BillFitzmaurice.info

I decided to get a bass rig.

I’ve had 4 x BP102 8’s for ages, gathering dust. I had thought to use them in a pair of dual loaded 28” T39’s, but changed my mind.

Went searching, found a cab that recommends BP’s as suitable drivers.
I got the download, a scetchup file from Leland, and that’s what you build from.

A big thanks to Bill, what I’ve learnt from building his designs was invaluable in this build!

I decided to add HF with a piezo. It might have been a mistake ( very in your face ), so if I can find the same size horn with a screw thread, I might change to a compression driver I have sitting around.

I don’t have enough grill material left, I’ve got a sheet on order, though that may take a while to turn up.

The WT400 David Eden head is a cracker, I got it for a pretty reasonable price. Valve ( pre amp ) looks to be in good order, will get some spares though.

All in all, enjoyable, quick, and with the angled baffles to reduce comb filtering, sounds not to bad to this drummers ears...

The only issue with that configuration for bass is that it results in less internal volume, which reduces low end sensitivity. That's not a problem with guitar cabs, as they don't need low end sensitivity.

Bill Fitzmaurice wrote: ↑Sun May 22, 2022 8:59 pm The only issue with that configuration for bass is that it results in less internal volume, which reduces low end sensitivity. That's not a problem with guitar cabs, as they don't need low end sensitivity.

Great point. Does porting change that?
It is ported, 5 of them on the back.

Here's the expected response from the ported cab:
8 ohm BP102: +3.8 dB @ 82 Hz and -0.2 dB @ 62 Hz (upper bass +3.8 dB @ 100 Hz)

The sealed cab specs are certainly lower...

I have a few heads, the WT-400 is my go-to. I use it almost all the time.
One of the finest bass amps ever made, IMO.
The tube is there partially for marketing. From memory, the two triodes of the tube are put in parallell and used to warm up the sound a bit, not as a gain stage. So really a solid state amp.
But it sounds fantastic. The preamp is voiced perfectly, and the EQ controls are magnificent. I even like the 80's style switchable compression.

Top Tips - Start with all the tone controls at 12:00 and make small adjustments. Ignore the Enhance control. If you like that scooped smiley face EQ curve, dial it in with the EQ. Either that or get out of your bedroom and embrace the joy of mids in a live environment <smiley face icon>.

I played it through 4x10s, 2X10s and 1x10s throughout the 80's until now. So a good pairing, if it sounds right to you and the efficiency is adequate.
I find it's a lot louder at 4 Ohms.

Porting doesn't allow the internal volume to be smaller. The ideal volume for the BP102 in a ported box is 4.2 cu ft net, per driver, although 1.5 cu ft per driver can work reasonably well, albeit a bit boomy.

Bill Fitzmaurice wrote: ↑Mon May 23, 2022 11:12 am Porting doesn't allow the internal volume to be smaller. The ideal volume for the BP102 in a ported box is 4.2 cu ft net, per driver, although 1.5 cu ft per driver can work reasonably well, albeit a bit boomy.

Thanks, we'll see how it goes.

Taking on board what Bill said in this thread earlier;

I decided to revise this build some.

I added 7" in depth to the cab.
That takes the cab to an internal volume of roughly 7.5 cubic feet, or 1.8 to 1.9 cubic feet/driver.
Adding 7 inches added 2.7 cubic feet, so as it was it was not even 1.5 cubic feet/driver.

It's not ideal, it's a compromise based on ply on hand, portability, weight, overall size etc.
I always find it nerve wracking enough to mod cabs, but it was already top and front heavy, so I didn't think I could go up in height as well.
I'm hoping the casters will still let the cab go up my truck ramp!
I also changed the piezo to a compression driver with a 2K filter.
I thought it was to much to move the handles and new/more bracing prevented that anyway.

Adding the depth added some stability to the cab in terms of the front/top heavy aspect.
Bass players playing the pre modded cab said it was fine (but not brilliant or crap), so we'll see.

Chopped and adding in 7 inches: And finished, with grille: ^Excuse the finger, it was very sunny and I was struggling to see the phone screen.

Thanks for looking...

Nice job fitting it in there!

Ahhh, that's cool Grant. Nice and clean mod. Well done. Noticeable change in sound?

Bruce Weldy wrote: ↑Tue Oct 10, 2023 9:56 am Nice job fitting it in there!

Cheers Bruce. Good to see you're out and about too!

Seth wrote: ↑Tue Oct 10, 2023 11:05 am Ahhh, that's cool Grant. Nice and clean mod. Well done. Noticeable change in sound?

Thanks Seth.
Change in sound? No idea, paint's still drying

Bruce Weldy wrote: ↑Tue Oct 10, 2023 9:56 am Nice job fitting it in there!