# EQ, Mics, and REW, oh my!



## glaufman (Nov 25, 2007)

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...


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## thxgoon (Feb 23, 2007)

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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## brucek (Apr 11, 2006)

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


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## glaufman (Nov 25, 2007)

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?


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## brucek (Apr 11, 2006)

> any chance there's a less expensive preamp for the mic


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.



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


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


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## glaufman (Nov 25, 2007)

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...


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## clubfoot (Apr 12, 2007)

glaufman said:


> 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?


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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## terry j (Jul 31, 2006)

glaufman said:


> 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...


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.


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## glaufman (Nov 25, 2007)

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...


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## terry j (Jul 31, 2006)

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.


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## glaufman (Nov 25, 2007)

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.


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## brucek (Apr 11, 2006)

> 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"


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


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## glaufman (Nov 25, 2007)

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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## Wayne A. Pflughaupt (Apr 13, 2006)

> 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"...


Nice idea, as long as you have the same speakers the studio used...

Regards,
Wayne


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## glaufman (Nov 25, 2007)

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


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## terry j (Jul 31, 2006)

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.


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## glaufman (Nov 25, 2007)

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...



> My aim is to get the speaker itself as flat as possible in it's FR,


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...



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


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?



> 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.


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...



> 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.


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...



> 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.


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



> 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.


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?


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## terry j (Jul 31, 2006)

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.





glaufman said:


> 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...


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.



glaufman said:


> 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?


What I didn't say was, as best you can minimize room reflections. No, with your current setup I wouldn't take your gear outdoors either, hey it's hard enough for me to do it that I rarely bother!! (lugging the computer, three amps and the speakers outside...too much just yet. When I build the final boxes and no more changes, then yeah I might bite the bullet and do the hard yards.) In room, the theory is to put the speaker equidistant from all reflective surfaces (room and floor included) for the measurements. All that does (using a swept signal) is to allow a gated response that can get you lower in frequency (hoping the experts will chime in if they see it). However, not sure if a pink noise RTA type setup (a la DEQ 2496) will get the same benefits.

As I don't bother just yet doing 'anechoic' measurements (ie outdoors) I only have the unit correct down to around 100 hz, as I'll be manually correcting the room in the lower frequencies anyway with REW (god bless it!!)



glaufman said:


> 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...


 I've often seen people posting graphs from the Canadian testing facility, don't know where to find them personally. Some of the high end speakers have truly awful responses....not even close to being flat.




glaufman said:


> 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...


Practice??



glaufman said:


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


That's right, the 'eq' process of the deqx makes them flat, as well as correcting the phase responses and time aligning the drivers. It is exactly like the soundcard calibration done here, the speaker response (or in my case as it's an active three way) the drivers response is meaured, and an inverse of that is created and applied, the net result (like the s/card calibration) is a flat response.

Like all engineering, the better the drivers/speaker to start with, the less problems you are correcting. Even with this stuff it does not pay to have bad foundations.




glaufman said:


> 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'm not sure how to explain this, and as I've always said I could be wrong so bear that in mind.

The purpose ( to me at least) is to have an accurate stereo system (BTW I have zero interest in HT, which I _strongly_ suspect is often what is being referred to when house curves are spoken about). Hence the emphasis on having accurate speakers.

To do that we measure the _speakers only_ which ideally means an anechoic chamber, or as best we can manage. that means NO reflections at all.

The 'crazy' response we see on an unsmoothed FR posted here are the result of all the multiple reflections the room gives the native response.

Quite obviously, we DO NOT hear the sound in the same way the microphone does, we cannot pick the thirty or forty db variations between frequencies only ten hz apart in the midrange for example, it is an artifact of what/how the microphone measures. I'm not saying ignore comb filtering etc, but trying (from very vague memory) to point out that the microphone does hear differently than our ears. Something like it can't discriminate between direct and reflected or delayed sounds and some such, and no doubt more ways than that too.

Besides that, (and do this to see for yourself) move the mic say one inch, and compare the measurements. You will see very little change in the lower frequencies, but _MASSIVE_ differences in the mid and high frequencies. Which one are you going to choose as the correct one to fix??

Left ear or right ear?? Middle of the forehead?? Which out of the massively varying responses is the correct one to choose?

