Axiom Home Page Forums General Discussion Home Theater How to use the SPL meter properly?

Ok, I have the original Avia and spl meter from radio shack. I have it at slow and C setting and 75db. So basically I set each speaker to 0db on my prepro and turn the master volume up till I reach 75db. Then I set the db for each speaker so it all reads 75db without messing with master volume. But I'm confused on one thing....the sub. The sub is set on 0db on the prepro also and I'm not sure if I'm supposed to adjust the db or just turn the volume on the sub itself to 75db and keep the prepro 0db on sub? I'm guessing to mess with volume on sub and then use the pre/pro for diff sources such as DTS, cd, Dolby Digital, etc? Am I right?

I think its best to set your sub at 0db on your prepro and adjust the volume knob on the back of the sub to 75db.

This makes it easier to pump up your sub +5 if you want, or turn it down -5 with the prepro, and you know where you are, because "0" is 75db.

This is just what I did, right now I run my sub +5db, so all my speakers are calibrated for 75db, my sub runs in at around 80db.

Eric, within broad limits it doesn't matter which of the controls relating to sub level that you adjust to reach the calibration level. That being said, neither of the controls should wind up very close to either their maximum or minimum settings after calibration. In particular, the sub trim on the receiver(prepro)shouldn't be near its minimum since that might not put out enough voltage to keep some subs active. As was already pointed out, if future small adjustments were to be made to sub level, it's more convenient to do that on the remote rather than on the back of the sub; so to allow for that it would be a good idea to have the control not too far from its middle position after calibration so that there's +/- space.

Ok, that makes sense. You guys are great help.

I can really add nothing to the great responses you've already received, but JohnK makes an excellent point.

Setting the sub is a balancing act between the Receiver's sub level and the sub gain level. John's point about achieving that balance is important. At first, I had some trouble with my sub not wanting to flip on until the music was loud, and reverted to just leaving it on all the time. After one evening of calibration trial and error, I realized I had the sub gain too high and the receiver gain too low, which means (just as John says) that the signal was too low going to the sub and it would shut down thinking no signal was present. Readjusting that balance fixed the auto-off/on problem for me. So my advice would be to keep the receiver's sub level close to 0, and adjust the sub gain appropriately to get your calibration where you want it. That gives you the greatest flexibility in 'couch tuning' certain tracks or movies.

One minor point, it's not uncommon to run the sub a few db 'hot' over the rest of the system. With speakers calibrated at 75db, I, like Hutzal, like the sub to be at about 79-80db, as that presents the best balance in sound (for me, in my room).

I had a problem when I set my sub to 0 dB on my receiver and then adjusted the gain on the sub to level it at 75 dB with the SLP meter. I have an Outlaw sub and I noticed that many times the sub wouldn't awaken from auto-on even though I was watching a heavy bass scene my Lord of the Rings, for example. Outlaw tech support suggested that the reciever should be set at +3 to +4 dB's to that there is enough of a signal to wake up the sub from auto-on. Then just adjust the gain on the sub so that you have 75 dB on your SLP meter. This took care of the problem. He also mentioned not to go past +5 or so on the receiver gain or your sub might start clipping.

- Nick

My rotel pre/pro goes from -10 to +10 and I have it set at 0 for the sub and the sub volume at 7 o'clock position to achieve 80db and other speakers at 75db using Avia. Now everything blends better. Stay tuned for pics of the system tonight. Right now its movie time!!!