# Galaxy CM 140 and level measurements: What is the right level for my subwoofer?



## actarusfleed (Nov 30, 2009)

Hy guys,
I'm here with my new Galaxy Cm 140.

I simply whant to measure the sound pressure of my speakers after the acustical calibration.

To do this I feed my speaker with the Pink Noise generated by my PRE (Ada Suite 7.1).

I know that my CM140 must be setted like this:
>C weight
>Slow

Ok, If all this conditions are right for you ... Can you suggest me what is the target pressure for my subwoofer related to the pressure of the other loud speakers?

thank you so much,
actarus


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## Dale Rasco (Apr 11, 2009)

What have you leveled the other speakers at? 70db? 75db?


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## actarusfleed (Nov 30, 2009)

@rasco
loud speakers @76db


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

The quick answer is, probably between 6-10 dB hotter than your main speakers. It will depend on the size of your listening room; smaller rooms generally “need” a higher sub setting than larger rooms. You might want to read over my house curve article for more info (link in my signature).

However, you have to consider that most rooms introduce peaks in subwoofer response, such as you see here:










The graph shows that certain frequencies register higher SPL levels than others. The problem we have in calibrating the sub level is that SPL meter is “dumb.” It will _only_ register the level of the frequency that’s generating the highest sound level – about 45 Hz in the case of the graph above. In other words, a SPL meter reading of this sub above would register ~96 dB, and the peak at 45 Hz would be responsible for that figure.

This is why it’s important to use equalization to flatten out the sub’s response before calibrating its level in relation to the main speakers.

Regards,
Wayne


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## actarusfleed (Nov 30, 2009)

Wayne A. Pflughaupt said:


> In other words, a SPL meter reading of this sub above would register ~96 dB, and the peak at 45 Hz would be responsible for that figure.
> 
> This is why it’s important to use equalization to flatten out the sub’s response before calibrating its level in relation to the main speakers.


Hi wayne (forgive me I'm newbie about this "world")...
Yes, I read your article about the home-curve and I undrestand your quote above but ...

Imagine that I've already done a "perfect" calibration on a flat curve.

Well, I whant to undrestand If the pink noise reproduced by a subwoofer (respect other LOUDspekers) generates (natively) a different SPL reading to my CM 140?

In other words: My CM 140 read identically pink noise generated from a subwoofer respect pink noise on the other loud speakers?

sorry for my poor english ...:sweat:

actarus


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

No worry actarus – your English is better than my Italian. :laugh:

I understand now that you’ve already equalized your subwoofer to take out the peaks. If you’re asking what the subwoofer SPL level should read compared to the main speakers SPL, typically the subwoofer will need a higher SPL reading than the speakers. How much higher depends on the size of your room, and your personal tastes (that is, the amount of bass you like), but generally most rooms will show the subwoofer between 6-10 dB louder than the speakers. You might start with 6 dB and listen for a while. If the bass sounds weak, then try 8 dB and listen again. Keep trying until you think it sounds right.

Regards,
Wayne


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## Brenton C (Feb 14, 2015)

Sorry to be reactivating an old thread here, but I'm reading only here for the first time that I should be equalizing the subs, alone, before adding in the mains plus subs. 

Is that right? Maybe that's why I'm having so much trouble. 

I have 2 Rythmik subs, a DSP 1124 PEQ, and plans built horns for mains. No high pass on the mains -- they fall off rapidly below 130Hz.

I've been equalizing the low bass with all speakers going, using REQ and the Galaxy 140 spl meter.


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## tonyvdb (Sep 5, 2007)

Yup, start with the subs alone.
With having to run your crossover so high that is going to be a challenge because bass from a sub that is above 80 Hz becomes localizable. Have you placed the subs in good locations in the room by doing a sub crawl test?


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## Brenton C (Feb 14, 2015)

Hi Tony, 

Thanks for the quick reply. No crawl test. I just placed them more or less symmetrically to the outside of the mains, but back against the wall. One happens to be almost in the corner, the other more or less midway down the long wall of my living room. Mains are out from the wall, about 3' at their fronts. 

I'm guessing from your question that the crawl test is a really good idea, hey? Now that I have recently put 10' interconnects on the subs, I could do that subwoofer crawl without too much trouble, though my dog might thnk I look funny.


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## tonyvdb (Sep 5, 2007)

Yup, the crawl test is a good start. Place one of the subs or both as close to the listening position as possible and then crawl around the outside of the room while playing some base heavy audio and where you hear the best response thats where the sub should go.
If you choose to use test tones remember that sustained low frequency test tones can damage a subs motor due to excessive heat.


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## Brenton C (Feb 14, 2015)

tonyvdb said:


> Yup, the crawl test is a good start. Place one of the subs or both as close to the listening position as possible and then crawl around the outside of the room while playing some base heavy audio and where you hear the best response thats where the sub should go.
> If you choose to use test tones remember that sustained low frequency test tones can damage a subs motor due to excessive heat.


Thanks for that tip about the test tones, because I sometimes do use test tones. I had no idea about the risk.


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## FargateOne (Mar 3, 2015)

neither do I !


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