Sound Measurements - Techniques and tools

[anm]

Hi,
What do you guys do to measure responses of speakers/ system in your rooms?
I am looking forward to understand how to measure and understand those measurements.

What are the tools being used - microphones/ microphone amp, sound card etc.

One of the system reviewed at stereophile is - Music in the Round #51 Page 2 | Stereophile.com

This one is attractive as it doesn't need anything but a usb connection to your laptop. Quite expensive though.

Any other suggestions?

 

[raj]

You need a test tone generator to generate various frequencies and a meter to measure the sound level (db). The basic instrument to measure the sound level is an spl meter. But now a days there are apps for iphone (and other i-devices) that can do the job.
Then you need something like a guided program to use these. I have had setup disks which would run the signals through different channels and give you instructions on how to adjust the volume of different channels.
RoomEQ is a software available for free and you can use an spl meter with it to measure the acoustic characteristics of a room.
Hope this helps. Happy exploring.

 

[deba]

I sometimes use the Signal Generator of Adobe Audition (use old version, the new version do not have the feature) to test my amp and speaker, but above all a good pair of Ears is what I need to measure my system.........

Setup your system in totality and make minor changes till it suits your taste.....each one of us like to hear our system differently hence there is no golden rule of good sound and bad sound....)

 

[anm]

deba - I agree. Listening by ear is not discounted, but I would also like to see how changes are impacting the measurements. And the speakers behave differently with different rooms so looking for some minor enlightenment

 

[anm]

Since I would be using a laptop, pls suggest some locally available not so expensive usb sound card.

Mic - Behringer ECM8000 Measurement Microphone 248-625

s/w - REQ

usb mic preamp/ sound card - pls suggest

Good readings on basics - please suggest.

 

[anm]

Here is one list of items I have created
1. mic - dayton or behringer mic - which one would you recommend? ~$100
2. USB pre - ~$150
3. Cable to connect mic and pre. xlr - 15 ft.
4. cable/ connectors to connect line out to line in for one channel.
5. headphone out to RCA - so that I can connect line out to my AVR/ stereo amp.
6. galaxy CM 140 spl meter - ~140 for verified.
7. cable to connect CM 140 to pre.

Has anyone gone this route? What did you purchase?

This option includes an spl vs option 2 listed below. Pre calibrated mics can also be purchased, but they are close to $100.

This costs ~$250 plus the spl meter.

Con: don't know if these things from various sources would work together fine.

Advantage - should work with many applications using a laptop, including free REW.

 

[anm]

Option 2 is to use
1. ipad 2
2 iaudiointerface2

3. Cable to connect mic to iaudiointerface2
4. cables/ connectors to connect amp to iaudiointerface2

This one costs close to $500 just for iaudiointerface2 and mic.

Advantage - less hardware, straight forward.
Disadvantage - iaudiointerface2 DOES not work with laptop or computers. You are therefore limited to ipad and the paid app.

 

[anm]

has anyone here purchased any of these? Which one would you recommend?

 

[ashishkesarwani]

To measure the room response for different Frequencies in a room you need a signal generator which is measured through a RTI meter, now this is the method professionals use to correct the room response to a particular frequency by finding it and then using corrective measures.
Another method of doing it is through a computer/Ipad/Iphone based software connected via a pre amp to a pre-calibrated microphone and then the test tones are generated via the applicable software and then the measurement is taken for a particular position.
This is the same principal which is adapted by all calibration systems as they first take the room response and then correct the same by equalizing each speaker such that it's curve becomes as flat as possible.

 

[anm]

REW is the software to generate test tones.
For measurement, I would need hardware. I can think of only 2 of the above options.

BTW, for my room, the NAD should be able to correct the room response, right? But does it correct for both subwoofers individually?

 

[Jaybe]

has anyone here purchased any of these? Which one would you recommend?

anm,

I recently procured Dayton Audio EMM-6 Electret Measurement Microphone from Parts Express to measure Speaker response. This comes with its unique calibration plot. I am toying with using Winisd or ARTA software for frequency generation and measurement.

Jayant

 

[anm]

thanks. how are you powering the mic. How are you connecting it to your computer? Desktop or laptop?

 

[msagar]

I use Radioshack Digital Sound Level Meter.

http://www.radioshack.com/graphics/uc/rsk/Support/ProductManuals/3302055_PM_EN.pdf

Also use Test CDs from different sources (Stereophile, Reference Recordings, Chesky etc).

 

[anm]

do you use any analyzer (RTA)?

 

[jetlag]

anm
I suggest you use "Speaker workshop". I find it easier than Arta. The only hitch is that you will have to cook-up a small ckt to condition the mic output. Having said that, it requires to tonnes of patience to do the measurements. The first few runs can be very frustrating (no, I am not trying to discourage you..just from my exp), in the end it yields some result which can help you understand your xover.
I trusted more on my ears than on the meas to arrive at where I have. As long as you know how an instrument sounds acoustically it makes the job that much simple.

Then again, any good mic not necessarily a calibrated one with a decent sound card which accepts rca inputs will do the job for you.

Peace
Jetlag

 

[anm]

^^ thanks.
Can you suggest such sound card? I do not have a desktop, I want to use laptop or ipad.

 

[t.antony]

I got acceptable readings with HOLMImpulse(HOLM Acoustics) using my laptop's internal sound card. If your laptop has separate input and output jacks, then probably you won't need a separate USB sound card. The extra hardware required would be a loop-back cable and the mic of your headset apart from your amp and speakers.

My iball headset mic gave acceptable readings in the 30Hz+ region when compared it with Behringer ECM8000. If you are not measuring extreme lows and highs then the headset microphone might work fine.

A loop-back cable looks like this.

Tutorial on HOLMImpulse - http://www.avsforum.com/avs-vb/showthread.php?t=1236094

BTW Room Eq Wizard also seems to work with the same hardware. I did not test extensively so can't comment on the accuracy. - Here is a tutorial on REW - Room EQ Wizard - Step 1 - Calibration - YouTube

 

[kaushik]

a web link 4 anm :
Measuring Frequency Response Using ARTA

http://sound.westhost.com/project58.htm

An electret capacitor microphone is a cheap and remarkably accurate little device, but they are not known for tolerance to high SPLs. The FET preamp is usually very crude, and having no source feedback resistance will distort readily at modest sound pressure levels. To this end, Siegfried has gone to work on a standard capsule, and modified it so that it will work at standard test levels.

 

[anm]

thanks Antony. My first objective after measuring is to adjust subwoofer response, so I guess I would like to see how much content is there below 30 Hz.

 

[Thad E Ginathom]

Here's a couple of things that might be interesting:

krk Ergo --- but this, I think, assumes you are playing the music from the PC that you are measuring with, and applies a correction to that output --- so no good for measuring and setting up independent system.

Genelec DSP series This one means buying the speakers. Again, not useful for calibrating a system you already have --- but it is an active speaker system, not only with its own amplification, but also with its own DAC. Takes a digital input. Uses a mic and supplied PC interface/software for auto calibration.

ISTR a member using something for Behringer for room correction sometime back?