Thinking about 4 10's - combinations and history

[pjd3]

Hello,

Seeing if I can get some insight into the topic of speaker ohms combination with four 10" speakers.

So, I have a cabinet nearly ready that is the width of a Princeton Reverb chassis but 27" tall. My amp should be ready for its "health check with Stan Day in Wilmington, Ma. It is a 40 watt AB763 circuit single channel in a Princeton chassis.

I realized that this cabinet is big enough to hold 4 10's if I'd like, and I recently recall playing a couple of Super Reverbs years ago and loving the tone. Perhaps I could just do this with this amp/cabinet. I like the looks/price and what I'm hearing about those Fat Jimmy C1025's too, could probably win the war with the wife for four of those.

My main interest is if there has been found to be any difference in performance, sound, safely, etc... between say, having four 16 ohm speakers in parallel to a 4 ohm speaker tap, Or, having say two series strings of 32 ohms each in parallel with a second series string of 32 ohms for a total of 16 ohms, just use the whole secondary coil of a multi-tap OT.

We know that Leo Fender for the Super reverb used four 8 ohm speakers in parallel with a single 2 ohm output transformer. I'm wondering if there was any utility to that, either for cost or electrical efficiency, or, if it all doesn't matter too much as long as impedances are matched. I do see that four 10's in parallel,, should one blow would create less of an impedance change than other configurations.

Any insight into this would be really great.

Thanks,
Phil D. (pjd3)

[nuke]

The 4-speaker arrangement of the same impedance speaker can provide 4 x z, z, or z/4 ohms impedance.

With 4 8-Ohm speakers, that's 32 ohms, or 8 ohms, or 2 ohms.

4x8 ohms in series = 32
4x8 ohms in series/parallel = 8 ohms
4x8 ohms in parallel = 2 ohms

The 4x10 Bassman had 4 in parallel, for a total of two ohms. Because speakers had solder terminals on them back in the day, they wired each to a single RCA plug, with 4 RCA jacks on the chassis in parallel.

That's because it left the working musician the opportunity to complete a gig by unplugging a bad speaker. These were professional working-man's tools after all.

By the time the Super Reverb came along, the amp chassis had a single 1/4" phone jack, and there is a 1-inch round eyelet board in the center of the 4 speakers where they are paralleled together. Most of the speakers by that time had "Fast-On" terminals (0.205" if you're curious) and could also be easily unplugged should a lone speaker have trouble. But not all drivers had Fast-On terminals, and Fender sometimes soldered onto the ones that did. But the spider in the center worked with everything.

I'm working on a similar project, built around a re-issue '59 Bassman cabinet carcass I've had in the garage for a long time. Back when they were introduced, people sometimes "upgraded" to cabinets built of finger-jointed solid pine, rather than the plywood construction of the re-issue. So I got the complete carcass for free.

Still deciding what speaker to use. One of my strong design goals is to keep it as light as possible. Speakers will be a substantial part of the weight. I have some CTS alnico pulled from organs, and I've tried the re-issue C10R, both just a smidge under 3lbs each.

I love the old Reverend AllTone 1030's, and I have several NOS ones. But they weigh since they have a bigger magnet.

The original Bassman 5F6A and Super Reverb 2-ohm transformers are quite heavy, as is the power transformer. I don't need the 40-50 watt output of the originals, so considering 6V6GT or EL84 output for 18-22 watts. It will probably get spring reverb with solid-state electronics for simplicity sake. Want to make it a "fun-size" Super Reverb lite.

[pjd3]

Very cook nuke, sounds like a fun project.

With this cab I had originally intended to use a Weber 12F150B that I had. But then I was reading threads on "12" vs 10" " and recalled how much I like the Super Reverb amps. I made the cabinet 'Big" for having only one 12" speaker. I think I erroneously was thinking it would be fuller sounding with more dimension and wood. And I suspect it would probably be but, maybe a little waste of "Wood and space". I think 4 10's would fit in it if they are offset a bit (Princeton chassis = 18.5", two 10" speakers are 10.1" diameter. I'll have to do some graphic drawing to see if or how that works. the thing is 27" tall. Might do it. Was also thinking about the 12" Weber and two 10's with the 10's set back a bit to line up the magnets on vertical plane in case phase was an issue.

But yeah, looks like there are a number of ways to skin this cat. I'll find the one that works with what I have.

Thanks for coming by nuke.

Best
Phil D (pjd3)