Audyssey delays are off according to REW impulse measurements?

Croy9000

Registered
Thread Starter
Joined
May 3, 2022
Messages
6
After running Audyssey I am running into what I am not sure is an issue in REW or my methods. The overlay impulse graph is saying that the front LCRs are ~1ms (12in / 0.3m) closer than they should be. I am using the surround right as acoustic reference for all measurements. Also the 2 rear surrounds are saying they are 0.2ms (3in 8cm) closer than they should be. The reference itself is saying it's 0.03ms (0.5in) away, which seems like of all of them, that one should be very very close to zero.

I am running Audyssey MultEQ XT32 on my Denon an 11.1 system (with Dynamic EQ turned off for now). I am running REW 5.20.7 with a UMIK-1 with ASIO4ALL. The distance measurements Audyssey are setting are spot on when I check them. The signal path is very simple being Windows Laptop > HDMI 7.1 > Denon > Speakers.

Any ideas? Being new to this, I just want to make sure my setup (and expectations) are good before I learn more about REW for my sub riser project.


51451
 

John Mulcahy

REW Author
Joined
Apr 3, 2017
Messages
5,439
Looks normal. Hopefully the surround speaker isn't a type with multiple tweeters, as that could confuse things. The timing signal is a high frequency sweep, 5 kHz to 20 kHz, and may have slightly different arrival time to the full response of the speaker when measured, so the half inch delay for the ref isn't unusual. As an experiment you could change the ref to another speaker, e.g. front left, and remeasure the relative timing.
 

Croy9000

Registered
Thread Starter
Joined
May 3, 2022
Messages
6
Thanks for the quick response John. The speakers are Triad Silver LCR for fronts and all surrounds, so just a single tweeter.

Of the many things I have experimented with (and the result is always the above graph) is changing to reference to other speakers. The results are always the same (about 1ms difference between front and rear of theater). Always measuring from the same spot at the primary middle seated position.
 

John Mulcahy

REW Author
Joined
Apr 3, 2017
Messages
5,439
If you get the same relative timing with a different ref then those are the timings.
 

Croy9000

Registered
Thread Starter
Joined
May 3, 2022
Messages
6
Thanks John. Yeah I agree the results must be what they are if they are consistent between references. Sure seems to be pointing to Audyssey being off in its calculations of distance (at least in my feeble mind). I can start tweaking things with Denon delays, but not convinced this is a wise or productive thing to do.

My main goal is to ensure when I start tuning subs, I know I am getting accurate results.
 

John Mulcahy

REW Author
Joined
Apr 3, 2017
Messages
5,439
The differences are irrelevant for sub alignment. On a vaguely related note, this thread discusses a test that measures how high the timing difference between a bass drum and a high hat needs to be before it becomes audible.
 

Croy9000

Registered
Thread Starter
Joined
May 3, 2022
Messages
6
Figured I would share this in case it meant something. For the Left speaker, it compares the default delays Audyssey set, to an adjustment I made in the AVR to bring the Left delay into alignment to the reference Surround Right. The Left+SurRight is both speakers playing at the same time before the adjustment, and Left+SurRight (aligned) is after. I guess the notable thing is the general increased SPL of the aligned one.


51453
 

KMO

Registered
Joined
May 19, 2021
Messages
1
My AV System  
Preamp, Processor or Receiver
Denon AVR-4308
Front Speakers
KEF LS50 Meta
Center Channel Speaker
KEF LS50 Meta
Surround Speakers
KEF LS50 Meta
Surround Back Speakers
KEF HTS2001
Subwoofers
KEF KF92
So, we've dug into this deeper, and it seems that the issue of OP's poor alignment is down to Denon using 300m/s as their speed-of-sound constant for the speaker distance UI. If you use accurate distances, measured by tape or converting measured delays using 343m/s, you get inaccurate results like OP's.

Correcting by rescaling the measured distance to allow for this 14.3% difference greatly improves things, and some versions of Audyssey like MultEQ Pro and MultEQ-X seem to be aware of this, while others are not.

Details over AVS Forum threads that I can't link to due to insufficient posts:

"Audio / Audio Theory, Setup, and Chat / Audyssey time alignment is off according to REW impluse readings?"
and
"Audio / Receivers, Amps and Processors / Audyssey MultEQ-X

So no fault of REW, but it does one raise feature request.

Please can we configure the speed of sound to 300m/s to give us distance values we can enter directly into Denon AVRs? It seems that the preferences won't let me configure lower than 330m/s.

I would find this particularly useful for the time alignment tool - my last alignment showed a required delay change of -3.5ms, which I attempted by adding 1.2m as indicated, but it turns out that got me -4ms due to this issue, and I should have added 1.05m instead. Would be nice to have that shown directly in the UI.
 
Last edited:

John Mulcahy

REW Author
Joined
Apr 3, 2017
Messages
5,439
Must be chilly in their R&D labs, 300 m/s in air happens at about -49 C :)
I'll widen the range of accepted values in the next build.
 

sam_adams

Member
Joined
May 23, 2017
Messages
173
@John Mulcahy, points of reference for the discussions mentioned by @KMO:




John, one of the sticking points on the SOS value in the prefs is that if 'Distance units:' is set to 'feet', the displayed value is still listed in meteres. Can that be fixed to display properly based on selection?
 

John Mulcahy

REW Author
Joined
Apr 3, 2017
Messages
5,439
OK, I'll show the speed of sound preference setting in feet per second if the distance unit is set to feet.
 

Croy9000

Registered
Thread Starter
Joined
May 3, 2022
Messages
6
Awesome, thanks John. These changes will help a lot. Also thanks for the original help above. It kept the discovery process pointed in the right direction.
 

HD MOVIE SOURCE

Registered
Joined
Jun 23, 2021
Messages
2
My AV System  
Preamp, Processor or Receiver
Denon x6500h
Universal / Blu-ray / CD Player
Panasonic UB9000
Thank for this post and the links, makes a lot of sense. There are some really impressive people that got to the bottom of this, spreadsheets, calculations, all really impressive work.

As somebody on the AVS forum pointed out.

2.52m * (300/343) = 2.2m

Distance times Denon speed of sound divided by the real speed of sound and you get the real distance. Some have said that the MultiEQ-X app accounts for the error when sending the file to the receiver. I'm going to contact Audyssey and see if that is correct.

I think running 2 subs on Denon now, I'm just going to use one output, let MiniDSP and REW time-align it, and have my Denon just consider it one sub when it does its time alignment. I was doing half and half before, but using one sub out from the receiver just makes it much simpler.
 
Top Bottom