Tumult and a sealed enclosure...

ClaudeL · 10-29-2003, 06:32 PM

Hi all!

I have in mind a 2.5 cubic ft sealed box for my Tumult and the QSC PLX2400. BUT, WinISD Pro and BassBox Pro 6 dont give me the same Qtc value. WinISD Pro gives me a Qtc of 0,66 and BassBox Pro 6 gives me a Qtc of 0,6. In both programs, the Qa=100 and Ql=10.

If BBPro6 is right, a 2 cubic ft box would give me a nice Qtc of 0,65 , the box would be smaller and it would be nice. The Xmax around 20 Hz would be safer with that 2400W amp according to BBPro.

Second question... Is 3/4 inch thick plywood is enough for the enclosure? I often see people mentionning that we should use 1.5" of MDF for the enclosure walls, ore double walled 3/4" of MDF. I saw in one post somewhere that 3/4" of baltic birch ply can be enought because that material is more rigid.

Third question... do I need "special" binding post because of that powerfull amp? Gold plated I imagine... But I dont see any power rating when I look at some binding posts. For example: a binding post "A", power rating: suitable for 5 to 10A of current.

ThomasW · 10-29-2003, 07:10 PM

Software programs of course use formula's to make their calculations. There is some latitude in how those formulas are implemented.

I suggest downloading the Adire version of LspCAD or UniBox and modeling with one of those.

With adequate add-on stiffening braces, 3/4" baltic ply is very good for subs

No you don't need special inputs for high power amps.

Rory Buszka · 10-29-2003, 07:30 PM

That said, binding posts will probably carry current better because there is less of a constriction in the conductor size. You should do the binding posts.

ClaudeL · 10-29-2003, 08:16 PM

LspCAD of the Adire Audio site... the problem is that they dont carry the Tumult woofer in the software. Im gonna try Unibox. BassBox Pro 6... this isnt a good software for modeling subwoofer?

"3/4" baltic ply is very good for subs"... but what about the subs using a woofer which can displace 5.1L of air? This woofer is a monster and I must be sure than only 3/4" thick plywood is enough... of course with some braces. At the beginning, I was thinking about 1.5" of MDF but why adding more mass to the enclosure IF only 3/4" thick plywood can do the trick

ThomasW · 10-29-2003, 08:35 PM

I thought someone posted that the Tumult was added to the LspCAD data base.

You'll get somewhat differing results with each program.

I'm pretty familar with the design and construction of monster subs. And if I were building it the material would be no less than 1.5" thick, but yes if you put in ENOUGH bracing it can be built from 3/4"

Input terminals like THESE are adequate to the task

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Brian Bunge · 10-29-2003, 08:51 PM

Also keep in mind that 3/4" cabinet grade plywood, which you buy in 4x8 sheets at most home improvement stores, is not the same thing as 3/4" baltic ply.

ClaudeL · 10-29-2003, 08:57 PM

"And if I were building it the material would be no less than 1.5" thick, but yes if you put in ENOUGH bracing it can be built from 3/4"

Do you talk about MDF there? Because like I said, Ive read a post about a person mentionning this, but he said 1.5" thick of MDF or 3/4" thick of baltic bich ply. He said MDF is more dense, but plywood is more rigid so its why we can use less thick plywood (according to him).

*UPDATE*: Oh.. and anyone know the volume displacement of the Tumult woofer?

ThomasW · 10-29-2003, 09:09 PM

Look this is a matter of making a choice.

A box made with 3/4" baltic ply and proper bracing will do the job.

I tend to leave nothing to chance so I overbuild everything, that's my choice.

If you're going to use MDF then yes it must be at least 1.5" thick and have good bracing.

There are 2 ways to build a box. High Fs = low mass, low density, rigid and stiff = Baltic ply. Low Fs= high mass and dense = thick MDF

ClaudeL · 10-29-2003, 09:18 PM

Thanx a lot!

Im sorry for my attitude :b I may be a bit TOO worried about my next sub, but its because Ive never built any killer sub like this one. I just used the Shiva and the Tempest in the past. So having a woofer which is so powerfull, I was affraid to have a lot of wall vibrations with only 3/4" of MDF. And I never used plywood yet, because I always felt that MDF was cheaper and it was ok for what Ive built. I think that Im gonna go with 3/4" thick plywood, and I'll use MDF for the internal braces.

Thanx again

OH.. and by the way, BassBox Pro6 and Unibox seem to like each other because I have the same Qtc value with a 2.5 cu ft box. Seems like BassBox Pro is a very good and accurate software

Rob Formica · 10-30-2003, 12:08 AM

Quote:

Also keep in mind that 3/4" cabinet grade plywood, which you buy in 4x8 sheets at most home improvement stores, is not the same thing as 3/4" baltic ply.

That's right, the Baltic ply I've seen has been in 5'x5' (approximately) sheets and is significantly heavier than furniture plywood... but your box will still weigh less than 1-1/2 MDF.

George W · 10-30-2003, 05:39 PM

Claude,

You don't want to use mdf for the braces. It will compress along that axis much more easily than plywood will, so if you have extra plywood that is your best bet.

ClaudeL · 10-30-2003, 06:50 PM

Ok... all in plywood or all in MDF

I justly thought about using plywood for the braces, because it sounded weird to me to mix 2 different materials for stiffening the enclosure. So thanx for backing my mind up!

I wonder how really hard is the plywood... I mean... I worked a lot with MDF and this material is so easy to work with, especially when you cut some piece or when you use the router. I never tried anything with plywood. I just learn and learn more everyday thanx for you all and thanx for my dad who is skilled in "wood working" and who is way better than me in that department!