Measuring max SPL

burdette

If I want to measure a "max" SPL, or even check the level of my usual "loud" setting, what source material do I use? I don't imagine I'd use a test tone.. a movie or music and just sort of eye an average?

Also.. what settings on the meter. As a reminder, what were the settings for subwoofer frequency response check?

Thanks.

HBombToo

This issue has been a source of confusion for me while trying to set my system up. By default in my system the dvd player is the standard using the avia disk at 85dB spl. Now while watching 5.1 material from direct TV there is a big difference in SPL with the dvd player plus it even changes from channel to channel. I have even noticed changes from dvd ---> dvd on the mix which has been discussed here. All these variances make the whole reference game a flaming pain in the Arss!... but instead of resetting everything all the time I just use the volume control and put is as loud as the wife will permit which is around 75dB SPL.

I also bought a VU meter that I hooked up prior to going on vacation so that I voltage levels hitting my sub amp. It is amazing when I first hooked it up and ran back through the avia cal then put on 2 channel the reduction in SPL or Voltage. The processor change in the h/k varies on the preamp stage a lot and I'm not really sure that should be the case. I think the h/k just is not cutting it but it is serving its purpose for now.

HBomb

rs159

His question wasn't calibration, he wanted to know how to get his max spl.

That's probably a dangerous thing to do, considering you would have to get to the limits of the system, which could include burning the voice coil or hitting the xmax or clipping. This is something I've been wondering how to safely do, too. Anybody?

HBombToo

Originally posted by burdette
what source material do I use? I don't imagine I'd use a test tone.. a movie or music and just sort of eye an average?

Also.. what settings on the meter. As a reminder, what were the settings for subwoofer frequency response check?

Thanks.

I believe we were talking about source material and measurements rs??? Furthermore, to eliminate confusion regarding source material I suggested the avia disk... and through in a little of my own thoughts so be cool.

Also when trying to achieve the speakers true max you probably want to eliminate the room response so you can put the speaker on your driveway or something like that...

HBomb

rs159

Ah yes, I should read posts more carefully.

Sorry

Dr. Spec

I use the SPL meter mounted on a tripod at my feet about 2-3 feet in the air, facing forward on C-weighted fast.

Invariably SPL peaks are bass peaks - no two ways about it - bass moves the most air and creates the most pressure.

I keep a spreadsheet of the DVD, the Master Volume setting, the "hottest" scene with a time stamp, and the peak SPL.

In my room, I limit my sub to "around" 112-113 dB peaks on the hottest scenes. This limit is derived from cautious increases in volume with a sixth sense of when I am nearing its safe limits. I have never bottomed it, but I do keep the SS filter set to 20 Hz which helps greatly.

Also be aware there is a big difference between generating 112-113 dB peaks in the 25 Hz range vs. the same SPL at 40-45 Hz. The scenes that give me peak SPL might be largely ignored by lesser subs - like the "ring drop" in LOTR-FOTR opener.

My SPL meter is also a far sight better than the RS meter most people use. It is faster to react, and is more accurate on the C-weighted scale, especially below 30 Hz. In fact at 15 Hz, it reads 8 dB higher than the RS meter.

Just some food for thought when working up to and documenting the safe limits of your sub.

Doc

GuitarheadCA

I've Heard a ton of stuff about SPL meters and test discs, but have never tried it on my system and I'm starting to think I should. Doc (or anyone else)- where did you get your SPL meter? Where else(besides RS) can you get them- how much should I expect to pay?

Also, I'm under the Impression that AVIA makes one of the better test and calibration discs. Any Comment?

Thanks in advance,
Peter

HBombToo

I use the avia and the RS spl analog meter and both are fine? total package should run about $80.00???

HBomb

Dr. Spec

If I didn't have the good fortune of having full time access to a B&K meter, I'd be soldiering on with the RS meter like everyone else. You don't want to know what a pro-grade SPL meter costs - the RS meter is a STEAL for $35 - buy it without hesitation.

They are both c-weighted, but the B&K follows the c-weighted curve far more faithfully than the RS model. Compared to the B&K, the RS model is down 3-4 dB at 20 Hz and it gets worse below that - over 10 dB down at 10 Hz.

As long as you use the commonly available correction factors for the RS model (which incidentally are a combination of meter error correction and the theoretical unweighted correction), you should be OK if you will be using the meter for plotting FR sweeps.

CFs for the B&K meter are just the theoretical "c-weighted to unweighted" CFs.

I have the Avia disc, and I like it very much for A/V calibration.

Doc

burdette

I'm not interested in pushing ANYTHING in my system to the edge of its theoretical limits. I've no qualms about saying that while my inexpensive receiver works wonderfully for our needs right now (and, frankly, has decently respectable numbers), I know that it does not have the reserves or clean high power as more costly amps. I don't intend to push it until either it or a speaker *almost* fries.

I just want a bar-room SPL number so I have an idea of what I've got and what my system can do. I can *easily* turn up both music and movies to levels that are beyond comfortable for my ears, with no distortion. I don't do that, however. Which brings me back to my question about measuring 'average' SPL.... to get an idea of what SPL I'm at when my system sounds LOUD to me, what sort of source material to use to check that, and how you interpret the readings on the meter as an 'average' SPL. You can find information on the dB levels of a "loud" rock concert, for example. Well, when they measure that.. how/what are they measuring??

Again, I don't care what the max SPL either my sub or system is capable of.. I want to know the SPL of what I consider LOUD.

Thanks for the information and replies.. and for any additional replies.

faster100

It really matters if you measure it with material you like, not something you don't.. Say you put in heavy metal to test it, sure it may be louder with distortion but does it really matter what spl it hits if you really listen to say classical music.. I would put in material you like and crank it to what you think is good clean and clear and measure it with an spl meter.. simple.. if you indeed don't want a max spl, but a max that is comfortable with your music/movies then that is the way to achieve it i think.. just my .02 cents..

Dr. Spec

For average SPL's set the meter to c-weighted slow and place it near your head and watch the needle. It will hang at the average SPL during sustained periods of music.

Low to mid 90's is pretty loud for me - probably averaging a few watts steady.

Doc

Tour2ma

Agree with Doc, continuous 90 db is loud, even 80+ "grows" loud with time. But in transients, either music or movies, even 100db is enjotable...

Stravinsky's "Firebird"... Great dynamics. Nice "symphonic" listening level with 60 to 80 db in the final movement hitting 106 in the crescendos and a fairly sustained 110 in the final bars...

Reminds me Doc, I still owe you the 2nd half of my list... This one's the complete ballet, not the Suite, on London 414 409-2 from Charles Dutoit and the Montreal Symphony, 1986. Just a gorgeous recording.

Dr. Spec

Thanks, tour. I'm getting into SACD, and will be ordering cables and the discs over time. The SACD format looks better than DVD-A to me from a sonic and selection standpoint.

But I will still appreciate good old 2 channel orchestral whenever I get the chance. My ex took almost my entire classical collection and I still haven't busted a move on replacement, but this SACD phenom is the catalyst.

Ain't this hobby grand?

Doc