Dummy speakers to alter impedance?

[billfitzmaurice]

It seems like there would be somebody doing this if it were viable.

Your own question answered you just have.

 

[Taylor Livingston]

That's what I thought, but why is it not viable?

 

[coyoteboy]

Invalid Link Removed

 

[Nitto]

So is anybody pursuing this for musical instrument speakers? Are there any really negative attributes for these dual coil speakers? It seems like there would be somebody doing this if it were viable.

they're more expensive than similar drivers with single coils

having 2 voice coils halves the impedance of the driver, effectively doubling the effective power from the amp, but if you use say, 4 dual coil speakers in series, the resistance would be extremely low which wouldn't be too amp friendly (you would reach the cabinet's limits way before the limits of the amp and the inductance would be super high so the sound would be far from dynamic and high in distortion)

yeah, there's ways to get past these issues, but they all involve money so they aren't really practical for most, plus i don't think they sound any better personally

 

[T-Bird]

Hi.

So is anybody pursuing this for musical instrument speakers?.

Not that I know of, but I haven't followed the speaker development too close.

Are there any really negative attributes for these dual coil speakers?.

Yes, there's interference and loss of "performance" from the fact that both the coils are operating in the same magnetic flux and the coil placement in the gap is less than ideal. The ones I've taken apart had only single gap and the coil just had an sort of a center tap.

It seems like there would be somebody doing this if it were viable.

IMHO it's just not feasible to produce such a limited market driver as the manufacturing costs are higher than with regular components.

The compound would theoretically work, but the 3db gain wouldn't justify the doubled cost and the cone area remaining the same. Only if the box size was the only consideration, would compound work as a size reduction method.

IME/IMO as usual
Sam

 

[Luke73]

useless heat

...might be useful in the middle of Winter.

 

[BassmanPaul]

Getting back to the OP yes you can do what you are asking but not with a dummy load. What is required is a matching transformer rated above the maximum output of your SS amp into its minimum load. These are available from several sources such as Peavey and Hammond. The idea is that if you have an eight ohm cabinet, for example, and an amp that will give say 100W into 8, 200W into 4 and 400W into 2 you would connect the cabinet between the common and 8 ohm taps of the transformer and the amp between the common and 2 ohm taps. The cabinet will source 8 ohms but the amp will see it as 2 ohms and supply the full 400W that it is capable of. The biggest problem is the size, weight and price for such a transformer would be horrendous. It would be a much better outlay of funds to change your amp or cabinet.

Paul

 

[bassmodder]

Agreed. I like to think of it as a water tank with two outlets. You open the first one full bore and flow say 10 gal per min. You open #2 up and flow and additional 10 gal per min. So you are now flowing 20 gal per min with both valves wide open. However you are STILL flowing 10 gal per min through each valve. You are simply making your amplifier work twice as hard for the same volume getting to your ears. Your additional 10 gal per minute of flow simply would end up as heat.

 

[billfitzmaurice]

The idea is that if you have an eight ohm cabinet, for example, and an amp that will give say 100W into 8, 200W into 4 and 400W into 2 you would connect the cabinet between the common and 8 ohm taps of the transformer and the amp between the common and 2 ohm taps. The cabinet will source 8 ohms but the amp will see it as 2 ohms and supply the full 400W that it is capable of.
Paul

You may use a transformer or autoformer so the the amp can operate into an adequate load. It's seldom done, as the additional amp weight and size is considerable. McIntosh uses autoformers with some of their power amps, allowing them to drive virtually any load impedance, but they are hi-fi/studio amps where portability is not a concern. Since the amp sees the transformer/autoformer as the load, and not the speaker directly, power output is constant whatever the speaker impedance. Basically, it emulates the operation of a tube amp with a multitap output transformer.

 

[bgavin]

Your own question answered you just have.

-Yoda

 

[GreyBeard]

This post will probably reveal that I don't have a great grasp of the physics involved in amplification. Here's what I'm wondering: Is it possible to have a dummy speaker coil inside a cabinet, that can be switched in or out of the circuit so as to switch between 8 ohms and 4 ohms? It seems like this would achieve what the "Accuswitch" was trying to, but I've never heard mention of anything like this, so I'm guessing it isn't possible, or wouldn't work as I'm imagining for some reason. Any of you knowledgable folks have some thoughts on this?

check this out
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[Petebass]

That's what I thought, but why is it not viable?

For all the reasons mentioned, PLUS, an Isobaric cab sounds just like a normal cab with one speaker in it. Mounting them in an isobaric configuration halves the VAS of the speaker, so the speaker cabinet size is also halved. That's good. But you're now having to pay for and haul around the extra weight of the additional speaker. The idea has it's usefullness but musicians haven't embraced it.

As for dual voice coils, the manufacturer I can think of who has tried this is Tecamp back when they were still called Tec Sound Systems. I'm not sure if they still offer this feature on their current products........

 

[BassmanPaul]

Your own question answered you just have.

Master Jedi you have GOT to stop watching Star Wars my friend!

Paul