Any theoretical or sonic advantage to a sealed versus T-line enclosure?? - diyAudio
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Old 23rd October 2005, 10:24 PM   #1
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Question Any theoretical or sonic advantage to a sealed versus T-line enclosure??

Just curious for the hardcore experts here. Besides *size* is there any advantage either sonically or in "theory" that a sealed sysem (infinite baffle) beats a TL in the 100Hz-20Hz range??????

Not looking to start a war either way, just asking for either "scientific" or "subjective" thoughts.......

Thanks!
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Old 24th October 2005, 07:14 AM   #2
Coolin is offline Coolin  Netherlands
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If your really talking infinite baffle this will be better quality wize but you will need more displacement to get down as low as a port assisted TL.

If your talking regular sealed compared to TL then i'm wondering the same thing actually.

With a TL you will always have two outputs (driver and port ) firing into the room. It will always have an overlap frequency wise which you may or may not hear.

Ive had a large TL to listen to a few years ago for about a week and it was amazing ( my hearing has improved much since then though so i cant say i can back it up presently.. )

TL also has the benefit of improving the midrange because the rear waves are "transported away from the driver" so i suspect that this should sound better maybe even with a closed port ? so its really still a sealed system.

Please fill in here guys, we need to know

Coolin
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Old 24th October 2005, 01:26 PM   #3
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For sealed, I mean a system that would, say, have a 12" driver in a large 100-150 liter cabinet versus something comparable in a TL enclosure. All I know about sealed system types is this:

There are two types of sealed enclosure systems: the infinite baffle (IB) system and the air suspension (AS) system. The IB system normally uses a large enclosure where the compliance (or "springiness") of the air within the enclosure is greater than the compliance of the driver suspension. The AS system normally uses a small enclosure where the compliance of the air within the enclosure is less than the compliance of the driver's suspension by a factor of 3 or more.

So then most likely a 12"er in that large a cabinet sealed would most likely be an infinite baffle, no?
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Old 24th October 2005, 02:37 PM   #4
Volenti is offline Volenti  Australia
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According to http://home.comcast.net/~infinitelybaffled/ , you need 4x Vas per driver at a minimum to be considered infinite baffle with 10x Vas being optimal.
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Old 24th October 2005, 03:01 PM   #5
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OK then, forget the infinite baffle sealed system aspect, my bad there.

How about regular sealed versus T-line.

Let's say you were in a 2-way debate with someone on the merits of each technology, and you were representing the sealed system. Would you even have a leg to stand on in any aspect of performance over the T-line? Objective or subjective?

Opinions or thoughts from anyone??????

I personally own 1 design of each as "subs" and want to know what others think for fun.
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Old 24th October 2005, 03:04 PM   #6
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Don't forget the one inbetween: The closed TML

Regards

Charles
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Old 24th October 2005, 06:01 PM   #7
GM is offline GM  United States
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Greets!

The performance goal of a 'classic' TL (i.e. heavily stuffed, or ~aperiodic) is to get a near IB response in a much smaller package, which it does. It also has the potential advantage of lowering the system Q to < the driver's Qts, which an IB can't do enough to be audible. For instance, I've critically damped (Qtc = 0.5) drivers with a Qts as high as 2.45 when the driver was placed at the proper point along the length of the pipe. The trade-off is that it 'sucks the life' out of wide BW drivers, so best IMO to limit this extreme damping to the midbass/LF BW.

Another plus is that it highly damps the Fs impedance peak if properly designed, so its acoustic phase is flatter. If you're willing to accept a higher F3 to get a flatter phase response, then design the pipe based on Fp = Fs/Qts.

When you compare a typical T/S max flat sealed cab to an equivalent Vb TL, it all falls apart though since you will wind up with a higher F3 to get an aneochoic flat response in such a short 'pipe'.

The IB OTOH has theoretically greater gain at the lowest frequencies and requires no stuffing, but unless a wide BW driver is used and/or it has the mechanical displacement and electrical power handling to drive it this low it's a moot point. Last, but not least, a driver wants to 'feel' an equal pressure on both sides of its diaphragm, so this is reason enough IMO for the IB to be the default choice of the two where practical, which for most folks is unfortunately strictly a 'pipe dream'.

GM
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Old 24th October 2005, 08:05 PM   #8
Coolin is offline Coolin  Netherlands
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GM, always using your knowlege for the good

If you forget all the numbers and size issues can you say which SOUNDS better and in which way (detail/dynamics etc.)
Same size driver though.

jjkozlow, whats your opinion based on your two subs ?...
There probably too different to really say?
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Old 24th October 2005, 08:40 PM   #9
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Well, I have this Fried TL sub with twin 10" Kef woofers:

http://www.t-linespeakers.org/classi...H/fried_H.html

And I have this home brew sealed job (2 of them obviously) with a total of 4 Peerless 10" 850146's:

http://img18.imageshack.us/content.p...opic0170do.jpg

Both are "excellent", and I woulda tried to do my home brew as a TL (the monitor on top of it is), but size and the 2 driver look prevailed.

I prefer the midbass slam of the sealed system and the pitch definition of the TL sub as a "general" comment. Not to say there is a lack of pitch definition with the sealed system, quite the contrary, it is great. The TL is about 5-10% "better" in that area to my ears though. Both go down into the low 20's response wise, with the coffin TL flat to 20Hz in my room, but otherwise a wash in extension.

The homebrew is relatively "new" to me, I've had it up and running for about 2 months now. I guess my biggest astonishment is really how good and close it comes to my coffin TL. I thought I would be giving up some performance by going sealed, but, to my amazement the sealed system just about equals it and in midbass, I believe it betters it . Although the Peerless drivers are "newer" by, oh about, 20 years, so I'm sure much of what I'm hearing are the difference between the drivers themselves.

So anyway, I was curious as to what the experts here thought. As a longtime Fried speaker nut, I have been "born and raised" transmission line. I guess the bottom line is there is less difference between the 2 types then what I had previously been "trained" to believe.

Joel
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Old 24th October 2005, 08:52 PM   #10
GM is offline GM  United States
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Greets!

Best I can anyway.

In the <100 Hz BW they should 'sound' identical for a given driver/alignment/room location, but as I noted, once you move up into the driver's non-pistonic BW the IB will sound more 'open'/'dynamic'/'detailed', though it may not be as 'accurate' as the better damped TL. Most folks appear to prefer the former since some of the signal gets lost in the recording process, but some of us prefer the more highly damped presentation of a low Qt driver or compression horn, so the TL usually gets the nod.

At one time I had ~the best of both, a 300+ ft^3 false wall IB loaded with a 'stereo' matched pair of Altec 15" midbass horn drivers which have a measured 20 Hz Fs/0.16 Qts. They now reside in a pair of highly damped 20 ft^3 corner loaded ML-TL cabs tuned to 16 Hz, and frankly they sound as good to me as the IB, but with the bonus of more gain, so as always YMMV.

GM
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