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-   -   Opinions ?- Transmission Line over Reflex and Acoustic Suspension ? (http://www.diyaudio.com/forums/multi-way/112508-opinions-transmission-line-over-reflex-acoustic-suspension.html)

NepaEric 24th November 2007 11:06 PM

Oninions ?- Transmission Line over Reflex and Acoustic Suspension ?
 
Hi. I posted a previous inquiry in reference to building a pair of TL speakers in the design of a narrow, tall, column tower design.

I am somewhat inexperienced in TL's other than assisting my brother in duplicating an existing design in a publication by David Weems, " Great Stereo Sound Speaker Manual with Projects." We did this some time ago, around an inexpensive Pioneer 6-1/2" translucent woofer driver, a cheap Motorola piezo radiant tweeter, and a simple crossover.

The sound, from my recollection, was astounding, and unusual for such an inexpensive design and small woofer. The reason we did it was experimental, and they delivered on the promises Weems made about them. Anyway, my brother is still using them in his den.

I also had the opportunity to hear a pair of Vandersteens, when invited to a friend's boss' house for a party several years ago, and recall many people (myself included) marvel at the warm, depth, clarity and imaging of these amazing speakers.

I had a similiar experience listening to KEF s and Soliloquoys, among others on other occasions, and really felt they had a beautiful sound by comparison to other quality speakers I've heard over many years, and cannot describe the apparent difference. For this reason I have taken a serious interest in unusual designs such as Voigt pipes, tapered lines, labyrinths, folded horns, etc.

Would any or most of you agree that they are sonically superior by design ? Does anyone have different views regarding TL's ?

Most of the material I have been reading regarding TL theory suggests these designs are superior and capable of producing bass down to a woofer's given free-air frequency, and do not impose limitations on the woofer that inhibit clean, natural, uncolored bass, particularly in the upper and middle-bass frequencies. Advocates of lines all seem to unanimously agree that they beat all other designs on all counts. (Efficiency, lack of coloration, depth, etc.) Often they condemn acoustic suspension designs for pressure buildup in one side of the cone, and vented bass reflex systems for "ringing", and port noise, etc.

Just interested to see what some of you out there, think, in your honest and professional experience and opinions.

I'm wondering if it is worth all of the effort to build such a large enclosure, when many cite I could obtain the same reults in a smaller, less expensive, less time (and space) consuming box.

I truly appreciate any of your opinions, value your DIY experience, and your willingness to share your knowledge.

Thankyou. Warm Regards, Eric

RAndyB 25th November 2007 10:36 AM

I have built Mass Loaded Transmission Lines and Bass Reflex cabinets for the same driver. Bass does sound more controlled by the MLTL, but there are other considerations. See:

http://www.diyaudio.com/forums/showt...968&highlight=

Regards,
Andy

NepaEric 26th November 2007 12:01 AM

"Eggs" and Transmission Lines
 
Those "Eggs" (speakers) you discussed in the thread seem very interesting.

Reminds me of a design I saw once, where the guy called his speakers the "centipede." It was made up of a group of series/parallel, full-range, Tang Band drivers, consisting of a several round, egg-shaped "spheres," mounted on an S-curve bend wrought iron rail. These were a left and right pair.- I believe twenty-some, total, in all.

Do you have an opinion regarding TL's over vented and/or sealed enclosures?

Do you feel they offer better sound?

Do you share the common belief, as many others have indicated that, "it is a waste of time to build such large cabinets, when you can obtain good results from a smaller, less complex, easier to build enclosure which occupies less space?"

planet10 26th November 2007 04:49 AM

There is a large spread of designs that can be called TLs. Some drivers are suited, some aren't.

For a suitable driver a TL is a very nice box.

dave

GDJ 26th November 2007 10:14 PM

Re: "Eggs" and Transmission Lines
 
Quote:

Originally posted by NepaEric

Do you share the common belief, as many others have indicated that, "it is a waste of time to build such large cabinets, when you can obtain good results from a smaller, less complex, easier to build enclosure which occupies less space?"

I certainly don't. I've built my own 1/4 wave Transmission Line speakers and they are VERY worth the effort. Deep DEEP bass is quite possible with a small-ish driver (mine uses a 8" woofer).

Do it! You won't regret it!

NepaEric 27th November 2007 03:00 AM

Dayton Drivers on thier way.
 
I am going to build them. I have an excellent design from a friend who modeled them with the MathCad program. They seem promising, based on the graphs, which show a very good, flat response curve. Thanks, Eric

Ron E 28th November 2007 02:26 AM

Quote:

Those "Eggs" (speakers) you discussed in the thread seem very interesting.
Quote:

Oninions ?- Transmission Line over Reflex and Acoustic Suspension ?
Eggs and onions? How about some cheese and hash browns?
Speakers for breakfast? Hope you brought some coffee.:D

Quote:

Most of the material I have been reading regarding TL theory suggests these designs are superior and capable of producing bass down to a woofer's given free-air frequency, and do not impose limitations on the woofer that inhibit clean, natural, uncolored bass, particularly in the upper and middle-bass frequencies. Advocates of lines all seem to unanimously agree that they beat all other designs on all counts. (Efficiency, lack of coloration, depth, etc.) Often they condemn acoustic suspension designs for pressure buildup in one side of the cone, and vented bass reflex systems for "ringing", and port noise, etc.
If I were you I would read some recent stuff about TL's. Much of the hype that has been perpetuated for 40-odd years about these enclosures has been debunked. They are revealed to behave as damped 4th order systems of the nature of reflex boxes, but with a different (more complicated) resonant mechanism. They generally are much larger than an equivalent reflex. They ring or resonate at multiple frequencies just like Bass reflex. The whole concept of acoustic suspension being a "pressure box" (in a negative way) is flawed. All enclosures radiate sound in proportion to the amount they pressurize the air inside the box.

Good things about TL's, the cabinet construction lends itself to automatic bracing - less box talk. They also have the audiophilia nervosa mystique factor that will make your tweekaholic friends envious.

planet10 28th November 2007 08:21 AM

Quote:

Originally posted by Ron E
Much of the hype that has been perpetuated for 40-odd years about these enclosures has been debunked. They are revealed to behave as damped 4th order systems of the nature of reflex boxes, but with a different (more complicated) resonant mechanism.
That is untrue. Because we have a greater understanding on TL-space does not undo how good the best of the breed are/were capable of or make any less valid the positive attributes a TL can bring to the table. It does mean that the success rate of good TLs has gone from probably 10% up to 90%.

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.

dave

Jozua 28th November 2007 09:00 AM

Small Box design for Kef 139
 
Planet10

I interested in building a TL using Kef139. Any recommendations or plan's you can refer me to re making the speaker as compact as possible ?

Thanks

Jozua

GM 28th November 2007 04:05 PM

2 Attachment(s)
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.

Actually, with a max flat impedance alignment you can achieve a nominally zero phase shift in its passband:

GM


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