AK Design Collaborative - TCB Subwoofer

Zilch

Curve Junkie
Subscriber
Impressed with the bass performance of PE's Dayton DA175-8 aluminum-cone woofer in Indignia, I wonder how good a TCB (Triple Chamber Bandpass) sub might be made with them:

http://audioheritage.org/vbulletin/showthread.php?t=6289

JBL made a half-dozen versions of these before a threatened infringement suit allegedly shut down the design. The Bose patent has since expired, and the concept is reappearing in some JBL (and other manufacturer) products.

Here's the vintage JBL dual-18" "Monster Sub:"

http://audioheritage.org/vbulletin/showthread.php?t=6782

They also made small ones. This is more what I have in mind:

http://www.jblproservice.com/pdf/Control Series/Control SB-5.pdf

I ran some preliminary sims in BB6P with the DA175-8. Here is the quad-woof isobarik "Other-1:"

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And here is the "Push-push" dual-woof "Other-2:"

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The response curves are virtually identical; the advantage to isobarik (Black) is smaller box size. While it also has higher power-handling, it is 3 dB less efficient, according to these sims:

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Try modeling this... it's not absolutely flat, but BOY, does it hammer.

Eminence Sigma 18 in 3 cubic foot front chamber (tuned to 49 Hz), and 7 cubic foot rear chamber (tuned to about 16 Hz, IIRC... some playing might be in order to maximize flatness).

I have four of these... each pair on a Hill DX1500 power amp (about 350w/ch into 8 ohms)... :D :D :D

Regards,
Gordon.
 
Hmmmm I have 4 cast frame 10" CV woofers! Also 4 KLH 10" model 23 woofers! This might be a fine little home for them! Dual Isobarick for those with an excess of woofers-who wuda thunk it- Great ideas for a sub(s) here Zilch, kinda reminds me of some HWK15's I saw at Decware yesterday.
DC
 
Hmmmm I have 4 cast frame 10" CV woofers! Also 4 KLH 10" model 23 woofers! This might be a fine little home for them! Dual Isobarick for those with an excess of woofers-who wuda thunk it- Great ideas for a sub(s) here Zilch, kinda reminds me of some HWK15's I saw at Decware yesterday.
DC
BB6P models them, as you see. Set the configuration and click the "Suggest" button.... ;)
 
I have 2 KEF 139's awaiting a project sub. :banana: I think i am going tall narrow TL design though.
 
Dangit, Zilch. How about a little rest between projects?

Q's for you:
-is this going to be a group design project from the start or are you just looking to tweak on the concept/driver you started with?

-is 39Hz really a subwoofer?

-looks like your passband is an octave and change, what's the gain over that passband? (normalized response)

-what's the porting look like? BB says the port might not fit and I'm too lazy to model it up myself right now.


I have 2 KEF 139's awaiting a project sub. :banana: I think i am going tall narrow TL design though.

You need to contact Martin King who is a member here. I think he's martinjking but not sure. He's got some great software for simulating TL's.

Ray
 
Dangit, Zilch. How about a little rest between projects?
Heh, heh....

Q's for you:
-is this going to be a group design project from the start or are you just looking to tweak on the concept/driver you started with?
Everybody LOVES building subs!

I'm mostly attempting to define some project parameters here: modest output, modest size, modest cost, an adventuresome design.

TCB's an approach virtually no one has built. I know it works, because I have both ends of the JBL spectrum here.

Are there similarly small drivers suitable/better for this application?

-is 39Hz really a subwoofer?
It's a matter of context and perspective. F6 = 31.63 Hz. Most importantly, it can actually deliver down there.

Wiredbecker and I hooked a JBL SUB-5 and a pair of Minimus 7 AV to an Accurian here, and instantly, we had a sub/satellite "System" that worked. The two channels sum acoustically in the TCB box. I think there's lots of AKers for whom a similar result would be quite satisfying.

Will a small DVC design work as well? I dunno; let's have a look at alternatives. :yes:

-looks like your passband is an octave and change, what's the gain over that passband? (normalized response)
I don't know, but I'm willing to learn about gain.

-what's the porting look like? BB says the port might not fit and I'm too lazy to model it up myself right now.
The dual-woofer is a single 3" x 3.837" long in the center, and a single 1.5" x 4.69" in each of the outer chambers. We should probably bump that to 2" and whatever length is required.

The isobarik has 10.67" and 10.88" lengths, respectively, which will require elbows, no biggie....
 
