SSA DCON 12 mods...

[Brian Steele 0]

Is it possible to easily mod the SSA DCON 12 to have a higher resonance frequency, say 39Hz? I know some subs appear to allow this by simple dust cap replacement (replace the stock dust cap with a lighter one).

[lithium 358]

why?

[Kanaworm$ 292]

[Brian Steele 0]

why?

A little project I'm working on at the moment, that might produce better results with a long excursion driver with Fs around 39~42 Hz....

[Aaron Clinton 2,372]

What is it you need to raise the Fs for?

[Brian Steele 0]

What is it you need to raise the Fs for?

To make it a better match for a future project I'm considering.

Some background -

1. I've almost finished my POC#2 project - a "small" (4.3 cu.ft. net) 40Hz tapped horn based around a cheap pro audio driver (Fs 39 Hz, Qts=0.31). I haven't put up a page about it yet, but a picture of it under construction can be seen here: http://www.diysubwoofers.org/projects/other/PA310-TH/images/PA310-TH-10.jpg . HornResp predicts efficiency of 93dB@ 40 Hz /1W/1M, over 96dB/1W/1M through the passband, and an upper cutoff above 120 Hz. The design is theoretically displacement-limited to 116dB peak @90W just about 50 Hz in its passband though (and that's assuming that I can use the full 5mm throw of the driver - hardly likely). I can glean a few more dB by going with a slightly larger horn, but if I had access to an inexpensive driver with similar specs and a bit more Xmax...

2. There's a "challenge" on at DIYAUdio at the moment - to build a TH capable of 40 Hz and 125dB peak in its passband, using only one sheet of ply. See http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge.html. I'm just curious to see if it's possible to do it with something smaller than a 15", which will give a bit more leeway wrt box geometry.

Edited August 6, 2010 by Brian Steele

[Impious 1,476]

I can't imagine a dust cap change would be enough of a drop in mass to increase Fs to the range you need for this driver. It appears, on a Dcon, you would need to decrease the mass by about half to get the Fs into the range you need. Which means the most logical option would be to decrease the compliance of the suspension. Would the raise in Q and decrease in Vas as a result still be acceptable to your design goals?

[Brian Steele 0]

I can't imagine a dust cap change would be enough of a drop in mass to increase Fs to the range you need for this driver. It appears, on a Dcon, you would need to decrease the mass by about half to get the Fs into the range you need. Which means the most logical option would be to decrease the compliance of the suspension. Would the raise in Q and decrease in Vas as a result still be acceptable to your design goals?

Oof, sounds like a complete rebuild, rather than a simple adjustment.

A higher Q will require an adjustment in the horn's geometry to compensate. After having run dozens of TH sims in HornResp, it looks like generally a higher Q = lower throat/mouth ratio to achieve a flat passband. A reduction in Vas might reduce overall size, but this and the change in throat/mouth ratio may not necessarily be good things - the end result might be a sim that looks great - until it's time to actually fit the driver into the box .

[Impious 1,476]

Well, I don't know how helpful this may be, but worth a shot.

Fi X 12"

Fs is already almost 36hz, from some quick figuring it looks like mass would only need to drop by ~27g to reach an Fs of ~39hz. Now, I don't know the mass of their dustcaps, but you are starting from a much closer point so that might be something they may be able to help manipulate with the dust cap. Q is higher, but they have a S2 and S4 options, so they may be able to manipulate the coil and gap width/etc to lower the Q to your target. Vas is smaller than the Dcon which from the sounds of things, if you can get the Fs and Q within your target range the smaller Vas will help keep overall size down some. 18mm Xmax will help reach your output goals. And it's still an affordable driver

I would shoot Scott or Nick @ Fi an email or PM on here and see if that's something they could work out for you.

As a last ditch effort, you may try the Audioque HDC. It's twice as expensive, but the Fs and Q are already in your range and it should have enough useable throw for your application. Oh, or a Fi BL.....again, expensive (compared to your goal), but the dual 2 has an Fs and Q that should be within your range, good throw and small Vas.

Pro Audio drivers would be nice for your app, but it's hard to find an affordable driver that has significant throw

[Brian Steele 0]

Well, I don't know how helpful this may be, but worth a shot.

Fi X 12"

Fs is already almost 36hz, from some quick figuring it looks like mass would only need to drop by ~27g to reach an Fs of ~39hz. Now, I don't know the mass of their dustcaps, but you are starting from a much closer point so that might be something they may be able to help manipulate with the dust cap. Q is higher, but they have a S2 and S4 options, so they may be able to manipulate the coil and gap width/etc to lower the Q to your target. Vas is smaller than the Dcon which from the sounds of things, if you can get the Fs and Q within your target range the smaller Vas will help keep overall size down some. 18mm Xmax will help reach your output goals. And it's still an affordable driver

Thanks - that Fi driver does look interesting. I'm working with another driver at the moment, but the Fi's specs suggest 5 or more dB output in the same passband in only a slightly larger TH - nice! I'll pass the info onto the guys on the DIYAudio forum just in case anyone wants to look at it while I'm finishing my current project. It does look VERY promising. Thanks again!

Edited August 7, 2010 by Brian Steele

[Impious 1,476]

Good luck with the project

Now that you've spilled the beans on your project, feel free to post results and progress here on SSA as well if you don't mind and have the time I for one would be interested in seeing what you are able to come up with.