either Vas or Qts must go up to 'fill' it if you want it ~flat, with increasing the latter being the easiest for the DIYer.
GM |
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| GM |
| quote: | Originally posted by Patrick Bateman
Thanks for the heads up.
Well I don't want to build junk, so I did a bit of redesigning. I still want to keep it simple, but integrated a taper by putting the center panel a bit off center. This basically creates two sides of the pipe, one that's double the size of the other.
Voila! Two to one taper. |
You're welcome!
I didn't mean to scare you off as I don't see anything fundamentally wrong with the TP concept and apparently the math doesn't either according to Hornresp, just that Al's build highlights how sensitive to variables any tapped pipe/horn build can be and unfortunately he hasn't let us know where his might have gone awry.
I'm still probably up to at least a year away before I'll be set up to build/measure again, so was hoping someone in the meantime would give these a shot since they are so cheap/simple to build.
If I'm understanding you, the baffle is just made narrower and offset to create a stepped pipe rather than the tapered one simmed, so it will be interesting to see how it measures Vs the sim.
Anyway, thanks for sharing as so far outside the few on the TH thread that have taken the 'plunge', folks I've suggested THs to have proven way too intimidated by such simple box builds once one or more internal angled boards are added. :(
Maybe if we call them shelf braces instead..............
GM |
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| gedlee |
| quote: | Originally posted by Patrick Bateman
frequency response |
John
That just looks like a badly tuned bandpass. Why not just build a bandpass? They have worked well for me. |
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| Patrick Bateman |
| quote: | Originally posted by gedlee
John
That just looks like a badly tuned bandpass. Why not just build a bandpass? They have worked well for me. |
Huge efficiency gain. These woofers are something like 84db efficient.
Admittedly, these will work nicely in a bandpass - but at much lower efficiency. |
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| gedlee |
How so? Bandpass is an efficiency boost and in fact I would say that I could get as much as you are getting but in a much smaller package.
I don't see where the efficiency comes from. Because the "port" is a horn? But at these frequencies the horn is just a single lumped mass, just like a port, there is no gain. |
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| Patrick Bateman |
| quote: | Originally posted by gedlee
How so? Bandpass is an efficiency boost and in fact I would say that I could get as much as you are getting but in a much smaller package.
I don't see where the efficiency comes from. Because the "port" is a horn? But at these frequencies the horn is just a single lumped mass, just like a port, there is no gain. |
The efficiency bump is because we're getting useful output from both sides of the cone.
This was something that I found interesting about dipole subwoofers, which I'd never considered. If the baffle is large enough, it can be more efficient than a sealed box, because we're getting output from both sides.
I modeled this in Mathcad using Martin King's worksheets and it confirmed this.
(www.quarter-wave.com)
Upstairs in my new home I have a baffle that's the size of my king bed that's a dipole sub. It's literally under the bed - talk about stealth! The efficiency on this thing is HUGE. It literally shakes the house. Of course part of this is because it's radiating right into the floor.
This set of subs will go in the living room downstairs, which is where I have the Summas.
Now you could argue that a DUAL reflex bandpass would be nearly as efficient, which is true, but I've always thought they sounded "weird." I built a few back in the early 90s, when Peter Mitchell turned me on to your work. That was actually what inspired me to learn your work, was reverse-engineering bandpass subs fifteen years ago. |
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| gedlee |
John
This just doesn't sit right with me. Dipoles have a very low radiation efficiency so it seems to me that they could never equal a monpole. I've always thought that the "both sides of the diaphragm" argument was flawed because it ignores that fact that these two sides are out of phase and that getting them in-phase to radiate efficiently is no small feat. The dual bandpass system cannot achieve any greater output that a single, it can just extend this output a little lower - just like a ported enclosure, but it does so at the cost of a dipole roll-off rather than a monopole.
I have found since I switched to all monopole outputs that I prefer the results.
The Acoustic Lever - now that does add a lot of efficiency. Real honest to goodness monopole efficiency. Some day those will dominate the landscape. |
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| Patrick Bateman |
| quote: | Originally posted by gedlee
John
This just doesn't sit right with me. Dipoles have a very low radiation efficiency so it seems to me that they could never equal a monpole. I've always thought that the "both sides of the diaphragm" argument was flawed because it ignores that fact that these two sides are out of phase and that getting them in-phase to radiate efficiently is no small feat. |
The tapped horn is quite a clever invention I'd say. It's true that it's challenging to get both sides to radiate in phase, but I'd have to say that Danley has come up with a clever way of doing it.
99% of the programs out there ignore where the port is located. One thing that's intrigued me about hornresp and Martin King's worksheets is that they factor it in.
For instance, let's say you build two vented boxes. Each has the same driver and the same volume. One has the port located near the cone; the other is an eight foot tall sonotube and the port is located on the other side of the enclosure. The in-room response of the sonotube sub will be different because there's a 7msec delay introduced by the distance from the port to cone. This delay will do some interesting things to the in-room response. In addition, the *direction* of the port has some interesting ramifications, due to high frequency peaks radiated via the port.
King's software in particular is quite clever, and easier to use than hornresp IMHO. Unfortunately it can't model tapped horns. It CAN model transmission lines, and I've long thought that the tapped horn is quite close to a transmission line (but not quite.)
If I can find a few minutes I should throw together some comparisons with Martin's software to see how it models the hypothetical vented box described above. |
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| Patrick Bateman |
I fired up my favorite program for modeling bandpass subs quickly - bandpass boxmodel. I actually bought this program when I was a teenager, as mentioned above, was trying to reverse-engineer bandpass subs. Nowadays it's free.
Using a "textbook" bandpass we can get fairly flat response, as the pic shows. The efficiency is very VERY low though; about 82db. The box is impressively small though; just a hair over four liters! These MCM subs love stupid small enclosures.
The F3 is too high though; just 49hz. Not much of a "sub" woofer.
To optimize this sub I'd probably do what I did with the tapped horn - add a resistor to increase QTS, which will extend the low end response. The resistor will also make the enclosure size more manageable, as a five liter enclosure contributes to a ridiculously long port. |
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| gedlee |
I've spent more than a little time with transmission lines and from what I can tell they just don't pan out. Sure a port some feet away will be "different", but thats totally unpredictable and completely room dependent. There will be modes that this distance will excite better and those where it will excite less. I just don't see that a general trend can be established.
