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SPL Meter


Iceman

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You can get analogue test CD's from direct-to-disk (vinyl LP) recording company Sheffield Lab

http://www.sheffieldlab.com/catalog.html#test'>http://www.sheffieldlab.com/catalog.html#test

http://www.sheffieldlab.com/

In regards to SPL meters, be aware that inexpensive SPL meters like the one from Radio Crap are really only to "get you in the ballpark". These are not for things like 'tuning your room or system'. The microphone in them is not calibrated & there can be considerable deviation in frequency response. They're OK for getting a general idea of average sound levels. Peak level readings are not as accurate & can be off by as much as 12dB. These are in the catagory 'You get what you pay for'.

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mOOn,

As you await Artto's reply, consider:

I have a $40 RS digital. The RS model is recommended by many (including SVS, and folks on this board and other boards). It may be inaccurate, but as long as it is consistently inaccurate, I don't see a problem. Plus, as I was looking for a meter, I found many on eBay, and the RS was the only meter within my price range--the really good ones are really expensive.

Most seem to prefer the analog meter to the digital--quicker to react, I think. However, I have no trouble setting levels with my digital. A meter may surprise you how good (or bad) your ears are. Then too, I'm not sure I want all speakers at exactly the same level, as is consistently recommended. My ear "wants" the surrounds a bit higher, in which case, I might as well sell my meter.

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Depends on what you are using SPL for as to which to get,....

For just setting balance based on pink noise then a RS is great....

The RS is good as for comparison between speakers...but I would not trully trust it for setting a EQ for certain test tones.....out of one speaker and expect to get it perfect...it would work to get all speakers the same though...

HTH

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Moon, for general use I use a Radio Crap. When I have to take accurate measurements, in the past I've rented (or borrowed) a real time spectrum analyzer that comes with a calibrated mic.

Some of the better meters require you to use your own external mic (which should be calibrated), some don't. They can get pricey. $1200 or more.

see http://www.prosoundweb.com/studyhall/lastudyhall/slm/slm_4.shtml for more in-depth discussion.

By the way Moon, that Ethan Winer link you posted had some good stuff on there. I particularly liked his idea to place a calibrated mic at the listening position, play the test signal such as 'pink noise' & record it to a DAT. Then download the DAT to your computer & use the spectrum analyzer in Sound Forge to view the results. Dummy me, I've been using Sound Forge & DAT for years & the thought didn't even occur to me!

Moon, also, on the sound board stuff, looks like you're using something Celotex Insulating Sheating. The NRC (Noise Reduction Coefficient) is 23. They derive these ratings by taking an average over several frequencies, 250Hz, 500Hz, 100Hz & 2000Hz. It doesn't tell you much about the bass range. It's sort of a gray area which is why you must be careful trying to predetermine the acoustical characteristics before it's built. I've found it's better to leave some room for trial & error experimentation afterward.

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----------------

On 9/22/2003 1:42:58 PM artto wrote:

Some of the better meters require you to use your own external mic (which should be calibrated), some don't. They can get pricey. $1200 or more.

----------------

Ouch! Might as well hire someone to come in and do it for me. Thanks for the info on the soundboard. 1.gif Where did you get that info anyway?

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Celotex is located in the Chicago area (my hometown). They've been bought & sold a couple of times. Since it's a building product, me being an architect, I probably have access a little access to their products than most folks. But since this product is primarily used as rigid roof insulation and wall sheathing there weren't any sound specs listed I emailed their product support department. They are now called Knight-Celotex, based in Northfield, IL. When I was a kid my father used this stuff as a layer on top of plywood with the Lionel RR to deaden the noise. That was my first experience with it.

I all honesty, 23 seems a little high for a NRC rating. I think he may have meant 0.23 which makes more sense now that I think of it. I've emailed him back asking for clarification since in this rating zero is supposedly 'perfectly reflective' and 1 is 'perfectly absorptive'.

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Moon, I can tell you as a matter of fact, since I've used this stuff 'exposed' in my room, it can shed a lot dust which is one of the reasons in my room it's now behind the curved polycylindrical Masonite panels.

Auralex makes these thick angled acoustic foam bass traps in 2' long sections that will probably produce the same or better result than what you're trying to do via construction. It cost me a few hundred bucks for 8 sections. The advantage here is you can easily move them around & experiment to achieve the best results, add more or less. You can use 1-1/2" or 2" steel 'T' pins available at office supply stores to secure them to the wall temporarily (or permenantly). The T pins do very little, if any damage to the drywall. And the stuff looks cool too. I'd also be willing to bet that an 8' long section of these in each corner or across the back ceiling wall intersection has better low end absorption than anything you're going to build with Celotex. It has a much higher NRC rating right out of the box.

This guy sells it at a better discount than I can get at Guitar Center or Musicians's Friend. Fluxt.com Sales Write to Eric.

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Hey thanks artto! I will definitly look into it. As far as the dust goes, oh yeah after working with it I know just how nasty it can be which is why a nice looking fabric was going to wrapped around it.

I like the T-Pin idea... Never thought about it.1.gif

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I used some of the smaller pyramid foam in a corner behind a loud computer at the last place I worked. It really helped cut down on the fan noise.

2 Inch Studiofoam Pyramids acoustic foam absorption panels

If you go to the auralex website, they have info on the absorption properties. It can certainly make your studio look more professional, even if you aren't.

Lots of cool colors too.

Marvel

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See this is where it starts to get real crummy for me. I was at their site looking around at the various products... While I have no doubt in my mind they are good, they just don't cosmetically appeal to me in where I want to take my theaters appearance. It's going to be a compromise for me between acoustic treatments and decor. It's gonna be hard.

Artto.. You feel like taking a small vacation to Oregon? 1.gif

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You can buy a Behringer 8000 mike and mike preamp for about $110. Couple this with a sound card and free soft ware and you have an RTA. Works for me.

http://www.musiciansfriend.com/srs7/sid=030922132244216103104218723836/g=home/search/d=tp?q=ecm+8000

http://www.musiciansfriend.com/srs7/sid=030922132244216103104218723836/g=live/search/detail/base_id/53176

Jim N

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