Hi,
I have been thinking about a largeish build with a fane 12-250tc to get proper full range response with a cutoff as low as possible. A kind of back loaded horn/tqwt/mltl thing.
Is anyone up for helping me a bit in the process? I've been looking a bit into martin kings quarter wave material, and reading some threads on here about tqwt and mltl....
My original idea was to build something like this back loaded horn design:
Cyburgs-Viech von Berndt Burghard
One basic design premise of this horn was that it has no backchamber because of the high qts of the transducer. I suppose this would be beneficial with the 12-250tc as well, since it has qts=0.7.
On the other hand I recently read this paper
http://www.coolcat.dk/bjoern/QWforDummies.pdf
I'm leaning towards a straight line. Cab size 100 cm high, 70ish deep, 35-40 cm wide. (maybe try the 15" big brother in it later?)
I have a funny novel folding layout in mind, a sort of "tapped spiral TL"
Here is a very rough sketch to illustrate my idea. Please dont laugh.....
Front baffle on the left, driver in the upper left, line terminus on the bottom to the same direction as the driver.
Opinions?
I have been thinking about a largeish build with a fane 12-250tc to get proper full range response with a cutoff as low as possible. A kind of back loaded horn/tqwt/mltl thing.
Is anyone up for helping me a bit in the process? I've been looking a bit into martin kings quarter wave material, and reading some threads on here about tqwt and mltl....
My original idea was to build something like this back loaded horn design:
Cyburgs-Viech von Berndt Burghard
One basic design premise of this horn was that it has no backchamber because of the high qts of the transducer. I suppose this would be beneficial with the 12-250tc as well, since it has qts=0.7.
On the other hand I recently read this paper
http://www.coolcat.dk/bjoern/QWforDummies.pdf
I'm leaning towards a straight line. Cab size 100 cm high, 70ish deep, 35-40 cm wide. (maybe try the 15" big brother in it later?)
I have a funny novel folding layout in mind, a sort of "tapped spiral TL"
Here is a very rough sketch to illustrate my idea. Please dont laugh.....
Front baffle on the left, driver in the upper left, line terminus on the bottom to the same direction as the driver.Opinions?
Attachments
Last edited:
Yeah, ran a quick sim and a TL is ~450 L net tuned to 29 Hz once stuffed Vs a ~223 L, 38 Hz MLTL I did awhile back and it was the overall winner with the TL only having considerably less group delay down low enough not to be an issue for all but the relative few that are only happy with low Qtc sealed alignments.
GM
GM
By the time the back signal gets to the front of the speaker the CD will be on the next track at the front of the speaker !
I have put a Fane 15-300TC in a W bin and it sounds good.
I have put a Fane 15-300TC in a W bin and it sounds good.
An externally hosted image should be here but it was not working when we last tested it.
refreshing my memory on MJK.....
so I did
1) play around in horn response a bit. very basic inputs, BLH 1 PAR segment ~2,4 m long with 2000 sq cm mouth without back chamber. Results were spiky and ugly with low bass levels. Need to invest much more time and effort to get into HR, model some existing designs..... tedious. May do to that later
2)went to MJK's site and read this paper:
http://www.quarter-wave.com/Horns/BLH_Design_Article.pdf
two interesting conclusions:
A) MJK's design approach starts from enclosure size. I like that, very practical.
B) mouth size of typical BLHs too small for proper horn loading at bass/sub freqs. My assumed mouth size of 2000 sq cm would provide horn loading only down to ~180-200 Hz. Even assuming half space loading, which doubles the effective mouth size it would be ~90-100 Hz which is not low enough.
-> TL theory applies
I signed up for the yahoo group. I want to get hold of those worksheets. Everybody on here seems to use them
All in all I'm beginning to have some doubts regarding the effort and box size, the general feasibility of my approach. I'm looking at a 350 L box to MAYBE eek out a bit of bass from this driver. Altough I have scrap wood I can waste on this, I want to have some confidence in what I'm building. Hopefully I can arrive at a worthwile design utilizing the MJK worksheets.
so I did
1) play around in horn response a bit. very basic inputs, BLH 1 PAR segment ~2,4 m long with 2000 sq cm mouth without back chamber. Results were spiky and ugly with low bass levels. Need to invest much more time and effort to get into HR, model some existing designs..... tedious. May do to that later
2)went to MJK's site and read this paper:
http://www.quarter-wave.com/Horns/BLH_Design_Article.pdf
two interesting conclusions:
A) MJK's design approach starts from enclosure size. I like that, very practical.
B) mouth size of typical BLHs too small for proper horn loading at bass/sub freqs. My assumed mouth size of 2000 sq cm would provide horn loading only down to ~180-200 Hz. Even assuming half space loading, which doubles the effective mouth size it would be ~90-100 Hz which is not low enough.
-> TL theory applies
I signed up for the yahoo group. I want to get hold of those worksheets. Everybody on here seems to use them
All in all I'm beginning to have some doubts regarding the effort and box size, the general feasibility of my approach. I'm looking at a 350 L box to MAYBE eek out a bit of bass from this driver. Altough I have scrap wood I can waste on this, I want to have some confidence in what I'm building. Hopefully I can arrive at a worthwile design utilizing the MJK worksheets.
No, but in fairness nobody claimed it was.
