New cab project / Peavey Max 115 combo mods

[Dave CALEYRON]

Hi bass people !



I need your advice :



I recently got for free a Peavey Max 115 amp (300w / 8ohms version)from the owner of our rehearsal place, because it was cutting after two minuts, only bips were getting out of the speaker. He decided he did not had the time to have it repaired and wanted to dump it…..lucky me !

A capacitor lost its metal cover, I found it in the chassis, glued it, easy fix for the moment, and stable.

I like the sound of this Peavey !



I don’t need another combo, as a proud owner of a Fender Rumble 500c, but would like to rehouse the Peavey speaker in another cab to get an extension (for now, according to my experiments in my living room at medium/high level, it seems to match, soundwise). The new design would match the Fender too (grillcloth, etc).

I’ve already built cabs, so I know the inner volume and vents must be the same. The Peavey design is a bit complicated :The actual port (from the inner room)fires through the chassis and the electronics and cables, and the air is finally led through a thin blade between the logo and the speaker, vertically. The area of this blade is far different from the area of the port getting out the inner room of the cab.

Here’s my question : should I respect the actual design completely, and if I don’t, which port area should I create ?



It would end with two separate heads and two 8 ohms cabs, allowing me many combinations.

 

[Redbrangus]

I don't see any point in trying to faithfully emulate the 'design', such as it is, if you're seeking just an extension cab. From your description, it sounds like the part of the enclosure that housed the chassis is serving as a ducted port, but placed on the outside of the box. Maybe. At any rate, I wouldn't bother trying to exactly copy it. It's going to be a bit difficult to do it "right" without the T/S parameters for the driver, but I'd go in the direction of designing the cab to be similar in size and form-factor to your Fender. I'm presuming the overall volumes of the two cabs are pretty much the same -- if the Peavey cab is functioning as I think it is, the volume of the amp enclosure would be included in the overall internal volume of the speaker cab. Then you need to tune that enclosure: probably the best you can do is tune it to the driver's resonant frequency (Fs), which you will need to determine empirically. Do a search here for "rice test" -- there will be a thread that describes in detail how to do that. Once you have that, there are some simple on-line calculators that will give you the dimensions for a ducted port based on the internal volume and desired enclosure resonant frequency (Fb)

My apologies for not searching that information out for you, but I must go to get some more coffee. Bonne chance!

 

[Dave CALEYRON]

Thanks a lot for the rice tip ! I ll try it soon. By the way the speaker looks a lot like a peavey pro 15, and the ts parameters are easily available. I ll try an email to the peavey's customer service.