To me there is simply no way to uncouple the source problem from the room problem at very low frequencies and I am now firmly of the opinion that multiple monpoles cannot be beat for efficiency and smoothness. It would take a lot of data to get me to believe otherwise since I have a lot of data to support this position.
SPEAK has always been able to model transmission lines and in playing around with them I was never able to get anything useful. They can even do damping at different locations in the line (although this feature is not obviuos as to how to imliment).
I looked at the tapped horn briefly and I agree that to me it was a transmission line. Horns at low frequencies, like in your example, just don't work as horn. They are too small and only act as very big ports. Of course big ports are a good thing - lower loss - but a straight port is a lot easier to build if it works the same as a horn. |
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| gedlee |
| quote: | Originally posted by Patrick Bateman
I fired up my favorite program for modeling bandpass subs quickly - bandpass boxmodel. I actually bought this program when I was a teenager, as mentioned above, was trying to reverse-engineer bandpass subs. Nowadays it's free.
Using a "textbook" bandpass we can get fairly flat response, as the pic shows. The efficiency is very VERY low though; about 82db. The box is impressively small though; just a hair over four liters! These MCM subs love stupid small enclosures.
The F3 is too high though; just 49hz. Not much of a "sub" woofer.
To optimize this sub I'd probably do what I did with the tapped horn - add a resistor to increase QTS, which will extend the low end response. The resistor will also make the enclosure size more manageable, as a five liter enclosure contributes to a ridiculously long port. |
John
Send me the driver data and I'll see what SPEAK says. I don't trust other programs as I have found them incorrect on too many occasions.
What you are showing looks very bad to me. Thats way too much bandwidth for a bandpass. They don't work well beyond one, maybe two octave. But in a narrow bandwidth they really do work well. |
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| Patrick Bateman |
I'm really not trying to scuttle my own project here, but a one dollar resistor makes that MCM woofer VERY attractive in a bandpass.
I've attached a pic which shows the response of the SAME woofer once you bump up it's QTS to 0.6 via an increase in QES.
The difference is night and day - it extends the response a full octave!
Of course you need an enclosure that's five times as big, but that's expected due to the increase in QTS.
The bottom line is that you're looking at a $25 driver that can reach down to 25hz in an enclosure that's barely over a cubic foot.
In 2004 we had a discussion about buying a bunch of cheap subs to implement your multiple sub idea, and this sure looks like a good candidate. I have a hunch that three or four of these $25 subs in small bandpass boxes would clobber the sound quality of a "cost-no-object" subwoofer.
Of course the rich guys should go out and buy three or four "cost-no-object" subs, but that's a whole 'nother ballgame. |
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| Patrick Bateman |
dammit, i'm really starting to wonder if I should build a bunch of these. Here's a pic of the excursion at 25 watts. Keep in mind we're not going to feed these with much power, since I'll be using a minimum of three.
In my humble opinion the biggest advantage of the bandpass sub is something you haven't discussed. The biggest advantage of the bandpass sub is that it's STUPID easy to build. I've made bandpass subs out of sonotube in an evening.
The trickiest part about this tapped horn that I'm building is that it's sooooo looooooong. Because it's eight feet tall, sealing the panel inside of the tube is going to be a b1tch. And if you skimp on the seal, the whole design is RUINED. Any kind of leak is going to be a BIG problem.
My plan was to cut access holes every three feet, seal the inside panel, then replace the access panels. Definitely a p.i.t.a. |
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| Patrick Bateman |
| quote: | Originally posted by gedlee
John
Send me the driver data and I'll see what SPEAK says. I don't trust other programs as I have found them incorrect on too many occasions.
What you are showing looks very bad to me. Thats way too much bandwidth for a bandpass. They don't work well beyond one, maybe two octave. But in a narrow bandwidth they really do work well. |
The extremely wide bandwidth in that first plot is because it's a "textbook" design which would never work in the real world. The volume of the chambers is so small, it would never behave this way in real life. It's because the MCM woofer has a tremendously low VAS combined with a very low QTS. An author for Audio Xpress found this out the hard way a few years ago when he tried to put it in a vented box. The vent wound up being larger than the enclosure!
The resistor seems to help a lot.
Here's the specs I'm using: http://www.diyaudio.com/forums/show...560#post1565560
I personally measured three or four, they're all very close to what Krutke measured. |
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| gedlee |
John
Thanks, but no Sdia - cone area. And you said $25!? That is the right price!!!:) |
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| Patrick Bateman |
| sd is 220 |
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| gedlee |
cm^2
I found the driver on the web. Very attractive.
I'll look into making a sub with two facing a central ported enclosure. This will cancel the box vibrations. I'll do a broad band sub as I think that these are the most important and would work best with this inexpensive driver. Why two? Because I doubt that one could take the output of the plate amp - I know what they claim the power handling is, but I also know what to expect from a 2" voice coil and a cheap driver. |
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| Sheldon |
| quote: | Originally posted by Patrick Bateman
My plan was to cut access holes every three feet, seal the inside panel, then replace the access panels. Definitely a p.i.t.a. |
John,
Why not just slice the tube longitudinally, then glue the two pieces to your flat divider? Easy to control the whole seam this way. You could even taper your cut if you want a tapered tube. There shouldn't be much pressure in the tube, but if you are worried about integrity, it would be simple to wrap the entire reassembled tube with reinforced tape, or for a decorative touch, a nice braided rope.
Sheldon |
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| Mark Seaton |
| quote: | Originally posted by gedlee
How so? Bandpass is an efficiency boost and in fact I would say that I could get as much as you are getting but in a much smaller package.
I don't see where the efficiency comes from. Because the "port" is a horn? But at these frequencies the horn is just a single lumped mass, just like a port, there is no gain. |
Hi Earl,
The tapped horn is most like a 6th order bandpass, and most analogous to a vented box vs. a transmission line comparison. I've been designing plenty of 4th and 6th order bandpasses lately, and there are many similarities and a few differences which can of course work for or against you. For the rest reading along, the important difference lies in the significant distance/lengths involved related to the design vs. the operating bandwidth, so you have to account for 1/4 wave resonances and other effects which again can be problematic or beneficial.
