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Centred mono signal appears to the left

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Re: Centred mono signal appears to the left

Postby James Perrett » Thu Jan 14, 2021 10:52 pm

One thing that I happens here is that if I put something on the desk in front and below one of the speakers the stereo imaging degrades massively. The whole area around the speakers including the desk needs to be symmetrical for a decent stereo image.
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Re: Centred mono signal appears to the left

Postby CS70 » Thu Jan 14, 2021 10:57 pm

jellyjim wrote:I downloaded a sound level meter app for my iPhone and created a 440hz sine wave test tone in Audacity and measured same distance from each monitor (about 10cm) and got 74.9 vs 76.2 Instantaneous level dB(A).

A significant difference or negligible? They certainly sound the same up close and if I sit back in my normal monitoring position I get the same left bias as the bass lick in the song I was working on.


Hard to say - the phone microphone can be a bit of a lottery when measuring SPL but since you've used the same phone, same position and sample, I'd say it's a small difference - you notice 1dBA in focused mixing situations, but hardly for a sine wave.

And yet you have the skewedness... assuming you've checked cables and all, you could try rotating the speaker on its axis. Also, are you positive they are on the same horizontal level? What happens if you move a bit on the side? And no reflecting surfaces (such as screens) between them and your ears? Are the monitors directly on the desk? Are they oriented towards you (i.e. angled) or towards the back wall? Do you experience the same at all levels, or only when the music is loud?

What could be happening is that the reflections produce a frequency shift in the summed sound exactly where you are most sensitive. In my setup, I have massive cylindrical traps just behind the speakers, and absorbers around. Are other people perceiving the same thing?
Desk reflections can also be very powerful if the monitors are on the desk, in my set up they are just on the border of the baffle and high up so not much of the sound bounces to my ears.

A quick test can be to move the table and speakers someplace else in the room, 1 or 1.5 meters would do. You can also angle them a bit towards the ceiling (using books or something on the front) to see if it's the desk. If you a pic of the setup, could be worth to post it.



I did make a video with my iPhone to try and illustrate the sound in my room and weirdly the bias wasn't evident so I exported the audio from the clip to look at the waveforms ... and realised the iPhone records in mono! :headbang:

Hehe been there!
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Re: Centred mono signal appears to the left

Postby Hugh Robjohns » Fri Jan 15, 2021 12:10 am

jellyjim wrote:... a 440hz sine wave test tone in Audacity and measured same distance from each monitor (about 10cm) and got 74.9 vs 76.2 Instantaneous level dB(A).

A significant difference or negligible?

Negligible. Probably pure measurement tolerances. An inter-channel level difference of about 16dB is needed to move a sound image fully left or right, 8db is about half-left or right... So 1.3dB difference will create an off-centred image when auditioned in good conditions, but It would only be slightly off-centre. Your description sounded rather more dramatic than that... Implying a local acoustics issue, rather than a signal path issue.
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Re: Centred mono signal appears to the left

Postby blinddrew » Fri Jan 15, 2021 12:13 am

When i briefly had all my rockwool slabs on one side of the desk i had a 6dB difference in perceived level at the midpoint.
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Re: Centred mono signal appears to the left

Postby adrian_k » Fri Jan 15, 2021 8:05 am

James Perrett wrote:One thing that I happens here is that if I put something on the desk in front and below one of the speakers the stereo imaging degrades massively. The whole area around the speakers including the desk needs to be symmetrical for a decent stereo image.

This. I have symmetrical clutter on my desk, twice as much as I need, to ensure a good image. I’m not joking.
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Re: Centred mono signal appears to the left

Postby Zukan » Fri Jan 15, 2021 10:00 am

I haven't read all the responses so forgiveth if I repeat....have you tested the volumes are the same for both monitors?
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Re: Centred mono signal appears to the left

Postby CS70 » Fri Jan 15, 2021 10:18 am

adrian_k wrote:This. I have symmetrical clutter on my desk, twice as much as I need, to ensure a good image. I’m not joking.

There's people who actually put absorbent material on the desk :)

A pair of short desktop stands usually do the trick, together with having them towards the edge of the table.

This page gives some good hints: https://www.thomann.de/blog/en/8-tips-g ... -monitors/
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Re: Centred mono signal appears to the left

Postby jellyjim » Fri Jan 15, 2021 10:42 am

Zukan wrote:I haven't read all the responses so forgiveth if I repeat....have you tested the volumes are the same for both monitors?

You do, but bless you Zukan, your contributions are always welcome.

They don't have volumes as they're fancy software-driven mathingyamies driven by electrickery and general witchcraft

The software confirms they're at matching volumes.

We've decided

1. It's room acoustics
2. Good stereo imaging is hard
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Re: Centred mono signal appears to the left

Postby Zukan » Fri Jan 15, 2021 12:43 pm

Jelly, I wonder if Room EQ Wizard might help here? At least it will plot the room's response and maybe shed some light....
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Re: Centred mono signal appears to the left

Postby jellyjim » Sun Jan 17, 2021 10:50 am

Zukan wrote:Jelly, I wonder if Room EQ Wizard might help here? At least it will plot the room's response and maybe shed some light....

Is the correct solution when I haven't just moved studio rooms and everything is arse over tit! :D

A right pan of 13 on my master bus seems to have placed my bass where I expect it to be and, for now, is my #amateurhour solution :headbang:
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