Speaker Wiring

[JonO)))]

My "theory" was premised on what I read in the link that Ed took us to, under the heading "8 Speakers - Series/Parallel Wiring; In Phase".

There, albeit with 8 speakers rather than 4, we are told that individual speakers rated at 8 Ohms will create a total load impedance of 4 Ohms if wired in series/parallel.

I therefore theorised that the same wiring could be applied to 2 sets of 2 speakers in my quad, with the result that four 8 Ohm speakers wired in series/parallel would give a total load impedance of 4 Ohms.

Would you care to elaborate on why this is not the case?

[EdBass]

As I posted before, with four 8 ohm drivers you have the choice of 32, 8, or 2 ohms. It's not really a "theory" at all, it's just the way it is. The reason that eight 8 ohm drivers can be wired for 4 ohms is best described by thinking of the 4 ohm 810 as two 8 ohm 410's wired together in parallel.

Theoretically, you could wire it for 2 ohms and put a resistor in the circuit to obtain 4 ohms; but that is such a terrible idea on so many levels it's not worth explaining. 
It also would be counterproductive to the reason you want a 4 ohm cab in the first place, it wouldn't be louder than an 8 ohm cab, probably quieter in fact.

As far as getting "full use of the amp", the difference between running the amp at 8 ohms vs. 4 ohms isn't really that great.
A lot of people assume that just halving the impedance will make your rig about twice as loud.
I'm not real sure about the Beta output with an 8 ohm load; I'm going to guess about 60 watts or so. If that is correct, you might pick up a decibel or two in volume by running the same cab but at 4 ohms.
IMO not worth messing with; you probably won't even be able to tell it's louder without using a dB meter, and the amp is much happier and cooler running at 8 ohms.

If you want louder, add another 8 ohm 410. That will pump things up!

[JonO)))]

Thanks Ed.

I'm not actually looking for louder - I was simply concerned about the mismatched impedance between the amp and speakers. Since the Betas are rated 100W at 4 Ohms, and there is no switch on the amp to raise the impedance to 8 Ohms, other people on this site had me worried that an 8 Ohm load was not optimal (and therefore potentially bad) for this kind of amp.

Rest assured, I am happy to know that "the amp is much happier and cooler running at 8 ohms"!

How about this then: There are two jacks on the back of my 410. There are also two output jacks on the back of my amp.

Is there any reason why I can't, inside my 410, wire a set of two speakers in parallel and connect them to a jack on the 410, and do the same with the other set of two speakers. The impedance of each of the two sets of 8 Ohm speakers would then halve to 4 Ohms. I could then run a lead from each output on the amp to each jack on the back of the 410.

Cheers
Jon.

[EdBass]

 

Thanks Ed.

I'm not actually looking for louder - I was simply concerned about the mismatched impedance between the amp and speakers. Since the Betas are rated 100W at 4 Ohms, and there is no switch on the amp to raise the impedance to 8 Ohms, other people on this site had me worried that an 8 Ohm load was not optimal (and therefore potentially bad) for this kind of amp.

Rest assured, I am happy to know that "the amp is much happier and cooler running at 8 ohms"!

I think you may be confusing tube amps with transistor amps.
Tube amps use transformers to match the load impedance with the impedance of the output stage of the amp, they make the same power with any speaker impedance but you need to select the output transformer output (referred to as output “tap”) that matches the load with the output stage.
Transistor output stages don’t need to be matched, they will also put out increasingly more power the lower the load impedance gets down to the point where the amp fries. With an 8 ohm load your Beta is more stable than with a 4 ohm load, but will make less power with the 8 ohm load.

How about this then: There are two jacks on the back of my 410. There are also two output jacks on the back of my amp.

Is there any reason why I can't, inside my 410, wire a set of two speakers in parallel and connect them to a jack on the 410, and do the same with the other set of two speakers. The impedance of each of the two sets of 8 Ohm speakers would then halve to 4 Ohms. I could then run a lead from each output on the amp to each jack on the back of the 410.

The reason you can’t do that is because there is really no way to circumvent Ohm’s Law.
There is only one actual output on your amp. Those two jacks on the back are that single output split, and when you spilt the output like that the jacks have to be either in series or parallel. The jacks on the back of your amp are in parallel so you need to factor that into your impedance calculations, using your idea would actually be showing 2 ohms to the amp, which I believe is below what a Beta is rated for.

There are lots of threads about both of these issues; a search is your friend!