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calibrating speakers - problems!

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thorne
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thorne posted on Sun, May 4 2014 12:31 PM

I decided to calibrate my speakers properly using an SPL meter

The technical guide states that I should set the meter for each speaker at 65db positioning it at the listening position

 

So in the speaker level setting, I attempted to do this, but cannot achieve anything like that level even with the speakers up to their maximum of 6db

 

However, the guide specifically states I should adjust the volume and not the speaker level for each speaker but I should do this in the speaker level option.  So I am a little confused.  Is the level different to the volume, and if so how do I get to alter the volume, rather than the level?

 

Hoping someone can help!

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thorne
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Me again, are there any calibration experts out there?  I'd love to do this properly. Hope I have explained my problem properly

thorne
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Me again, are there any calibration experts out there?  I'd love to do this properly. Hope I have explained my problem properly

Jeff
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Jeff replied on Sun, May 4 2014 4:52 PM

Well, I've never calibrated a B&O surround setup but have done more proletarian systems many times over the years. The traditional approach is to use pink noise sent to one of the speakers at a time (this still leaves subwoofer setup which is a bit harder). The instructions I've seen all say use 85 db as the signal level to make sure you swamp out any small amount of room noise. Use an spl meter, set to slow response, C weighting. Move from speaker to speaker, you will have to eyeball the 85 db setting a bit, as due to the random nature of pink noise the meter will bounce around a bit, which is why you use slow response. If you choose fast response on the meter you'll never balance it as it will bounce around rapidly, slow response evens that out a bit.

Interestingly, B&O has not incorporated the more modern calibration approaches as they believe you will have a dealer to it for you, and therefore don't need to spend the money in the product design to add this capability. Cheaper receivers for AV know you will likely buy them either mail order or from a big box store and will be on your own, and many include a mic and automatic calibration software that works really well most of the time. But you usually use it once only unless you move the system.

Jeff

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thorne
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Thanks for that. Yes, my dealer did it through guesswork, not an SPL.  The B&O manual definitely days 65db, and that I should not point the meter at each speaker but point the microphone to the ceiling at the listening point, and I am not getting anywhere near 65db, more like high fifties, even when I crank up the speaker to its maximum setting of +6db.  So I am doing something wrong

 

As I said, the manual says I should adjust the speaker volume and makes a big point of that not being the same as the speaker level.  I don't understand the difference at all.  Maybe that's where I am going wrong

Jeff
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Jeff replied on Sun, May 4 2014 5:52 PM

Definitely aim at the ceiling, that's right. To get to 65 db you have to use the main system volume, your regular volume control, to get there. I'd start by setting all the speakers to the zero position of their + and - 6 db trim range, then use your main volume, the one you use to control the volume when you're listening to music or watching TV, to ramp up say one of the main speakers to 65 db. Then go speaker to speaker and use the trim volume controls to adjust each speaker until it's 65 db. That's where you're going wrong, you set the main system volume first, speaker volume, then use the speaker level controls to fine tune each speaker as you go from speaker to speaker using the noise generator.You have to get the whole system loud enough to hit 65 db, then calibrate each individual speaker using the trim or level controls.

Your dealer should never, ever attempt to set this by ear, it can't be done. The human ear is just not accurate enough.

Hope this helps!

Jeff

I'm afraid I'm recovering from the BeoVirus. Sad

Beobuddy
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Start by setting the adjustments to default.

By entering the speaker level menu, use the centerspeaker as reference. When the white noise is heard at the centrespeaker, use the volume to adjust it to 65 dB. Then manually switch to the other channels and use the levelsettings to adjust them also at 65 dB.

thorne
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Brilliant!  Thank you so much, that's really helpful.  I'll try that tonight

Geoff Martin
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Hi,

I wrote the Technical Audio Guide - so it's my fault that you're confused. My apologies. Here's what you should do, Step-by-step...

1. Place the SPL meter in the listening position. Arrange it so that the microphone is pointing skywards (or ceiling-wards, if you're indoors...). Set it to "C" weighting and "Slow" response.

2. Go to the Speaker Level menu on the V1 or BV11 (or BeoSystem4) and select one of the loudspeakers to start with (I usually start with the Centre Front speaker - but this is arbitrary.

3. Set its Speaker Level to 0 dB.

4. Adjust the master volume of the system so that the reading on the SPL meter is 65 dB (or 70 - it doesn't matter what the actual number is, so long as its high enough to be sure that the noise reading is the result of the sound coming from your loudspeaker and not other background noise sources) We'll assume that it's 65 for this discussion. Also note that it's normal for the SPL meter to vary a bit. You can consider that the value should average around 65 dB SPL - but it'll probably vary plus/minus a couple of dB in the real world.

5. Once the master volume has been set to achieve this value on the SPL meter, never touch it again through this process.

6. Select another loudspeaker so it's making the noise. Check the SPL meter. Change the SPEAKER LEVEL so that the SPL meter reads 65 again. Since your SPL meter is set to SLOW response, you might want to wait a while for it to settle - so don't do this quicker than the SPL meter can respond.

7. Repeat step 6 with each of your loudspeakers. This is true whether they're main loudspeakers or subwoofers. They should all read the same value on a C-weighted SPL meter. (This is slightly abnormal when compared to the way other companies tell you do do things, but this is because the V1/BV11/BS4 have pre-weighted noise characteristics that compensate for the C-weighting on your SPL meter to make things easier for you.)

8. When you've done all the loudspeakers, it's good to just go around again and make sure that each is still giving you the 65 dB SPL reading.

9. It might be wise, once you've checked everything, to turn down the volume again before exiting the menu page. This is optional...