So we can see having a completely accurate speaker and throw it in the room, and we can measure the inroom response from the LP and see regular periodic variations up the scale, and can add 6 db here and subtract 6db there to get a smooth response (i'M TALKING MID FREQUENCIES ETC HERE)..sorry about that...but that means if we took a measurement of the speaker under those changes it would be anything but accurate, and would sound terrible. Floyd Toole is a great resource for this type of stuff, he has shown many times the vastly preferred sound is that of a smooth accurate speaker, which the example above is most definitely not.

If I have an accurate system, then it plays all recordings equally. the trouble with a coloured sound is that it colours _every_ recording in exactly the same way. That might be OK with a particular recording (the system colouration is an exact inverse of the recording colouration if you will) depending on what the drunk monkey gave us, but on the other recordings....?

At least with the deqx (and the deq as outlined earlier) I can selectively add or subtract whatever colouration I wish depending on what is being played. And this IS where personal taste may come into it...if you want more bass and less treble then go for it, who am I to say what you do or don't like?

I hope I addressed your questions!!


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## glaufman (Nov 25, 2007)

Wow... so much info Terry.... Thanks a bunch... 



> the theory is to put the speaker equidistant from all reflective surfaces (room and floor included)


OK, serious question... equidistant from flooor/ceiling... I have towers, tweeter on top, followed by two woofers, bass port in rear at bottom... I don't mind putting them on a pedestal...but... which point is better to center between floor/ceiling (center of tweeter, center of all drivers, center between tweeter and bass port) I realize I'm probably over-analyzing here...



> However, not sure if a pink noise RTA type setup (a la DEQ 2496) will get the same benefits.


Really? How come?



> Some of the high end speakers have truly awful responses....not even close to being flat.


Funny how that works. I was speaking to one particular mfr yesterday about getting graphs, and was told they don't release them because they're afraid people don't know how to read them and they'd like people to focus more on how they sound than what the curves look like... their opinion being a flat speaker doesn't sound as "pleasing" as their "jagged" response FR... Until the guy said "jagged" I figured they just didn't want people seeing a 0.5db slope in the response and getting turned off, but now that I've heard the word "jagged" I just gotta find a way to see these curves...



> Practice??


Yeah, yeah... You know, in golf, if you keep practicing the same lousy swing, all it does it get worse...
OK, Im' probably not as bad as I'm making it out to seem... I'm probably just frustrated from my latest round of trying to help a friend with a particularly terrible setup... HTIB from a MFR we all love to hate, added on a true sub, didn't have any decently engineered music to listen to, not instruments to follow, and for some reason was trying to adjust while sitting right next to the rack, with the bass module behind the glass door... not sure what I was thinking...



> The purpose ( to me at least) is to have an accurate stereo system (BTW I have zero interest in HT, which I _strongly_ suspect is often what is being referred to when house curves are spoken about). Hence the emphasis on having accurate speakers.


Perhaps.... I'll probably write more on this in another post after I go back and find that other post I read...

I've heard Toole's name many times... Where's a good resource for Toole's writings?


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## terry j (Jul 31, 2006)

glaufman said:


> OK, serious question... equidistant from flooor/ceiling... I have towers, tweeter on top, followed by two woofers, bass port in rear at bottom... I don't mind putting them on a pedestal...but... which point is better to center between floor/ceiling (center of tweeter, center of all drivers, center between tweeter and bass port) I realize I'm probably over-analyzing here...


yep, over analyzing..what, you a psychiatrist?? ha ha To take an honest stab, I guess the _mic_ would be at the point of minimizing reflections, and then the speaker is set to that. I have no real theory to back this up, but for example I position the mic midway between the tweeter and midrange (and I have them as close as I possibly can) as I have the idea that there is where the two signals merge. Is it right? I dunno, just the way I do it.



glaufman said:


> Really? How come?


Well, like in REW you hear a sweep signal, ie the signal starts low and rises up through the frequency range. Depending on the software usd (and I was mainly directing that point to how the deqx does it) the measuring is gated, ie the software follows the sweep up when measuring and only allows a small amount of time to record the response. By doing it that way (and don't take my explanation too critically, it's a very basic and poorly understood explanation) we can 'window out' any reflections from the room. So the longer we can get before the reflections arrive at the microphone, the lower in frequency we can get good measurements.

Say it took us 20 sine waves at a frequency to get a good measurement..well at 20 khz we only need 1/1000 sec to get those twenty cycles, but at twenty hz we need a full second to get those twenty cycles. That was just an explanation of why the lower we go the less accurate measurements we can get, there is nothing absolute about those figures I quoted, I haven't the foggiest what we actually need for a measurement.

