EQ, Mics, and REW, oh my!

Hi there... one thing that's always bugged me is getting my eq's set just right... and not just on my system, but friend's as well, where I'm not there every day to tweak here and there over time... I've been looking for an easy way to do this quickly, and I'm not just talking in the sub range, but all the way up... so I stumbled upon REW, and am condsidering which equipment to pair it with... I'm on a limited budget, I want to get some video equipment also, and my partner in crime already has an RS digital SPL meter...

I notice the REW literature that the RS is ok for "low frequency" measurements, and I see the correction file only goes up to 200Hz... Should I assume the RS meter shouldn't be used for measurements above 200Hz? Or is it's curve sufficiently close to C weighting above 200Hz to not need correction? In which case, what frequency can it be used up to?

I guess the same questions apply for the Galaxy (the correction file only goes to 200Hz?) and the Behringer (correction file goes up to 20kHz...)...

I'll have more questions I'm sure, but I'll start here... thanks in advance...

The correction values only go to 200hz because most of us use them for subwoofer calibration. I think the meter is pretty accurate up to 10khz, though I could be wrong.

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Goon's Theater
LLT Build Thread

If you want to do full range measurement you really should get a mic and preamp like the ECM8000 and the XENYX 802.

The RS meter isn't considered accurate above ~5KHz....

There's little you can do with EQ / Traps / room treatment above that range anyway, so why not give the RS meter a try.

brucek

Well, truth be told, if I get what I get now, I can get it as gifts from the family, but if I don't have to, there's other goodies I'd rather get... such as light meters and the likes...

If there's little that can be done over 5k, why do eqs come with that capability?

I've been trying to determine what sound card to use, I'd like it to be external, was looking at Soundblaster Live! as recommended by REW literature, but I can't tell if it has the inputs I need... it doesn't look like the one in the picture in the REW docs...

Also, any chance there's a less expensive preamp for the mic, perhaps one that does as good a jobn on the preamp but doesn't have the mixing capabilities that I don't really need?

My buddy has a mixer/preamp, but he doesn't think it has an XLR input... is there an appropriate BALUN that can be used, or is that a bad idea?

In this post, another member found one a bit cheaper, but I have no experience with it. Maybe wait and see if it works for him.

There are external soundcards (M-Audio) that come with a built in mic preamp with phantom power. They seem to work OK and a nice all in one solution.

When it comes to the preamps you have to be able to cancel their response inadequacies by adding their inverse response to the soundcard file, so there needs to be appropriate inputs and outputs to do so.

When I'm talking about EQ I meant parametric EQ to reduce modal resonance (15Hz-100hz). Yeah, you can always alter large areas with low Q filters in graphic type equalization or tone controls.

brucek

I guess that's what I'm really interested in... not that I'm not interested in the low end, but there's plenty of info on that out there... what seems to be lacking in info is help on setting the mid-bass up to the highs... I thought I'd be happy once I got an RTA and flattened the curve from pink noise, but I just read on the forum that people don't like the way that sounds, so I'm still looking for at least a quasi-scientific method... When people hear my system (which has been tweaked by ear every month for the past 7 years they ask me to do theirs, but I can't continue tweaking their system all the time the way I do mine, so I need a relatively fast, repeatable method to get relatively close in a few hours time...

BTW, REW it seems won't take spectral measurements form an external source, just from it's own sweep generator? For instance, I'd like to see the spectral content of the room when feeding broadband pink noise...

I can recommend the M-Audio Buddy mic preamp. As brucek recommended add it to your sound card loop back calibration to take into account any response variations, from what I remember it was flat. Paired with an ECM8000 you will be able to do full frequency measurements.

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My HT pics

Out of curiosity, just how do you do the higher frequency eq?? ie what unit etc.

I've written up in the past how I do it with something like the DEQ 2496, and the methodology behind it.

I like the result, can't speak for others. Yet I do do it a bit differently than most, and in any case the DEQ is perfectly well able to set your own desired curve, so it's a moot point.

The main reason (I suspect)that people don't like the result of full range EQ is it's usually done from the LP, and so you are trying to correct the room. won't work, and as Bruce always says, any non optimum FR caused by the room in the higher frequencies is best handled by room treatment.

Nothing wrong with correcting the speaker as opposed to the room.

Now we're talkin... well in this case, I'm just using the eq built into my Sony STR-DB940... 3 band, setting corners/centers... (does that make it parametric?) but one particular friend has what I think is a Teac, 9 or 11 band... I have no problem admitting that much is better off corrected with room treatments... but I do believe in amp/speaker correction... (and perhaps a little contouring)
I'd love if you could point me towards your methodology...

OK, will have a hunt later tonight, hopefully I can find it so I don't have to type it again, tho (for you ha ha) I will if I have to.

Thanks. I'm looking forward to it. Interesting aside:

Interesting note I'd like to throw out there and let people sound off on to hear a bunch of differing opinions:

I have a friend who insists on running his system with eqs completely flat, because despite how flat and un-pleasing it sounds, in his mind it's "what the author intended"...

I'm all for achieveing the mood that was intended, and I know better than to bring up the bass guitar with eqs if they just didn't want it that prominent in the studio, but what's wrong with adding a little contour?

I sincerely hope I'm igniting a firestorm on this because I really want to see some heated debate.

That flatness will be perceived by the human ear quite differently at lower volumes as it will at high volumes. The flat EQ only works at one specific SPL level........

brucek

So, that would be in favor of adding alittle contour, yes? But logically, even that contour would only sound right at the SPL it was contoured at, yes? Which basically means: apply the contour at the volume level you're most likely to listen to the most?

Any differences in opinion between music mode vs movie mode?

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My thoughts exactly.... ok, not exactly, you were much more eloquent...

Hi Glauf

I may as well just do a quick write up, and you can decide what you want to do with it. My only concern is that I may come across as if I'm some sort of expert, bear in mind I'm not OK?

Also, not sure how much you can do with the eq available to you, but at least you can try it and see.

I would do a bit of a bigger 'how to' if you were going to use something like the DEQ 2496, it can be a bit intimidating at first, it took me a while to work it out. Not sure how much interest something like that would be as a general rule at the shack, most people only want to do their subs. Fir anyone who wants to do their subs AND 'correct' their mains, then go straight to the deq and forget the rest. From what I can gather it is a much higher quality unit anyway, has heaps of processing power to do all the bass as well as eq the mains, and has umpteen presets for varying recording quality, or maybe even for low level listening (ie set your own Fletcher Munson curves if you wish).

this is how (and why) I do it. Like your earlier question above, I hope that the (far) more knowledgable guys will chip in on the 'theory', I certainly don't claim to know it all.

Leaving aside the bass correction, which is admirably covered in detail here, if you wanted to go further the here is my approach.

My aim is to get the speaker itself as flat as possible in it's FR, and so measure the speaker from say one meter (varies according to the speaker, but the main thing is to measure at the point all the drivers gel, if you get me). With the DEQ you can choose to use it's automated FR shaping, and if you do then I go for flat. As this is not a DEQ writeup i won't go into detail on that.

the reason?? Well, as I understand the definition of hi-fi, we want an accurate flat and hence uncoloured speaker that reproduces accurately the signal given to it. It has never made much sense to me that some people spend oodles of money further back in the chain for accurate source, dacs etc etc and then say 'who cares what the FR is like on the speakers..??' why spend heaps of money for accuracy elsewhere for it to be 'undone' by the speakers?

Your method, depending just how much control you have with yur 3 eq points, would be to do a full range measurement (with something better than the RS meter) and then, trial and error, add the available EQ points and remeasure. Always start with the largest deviations (ie low q on the equaliser) and work your way through as far as you can with the points available to you.

The goal, as accurate a transducer as you can get.

What you get in the room after that is another matter!! But that is the nature of the beast.

In my situation, regarding your question above, is that my speakers ARE flat, very much so ( I use the deqx) and so that is always my first point of call, as accurate a reproduction as possible.

However, as most of us know, not all recordings are good!! With the deqx it is then a trivial matter to 'boost/cut the bass as needed', add or remove treble, or again fiddle with the midrange all from the LP (using the remote) to suit whatever recording I happen to be listening to.

So, I accept your friends argument, but bear in mind I always come from the security of knowing that my speakers ARE flat to start with.

With the DEQ, you can (with a bit of fiddling) have twenty or more different settings stored, covering all those permutations above, and recall the setting depending on the recording.

In addition to having flat speakers, then of course all the bass eq (as outlined on this forum) can be done too.

