Engineers & Gurus- I'm rewiring a 6x10, double check my math?

[McNothing]

The attached jpg has all my work, but I'll summarize in case it isn't clear:

I currently have a SUNN 6x10 guitar cab. All speakers are 8 ohm, wired in series-pairs, and then those pairs are wired in parallel together. 5.33 ohms total (marked as 6 on the cab, but close enough).

(8 + 8)
(8 + 8)
(8 + 8)

I'd like to swap in four CTS 32 ohm speakers, the good ones from early SVT cabs. I'm thinking I combine them with two of my existing SUNN speakers, and I can keep the total impedance the same.

Like so:
The two 8 ohm speakers are connected in series, making (essentially) one 16 ohm load. The four 32 ohm speakers are wired in parallel with the 16 ohm load. If my math is correct, impedance should end up exactly the same, 5.33 ohms!

(8 + 8)
(32)
(32)
(32)
(32)


I used ohms law with Voltage @ 1V. Anybody notice any mistakes on the sheet?

I'm open to suggestions on where I could post this (is there a DIY amp forum somewhere?).

 

[Downunderwonder]

Your 4 32ohm parallel is 8ohm. But unless they are in their own box internally and sealed you could easily find it sounds terrible following up with no sound from them.

 

[McNothing]

Your 4 32ohm parallel is 8ohm. But unless they are in their own box internally and sealed you could easily find it sounds terrible following up with no sound from them.

Can you expand on that? If the four 32 ohm speakers were alone in the circuit, it would be an 8 ohm load... but we can't just divide by 4 in this scenario because we are mixing speaker loads. As far as I know you can't calculate those 4 speakers alone without considering the rest of the circuit. Did you get a different final cab rating?


The sound will definitely be unpredictable, I agree. Just want to get the wiring correct for my SVT as a starting point. Can always go back to where I started!

 

[B-string]

Impedance load was not the concern, acoustic loading inside the cab is. Are there three separate sealed chambers to work with? Your math was good with the exception of four 32 ohm in parallel being 8 ohms not 16 ohms.

 

[Downunderwonder]

Yeah, your result of 5.something is correct but the cab it all goes in is a guitar cab so I assume not sealed. Good way to shred valuable vintage bass drivers.

 

[McNothing]

Impedance load was not the concern, acoustic loading inside the cab is. Are there three separate sealed chambers to work with? Your math was good with the exception of four 32 ohm in parallel being 8 ohms not 16 ohms.

Gotcha- yeah Im not concerned with acoustics right now, just impedance. Those four speakers aren't 8 ohms anyways, since there is a 16 ohm load in parallel with them, fyi.

I think you are misreading something in my math. Top right corner I combined the two 8 ohm series speakers into one load for calculating amperage. Is that what you are seeing? I wouldn't try to calculate four of the 6 speakers on their own without factoring the other loads.

 

[McNothing]

Yeah, your result of 5.something is correct but the cab it all goes in is a guitar cab so I assume not sealed. Good way to shred valuable vintage bass drivers.

You assume wrong. In fact both of your replies have been incorrect. Do you have anything useful to add?

Edit: You know what, I'm being a dick. Apologies- I totally misread your tone. You are right about the drivers, I'm taking measures there. Really just need some reassurance I haven't botched the numbers.

Leaving it up as a testament to my bad attitude.

 

[Downunderwonder]

Careful as ye go then.

 

[B-string]

Make it easy on yourself Speaker Impedance Keep in mind your are dealing with AC impedance not DC resistance.

 

[McNothing]

Make it easy on yourself Speaker Impedance Keep in mind your are dealing with AC impedance not DC resistance.

Thanks B-String, I was looking for something like this.

 

[B-string]

Thanks B-String, I was looking for something like this.

Your welcome. You have five circuit branches, since four are all the same they can be treated as a single load (in parallel) the series is treated separate as without both drivers it is no longer a complete citcuit. It must be functional to add in parallel or series to the total load.

 

[McNothing]

You're right, Downunder too... I get 5.33 ohms even if I consolidate the 32 ohm speakers to 8 ohms.

Well there you have it. My math was right but my understanding of circuits was completely wrong. Foot meet mouth.

 

[moody]

The big thing with this is that the speakers may not work well together and even in a seperate acoustic chamber it may not be the right sized cab for these speakers.

 

[McNothing]

The big thing with this is that the speakers may not work well together and even in a seperate acoustic chamber it may not be the right sized cab for these speakers.

Yeah, I agree that the result will be unpredictable. I'm under no illusion that I can out-design Ampeg or SUNN engineers.

BUT- Its already making a great bass cab AS-IS, and the damn thing fits in my Corvair. The SUNN cab is already roomy and sealed, and if what I hear is promising I could even section into chambered rows.

For 15 minutes of soldering speakers I already own, I'll give it a go. Just didn't want to blow my amp during the experiment.

 

[moody]

BUT- Its already making a great bass cab AS-IS, and the damn thing fits in my Corvair.

Then why change anything?

 

[McNothing]

Then why change anything?

Because I think SVT-specific CTS speakers will make an improvement. The fact that it sounds good with guitar-voiced speakers leads me to believe that the platform could handle real bass speakers.

 

[moody]

Because I think SVT-specific CTS speakers will make an improvement. The fact that it sounds good with guitar-voiced speakers leads me to believe that the platform could handle real bass speakers.

Intuition? Or hope? Definitely nothing scientific.

I wouldn't mix speakers. Better internally subdividing to the exact half size internal volume of an existing sealed 8x10 that works with those speakers and leaving the other 2 speakers disconnected. (Make them the top 4 to raise the perceived level).

 

[McNothing]

Intuition? Or hope? Definitely nothing scientific.

I wouldn't mix speakers. Better internally subdividing to the exact half size internal volume of an existing sealed 8x10 that works with those speakers and leaving the other 2 speakers disconnected. (Make them the top 4 to raise the perceived level).

This IS scientific, I'm just not being academic about it. I'll have the speakers in the cab in 15 minutes and can see how it sounds. Record before, record after, conclusion.

If you read the schematic above, I'm using the 8 ohm speakers to keep impedance consistent... If you can think of a wiring configuration to get four 32 ohm speakers to work with an SVT I'd be right there with you.

 

[moody]

This IS scientific, I'm just not being academic about it. I'll have the speakers in the cab in 15 minutes and can see how it sounds. Record before, record after, conclusion.

If you read the schematic above, I'm using the 8 ohm speakers to keep impedance consistent... If you can think of a wiring configuration to get four 32 ohm speakers to work with an SVT I'd be right there with you.

Better off just running the Svt at 8ohm. Quite possible on the 4ohm setting.

 

[moody]

Ps the unscientific bit I was mentioning was your conclusion that what you had sounded good for bass therefore putting different speakers in would still sound good for bass. Testing and conclusions may be somewhat scientific (trial and error). What's wrong with comparing some on paper cabinet volumes?