High ohm subwoofer?

[todd.brust 29]

Here it goes...

At work, we have a Definitive Supercube subwoofer (awesome little things) that has been having problems. It powers up but will have little to no output. That's beside the point. I took it apart and checked the coil to see if it was open. I took my meter and it measured just under 30 ohms. We talked to the Definitive rep and he said that was right.

My question is, what advantages are there to using a high impedance speaker like this? Keep the impedance spike higher in the FR range so the true sub bass isn't affected?

I also figured that the plate amp would have to be designed to match the speaker also so parts cannot be properly swapped out.

Just a curiosity question.

[cobracommander 0]

maybe it uses a tube amp

[JimJ 11]

Keeping the parts proprietary may have something to do with it.

I've never seen a subwoofer like that, but there are plenty of 32 and 16 ohm speakers out there. A lot of tubed output stages have a primary impedance of around 3k ohms, which tend to be suited for higher impedance loads on the secondary For the first couple decades of audio, that's what it was - lower impedance speakers didn't come along until transistors became common.

[///M5 2,833]

Wow. Didn't expect that. I tend to agree that it is solely for proprietary reasons in their case.

[todd.brust 29]

maybe it uses a tube amp

It's make more sense if that was the case but it is definitely a solid state. I've seen 16 ohm taps on my Heathkit but never 32. I am almost certain that it is a class D by looking at the internals.

[helotaxi 46]

Makes the amp cheaper because they don't have to worry about high current devices in the output stage or anywhere really.

[stealth 113]

not to the consumer.

[helotaxi 46]

The goal of a company is profit. Reduce costs to increase margin for a given price point. If that price point happens to be pretty high, so much the better for the company.

Amp will run cooler as well.

[creyc 1]

Interesting helotaxi, I wondered that myself but figured any benefits by reducing high-current devices would be offset by having to run everything at a much higher voltage, although it's possible many of the components are already rated for this.

(I'm not familiar with this particular speaker but some quick math says if it were good for 500w output at this 30Ω impedance, the voltage at the speaker terminals would be about 120V AC! Incidentally the same as your power outlet..hmm, do you even see a large transformer on the power supply side of the amp?)

[todd.brust 29]

Actually, now that you say that, there isn't a large transformer at all. Since there isn't a large transformer, that also helps with the space issue, Those Def Tech Super Cubes are chitpacked full of stuff. I had to remove a PR just to connect the power amp to the pre-amp.

It's actually a 650 Watt plate amp, so you'd need voltage rails sitting right around 140V. It didn't even occur to me that it was probably high voltage. I wondered why the PS caps were rated so high. I guess I was thinking more traditional like 40V rails. Duh. lol

Edited October 7, 2008 by todd.brust

[todd.brust 29]

Actually, now that you say that, there isn't a large transformer at all. Since there isn't a large transformer, that also helps with the space issue, Those Def Tech Super Cubes are chitpacked full of stuff. I had to remove a PR just to connect the power amp to the pre-amp.

It's actually a 650 Watt plate amp, so you'd need an output sitting right around 140V. It didn't even occur to me that it was probably higher voltage. I wondered why the PS caps were rated so high. I guess I was thinking more traditional like 40V rails. Duh. lol