Tumult + LT Suggestions? (1 Viewer)

[Gary Griffiths]

I would appreciate some suggestions on a Tumult design using a Marchand Electronics BASSIS LT that would improve on my current sub.

Priorities are sound quality, depth and slam. It would be used for both HT and music. Room size is small, 8ftx8ftx13ft, amplifier power is whatever is needed.

Current sub is a 16^3 twin Tempest using a BASSIS and BFD.

 

[Jack Gilvey]

Since the Bassis will allow you get any response you want very easily, I'd just build a box big enough that you don't have to dump too much power into the driver. 3ft^3 will have you below .7 Qtc. I'll bet you'd get better performance than your current setup in a fraction of the size. In that small a room, you can really go for the infrasonically low response without worrying too much about lack of output.

 

[Gary Griffiths]

Hi Jack

Thanks for the reply. Came across a thread mentioning Unibox so I gave it a try. Looks like 56L (2^3ft) should give me a Q of .7, that seems like a really small box, if that's right and I haven't goofed, great! I'm finding that I prefer a higher Q rather than lower Q so is there any other drawback other than power over going for the smaller box?

 

[Jack Gilvey]

I'm finding that I prefer a higher Q rather than lower Q so is there any other drawback other than power over going for the smaller box?

Since the Bassis or LT circuit will allow you to choose your Qtc/Fc, the thing to watch for is the amount of power your chosen box will require. You may not have enough available and, even if you do, it's best to use as little as possible to get to the excursion you need to avoid power compression (not that I tink it'd be a big issue with Tumult). Bigger boxes are more efficient. If you do prefer the higher Q (.7), then I think you'd best stick with that box since I don't think the Bassis or a bare-bones LT can raise Q.

Here's a great Linkwits transform program that illustrates very well the relationship between box size and power requirements for a desired "alignment":

http://www.pvconsultants.com/audio/eq/linktran.htm

As it happens, the Tumult is the default driver, so there's no inputting for you to do except for box size, power, and desired Fc/Qtc. I think the Xmax spec is wrong, though, should be input as one-way...I think.

 

[Gary Griffiths]

Thanks for the info Jack, that LT spread sheet is much easier to use that other versions I've seen. Just need to make my mind up on 1 Tumult or 2!