# Setting speaker and subwoofer levels



## Doctor X (Apr 3, 2007)

Hi,

Although I'm still in the process of moving to REW, I have a few questions with regards to setting levels out of curiosity. I have a normal SPL meter right now and I use test tones in my AVR to set the levels to 75 dB's.

Now as I understand it the Dayton and Behringer mics are more accurate than the Radioshack SPL meters for reading levels. So what is the best and most accurate way of setting speaker and subwoofer levels? How would I set the levels in REW... ?


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## Wayne A. Pflughaupt (Apr 13, 2006)

Hey Vaughn,



Vaughan100 said:


> Now as I understand it the Dayton and Behringer mics are more accurate than the Radioshack SPL meters for reading levels.


I think perhaps you have the use and/or purpose of the mics vs. the meter confused. The mics don’t read sound levels; the sound level meter (SLM) does that. The mics are more accurate than the Radio Shack SLM for taking _frequency response measurements,_ but then the SLM wasn’t specifically designed for that.

Keep in mind that “accuracy” with a SLM is not the same as “accuracy” with a measurement mic. With the meter, it’s how accurate its SPL reading is. The Radio Shack meter is a Class 3 device, which means its tolerance is ±1.5 dB.

Now, after using the SLM to calibrate REW’s SPL, REW can then take sound level measurements, using a measurement mic. However, it should go without saying that REW’s SPL measurement won’t be any more accurate than the meter used to calibrate it.

Personally, I just calibrate my speaker levels with a SLM. It works perfectly fine. I know John prefers to use REW for speaker calibration; perhaps he’ll chime in with some pointers for you.

Regards, 
Wayne


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## aackthpt (Jan 24, 2011)

The way I see it, relative level between the channels is more important than absolute level when setting up an AVR. And since they are all being set to the same level, linearity (meaning, basically, consistent accuracy across a range) is not an important characteristic of the measuring device either. One could guess that precision of the measuring device would be important, but since AVRs (in my experience) only adjust in 1dB increments, and the Rad Shack meter can be read to that accuracy, the 0.1dB readability of the REW SPL meter is not really much of an advantage either. The advantage I _can_ see of using the REW SPL meter over the RS one is that the mic probably has a much wider usable bandwidth than the RS meter mic, and because it is programmed in software the weighting curve will be more accurate--all of which might lead to more accurate settings between subwoofers and mains.

All in all, perhaps a slight advantage for using the REW SPL meter over the Rad Shack meter. Much more so if you were to set up REW's SPL meter level using an SPL calibrator rather than comparison to the RS meter with white noise (per the regular procedure).

After setting levels with the AVR noise signals, I usually use the RTA and signal generator with white noise to look at the balance visually (especially if going for a house curve), also will run some sweeps of L/R to have a look at the FR and verify that I'm happy with the result. I may adjust the subwoofer balance this way regardless of the test tone results, and I think I am often able to achieve a better balance this way.

I have also found that it makes a big difference where I put the measurement microphone, an effect which must be related to the effects of modes in my room. When I set the sub level with the mic in the center I don't like the sub balance, but if I do it with the mic in either of the actual head positions which are slightly left and right of center I get a much better result.


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## bongo charlie (Jun 17, 2012)

Hi, which model radio shack meters are you referring to, i have model 3300099 is that any good? alternatively i have an emu 0202 and a DBX rta mic, would that be a better setup?


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## aackthpt (Jan 24, 2011)

Welcome to the Shack, bongo charlie.

It's not polite to glom onto someone else's thread (start your own) but in the interests of expediency I will just answer here.

For the purposes of setting (relative) channel levels on your AVR, any SPL meter (even an iphone app for that) is good enough.

If you want to use an RS meter as a microphone for REW (a use which was not being discussed in this thread) that is a different story. One downside is that there isn't a correction file for that model yet listed on the downloads page. If you want to get more into it look up more info such as Ethan Winer's page on RS SPL meters, also in this thread there are some comparisons a fellow did between an older model RS meter that _does_ have a known cal file and this newer model, which should be able to give an idea of the relative accuracy.

On the other hand I'd recommend to anyone really caring to do a good job to invest in a decent microphone and preamp rather than using the RS meter as the mic--even if I do appreciate the populist appeal of the free REW + RS meter combo.


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## bongo charlie (Jun 17, 2012)

Sorry didint mean to hijack the thread I will read through the forum rules. thanks for the links I'm readig them pesently. Sounsd like its best just to use the RS meter to check im not deafening my audience, and my DBX RTA mic and emu 0202 for teh measurements.


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## Wayne A. Pflughaupt (Apr 13, 2006)

bongo charlie said:


> Hi, which model radio shack meters are you referring to, i have model 3300099 is that any good? alternatively i have an emu 0202 and a DBX rta mic, would that be a better setup?


Expounding a bit on what John said, the Emu- dbx rig would be better _*IF*_ you have a calibration file for the dbx mic that REW can use. This mic has been discussed before, and perhaps someone has posted a calibration file for it – try using the search function. If not, if you can obtain a manufacturer’s response chart for the mic you can create your own calibration file –  see this post. Just keep in mind that a manufacturer’s response graph will be generic, as it’s doubtful that ever sample that they send out the door has the same identical response.

And also keep in mind that without the calibration file what you’d be seeing with any frequency response measurement is a combination of both the room and the mic’s response. The calibration file compensates for the mic (i.e. renders it effectively flat) and lets you see the actual room measurement.

Regards, 
Wayne


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## aackthpt (Jan 24, 2011)

Here is a discussion of calibrations for this very mic with several alternate mic cal sources. Also Wayne has linked ppl to a cal file being traded around here before (LOL) here. A more recent thread happened here.

At least in the US, it is also an option to get a slightly less accurate cal file with a mic by buying a Dayton EMM-6 for $48 from parts express, but I wouldn't be surprised if shipping killed that deal unless Dayton has a dealer in the UK. A quick search does turn up a dealer selling it in DE for 48 euro.


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