Multi watt reduction 4x speaker cab

RetiredUnit1

RetiredUnit1

Well-known member
So, I got this great idea. I ordered some 50w resistors so I could put a 1/4 power mod on a amp I'm building (mod from Rob Robinette's site) and the thought suddenly smacked me in the head like cold guacamole in a food fight on Cinco de Mayo!

I can take four of these, and wire them into my 4x10 or 12 speaker cab, with four switches wired in line with hot. Each switch would either send juice to the speaker or the resistor.

I could attenuate the 4x cab with a simple flip of the switch. So the sound guy says "you're too loud" and instead of screwing around trying to get the right sound, you could just flip a switch, or switches, until you're good with no change in the output sound except for fewer speakers.

At home you could just flip three switches and basically play with 1/4th of the moving air. Or flip all four for a dummy load and hook up the oscilloscope without fear of hearing damage.

Too easy to be true? Am I just one too many margarita's to the wind on this Holiday??? :unsure: :sneaky:
 
Cybercow said:
Mind you, power resistors are a 'non-reactive' load and will not react like the coil of a speaker. When wired properly, they shouldn't do any damage. Power resistors are a quick & dirty method of power soaking.

Check out this article about "Designing a Reactive Load". And/or this article on "Dummy Loads".
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Thanks!

You know, I was looking at the 1/4 power mod for the inside of an amp. And I couldn't understand why it was one 8ohm, and one 16 ohm resistor. It just hit me, it's mimicking the parallel/serial wiring of a 4x speaker where 4x8r=8r! One 8 to raise up to 16, one 16 to bring it back to 8.

I'll check those out, but probably not today. My new RIC 620 delivery is scheduled sometime in the next 5 hours. :cool:
 
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My experience of using a dummy load and an oscilloscope while 'chop sticking' is that non reactive dummy loads work fine for FINDING oscillation and don't induce it. The dummy load consisted of 400w resistors of various values with a patch panel which Paramount studio's discarded and my friend Bob found in the trash while leaving for the day, he was an A/V tech there for around 30 years.

I've learned a lot from Aiken's site, as well as from Robinette's site, both have a remarkable amount of tube knowledge.

I was deciphering this '8R in serial and 16R in parallel on a switch' layout when the idea hit me that it could be incorporated into a speaker at the speaker level, one switch to choose between either resistor or speaker per position in a 4x. I've ordered the resistors from AliX. Figured I'd try it...

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I re-laid out the above layout to be a bit easier to follow, and put together. This is a 5e3 I'm going to build in a 17x8x3 hammond chassis instead of that sardine can of an original layout.

Since I'm putting this together I figured I'd try to see how it works and sounds before I try applying something similar on the speaker side.

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