Author Topic: Calibrating a subwoofer + set up  (Read 12465 times)

Online petetherock

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Calibrating a subwoofer + set up
« on: December 07, 2006, 11:39 »
Since we concluded the MO for SVS subs, some bros have asked me for advice on setup so I will start a new thread with some tips:

And for those living near AMK, I have some time during the pre- CNY end Jan period to help out, so long as I get a ride to and from your home.

get a proper demo disc with bass
ask around for the DTS / THX demo discs
be flexi - the best position may not be one your wife likes!
get an assistant to move the sub
be mindful of room nodes and room treatment

A v useful excerpt:


"Excerpt from "UNDERSTANDING SURROUND SOUND - 5.1 And Beyond..." writen by Mark Techer, July 2000
SYSTEM CALIBRATION.

AUDIO ADJUSTMENTS.

A well designed controller will have a few standard items. Apart from different surround sound decoding algorithms, your audio processor should have level trims for all channels including the FRONT LEFT and FRONT RIGHT.

For those systems that do not, you will need to find the level where the Left channel that reads +75dB and remember or mark the master volume at that point. That number will your 00dB level, even though it may not be close to 00dB.

Also, not all volumes display in relative (negative dB figures), some display in “absolute” (number that increase with the loudness). If your system is such, then choose a “round” number and then adjust each channel trim to read +75dB on the meter.

The worst case scenario will be a unit that does not offer either trims on the front left and right channels or a master volume displayed in absolute values…

In this digital age, usually both the trims and the master volume control will be digital and the trims should be in half dB adjustments. Full dB adjustments are too course and may not allow total precision.

All well designed decoders will also have an internal noise generator. The tone emitted from the noise generator will be equivalent to an audio tone recorded at –30dBFS for film sound (18BIT) which is the same as 105dB – 30dB or +75dB. Using a Sound Pressure Level meter and these tones, you will be able to precisely adjust the acoustic output level of your system to equal that of a cinema or dubbing stage.

The end result will be that you will hear the sound track they way it was heard in the studio that created it both from channel to channel sound as well as absolute volume level.

The SPL meter should have an analog display. The use of the analog model is preferred as reading can be under 1dB and depending on the type of level trim on your system, totally accurate.

The radio shack SPL meter is the same type used by the film industry. Independent tests revealed that this meter was the most accurate model from a group of meters tested including more expensive models.

The new meter from JAYCAR is more expensive, but it has a calibrate feature. Whilst this meter is digital, it does display in 1/10th of a dB.

USING THE METER.

The meter has a rotating “range” dial and two switches. The range dial provides the SPL range you would like to measure in decibels starting form 60dB to 120dB. There is also a battery check “BATT” position just next to the “OFF” position.

The two switches are labeled “WEIGHTING” and “RESPONSE”. Set the “WEIGHTING” switch to the “C” position and the “RESPONSE” switch to the “SLOW” position.

Set the dial to the 70dB range. This will now allow you to read SPL from 60dB to 76dB.

EDIT: Position the meter in the prime listening position.

Hold the meter at arms length from the body. The meter should be at seated ear height, pointed up and slightly forward.

DO NOT POINT THE METER AT ANY ONE SPEAKER.

I use a tripod to hold the meter and move well away so that reflections from my body are not read by the meter and give false readings.

Activate the test tone generator on your surround sound processor. Well designed processors will default to a 0dB reference level position regardless of the actual volume position and start at the LEFT front channel.

Observe the level reading. It should be reading at +75dB/C/SLOW. If the audio level is too high, the meter’s needle will “peg” and you will have to reduce the trim level for that channel to read the desired +75dB/C/SLOW. If the audio level is too low, adjust the trim to read the correct level.

PEGGING OF THE NEEDLE IS NOT ADVISED AND MAY ACTUALLY DAMAGE THE METER.

Once you are satisfied with the level, proceed to the next channel, working in turn around the room.

