Transmission line problematics

Posted by Duke (D) on September 26, 2002 at 03:36:51

In Reply to: Re: Best bass posted by rick57 on September 26, 2002 at 01:41:06:

Thanks for the clarification on your intended use of transmission lines, Richard.

I still wouldn't suggest TL's for the subs. In my experience, the odds are that a TL won't deliver the bottom end performance expected. This is because, to the best of my knowledge, TL's don't follow the classic design theories. There have been a few new theories put forth recently (including a particularly interesting one by Jon Risch), but I have no experience building with the new theories. I have no doubt that there are manufacturers who know how to mathmatically model a TL, but I don't think that information has been made available to the general public.

I once built a pair of 16-foot transmission lines, following the conventional wisdom of the day regarding line cross-sectional area. Despite quite a bit of playing around with stuffing density, I never got any serious deep bass out of the line.

Over the years I did quite a bit of experimenting, and finally got good results with an intuitive rather than mathematical design that in retrospect probably worked by sheer chance. I used multiple drivers in an "offset" configuration (borrowing that term from the 6th edition of the Loudspeaker Design Cookcook), with a line geometry somewhat reminiscent of the "chambered" line.

If you use a large vented cabinet and tune it very low, you will get a very gradual rolloff with correspondingly very good transient behavior. A large driver x-max is called for to keep the woofer from bottoming out. You might try modelling the BluePrint 18" woofer in a 10 or 12 cubic foot box, tuned to 18 Hz or so, with a 4th order low pass filter at 40 Hz (it would have to be an active filter). System efficiency will be in the mid-80's, but you might not even need any equalization.

Best of luck!

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Follow Ups Full Thread

Topic - Best bass - rick57 22:56:43 09/25/02 (17)

Re: Best bass - DIY world 20:52:21 09/26/02 (1)

Re: Best bass - rick57 21:53:37 09/30/02 (0)

Re: Best bass - seasterl 05:05:09 09/26/02 (5)

i'm a music enthusiast *&* audiophile & i got it *all*... - doug s. 11:30:58 09/27/02 (0)

Re: Best bass - Q-Bert 18:24:16 09/26/02 (3)

Re: Best bass - seasterl 18:03:34 09/30/02 (1)

Re: Best bass - doug s. 05:53:54 10/1/02 (0)

Re: Best bass - Q-Bert 18:30:19 09/26/02 (0)

Re: Best bass - jb 04:15:36 09/26/02 (0)

Re: Best bass - Duke 00:12:52 09/26/02 (4)

Re: Best bass - rick57 01:41:06 09/26/02 (3)

Transmission line problematics - Duke 09/26/0203:36:51 09/26/02 (2)

10hz from a transmission line, - GTF 18:01:45 09/26/02 (1)

Re: 10hz from a transmission line, - rick57 21:59:06 09/30/02 (0)

Re: Best bass - Rob Thomas 23:53:49 09/25/02 (0)

Re: Best bass - Scott Elder 23:52:50 09/25/02 (1)

Re: Best bass - rick57 22:02:28 09/30/02 (0)

Follow Ups

Transmission line problematics - Duke 09/26/0203:36:51 09/26/02 (2)

10hz from a transmission line, - GTF 18:01:45 09/26/02 (1)

Re: 10hz from a transmission line, - rick57 21:59:06 09/30/02 (0)

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