The comparison of a 4th order bandpass to a 6th order makes for a reasonably parallel comparison of a horn and a tapped horn. As with most higher order systems including more variables, they are also easier to screw up, requiring a little more fine tuning or accuracy and completeness in the modeled parameters. |
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| Mark Seaton |
| quote: | Originally posted by gedlee
What you are showing looks very bad to me. Thats way too much bandwidth for a bandpass. They don't work well beyond one, maybe two octave. But in a narrow bandwidth they really do work well. |
Earl,
Is your definition of "work well" implying there is useful gain in sensitivity? I've always seen bandpasses as offering the advantage of allowing the flexibility to trade bandwidth for sensitivity with suitable drivers. While sensitivity is traded off, bandwidth of one decade is certainly possible. |
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| Patrick Bateman |
| quote: | Originally posted by gedlee
cm^2
I found the driver on the web. Very attractive.
I'll look into making a sub with two facing a central ported enclosure. This will cancel the box vibrations. I'll do a broad band sub as I think that these are the most important and would work best with this inexpensive driver. Why two? Because I doubt that one could take the output of the plate amp - I know what they claim the power handling is, but I also know what to expect from a 2" voice coil and a cheap driver. |
When it comes to MCM, it always pays to be a cynic.
I bought TEN which drops the price.
Then I measured four, just to be sure they're consistent (they are.)
Then I sold four on ebay.
IIRC, one of them sold for more than MCM's asking price LOL |
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| gtforme00 |
In case anyone missed it. The 55-2421 is presently on sale for $25 (single piece quantity). I bought one to play with a 6th order bandpass design. To get the discount you will need to lookup the source code for the current flyer (viewable in pdf from MCM)
Just a heads up,
David |
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| gedlee |
| Why don't you just post the code and I'll order some. |
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| littlemike |
| Source Code WA807 |
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| gedlee |
| Thanks, I ordered four of them. I'll check them out. |
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| littlemike |
Hope that they get there without getting beat up. I have had several get bent frames during shipment (that is a lot of magnet and steel hanging off that relatively thin frame). I was able to straighten all but one acceptably, and MCM graciously exchanged that one.
Don't feed them more than about 20 volts during sine sweep testing or you'll let all the magic smoke out. |
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| Pallas |
Another one guys you might want to look at (though it's double the price and then a bit more) is the Peerless SLS8. (There's also an SLS10 that's only a few bucks more.) It seems to have about the same throw, but it also has a shorting ring in the motor and at least the eight I've played with (from at least two different production runs) were extremely consistent from unit to unit. It also has the look and feel of a precision high-performance part, which probably doesn't matter so much in a bandpass but makes some people feel better.
SLS8: http://www.madisound.com/catalog/pr...roducts_id=1386
SLS10: http://www.madisound.com/catalog/pr...roducts_id=1705 |
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| gedlee |
| A shorting ring and the other features don't really mean a thing in a subwoofer. So for twice the price you get ... well twice the price, er ... more than twice the price! I paid 24.95 each. |
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| Jimmy D. |
Could someone design a tapped horn using the MCM 55-2421? I've been wanting to try out THs. I would need a rough sketch or description with dimenstions. Something from the high 30s to about 100 hz would be good and a small as possible footprint would be ideal.
Thanks,
Jim D. |
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| littlemike |
Based on my experience with the 55-2421 in a TH, it is not the best driver for the job. It does work, but does not play as loud or low as a number of other drivers. That being said - the TH I have has the 55-2421 in it.
Have you tried your hand at hornresp yet? The latest version is quite easy to use, especially with the design of a tapped horn (which is an iterative process - there is no optimum design that I am aware of)
Certainly, I am no pro with tapped horns. Others may have better design ideas than I do. |
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| GM |
Hmm, while I agree that the 2421 has an excess of HF BW capability, I don't see that as a reason not to use it, especially since it doesn't run out of Xmax until the far side of 130 dB in the desired passband if it doesn't let its smoke out first, which is more than plenty for typical HIFI/HT apps. Pretty impressive for only a ~81.51 L net bulk! I've built 'bookshelf' speakers bigger than this.......
GM |
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| littlemike |
Thanks for the additional insight. An exponential design sure smooths things out when compared to simple conic flares. I am still very much on the steep part of the learning curve with respect to tapped horns, so please bear with me. I have not read _all_ of the collaborative thread (though I do recall seeing you as a regular contributor), but try to get a few pages read here and there when I can.
The only real issue I have with the response of a 55-2421 in a tapped horn is the 5 dB step in response that is typically predicted around 100 Hz, which is right where my mains cross in. I am aware that the resonances predicted in Hornresp may not exist/can be altered through folding, but not all of the drivers I have modeled exhibit this step in response.
Based on my limited understanding of tapped horn design, the throat in your simulation seems very small - only 1/7 of the driver's Sd. Won't a throat that small kill the driver in a bass horn (torn cones or surrounds)? Have I missed something? I have never ventured that far down that path - I have limited myself to a minimum throat area of Sd/4 based on something I read somewhere a while back - think it was something Cowan recommended. It does dramatically reduce the excursion, but I am sure that there must be some commensurate increase in cone pressure.
Have you built and measured one of these?
If not, I will have to, as I have plenty of 55-2421's and a few sheets of plywood. As usual, all I lack is the time to do so. While punching keys and pushing pixels is a great way to play, I really only manage to learn when I actually build and test something (often to the limit - hence my magic smoke story).
Thanks again for your insight. |
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| GM |
You're welcome!
Indeed it does, though at the expense of gain BW for a given path-length. Not many 'free lunches' in sound systems design.
The stepped response is the price you pay for a small net bulk, i.e. there's only true horn loading in its HF BW. Design it as a max gain BW TH where Fs = Fc and watch it smooth right out, though now its size will be measured in thousands of liters just like a traditional 'ideal' bass horn.
Bottom line, as in any optimum speaker alignment you want to use the right driver for the app and if you can't find or mod an existing one to suit, then you either accept its trade-offs and work around them as TD does with his DTS-20 or rethink your system design.
IIRC 'JH' posted that while the HF 'ripple' wasn't nearly as bad as predicted, the folds didn't have much (any?) affect on them either like in a typical folded horn. Not surprising considering the typical driver-in-mouth TH designs that folks here seem to prefer.
No, my speaker design/building avocation for a variety of reasons has been on hold for many years now, so my postings are based on what I think I know about TL, horn, etc. design from prior experience and of course the much appreciated published efforts of others and last, but not least, rely on Prof. Leach's well proven math to calculate the throat, etc., values of any low frequency horn alignment.