SUBWOOFER AND LFE LEVEL.

While the standard level for all main channels (including the Surrounds) is +75dB/C/SLOW, setting the level for both the subwoofer and the LFE channel is a little more complex.

Ideally you would use a Real Time Spectrum Analyzer. The level of the Subwoofer can be set with the SPL meter by the following method. The level of the Subwoofer should also read +75dB on the meter, however the tone for the Subwoofer is a “Warble” and the level will very along with the frequency. It will be difficult to set the level at the 70dB range.

Turn the dial to the 80dB range. If your processor has a Sub test warble, adjust the trim to read an average of +79dB/C/SLOW with the lowest part reading at –5dB on the 80dB scale. The level difference will be around just 4dB and is equivalent to the average level of +10dB when using the RTA.

DO NOT SET THE SUBWOOFER TO READ 10 DECIBELS HIGHER THAN A MAIN CHANNEL WITH THE SPL METER.

The LFE channel is a fixed value in reference to the subwoofer level. That is if you increase the Subwoofer level, you will also increase the level of the LFE channel. Some decoders offer a separate trim for the LFE channel. It should be set to the same level as the Subwoofer. If the SUB trim is 0dB, then so is the LFE trim.

THE LFE TRIM WILL NOT GO ABOVE 0 REF DECIBELS. IF THE LEVEL IS NOT HIGH ENOUGH AT THE 0 REF DECIBEL LEVEL, INCREASE THE GAIN ON THE SUBWOOFER WHERE POSSIBLE.

PLAYBACK.

Once your system has been calibrated, you can enjoy a film. The 0dB reference level is the level you should watch films at. You may of course reduce this level if it is too loud.

DIALNORM may be seen on some format decoders. It is a part if the Dolby Digital coding and will advise you of the average level of dialogue in a program. If the DIALNORM reads a plus figure EG “DIALNORM +4”, you must reduce the level of the master volume by 4dB. When used correctly, you will find that the level of dialogue remains consistent across a wide range of program material. The peak levels however will vary occasionally resulting in some very high Sound Pressure Levels. "

Enjoy your films and music… "
Please post instead of sending a pm, so more can learn.

My gear:
https://peteswrite.blogspot.com/2020/02/my-setup-22020.html


Offline Quest

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Re: Calibrating a subwoofer + set up
« Reply #2 on: December 07, 2006, 12:11 »
so much to read.  >:(
i ask you over and check for me easier la. :P when can i set appointment
do you know how to use PEQ or a BFD?

actually my main problems are:
1. integrating sub with main speakers. now i just do pure stereo and only on sub for movies. bass is just overwhelming for music if i on the sub, and my crossover (lowest 100hz on AVR) somehow may not be low enuf. can still get some perception of bass from sub. dunno how to set 2 modes for movie and music (BFD?)

2. somehow my speakers dun sound right in my new room. even my visitors said so.. it sound not so life-like as my previous setup. i think its partially cos of the front wall reflection and the fact that im seated nearer, but want to get 2nd opinion before doing anything.

i got SPL meter, Avia, DVD essentials and probably jag's disc somewhere. also got an unused BFD lying around. hehe

Online petetherock

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Re: Calibrating a subwoofer + set up
« Reply #3 on: December 07, 2006, 12:18 »
Sure, anything for my neighbour :)
Call me in Jan, when the SVS is 'seasoned'

Its not easy in an apartment, PEQ no issue, no experience with the BFD though

Have a floor plan ready, tape measure and a medium sized mirror (wah I sould like that Ghost hunter from those HK shows ....)

I accept payment in AMK mee pok, kway chap from Sembawang or Ampang Yong tau foo.... he he

another good link:

http://www.bigpicturebigsound.com/printer_560.shtml
Please post instead of sending a pm, so more can learn.

My gear:
https://peteswrite.blogspot.com/2020/02/my-setup-22020.html

Online petetherock

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Please post instead of sending a pm, so more can learn.