RTA on the other hand, is a continuous noise stimulus that is played through the speakers, and the mic picks it up and analyzes the result. As it is an ongoing signal the mic is always picking up the direct sound AND the reflected sound, as the measurement is over a minute or so. So little point I would think in putting the speaker on stands in the middle of the room etc.



glaufman said:


> Funny how that works. I was speaking to one particular mfr yesterday about getting graphs, and was told they don't release them because they're afraid people don't know how to read them and they'd like people to focus more on how they sound than what the curves look like... their opinion being a flat speaker doesn't sound as "pleasing" as their "jagged" response FR... Until the guy said "jagged" I figured they just didn't want people seeing a 0.5db slope in the response and getting turned off, but now that I've heard the word "jagged" I just gotta find a way to see these curves...


You mentioned looking up Toole, well his stuff should be mandatory for all with even the slightest interest in sound reproduction. And in one of his papers, he does show what is important etc on the FR, almost teaches you how to read them. Try looking in the whitepapers section of Harmon Kardon, I'm not sure if they are all there, but they are floating around on the net.

then enjoy!!

I do have a social life you know, but I can't sleep at the moment so I'll tell a little story here. One of his papers examines the optimum number and placement of subs in the room, and how the FR is affected. I'd have to look it up, but no real need to go past four or something and gives guidelines for placement.

Sounded like a really good idea, so I gave it a quick try and whipped up some extra boxes and placed them around the room. Well, I hated the result.

Fast forward a year or so, and tried another trick (rear channels using the left minus right signal and delayed in time etc) and discovered something interesting...I noticed the same phenomena I hated about the distributed subs... a delay in arrival time _in the bass region _was what irritated me earlier, and irritated me with the rears. With the rears, I just didn't bother with anything below 120 hz or something, no bother.

I went back to having multiple subs (4) through the room, but each sub was individually delayed to have the signal arrive at the same time at the LP. BIG difference, and does give a wonderfully enveloping bass feel, without the irritating 'wave' feel.

Sorry to bore you, but if I'm bored and can't sleep then why not you too?


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## glaufman (Nov 25, 2007)

> yep, over analyzing..what, you a psychiatrist?? ha ha


Even worse: I'm an engineer... and I'm really beating myself up for never taking that acoustics class in school...



> Well, like in REW you hear a sweep signal





> RTA on the other hand, is a continuous noise stimulus that is played through the speakers, and the mic picks it up and analyzes the result.


Raises another question: Has anyone tried to emulate an RTA by disconnecting the injected signal from REW, piping a true pink into the system, and just using REW's listening to get a pseudo RTA measurement? Problems? Anyone know an equally cost effective (read: free) RTA program? Anyone ever try TrueRTA?



> I do have a social life you know, but I can't sleep at the moment so I'll tell a little story here.


I happen to be married, employed, renovating my home, trying to imrove my AV system, AND starting my own business on the side... so please explain, exactly what is this "social life" about which you speak?
Oh yeah, and my mother-in-law is visiting from abroad...



> I'd have to look it up, but no real need to go past four or something and gives guidelines for placement.


I've seen that THX recommends that as well, to try and smooth out bass mode variation in bass SPL around the room...

Sounded like a really good idea, so I gave it a quick try and whipped up some extra boxes and placed them around the room. Well, I hated the result.



> I went back to having multiple subs (4) through the room, but each sub was individually delayed to have the signal arrive at the same time at the LP. BIG difference, and does give a wonderfully enveloping bass feel, without the irritating 'wave' feel.


Excellent comment, I got to file that one away for future use...



> Sorry to bore you, but if I'm bored and can't sleep then why not you too?


To the contrary, Im glad my incessant questions/re-questions aren't detracting from your normal life...


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## Spridle (Sep 5, 2007)

I think it all boils down to personal preference and the nuances of your equipment and listening environment. However, experimenting with your full room response from 20-20k Hz is mandatory IMO (sub adjustment is only half of the equation!). I recently discovered REW which has helped tremendously in many ways. I EQ my subs and mains and have tried about a dozen curve variations over the past few months including flat (the worst sounding to me), academy x-curve, house curves, Wayne's knee-kicks, and rolloffs at different slopes and starting points. I finally found a curve that I really like in my listening environment that works well for all types of music and movies. My target curve is flat from 20-80Hz then rolls off 1 dB per octave through 20kHz. I like tight and balanced bass, a slightly warm, rich natural tone color, and sparkling, detailed highs. But, that may not be what you like.