Note that just plugging numbers into his math will probably not give you a viable alignment or even a decent starting point, especially WRT TH alignments, i.e. GIGO applies (garbage in/garbage out), hence the tiny throat predicted (the byproduct of a low Qes/Qts) would probably quickly destroy even a 'bullet-proofed' horn driver if used in a prosound app and probably cause audible distortion via surround deformation using a thin, high compliance half roll one, but the 2421 is robust enough for prosound apps, so I see no reason why it wouldn't be fine for a much less stressful HIFI/HT one. Only one way to know for sure though.........
Yeah, not being math savvy enough to learn from acoustic engineering textbooks I was forced to make many 'proof-of-concept' cabs to create enough of a pattern of each type of basic alignment to see trends, which then allowed me to skim past much of the higher math to design conservative alignments I could tweak to suit since making something acoustically smaller was far easier than stretching it to sound big enough.
GM |
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| Jimmy D. |
Greg,
Could you please email me? (You designed a cabinet for at 515-8G a couple years back for me.)
Thanks,
Jim D.
jrclwd@embarqmail.com |
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| Jimmy D. |
Can someone define the parameters required to design a TH box from GM's simulation in Post 49?
Thanks,
Jim |
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| Patrick Bateman |
| quote: | Originally posted by Jimmy D.
Could someone design a tapped horn using the MCM 55-2421? I've been wanting to try out THs. I would need a rough sketch or description with dimenstions. Something from the high 30s to about 100 hz would be good and a small as possible footprint would be ideal.
Thanks,
Jim D. |
Hmmm, where to start with this one?
I started a thread called "Tapped Horn for Dummies" because all the tapped horn designs on William Cowan's thread were no good for people who weren't good with a table saw. So this design is ideal for beginners, and you guessed it, it uses the very woofer you're asking about.
I'm listening to my tapped horns as we speak.
Construction plans are here : http://www.diyaudio.com/forums/show...695#post1565695
That's page 1 of the thread.
I'll post pics soon... |
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| aznboi3644 |
| I still don't understand how this enclosure is assembled. Could we get some more pictures |
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| Patrick Bateman |
| quote: | Originally posted by aznboi3644
I still don't understand how this enclosure is assembled. Could we get some more pictures |
I need to find the reader for my camera. 'Til then, it boils down to this:
#1: Get a 8ft tall sonotube that's 10.5" across. Home Depot doesn't sell eight foot long sonotubes, so just buy two that are four feet tall. Also, bring your tape measure with you. The sonotubes at Home Depot and Lowes come in various sizes. The ones that are labeled 10" are actually 9.5", 10", and 10.5". The reason they do this is because it allows them to put more on the shelf. You want the ones that are 10.5" across, not 10" across.
2. Get a piece of plywood, cut it to 9" x 90". I used 1/2" stock. You could use MDF too I guess. I like plywood because it doesn't split as easily as MDF.
3. Cut out a 7.5" hole for the woofer. The location of the hole is very important. The centerpoint of the hole must be 16" from the end of your 90" piece of plywood. See this pic here, from the 1st page of this thread?
http://www.diyaudio.com/forums/atta...tamp=1216524591
Note that L1 is 50.8cm, which equals 20". Our hole is at 16" because that's the center of our 8" woofer. Get it? 20" - 4" = 16".
4. Put the MCM woofer in the hole
5. Put the plywood divider right inside the sonotube
6. Cap one end of the sonotube completely. Leave a 5" gap between the end cap and your piece of plywood. The reason there's a five inch gap is that a five inch gap is equivalent to the midpoint of our tapped horn.
7. Put a cap on the other end that covers up one HALF of the sonotube. The reason that we're covering all of one end and half of the other end is that the mouth of our tapped horn is on one side. If you covered up the whole thing it wouldn't work too well :)
8. That's it!
THESE ARE THE FINAL DIMENSIONS. I know I've posted two or three variations on this, but these dimensions are what I'm using for the tapped horn that I'm listening to RIGHT NOW. It's done, it works, it's cheap :D |
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| Patrick Bateman |
A couple o' notes for people who actually build this beast. This is kind of a post-mortem, and things to consider when you build it.
#1 - OMG this thing is more work than I thought. Seriously, I thought I could build two of these in a day and it took me a month to finish one 90%, and the other 50%. (One works but needs carpet.)
#2 - The reason why it's such a P.I.T.A. to build is because it's so TALL and SKINNY. I never even considered this before I fired up the table saw. When you build a horn you need to make that thing AIRTIGHT, and I couldn't figure out any easy way to do this!!! Sheldon recommended cutting the sonotube lengthwise, sealing up the board, then stitching everything back together. That might work for you.
What I wound up doing, which is anything but elegant, is chopping up the sonotube into 9" chunks. The idea was to build it from the ground up (literally), piece by piece. So I stood the board vertically, attached a piece of sonotube with glue and screws, then used plumbers caulk to seal both sides of the board.
If I had to do it again, I'd chop it into 24" chunks. 9" chunks are too small. If you cut it into 24" chunks it's short enough that you can get inside and caulk everything up, but not so short that you'll spend the rest of your life assembling this thing. YMMV
If anyone can come up with a better method of insuring that the enclosure is airtight, I am all ears. This project would be much easier if the sonotube wasn't so narrow. 10.5" doesn't sound that small, but it really is. The inside is so narrow, I can barely fit my arm inside of it. I don't have massive guns, it's just really difficult to work inside of this thing.
Also, if you don't put in the effort to seal this thing properly IT WON'T WORK. PERIOD. It has to be AIRTIGHT.
#3 - If I had to do it again, I might use this woofer instead: http://www.partsexpress.com/pe/show...number=295-456. You see, the whole idea of this project was cheap and easy. Yeah, it's cheap, but damn these enclosure take a long time to build. If you're going to invest a month building a subwoofer, you might as well use a driver that costs more than $25 I think. Having said that, the MCM woofer is a much MUCH better deal than the Dayton. Another thing about this subwoofer is that you'll end up spending $50 on carpet, wood, glue, screws, styrofoam, sonotubes, etc. It seems a little silly to spend $50 on the enclosure and $25 on the woofer.
