Speaker measurement tools

[westend9]

I would like to enter the speaker measurement universe and have nothing other than a JBL 5860 mixer that is probably not going to add much to the effort. I have been looking at mic's and sound card processors but haven't made any decisions.

What would be a good entry level set of gear to measure speaker response?

[bfish]

"Entry level" can get you in trouble unless you just want to use it once or twice. You can start with an onboard soundcard, compatible mic, and freeware. If you're like most of us though, a little info just makes you more curious, and soon the limited capability/accuracy of entry level doesn't get it anymore. I went through several upgrades just trying to have enough to get by the task at hand, and wasted a lot of dough getting there. I'd have been many dollars and headaches ahead to jump in the deep end first.

The deep end doesn't have to hurt too bad though. Around $300 for hardware and the same or less for software should get you there. Another $150 for a WT2 to do TS specs if desired. Since my gear is a few years old and I know there is newer/better out there now, let those that have been in the market recently point the way.

[westend9]

Thanks guys, good info, so far. I was looking at the Behringer ECM8000. Do you think a calibration is necesary?
What are the advantages of the M-audio product? As for phantom power, can this be as easy as just providing a power source? I do have some stand-alone power supplies in the 24v.-30v. range.
I'll take Bfish's advice on not trying to bottom-feed this to fruition. I've learned the hard way about not having good tools. I will probably start with one of the freeware software products just to get my feet wet, though.
I would like the gear to be able to interface with a laptop, for convenience. What is the typical connectivity, USB?

[bfish]

...And another $100 for the WT3 woofer tester with scale...

There are some reports (from reliable sources) that WT2 may still be the preferred option;

WT-3 testing of 2204, Fs higher in sealed box???

Which brings up another point. Test results are only as good as the gear, the setup procedure, and the interpretation of the results. It's a real treat that DIYers can now get the info they need, but bad info is worse than no info.

For example, TS specs can vary widely depending on the position and securing method (or not) of the driver. Indoor acoustic tests will have all sorts of false data unless the software has "windowing" ability to catch only the direct sound and shut off before any reflected sound arrives, and the user must set the appropriate parameters based on mic placement and distance to reflective surfaces. There's plenty of bad data posted online to prove it. Bottom line, read the book and follow the instructions.

[bfish]

Thanks guys, good info, so far. I was looking at the Behringer ECM8000. Do you think a calibration is necesary?
What are the advantages of the M-audio product? As for phantom power, can this be as easy as just providing a power source? I do have some stand-alone power supplies in the 24v.-30v. range.
I'll take Bfish's advice on not trying to bottom-feed this to fruition. I've learned the hard way about not having good tools. I will probably start with one of the freeware software products just to get my feet wet, though.
I would like the gear to be able to interface with a laptop, for convenience. What is the typical connectivity, USB?

I use an off-the shelf ECM-8000, but I preload the provided calibration file. There's certainly nothing wrong with calibration, every aspect of the hardware should be calibrated. You'll end up testing your testing system in order to trust it.

Integral phantom power can't be beat, especially for laptop/portable use.

USB 2.0 or Firewire ports offer the needed bandwidth.

The specs of your external card determine the resolution of your test. Pay close attention to the duplexing ability (simultaneous input/output), many units say "full duplex", but when you read the fine print, they only duplex at low to medium bit rates.

[westend9]

There are some reports (from reliable sources) that WT2 may still be the preferred option;

WT-3 testing of 2204, Fs higher in sealed box???

Which brings up another point. Test results are only as good as the gear, the procedure, and the interpretation of the results. It's a real treat that DIYers can now get the info they need, but bad info is worse than no info.

For example, TS specs can vary widely depending on the position and securing method (or not) of the driver. Indoor acoustic tests will have all sorts of false data unless the software has "windowing" ability to catch only the direct sound and shut off before any reflected sound arrives, and the user must set the appropriate parameters based on mic placement and distance to reflective surfaces. There's plenty of bad data posted online to prove it. Bottom line, read the book and follow the instructions.

I was wondering about the reliability of test results when doing "in room" setups. It would seem that any reflections (or absorbtions) are going to foster inaccuracies. Hell, I'll get my buddy that used to eat his lunch in the Bose anechoic chamber to help me set up something, lol (as long as we don't end up with something Bose-like).