Here is a hint: try to measure a system you like. For instance, I have always liked the sound of my car audio system. I measured it and, as you might suspect, it measures very close to my home theater. My personal standard for great sound is an IMAX theater. I wish I could measure that set-up.


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## terry j (Jul 31, 2006)

Spridle said:


> I finally found a curve that I really like in my listening environment that works well for all types of music and movies. My target curve is flat from 20-80Hz then rolls off 1 dB per octave through 20kHz. I like tight and balanced bass, a slightly warm, rich natural tone color, and sparkling, detailed highs. But, that may not be what you like.


hi spridle

you haven't said, but I'm assuming, that this curve you prefer measures this way from the LP??

I so, then it is a pretty well expected result. Perhaps not so much final roll off, tho I'm happy with something like that most would like a bit more treble I'd say.

That result happens almost as default when a perfectly flat pair of speakers are put into the room.

The high frequencies are easily absorbed, and as well tend to beam at the upper ranges and so are less likely to get help from the room.

AS WE PROGRESSIVELY GO DOWN THE (sorry) frequency, the room more and more helps the response and causes gain. therefore the net result we here is a natural dropoff in the high frequencies.

There is a paper by Toole (who else??) which shows this in graphic terms. We have the sum of two things, the curve of the natural response (which we want flat so that the speaker is accurately reproducing all frequencies equally) and then the next curve which is the power response of the speaker (what the speaker sends into the room), the two of which gives us the natural 'tilted down at the high end' frequency response.

Greg, maybe if you see this, it might be a good idea to change/modify the title of the thread to reflect quite a bit of discussion of full range eq etc?? Would help some future browsers.

What is interesting is just how few are joining in the topic...it backs up what i've learnt elsewhere that eq full range is still regarded as taboo, or uninteresting or whatever. yet, over here in Aus when I offer to show them what it does so they can make up their own mind,...no interest. go figure. yet they will come out with all the theoretical 'why nots', all the prejudices of decades yet will not even challenge their preconceptions by audition. oh well.


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## Spridle (Sep 5, 2007)

Yes, my measurements are an average of 3 main seating positions. 

I'm really not a fan of EQ on the mains, but I've ended up there with good results. I'd prefer to do more with treatments and positioning, but there is not much I can do because of my room and built-in entertainment center. With my subs and mains, I have used EQ very sparingly. In fact, after using REW for a while, I have gone from 10 filters on my sub to get a perfect curve fit to using only 3 filters to knock off peaks and it simply just sounds better even though the measured response is not exactly on the target line.

I have played with the treble tone control and speaker crossovers and have settled on the current setting which give me the 1db/octave roll-off. Any more treble and it starts to scream, isn't warm, and doesn't sound natural. Another factor is that my mic may not be calibrated accurately at the high end but I think it is in the ballpark.

As far as full frequency room response measurements are concerned, I think it is very important for overall balance of the system. Even without EQs on the mains, looking at the full range gives you an idea on balancing the subs with mains and using tone controls or treatments to shape the system. Your ears are the best test for tuning, but a full spectrum visual is extremely helpful when tuning and makes it a lot easier. 

Hopefully, people will start posting more full frequency graphs on HTS. Here's my latest and greatest full range room response (1/1 octave smoothing, main speakers and subs, average of 3 main listening positions).


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## glaufman (Nov 25, 2007)