Does the Dayton offer any huge advantage over the MCM? Not really, just the peace of mind that the build quality is superior, and MCM isn't known for their reliablity. Again, you get what you pay for. |
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| GM |
Please explain again why you didn't make it out of straight cut boards? Folks have been doing just fine with BIBs and Weems style Voigt pipe horns without any angle cuts.
Really, you could probably come up with a design that used standard width boards as I've done for some driver alignments (no TH though), so only their lengths need cutting.
GM |
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| Patrick Bateman |
| quote: | Originally posted by GM
Please explain again why you didn't make it out of straight cut boards? Folks have been doing just fine with BIBs and Weems style Voigt pipe horns without any angle cuts.
Really, you could probably come up with a design that used standard width boards as I've done for some driver alignments (no TH though), so only their lengths need cutting.
GM |
The board is straight. The dimensions are posted above. The tricky part is that you have to be sure that the board and the sonotube are airtight. Because the internal dimensions are so small, and the tube is so long (eight feet!), sealing the board is tricky.
If the board was centered, this wouldn't be a big deal. For example, if the sonotube was 10" across you could cut the board to 10.125" across. The extra eight of an inch would seal the board along the entire length of sonotube, and you'd be good to go! That's because the tube is kinda flimsy, and the board would cause the tube to flex, accommodating the extra width. But the board ISN'T in the middle of the tube, it's off center, so that one side has more volume than the other. That makes construction much trickier. |
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| GM |
I meant why use Sonotube at all? Make it all out of straight boards.
GM |
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| Patrick Bateman |
The usual reasons. A sonotube sub is lighter and stronger than a MDF or plywood sub of the same weight. Whenever possible I use sonotubes for subs.
These subs are MASSIVE. Their footprint is less than one square foot, but they're EIGHT FEET tall. If I built the same thing out of MDF they would be almost unbearable to move.
Also, I live in a three story house, and the idea of hauling three 100lb subs up the stairs isn't too appealing :( |
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| GM |
~100 lbs isn't my idea of 'massive', but I always had a cheap hand-truck for heavy and/or awkward size loads such as my ~245 lb speakers (less drivers), which I have moved by myself up/down stairs before a car accident ended such endeavors.
Anyway, the way I've dealt with your problem is to buy a second one to mount the baffle at each end, trimming off the large side so the seams can easily be sealed up, then glue it up and slide it down the other tube and add the end caps.
GM |
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| Patrick Bateman |
I've been working on this for a few weeks, and I just came up with THE PERFECT SOLUTION!
The problem with a sonotube tapped horn is that the board has to be ABSOLUTELY airtight. When the inside dimensions are small, it's practically impossible to get your arm inside to seal things.
But how's this for a solution:
Cut four discs. Each disk is the EXACT size of the sonotube. So if the sonotube is 10.5", each disk is 10.5". Then you cut the discs down the middle, and attach them to the center board. By doing this, the discs will insure that the sonotube is PERFECTLY cylindrical. And that will solve the problem with gaps between the board and the sonotube.
See, the reason there are gaps is that the sonotube isn't perfectly cylindrical. The discs solve that. In addition, they also reinforce the sub in a big way.
Of course you would have to cut holes in the discs, otherwise they would turn your tapped horn into three six sealed chambers. |
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| winslow |
John, I built my tapped horn in haves and assembled it in my apartment. There was no way I could have gotten the blame thing home if it was in one piece. Sealed it up with silicone and screwed it together.
Also didn't break my back moving the smaller half sections. |
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| Patrick Bateman |
In a strange turn of events, my 2nd tapped horn threw itself off the deck of my house, plunging fifteen feet in the process. This is the first time I've seen a subwoofer commit suicide. Sure, I've murdered a few subwoofers, but never seen one kill itself. I woke up on Saturday morning, couldn't find my tapped horn, only to see it's crumpled body laying in the weeds in front of my house.
Sad really. |
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| agent.5 |
| quote: | Originally posted by Patrick Bateman
In a strange turn of events, my 2nd tapped horn threw itself off the deck of my house, plunging fifteen feet in the process. This is the first time I've seen a subwoofer commit suicide. Sure, I've murdered a few subwoofers, but never seen one kill itself. I woke up on Saturday morning, couldn't find my tapped horn, only to see it's crumpled body laying in the weeds in front of my house.
Sad really. |
Are you sure that this is not an "apparent suicide"? Maybe a hitman is involved. |
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| Nordic |
| quote: | Originally posted by GM
~100 lbs isn't my idea of 'massive', but I always had a cheap hand-truck for heavy and/or awkward size loads such as my ~245 lb speakers (less drivers), which I have moved by myself up/down stairs before a car accident ended such endeavors.
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Hope you have repaired the stairs by now and given up the moonshine. |
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| Patrick Bateman |
Here's a photo of the tapped horn's throat. The duct tape is there because I was too impatient to wait for the plumber's caulk to dry. I'll fix that.
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| Patrick Bateman |
Now THAT'S an ugly subwoofer. Movie screen in the background (I only set up the screen when I watch a film.)
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| Patrick Bateman |
The Gedlee Summas sure look a lot better than my subwoofer. As you can see in the picture, the finish is like a mirror. You can see the reflection of my front yard on the speaker, via the window beyond the speaker.
Tapped horn is in the corner; audio video cabinet in front of it.
I placed a 18sound waveguide there to give you a sense of scale, the Summa waveguides are easily twice as big.
I need to finish two more subwoofers, and carpet them.
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| Patrick Bateman |
Since my 2nd tapped horn commit suicide, I built a pair of bandpass boxes to replace it. They're fairly similar to the boxes I considered on page two of this thread. I built two instead of one since the tapped horn should be much more efficient (and bigger!)
So here are some thoughts on a tapped horn versus a bandpass, using the same woofer:
The first thing I noticed was that the bandpass is more efficient. Which was quite a shock, I was expecting the tapped horn would be a good 3-6db louder. I didn't measure the response, so it's possible that the difference was psycho acoustice, due to fletcher munson curves. Because the tapped horn was *definitely* playing lower than the bandpass.
The second thing I noticed was a buzzing present in the bandpass that was mostly absent in the tapped horn. Both enclosures are quite inert, so I'm guessing that this buzzing sound is either 2nd or 3rd harmonic distortion, or a pipe resonance in the bandpass. It's a sound I've noticed in every bandpass box I've built, going back for years. It's not obvious once you turn on the main speakers, since they mask it. But it's quite prominent when listening to the subs alone.
