Wiring 2 older 15ohm speakers in a cabinet with an 8ohm speaker.

[Hobojangles]

Hello all,

A friend and I are building a guitar/violin cabinet for another one of our friends. He has been collecting odd oldschool speakers from cabinets and anywhere he can really. He has 2 15ohm metal magnetic coil 10w speakers that we want to wire in a cab with a singular 12" speaker which is 8ohm and around 50watts. The head which is running the cab is also an older one running 7.5ohms and 40watts. We need to know how to wire these speakers to arrive with the best result.

Attached is a picture which details the setup a bit more.

An externally hosted image should be here but it was not working when we last tested it.

 

[rem280]

If you wire the two 15 ohm speakers in series and then parallel them with the 8 ohm speaker you will end up with an impedence around 6.3 ohms (1/30)+(1/8)= 38/240
240/38= 6.3. You will end up with much more power delivered to the 12" than the others which may be good or bad. Are these speakers all full range I'm assuming your not planing on running a crossover. Do you have more info on the amp does it have taps for
Different impedance you said it was for 7.5ohms that sounds unusual

 

[Hobojangles]

I don't have too much info on the drivers yet. I know that the two 6x9's are old radiogram speakers. As I said this guy is a bit of a collector, he has really old australian made drivers and also an old australian made amp head which is why it's only 7.5 ohms. Not planning on having a crossover. 6.3 ohms is too little to run with a 7.5 ohm head is it not? or is that sort of small difference not that bad. is there any way to increase the resistance of the cab without ******* up the drivers?

 

[tinitus]

Not planning on having a crossover.

hmm, and I would have suggested just that

reason
those oval are vintage 10watt
and thats probably all we need to know about them
would probably serve them best to have a cap in series

but thats not the hardest part
it would be good to also know a bit more about the 12"

but probably best to try with a relatively small cap on the 10watt
and thats all
oh, yes, and maybe cab should better be open back

 

[Hobojangles]

We are thinking now of wiring the 2 15 ohm in parralel to get 7.5 ohms, and then in series with the 8 ohm speaker so it's 15.5 ohms total. How would you go about wiring this?

 

[PeteMcK]

The power rating of the 15 ohm drivers is too low for this kind of use, stick with the single 12".

 

[sreten]

Hi,

The single 12" is by far the simplest and most common sense
way of doing it, the other drivers won't help much at all, and
likely make the end result worse, not better.

rgds, sreten.

 

[head_unit]

Hi,

The single 12" is by far the simplest and most common sense
way of doing it, the other drivers won't help much at all, and
likely make the end result worse, not better.

rgds, sreten.

Yeah, what he said. Because:
- If the cabinet is sealed, the 12" and 6x9s will push against each others' cones, not a path to good sound
- Ancient 6x9s won't handle much power without melting, most likely
- Series connecting speakers is basically never a good idea, with a few oddball exceptions.

Why do you want to do this anyway? Seems very bastardized. Are you trying to get more high end? If so, some kind of mid or horn might be better...