Novice - To Measure or Not To Measure

**Nick** · **10-28-09, 04:21 PM**

Hello, I am a new member with an interest in finding out what my room measurements are. After reading through some of the material I see that it is much more involved than I anticipated and I have no electronics or hardware background.

As background, I just finished reading Dr. Toole's book, Sound Reproduction. I do not have a home theater, but I do have a dedicated two-channel listening room with room treatments, including Real Traps and homemade tube traps. The speakers are 'full range' floor standers. Before making changes, like adding a pair of sub-woofers and parametric EQ, I would like a baseline. So, I really would just like to make high resolution acoustical measurements with my laptop, if possible.

I have both a Radio Shack digital meter and a Phonic PAA3 RTA with line in and line out XLRs. I do not have a processor or a receiver, just an unbalanced multi-channel amp and an unbalanced preamp with two line out functions and a tape loop. My computer has only a microphone jack.

I am wondering if anyone has experience with the Phonic and whether it is an appropriate microphone and meter to use with REW. Given that my computer has no line-in function, I would also like to know if there is something appropriate in the way of a cheap external USB soundcard at Radio Shack.

I would welcome any additional thoughts you may have for one who is just getting started.

Many thanks in advance,
Nick

**Wayne A. Pflughaupt** · **10-28-09, 05:43 PM**

Welcome to the Forum, Nick!

Not clear from your post, are you looking to take full range measurements, or just the low frequencies?

Regards,
Wayne

**Nick** · **10-28-09, 06:04 PM**

Hi Wayne,

Thank you, it is nice to have access to the forum. It would be nice to measure all the frequencies, but I would be quite happy to better understand the low frequencies that may benefit from EQ. My room has a large opening as well as a decent amount of windows, so I think bass rolls off significantly below 40hz.

Nick

**Wayne A. Pflughaupt** · **10-28-09, 07:02 PM**

Quote:

I am wondering if anyone has experience with the Phonic and whether it is an appropriate microphone and meter to use with REW.

Not likely. Any mic you use with REW requires a calibration file. Since most mics do not have flat response, the calibration file allows REW to compensate for its inaccuracies and produce a reading as if the mic truly were flat. Since the PAA3’s mic is built in, it would be pretty tough to create a calibration file for it.

Not that it matters in your case – if you only want to measure bass response, your Radio Shack SPL meter is all you need, and we provide a calibration file for it.

Quote:

Given that my computer has no line-in function, I would also like to know if there is something appropriate in the way of a cheap external USB soundcard at Radio Shack.

It seems to be hard to find any 2.0 USB sound cards with line in and out for less than $50. I suggest finding a used Creative Labs MP3+ on eBay (since it’s a discontinued product). May not be a whole lot cheaper, but it has no calibration issues in REW. That alone might make it worthwhile for you, since you say you find all this a bit of a challenge. (Like the mic, the sound card also needs a calibration file; REW generates the calibration for the sound card. With some sound cards seem to be problematic generating a calibration file.)

Regards,
Wayne

**Nick** · **10-29-09, 12:21 AM**

Wayne, my Phonic RTA has a calibration feature. But it sounds like I need to purchase equipment that can be calibrated with the software. If that is so, I guess I would rather buy the sound card you recently reviewed and purchased, given the small price difference from the discontinued model. You mentioned it had EQ functionality, but I imagine one would still need the ability to change the crossover frequency at some point, thus need one of the behringer products, too.

I can learn with the Radio Shack SPL meter and then move on to a better mic later with hope that the various connections will be the same when I change mics. Is there a mic that you would suggest for full range measuring?

Thanks again,
Nick

**brucek** · **10-29-09, 08:11 AM**

Quote:

Is there a mic that you would suggest for full range measuring?

