Announcement

**Dirk** · 04-10-2007, 02:35 PM

Re: Crooked subwoofer?

> Hi,

> I am interested in building a subwoofer
> design that I saw a long time ago in Stereo
> Review.

> Basically, it is 32 3" PVC elbows with
> a driver between the 8th and 9th elbow.

> I think this is called a "Transmission
> Line" design. Am I right?

> The URL I've attached is a scan of the 1992
> Stereo Review article.

> The questions are:
> 1. Do you think it will work well?
> 2. What Dayton driver would be most
> appropriate?

It's location between elbows does not matter. Just its location in the line.

One of the most important tuning aspects to a transmission line is the cross-sectional area. In this case, they use a 4" driver tied to a 3" like. Suitable, more or less. Bigger drivers need appropriately sized pipes. And let's not think that a T-line will turn a pigs ear into a silk purse. It's STILL a 4" driver, and you'll only get so much bass, no matter what you do to its backwave.

Personally, if I were to make a horrid abberation of a sub (and I say that in the best possible way), I'd find a driver with a low Vas and a very high Xmax. Normally, these drivers take very big ports that don't fit neatly in the box. Don't bother trying, I say. Mount 'em OUTSIDE the box. For example, the Dayton RS 265HO 10" subwoofer works smashingly well in a .75ft^3 box. And with two 3" ports approximately 66" long. Get to foldin'. :-)

Oh, and the Dayton option, while substantially more expensive, would be a true high-displacement subwoofer capable of all the things you'd expect of a sub. It'd just look like a Blue Man Group prop!

**johnnyrichards** · 04-10-2007, 02:37 PM

Cool name! *PIC*

Provided Link: 4" Shielded Tang Band

Maybe the Tang Band 4" "Subwoofer" that PE sells would work in this application...

**Dirk** · 04-10-2007, 02:40 PM

Re: Crooked subwoofer?

Or, if 3" ports become hard to work with, twin 2.5" PVC ports at 46" each would also provide the same tuning.

**marlboro** · 04-10-2007, 03:22 PM

April Fool's Issue

I used to get this magazine. Lirpa is April spelled backwards.

This was their annual April Fool's issue.

There are some transmission line speakers using spiral piping, but not sub woofers. They knew that even way back in 1992 when I was just a boy at 43 years old.

You've been had, or you're trying to pull our legs.

Marlboro

dB · 04-10-2007, 03:43 PM

Re: April Fool's Issue

> I used to get this magazine. Lirpa is April
> spelled backwards.

> This was their annual April Fool's issue.

> There are some transmission line speakers
> using spiral piping, but not sub woofers.
> They knew that even way back in 1992 when I
> was just a boy at 43 years old.

> You've been had, or you're trying to pull
> our legs.

> Marlboro

Something tells me he knew this already -- trying to Lirpa us.

...and I was 46 that year. Dude we gettin old!

dave

**Dirk** · 04-10-2007, 03:50 PM

Re: That's all fine and good, but...

> Something tells me he knew this already --
> trying to Lirpa us.

> ...and I was 46 that year. Dude we gettin
> old!

> dave

Yeah, I kind of figured something was up once they started dropping names like the "Hirsutic Institute for the whatever" and "Linkwitz Moscovitz".

Anywhoo, do you see any reason why, in theory at least, this wouldn't work? I could see the passband being fairly narrow, but there'd be two re-inforced frequencies, somewhat like a 6th order bandpass. Not that'd I'd try to build such a monstrosity (I can think of better things to do with my limited time).

Oh, and I won't tell you that I was 15 in '92...

**scott_s** · 04-10-2007, 04:20 PM

It's actually been done...

Provided Link: Bose Acoustic Wave Cannon

...believe it or not by Bose, sort of. IIRC theirs uses a 12" woofer and a straight, very big/long tube and is intended for pro applications. Check out the "Acoustic Wave Cannon". There is also a (very long) thread about a DIY version here: <A HREF="http://www.diyaudio.com/forums/showt...?threadid=9501">http://www.diyaudio.com/forums/showt...?threadid=9501</A>
Scott S.

**daylbrinkman** · 04-10-2007, 04:33 PM

Re: That's all fine and good, but...

Obviously, I knew the article was pulling your leg. But, not having a lot of experience, what I wanted to know was, do think something like this would actually work? (Before I go to Home Depot and raid the PVC aisle).

> Yeah, I kind of figured something was up
> once they started dropping names like the
> "Hirsutic Institute for the
> whatever" and "Linkwitz
> Moscovitz".

> Anywhoo, do you see any reason why, in
> theory at least, this wouldn't work? I could
> see the passband being fairly narrow, but
> there'd be two re-inforced frequencies,
> somewhat like a 6th order bandpass. Not
> that'd I'd try to build such a monstrosity
> (I can think of better things to do with my
> limited time).

> Oh, and I won't tell you that I was 15 in
> '92...

**Dirk** · 04-10-2007, 04:52 PM

Re: That's all fine and good, but...

> Obviously, I knew the article was pulling
> your leg. But, not having a lot of
> experience, what I wanted to know was, do
> think something like this would actually
> work? (Before I go to Home Depot and raid
> the PVC aisle).

Kinda sounds like it would. I read a bit of the Bose patent mentioned in the diyaudio post (in Scott's post). Looks like you want a low-Qts driver with gobs of excursion and that the pipe sizing & length all depends on the frequency you're trying to reproduce.

That all rings of "transmission line" to me. They're just treating both the front & back wave.

**dancarroll** · 04-10-2007, 05:23 PM

Wholly Molley is you guys Auld!

I was only 39 then. Or 40, if it was after October. But it wasn't, bein' Lirpa and all.

**marlboro** · 04-10-2007, 05:36 PM

Re: That's all fine and good, but...

You are going to have some issues. How low do you expect them to go? How much total volume do you expect them to have? The won't have vibration problems?

Transmission lines are much different than they were before ML King. TL's really don't help much when you get into the woofer and sub woofer category. I had Pete run the figures form me using Martin King's spreadsheet, and it just wasn't worth it.

You should consider low footprint high volume sonotube systems in a vented design.

Bose operates on the "you can get something for nothing" principle, but no one has found away to violate the laws of physics in regard to low notes, and a sub woofer means hitting the 15-30hz frequencies.

Marlboro

**blair** · 04-10-2007, 05:40 PM

Re: That's all fine and good, but...

"Something for Nothing"!!!!

Have you seen their prices? I hardly call that nothing;)

Blair

**marlboro** · 04-10-2007, 05:41 PM

But do you remember.....

You're only old on this forum if you can rember leafing through the very old 1 inch thick ALLIED RADIO CATALOGUES with an eager look in your eyes.

Marlboro

**dancarroll** · 04-10-2007, 05:47 PM

Honesty requires I say

> You're only old on this forum if you can
> rember leafing through the very old 1 inch
> thick ALLIED RADIO CATALOGUES with an eager
> look in your eyes.

. . . that I am not sure. I remember looking at some such catalogs as a 17 YO college freshman, but whether it was Allied Radio or something else, I don't know. It contained Lafayette electronics and, among other things, Utah speakers.

Dan

Announcement

Crooked subwoofer?

Crooked subwoofer?

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment