Imaging Issue – Center Image Pulled to the Left

[OCA]

Hi folks,


Lately, I’ve been noticing a significant shift in the soundstage of my stereo system—specifically, voices and some instruments in the upper-mids and low treble range are clearly pulling to the left of center.


This happens regardless of whether I’m using Dirac correction or not. For context, I’m using an Arcam SA30 driving a pair of Dynaudio Special Forty speakers. I haven’t made any major changes to the room or speaker positioning. The only recent addition is a turntable placed in the cabinet about 30–40 cm behind the speaker baffles. I considered whether the plastic dust cover might be introducing some reflections, but it seems unlikely to cause such a noticeable shift. In fact removing such dust cover does not solve the issue.


I initially suspected an issue with the right speaker and swapped the L/R channels, but the imbalance remained unchanged. I’ve also ruled out hearing issues, as the soundstage is perfectly centered when listening through headphones.


At this point, the only remaining suspect would be the amplifier, but it seems unlikely that a subtle fault would only affect imaging without other symptoms.


To investigate further, I ran a set of measurements using a UMIK-1 mic and REW. I captured each channel separately and then both together, with and without Dirac correction. While I’m no REW expert, I didn’t see dramatic differences in SPL between the channels. Phase alignment isn’t perfect but not wildly off either. The only significant difference I noted is in RT60 around 100 Hz.


Here’s a link to the REW measurements: https://drive.google.com/file/d/13g-9AqNKMySv3sKYinfRd_X18M-BSces/view?usp=sharing


If anyone is willing to take a look and share their thoughts, I’d greatly appreciate it!



Thanks!

Even the tightly windowed excess phase differences between left and right speaker show a major shift at 60Hz. It could be electrical if you are in the US.

 

[gianluca_v]

Even the tightly windowed excess phase differences between left and right speaker show a major shift at 60Hz. It could be electrical if you are in the US.

View attachment 461316

Could you please elaborate a little bit on that?

 

[OCA]

Could you please elaborate a little bit on that?

Hard to elaborate much else, you haven't measured with timing reference and full range and the weird peak around 12kHz says you have moved the mic direction between left and right speaker measurements as well. Proper measurements is a must to get decent results especially with major boundary asymmetries between speakers as in your case.. But if all else is assumed ok a very wild guess could be 60Hz ground loop affecting only one of your speakers!

 

[gianluca_v]

Hard to elaborate much else, you haven't measured with timing reference and full range and the weird peak around 12kHz says you have moved the mic direction between left and right speaker measurements as well. Proper measurements is a must to get decent results especially with major boundary asymmetries between speakers as in your case.. But if all else is assumed ok a very wild guess could be 60Hz ground loop affecting only one of your speakers!

I dont know what you mean by "measuring with timing reference and full range" but I swear the mic was not moved by an inch throughout the entire process. Anyway thanks for looking intorno that.

 

[gianluca_v]

Just a quick update. I noticed that the shift to the left becomes more noticeable after 10-15 minutes of listening. This might explain why the measurements do not reveal much (the amp does not warm up much to play few sweep tones). I know that some amps have an internal thermal sensor that adjust bias of the mosfet based on the measured temperature to keep tonal balance consistent all the time. I dont know whether my arcam sa30 has it too but at this point it seems pretty clear that something is negatively impacting the gain of right channel as amp gets hot. Does this make sense to any of you ?

 

[Count Arthur]

Just a quick update. I noticed that the shift to the left becomes more noticeable after 10-15 minutes of listening. This might explain why the measurements do not reveal much (the amp does not warm up much to play few sweep tones). I know that some amps have an internal thermal sensor that adjust bias of the mosfet based on the measured temperature to keep tonal balance consistent all the time. I dont know whether my arcam sa30 has it too but at this point it seems pretty clear that something is negatively impacting the gain of right channel as amp gets hot. Does this make sense to any of you ?

It could be that something has gone out of spec, however, I'm not an electronics engineer, so hopefully someone more knowledgeable can wade in on that.

In the meantime, do you have a different amplifier you could try out to see if the issue persists? Maybe borrow one.

 

[OCA]

Just a quick update. I noticed that the shift to the left becomes more noticeable after 10-15 minutes of listening. This might explain why the measurements do not reveal much (the amp does not warm up much to play few sweep tones). I know that some amps have an internal thermal sensor that adjust bias of the mosfet based on the measured temperature to keep tonal balance consistent all the time. I dont know whether my arcam sa30 has it too but at this point it seems pretty clear that something is negatively impacting the gain of right channel as amp gets hot. Does this make sense to any of you ?