Wow.... great looking curve Spridle...
Terry, I'd be happy to take that suggestion of changing the thread name, just not sure how to do it...
I'll be very happy when I get some measuring equipment and see what my setup is actually doing... with the exception of low end, I actually think I have it tuned pretty well to whatever my personal preference is... someone who listened suggested boosting the treble a few days ago because he couldn't hear the attack in some cymbals, and I spent an hour trying to explain it was being heard as the artist intended, and boosting it for this disc would make it too bright for most other ... to no avail... he accused me of wanting it to look right on a scope instead of wanting it to sound nice... so people definitely run the gamut...
Another friend was over last night, my partner in crime actually, and kept commenting on how well the system sounded for stereo, but also commented that he prefers his own system for HT... we were able to reach a middle ground in figuring that's the way it's supposed to work, as mine is 2 almost-full range towers in front with no sub, whereas he went the satellite/sub route...
I find what Spridle said interesting about allowing deviation from the target line sounding better overall, for 2 reasons: 1, it obvviously means less eq'ing, which I imagine means less group delay problems, and just less processing of the signal overall, and 2, it makes the response slightly jagged, which having spoken to at least one speaker mfr, they said they didn't provide response curves because (and I'm paraphrasing here) they think people will balk at the jaggedness of their curves, even though they think their speakers sound great that way, as opposed to seeing what we all at least THINK we want to see, a nice smooth flat line... BTW, I agree with them on one point, I DO think their speakers sound great...
I'm hoping, even though I'm sure it wont' be the case, that when I get a measurement stuff in another month or so, it'll show that whatever work I've done to ear on my limited eq has in effect, rather than colored it per se, corrected for amp (or speaker, or whatever, just not room) response things I didn't know were there...


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## glaufman (Nov 25, 2007)

I also wonder, in terms of being accurate vs sounding good, and noting that the two should not be mutually exclusive but in a perfect world where the "drunk monkeys" aren't so drunk after all, is what kind of signal we should be looking for a flat response to? As in...
When we talk about scans in REW, I think we're talking about using REW to inject the test signal, and I'm always assuming it's test signal sweeps all frequencies with the same output level (not sure if that's going to be equal voltage (peak/rms) equal power, etc... for now I'll assume equal voltage, which should mean that a flat amp should translate that into flat power? In which case that's analgous to white noise? And wouldn't it make more sense to see how we respond to pink noise? Anyone with these pretty REW curves ever take a graph with pink noise going through their system?


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## brucek (Apr 11, 2006)

More people should read and re-read this line......

_I have gone from 10 filters on my sub to get a perfect curve fit, to using only 3 filters to knock off peaks and it simply just sounds better even though the measured response is not exactly on the target line._

:T

brucek


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## Spridle (Sep 5, 2007)

One thing that stands out with only using 3 filters on my sub as opposed to 10 was that the transition area between subs and mains is very smooth and I only have to reverse the polarity (180 degree phase shift). Before I was getting dips in the transition area that I couldn't fully fix even with varying the phase in 5 degree increments. I was also hearing some strange subtle bass sloppiness in certain songs with playing frequencies around 70-150Hz. With 10 filters, I think there must be wild phase shifting going on.

I also have an AudioControl SA-3050A 1/3 octave spectrum analyzer which uses pink noise as the signal. When I plot these points, SPL levels match up almost exactly throughout the spectrum to a smoothed REW curve. I use the AudioControl mic with REW with a calibration file I created.


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## Wayne A. Pflughaupt (Apr 13, 2006)

glaufman said:


> …someone who listened suggested boosting the treble a few days ago because he couldn't hear the attack in some cymbals, and I spent an hour trying to explain it was being heard as the artist intended, and boosting it for this disc would make it too bright for most other ...


Simple tone controls will do the trick without messing with overall system calibration. I use mine all the time when I run across treble-challenged programming and the reverse (which seems to be less common), and set them back to flat when I'm finished. Of course, I have simple knobs for my tone controls, which makes access quick and easy. Might not be the case with more recent receivers...

Regards,
Wayne


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## atledreier (Mar 2, 2007)

brucek said:


> More people should read and re-read this line......
> 
> _I have gone from 10 filters on my sub to get a perfect curve fit, to using only 3 filters to knock off peaks and it simply just sounds better even though the measured response is not exactly on the target line._
> 
> ...


I use one (1) filter to tame my 30Hz peak... :yay: Now if only I could tame my inner wall flexing 5mm whenever T-rex walk by, I'd be happy. There should be EQs for walls too!


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## brucek (Apr 11, 2006)

> I use one (1) filter to tame my 30Hz peak...


Yeah, I have been an proponent of less is more for quite a while now. I use to have a perfect response that absolutely tracked the target line. It used just about every filter the BFD had to offer. It simply didn't sound that great.

Then I decided to use REW to measure at multiple positions and place all the responses on the AVERAGE tab to see the over-riding trend that all the results shared. I used the Average button to create a new response from all those results. I created my filters from that average response (REW allows this) and created only two filters to get rid of the major resonance. I then only used one more filter at the crossover area. So I've been using three filters for the last while, and it sounds much better, and in any position I sit.....

brucek


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