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Stupid ? what does reference level do. (1 Viewer)

JohnWA

Auditioning
Joined
Jan 11, 2003
Messages
8
Vince,
I discovered the FAQ after I posted that msg. back in Jan. I've also read the zillion or so msgs you've written on the topic of Ref Level and the calibrating of a HT. I'm grateful for all the time you spend on this forum. You have helped a lot of us.
Unfortunately some of us are a little more dense than others. :) I still have a question about Sub output. I've read some conflicting things on the accuracy of a SPL meter w/r/t lower freqs. At the "couch" position, should you set the output of your sub the same way you set the other speakers? In other words, adjust the Sub lever to 75 or 85dB. (Depending on the source used.)
Thanks,
John
 

Lee Carbray

Second Unit
Joined
Oct 23, 2002
Messages
308
John, let me see if I can answer this and Vince you can correct me if I am wrong.

You are correct in setting you sub up to match the other speakers however the Rat Shack meter is reads about 3Db(I think)lower while reading low frequencies. Therefore to get the same level your meter should read 72 or 82 depending on the source used.

Of course for personal preference a lot of people set the LFE a few Db on the Hot side for more dramatic effect.
 

RobertR

Senior HTF Member
Joined
Dec 19, 1998
Messages
10,675
I had an experience tonight that showed me the source of a potential source of confusion when trying to determine how loud "reference" is. I calibrated to 75 dB using my AVM20's internal reference tones. When I did this, I noted that the volume was set at -23 dB. Therefore, I assumed that a volume setting of -23 dB was 10 dB below reference, and -13 dB was reference. I tried DVDs at this level, and I kept thinking "what's all the fuss about reference being loud? This doesn't sound that loud".

THEN I noticed that the level of the AVM20's test tones are at a fixed level that's INDEPENDENT of the volume setting. I needed to IGNORE it. I then used Avia (this time being careful NOT to use the internal tones) to calibrate, and discovered that reference was acheived at a volume setting of more like +1 dB, a full 14 dB louder than I thought it was! Guys, reference is L O U D!
 

Jeff Gatie

Senior HTF Member
Joined
Aug 19, 2002
Messages
6,531
RobertR,
I would calibrate to reference using Avia at a volume level of 0dB. Then it will be easier to remember;) . This is how I calibrated my Denon. Also, the output from your receiver test tones probably corresponds to a volume level of 0dB, so you can compare how "off" your test tones are. Plus, it just seems "right"!
 

RobertR

Senior HTF Member
Joined
Dec 19, 1998
Messages
10,675
Jeff,

Yes, that's essentially what I did. I now know that when my prepro's volume is at 0, I'm listening at reference level.
 

Edward J M

Senior HTF Member
Joined
Sep 22, 2002
Messages
2,031
My Denon also defaults to 00 on the Master Volume for Reference Level calibration. The individual channel levels are then adjusted up or down to get 75 dB for each speaker at the key listening position.

Since my HT room is only 1800 ft3 and my speakers are fairly efficient, the 00 setting actually gave me a bit more than 75 dB, so my settings all ended up slightly in the negative range, which is fine with me - I like running my pre-outs on the cool side to ensure there is no voltage distortion.

Regardless, 00 on my Denon IS Reference Level playback for DVDs. I prefer 10-15 clicks under Reference (i.e., -10 to -15 on the Master Volume) most of the time. This gives me 105-110 dB SPL bass peaks at the key listening position, depending on how hot the DVD is mastered, and how bass intensive it is.

And yes, the RS SPL meter typically reads 2 dB LOW on the subwoofer test tone, so you you need to ADD this amount to what the meter displays for the true SPL. There are a few websites that provide the RS correction factors for various bass frequencies.

Regards,

Ed
 

Vince Maskeeper

Senior HTF Member
Joined
Jan 18, 1999
Messages
6,500


Which do little but confuse people trying to use wideband pink. The correction values offer some idea at individual freq, but when used with a pink tone it doesn't tell you much about an overall correction (and even moreso, the acoustics of the room could interact with humps in the RS meter reading causing even more skewed results on a case-by-case basis).

