Mass Loaded TL - Getting started?

[Dave Jones]

Last night I played around with Martin King's software, trying to get started on a mass loaded TL design. Specifically, I was looking at the ScanSpeak 5.5" Revelator 15w_8530k01, which has a Qts of .35, Vas of 28 liters, and F3 of 30Hz.

Well, I didn't get anywhere. Every combination I tried had a huge boom-box peak. I never got close enough to a decent design to start tweaking.

Is there a paper on the net about how to get started? Or maybe someone could offer some advice?

[GM]

I've posted how-tos several times on this and other forums, done everything but publish a manual, I think. TLs, ML-TLs don't defy T/S doctrines, so the easy way to get started is to model it in a box program to get the Vb/Fb and vent specs for a starting point. Then it's just a matter of picking a height and the cross sectional area is whatever it is, just keep it > ~1.5*Sd. Put the vent near/at the bottom and slide the driver down the pipe till the third harmonic is suppressed.

I just did a T/S golden ratio max flat, ML-TL max flat, and ML-TL extended to 28Hz, and peaky they ain't. With the abysmal efficiency though, it takes two to make even a marginally acceptable speaker IMO. With it only good to 1kHz, a FR driver, or at least a very wide BW one, appears to be required.

GM

[Dave Jones]

Originally posted by GM
I've posted how-tos several times on this and other forums, done everything but publish a manual, I think. TLs, ML-TLs don't defy T/S doctrines, so the easy way to get started is to model it in a box program to get the Vb/Fb and vent specs for a starting point. Then it's just a matter of picking a height and the cross sectional area is whatever it is, just keep it > ~1.5*Sd. Put the vent near/at the bottom and slide the driver down the pipe till the third harmonic is suppressed.

I just did a T/S golden ratio max flat, ML-TL max flat, and ML-TL extended to 28Hz, and peaky they ain't. With the abysmal efficiency though, it takes two to make even a marginally acceptable speaker IMO. With it only good to 1kHz, a FR driver, or at least a very wide BW one, appears to be required.

GM

Thanks, GM. I'll search for articles by you that contain "mass loaded." I don't quite grok the second paragraph. When you say "it takes two," are you referring to the ScanSpeak driver I was playing with? And a FR (full range) driver is required... for what?

[azira]

Check Bob Brines website. He has a link that says "Design a TL" which has some good starting points. I tried it his values on one and ended up keeping some of the numbers he recommended. My results weren't too shabby (look down for MLTL, Suggestions topic). I'm in the process of building it to see how it will come out.
--
Danny

[joensd]

Hi Dave,
I just put a few links here.

regards
Jens