To make a long story short, the tapped horn sounds pretty darn good. The bandpass box is much MUCH easier to build, but there's definitely something special about the TH.
Having said that, the bandpass IS easier to build, and the tapped horn doesn't appear to have an efficiency advantage over the bandpass. Of course in-room measurements should be done to confirm this.
Also, I checked the tuning frequency of the bandpass, and it's tuned a few hz too high, which gives it an additional DB of output.
I'll fix that in the next few days. |
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| Patrick Bateman |
I just double checked the models, and it looks like the bandpass should have an F3 of 28hz & 70hz, while the tapped horn has an F3 of 18hz & 70hz.
So that confirms what I was hearing, the TH is playing much lower.
Having said that, the efficiency claims of the TH seem hard to believe; according to hornresp the TH is *12DB* more efficient than the bandpass. It doesn't sound like that at all. Also, the bandpass is exactly 1/2 the size. |
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| gedlee |
| quote: | Originally posted by Patrick Bateman
The second thing I noticed was a buzzing present in the bandpass that was mostly absent in the tapped horn. Both enclosures are quite inert, so I'm guessing that this buzzing sound is either 2nd or 3rd harmonic distortion, or a pipe resonance in the bandpass. It's a sound I've noticed in every bandpass box I've built, going back for years.
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John
I am guessing this is turbulence. I am very careful to radius every corner in the ports as not doing so will create a turbulent noise that can be objectionable. I also often use foam in the port to quiet them down. The "smallish" ports on a bandpass are its Achieles Heal.
You comparison is not really fair since the bandpass in the same volume as the TH would go as low. I would expect the two devices to be quite comparable at these very LF in comparable volumes, etc. 12 dB more output from the TH is rather absurd. |
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| Patrick Bateman |
Dr Geddes,
I've become accustomed to this buzzing sound in every bandpass I've built, assuming that it was a pipe resonance or perhaps mechanical noise from the woofer. But I trust your advice so I went and took a look.
First I took a look at the port, and there *was* a lot of turbulence. Which was a surprise, as the computer model indicated that my port was adequate. It turned out the turbulence wasn't from the port, but the SEAL on the port. In my haste I hadn't caulked the seal, and a TON of air was escaping through the seal.
That eliminated 25% of the buzzing, but the tapped horn still sounded more relaxed, while the bandpass buzzed away at the same power levels.
I noticed that the subwoofer was rattling quite a bit on my wood floors, so I pressed my entire weight against the cabinet, while the sub was playing. The idea was to keep it from bouncing off the floor.
And THAT solved the problem!
This buzzing sound was radiating from the end caps of the sontube! Honestly, the difference was night and day. So the woofer was turning the plywood end caps into a 10 inch passive radiator, on both sides of the subwoofer.
I am seriously kicking myself right now, because I've heard this distortion in every damn bandpass I've built for over a decade. If only I'd caught this years ago.
Once I placed some weight on the bandpass sub, to fix the problem with the end caps, the bandpass sub sounds *completely* different. It sounds a couple of DB less efficient, but also appears to be playing deeper, and there's isn't rattle or a buzz to be heard. It's very VERY clean, definitely cleaner than the tapped horn now.
Next up, I'm going to reinforce the heck out of BOTH subwoofers. |
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| Patrick Bateman |
Here's the details on the bandpass sub. It's stupid easy to build. I put two of them together in under six hours with nothing more than a jigsaw, a drill, and a handsaw. One sub is about 80% complete, the other is about 50%. It is easily 10x easier to assemble than the tapped horn, which is MUCH more difficult to build than I realized.
First off, the bandpass sub requires modifications to the MCM 55-2421 woofer. In a nutshell, I add mass to lower the FS and raise the QMS, then I add a resistor to raise the QES. These modifications make it work much better in a single-reflex bandpass.
The front chamber of the sub is 15.8 liters.
The rear chamber of the sub is 34.1 liters.
The front chamber has a vent which measures 22" in length and 3" in diameter. The volume of the vent is 212."
The rear chamber is sealed; the woofer is in the rear chamber, and takes up 113".
The total volume of the front chamber, including the port, is 1176" (964" + 212").
The total volume of the rear chamber is 2194".
I juggled all the numbers so that this sub needs exactly ONE sonotube :D
The rear chamber is 31" in length; the front chamber is 17" in length. Note that you'll have to use a 180 degree turn to fit a 22" port into a chamber that's 17" long. No, I didn't factor in the volume of the front cap and the end cap, but it certainly wouldn't make more than a half DB difference :P |
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| Patrick Bateman |
| quote: | Originally posted by gedlee
John
I am guessing this is turbulence. I am very careful to radius every corner in the ports as not doing so will create a turbulent noise that can be objectionable. I also often use foam in the port to quiet them down. The "smallish" ports on a bandpass are its Achieles Heal.
You comparison is not really fair since the bandpass in the same volume as the TH would go as low. I would expect the two devices to be quite comparable at these very LF in comparable volumes, etc. 12 dB more output from the TH is rather absurd. |
I wonder if some of the shockingly high SPL numbers that people are getting with their tapped horn simulations are due to everyone assuming perfect corner loading with their simulations? Did you see this post:
http://www.diyaudio.com/forums/show...070#post1488070
This project has definitely made me re-evaluate what's important in a subwoofer design. Off the top of my head, here's what I think at the moment:
- The tapped horn is a very cool design for prosound, where absolute maximum SPL in the smallest and lightest package is king.
- Tapped horns in the home are a bit silly - they're just more trouble than it's worth. They're too damn difficult to build. As I see it, why spend an extra three weeks building subwoofers, when I could work a few more hours AT MY JOB and just buy a bigger amplifier?
- Bandpass subs are MUCH easier to build, smaller, and they have distortion killing mechanisms which are comparable to a tapped horn.
- I tried half a dozen different dual-reflex simulations, and kept coming back to single reflex. Theoretically dual-reflex will offer greater bandwidth, but the size of the ports just gets out of control. It all comes back to what your time is worth. Would you rather spend three times as long building a box, or just spend a few extra bucks on a bigger amp? The only way I could make a dual reflex perform better than a single reflex was by using extremely long ports, and it got to the point where the cost of the PVC pipe and elbows would be more than the subwoofer!