-Vince
 

Edward J M

Senior HTF Member
Joined
Sep 22, 2002
Messages
2,031
Vince:
I use a 10-100 Hz 1/12 octave FR sweep with individual test tones that are each 10 seconds long. I manually plot the results in Excel and evaluate the FR in that manner. The long tone gives the meter time to stabilize and each one is an individual frequency so the meter reads very steady.
The 1/12 octave resolution is fine enough to provide detail about the overall bass FR of the speaker, and room nulls and peaks are also readily apparent. This method of FR evaluation is a very useful tool in determining the effect of various filter points, sub/speaker placement.
Without question, the RS meter reads LOW in the bass frequencies. The correction factors must be added to the reading for the true SPL. It is about 2-3 dB low at 40 Hz, and as much as 7-8 dB low at 20 Hz.
Go here for more information:
http://www.hometheaterhifi.com/utili...load-page.html
I don't use the RS meter (I use a pro-grade B&K meter), but I do have a spread sheet which automatically adds the CF for each frequency if one is using that meter and manually plotting test tones.
Regards,
Ed
 

Vince Maskeeper

Senior HTF Member
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Jan 18, 1999
Messages
6,500


Indeed- no question. My point being- since the "variation" is all over the map at specific freq- it makes me wonder how far off the "average" ends up being when playing a standard pink noise tone for overall channel calibration.

Again- my sub calibration is very similar (I do a chart and use correction values for individual freq)-- but my point was to be careful on pointing out the correction chart, as the average HT guy trying to stumble his way through Avia will find the chart more confusing than helpful.

I'm just trying to figure out how far off the overall SPL is in bass when using pink noise wide freq-- since the amount the meter is "off" is quite different across the spectrum-- pink noise interacting with nulls and nodes measured by a meter that is more/less sensitive at specific freq-- well you can see the potential variation.

-Vince
 

Edward J M

Senior HTF Member
Joined
Sep 22, 2002
Messages
2,031
Vince:

I have had both my B&K (factory certified and recently calibrated) and a new RS model in my room side-by-side on tripods. I have compared them both for single frequencies and for the bass rumble tone generated by the AVR.

The rumble tone is tough, because it causes both meters to fluctuate, even on Slow. Nevertheless, the RS model reads about 2 dB lower than the B&K - on average - for this tone.

I'm not saying my B&K is an absolute - but it's a far sight better than the RS model in the accuracy department. And I can appreciate what you are saying about the complexities of this rumble tone vs. a single frequency. With that said, I don't think I'm steering anyone too far wrong when I tell them the RS meter reads about 2 dB low on the typical bass rumble calibration tone.

To get an even better answer, you would need some higher end stuff like an real time spectrum analyzer and associated software to see how far off the RS model really is.

Regards,

Ed
 

Brian L

Senior HTF Member
Joined
Jul 8, 1998
Messages
3,302
FWIW, the most stable test tones I have used are from the Bass Mekanix (spelling?) CD. It too has frequencies at 1/2 hertz increments. I use it with an Infinity Rabos meter.

I found that the the real contributing factor to getting stable readings was the tones, not the meter. Everything else I tried were way too wobbly to interpret.

YMMV.

BGL
 

Mike Up

Supporting Actor
Joined
Dec 16, 2002
Messages
657
Edward,

The rumble tone is tough, because it causes both meters to fluctuate, even on Slow. Nevertheless, the RS model reads about 2 dB lower than the B&K - on average - for this tone.
Funny, remember on the AVR-3803 post, where I sited I like the sub level 3db higher. Well, I use the new RS digital meter. I don't know if it is the same as the analog, but setting the sub level to equal the speaker level left the midbass to weak IMO. My speakers go to about 50Hz -3db and 40Hz ~ -8db. I have to turn the sub level 3db higher than the speakers to equal the midbass output of my speakers when they are run full range. Most music nowadays it's harder to hear, but with 80's heavy metal that only had upper midbass and no low bass, the impact differences were quite noticeable.

I would had thought the RS SPL Meter read 3db high, not low, then again I could be experiencing room response, where the sub is located.

Have a good one.
 

Edward J M

Senior HTF Member
Joined
Sep 22, 2002
Messages
2,031
I would had thought the RS SPL Meter read 3dB high, not low, then again I could be experiencing room response, where the sub is located.
Hi Mike - Clearly the pink noise rumble tone is more complex than a single tone. I think it was designed to be, because if a user has a null or a peak at a single frequency, it would throw the entire sub calibration off. Unless the user wants to take the time to do a 1/12 octave (or even finer resolution) FR sweep on the sub to actually see what the sub is doing, the "rumble" tone is a good yardstick for initial sub calibration.

Tone complexities aside, I think we can all agree that the individual frequencies that make up the rumble tone are all grouped in the bass region. And it is a well established fact the RS meter reads low on all bass frequencies below approximately 125 Hz. It would be logical to conclude the RS meter would also read low on the rumble tone, and my experience with that meter supports this conclusion. Again, the best way to tell would be with the much better spectrum analyzer, but I don't have one available to me.

Ed
 

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