I Pialigned a Seas Excel 7" for use as a midbass in vehicle, running down to 60 Hz.

It came up with some somewhat odd results which plotted funny in my box program (it gave me a response peak), but maybe I just mistranslated them.

Anyway, I tweaked it slightly from what Pialign gave me, I placed it in a 0.33 cuft tuned to 51 Hz. Gives me flat response to 50 Hz, which is fine in this case because it'll only be operating 60 Hz and up.

Is there any chance you could check this out and tell me if this box design would still sound great for the midbass? This is one of the best midbass drivers in existance, but I've never heard of it being run in such a small enclosure before, and it strikes up a bit of worry. Since you have a ton of experience with these overdamped ported box alignments, I thought maybe you could help me out.

Thanks bud.

Here's the woofer specs:
http://www.madisound.com/seas/e017.pdf

Adam

From the Seas W18EX001 specification sheet, the numbers shown are Vas=37 liters (1.31 cubic feet), Fts=31.0Hz and Qts=0.24. PiAlign values are then Vad=1.31, Frd=31.0 and Qd=4.17 and the recommended enclosure is 0.31 cubic feet and tuned to 48Hz. It is able to calculate a cabinet having actual resonance very close to this - 52Hz - using a 3/4" port that's 3/4" long, so that nice because it can be formed easily by drilling a 3/4" hole in 3/4" baffle material. All-in-all, PiAlign's recommendation is an excellent solution.

A couple of other things are worth mentioning. You might notice that distortion rises substantially at low frequencies. It rises fast below 100Hz, where it is around 1%. By 50Hz, it is over 3% and climbing quickly into the double digits. Distortion is also rising at the other end of the spectrum, and breakup modes are severe at 4kHz. Performance up to 4kHz is quite sufficient and really, so is performance down to 50Hz. For a system of this size, I think it would compare favorably and work very well.

I was planning on crossing it at 1.2 kHz with an Image Dynamics horn, so the breakup modes won't be a problem.

Also, like I mentioned in my particular app, it'll only be operating down to 60 Hz so I think distortion should be fine. This is one of the cleanest midbass drivers around. I think you can do better than it for the low bass, but it's still an impressive unit... Some of the lowest distortion figures around, twin copper shorting rings, magnesium cone, solid copper phase plug...

Pialigning the driver (or at least a similar alignment) really seems to offer the extension I need down to 60 Hz, with big time power handling, no loss in sensitivity... Shoudl be great!! Much better than running the weaker motor version in a sealed box... Bleh.

I was going to recommend this driver to Scott actually, the only thing that stopped me is it's $156 dollar price tag and it's 8 ohm impedance.

Adam

I imagine the distortion figures on the bottom end would be a little lower if it was measured ported perhaps?

Adam

Cabinet volume = 0.31 cubic feet
Port = 3/4" diameter hole drilled through 3/4" thick baffle

Adam