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.
Don't feed them more than about 20 volts during sine sweep testing or you'll let all the magic smoke out.
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/product_info.php?products_id=1386
SLS10: http://www.madisound.com/catalog/product_info.php?products_id=1705
SLS8: http://www.madisound.com/catalog/product_info.php?products_id=1386
SLS10: http://www.madisound.com/catalog/product_info.php?products_id=1705
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.
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.
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
GM
Attachments
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.
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.
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
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
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
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
Jimmy D. said:
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/showthread.php?postid=1565695#post1565695
That's page 1 of the thread.
I'll post pics soon...
aznboi3644 said:
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/attachment.php?s=&postid=1565695&stamp=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
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/showdetl.cfm?Partnumber=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.
#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/showdetl.cfm?Partnumber=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.
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
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
GM said:
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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