LDS sealed cab build for Ampeg B25B
 

I have had a 1972 blackline (square graphics) Ampeg B25B 55-watt all tube amp head for a while, with no cab. So I have decided to have Don Oatman at LDS make me a cab for it.

For those of you who are familiar with the B25B, you already know that is has two 16-ohm output jacks.

I happen to like the sound of an all tube amp into a sealed cab with 10's (I have a 1991 Ampeg SVT-II non-pro that I run into a Berg NV610, and it sounds glorious). My plan is to use the B25B as my practice rig, so I don't want a huge cab for the B25B rig. For gigs, I plan to use a Lehle splitter box and run the SVT rig and the B25B rig at the same time, using the SVT rig for the cleaner sound and the B25B rig for power tube saturation grit when desired.

Okay, for the cab build, I am planning on going with what is essentially a "half fridge" cab, i.e., a 4x10 cab with a pair of sealed chambers. As most of you know, the Ampeg 8x10 fridge cab is comprised of four separate sealed chambers, each with a pair of 10's, so my build would be half of that.

But I'm going to do something a bit different. Rather than have the chamber divider horizontal like they are in the fridge cab, I am going to have it vertical, so I essentially will have a pair of vertical 16-ohm 2x10's, each with their own input jacks in the back of the cab. That way, I can run just one vertical pair if I want, or both vertical pairs for more volume, depending on the situation. Using just one vertical pair will provide better dispersion than using a horizontal pair, hence the choice for vertical pairs.

I plan to go with Eminence Legend B810 speakers which are 32 ohms each. These are what Ampeg is using in their Heritage and 810e cabs.

I have already spoken to Don about this build, and we both agreed it will be a good match for the B25B amp.

And of course, if I ever want to use the cab as a typical 8-ohm cab, all I have to do is daisy chain a short speaker cable from one side to the other in the back of the cab, as I plan to have twin Speakons for each vertical pair.

This sealed 4x10 cab will be similar to having a pair of SVT210AV cabs, except the greater internal cab volume per driver will match that of the Ampeg fridge cab. My outer cab dimensions will be 25h, 25w, 16d. The 24" wide B25B amp head will fit nicely on top of the cab.

Once Don completes the build, I will post up with a tone report!

Sincerely,
Sactobass

Great idea.

Thanks Bmf. It should work pretty well.

Se if you can get the fliptop neos :)

Thanks RP, and I know gauss is gauss, but I have decided to stick with the Ampeg Heritage/810e design as closely as possible.

But I appreciate your comment!

Ampeg actually doesn't use the B810's in their cabs. They use the 86-032-01 for the Heritage and a speaker made by Eminence China in the imported 810e's.

Just my opinion but I think you'll get closer with custom eminence woofers designed to sound like Ampeg by experts than you will with off-the-shelf woofers. And lighter too!

Instead of having two completely isolated jacks, and having to use an extra cable if you want to run them at 8 ohms, why don't you just have a jack plate with 3 separate jacks so you can do all the necessary wiring internally?

Also, with such low wattage, why bother with pricier and more fragile speakon jacks instead of just some nice 1/4" jacks that will last forever and if they don't will be super easy to replace? For my setup (which is either running about 350 or 500w), I just use 2 12 gauge 5' cables with heavy duty plugs, and they work just fine. What happens if you take the cab somewhere, and oops! forgot my speakon cables, sorry guys, guess I'll have to go back and get them. Be back in an hour. With 1/4", you have a much better chance of being able to borrow some. Plus, you could probably get by with instrument cable in an emergency.

Anyway, sounds like an interesting cab idea. Might also work well for a stereo guitar rig, depending on how those speakers sound.

Thanks JimmyM. Can an average joe like myself (or a cab builder like Don) obtain 86-032-01's?

EDIT: never mind. The answer is yes. Google is my friend! They are a little higher in price than the B810's, but only by about $15. A trivial dollar amount! Thanks again JimmyM.

I loved my B25B, I was amazed at the responsiveness of the clean notes. When people use descriptions now of "glassy", smooth", I know what they are talking about. I was so addicted to that, I never tried to crank it.

I'm sure Don will do this justice, looking forward to the review.

Thanks RP. I have decided to go with the 86-032-01's.

Thanks SB45. I will definitely post up with a tone report. Don is a bit swamped right now, so it will probably be six weeks or so before I receive the cab. No prob. I'm in no hurry.

subscribed. :)

I chatted a bit more with Don this evening about the build. We decided to stick with the B810's. Don said they have better excursion and freq response than the 86-032-01's.

It's all good! :bassist: