DRC, with open baffle speakers

[otto88]

I’m planning an XO that's PC based, so I’ve been reading through this http://www.diyaudio.com/forums/multi...how-pc-xo.html
It makes sense to allow for flexibility & future uses. at this stage choosing the sound card (almost picked the Saffire PRO 40)

In particular, ShinOBIWAN and ewildgoose’s experiences have convinced me that after the XO, to minimise room problems I’ll want to add/ try DRC.

A good summary of the benefits of DRC from that thread are here:
http://www.diyaudio.com/forums/multi...tml#post823319

I hope/ expect that with very good drivers (and source and amplification) and a *lot of time spent fine tuning, the speakers will be really good.

However the speakers will be open baffle, which have less room interactions.

How much benefit would/ does DRC provide with open baffle speakers?

And what “extra” do you need include in the sound card spec, so it handles DRC? DRC say on left, right, and centre: 3 extra inputs and outputs?

[otto88]

(Reading on) ShinOBIWAN found after using a Behringer EMC8000 mic "fairly poor"

"I personally wouldn't use DRC without a top notch mic unfortunately"

I'm also in process on a similar $ (cheap) mic, the Dayton EMM-6, but properly calibrated from
Cross·Spectrum - Calibrated Dayton Audio EMM-6 Microphones for Sale

The Premium-Plus is measured individually for:
• on-axis response
• frequency response at 45° and 90°
• polar response (for measuring room acoustics)
• and sensitivity and noise floor

Is a EMM-6 adequate for DRC, if properly calibrated?

[catapult]

Is a EMM-6 adequate for DRC, if properly calibrated?

Yes IF your measurement software can use the calibration file supplied by CSL. Hopefully your DRC software will be able to import the corrected impulse response or frequency response from software like HOLM or ARTA that can use the cal file.

[otto88]

Thanks catapult, I suspected that: calibration is the key.

I haven’t yet chosen the DRC software, but importing the corrected response should be a prerequisite.

[Reverberant]

Originally Posted by otto88

Is a EMM-6 adequate for DRC, if properly calibrated?

This is Herb from Cross-Spectrum Labs, a poster asked me to weigh in.

As catapult noted, you first have to be sure that whatever DRC package you use can accept mic calibration files. There are a couple that do (REW comes to mind).

As for the measurement itself, most mic cal files are for using the mic in an on-axis configuration, where the signal is assumed to be coming straight on along the long axis of microphone (mic pointed toward the sound source). In room acoustics applications, there will be direct sound from the speakers, but there will also be sound waves from reflections arriving at random directions to the microphone. Since 1/2-inch microphones are not omni-directional at the highest frequencies (above ~ a few kHz) using the on-axis correction file could cause some problems at the higher frequencies.

That's not to say that you can't get good data using the on-axis cal files, it's just that you may (and I stress may) have to work a little harder at it. I started offering 45/90-degree calibrations for room acoustics applications to avoid the problems some of these problems. But you can certainly experiment a little with on-axis cal files and get perfectly acceptable results.

One thing about DRC measurements is that you may find that even with the mic kept in the same spot, that you get different results every time you run a measurement. One thing you can do to try to avoid this is spacial average - you can take measurements with the mic in different locations in the listening area and then generate an average of the resulting curves, or (my preferred method) put the mic at the end of a long stick and slowly move the mic in horizontal and vertical circles around the listening area during the sweep.

HTH

[gainphile]

I've heard DRC few times and including DEQX2496 and all leave me cold. The resulting eq is simply unnatural to the ears. I think this is because you can't eq time domain with amplitude correction.

The best speakers I've built (OBs) were the ones measured flat in freespace (outdoor)

But I don't mind correcting one or two peaks in the bass region for room modes.

[StigErik]

I agree with gainphile here. In severe cases DRC will improve things, that is when the speakers are very far from flat or the room is really bad.

My approach is to correct the *speaker* with EQ above 2-400 Hz or so, and tailor the speaker to the room with EQ below 2-400 Hz. That could be named "manual DRC"

[otto88]

Yes, bass and esp low bass is where most of the problems are.

I think the DEQX2496 is probably DRC built to a price; good value, but with some compromises. Maybe there’s something about it’s processing, which creates that sense of being unnatural.

The time domain? Good point, I don’t know yet if software eg Bidule also works in the time domain??

What DRC did you try on the OBs, the Behringer?

"manual DRC" may give 80% of the benefit, for 20% of the complexity

[StigErik]

Bidule cant do much on its own - it needs DSP plugins. If you use an impulse response convolver you can do things in the time domain also.

Behringer DEQ2496 is very limited in its EQ capabilities - 10 parametric EQ's is simply not enough. Its automated EQ is .. well... no good at all! Better to set it manually assisted by proper measurements I think.

Proper EQ software can do much more - the number of EQ points is only limited by computer CPU power. Sofware EQ can also be Linear Phase, which none of the hardware EQ boxes can do.

[otto88]

I didn’t at first see Reverberant’s post

(gainphile, was the mic used properly calibrated for DRC?)

REW has quite a following, with its own forum REW Forum at Home Theater Forum and Systems - HomeTheaterShack.com - could well be worth trying.

I can see why a sweep of the listening area would be good.

Though why with the mic in the same spot, might you get different results every time you run a measurement; do they vary much?