It does to me. I had a Naim Supernait 2 amp and I could swear center image would shift to the left after a certain period of listening. I don't have a technical explanation for that though.

 

[Keith_W]

Just a quick update. I noticed that the shift to the left becomes more noticeable after 10-15 minutes of listening. This might explain why the measurements do not reveal much (the amp does not warm up much to play few sweep tones). I know that some amps have an internal thermal sensor that adjust bias of the mosfet based on the measured temperature to keep tonal balance consistent all the time. I dont know whether my arcam sa30 has it too but at this point it seems pretty clear that something is negatively impacting the gain of right channel as amp gets hot. Does this make sense to any of you ?

It could be the amp, it could be the speakers. You could try playing pink noise for 15 minutes and then take a measurement.

 

[gianluca_v]

It could be the amp, it could be the speakers. You could try playing pink noise for 15 minutes and then take a measurement.

No the speakers and cables are fine, I switched left and right of both and problem persisted. Ill try to find another amplifier to do a/b testing to confirm this hyphotesis. Alas it is out of warranty

 

[A Surfer]

I would be curious if the experimenting with speaker toe in as suggested earlier has been tried.

 

[gianluca_v]

I would be curious if the experimenting with speaker toe in as suggested earlier has been tried.

Yes of course I tried and did not solve anything. I even went beyond and moved the entire system in another room with perfect simmetry. Nothing changed. No definitely there must be something wrong with amplifier. But it is really strange because issue is not present when using headphones through the very same amp (and if im not mistaken arcam sa30 does not have a dedicated headphone amp but uses the same module that drives speakers. It is also a relatively new devices: only 3 years and up until a couple of months ago it was perfect

 

[PeterNL]

Looks like oxidation of the output relay contacts.

 

[SteveC]

Don't forget that your ears also play a role in this. It's entirely possible that something has caused some damage to an ear. Might want to test for this, either DIY or going to an audiologist.

 

[gianluca_v]

Don't forget that your ears also play a role in this. It's entirely possible that something has caused some damage to an ear. Might want to test for this, either DIY or going to an audiologist.

I went last week to an audiologist as I was start thinking that if I could not find any fault with my system maybe I was the fault Both ears are perfectly clean and the audimetric test did not reveal any asymmetry between the two ears.

 

[A Surfer]

Seems like you've exhausted almost every conceivable explanation other than there being some kind of issue with the amplifier. Seems like an extremely odd fault though. So specific and divorced from anything obvious.

It will be great to finally learn what the issue is when you do finally find out.

 

[Daverz]

The change as the amp heats up seems pretty definitive to me.

An easy test of the amp is to swap both input cables L to R and speaker cables L to R at their ends.

If I might make a comment irrelevant to the problem at hand, I don't like the way Dirac has your in-room response tilting up between 200 Hz and 10 kHz. It should tilt down. (1/1 octave smoothed response below).

 

[Duke]

An easy test of the amp is to swap both input cables L to R and speaker cables L to R at their ends.

^^This^^ will tell you whether it's the amp.

If it's not the amp, have you tried draping a thick blanket over anything to the left of the centerline (even if it's between the speakers) that could possibly be causing a reflection or diffraction? This includes vertical edges, like the vertical corner of a cabinet.

 

[Scytales]

Lately, I’ve been noticing a significant shift in the soundstage of my stereo system—specifically, voices and some instruments in the upper-mids and low treble range are clearly pulling to the left of center.


This happens regardless of whether I’m using Dirac correction or not. For context, I’m using an Arcam SA30 driving a pair of Dynaudio Special Forty speakers. I haven’t made any major changes to the room or speaker positioning. The only recent addition is a turntable placed in the cabinet about 30–40 cm behind the speaker baffles.

I guess if the only other change is the turntable then maybe try removing it entirely to see if the problem goes away?

Have you given a try to kemmler3D suggestion?

 

[Arindal]

No the speakers and cables are fine, I switched left and right of both and problem persisted.

Did you swap solely the amplifier channels to check if the problem still persists, or is it flipping to the other side in this case?

If any hardware problem can be ruled out (speaker, amplifier), I would further narrow down potential issues by deactivating room correction (at least above 250 or 300Hz) and playing around with stereo triangle, listening distance and toe-in. If reflections or cancellation issues in the room are the root, you most likely during this procedure will come to a speaker placement with which this is disappearing (in many cases a pretty nearfield triangle with strong toe-in).

 

[pinger]

Are you sure its not different recordings than when the soundstage was centered?