Tools for measuring frequency response of speakers in a room

What are people using for this?

Our room tuning guy moved to the east coast and will now cost us several $$K to get the guy and his gear and his hotel room and a car.... We have used this guy for 20+ years.

Watching him work for the past five years, he seems to have a pink noise generator band limited to center frequencies that correspond to those on a graph, then uses a meter and plots a graph that way. He used three microphones, I believe are omni in a triangle formation in the mix position.

In the past, I have "tuned" the room immediately after replacing all the drivers by listing to program material that I know very well and tweaking on the EQ's before the professional comes in. (He says I get sorta close, but he might just be trying to flatter me)

I'm just wondering what a good (modern, or semi-modern) scientific method to make measurements, the equipment required, recommended reading and any advice I could use for the subject.

Regards
~B

here is a funny picture of a former co-worker wiring up a horn in our Studio A.




and some DIY x-overs I made when we added ultra high frequency drivers to the mains.




:grin:

Ben... your a crazy Biatch. Nice crossover... custom wound inductors there?

That picture reminds me of what happened to Dr. Emilio Lizardo in his initial and tragically abortive and invasive attempt at dimensional transport with the Oscillation Overthruster.

Was he any relation to Emily Lazar?

BTW - Rather than just make a wisecrack, I can tell you that, for a room of your calibre, you'll want B+K mics - not cheap. There's an Earthworks mic that's more affordable, but B+Ks are regarded as the daddy: http://www.earthworksaudio.com/27.html

Be prepared for open-wallet surgery when you see the B+K price list.

I can't see why, with the right mic selection, you couldn't get by with a fairly basic measurement programme such as SpectraFoo etc.

Justin

for measuring rooms @ westlake we had a urei model 200 plotter and a warble tone generator. We would sweep the up and down and ploot each speaker on the stereo field Then make adjusments on the white eq's attached to each main. We would get so spot on that we would plot each speaker component by itself so that each woof,driver,etc,etc was as matched to the one on the other side. IF a speaker started to go bad we would replace it on both sides again matching the parts as closely as possible. At my current work we have an audio toolbox 3 which has it's own test mic and so forth. It works quite well. It's no AP by any stretch but it works well for alot of our needs.

Lots of people swear by Bob Hodas. I have been into rooms he has done. They were good but I can't say that with 100% as I was familiar with the Mayer mains that were set up.

His website

http://www.bobhodas.com/

Thinking about it, this is going to be an area where chops have infinitely more importance than gear. The top guys have university degrees and a shed-load of B+K gear. I was told by one London-based acoustician (someone with a degree from the right uni) that he usually goes on a job with around £100K's worth of equipment. If you have the theory and the gear, well, then you do a good job! Having said that, I bet that a top acoustician could probably do a better job with a cheap RTA and an SM57 than a non-acoustician with all the goodies known to man.

Acoustics must have many centuries' worth of research to draw from above other audio-related fields. The Romans had pretty mean acousticians from what I understand.


Justin

Was always told a real room designer shows up with a flash light a tape measure and a reference CD to measure/eq a room.. The pseudo room designer shows up with lots of fancy computer to do the same.

I believe there are a few ways you can go about it.

If you want an FFT measurement of your system, you can go with Smaart (www.eaw.com) . It is what most people are using. I've tuned a bunch of live sound systems with it as well as some control rooms. Is it the perfect tool. Probably not, but I've had amazing results with it plus M23 or M30 earthworks mics.

If you want to get a little fancier, look into a TEF system, (www.gold-line.com),
It uses TDS (Time-Delay Spectrometry) for frequency reponse measurements. You can get very precise with it. It costs a bunch of money, and I'd think twice before buying it, if you are only going to be measuring one or two rooms.

The studios where I work, with Dynaudio M2s, were tuned with Smaart by another coworker and the results were pretty good. The M2 were passives, so there wasn't much you could do about individual components, but he got them to sound pretty close.

Hope it helps.

take care
Gil

I am an application engineer for B&K right down the street from you and might be able to hook up rental or demo equipment.

The local sales guy and I are actually putting together a system that would map the frequency response of a control room graphically - essentially to determine size/response of the "sweet spot".

Shoot me an email at tony(dot)spica(at)bksv(dot)com and I'll see if I can help you out at all. I just moved to LA, so I don't have a full assortment of my own equipment at the moment, but will in the coming weeks.

-Tony

:thumb: I've never messed with one, but Smaart is pretty well regarded for dialing in live sound rigs.


JR

For starters, I think I might rent the Earthworks mic and use the Smaart 6 demo that is available online. The thing I don't like about that system is the sound-card variable. I'm sure the software compensates for anything the card would add to the test signal, but something stand alone and purpose built is much more appealing.

I looked into adding DSP option to our Audio Precision to use the MLS function but it's way out of the budget and I can get a MLSSA rig much cheaper.

I am an application engineer for B&K right down the street from you and might be able to hook up rental or demo equipment.

Click to expand...

Cool! I was just digging into the shop filing cabinet and found a B&K catalog from 1983 with some cool stuff in it. I thought I could find some of that stuff on eBay on the cheap, I was wrong. I'll shoot you an eMail when my brain gets back from Burning Man.

The local sales guy and I are actually putting together a system that would map the frequency response of a control room graphically - essentially to determine size/response of the "sweet spot".

Click to expand...

Interesting. You can beta test here! :grin: This would be especially useful for setting up 5.1 monitors?

~B

By the way, I have no idea what I'm getting into.

~B

My measurement setup is very loose, but good enough for the girls I go with...

I just use a C414 and Audition's frequency analysis.

Combined with: tape measure, a mirror, a flashlight, and a calculator to make sure everything is sympatico.

I did a recent install and the acoustician found big and small issues with a new space using Electroacoustic Toolbox, the older version available for $99 here
http://d-softwarehouse.com/software/mac/other/electroacoustics_toolbox_1.1_mac.html

He had a small Maudio box and a single Earthworks as the front end to a mac.
Your system is already tweaked, so perhaps you can maintain it with existing AD hardware, the best house mic, and ET?
Other acousticians:
A NYC guy, now retired used a White RTA with B&K mic listening to pink noise, moving it in the stereo field.
George Augspurger uses the same rig, but with a stationary mic. A Lionel Richie CD is the final voicing source.

With anything, mark the existing settings before you start! Anyway, you are starting with a tuned room, so you will not get into any of the "new room" problems like going for electronic compensation rather than mechanical/physical room changes.
Mike