Which SPL meter and how to use document?

Radio Shack

Radio Shack for sure. I like the digital- some like the analog.

Your AVR lets you set the distance from the listening position to each speaker in feet. Get a tape measure and do that if you have not already done so.

Your AVR has a built in test tone that you can use with the SPL meter. Read your manual for instructions on using the tone.

Position the SPL meter at your normal listening position, at ear level, with the silver microphone on the end pointed upward.

Turn it on, set it for C weighting. Select the 70 or 80 dB range.

Play the test tone.

Adjust the volume on the set until the spl meter reads 75dB.

Test each speaker in turn. The idea is to adjust the volume trim on each speaker until every speaker produces a 75dB reading at the listening position.

In the links below there is the company that makes the radioshack spl meters at 45% cheaper for the same unit ,
And the other link is a step by step how to on how to use the meter..


http://www.bswusa.com/proditem.asp?item=SLM100
http://www.audiophilia.com/hardware/spl.htm

With a htib all the values are set to a default value since their systems are limited to what comes in the box with the purchase you made ,
so the speakers are set to small and I guess sub 1,2,3 is the different crossover points in the system.

Trekguy,

I have a RS digital. The manual states to point the microphone at the sound source. What advantage, if any, is there in pointing it upward?

Doug

Your mic needs to be pointed up in the "Sweet Spot"since the listeners position is sitting up and not laying down ,so the theory is correct.

I'm guessing if trying to measure the SPL of a source like a jet engine you would need to point toward the engine.

With surround sound you are trying to measure multiple sources & everything I have ever read states to point the microphone straight up. This probably eliminates the variable of trying to point the mic accurately at each spkr.

While playing with your meter, why don't you try straight up & then compare to pointing to each spkr and see what, if any, differences you measure.

Mike

Mic forward or mic up? Here is what I understood is true.

We are most of us, measuring in a room small enough so that room effects are important. No matter what, we get both direct and reflected sound at the listening position. The advice to point the mic upward is try an get an equal measurement in all directions. I also suspect that prevents the user from standing just behind the mic and blocking reflected sound.

Does it make much difference? Maybe not. The microphone is not especially directional as far as I can tell. Sound waves bend around corners fairly well.

I just put it to the test. Sitting on the floor and holding the unit out and higher than my head. Using the built in test tones on my AVR the difference was not more than 1dB at the most. I actually think it was less because I have the digital version and it tends to flip between levels when the change is on the borderline.

Good try, trekguy, and I agree with your arguments.

Can I assume you used pink noise? I wonder what the results would be with a tripod (more stable than hand-held), with MLS or burst source and a more accurate mike. I've always used the straight up mike but I did get different spectral measurements on each channel with the mike aimed at each speaker.

rubs-re your last.

I am not clear exactly which Onkyo HT or receiver you have, and so I am not sure which on-line manual is yours. Perhaps you could look at http://onkyousa.com/download/own_man...m?cat=Receiver and http://onkyousa.com/download/own_man...fm?cat=Systems or some other site you find, and give me the url of the correct manual.

But if you are using the RC-581M remote the "Test" button starts the tone and just next to it, the "Ch SEL" button cycles the tone through each of the speakers.

If that works for you, run through it again, and then if we need to, we can take a look at the amount of trim. Try changing the subwoofer mode button if there is one; with program material this will increase or decrease the amount of bass.

Thanks Kal.

I was doing my best to think like a tripod! But the slight fluctuation in readings may have been caused by my heart beat. If I get a chance I'll put on DVE and try it again using a tripod.

Sounded like pink noise, but then as I get older it is all begining to sound like pink noise. Maybe I'll blow the dust off an old FM tuner and listen to the inter station hiss. Actually on my unit, the quick sound check is different in balance than the more complex set up. That one uses two tones, one after the other. The second tone is much more bassy. So it may have been one of the other colors.

A change in spectral balance makes sense. No mic is perfectly omni-directional and certainly the amount of reflected sound will vary with frequency.

Alas I no longer have access to anything more sophisticated than a digital multimeter, so I must leave testing the hypothesis to those of you who do.

rubs-

My first attempt to reply was lost in the load balancing, so hopefully this time will work.

I am still not quite with you. Where you able to generate test tones and use them set the trim? If not a url for the manual will really help. I have the HT-R501 but don't know if that is right.

But assuming that you did or will on to your questions.

The trim levels you set are with in the normal range.

Don't worry about the master volume control position. This exercise is to balance the levels of each channel as heard at the listening position. Once you do that you can set the volume control where every you like when listening to TV or DVDs or CDs.

If the sub is not quite what you like go ahead and raise the level from -8 to - 4, and or to 0 dB. If that's not enough try +3dB. That is really large increase --about double the sound level.

If that did not do it, take a look at the sub 1 2 3 settings (if you have them). Each of them changes the amount of bass sent to the sub. Sub 1 should have more bass than sub 2. Sub 3 will have no bass unless you are listening to material with a Dolby LFE channel.

Search this forum for test tone downloads, or rent Avia or Digital Video Essentials

Keep us advised.

Hey guys,

I am just now setting up my NAD equipment and learning how to do this properly. I just wanted to thank you for the head start. This thread was like reading my future over the next few days/weeks. I appreciate it.

KKobi

Thanks all,

The measurement of sound is fun and very revealing. Your ears will thank you. I'm glad there's no appreciable difference in pointing at the source or straight up, at least for the RS meter.

For what it's worth, I have always used a tripod, and I've tested speakers every way imaginable. When testing in-room response on stereo speakers, I point the meter between the two from the listening position at ear level.

I have Stereophile's Test CD 3 that works okay in a player, but if you can connect your computer to your system, that is the only way to go. The program I have defaults to 12th octave steps, and you can play sine, square, triangular, sawtooth, impulse, and white and pink noise. I stick with the sine and pink noise as I don't yet understand the significance of the other noises.

Doug

It's a PC program called NCH Tone Generator. It's a free download, but they would like some money eventually. There are others, but this one works for me.

Sorry for the delay, this site has been busy. Couldn't get in for two days.

Doug

I use and like the free REQ Wiz software. You need a PC sound card with line in and an SPL meter like the one from Radio Shack.

Downloads, instructions and advice can be found here http://www.hometheatershack.com/roomeq/ There is some good discussion on this avs thread here

It sounds like the problem is between the laptop and receiver. Have you ever successfully played audio from the laptop through your receiver?

--Ethan