Is this just a subwoofer for general purposes or is this to be specifically tweeked for the indignia collaberative effort? Once my 2235H arrive, I was going to stuff them into the 4647 boxes, plug two ports with Zilch plugs, and with an electronic crossover use them as subs, but this collaberative effort may be a little less brutal.:D

Russellc
 
General-purpose. While it will play lower than Indignias, I'd guess 15" 2235H woofs will have this beat.... ;)
 
General-purpose. While they will play lower than Indignias, I'd guess 15" 2235H woofs will have these beat.... ;)

I suppose they would, and its OK to try in the basement, but all those boxes dont have as much WAF as a nice compact sub or two, and these collaberatives are getting a reputation for kicking ass!:thmbsp:

I've got a couple of other volunteers that could use a good sub:

russellc
 

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I'm mostly attempting to define some project parameters here: modest output, modest size, modest cost, an adventuresome design.

Roger.

TCB's an approach virtually no one has built.

Probably has to do with Bose owning the patent until fairly recently and eating interlopers up with their legal department.

It's a matter of context and perspective. F6 = 31.63 Hz. Most importantly, it can actually deliver down there.

Fair enough.

Will a small DVC design work as well? I dunno; let's have a look at alternatives. :yes:

Right off hand I'd say we should look at the Tang Band small subs that PE has. Some of them are pretty impressive.

I don't know, but I'm willing to learn about gain.

Look at the normalized response on the BB6 graph (NA = Normalized Amplitude). Generally with a bandpass design as you narrow the band you'll get some gain above 0dB due to energy storage. Kind of like putting a woofer in a too-small sealed box. You get the "high Q" hump. Same type thing with a bandpass.

I knew a guy who had a sealed sub in the back seat of his pickup. When he rolled down the window the bass went nuts. I modelled it up for him once and with the window open he turned into a bandpass system where the sealed box was the back chamber and the truck cab was the front. He was running ~12dB of gain at around 40Hz. :yikes:

The dual-woofer is a single 3" x 3.837" long in the center, and a single 1.5" x 4.69" in each of the outer chambers. We should probably bump that to 2" and whatever length is required.

The isobarik has 10.67" and 10.88" lengths, respectively, which will require elbows, no biggie....

Wow, that's quite a port. For that size you could probably go PR but that would blow the budget part of the project. Unless...we did DIY PR's using surrounds and MDF discs. Hmmm.... Might have to do some dorking around.

Ray
 
Right off hand I'd say we should look at the Tang Band small subs that PE has. Some of them are pretty impressive.
What do we look for to use in this alignment -- high Q, low Q, Fs?

The surprising thing for me in the 18" JBLs was that the 2240H drivers they used aren't even subwoofers.

Look at the normalized response on the BB6 graph (NA = Normalized Amplitude). Generally with a bandpass design as you narrow the band you'll get some gain above 0dB due to energy storage. Kind of like putting a woofer in a too-small sealed box. You get the "high Q" hump. Same type thing with a bandpass.

If there's any gain in either design, it's miniscule:

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Might have to do some dorking around.
NOW yer talkin'.... :thmbsp:
 

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Let's tackle this as a subwoofer system not just a single, since more is indisputably better than less. :)
 
Let's tackle this as a subwoofer system not just a single, since more is indisputably better than less. :)
It would appear you've been right about the dubious advantage of isobarik in this example thus far.

It'll only handle 24% more power at the low end when delivering the same SPL, and it takes twice as much to get there.... :yes:
 
Ah, I'm too tired to do much with this but just wanted you to know that I threw the TB W6-1139SI into BB6 to play with. It's a 6.5" sub with 13(!) mm of Xmax and is on sale for $29 right now. Anyway, thought it was a bit funny that in a 2 driver TCB like the JBL's above it had similar performance to the Dayton. The funny part is that the "suggested minimum" vent for the outer chambers is 3" dia x 42" long. How many elbows is that, Z? ;)

Looks like more messing around is in order.

Ray
 
The funny part is that the "suggested minimum" vent for the outer chambers is 3" dia x 42" long. How many elbows is that, Z? ;)
Newman will work out the answer. :yes:

A Calliope, maybe? :tongue:

I'm on the hunt for the T/S parameters of the little woofs they used in Sub5.

Oddly, they're cloth surround.

[S'pose I could measure them, but that's a last resort.... ;) ]
 
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