The 12-250TC is a 12in wideband driver with a Qt at the top end of what could reasonably be described as 'middling', a moderate Vas & Fs. By current enclosure size expectations, it wants quite a large box. For example, a Keele max-flat aligned vented cabinet is about 355 litres, with an Fb of roughly 27Hz. My friend Steve is happy with his in 80 litres sealed; depending on what amplifier he's running at the time system Q will be about 1 - 1.2. Suits his room & requirements, but like every other speaker ever built, won't work for everybody. The smallest I'd go would be the MLTL GM indicated above, or this Keele converted into MLTL form factor which should give some extra alignment damping.
As for horns -available HL BW is 18Hz - 134Hz (nearly). You can tune it low, but like any other vented alignment, you need bulk if you want gain.On top of that, if you heavily compromise the horn expansion you'll need to know what you're doing in terms of blending QW action into what BW is impedance matched, or you'll have a fairly rough response. That may or may not be terrible, depending on specifics; the room dominates < c. 300Hz & combined with our falling hearing acuity in the LF & our tendency to 'key off the peaks' we can put up with a rockier LF response than many believe. Worth it? Technically yes, in certain senses (e.g. dynamic range &c). From a practical POV, I doubt many would be willing to accept the large size of the enclosures (pity).
I suspect the smallest practical vented option that would blend gain & some output down to, say, the midbass would probably by a Karlson BP variation. Not to my taste but YMMV.
The 12-250TC is a 12in wideband driver with a Qt at the top end of what could reasonably be described as 'middling', a moderate Vas & Fs. By current enclosure size expectations, it wants quite a large box. For example, a Keele max-flat aligned vented cabinet is about 355 litres, with an Fb of roughly 27Hz. My friend Steve is happy with his in 80 litres sealed; depending on what amplifier he's running at the time system Q will be about 1 - 1.2. Suits his room & requirements, but like every other speaker ever built, won't work for everybody. The smallest I'd go would be the MLTL GM indicated above, or this Keele converted into MLTL form factor which should give some extra alignment damping.
As for horns -available HL BW is 18Hz - 134Hz (nearly). You can tune it low, but like any other vented alignment, you need bulk if you want gain.On top of that, if you heavily compromise the horn expansion you'll need to know what you're doing in terms of blending QW action into what BW is impedance matched, or you'll have a fairly rough response. That may or may not be terrible, depending on specifics; the room dominates < c. 300Hz & combined with our falling hearing acuity in the LF & our tendency to 'key off the peaks' we can put up with a rockier LF response than many believe. Worth it? Technically yes, in certain senses (e.g. dynamic range &c). From a practical POV, I doubt many would be willing to accept the large size of the enclosures (pity).
I suspect the smallest practical vented option that would blend gain & some output down to, say, the midbass would probably by a Karlson BP variation. Not to my taste but YMMV.
yes, not a woofer by modern comparison. Manufacturer's rating 5.25 mm (whatever that's worth....).
Yet people build big horns for 4" fostex drivers with even less xmax and Sd.
I guess it's the same ideal that full range driver enthusiasts (fostex et al.) have had for a long time, trying to get the best single driver performance.
My build is all about having some fun and trying to eek out as "much" bass as possible from this driver. I know there are limits. I haven't decided on the lower cutoff yet, that depends on what the simulations tell me. Once I have an idea of the options and tradeoffs, I can make a decision.
By all means go for it. I would buy a pair if my budget would allow it. My garage system is an ancient pair of EV Wolverine 12" and they just play on and on with a jvc boombox (5 band eq!) driving them. The whizzers are damped with light foam and the surrounds are doped - these have the corrugated paper not a separate cloth annulus, being the budget offering from 50-60 years ago. Alloy frame!
Here's a sub design with bass measurements. But easily changed to full range too.
17 foot pipe sub 12-230 Hz ±5dB
B.
So far i was planning a 350 litre build, be it a "traditional" BLH, a TL, or an MLTL.
Let's see when I have the time to properly sit down and check out those worksheets. I'll probably start by plugging in the TS parameters of the 12-250TC. Hopefully I will get the hang of how to change the enclosure geometry.
Is it true that there is no way to save the inputs / modified versions of the worksheets, due to functional restrictions of MathCad Explorer?
Yes, you'll need a functioning full copy of MathCAD in order to save. So I strongly recommend you have a writing pad & pencil by your keyboard for making notes / quick records. That's what I always did until I got a full copy from Mathsoft.
As a quick starting point, I suggest you use GM's MLTL, which looks like a nice balanced alignment with a little extra broadband gain for some extra 'slam'. Make it a reasonable wide baffle & you don't need to worry about step-loss as you're pushing it down toward the region where room gain starts to take over. I get basically the same alignment, although since I have a similar design approach we were presumably working on the same basis / along the same lines.
As a quick starting point, I suggest you use GM's MLTL, which looks like a nice balanced alignment with a little extra broadband gain for some extra 'slam'. Make it a reasonable wide baffle & you don't need to worry about step-loss as you're pushing it down toward the region where room gain starts to take over. I get basically the same alignment, although since I have a similar design approach we were presumably working on the same basis / along the same lines.
FWIW, I saved my pre MC 2K sims in WORD or Open Office docs and used one of those freeware programs to screen save small sections such as just driver specs, etc..
Nowadays I just use Hornresp
for quickie sims, so here's the files to import/save/view/make copies to modify or just use dims to load into MC:
GM
Nowadays I just use Hornresp
for quickie sims, so here's the files to import/save/view/make copies to modify or just use dims to load into MC:
GM
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.