- Once I fixed the buzzing end caps, the bandpass easily sounds cleaner than the TH. Of course it's only fair to make the same evaluations about the TH enclosure, which I intend to do. |
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| gedlee |
Box construction is a very important aspect in any design. So many people just don't do the structure right. I make my boxes so that all the sides are nearly equal in size and nearly square - this minimizes the surface area for a given volume. Then internal bracing in the right places and I "usually" don't have a problem. Where I have had endless problems is with the plate amps - most of them are built like toys - even the "top-line" models and tend to vibrate like crazy. I usually end up hot melt gluing everything in sight right off the bat just to avoid the problems down the road.
"Corner loading" is a completely misused concept as it can only exist in a room of infinite volume - all opposing walls are at infinity. In a finite sized room "corner loading" becomes "modal loading" and then we are back to multiple subs as the only real solution. |
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| Patrick Bateman |
The sobering conclusion I came to after working on this project was that a tapped horn is pretty darn cool IF maximum SPL from a given enclosure size is your number one goal.
I can really see why these are a fantastic option for prosound, because an extra one or two DB per cabinet could be the difference between lugging around six subwoofers for a show instead of six. A tapped horn is also incredibily attractive if you're using a woofer with loads of excursion and a high power voice coil. The distortion-masking mechanisms in a TH would make a TH sound audibly superior to a vented box at high power. For instance, the MTX and Eminence woofers that Danley uses are damn near ideal.
But for the home?
Three or four small subs will sound more natural. My house, like a lot of new construction, is hyooooge. Yet I have no idea where I'd hide three or four tapped horns. Even if I figured out where to hide them, I'd have to re-construct the listening room to deal with that much bass I think. I'm mystified when I see people building eight cubic foot tapped horns, when three or four subs would give you comparable SPL, sound better, and they're cheaper (if you use inexpensive woofers.)
At this point I'm running two subs, with one more to finish, and I might go to four.
When I turn on the second sub, my ability to "localize" the subs is diminished greatly, which is one of the greatest benefits of using multiple subs.
In my experience, the biggest complaint that people have about their subs is that they're too easy to localize.
The use of multiple subs addresses that nicely. |
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| Chris8sirhC |
| Can you post some spl graphs and distortion measurements of the two? In my experience, after reading all the stuff gedlee has said, Ive had 3 different subs in the room at the same time Dayton DVC, Dayton Ref, and Lab 12, and my single tapped horn completely blew them away sq wise. It wasn't even close, yet I havent hooked the 2 tapped horns up at the same time. |
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| Patrick Bateman |
I'm dying to do that, but my measurement rig is in a box at the moment. I can do impedance measurements, but not SPL measurements at the moment.
As soon as I can, I'll take a crack at it.
I'm not trashing the TH by any means - it's a neat design. I'm just coming around to the belief that a bandpass has comparable distortion killing mechanisms, and is easier to build. Without a doubt, the biggest advantage to a TH is that big fat distortion-killing notch that lies just above the passband. That could explain why your TH sounds so much better than your prior subs. Based on listening to them back-to-back, at the same power, the bandpass is noticeably more efficient (thought it *doesn't* play as low.)
If you have the patience and the room to build three or four tapped horns, by all means, go for it. If you don't, I believe three or four bandpass subs will trump a single tapped horn. |
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| Chris8sirhC |
| What was so hard about building your tapped horn? Mine didn't require any mitering and almost all of the angles were at 90 degrees. The one angle that wasnt at 90 was within 5 degrees or so of 90 degrees. The most time consuming part was drawing out the design on both sides of the side pannels to make it easier to line up the screws etc when assembling it. |
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| Patrick Bateman |
I'm a big believer in using multiple subs, so the goals of my tapped horn were:
#1 - smallest size humanly possible
#2 - since i'm using a bunch, total spl weren't big requirements
#3 - all of the tapped horns on the big thread require a fair amount of wood working, so I *tried* to design one that didn't
The end result is this thread. Without a doubt, the achilles heel of this design is that it's tall and narrow, which makes it exceptionally difficult to work with. For example, I had to saw the enclosure into quarters just so that I could seal the internal partition, then re-assemble the whole thing.
Again, I'm not trashing the tapped horn, just saying it's not ideal for a home sub IF you agree that multiple subs is de rigeur. |
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| littlemike |
Were it only based upon what I agreed.....
In my case, the architectural review committee has clearly indicated that there are to be a minimum of speakers in the room, and that they are to be as small as possible.
I have approval for 6 (and only 6) enclosures - FR, C, FL, RR, RL, S - and even this is pushing it. Due to the layout of the room, I have limited floor space to put them in. Turns out that in my case - your Achilles' heel is my godsend. A slim tower that makes bass is a much easier enclosure to integrate into my room.
Add to that my desire to experiment and play, throw in my woodworking abilities, and a tapped horn is definitely a viable alternative for me. |
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| electroaudio |
| quote: | Originally posted by Patrick Bateman
Based on listening to them back-to-back, at the same power, the bandpass is noticeably more efficient |
Dont judge efficiency based on listenings.
The ear has a lot more complicated way to caculate loudness than a simple spl meter. Time and frequencycontent is very important to the ear.
http://www.tcelectronic.com/media/s..._loudness_m.pdf |
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| Patrick Bateman |
Oh I agree completely. The fact that the tapped horn is playing noticeably deeper AND we're less sensitive to deep bass might imply the tapped horn is in fact louder.
But the bottom line is that the bandpass is half the size, easier to build, and easier to hide.
I'd love to see someone try a tapped horn with a five inch or a six inch driver. You can get a STUPID amount of low bass out of a tapped horn. Even the eight inch woofer I used was overkill to some degree.
If I could come up with a tapped horn that was one half the size, I'd be all over it. The one in this thread is four cubic feet, and that's quite a lot to hide when you need three or four. |
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| littlemike |
| quote: | Originally posted by Patrick Bateman
Oh I agree completely. The fact that the tapped horn is playing noticeably deeper AND we're less sensitive to deep bass might imply the tapped horn is in fact louder.
But the bottom line is that the bandpass is half the size, easier to build, and easier to hide.
I'd love to see someone try a tapped horn with a five inch or a six inch driver. You can get a STUPID amount of low bass out of a tapped horn. Even the eight inch woofer I used was overkill to some degree.
