Basic measurement setup

Why measure?

Every system can potentially benefit from using measurements. If you are designing or modifying your own speakers, or setting up a subwoofer, measurements are essential. Even if you have a simple 2 channel system there is still some benefit. Measurements won't replace critical listening skills, but they will help you make better choices, including many that simply can't be made by ear. It is a learning process, where you take measurements as well as listen carefully. In this process, you learn what to look for in the measurements since better looking measurements don't always sound better. Expectations often need to change.

Isn't it better to everything by ear, since it is the ear that is the final judge?

Find the answer here:
Measurements vs doing it by ear >

The best $150 you've ever spent on audio?

It's affordable and not exceptionally difficult. In the past, the cost was much greater where a measurement setup would most likely cost more than $1k. Now low cost tools will do the job.




Essential:
Behringer ECM8000 measurement mic >
Behringer XENYX 502 mixer >
Sound card which supports full duplex operation
Mic tripod (you can use a camera tripod but it's inconvenient)

Highly Recommended:

Cross spectrum calibrated mics >
(slightly more expensive than a stock ECM mic, but far more reliable results)
Boom mic stand

You'll find it much easier with a proper stand and if you plan to measure on a fairly regular basis, the extra expense is certainly worth it.

Why can't I just plug the mic into the PC?

The signal will be too low and you will not get a measurement at all.




Software

Fortunately, this part is free.

For bass measurements, download the free program REW from the HT shack here >

 

For full range measurements, Holm Impulse is both free and very easy to use:
Download Holm Impulse here >


Do you need a calibrated mic?

This depends on what you will measure. For fullrange measurements - definitely. For bass optimisation, you be the judge. Here is a chart that shows a number of the Behringer Mic unit to unit variation:


Image courtesy of Cross Spectrum Labs who offer a calibration service, and supply calibrated mics (including the Behringer mic shown here) at a very attractive price.
View Cross Spectrum Labs website >

As you can see, you get about +/- 2db at 40 Hz, worse at 20 Hz but not as bad higher up. The most you are likely to see is 2db out above this point, but if you are lucky you may get 1db or less. In truth that is probably enough, but then when you consider that it doesn't cost much more to be sure I think most would simply pay the extra.

If you already have a mic, you are probably best to sell it and simply buy a new one direct from the lab that has already been calibrated:

Cross spectrum calibrated mics >

The cost shipped to Australia is little more than the stock ECM mic.

There is a thread on the HT shack about this service, with some very useful info:

More info on the service >

Cables and connections

You will need balanced mic cable to connect the mic to the mixer and it's a good idea to pick up a good length like 10m, with XLR connectors on each end. Connect to a PC with jacks on "main out." The simple way is to connect jack > RCA adaptors then just run an RCA cable to PC. You can get a cable with RCA on one end and mini jack on the other, or again use an adaptor.

What kind of results will I see?

The most common use will be to get the bass right in your room. The best bass can't be bought - it must be tuned to your room.

Here is an example of in-room bass measurements >

In that example you will see examples of the mains and subs, how they are combined and a final result with EQ applied.

In the most basic system, it will show you which sub and speaker placements work best. In a more sophisticated system, it will help with placing multiple subwoofers and with using EQ without killing headroom.

How do I measure?

There are various methods to measure covered here:


Measurement techniques - an introduction