How to Solve High-Frequency Suckout in Room?

@theaudiomaniac I think you might be right, in terms of AC voltage output being close enough. That said, there is a 1.2% variance at 5,000Hz, and close to a 1% variance around this frequency. While small, wouldn’t that be audible

@djones51 , I think the voltage output should be sufficient to compare the differences (without needing to convert to power which should give the same readings. Unless, of course, you are thinking there might be differences in the resistance between left and right and I should measure that too? As I said the problem was evident to a lesser degree on my old speakers, and I also tried swapping the speakers with each other and the problem remained on the right.

I highly doubt testing with the speakers connected will show much difference (but I will try later today). This is because I won’t be able to play the 1kHz tone at the same volume as I did without connecting the speakers, and therefore I am guessing there will be an even smaller difference between left and eighth channels.

I did read an old forum post that indicated that subtle differences may not be detectable using a voltmeter. The ultimate test is to use a dual channel oscilloscope, inverting one of the channels phases, then using the “sum” function of the scope. Because you’ve inverted one of the phases, the channels should cancel out each other when you sum them, and any variance from 0V that the scope shows would indicate an imbalance. I used to have an oscilloscope that hooked up to your PC but it’s so old it won’t work anymore.

Thinking my next step could be to rent a dual channel oscilloscope.

And, I’m going to book a frequency response hearing test just to totally rule that out! Although my wife also detected the problem without being told exactly what the issue was first.

I will also try to measure the frequency response playing the test tones, 1m from each speaker playing one side at a time.

Finally, I will also try rotating my entire system 90 degrees in my room.  Just as one final “room test”.  This will require me to dismantle my couch again so might be a while…

I do have a good relationship with my local dealer who I did not buy my amp from.  I could potentially ask them to borrow one of their high end Moon amps for troubleshooting.  I’ve tested Moon gear before and I found their stuff to be very highly resolving, so if the issue is not present with a Moon integrated, I’d think that would prove definitively that my amp is at fault.

The things we do for our hobby!

@theaudiomaniac I think you might be right, in terms of AC voltage output being close enough. That said, there is a 1.2% variance at 5,000Hz, and close to a 1% variance around this frequency. While small, wouldn’t that be audible

That is at best 0.1db. Left to right, your system could be off 3,4,5 or more db. It will not be audible.

I did read an old forum post that indicated that subtle differences may not be detectable using a voltmeter. The ultimate test is to use a dual channel oscilloscope, inverting one of the channels phases, then using the “sum” function of the scope. Because you’ve inverted one of the phases, the channels should cancel out each other when you sum them, and any variance from 0V that the scope shows would indicate an imbalance. I used to have an oscilloscope that hooked up to your PC but it’s so old it won’t work anymore.

Don’t waste your time. A wide bandwidth multimeter is accurate enough. The difference in time between measurements and thermal differences are smaller than what you are measuring. It is your room. Didn't you already say you swapped channels and the issue is still there? That rules out the electronics.

What you need to do is figure out how to measure room response. There are many resources on the web. It will cost you $100-200. If you have a noticeable difference, then then it will be easy to see them. Measure with one speaker, measure with the other, then compare.

@theaudiomaniac , I swapped the cables at the amp end (only) and the problem changes from the right side being too soft in the upper mids and into the treble, to the left side being too soft in these frequencies. This leads me to believe it’s not the room.

That said I am planning to completely rotate my system in the room as a test (setting up my system against the side wall.

Update: I have also questioned if the source material is causing the issue since the problem is not apparent on all music, mildly apparent in some music, and blatantly obvious in other tracks. As above, vocals sound centered but the upper end of vocals seem more fleshed out on whichever speaker is NOT being driven by the amp’s right channel.

So it's not the room, it's somewhere in your system.  Further swapping and substitution of cables/channels will reveal where it is.  Proceed by using logic and focus on one component at a time.

Yes, for tonight I plan to:

1) Try my old Clarus Crimson Biwire cables which I’ve not sold yet. More out of curiosity as they are less resolving than the Valhalla 2’s (but very good still), so I may or may not hear the issue with these cables

2) Resurrect my old Arcam CD player to see if the problem goes away. If it does go away the problem must be the DAC module in my amp. That said it was a $700 CD player that I bought 25 years ago for $500 so again it’s possible the issue may be present but not audible, comparing against a $5,000 DAC module.

3) Resurrect my old Arcam A85 integrated amp and see if the problem is detectable with it. Again, a lower end amp so I may not be able to hear the issue if it exists. Turns out it accepts spades after all (I had thought it needed bananas).

So far, with 1-3 above, if I AM able to detect the issues still with these tests, it would suggest that either my room or hearing ARE in fact to blame. If I can’t hear the issue it doesn’t necessarily mean anything as it may be that this low end gear “hides” the issue by not being as resolving.

4) I will try the voltage comparison between left and right, when playing a 1KHz test tone, this time with my speakers connected. Will also try at 5kHz where the voltage was the most varied (7mV). Not expecting to see any difference playing at a reasonable volume, since I expect the difference to be even smaller at the lower volume of this test, vs the test I did last night at a higher volume. But maybe adding the speaker load will change things.

5) I will try the 1kHz and 5kHz test tones using a frequency analyzer app on my phone, 1m away from the speaker and 1M from the ground, one speaker at a time.

6) Might save this for another night but I will completely reconfigure my system and living room to be in a different orientation in the room.

If after all of this I’m left at square 1, I will either:

1) See if my local dealer will lend me a high end integrated for a day (probably would be Moon or McIntosh), even though I didn’t buy my amp here, or

2) Bring my amp to my local dealer (who again I didn’t purchase the amp from), or

3) Bring my amp to the dealer I bought it from, which is in a different city, to listen to other high end speakers to see if the issue manifests. I actually prefer the first two options as this particular dealer WAY overdampens their rooms to the point it sounds like an anechoic chamber. I sense all sorts of frequency removal happening whenever I test speakers there.