Boston Cabinet Builders - Collaboration

[gmarcus]

Years ago I worked up a very easy and effective design for building transmission line speakers for home stereo. I've always wanted to try this out for a bass speaker cabinet. Unfortunately I don't have a workshop anymore and I was never really a good woodworker. Is there anyone in the Boston area that would like to collaborate on this with me? Shoot me a PM if you are interested.

Thanks

Gregg

[gmarcus]

The design works with speakers that have a relatively high QTs of greater than about .5 or .6 which are generally cheaper. It results in a small cabinet with really tight bass. It is a non resonant design so there should be a much smaller impedance peak than with a ported cabinet. Ported Cabinets have a 24 db/octave roll off, Sealed cabinets have a 12 db/octave roll off and T-lines have a 6 db/octave roll off. We can mess around with the line length to get the desired bass extension and possibly to reinforce some of the low mid frequencies.

I based the design on a microwave filter concept and it seemed to work really well. I built 2 cabinets many years ago. The construction method is actually pretty easy and it works to help brace the cabinet too.

[rpsands]

Have you found any light woofers with Q that high?

[gmarcus]

http://professional.celestion.com/ba...BN15-400X8.pdf

It doesn't have the Xmax of the Kapalites but it should sound good in a T-Line.

You can build T-Lines with low QTs drivers, but the bass roll of is kind of like the driver in free space. I think it actually gets loaded a little bit by the cabinet so it might be a little higher. A QTs of ~.7 would be perfect.

[gmarcus]

These would work for a 2X12
http://www.eminence.com/pdf/basslite-s2012.pdf
http://www.eminence.com/pdf/alpha-12a.pdf

a cheap single 15"
http://www.eminence.com/pdf/beta-15a.pdf

[gmarcus]

I can't find the reference, but you can also add weight to the speaker cone and it will increase the Q at the expense of high frequencies and probably some efficiency. I bet Eminence could make a high Q Kappalite or we could glue some weight around the dust cap.

[billfitzmaurice]

Originally Posted by rpsands

Have you found any light woofers with Q that high?

There are plenty, but few with xmax more than 4mm. That's very limiting.

It results in a small cabinet with really tight bass.

The problem with a TLine is that to be effective to only 50Hz it has to be at least six feet long, and the result can be easily beat with a smaller vented box.

T-lines have a 6 db/octave roll off.

12dB actually, just like a sealed cab.

I bet Eminence could make a high Q Kappalite or we could glue some weight around the dust cap.

Eminence wouldn't do so. The added mass would severely reduce broadband sensitivity and kill the mids entirely.