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Idea Brewing, 15" TL Design!

dc270

dc270

Now Off the Reservation
I am toying with an idea of building a 15" transmission line design, as pictured beow. I found a website where you load your driver parameters and tuning to get a cut list & design pics. I want to modify it a bit so I can adapt a 511 horn on top above the woofer.

http://dbdynamixaudio.com/dual-fold-on-axis-transmission-line-enclosure-calculator/

The driver would be the TD15M from Acoustic Elegance. I am not sure if there would be any gain of a TL over conventional BR type. One thing for sure, I did some measurement of the TD15M this weekend and the ohm curve is amazingly flat out past 2khz! Also not sure if there have been any large TL build like this here. I do like the sound of a well made TL- but also know of their temerment to stuffing properly, etc.

Thoughts gentlemen?

Thanks
DC
 

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Be careful, TLs are tricky and the design seems to be rather empirical. Some of the best bass I've heard was from TLs (Fried Model H) but also some of the worst (big IMFs).

Just my opinions and observations.
 
Tom Brennan said:
Be careful, TLs are tricky and the design seems to be rather empirical. Some of the best bass I've heard was from TLs (Fried Model H) but also some of the worst (big IMFs).

Just my opinions and observations.
Click to expand...

That is exactly why I am posting the question here Tom- see what experience has taught the group here on a large TL designs- could be I would be better of with tradional BR.......or dare I step out on the cutting edge?
Thanks for the reply
DC
 
Tom Brennan said:
Be careful, TLs are tricky and the design seems to be rather empirical. Some of the best bass I've heard was from TLs (Fried Model H) but also some of the worst (big IMFs).

Just my opinions and observations.
Click to expand...
Really! Bad bass from the IMF's? Interesting. I gather you mean sluggish?
 
The file I found is very similar to the ones suggested here, just easier to understand & input information, the results are almost identical.....
DC
 
sealy said:
I gather you mean sluggish?
Click to expand...

Sluggish is a good description. Wooly, thick; a little boomy though boomy overstates it. Keep in mind my opinions are based on auditions from over 30 years though my taste in bass reproduction hasn't changed.
 
Also- one other pitfall, with a wide-bandwidth speaker in a TL:

When the speaker is only reproducing bass (such as in most of the KEF B139-based ones), there's very little chance of midrange coloration in the overall sound, due to midrange frequencies being conducted through the TL, and out the vent. However, with a driver that's flat up to several KHz, you can have significant transmission of upper frequencies, through the line. With the much larger vent opening size (and the relatively "straight line" path) compared to other enclosure types, this can be more of an issue, than with vented or sealed "normal" enclosures.

You will really have to make sure your enclosure is properly damped in the upper frequencies...

BTW: I can understand "sluggish" being an adjective applied to the sound of TL enclosures. The sound DOES have a pretty long path length through the line- this constitutes sometimes significant time delay, which can "smear" transient impacts. The longer the line, the more the delay... the more likely it is to be audible. Same applies to rear-loaded horns... it just takes time for the sound to get out of the opening...

Regards,
Gordon.
 
I recently built a pair of TL enclosures for a single pair of Dynaudio 6.5" drivers, and even for those ended up being pretty large when tuned to 40 Hz. I imagine a 15" TL enclosure would be really, really big. And the cabinets require many, many pieces (mine were 3 folds) I can see why manufacturers aren't crazy about selling them.

It seems the "rules" for TL designs are all over the place.

The tuning i.e. stuffing at various points along the line, really does make a difference, and can take a while to nail down.

Ultimately I had to abandon the project because it was apparent that it was going to take time to get right, and I have no workshop/mancave to do a lot of experimenting, just my living room (which is of course shared with my wife).

That said, I think it's worth pursuing. AK member Robie has a pair of Rega TL speakers with a tiny 5" woofer that produce amazing bass, and overall just a very fine speaker. Also, my local speaker-builder, Van L speakerworks, has a new TL design that I've heard and was very impressed. And consider DCM Time Windows, IMF, Frieds, etc. - correctly executed TLs are excellent.
 
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kirk57 said:
Also, my local speaker-builder, Van L speakerworks, has a new TL design that I've heard and was very impressed.
Click to expand...

Yes, I was over there the other day and heard the new speaker, the Silhouette, and I was mightily impressed. Hard to believe that the depth, quality and quantity of bass was coming from a 6.5" driver. Interesting as I was unaware it was a TL until I later looked at the Van L website. Other aspects of the speaker were just as impressive--- depth, clarity, soundstage and all that. A VERY good speaker.
 
Dc270 another Yahoo group about t-lines. These designs based on the formulas for flue pipes. Richard the group founder also set the world record for loudest sound with one of his steam whistle designs. He is a former physics teacher.
Properly designed and tested t-lines do flatten peaks out.
.
http://tech.groups.yahoo.com/group/tl_loudspeakers/?yguid=137959091
There is more than one way to design them.
I was never fond of the B139 driver. Most of those old Kef drivers had only a 3mm xmas and heavy cones. They would easily bottom out at high spl
One of the reasons Fried abandoned them and used oem drivers for his intended use.
 
Hi DC. I will be recieving my TDF15X drivers this week. I was not part of the group buy. This was a recone job. Anyway, with you built that sized cab as just a vented cab, you could get down to 30hz I would think. A friend has the 15Ms in that size vented cab and there is no need for subs. VERY STRONG bass. A real chest thumper.

I think of using a TL when you are using a small driver and need to augment the bass.
 
Van L was using a 5" dual voice coil version of the Gefco composite cones in the original Quartet.
Similiar to the Fried 6" and 10" Gefco composite drivers that used the M.A.R.S ambience recovery system he later abandoned. Van L used to be a Fried dealer BTD.
 
I am a member of the Yahoo Super Tuner Group, appreciate the link here- they usually offer good information- thanks again
DC
 
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