Measuring FR of an Amp alone (w/o speaker) may not be accurate. Your thoughts?

[mhardy6647]

The Quad "ESL-57"
A capacitor that also made (beautiful) noise.

Interaction of QUAD 57 and 303

 

[Blumlein 88]

Quad ESL 63

Soundlab A1

 

[mhardy6647]

Quad ESL 63

Quad ESL-63 loudspeaker

Warning to Purists: Despite certain qualities about the ESL-63 speakers which you will probably like, Quad equipment is not designed primarily for audiophiles, but for serious-music (call that "classical") listeners who play records more for musical enjoyment than for the sound. Quad's...

www.stereophile.com

Pretty darned similar.
The 63 definitely had (has) some advantages over the '57.
For me, though, the big advantage of the ESL-57... is that I have a pair.



I do, for the record, have some aftermarket stands for them -- I got this pair sans their proper legs (well, I do actually have one). For the price, though, I cannot complain.

 

[Chr1]

So I think that this is what I would call sensible component matching... or "synchronicity" in audiophilia. And it makes sense. My main system is now a pair of Neumann KH310s and a pair of BK XXLS400FFs, all active, but my other gear is matched/paired due to the fact that it has variables that I have not been able to optimise with DSP/EQ only. Most probably due to speaker specifications/shortcomings.

I guess in the ideal world all speakers would measure perfectly and an amplifier would simply need to amplify. As I see it, this is unfortunately not usually the case and so there are plenty of speakers that need EQ and (for some people) the addition of valves can also sometimes make a significant subjective improvement.

Ho hum. Back to the old valves = good/bad thing, I guess.
However, why so damn binary.

Possibly wandering slightly off topic here however
... Sorry.

 

[mhardy6647]

I believe that audiophiles prefer the term synergy to describe that je ne c'est quoi when the source, amp, loudspeaker, cable, and fairy dust stars all align. Maybe they call it synchronicity when they're listening to the Police, though.

 

[Chr1]

Sorry, that'd be the afternoon Cabernet there.. Apologies.

Getting my audiophile terminology muddled.
Synchronicity is finding out that you use the same cable risers as Stings accountant surely.

Doh.

Or is that... da doo doo da, da doo doo da.

... Roxanne.

Ah hem. Apologies.

 

[mhardy6647]

^^^ Well played.

Mr. Sumner himself might even approve.

 

[dorakeg]

Krell FPB 350 mcx at about 5 watts into MartinLogan reQuest electrostatic hybrid here in the audiotorium:

The vertical scale is 1/10 dB and the impedance of the speaker drops severely at the high frequencies.

And Stereophile's measurement of the speaker impedance - not the same model, but the prior version, and should be representative.

The FR dips above follow the impedance dips below

View attachment 271641

Nice!! Thank you for the measurement!!

I have a question. The measurements were taken at 5w. What if it's 10w? Will everything increase by 3db (taking assumption of 2x power for every 3db increase) or increase will vary between different frequencies?

I am thinking that this variation in sound level may be one of the reason why people hear differences. Eg. On person mention some amps have more "punch". I think perhaps the amp is able to produce slightly higher sound level at low frequencies compared to others.

This also brings me to the part about sound level matching and this could explain why people hear differences despite them being level matched. Assuming we level match at 79.5db @ 1KHz. As the sound level across 20-20KHz is not flat, certain frequencies will be higher/lower depending on the amp. I would say at certain situations, these differences could be audible.

HAving said that, it is possible to use DSP to make them volume match at all frequencies. But that is meant to compensate for the differences instead of saying that there are no differences.

 

[RayDunzl]

I have a question. The measurements were taken at 5w. What if it's 10w? Will everything increase by 3db (taking assumption of 2x power for every 3db increase) or increase will vary between different frequencies?

5 watts is pretty loud for a sweep.

I do have the frequency response for a range of speaker outputs, though. If the amplifier was changing, other than output level, then so would the speaker.

I don't see it in these 24 sweeps:

Ambient room noise interferes with the low level low frequencies, and my room has a hole around 48Hz.

---

As for phase, the same situation.

Here, the three lowest level traces are removed as they didn't fit the pattern of the other 21 sweeps, also, likely noise related:

Distortion:

Measured distortion is dominated by noise until the the highest SPLs are reached, where the distortion measurement bottoms out then begins to rise a little.

Lowest SPL at the top, increasing toward the bottom trace.

The bold trace is the highest SPL, and measured distortion has just begun to rise out of the noise floor,

Conclusion:

No audible differences as the sweep levels are increased from very low to rather high. Hearing protection desired at the higher sweep levels.

 

[Head_Unit]

Mr. Sumner himself might even approve.

Pfffft, just a bell boy!

 

[Head_Unit]

When I introduced a Studio 530 into the mix and was measuring things electrically not acoustically, the PM-10 was superior to PM-11s2 in performance in terms of THD (how the load increases THD compared to a resistor) and consistency of the frequency response.

There's another thread here somewhere comparing THD of some expensive amps, and Stereophile measures that and other things. Different amps definitely do not measure the same. The question is do they sound different-I have mixed opinions, as I've sometimes swapped amps and heard a different sound (however not under blind conditions and hence unscientific). Then again there was this
https://forums.stevehoffman.tv/threads/denon-vs-parts-express-round-1.984507/
experience.
- What do you mean by "consistency of the frequency response"?

 

[dorakeg]

5 watts is pretty loud for a sweep.

I do have the frequency response for a range of speaker outputs, though. If the amplifier was changing, other than output level, then so would the speaker.

I don't see it in these 24 sweeps:

View attachment 271794



Ambient room noise interferes with the low level low frequencies, and my room has a hole around 48Hz.

---

As for phase, the same situation.

Here, the three lowest level traces are removed as they didn't fit the pattern of the other 21 sweeps, also, likely noise related:

View attachment 271796



Distortion:

Measured distortion is dominated by noise until the the highest SPLs are reached, where the distortion measurement bottoms out then begins to rise a little.

Lowest SPL at the top, increasing toward the bottom trace.

The bold trace is the highest SPL, and measured distortion has just begun to rise out of the noise floor,

View attachment 271802



Conclusion:

No audible differences as the sweep levels are increased from very low to rather high. Hearing protection desired at the higher sweep levels.

Thanks for the info!!

 

[Deleted member 48726]

Watching. (The watch thread button doesn't work for me).