My gear:
https://peteswrite.blogspot.com/2020/02/my-setup-22020.html

Offline Darthfunk

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Re: Calibrating a subwoofer + set up
« Reply #5 on: December 07, 2006, 12:36 »
Sure, anything for my neighbour :)
Call me in Jan, when the SVS is 'seasoned'

Its not easy in an apartment, PEQ no issue, no experience with the BFD though

Have a floor plan ready, tape measure and a medium sized mirror (wah I sould like that Ghost hunter from those HK shows ....)

I accept payment in AMK mee pok, kway chap from Sembawang or Ampang Yong tau foo.... he he

another good link:

http://www.bigpicturebigsound.com/printer_560.shtml


Yo Pete i can always buy you Ampang Yong Tau Foo at Katong if you dont mind coming down to Marine Terrace  ;D

Offline civicguy

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Re: Calibrating a subwoofer + set up
« Reply #6 on: December 07, 2006, 15:05 »
my house coffee shop the mixed rice store quite good..

used to have 2 mei mei working in the coffee shop for last few weeks.. very cute too  ;D ;D

Offline Darthfunk

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Re: Calibrating a subwoofer + set up
« Reply #7 on: December 07, 2006, 15:19 »
Marine Parade woo, the distance can be measured on an international map - the YTF better be good, pm me in late Jan.
in the mean time, I expect you to memorise all the articles - test will be conducted pre- setup  ;D

On second tots, laksa might be better than Katong YTF....

Wah need to take test somemore lol. Think you will be very familiar with the set up especially the speakers since you had listen it at your friends place. Btw, dont be shock by how tiny my place is (rented studio apartment) Iam like using half the hall 2.5m x 3.5 for my HT  :-[

haha the laksa at Kotong is indeed good if you had tried before. Actually there are lots of good food at the area, I can even bring you to the famous wanton noodle at Joo chiat.

Offline Quest

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Re: Calibrating a subwoofer + set up
« Reply #8 on: December 07, 2006, 15:36 »
Wah need to take test somemore lol. Think you will be very familiar with the set up especially the speakers since you had listen it at your friends place. Btw, dont be shock by how tiny my place is (rented studio apartment) Iam like using half the hall 2.5m x 3.5 for my HT  :-[
no big deal. my HT area is also that small. only for me + 1 person to enjoy. :)

Online petetherock

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Re: Calibrating a subwoofer + set up
« Reply #9 on: December 17, 2006, 05:20 »
Found another good link, only one page or so:
http://www.audiophilia.com/hardware/spl.htm

Yes Wanton, Laksa and Nasi Lemak all accepted :)
Please post instead of sending a pm, so more can learn.

My gear:
https://peteswrite.blogspot.com/2020/02/my-setup-22020.html

Offline ALERT

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Re: Calibrating a subwoofer anf speakers using Avia
« Reply #10 on: April 18, 2008, 17:23 »
Using Avia calibration DVD and right speaker(FR) as reference. I adjusted my receiver’s FR volume = 00. Adjusted receiver’s master volume till SPL reads 85db for FR.

I completed adjusting all my speakers to output 85db using the Avia’s test tone. Now I’m having problem adjusting my subwoofer level.

As some of you may know, Avia’s subwoofer setup test consist of alternating high and low frequency band of pink noise between main speaker and sub. Thus the test tones keep switching between the “FL and SW”, “LCR and SW”, “FR and SW” …and so on. We need to adjust the channel level till the alternating noise bands reads the same on the SPL
(i.e 70db suggested by Avia).

