Two 4 ohm speaker and one amp

[Len Amaral]

OK, got the series box complete and it works like a charm. Here is a pic with my multi-meter with the two 4 ohm cabs showing 8 ohms. Massive sound with both 15 inch JBL K-130 speakers.

both cabs.

[John Ducsai]

There ya go !

[Jerry Overstreet]

I'm reviving this old thread to ask a question from the community.

I'm going to be building or buying such a series box as Len's here.

My use is going to be with one 4Ω extension speaker with the solid state combo amp's 8Ω speaker. As I understand it, series wiring is additve so I will have a net 12Ω.

The amps is 8Ω with a 4Ω minimum requirement, so I think I will be good. Thoughts?

[Jerry Overstreet]

Not ideal, but will work just fine impedance-wise.

Why not? What issues will I encounter?

[Jerry Overstreet]

Thanks Georg. The main thing I was concerned about was hurting the amp.

[Jerry Overstreet]

https://www.radialeng.com/product/cab-link/faq

I was looking at this device, but the company advises against mixing impedances but they don't state the reason, so I was wondering if it is just this device or for all similar devices.

That was one of the reasons for asking.

[George Biner]

An 8 ohm speaker in series with a 4 ohm speaker -- the 8 ohm will be twice as loud, roughly. As I said before, 4 ohm speaker cabs are really not a good idea, as they don't play well with other 8 ohm loads and you can't parallel them with any other cabs for most power amps.

[Jerry Overstreet]

OK. I don't have to do this. I have plenty speakers. It's just that one particular 4 ohm cabinet/speaker combination is so sweet. I also have stereo rigs which don't fuss about mixed impedances on ea. separate channel.

For those interested, I'm building a head cab for a MosValve/TubeWorks RT2100 100W 2 channel mono combo amp rig with a minimum 4 ohm load requirement. I have 8 ohm cabinets of both 80s,90s era 1201-8 and 1203-8 Black Widows. I'm wanting to use 2 cabinets most of the time.

So, no problem driving any 2 of those with the RT2100.

I'm a little bit of a nerd and nut and spend a lot of time swapping speakers and cabinets to find the best combination. I admit to being bit anal about it without apologies.

So....one particular 1203-4 ohm 90s vintage BW in one particular cabinet just has the best overall sound. I was considering the series box to mix that cab with one of the other 8 ohm cabs. Mixing them like that might cause the 4 ohm to lose it's magic however, given what's been posted here and I can still use it alone.

I still don't understand why the 8 ohm cab would so overpower the 4 ohm one, but I'll take your words for it.

Appreciate all the knowledge and input...trying to learn a little something as I go.

So, I return the thread back to Lenny's original 2021 discussion concerning using 2 4 ohm speakers and the Series Patch Box.

[George Biner]

The power dissipation in a resistor R with a current I running through it is I^2*R (that's current squared times R). Two speakers in series have the same current, therefore the I^2 term is the same for both. Therefore, 4ohm power is 4x I^2, and the 8ohm power is 8x I^2.

External speaker cabinets are not usually used in series but in parallel. Although, in parallel, the 4ohm would be louder, so same issue.

[Jerry Overstreet]

Thanks George.

[Mark Draycott]

This is a solution that will solve all your impedance matching issues. It's a bit pricy, but has great reviews.

https://www.tedweber.com/z-matcher/

[Stephen Cowell]

If you connect an 8 and a 4 in parallel, you will have less than 4 ohms... this will cause your amp to overheat. If you like the sound of the 4ohm cab, use it alone... disconnect the 8ohm internal speaker when you use it.

[Jerry Overstreet]

If you connect an 8 and a 4 in parallel, you will have less than 4 ohms... this will cause your amp to overheat. If you like the sound of the 4ohm cab, use it alone... disconnect the 8ohm internal speaker when you use it.

I know that. This is an expansion of the topic Lenny started about using 2 4Ω cabs together with a 4Ω combo amp. We're talking about series connections, not parallel. I have the components ordered to build a series box in the style of Lenny's at the top of this page, so should have it ready in a week or so. I'll be using an extension cabinet and trying the 4 and 8 together and besides that, I have several speaker cabs I might want to mix and/or match.

[Jerry Overstreet]

I want to thank you guys for your information and knowledge sharing on this topic. Lenny for generating it and picturing his unit. All the input there, and particularly Jon Light, John Ducsai for the links and diagrams and Georg Sortun for the technical data along with George Biner for playing devil's advocate and advising against using 4 ohm cabs in general. And also everybody that contributed to the issues I posted.

I don't take this sharing for granted, it's very much appreciated. I try to reciprocate also where I can.

I have not put it to use yet, but I have completed the series box. Using the information from all the above, I acquired an enclosure of Acrylonitrile Butadiene Styrene composition [which is boring elongation for ABS] and jacks of the same material so I shouldn't have any issues related to unwanted grounding.

It's good to know that even if I don't use it right now, I will have it to resolve any future issues relating to impedance mismatch.

And, oh yeah, the combination of the 4 ohm and 8 ohm cabinets measures around 11 ohms on a cheap RS DVOM through the series box.

Here's a shot of the box.