# Room Measurment equipment for Cinema Room



## kam (Sep 13, 2010)

Hi All,

I have read through several posts on this forum relating to sound measuring equipment but still need a little guidance. I am interested in setting up a dedicated home cinema room and having spent a lot of time on the room acoustics forum am likely to need bass traps / absorbers etc but need to undertake a series of measurments first to determine the 'problems' in the room. I have an Onkyo tx-NR808 AV Amp which has audessy setup, but I don't want to use that yet, if at all. 

I was proposing to use my laptop and:

Maplin external sound card £20
RS Digital sound Meter
REW software.

Having read through the sticky on this forum I then changed my mind and thought I would get the behringer ECM8000, but then read that I also need the behringer xenyx 502 or similar to provide the Phantom power. I then read that the RS should be fine if it is just for setting up the subwoofer??

The truth is that I dont know what I need to do to setup the cinema room - is it just the subwoofer that needs measuring or the other speakers, or the room itself? Apologies if this sounds a bit daft, but I don't want to buy the wrong equipment and am aware that i need to use REW to set the room up correctly. I don't mind buying the behringer, but don't want to unless I have to as it seems a little more complex to set up. The photo of the Xenyx 502 hurt my head!:hissyfit:


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

Hey kam,

I’d say subwoofer measurement and EQ is a must-have, and as you’ve found, you can do that with nothing but the Radio Shack SPL meter and the cheapest sound card you can find.

There’s really no reason for accurate full range measurements if you don’t have the means to implement equalization if it is called for. However, some people like to do it anyway, just to see what their system is doing, and/or what auto EQ systems like Audyssey have accomplished.

Naturally, for the most accurate full range _frequency response_ measurements you need a custom-calibrated mic. An all-in-one USB audio interface like the M-Audio Mobile Pre or Tascam US-122 is a simpler option than the Zenyx 502, IMO. Another option that might be attractive if you don’t already have the Radio Shack meter is to buy a calibrated Galaxy SPL meter from Cross Spectrum. It would give accurate full-range frequency response measurements using a regular sound card.

Since you’re interested in acoustical treatments, impulse or ETC measurements are what you’re interested in. I see you’ve already been talking with Bryan at our Acoustics Forum. I’m not sure how critical accurate measurements are to gauge the effects of acoustical treatments; you might check with him and see. It might be possible to get away with an off-the-shelf ECM mic with our generic calibration file. If so, that would save you some money.

Regards,
Wayne


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## kam (Sep 13, 2010)

Hi Wayne,

Thank you for the helpful response, I will indeed check with Bryan. Before I do, can I please clarify that what you mena by Off the shelf ECM Mic, is the Radio Shack Mic - apologies if this is obvious, just not to me!


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

Off the shelf, meaning an ECM8000 you purchased at your local guitar shop, mail-order music supply store, etc. – as opposed to buying one from Cross Spectrum that’s been custom calibrated.

Regards,
Wayne


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## kam (Sep 13, 2010)

Hi Wayne

This is Bryan's response:



> I would agree for the most part. The Radio Shack (or some other SPL meter) will be required anyway to calibrate levels. No reason you can't use it along with the correction plug-in for doing measurements. It will be fine.
> 
> As for the sound card, we just need one that is bi-directional (can play and record at the same time). Any non-linear response will be adjusted for during the loopback calibration step.
> 
> ...



Am I reading this correctly that the RS digital meter will be fine and I need no other mic? Also, this is a link to the soundcard I am looking to purcahse, does this meet the requirments? 

http://www.maplin.co.uk/Module.aspx?ModuleNo=97120

Thanks in advance, Kam


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

kam said:


> Hi Wayne
> 
> This is Bryan's response:
> 
> Am I reading this correctly that the RS digital meter will be fine and I need no other mic?


Sounds like that’s what he’s saying. But he may not be aware that we don’t consider the RS meter to have usable (read unpredictable) accuracy above 3 kHz. You might double check with him to clarify if he knows that. 




> Also, this is a link to the soundcard I am looking to purcahse, does this meet the requirments?
> 
> http://www.maplin.co.uk/Module.aspx?ModuleNo=97120


Looks like it will, as long as you’re not considering a calibrated ECM8000 (or similar) mic. If you are, go for a USB audio interface.

Regards,
Wayne


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## kam (Sep 13, 2010)

Hi Wayne,

Just to close this off for anybody else who may read this thread, here is the response from bryan:



> It just needs to be accounted for when looking at the plots from an absolute response standpoint. WHen doing comparisons for placement, it won't really matter.
> 
> Above 3kHz is way too high to worry about in terms of placement and treatment. You're not going to change that. We're more concerned with 20-300Hz for the most part.


So all looks fine for the RS SPL.

Thanks for your help, 

Reagrds, Kam


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## kam (Sep 13, 2010)

Hi Wayne / all

I now have all of the equipment and have tried all evening to get the soundcard calibrated. I purchased the Maplin usb card as per the link below. I have followed the diagrams and procedures in the help file but cannot get the soundcard calibrated. 

When i try to calibrate, having selected the default sound card (and made the Maplin card the default under the OS) i can adjust the AV Amp volume so that the DB level output on the L&R channels matches the 12db input, but when it goes to the next stage to measure the soundcard it keeps throwing up an error saying that clipping is occurring. The only way i can get rid of this is to reduce the AV AMP volume down by 50% and even then i just get a more or less solid graph.

One thing to mention, if i connect the RS SPL to the line-in on the soundcard, I cannot adjust the AV AMP to match the 12 DB, the right and left channels are frozen, the only time it all works is if i have the mic (and loop) plugged into the Mic In port on the USB card. I am using 2 x the Y spplitters as per the diagrams. Any thoughts would be appreciated.


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

Do you have a link to the sound card you’re using? The only Malpin I could find only had a headphone output, not a line output.

Regards,
Wayne


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## kam (Sep 13, 2010)

Hi Wayne, the link was above in an earlier post to you, soryy I shoul dhave made that clear. Here it is again: 

http://www.maplin.co.uk/Module.aspx?ModuleNo=97120

Good News - after another day trying various things, Ihave got it working and produced a graph as per the Help files!! The solution appears to be to delete (or not install in the first place) the soundcard software that comes with the soundcard. When Ireverted to the standard Windows Vista USB generic driver, it all seems to work with the standard Windows sound software in Control Panel.

Thanks for your help to date....onwards and upwards! Kam


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