Advice needed

[Bungo Mike]

So I’m wanting to buy this cab to sit on top of my Ampeg SVT15e (8ohm) but it’s 4ohm. Can I re wire this to 8ohm so I can use it with my 4ohm head. Thanks 

[BassmanPaul]

Most likely two 8Ω drivers wired in parallel. The best you cab do is wire them in series for 16Ω.

[itu]

1) No. 

2) Yes... partially.

 

1) 4 ohms here equals 2x8 ohms in parallel. If you wire them in series, you get a 16 ohm speaker. You could try this. You decide whether the divided power is enough for you.

 

A 300 W amp pushes 100 W (1/3 of the total power) to the 16 ohm cab, and 200 W to the 8 ohm cab. Depending on the sensitivities of the speakers, the loudness of each cab may be whatever.

 

 

2) If you use one element only, you have an 8 ohm speaker. 

 

It would be feasible to replace the other element with a wooden plate. Otherwise the element with no connection would be a spring like component in the system. That would raise the lowest reproducible frequency (think it like the cab would have a leak).

 

 

Note:

The reason for the parallel connection (in cabs that include more than one element) is that if one element burns, there's still the other(s) left. A very good feature if you have a valve/tube amp because it always needs a load of some kind.

[nekomatic]

On 24/03/2025 at 20:32, itu said:

It would be feasible to replace the other element with a wooden plate. Otherwise the element with no connection would be a spring like component in the system.

Unless the cabinet is internally divided into a separate airtight compartment for each speaker then this would effectively double the cabinet volume seen by the remaining speaker, wouldn’t it?

[bremen]

Yes it would, and likely reduce the power handling of the remaining speaker as it'd have less acoustic suspension and be easier to drive past its maximum allowable excursion.

[Phil Starr]

You beg the question of: what are you trying to achieve by sitting this cab on top of your Ampeg cab?

 

If you are simply trying for more volume then a second ampeg 15 would be a better bet. It may also be that the Peavey cab on it's own would be louder than the Ampeg.

 

Have you tried the Peavey with the Ampeg? The results of merging cabs is a bit unpredictable for good technical reasons. If you are trying to aim for a particular tone this isn't the way to get it.

 

The probability is that there is no way you can run these two cabs together. You could try running them in parallel (both cabs simply plugged into your amp) this will mean both of the 12's and the 15 will each share the power equally.The problem then is the amp will be driving into 2.67ohms and not all amps will do this. The extra current demand may well overheat the amp leading it to shut down if it is well protected or to burn out if it isn't. If you re-wire the two 10's to make a 16ohm cab then this will reduce the output of your tweeter and your crossover to the horn will be all wrong as it is designed to work with the 4ohm speakers. in any case the two tens will be getting a lot less signal than the 15 which will mean they won't be as loud and your sound will be dominated by the 15 .

 

Dozens of people have asked how to mix an 8 ohm cab with a 4 ohm cab and the answer remains the same. If you want to change your set up then the minimum you need to do is to buy another 8 ohm cab. Don't buy this one, it just doesn't match.

[Bungo Mike]

8 minutes ago, Phil Starr said:

You beg the question of: what are you trying to achieve by sitting this cab on top of your Ampeg cab?

 

If you are simply trying for more volume then a second ampeg 15 would be a better bet. It may also be that the Peavey cab on it's own would be louder than the Ampeg.

 

Have you tried the Peavey with the Ampeg? The results of merging cabs is a bit unpredictable for good technical reasons. If you are trying to aim for a particular tone this isn't the way to get it.

 

The probability is that there is no way you can run these two cabs together. You could try running them in parallel (both cabs simply plugged into your amp) this will mean both of the 12's and the 15 will each share the power equally.The problem then is the amp will be driving into 2.67ohms and not all amps will do this. The extra current demand may well overheat the amp leading it to shut down if it is well protected or to burn out if it isn't. If you re-wire the two 10's to make a 16ohm cab then this will reduce the output of your tweeter and your crossover to the horn will be all wrong as it is designed to work with the 4ohm speakers. in any case the two tens will be getting a lot less signal than the 15 which will mean they won't be as loud and your sound will be dominated by the 15 .

 

Dozens of people have asked how to mix an 8 ohm cab with a 4 ohm cab and the answer remains the same. If you want to change your set up then the minimum you need to do is to buy another 8 ohm cab. Don't buy this one, it just doesn't match.

Thanks Phil. This is really appreciated

[BassmanPaul]

Physics is a pain ain't it? LOL