# Rew/umik-1 vs. radio shack vs avr mic



## pdxrealtor (Jun 30, 2013)

My AVR mic sets levels very even, the radio shack meter confirms the levels were set at 75db. 

The UMIK-1 and REW combo measure about 3 db lower. 

Normally I would take the UNIK-1 any day over the rat shack meter, but i find it odd that the rat shack is matching what the AVR is supposed to be setting levels at. 

Which mic would you use to verify and /or set levels?


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## 3ll3d00d (Jun 6, 2006)

pdxrealtor said:


> My AVR mic sets levels very even, the radio shack meter confirms the levels were set at 75db.
> 
> The UMIK-1 and REW combo measure about 3 db lower.
> 
> ...


I tend to use the RTA while the tone is playing rather than a single reading of a (relatively) broadband signal that might get dominated by any in room variance. 

You don't mention which signal you're referring to (sub or mains) but I've read discussions that suggest mentally adding 2-3dB to the RS meter for sub pink noise measurements makes sense to counter the rolloff it experiences towards the lower frequencies (where room modes can be expected to be stronger).


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## pdxrealtor (Jun 30, 2013)

3ll3d00d said:


> I tend to use the RTA while the tone is playing rather than a single reading of a (relatively) broadband signal that might get dominated by any in room variance. You don't mention which signal you're referring to (sub or mains) but I've read discussions that suggest mentally adding 2-3dB to the RS meter for sub pink noise measurements makes sense to counter the rolloff it experiences towards the lower frequencies (where room modes can be expected to be stronger).


Mains and surrounds mostly, but both meters read the same as the mains on the subs too. 

So you fire fire up the RTA and watch the levels in real time, then adjust for 75 db?

Sent from my iPad using HTShack


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## 3ll3d00d (Jun 6, 2006)

pdxrealtor said:


> Mains and surrounds mostly, but both meters read the same as the mains on the subs too.
> 
> So you fire fire up the RTA and watch the levels in real time, then adjust for 75 db?
> 
> Sent from my iPad using HTShack


basically yes 

tbh if you have the frequency response under control then there should essentially no difference between the 2 approaches, it depends how flat your in room response is. Even if you have a known bit of variation in the response then you can at least choose which bit of the response you level to, e.g. say you have a narrow hump at 1kHz then you can just ignore that.

One nice thing with the RTA is that it can remember the peak trace. This means you can measure the sub, it remembers the peak in the sub frequencies & displays it as a red line. You then switch to a main channel and it will now show the RTA for that channel without disturbing the remembered sub trace (as the noise has moved to a completely different frequency band) hence v easy to level them visually. 

A picture would tell a 1000 words here btw (reading back it sounds complicated) but I don't have one handy.


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## pdxrealtor (Jun 30, 2013)

3ll3d00d said:


> basically yes tbh if you have the frequency response under control then there should essentially no difference between the 2 approaches, it depends how flat your in room response is. Even if you have a known bit of variation in the response then you can at least choose which bit of the response you level to, e.g. say you have a narrow hump at 1kHz then you can just ignore that. One nice thing with the RTA is that it can remember the peak trace. This means you can measure the sub, it remembers the peak in the sub frequencies & displays it as a red line. You then switch to a main channel and it will now show the RTA for that channel without disturbing the remembered sub trace (as the noise has moved to a completely different frequency band) hence v easy to level them visually. A picture would tell a 1000 words here btw (reading back it sounds complicated) but I don't have one handy.



Ahh... I see. I am talking about just playing the rumble tone from my avr, the same tone it uses to set levels, and watching an SPL meter. WHICH spl meter to trust is the question. I do understand it's all relative, but I am curious as to what spl meter others would use to verify the avr set the levels correctly. The rat shack which reads 75db exactly what the avr is supposed to set levels at, or the UMIK-1 and REW spl meter which is reading 3db lower (72db). The umik-1 and rew spl meter should, as you mention, produce the same result as the RTA method. The difference being how that result is displayed. RTA or REW SPL meter. Sent from my iPad using HTShack


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## 3ll3d00d (Jun 6, 2006)

pdxrealtor said:


> Ahh... I see. I am talking about just playing the rumble tone from my avr, the same tone it uses to set levels, and watching an SPL meter. WHICH spl meter to trust is the question. I do understand it's all relative, but I am curious as to what spl meter others would use to verify the avr set the levels correctly. The rat shack which reads 75db exactly what the avr is supposed to set levels at, or the UMIK-1 and REW spl meter which is reading 3db lower (72db). The umik-1 and rew spl meter should, as you mention, produce the same result as the RTA method. The difference being how that result is displayed. RTA or REW SPL meter. Sent from my iPad using HTShack


I don't think I understand what you mean.

in the last statement, did you mean (REW) RTA or RS SPL meter?

I would trust a UMIK-1 over the RS SPL meter.


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## pdxrealtor (Jun 30, 2013)

3ll3d00d said:


> I don't think I understand what you mean.
> 
> in the last statement, did you mean (REW) RTA or RS SPL meter?
> 
> I would trust a UMIK-1 over the RS SPL meter.



I hate internet talk sometimes.  

I didn't realize at first that your method of using the RTA to set levels is same thing as using the REW SPL meter. That's me assuming you are using REW and the REW RTA function as I am. 

It would not matter if one uses the RTA, SWEEP, or SPL meter to set levels as all three OUTPUT measurements are taken by the SAME INPUT device. In this case the UMIK-1. 

Going back to my post number - I don't see how logically I would choose the UMIK-1 when I have two devices that are setting levels the exact same and a third (the UMIK-1) that is reading three DB lower. 

In this situation logic (my logic) would say use the two that are reading the same. If an AVR sets all levels dead even, and the target level is 75 DB, and you check the level with two different SPL meters and one reads 72 and one reads dead nuts at 75 db is it a coincident that two out of the three mics are wrong, and wrong at the exact same DB level????? 

By saying you'd use the UMIK-1 you're saying that two other mics are incorrect. That's fine. That's the info I want to know. I also want to know how you justify that decision? 

Is it as simple as 'the UMIK-1 is calibrated? Or??


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## 3ll3d00d (Jun 6, 2006)

pdxrealtor said:


> By saying you'd use the UMIK-1 you're saying that two other mics are incorrect. That's fine. That's the info I want to know. I also want to know how you justify that decision?
> 
> Is it as simple as 'the UMIK-1 is calibrated? Or??


yes 

If the UMIK-1 has been independently calibrated (NB: I am assuming you got it from CSL so it has been individually calibrated, I don't recall how the minidsp calibration works if you got it from there) then it is correct. The other 2 mics are not individually calibrated so the fact they agree with each other is neither here nor there in my book.


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## pdxrealtor (Jun 30, 2013)

Thanks for your input. I tend to agree but cant put a side the fact the pioneer and rat shack are identical. Especially considering the pioneer measures distance to the inch correctly

It is a CSL calibrated mic. But i dont think they calibrate the sens data.


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## 3ll3d00d (Jun 6, 2006)

pdxrealtor said:


> Thanks for your input. I tend to agree but cant put a side the fact the pioneer and rat shack are identical. Especially considering the pioneer measures distance to the inch correctly
> 
> It is a CSL calibrated mic. But i dont think they calibrate the sens data.


IIRC the more expensive CSL calibration provides some sensitivity data. Anyway I suppose the thing to look into is whether all umik-1's have the same sensitivity and, if so, whether the cal file you are using has those values included. If both are true then it is a bit of a mystery as to why yours would be off.


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