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Old 28th November 2007, 07:09 PM   #11
Dr_EM is offline Dr_EM  United Kingdom
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I have a sub I've built as a TL design (by people off of this forum). Using just 2 6" drivers it achieves very deep bass. Measurements haven't been too successful but in room it seems to be merely a db or two down at 20Hz. A big box in relation to the drivers but very effective.
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Old 30th November 2007, 02:47 AM   #12
Ron E is offline Ron E  United States
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Quote:
Originally posted by planet10
Further, an unstuffed TL is a 4th order system, but it can be taken down to a 2nd order system id you want with the addition of juditious stuffing.

If one is willing to live with the size, a TL can bring alot to the table. For one thing a TL is more tolerant (than a BR) of the shifting T/S parameters that happens with the weather or how loud we turn it up.
A damped 4th order can also be achieved with BR. A BR with "port damping in excess" acts as a sealed box. I have seen BR boxes with a 1st order initial rolloff...

When a flat impedance is desired, shorted coil DVC alignments and drivers with damping stapled tightly over the basket are admirably flat...

I am not trying to discourage anyone from building a TL, just giving my alternative point of view. It seems that anyone who listens to anything vaguely resembling or touted as a TL, whether it actually is or isn't (many are simply a variant/hybrid of BR) praises its bass.

The myths that they go down to resonance, that they have a first order roll off, that they are transient perfect, etc..... live on despite evidence to the contrary.

Much of DIY audio seems to be about fashion, or even just "being different" and expressing oneself. Build what you want, but one doesn't always have to delude oneself with decades old audio mythology to appreciate the music.

caveat emptor
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Old 30th November 2007, 03:29 AM   #13
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Quote:
Originally posted by Ron E
touted as a TL, whether it actually is or isn't (many are simply a variant/hybrid of BR)
Conversly, with the fasion for tall, skinny floorstanders there are a lot of boxes that are called BRs that are actually ML-TLs.

dave
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Old 30th November 2007, 09:30 AM   #14
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Right. Quite a few (commercial in particular) designers, when this layout became fashionable a few years ago, found themselves having to go back & re-tune their boxes because they found they were getting more LF extension & gain than they expected due to the QW action.

An MLTL (probably more accurately described as an ML QWR -not a happy choice of name IMO) is not a reflex box. Sorry. A BR assumes no standing waves; an ML QWR deliberately generates and uses standing waves. Generally you can take the transition from one to the other as being the point at which you have to adjust the box tuning to account for the standing wave action.

As for 'decades old mythology' -read MJK and Augsperger on transmission lines lately? Not much mythology in there, unless you've been reading versions of their papers I have yet to run across. The main problem in TL design IMO is that people use the term to mean different things & sometimes complete opposites. I sometimes wish Bailey had never coined the term.
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Old 1st December 2007, 01:39 PM   #15
Ron E is offline Ron E  United States
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Quote:
Originally posted by Scottmoose
As for 'decades old mythology' -read MJK and Augsperger on transmission lines lately? Not much mythology in there...
The name is GL (George) Augspurger.

Enclosure design and simulation is one of my main interests. I wrote a program like Unibox 10 years ago. I once had dreams of marketing it, but people are too interested in freeware nowadays. To me, MJK and GLA's efforts are most interesting in what they disprove, namely much of the 40 year old mythology (and design methods) behind TL's.

Anyway, I am familiar with their research, and that was the "recent stuff" I was suggesting the OP read in my first post.
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Old 1st December 2007, 03:31 PM   #16
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Yes, I know. Apologies for the typo.

Yes, they've done stirling service in ejecting a lot of the nonsense. That said, in fairness to both Olney (Acoustic Labyrinth) and Bailey (God help us... the 'transmission line', despite the fact that the example he presented wasn't really a TL), both their papers are actually very good, within their remit. In reality a lot of the problems appeared post-Bailey, and I get the distinct impression that many people simply hadn't read his article properly, resulting in problems, none of them helped when Bradbury took a bit of a wrong turn (nice idea, but...). George & Martin, finally (thank God), went back to basic physical principles, disproving a lot of the waffle, and also showing that some of the pioneers were in fact pretty good, until their work was diluted or lost.
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