Designing a sub... software, etc.

[Boris Yeltsin]

reed.hannebaum wrote:

I use the same front L/R speakers for 2 channel listening as I do for HT. I have a DIY passive sealed 15" sub behind each of my Quad 12L Studio Monitors. I use a Paradigm X-30 to crossover between the Quads and the subs.

how did you design the sub? did you use software? could you provide some more info on it? thanks man

take care

Chris

[reed.hannebaum]

I use the term DIY pretty loosely. I actually start with an old dbx SW15 subwoofer. These are sealed down firing subs that I modify. The enclosure is made from 5/8” MDF with a ¾” baffle plate. The interior volume minus the driver cone volume is about 3.1 cu.ft.

What I do is I bypass the built-in crossover, and wire the dual voice coils directly to the speaker terminals. I seal all the interior corners and edges with silicone. I add cross bracing to stiffen the walls, and I line the walls with about 1 ½ lb nylon dampening material. I replace the wood screws used for mounting the driver with T-nuts & 10-32 machine screws, and put sealing caulk around the driver.

I took this route for several reasons. I already had one of these subs from my early audio hobby days, I wanted something near DIY in my system (also, I have just mediocre carpentry skills), plus I wanted to minimize cost and effort.

My next step is to save my pennies and replace the drivers with the Adire Tempest 15D8. These are very good drivers especially design for small/medium size enclosures, and should work well with this box. Miraculously, the existing baffle cut-out and bolt pattern match up with what I now have.

[JCD]

reed.hannebaum wrote:

I use the term DIY pretty loosely. I actually start with an old dbx SW15 subwoofer. These are sealed down firing subs that I modify. The enclosure is made from 5/8” MDF with a ¾” baffle plate. The interior volume minus the driver cone volume is about 3.1 cu.ft.

What I do is I bypass the built-in crossover, and wire the dual voice coils directly to the speaker terminals. I seal all the interior corners and edges with silicone. I add cross bracing to stiffen the walls, and I line the walls with about 1 ½ lb nylon dampening material. I replace the wood screws used for mounting the driver with T-nuts & 10-32 machine screws, and put sealing caulk around the driver.

I took this route for several reasons. I already had one of these subs from my early audio hobby days, I wanted something near DIY in my system (also, I have just mediocre carpentry skills), plus I wanted to minimize cost and effort.

My next step is to save my pennies and replace the drivers with the Adire Tempest 15D8. These are very good drivers especially design for small/medium size enclosures, and should work well with this box. Miraculously, the existing baffle cut-out and bolt pattern match up with what I now have.

Will the driver actually have the right T/S parameters for your box? I would have assumed that you'd have a different internal volume requirement with a new driver.

JCD

[reed.hannebaum]

JCD wrote:

Will the driver actually have the right T/S parameters for your box? I would have assumed that you'd have a different internal volume requirement with a new driver.

JCD

As I am sure you know better that I do, a sealed enclosure is the most forgiving of the classical enclosure styles. The Adire website recommends using the Tempest driver in a 2-5 cu.ft. sealed enclosure. I used the AJ Sealed Subwoofer Designer software (freeware of course), and calculated a Qtc=0.816, which is a little high but still very good, and F3 (-3 db point)=35Hz. From the response curve it appears that the -6 db point is at about 22Hz, which is good for my application.

Another consideration with down firing drivers is cone sag. In one of their technical papers Adire gives the formulas to calculate sag, and recommends that cone sag should be no more than 5% of Xmas. Plugging in the parameters for the Tempest driver I calculate 2.78% cone sag, which should be satisfactory.

[bartolmay]

reed.hannebaum wrote:

As I am sure you know better that I do, a sealed enclosure is the most forgiving of the classical enclosure styles. The Adire website recommends using the Tempest driver in a 2-5 cu.ft. sealed enclosure. I used the AJ Sealed Subwoofer Designer software (freeware of course), and calculated a Qtc=0.816, which is a little high but still very good, and F3 (-3 db point)=35Hz. From the response curve it appears that the -6 db point is at about 22Hz, which is good for my application.

Another consideration with down firing drivers is cone sag. In one of their technical papers Adire gives the formulas to calculate sag, and recommends that cone sag should be no more than 5% of Xmas. Plugging in the parameters for the Tempest driver I calculate 2.78% cone sag, which should be satisfactory.

Did you ever replaced the drivers? If so, which one did you get? And about the crossover, did you direct into both coils or it got replaced.

Thanks

Frank