We usually recommend the Behringer ECM8000 or the Dayton EMM-6, since we provide generic calibration files on our download page.

brucek

**Wayne A. Pflughaupt** · **10-29-09, 09:15 AM**

Quote:

Nick wrote:

Wayne... I guess I would rather buy the sound card you recently reviewed and purchased, given the small price difference from the discontinued model. You mentioned it had EQ functionality, but I imagine one would still need the ability to change the crossover frequency at some point

Ya lost me there. I haven't seen any sound cards with EQ functions...

Regards,
Wayne

**Nick** · **10-29-09, 10:48 AM**

Thanks, Wayne. I was referring to the 10 band EQ in the Turtle sound card used when someone listens via a computer. I see that it would not be used in my system.

I am about to buy the sound card, so wonder if it helps the HTS site for me to buy it via a link to the product? Otherwise I will just go to the Turtle site directly...

**Sonnie** · **10-29-09, 12:14 PM**

Hi Nick and welcome to the Shack...

Which one are you looking at? The SRM may be a little less through the Shack Electronics Store and qualifies for free shipping if you are not in a hurry to get it.

**Nick** · **10-29-09, 01:10 PM**

Thanks Sonny, glad there is an Amazon referral, which I just did via the site. I plan to try a measurement with the radio shack meter, but imagine I will want a full range measurement after I learn to use the software.

Now I am trying to imagine what else is recommended to get full range measurements and perhaps EQ at the low frequencies. Is it better to get a mic/preamp or the Galaxy meter? Is there a product that can serve as a preamp and parametric EQ/external crossover for biamping so I don't have to buy both? I am seeing many iterations, so I am hoping to understand how to narrow down what will do the job best.

Thank you,
Nick

**Sonnie** · **10-29-09, 06:07 PM**

For full range measurements I prefer the mic/preamp combo. I am not familiar with the various mic preamps to give you advice on which ones do what, but I am thinking someone will know and chime in.

**glaufman** · **10-30-09, 10:53 AM**

Not sure about the preamp/PEQ combo, but for preamp alone, the Xenyx 802 from Behringer does a great job for me, and may be the best value out there...

Although I'm curious myself: it's been said many times that the the Galaxy SPL (the models with the line level output) is suitable for full range measurements, but it's also been said many times that the mic/preamp combo is preferred for full range measurements... so what exactly is the advantage of the mic/preamp combo? For argument sake, if need be, we can limit this to the ECM...

**Nick** · **10-30-09, 01:19 PM**

I just checked the HTS Electronics store and found there are no links to purchasing the Xenyx 802, although I see it via a Google search (only mention this because I assume HTS misses out on the kickback from the seller).

I look forward to hearing others thoughts with regard to Gluafman's question in the above post (can someone tell me the process for copying and pasting quotes in the blue background?).

**Sonnie** · **10-30-09, 01:55 PM**

I am not sure why that product is not showing up... beats me...

You can use

Amazon

if you don't find it for less somewhere else.

**glaufman** · **10-30-09, 05:35 PM**

Quote:

Nick wrote:

I just checked the HTS Electronics store and found there are no links to purchasing the Xenyx 802, although I see it via a Google search (only mention this because I assume HTS misses out on the kickback from the seller).

I look forward to hearing others thoughts with regard to Gluafman's question in the above post (can someone tell me the process for copying and pasting quotes in the blue background?).

There's another same, or at least similar, product called the Eurorack, I think, may actually be the one I have.

**Nick** · **10-31-09, 12:11 AM**

I have gotten stuck while trying to calibrate my RS meter to the software. When I play pink noise, the meter clocks it at 75db but the software says it is -36 db. The software says that the noise level is 75db when there is no noise being played, so it appears my calibration is done improperly.

It appears that I have not done this:

"Connect the soundcard's line output directly to its line input - use the channel that will be used to make system measurements, which should be the same one that has been selected in the Input Channel control

Is there a photo that shows how this connection is done?

**Nick** · **10-31-09, 01:30 AM**

Okay, problem solved - I was using the mic stereo line in and out instead of the line in and out. That after reading the direction many times!

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