2x250 W class D alternatives

[Deleted member 20765]

Has home audio switched over to having 4Ω speakers as the standard? It used to be home audio was 8Ω and car audio was 4Ω for the most part. Thou car subs often were "dual voice coil" and JL Audio had their dual 3Ω system.

Speakers have a highly variable impedance. My Revel f208 has two dips to 3.4 ohms, at 100Hz and 2.7kHz. Mostly, it wanders between 4 and 8 ohms. So it is difficult to say what the "impedance" of a speaker is since it is highly dependent on frequency. I use 6 ohms for my calculations since that appears to be a rough average value.

 

[Ropeburn]

Speakers have a highly variable impedance. My Revel f208 has two dips to 3.4 ohms, at 100Hz and 2.7kHz. Mostly, it wanders between 4 and 8 ohms. So it is difficult to say what the "impedance" of a speaker is since it is highly dependent on frequency. I use 6 ohms for my calculations since that appears to be a rough average value.

Meanwhile, technical conventions disagree. Nominally, your Revels are 3 Ohm speakers. But that category doesn't exist in sales departments, so...

 

[Deleted member 20765]

Meanwhile, technical conventions disagree. Nominally, your Revels are 3 Ohm speakers. But that category doesn't exist in sales departments, so...

How did you come up with 3 ohms impedance? Thanks!

 

[mhardy6647]

Obviously I am not @Ropeburn but here's what I see... (assuming this is the right loudspeaker?!?)

source: https://www.stereophile.com/content/revel-performa3-f208-loudspeaker-measurements

The nominal impedance would usually be taken in the region I circled above (which is, frankly, usually flatter than this loudspeaker's). It's clearly a bit less than 3 ohms, making it incrementally more amplifier hostile than a typical "nominal 4 ohm loudspeaker", but not sure I'd call it a 3 ohm loudspeaker.

@John Atkinson says:

The speaker's plots of impedance magnitude and electrical phase angle against frequency are shown in fig.1. The impedance ranges between 4 and 7 ohms for most of the audioband, though there are dips to 3.6 ohms at 100Hz and 3.2 or 3.7 ohms at 2.9kHz, depending on whether the HF control switch is set to its maximum or minimum, respectively. The phase angle is generally low, or high only when the impedance is also high, ameliorating its effect. However, the combination of 5 ohms and –50° at 25Hz means that the F208 will need to be driven by a good 4 ohm-rated amplifier. As Erick Lichte noted, the speaker worked better from his tube amplifier's 4 ohm than from its 8 ohm output.

 

[mhardy6647]

I note, wryly, that the whole domestic loudspeaker industry could go back to using "8 ohm" drivers and take this whole messy issue off the table.


PS My loudspeakers are of nominally 16 ohm impedance.

 

[mocenigo]

Obviously I am not @Ropeburn but here's what I see... (assuming this is the right loudspeaker?!?)
View attachment 444107
source: https://www.stereophile.com/content/revel-performa3-f208-loudspeaker-measurements

The nominal impedance would usually be taken in the region I circled above (which is, frankly, usually flatter than this loudspeaker's). It's clearly a bit less than 3 ohms, making it incrementally more amplifier hostile than a typical "nominal 4 ohm loudspeaker", but not sure I'd call it a 3 ohm loudspeaker.

@John Atkinson says:

To me it looks very close to 4ohm. 3.7ohm or something. It looks like a relatively comfortable load.

 

[Julf]

I note, wryly, that the whole domestic loudspeaker industry could go back to using "8 ohm" drivers and take this whole messy issue off the table.


PS My loudspeakers are of nominally 16 ohm impedance.

8 and 16 Ω made sense back in the bad old days of valve amps, with high voltages and low currents. Modern solid state amps have already mostly taken the issue off the table, except that some speaker manufacturers produce speakers that go to absurdly low impedance (below 2 Ω) and some amp manufacturers cut corners.

 

[mocenigo]

8 and 16 Ω made sense back in the bad old days of valve amps, with high voltages and low currents. Modern solid state amps have already mostly taken the issue off the table, except that some speaker manufacturers produce speakers that go to absurdly low impedance (below 2 Ω) and some amp manufacturers cut corners.

Using lower impedance drivers means smaller inductors in crossovers, and since these are the heaviest components, this saves space and weight. For the pro applications, having low impedance drivers allows more of them to be put in parallel. So, there are reasons for that.

But there is no reason for impedance of the final product to go under, say, 2.5ohm, except greed: a carefully designed crossover will keep impedance controlled both in modulus (from below but also from above) and argument. (The exception are some electrostatic speakers that are just designed that way.) it is not too difficult. With 8ohm drivers I have a crossover that does not go under 6ohm except at the highest frequencies where it stays above 5. So, a very easy load, even if everything thing were halved. And I am not a professional speaker designer!

As you said cost is a reason some amps cannot work if the impedance drops. Many small amps are BTL designs. But j would not call it “cutting corners”. It is called designing within a given budget. Nothing wrong with this, but the customer should pick an amp that is stable at low load impedance, if needed. This said, I do not want amps that are not stable at 2ohm, and I am ready to pay the price for that.

 

[mhardy6647]

except that some speaker manufacturers produce speakers that go to absurdly low impedance (below 2 Ω) and some amp manufacturers cut corners.

Yeah... "some"...
My point exactly.
It's senseless.

 

[Bleib]

What a great thing that Amir just reviewed one of the amps

3e audio A7/A7 Mono Amplifier Review

This is a review and detailed measurements of the A7 / "A7 Mono" stereo power amplifier with balanced inputs. It was sent to me by the company. I have no idea what it costs in US. Audiophonics lists it for 379,00 €tax incl. While the A7 may look like its competitors, it has a heft to it that I...

www.audiosciencereview.com

 

[erniek]

I have a Buckeye 252 and use this with a Wiim Ultra and KEF R3 speakers in a 12 x 12 room. I downsized to this from large PSB speakers, Odyssey amp and preamp with OPPO Dac and I will say that this sounds as good to me for a downgrade as I had in a larger system. Very happy with Wiim Ultra and Buckeye amp. I also am using a REL subwoofer in this setup.

 

[EJ3]

8 and 16 Ω made sense back in the bad old days of valve amps, with high voltages and low currents. Modern solid state amps have already mostly taken the issue off the table, except that some speaker manufacturers produce speakers that go to absurdly low impedance (below 2 Ω) and some amp manufacturers cut corners.

And when those 2 some'(s) get together, that cam spell SUM DISASTER!