speaker impedance

[mr fab]

hi
I usually hang out in the pickup forum. but have had this nagging question regarding guitar speakers:



why don't they make speakers with tapped voice coils for dual 8 ohm and 16 ohm operation?

is it possible? or is there some technical reason against this..... thought it would have been a practical and obvious thing to do

[pdf64]

Maybe the dead weight of an unused section, eg for 16 ohms when used at 8 ohms, would result in the impedance options performing rather differently?
Perhaps 2 equal windings that could be series or parallel would overcome that, but then the impedance / frequency curves between the options would differ too much, and the 8 ohms standard would have to be paired with 2 or 32 ohms, neither of which may have much appeal.
So a lot easier, same / greater benefit, and less downsides, to have tapped OT secondaries.

And bear in mind all the guruspeak regarding those, about how using the whole secondary winding always sounds better (anyone that can't hear it having tin ears).

[nashvillebill]

The Watkins woofer had two voice coil windings, they could be used in series or separately. Never really caught on, though some early Infinity speakers used the Watkins woofer with two separate crossovers--one for each segment of the voice coil. I have a couple of these woofers sitting here unused, they need refoaming.

[mr fab]

yes I have seen woofers with two voice coils and there seems to be quite an art involved driving them

but what I wanted to know, is why they are not used in general guitar speaker community

[Chuck H]

yes I have seen woofers with two voice coils and there seems to be quite an art involved driving them

but what I wanted to know, is why they are not used in general guitar speaker community

As noted by pdf64, it's much less difficult and less likely to create tonal inconsistencies to have impedance taps on the OT secondary. I wouldn't be inclined to buy a dual impedance speaker for three reasons.

Amp and speaker combo's are already mated well (ideally), so why change speaker impedance within the system?

Speakers become a fairly permanent part of a system as installed and aren't the sort of thing one wants to change on a whim because it's a lot harder than flipping a switch.

The amps can already be adjusted for matching. It's easy and non obtrusive,

I'm also not too concerned with being able to use the same speaker with multiple systems for all the reasons stated. Unnecessary.

Remember that we're talking about what is primarily a POWER system rather than a tone shaping system. One shouldn't ideally use impedance mismatch as a tone shaping method anyway, even though some do. The speaker and amp pairing needs to be more "fixed" than variable to provide reliable operation. To this end the system is uncomplicated.

[Enzo]

Sounds like a solution looking for a problem to solve.

[R.G.]

Hold your calls, we have a winner!

Maybe the dead weight of an unused section, eg for 16 ohms when used at 8 ohms, would result in the impedance options performing rather differently?
Perhaps 2 equal windings that could be series or parallel would overcome that, but then the impedance / frequency curves between the options would differ too much, and the 8 ohms standard would have to be paired with 2 or 32 ohms, neither of which may have much appeal.
So a lot easier, same / greater benefit, and less downsides, to have tapped OT secondaries.

The moving mass and space for wires in a speaker voice coil is CRITICAL. For best operation of a speaker, you want zero mass and zero space taken up. Mother Nature says that you have to have space for real wires, and that there is some resistance in there. The mass of the whole cone assembly is CRITICAL, and the voice coil adds nothing acoustically - just that nothing happens without it.

So no - there should never be unused wires in the voice coil.

And bear in mind all the guruspeak regarding those, about how using the whole secondary winding always sounds better (anyone that can't hear it having tin ears).

Guruspeak. Ah, yes, guruspeak on the internet.

Filled windows in transformers and using all the wires is connected to "sounds better" only tangentially. The correlation between needing to make the smallest, lightest transformer for economic reasons is the link between the two. What makes using all the wires good for sound is that not using all the wires means the spaces between the active wires is filled with inactive wires, and that increases the leakage inductance. Bigger cores can help this, but it makes the core and copper more expensive.

[Chuck H]

Filled windows in transformers and using all the wires is connected to "sounds better" only tangentially. The correlation between needing to make the smallest, lightest transformer for economic reasons is the link between the two. What makes using all the wires good for sound is that not using all the wires means the spaces between the active wires is filled with inactive wires, and that increases the leakage inductance. Bigger cores can help this, but it makes the core and copper more expensive.

Always good to have the devils advocate around But isn't the issue of unused secondary windings (for the actual transformers we use and the purpose for which we use them) small enough that it's really NBD? Certainly a much smaller offense than unused wraps on a speaker voice coil.?. And that was the point I think.

[R.G.]

Yes, it is hugely a smaller issue, almost unnoticeable. I wasn't clear - that's what I was trying to say, along with stating what I thought the grain of truth might be; a variation on my signature:
The music world seems to be a three-way race between the princess and the pea, the blind men and the elephant, and the emperor's new clothes.

[catalin gramada]

hi
I usually hang out in the pickup forum. but have had this nagging question regarding guitar speakers:



why don't they make speakers with tapped voice coils for dual 8 ohm and 16 ohm operation?

is it possible? or is there some technical reason against this..... thought it would have been a practical and obvious thing to do

Hi
You problem is allready solved. Take a look into MTX offer:http://international.mtx.com/t/libra...fer-voice-coil ...if you enjoy earthquakes

[Chuck H]

Hi
You problem is allready solved. Take a look into MTX offer: http://http://international.mtx.com/...fer-voice-coil ...if you enjoy earthquakes

Is this link working for anyone else?

[loudthud]

Try this: Subwoofer Voice Coils: Single vs Dual MTX Audio

[mr fab]

I was coming at it from a different angle:

1. if a 8ohm/16ohm speaker was available, then the manufacturer would theoretically only have to make one variant
2. many guitarists use amp heads and have separate speaker cabs. some amps are fixed in their output impedance (usually older amps like fenders and vox) and others provide switchable options. depending on the head and the speaker you have, then obviously, you have more choices available for a particular gig, and or speaker config you may wish to use at that particular time. ie use multiple speakers, or single speakers.....

as mentioned initially, I am aware of subwoofers taking advantage of this, but have not seen any wider range speaker with this feature

many guitar speakers are inefficient anyway, especially the older designs , its the tone of the speaker we shoot for, not the efficiency......

[mr fab]

Sounds like a solution looking for a problem to solve.

simple scenario, which I gather many of you have encountered..... customer brings an amp in for repair.... you find the amp is fine.... the speaker has blown and the OT on the amp has 4 ohm tap only (ie old fender twin with 2 x 8 ohm speakers). the customer wants a specific speaker type. you find 16ohm versions but no 8 ohm variants available...

[eschertron]

simple scenario, which I gather many of you have encountered..... customer brings an amp in for repair.... you find the amp is fine.... the speaker has blown and the OT on the amp has 4 ohm tap only (ie old fender twin with 2 x 8 ohm speakers). the customer wants a specific speaker type. you find 16ohm versions but no 8 ohm variants available...

I think R.G.'s post #7 intimates that a Greenback (for example) that has 8 and 16R taps will not sound like a Greenback with either. It will be sluggish (too much voice coil mass) or weak (too few turns) or a poor compromise that makes it both sluggish and weak compared to the optimized (original) version. So while a 8/16 speaker could be offered by the manufacturers, my sense is that the discriminating client who "wants a specific speaker..." won't have it.