10. Exit the menu page and you're done!

 

Please feel free to ask if any of this is unclear.

Cheers

-geoff

Geoff Martin
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Hi Jeff,

Jeff:

he instructions I've seen all say use 85 db as the signal level to make sure you swamp out any small amount of room noise. Use an spl meter, set to slow response, C weighting.

In the film industry, the standard is to calibrate each loudspeaker so that -20 dB FS full-band pink noise results in 85 dB SPL at the mixing position. However, this is not only calibrating the relative loudspeakers' levels - but also their absolute levels to ensure that all theatres are reproducing at the same level as the re-recording studio. (in theory, at least).
In the case of a home system, the absolute level is irrelevant, since customers use the volume knob, of course... In addition, most persons' homes do not have the low-end rumble of the HVAC system in a cinema, so 85 dB SPL is unnecessarily high. 65 or 70 should be high enough to be adequately louder than residential traffic noise, for example.

The system we designed in the V1/BV11/BS4 is intended to produce the same results as the industry-standard calibration techniques - with a simpler procedure. This is primarily done via a pre-weighting of the noise signals to make a C-weighted SPL meter easier to use (see my previous response in this thread...)

Cheers

-geoff

Geoff Martin
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Jeff:

Your dealer should never, ever attempt to set this by ear, it can't be done. The human ear is just not accurate enough.

 

Hi again,

Sorry - I have to disagree with you on this one. A listening experiment done at both B&O and Nokia (same experiment in two places) proved that a "normal" person can calibrate the levels of 5 main loudspeakers in an ITU-775 configuration to within 0.5 dB of each other. See this paper for some details. This is one paper in a series that addresses issues in this ballpark - the whole series is worth reading if you want to dig into this.

Of course, subwoofers are different.

Cheers

-geoff

thorne
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thorne replied on Mon, May 5 2014 12:42 PM

Hi Geoff

 

Wow, never thought the author of the guide would respond!  Thanks a lot.  And, you have now made things extremely clear.  Very grateful

Jeff
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Jeff replied on Mon, May 5 2014 5:05 PM

Geoff Martin:

Jeff:

Your dealer should never, ever attempt to set this by ear, it can't be done. The human ear is just not accurate enough.

 

Hi again,

Sorry - I have to disagree with you on this one. A listening experiment done at both B&O and Nokia (same experiment in two places) proved that a "normal" person can calibrate the levels of 5 main loudspeakers in an ITU-775 configuration to within 0.5 dB of each other. See this paper for some details. This is one paper in a series that addresses issues in this ballpark - the whole series is worth reading if you want to dig into this.

Of course, subwoofers are different.

Cheers

-geoff

Interesting, thanks for the reference. I am astounded though that a human ear can get within .5 db on anything. Back a few years ago I used to setup surround systems for people, and I never found one setup by the person, no matter how they assured me that they'd done it well without a meter, to anywhere near 0.5 db.

Similar to why I went with 85 dB, yeah it was loud, but homes, at least in the areas I lived and went around doing this, had all manner of noise, airplanes, traffic, etc. that made 65 problematic.

But yeah, it was loud. Ish. Stick out tongue

 

Jeff

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thorne
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thorne replied on Tue, May 6 2014 12:48 PM

Hello again Geoff

 

As you were so helpful with the calibration issue, I wonder if you might be able to help with 2 other issues which have been taxing my brain!

 

1. I have 5.1 surround system, and the dealer has set up only one speaker group, called TV.  But it seems to me that I also need an audio group for playing CDs on my 9000, whereby the centre speakers rate not used, but only left and right front, left and right surround, and the subwoofer.  Is this easy to do?  Unless, of course, the system is clever enough to detect when music is being played and adjusts the centre speakers accordingly.  Hence the question.

 

1. When I had a 7 TV and Apple TV, I liked the TV screen to be blank when playing music.  If I used P. mute, the screen would go blank and the TV would revert to standby position. With the 11, the screen does go blank, but the TV stays where it is.  Is this as it should be?  And how does Apple TV fit in with my issue in 1. above?

Millemissen
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I am not Geoff, and I - indeed - would like to read his answer.

 

Since this is an 'issue' that is relevant to many BV11 (and V1/BV12..) owners here are my ten cents.

The system is not 'clever enough' - I think, because it is not wanted so anymore. I miss that!!!

There probably are several reason why it is so - maybe Geoff will explain that?

 

You have to/can make up to 9 'Speakers Groups' and you can choose these via the Beo4 or via the onscreen menu.

If your dealer has only made one group installing your tv, he has been too busy getting the job done Sad

He should at least have made one more (for music), and have explained how to.

BUT, you can read about it in the users guide - it is actually quite easy.

 

As for now you can't even expect that this (music) group then is detected, when playing a music (stereo) source.

However I would advice you to hesitate a bit - because with the very soon arriving SW-update it will be made possible

to assign a 'Speakers Group' to each source - on your own choice.

That will make things a bit easier, I guess.

In the SW-update there also will be an 'Auto-P.Mute' function (after 30 sec), when playing an audio source.

Whether the 'stand position' can be assigned to these new 'Speakers Group' possibilities or not, I don't know?

But very soon you will be able to test that yourself. (I can't - my V1 has no motor function).

 

The AppleTV could then be assigned (I guess) to any of the 'Speakers Group's you have created - but only to one!

You should pick the one, you use the most - e.g. if you mostly AirPlay music, you could choose the group with both front speakers.

Many people like the double-stereo for music - so it would be that group instead.

And you would have to 'manually' choose another group, when watching video content over the ATV.

 

Probably Geoff can explain that all with fewer and clearer words than I can - we'll see if he does Smile

 

MM

 

There is a tv - and there is a BV.

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