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The WideBody 12th September 2007 02:19 PM

Peavey 1808-8
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i just bought off of ebay a peavey black widow 1808-8 he bmx black widow sub.

i plan on building the enclosure myself.

i am going to use it for the amplification of my 4 string bass through a fender bassman 100 tube amp also just recently purchased on ebay.

i have tried to use winisd and perfect box but just don't have enough knowledge to make the chart make any real world sense to me.

for reference, i've included the specs from the box.

please help!

i wanna box with a depth in the mid teens and as square as it can be or and with the dimensions no less than 28 inches.

also in this enclosure do you recommend that i have a midbass driver?

thank you for your help!


mashaffer 13th September 2007 02:23 AM

Hmmm... specs on yours are a lot different than the 1808 that PE sells but assuming that you have the right information for your driver a sealed box of about 18x30x30 (9cu-ft) should be down about 5dB at 50Hz which it seems shouldn't be too bad for bass but not as deep as I would think that you want. Going larger lessens the rolloff below this point but does not really move the -5dB point. Going below about 6cu-ft starts to raise the -5dB frequency (not a good thing).

A vented box seems to want about 16cu-ft but you could fudge it down to about 11 and still get quite flat down to 40Hz. For example 18x33x33 would get you there with a couple of short 4" diameter ports. Boxplot says 2 1/3" long giving just a tiny (1dB) bump at 80Hz.

Could go fancier too I suppose. I haven't checked but I bet a TL good be very successful but kind of unnecessary for this application.


The WideBody 13th September 2007 04:25 AM

thanks for the input.

sorry to sound like such a newbie, but what are you referring to when you say TL?

those are very near the dimensions that i was thinking. thank you. box plot says only 1/3" (.333") for port sizes?

i think winisd was reporting something short of 5 inches. i'll have to replot to double check.

mashaffer 14th September 2007 12:23 AM

Sorry, TL= Transmission Line which is essentially a long (1/4 wavelength) pipe loading the back of the driver. It extends the bass response and flattens the impedance curve. The down side is that they are rather large (even when folded) for subwoofer duty (though not nearly as large as a horn) and more difficult to design and tune that simpler boxes.

Search this forum and google for transmission line speakers and you should get a good overview.

My initial simulation had a port length of less than zero so I increased the port diameter and included two ports. The length I gave was for two ports of 4" diameter each. A single port or smaller diameters would be shorter.


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