Best audio perfomance from 8Ω or 16Ω loaded compression drivers?

[1audiohack]

For the last month or so I have been hell bent on quantifying the differences I hear from the different diaphragm materials and driver designs of the two inch throat variety. I think if I can hear it, I should be able to measure it, please note that I said should.

The current test pile consists of 2441's, 2445's, 2446's and 2450's with D16R2441's, D8R2445's, D16R2445's, D8R2450SL's and Truextent Be4008"s 8Ω.

I have extensively measured all of the possible combinations with the exception of the Be's in the 2441's and some patterns are emerging from the data that agree with my ears.

What I don't have is 8 and 16Ω versions of all of the diaphragms. It has been pointed out to me that most all of the really good / high end / top shelf drivers are 16Ω. If that is indeed the case then I must wonder why?

I have always bought the 8Ω versions (for home use) as I like to keep the amps as small as possible (with adequate head room of course) eliminating excess gain to keep the noise floor as low as possible, half the impedance, half the required drive voltage.

Following this logic, or lack of it, my question is this, is there a real sonic benefit to the 16Ω variety? Theoretical sonic advantages? Unless I buy a bunch more diaphragms, I am unable to answer this question for myself. Who would really know?

Thank you,
Barry.

[Robh3606]

It has been pointed out to me that most all of the really good / high end / top shelf drivers are 16Ω.

What would those be?? What's the imp. value for the 435Be, 045Be and the 476Be? If the impedance is the issue then throat diameter is a moot point. The main difference is the wire gage used and the number of turns to keep things simple. Why would more turns of lighter gage wire guarantee you sonic superiority all other parameters being the same??

Rob

[Mr. Widget]

Until recently almost all JBL compression drivers were rated as 16 ohms. Isn't the 476Be a 16 ohm driver? I know that all TADs are 16 ohms... my guess would be that the prevalence of 16 ohms is of a historical nature as opposed to one of performance, but that is just a wild assed guess.


Widget

[Eaulive]

On a purely mathematical point of view, higher resistance for a given reactance decreases the Q factor, so there maybe a softer impedance curve... with a given crossover it could lead to a flatter response.

Anyways, what do I know...

[pos]

there was a thread on this topic on diyaudio recently:
http://www.diyaudio.com/forums/multi...-vs-16ohm.html

I have always bought the 8Ω versions (for home use) as I like to keep the amps as small as possible (with adequate head room of course) eliminating excess gain to keep the noise floor as low as possible, half the impedance, half the required drive voltage.

You can look at it the other way around:
- with 16 ohms you get 3dB more S/N from a given amp
- with 16 ohms you get twice the damping factor from a given amp (not really important for a tweeter I guess...)
- with 16 ohms the protection cap value is divided by two (-> lower price or better quality, especially if charge coupled)

of course you loose 3dB of headroom from your amp, but its power supply will be less stressed, and I cannot see any decent commercial solid state amp that would not be powerful enough to power a compression driver to ear splitting levels at home.

I have extensively measured all of the possible combinations with the exception of the Be's in the 2441's and some patterns are emerging from the data that agree with my ears.

Please tell us more!

[yggdrasil]

16Ohm impedance represents an easier load for the amplifier than 8Ohm, giving the possibility of lower distortion, and/or the use of a simpler amplifier construction.

Given a very simple amplifer(e.g. SET), you will get better results by matching the amplifier bias to the represented driver / horn impedance.

[Eaulive]

- with 16 ohms you get 3dB more S/N from a given amp
----------------------------------------------------
of course you loose 3dB of headroom from your amp,

So at the end you're back to square 1

[4313B]

Isn't the 476Be a 16 ohm driver?

Yes.

[pos]

So at the end you're back to square 1

You have 3dB less noise when connecting the driver without signal (input shorted), which is good for home use

[Eaulive]

You have 3dB less noise when connecting the driver without signal (input shorted), which is good for home use

Yes, but ony because you get half the power from a given voltage, so the amplifier will arrive faster to clipping for the same SPL.
All in all the dynamic range is the same, you could arrive to the same result by padding the driver

[1audiohack]

there was a thread on this topic on diyaudio recently:
http://www.diyaudio.com/forums/multi...-vs-16ohm.html


Please tell us more!

I tried to glean what I could from that thread, thank you for that link. One thing of interest was the coments about Neo, I see something that puzzles me in the 2450 driver that I think is magnet related and I will follow up on it.

If and when I believe I have something conclusive to share I will be sure to share it. The last thing I want to do is possibly mislead anyone with incorrect information. At this point I think I need to purchase a pair of 16 Ohm Truextent diaphragms and keep on digging. I know it's a big puzzle, but I have now in place (at least for me) a couple more pieces.

Thank you for sharing guys,
Barry.

[pos]

Yes, but ony because you get half the power from a given voltage, so the amplifier will arrive faster to clipping for the same SPL.
All in all the dynamic range is the same, you could arrive to the same result by padding the driver

The residual noise (in volt) will generate less acoustical noise, which is very important when driving the driver directly from an amp. If you use a lpad you also loose power (real power this time, in heat) and you lower the apparent damping factor for the driver (but how cares for a compression driver...).

[Eaulive]

The residual noise (in volt) will generate less acoustical noise, which is very important when driving the driver directly from an amp. If you use a lpad you also loose power (real power this time, in heat) and you lower the apparent damping factor for the driver (but how cares for a compression driver...).

Resistors are a common component in crossovers, of course they eat power, but all in all, I don't think it was the reason behind having compression drivers at 16 ohms instead of 8.

I'm not even sure there's a real reason,

[JeffW]

I tried to glean what I could from that thread, thank you for that link. One thing of interest was the coments about Neo, I see something that puzzles me in the 2450 driver that I think is magnet related and I will follow up on it.

I didn't see anything about neo magnets in that mess, but I kind of glossed over a bunch of it . You have 2446 and 2450 drivers, aren't they about the same except for the magnet? I hope it's not neo=bad, all my drivers are neo

[1audiohack]

I don't want to wade through all of that thread again, what I thought was implied was that (most?) Neo drivers skimp on the magnet because Neo is ??? Not all of that threads discussion was centered around compression drivers. But I see a ghost in the 2450 that is likely unimportant, I just want to know what it is.