If I could come up with a tapped horn that was one half the size, I'd be all over it. The one in this thread is four cubic feet, and that's quite a lot to hide when you need three or four. |
I've been measuring and simulating some smaller woofers too. I have come up with several ideas that use inexpensive 6.5 inch drivers. Depending on the driver, you can come up with a tapped horn cabinet that is less than one cubic feet in volume and will play to 45 Hz with authority. As with most of the small drivers, they are limited in the amount of power they can take due to excursion limits.
The Tang Band 6.5" Neo sub driver is usable in a tapped horn as well, and has a lot of excursion. Unfortunately, it is not exactly cheap. |
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| Chris8sirhC |
| There was one exactly like you described in the col. tapped horn thread. I'm pretty sure it uses a 6'' tang band. |
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| littlemike |
IIRC Volvotreter (sp?) has done some work with them, and has posted several designs and favorable comments on his website.
The 6.5 I am playing with is the Dayton PA165 driver, which is very surprising in a TH - flat from 50 to 160 Hz, in about a cubic foot or so. In other words - tough to even fit the driver into the box once it is folded up.
Once I come up with a folding pattern to build one, I'll knock together a test enclosure, though at the rate my fun projects are progressing don't hold your breath waiting. |
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| gedlee |
I'm not even sure that I know what a "tapped horn" is but here is what I do know:
I've studied LF sound sources my whole life and there are no free lunches. Nothing has ever turned out to be an effective improvement in LF design except the Acoustic Lever and its just plain impractical.
Horns at LF are a joke. There is no such thing as a LF horn, unless its the size of a house. Smaller than that and its just a port and ports have been studied to death; series, multiple, transmission lines, its all a bunch of hand waving because when the wavelengths are ten feet long details simply don't matter.
A horn - at best - has an impedance transformation of the square root of the inlet and outlet areas. A lever goes as the square of these areas. Thus for a 2:1 output to input area ratio the lever is twice as effective as a horn. So much for horns.
I'm sorry, but I'll stick to my belief that subs are simple sources and closed boxs work great. Or if you want to get fancy, use a bandpass to lower the HF distortion and increase the efficiency (a little), but anything beyond that is simple "blowing in the wind". |
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| HK26147 |
gedlee
After your post: I have been reading the material on your web site.
RE No LF horns: For what frequency ranges do you consider horns as viable?
I found your use of open cell foam in upper frequency horns quite interesting, and wondered about the lowest usable frequency.
Also enlightening was the response letter on the recent Horn Theory articles
Thanks |
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| gedlee |
I recently did something that I should have done a long time ago. I used the OS contour in Websters Equation in order to determine the accuracy of the later. The OS in my approach is exact, but Webster is never exact - but how bad is it? Turns out its REALLY bad. The traditional idea that the rate of change of the area has to be small for Webster to be accurate is optimistic. It turns out that the rate of change has to be small compared to a wavelength!! This means that ALL predictions of Websters Equation are completely wrong at LFs.
I return to what I said - basicly all horns behave as simple ports at LFs. Ports are not that effective at increasing LF sound as they really can have gain or amplify. The Lever can and does actually amplify. But short of using a lever one may as well just use a single port or no port as nothing else does much good.
How low does a horn work as a horn? Based on what I am seeing in my work, about twice cutoff. Below that the air mass is simply a lump of moving air that has no notion what its boundaries look like.
It also turns out that the parameter theta / a , where "a" is the throat radius, plays a virtually identical role to "m" for an exponential horn - it sets the ficticious cutoff frequency. The OS has a large peak at cutoff while the exponential go to zero. Both solutions are imaginary below cutoff, which is erroneous. |
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| Patrick Bateman |
| The tapped horn is certainly efficient, but it's not because it's a horn. It's efficient because Danley has come up with a clever method to delay the rear wave so that it's mostly in phase with the front. But it's still not a horn - it's closer to a transmission line really. I agree that the front and rear paths are operating as glorified ports, not as true horns. |
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| gedlee |
So how does it differ from a transmission line since these have not ever been shown to be all that effective.
Unless the delay if frequency dependent, it will comb filter, gaining and cutting the output periodically. Over the lowest narrow band where it is gaining, its virtually identical to a dual bandpass design, which can achieve some impressive efficiencies, but only over some pretty narrow bandwidths. If you stager these plus and minuses - so that they interleave - then you have the Bose wave radio or the 1/3 - 2/3 tuning of the prior art.
Really in LF sources its pretty much all been done, but people keep making small changes that have no real effect but then they claim a "revolution". I'm not saying that the TH is like this, I really don't know, but I would be surprised if it is anything more than a new way of doing the same old stuff. |
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| Chris8sirhC |
| The only tapped horn you have built has been built of sonotube and is very lightweight, correct? |
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| Patrick Bateman |
It's quite similar to the Bose Wave cannon. I'd say the most dramatic improvement is the ability to use computer software to model the location of the mouth in two dimensions, and factor in the delay also.
When you look at the simulations, the location of the ports makes quite a dramatic difference in the response.
All of the bandpass programs I've seen until 2006 or so didn't include these factors. Martin King's Mathcad models from quarter-wave.com were the first. Ironically, he doesn't even claim to model bandpass enclosures, but you can model them using his "front loaded horn" simulation.
McBeans horn response is a lot easier to use, the wizards are just genius. |
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| Patrick Bateman |
| quote: | Originally posted by Chris8sirhC
The only tapped horn you have built has been built of sonotube and is very lightweight, correct? |
Yes, whenever possible I use sonotube for subs. It offers a dramatically higher strength to weight ratio compared to conventional construction. I also nest the tubes, as Geddes recommended on the Basslist many years ago. |
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| gedlee |
| But you have to be careful with the ends :devilr: :) |
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| Patrick Bateman |
| quote: | Originally posted by gedlee
I'm not even sure that I know what a "tapped horn" is but here is what I do know:
I've studied LF sound sources my whole life and there are no free lunches. Nothing has ever turned out to be an effective improvement in LF design except the Acoustic Lever and its just plain impractical.
Horns at LF are a joke. There is no such thing as a LF horn, unless its the size of a house. Smaller than that and its just a port and ports have been studied to death; series, multiple, transmission lines, its all a bunch of hand waving because when th |
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