levels spl meter

[dholmes]

I use a RS spl meter, set all spks at 75 db. Do any of you cheat and go beyond 75? And I have a hard time setting the sub level, the needle jumps around a lot. I have a Denon 4800 Thanks

[Frank Z]

The RS meter, when set to 70db will have a range of measurement from 60-76db, when set at 80bd the range of measurement is 70-86db. If ref level on your equipment is 75db you are going to get better results by setting the meter to 80db because you are closer to the center of the range. Try using the higher setting and then set your sub level to around -3 to -5 db.

[danger boy]

set your RS spl meter to "C" weighted and slow.. it won't jump around so much that way. use a DVD set up disc like Avia or Sound and Vision running thru your DVD player.. I wouldn't use your receivers noise because it won't be accurate.

[goingganzo]

that is true i have tryed the recever befor. and it is not a constant volume it varies. some dvd has setups on them the thx ones.

[mantis]

If your sub is jumping all over the place,that just might mean you need to reposition it.Your getting peaks and dips.Some subs are unstable,some are really steady.
Over the years I have noticed many different subs doing what you claim,this is normal and fixable.
I could go on and on about how to fix the room problems your probably having.Here's the simple solution....if the sub is in the corner,pullit out some.Reflections are killing you I feel.Once you fool around with placement some,and the meter is still jumping around a bit,If your processor/receiver will allow you to stay on the sub test tone,take the average,whch should be where you set all other speakers.
I also have found the need to decrease the sub SPL as most of the time the sub has better dynamic range then the receiver does.2 to 4 db should do it.

[Dr. Spec]

The sub test tone fluctuates on the SPL meter because it is not a single frequency at a constant amplitude; it is a rumble tone consisting of several bass frequencies all at fluctuating amplitudes.

It has nothing to do with placement. All rumble tones fluctuate on the SPL meter regardless of the sub location.

The reason it is a rumble tone, is because if it was a single frequency, the user might have a room null or peak at that single frequency, and it would give a bogus reading.

Just the other day I was setting up a sub in a friend's room that had a 22 dB (!!) null at 56 Hz.

Using the rumble tone for general set-up is fine. Just take an average reading on C-Weighted Slow.

The RS meter reads about 2 dB low on the typical rumble tone. Because of this, most people get best results at around 76 dB (if you are using 75 dB for the other speaks). This will actually be around 3 dB on the hot side for the sub, which is satisfying for HT at all but the loudest playback.

If you are REALLY cranking it on playback, drop the rumble tone to 73 dB and that will get you even with the other speaks and prevent sub distortion or damage at high levels.

Finally, if you really want to see what your sub is doing, burn a disc with 1/12 octave test tones and run a sweep in the room and plot the results. Use the correction factors for the RS meter, which can be off quite a bit at very low frequencies.

This project is for more advanced users - if you just want to set-up your HT system, stick with the rumble tone and 76 dB average on the RS meter.

Doc

[scottvamp]

It has nothing to do with placement. All rumble tones fluctuate on the SPL meter regardless of the sub location.

Exactly!!!!

[danger boy]

FYI i really love that THX LFE test on some DVD's .. it goes so loowww. love hearing that..