Tips on making corrective eq IR

musicianof1

musicianof1

Inspired
I'm looking to make a corrective eq IR for an RCF 312A. How does one go about this process? What all is involved? I have a room calibration mic but not sure what freeware woud be useful for this. Do I send a 1k or sweep tone out of my DAW into the RCF and use the mic to capture the results back into the DAW? What comes after that?

Any help would be much appreciated.
 
There are several approaches you might take for this.

The Verve 12Ma corrective IR was basically created by EQing the speaker by ear until it sounded "right", and then creating an IR from the EQ. To do this properly you have to understand where EQ is useful and where it is not, or at least have a very good ear. EQ alone may not get you close enough to your goal.

You might want to download a copy of Room EQ Wizard from the REW forum.

If you send a sine-wave sweep through the speaker and capture the results, you can deconvolve (use Voxengo Deconvolver) those results with the original sweep to create an impulse response. If you stop there you have a method of making an FRFR (well, a better FRFR) sound like your RCF, which is the opposite of what you are trying to do. What you need is the inverse of that IR, which will make your RCF sound like a better FRFR, or at least that is the idea. There is a program called Signal Wizard that an do this, at least in theory. The program itself is free, but the hardware that goes with it is not, and it's not clear whether you actually need the hardware for this function. I played with it a bit and didn't get anywhere, but it might be worth a look. THIS PAGE has more information. Let me know if you figure it out. Really.

It seemed simpler to me to just write a program to create an inverse IR than trying to figure out Signal Wizard and do all of the data conversions required. I've made a good start on it, but have no idea when it might be finished.
 
Thanks for your quick reply LMO. I'm thinking of doing the following: Send a sweep into the RCF and capturing it in Logic. Run that captured file into an analyzer or room eq software and seeing where the definincies are. Next, I'd make the corrective eq in Logic and export the eq'd sweep out of logic as a Wav file 24bit 48k. Run that thru an IR utility and I'm hoping that would do it.
 
The 312a is a non-coaxial 2-way monitor, right?
That will make it a bit more difficult to work with than with a coaxial speaker...
You'll have to mic it from several positions and use an EQ that works best with all of them.
Also, if there are phase problems in the wedge EQ won't help at all.

What does the 312a sound like to you?
Why do you THINK you have to use corrective EQ for it?

With the Verve 12mA it was obvious to me as it sounded way off every other systems I have and had...
 
musicianof1 said:
Thanks for your quick reply LMO. I'm thinking of doing the following: Send a sweep into the RCF and capturing it in Logic. Run that captured file into an analyzer or room eq software and seeing where the definincies are. Next, I'd make the corrective eq in Logic and export the eq'd sweep out of logic as a Wav file 24bit 48k. Run that thru an IR utility and I'm hoping that would do it.
Click to expand...
If you are just going to look at the frequency response, why not just record white noise through the RCF and run that through the spectrum analyzer in Logic?

BTW, where are you in Seattle? I'm just east of Redmond.
 
@Merlin,

The 312A is a powered non coax speaker. I've been using it for almost a year and it's pretty good on gigs but when I'm rehearsing and it has to carry the room the top end is about all you get 10 feet out from the speaker. I'd like more mids and less top. Low end is more than sufficient. I would think the low end would be weak if it was a phase issue but I'm not an expert. Anyway, I'm just looking for a way to flatten the response of this guy until I can get the NX12-SMA.

I also attempted to wire the tweeter out of phase to see if I liked it any better but could not easily pull the two wires out to reverse them. They are REALLY clamped down.

@LMO- I'm over where Mill Creek and Bothell intersect. Was just over near your area at the town center over the weekend. It's nice there.
 
I use 310As in my PA as monitors, and I used my speaker processor to create an EQ curve for them, which flattens out the response quite a bit (helps a lot with controlling feedback). Here's what the EQ looks like:
RCF310GEQ.jpg


If you want to bring your 312A over we can run the program on it and see what it produces.
 
@Merlin- I have used the global eq to shelve out past 6k and it's tolerable. I'm thinking I need to add more 2k-ish in there though. I've read a few different testimonies where that frequency was really lacking in various powered monitors and I can see in LMO's graph that it's boosted there too. I just thought maybe a corrective IR might be better since you can cut and boost frequencies with more precision.

@LMO- Extremely generous and tempting offer. I am going to see what I can muster up and if I can't get something useful, your solution might be a big help.
 
The Voxnego website says it's Deconvolver plug can do "•Inverted impulse response creation"

Not sure if that would be the type of cancelling IR being discussed here or not though.

Richard
 
So it dawned on me that I could download the spec sheet of the 312A online and take a looksie at the freq response they already measured. It's showing me some pretty handy info and as I suspected boosting at 2k made a remarkable improvement.
 

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  • RCF 312A Spec Graph.jpg
    RCF 312A Spec Graph.jpg
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Last week i made the same what you want to do, but with an DB opera M12. I took a reference mic and sweeped the Db opera in REW V5. Therse an exportfunction in it, where you can you can export thecorrected Filter. Than i converted the .wav to .syx with the ownhammer tool. This "Cab" is now at every end of my presets. It sound much better now, because theDb opera had some low frequencies between 1&3kHz.

If your intrested in it, i'll make a tutorial for you

Sent from my X10 using Tapatalk
 
Can you post the corrective .sys file for the Opera m12?
I'm using it onstage sometimes, so I'd like to try it out.
Thank you.
 
cobhc999 said:
Last week i made the same what you want to do, but with an DB opera M12. I took a reference mic and sweeped the Db opera in REW V5. Therse an exportfunction in it, where you can you can export thecorrected Filter. Than i converted the .wav to .syx with the ownhammer tool. This "Cab" is now at every end of my presets. It sound much better now, because theDb opera had some low frequencies between 1&3kHz.

If your intrested in it, i'll make a tutorial for you

Sent from my X10 using Tapatalk
Click to expand...

A tutorial would be awesome.

I'm just getting into REW and have both a reference mic and SPL meter with CAL files.

Richard
 
Stupid question here. Couldn't you send white noise through the monitor, mic that with the calibrated mic and then EQ it until you get a flat response? Do this from a couple mic placements and try to average it out and I would think that you have a ballpark EQ at that point. Then create an IR based on that EQ.

Then again maybe I'm just not tracking here.
 
Thank you for posting this. I'm looking forward to trying it out.

So suppose one could use an existing microphone he had, like a Microtech-Gefell M297 wide cardioid, or go out and buy a $55 Behringer "measurement microphone." Would one REALLY be better off with the Behringer?
 
if you get the .cal file with the Behringer from a decent source, REW can load the .cal file.

That I think would be a flatter response and more accurate than a M297 for the purposes of audio measurment.
 
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