Regarding EQ in the room, I personally agree 100% with the comments made earlier, above a couple of hundred hz it's a bad idea. Room acoustic treatments are what is needed.

Here is an article by Rod Elliott covering this http://sound.westhost.com/articles/dsp.htm , and from memory I think he asks that the whole site gets linked, so here it is too http://sound.westhost.com/index.html, please take advantage of perusing the whole site, it is a valuable resource.

Funnily enough, in the very long Beyond the Ariel thread on diy, Lynn Olsen said exactly the same thing today

As posted previously, I don't believe in using EQ to correct for room abberations above 300 Hz - above that frequency, I'll only correct for deviations from the drivers themselves, and preferably in the passive domain using the crossover. Below that frequency, though, EQ on a per-channel basis is a good idea, provided boost EQ is kept to a minimum (because it stresses both amplifiers and drivers, and reduces system headroom).

I don't usually go above say two hundred hz myself, but you can always try it and see.

So my 'method' outlined above (which is unashamedly taken straight from the deqx method) bypasses all that, and gets me as accurate a speaker system as possible.

If you are even vaguely contemplating bass eq as well (as all of us here most assuredly strongly recommend) then put a serious thought at getting the DEQ 2496, as you are at least interested in full range eq as well.

Thanks Terry... I'm with you on about half of it, but another half got me confused again... bear with me, please, although I've been listening and palying around with equipment for years, I'm really quite the newbie... anything I've omitted here just assume I completely agree with and (I think) completely understand...

Nothing wrong with making that the speaker/amp/preamp combination, right? Trouble is, I read the sticky thread somewhere on here explaining you want to set a house curve since the sound sounds, well, flat, when you adjust it to be a flat response...

Here's where the real confusion starts to set in... I understand you won't hear exactly what the speaker is putting out due to the room response, but then how (or is it more appropriate to ask where) do you correct the speaker if not in the room? Or, are you saying that by measuring the speaker 1m away (as opposed to the LP) you can get a much cleaner measurement of what the speaker is putting out with less (perhaps even negligible) effect from the room acoustics?

Just out of curiosity, anyone know where one might be able to attain measured response curves on different speakers? Hardly makes sense to pay to rent a good anechoic chamber, but if the speaker manufacturer doesn't provide? No, I'm not going to move my setup into an open field just to get this, I'm just curious...

AHA! Believe it or not, this is one of the areas where I'm asking for help... follow me on this scenario...
I have a system. When I set the system up, I spend many hours over many days listening to my favorite recordings and tweaking the eqs (in the days when I really knew nothing and therefore completely ignored response curves and room acoustics) until I thought it sounded about as good as it could be gotten. Very proud with myself. I had a friend over, and him being a big audio guy, I want to fish for the compliment of how good it sounded. So instead I asked him if as long as he was there to see if he could do better. In 5 mins he had made such drastic improvements with only the eqs that I couldn't believe my ears. I had never heard a system play a reording with such clarity. Ever since I've been looking for a way to train my ears to be able to do the same things. This scenario repeated itself several time over the next few years... I'd ask this guy to train me, but we're no longer friends... I obviously can hear the differences, so I wonder what I'm missing that makes me unable to achieve the sound that I prefer...

Meaning they have a flat response themselves, or you've made them flat with eq?

Again, confusion sets in. Where else are you going to eq but in the room? Do you mean don't cut obtrusive frequencies instead of treating the early reflections? OK, makes sense. Or is there something more to it? Even in the lousiest acoustic environments I've been in, I cna hear an increase in treble when the trble is turned up, so what exactly is the problem with doing that?

I just noticed the Greg alias, I much prefer names to 'silly internet handles'

so

Hi Greg

As I say, this is only MY cobbled together methods and works for me, and psychologically because I have my own ideas on what hi-fi should do that could be why it works for me. You could be different.



Well, I guess it automatically follows (certainly with the deqx, less so perhaps with the DEQ, and maybe even less so again with your three eq points) that when we correct and make the speaker flat, we have also by default made all the preceding parts flat...or more accurately the entire chain has been made flat, which to me is the aim of hi fi reproduction..the ability to accurately reproduce what is on the recording. What is on the recording could have been mixed by a blind and drunk monkey for all we know (and often is??) but nonetheless we throw ourselves on the mercy of the recording engineers.