Following the instructions by Avia:
1) Set SPL range to 70db, C weighting, Slow response.
2) I use right channel (FR) as reference and adjusted master volume till SPL reads 70db
3) Run subwoofer test tone in sequence “FL and SW”, “LCR and SW”, “FR and SW” …and so on.
4) Try to make adjustment to my receiver’s SW level till the alternating noise bands reads the same on the SPL

My SPL meter reading are as follows:
FL = 70db, SW = 67db-71db
LCR = 70db, SW = 64db-67db
FR = 70db, SW = 63db-66db
SL = 70db, SW = 67db-71db
SR = 70db, SW = 63db-66b

From the reading, I can’t seem to adjust all channels to the same level especially for  “FR and SW”, “SR and SW” test tones. Is this normal ??? Have I done it correctly ???

Please help  :-[

Online petetherock

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Re: Calibrating a subwoofer + set up
« Reply #11 on: April 18, 2008, 22:43 »
Alert,
Which sub do you have?
To achieve the SPL you desire you can use the volume for the sub in the amp, plus the gain on the sub itself.
Are you trying to acheive the same SPL for all channels and the sub at all frequencies. Thats not easy unless you have a ruler flat frequency response, which tough.

After all the tweaking in my room, I still have a suckout at 28-32Hz that is 10-15 db down from the rest.
Please post instead of sending a pm, so more can learn.

My gear:
https://peteswrite.blogspot.com/2020/02/my-setup-22020.html

Offline Jag

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Re: Calibrating a subwoofer + set up
« Reply #12 on: April 18, 2008, 22:55 »
Seems your Lefts (both front and surrounds) are reinforced by 4dB in both of them.

I recommend in this case, just calibrate yout sub to the center speaker. This is because a significant portion of movie audio comes from the center, and calibrating to center makes more sense.

Since the SL and FL can't seem to behave (I bet the shape of your room's left is not symmetrically same with the right), dun worry if you can't get it to be perfect. Yours is not the only case, so its normal.

Electronics : Denon 7200, MiniDSP Dirac 88A, Emotiva XPA-5 Gen2
ATMOS Audio : Martin Logan Ethos (L&R), ML Motif X(C), ML Motion 4 (14pcs surround spkrs)
LFE : Dual Rythmik FV25HP & Crowson Motion Actuator
Video : Sony VPL-HW55ES, Stewart Screen Studiotek 1.3
Source : HTPC
Fully automated HT via Alexa, Z-wave and Logitech Harmony Remote Control

Online petetherock

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Re: Calibrating a subwoofer + set up
« Reply #13 on: April 18, 2008, 23:01 »
Yep Jag the pro has spoken!
A diagram might help, Jason also mentioned in my room, the right side gives more bass than the left, and the rear corner produces the most of all the positions.
Please post instead of sending a pm, so more can learn.

My gear:
https://peteswrite.blogspot.com/2020/02/my-setup-22020.html

Offline Jag

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Re: Calibrating a subwoofer + set up
« Reply #14 on: April 18, 2008, 23:02 »
Alert,
Which sub do you have?
To achieve the SPL you desire you can use the volume for the sub in the amp, plus the gain on the sub itself.
Are you trying to acheive the same SPL for all channels and the sub at all frequencies. Thats not easy unless you have a ruler flat frequency response, which tough.

After all the tweaking in my room, I still have a suckout at 28-32Hz that is 10-15 db down from the rest.


Just to add, ruler flat frequency response, althou possible to achieve, does not sound great. A few years back, I had a few forumers come over to my place to listen how ruler flat sounds like...... all of them didn't like what it sounded like.

IMO, its more crucial to get the LCRs to conform towards the "X-curve"........ Next, the subwoofer to be spliced in smoothly with the mains.

Mains


Sub:


Combined:


Electronics : Denon 7200, MiniDSP Dirac 88A, Emotiva XPA-5 Gen2
ATMOS Audio : Martin Logan Ethos (L&R), ML Motif X(C), ML Motion 4 (14pcs surround spkrs)
LFE : Dual Rythmik FV25HP & Crowson Motion Actuator
Video : Sony VPL-HW55ES, Stewart Screen Studiotek 1.3
Source : HTPC
Fully automated HT via Alexa, Z-wave and Logitech Harmony Remote Control

 

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