Any TL experts out there?

[jmiyake]

I have not had any experience with TLs, but I am considering creating a pair of floor-to-ceiling tapered subwoofers (8' ceilings) for my listening room. The room is 13'x20'

I have a pair of 15" JBL 2226gs that I can use. (specs below FYI.)
Perhaps going from 1.25 sd at the base to maybe 1/2 sd at the opening, forming vertical wedge with an open top just shy of the ceiling. Perhaps about 7'6" length.

Seem viable to you?

Any advice or suggestions from you experienced TL experts.
__________________________________________________ ______________
Qts: .31
Qms: 5.0
Qes:.33
f.: 40 Hz
Re: 2.5 ohms (G), 5.0 ohms (H), 10.0 ohms (J)
Vas: 175 1 (6.2 ft 3 )
Sd: 0.088 m2
(137 in 2 )
Xmax: 7.6 mm (0.30 in)
Vd: 689 cm3 (41 ins)
L: 0.92 mH (G), 1.75 mH (H),
Distortion vs. Frequency

[DorinD]

Hi,
I'm not an expert but I built an TL sub like you intend to do. Mine is a strait 2.5 meters long with 2x12' izobaric. Some obs. I can do to your plan are:
- tapered TL or off-set driver are non-sense for a subwoofer. Has a meaning only for a large bandwidth TL.
- in principle a non dumped strait TL is the way to go for a sub. BUT, after a year of audition of my un-dumped TL sub I discover that dumping it makes a better one. If it's active there's not a problem with some lack of sensivity (previously I was forced to go un-dumped because of a passive configuration where I needed maximum eficiency for sub).

Some pics here:

http://www.hi-fi.ro/fhifi/viewtopic....r=asc&start=30

[sYkboy]

A good place to learn about TL's. Even if it isn't geared towards subs.

http://www.quarter-wave.com/

[mashaffer]

Well that simulates pretty nice for a music sub. The following output for 120W would not exceed Xmax until you got below the low 20s.

mike

[jmiyake]

Thanks Mike,
what are you modeling with?
What stuffing is being assumed?
Thanks again!

[jmiyake]

Hi DorinD,

- tapered TL or off-set driver are non-sense for a subwoofer. Has a meaning only for a large bandwidth TL.

I guess this makes sense if what you are trying to do is delay the backwave so it is no longer out of phase with the driver. But why would that be different for a subwoofer than just a woofer in a TL?

- in principle a non dumped strait TL is the way to go for a sub. BUT, after a year of audition of my un-dumped TL sub I discover that dumping it makes a better one. If it's active there's not a problem with some lack of sensivity (previously I was forced to go un-dumped because of a passive configuration where I needed maximum eficiency for sub).

I thought that "damping" is required to effectively lengthen and lower the frequency of the line. A definite requirement for a subwoofer. Also it is my understanding that tapering also has the effect of lengthening and lowering the frequency of the line.

Just trying to understand, thanks,
James

[DorinD]

Hi,
Somewhere I find the next phrase written by a TL guru:
"There is no reason to use a classic TL design. Using the mass-loading technique, with a taper ratio in excess of 4, you can go lower, smoother than a TL. You also maintain the pipe's ability to eat the back wave in the mid range, which gives you that open pure sound that is the reason to use a TL in the first place. An exception is for a bass TL that will be crossed over at or before the first dip. Then, an un-stuffed pipe, as large as you can stand is the way to go."

Anyway,
have you think of using Jensen's Transflex principle for TL sub?

[qi]

Originally posted by DorinD
Hi,
Somewhere I find the next phrase written by a TL guru:
"There is no reason to use a classic TL design. Using the mass-loading technique, with a taper ratio in excess of 4, you can go lower, smoother than a TL. You also maintain the pipe's ability to eat the back wave in the mid range, which gives you that open pure sound that is the reason to use a TL in the first place. An exception is for a bass TL that will be crossed over at or before the first dip. Then, an un-stuffed pipe, as large as you can stand is the way to go."

Anyway,
have you think of using Jensen's Transflex principle for TL sub?

That would be Bob Brines.

Yes, the Transflex is a BIG MUTHA unstuffed pipe.

I would go with Tom Danley's Tower of Power design.

It is an expanding tapered pipe with an undersized mouth making it mass-loaded (MLTQWP).

He is on the leading edge of subwoofer design and theory...

[mashaffer]

It is DOSTLBM a component of the DOSBOX series of freeware DOS programs. I used an evaluation version of CaptureEzePro to capture the print screen of the DOS screen.

I am using no stuffing in the sim since it doesn't do a good job of simulating stuffing. In your application I doubt that you will want any stuffing anyway. You can always play with stuffing when you prototype it.

It seems to me that a tapered pipe makes sense with this driver ( low Q and fairly low Vas) and given that he is trying to get the best response with a fairly short pipe (since he doesn't want to fold it).

Just my [far from expert] observations.

mike