I use an off-the shelf ECM-8000, but I preload the provided calibration file. There's certainly nothing wrong with calibration, every aspect of the hardware should be calibrated. You'll end up testing your testing system in order to trust it.

Integral phantom power can't be beat, especially for laptop/portable use.

USB 2.0 or Firewire ports offer the needed bandwidth.

The specs of your external card determine the resolution of your test. Pay close attention to the duplexing ability (simultaneous input/output), many units say "full duplex", but when you read the fine print, they only duplex at low to medium bit rates.

Great information, this is just the kind of things I need to know. Thanks!

Are there any sound cards that are better at testing than just doing audio? Or, are the sound cards that have a good set of DAC's good at both? I'm looking for cross-purposing or lack of that, here.

[bfish]

There are (or at least used to be) externals made explicitly for testing, but waay more expensive. Consumer cards for music usually have little need for simultaneous input and output, you're usually either playing or recording, but not both at the same time. That's where the duplexing factor comes in for testing, you're sending a signal and listening for the real-time response at the same time.

The Edirol FA-66 I use was made for multi-channel recording, and the live monitor function allows 24/96 duplexing.

Speaking of real-time, latency is a term to learn and understand how it applies to your hardware;

http://en.wikipedia.org/wiki/Latency_(audio)

With that in mind, time-sensitive data loops on Windows platforms benefit from hardware using ASIO drivers in place of the std WDM.

[Panomaniac]

One of the M-Audio USB cards will be just fine and dandy. Just be sure you get one with phantom power if your mic needs it. If it doesn't - I have one to sell you.

[sba2]

What’s the likelihood that measurements might be contaminated by a mic preamp, like this one that is designed to “add warmth to condenser microphones” ?
BEHRINGER: MIC100

I’ve been trying to figure out what’s causing some mysterious 2 millisec / 70cm / 28 inch resonances in my measurements. I’m pretty sure they’re not from room reflections.

Is it necessary to have a mic preamp between a condenser mic (ECM8000) and a sound card (Echo Indigo I/O), or would a plain 48-volt phantom power supply be enough ?

http://img819.imageshack.us/img819/2...03millisec.png

http://img444.imageshack.us/img444/4...isecnormal.png

[bfish]

RE sampling rates and connectivity:

44/48kHz sampling rate is the minimum needed to sample 20kHz audio. Your hardware needs to support simultaneous in/out (duplex) at that rate at a minimum. Most cards advertise their maximum one-way sample rates, but you need to read the fine print to see what rate they'll duplex at, it's usually half of the maximum. If the duplex rate isn't specified, move on.

Sampling rate x bit depth x2 = the data stream (in bits per second) you need to be able to run from the card to your computer.

USB 2.0 offers 480 Mbit/s, a fortyfold increase over 12 Mbit/s for the original USB 1. 1394A (Firewire, ilink) ports support 400Mbits/s, making it comparable to USB 2.0. For desktop PCs, the low cost of a USB 2.0 or a 1394 PCI card (~ $40) makes it a no-brainer. If your laptop already has the port, pick an external card that can take advantage of it.

If you don't care to do the homework before buying your gear, you can join the guys that buy some crap, plug it in, run some tests, then splatter the web with their "scientific data", or at the least can't figure out why their results are unexplainable. Otherwise, read on...

Once you're setup with your gear...

...you should test it if you want any confidence in your measurements. Why go to the trouble of calibrating a mic if the rest of the system is unknown? Fortunately, there's a simple and freeware option for detailed souncard benchmarking called Rightmark audio analyser. I use it regularly, and it has exposed connection and settings flaws that I'd have overlooked many times;

Download. Audio Rightmark

Benchmark setup is stupid easy, just loop the soundcard output back to the input and run the level setting utility. Then click "run tests", and a few seconds later you get a detailed text/graphics report of your system performance.

For ASIO support you'll need to buy the Pro version. Well worth it if you're serious about accuracy (and your card is running ASIO).

An unintended extra function is the ability to insert nearly any audio device in the test loop so you can benchmark it too.