BassmanPaul

WOW! Talk about resurrecting a Zombie thread! LOL

I agree that there is something special about a B15. I just love the tone of my B15NF which I use as my practice amp. It makes practice time a pleasure. Mine is in better condition than the one in the link that Bill posted. In your place I would keep the 15" unit as you never know when the urge to play will grab you again. I do hope that the external transformer that you use is rated high enough to operate the amp safely.

If an amplifier has been correctly designed to operate, as all the ones I own are, into a 2Ω load they will run just as well at 2Ω as they will at 8Ω.

It's very unlikely to be class A! Too inefficient for a bass amp.

My comment was better said than unsaid! Many folks have done this and their amp has failed.

I remember that from my JBL days. I still love the brand though I don't use them to play through any more.

Don't connect both amps to the cabinet at the same time. Magic smoke comes out wen you do that!

Indeed that's what I do. After a while it becomes automatic!

Calculating parallel impedances is so simple as just about every one in the world has a calculator built into their phone. Formula is R1 times R2 divided by R1 plus R2. Using 8Ω and 4Ω: 4Ω times 8Ω=32, 8Ω plus 4Ω = 12. 32 divided by 12 = 2.67Ω. QED

Back in the late Seventies I used an H&H scoop twin 15. That was supplanted by a 'stereo' system with a 15" JBL K145 and two TL style cabinets housing JBL K120 12" drivers on each side of the stage. The amp was a SS 200W per side amp that I had designed for the purpose. The pre-amp was my build too. The whole shebang weighed a ton but sounded wonderful. The best part was the amplifier worked first time I powered it on. YEAH! I still own the power amp and it still works. Today I use a 2000W capable Class D power amp pushed by a simple tube pre-amp I again designed for the job. That drives either two or four Acme B2 2x10 three way boxes and I've never been happier.

Looks to me that the amp chassis has ventilated spacers on each side of the amp. Have you taken the amp out of the combo and taken a look?

@Thor please don't forget to keep us up to date with how you find the amp.

Swine!! I would really like one of those.

The cabinets are best if they are identical. If they are of different manufacturers do the battery test and ensure they are both working with the same polarity.

@ZenBasses how are you getting on with your amplifier?

Not all fans are created equal. If you want to replace the fan first check the specs of the installed unit.

A thought that struck me was are the two cabinets working with the same polarity. If one is 'pushing' whilst the other is 'pulling' they are going to fight each other all night long, and that's not a cue for a song!

Maybe the amp doesn't like your playing! I hope you can get your problem sorted.

I don't think that a SansAmp has enough output to drive the power amp properly. It depends on the input sensitivity of said amp. The SansAmp was designed to work into the normal input of a bass amp therefore instrument level.

I know but to be accurate the formula is 1/RTotal =.1/R1 + 1/R2 LOL

Not wanting to argue with you but if your main cab is 8Ω and you try to add a second cab that is 4Ω to a 4Ω minimum amplifier what is going to happen? I was trying to pass on information to someone who may not understand impedances. I wanted to keep matters simple.

An other thing about using a Series box is that you will not get all the power out of the amp that it's capable of. The amp will see 8Ω and thus will give less than it's 4Ω level of 800W. When buying an amplifier to use with your existing speaker cabinets it's wise to consider their impedances and verify that the amplifier is capable of driving them safely.

As for this Palmer box I wouldn't use it. It only has 1/4" phone sockets that are not safe to use with a high power solid state amp. SpeakOns are the only way to go for this service. All you need is a plastic box and three NL4 SpeakOn sockets. If you want to build such a box I'll tell you how to wire it.

I use 4Ω Acme B2 2x10 cabinets and I run them one per channel of a class D power amp. It works well.

Having items stuffed in your ears becomes a necessity after reaching a certain age in this business. My hearing is permanently damaged by playing music. my latest pair of hearing aids cost me $6000 plus. They help but I dislike them intensely. Putting transducers in my ears is less irritating trust me!!