# What's your ideal frequency response curve for a car?



## dbiegel (Oct 15, 2006)

I'm struggling trying to figure out how to best shape my frequency response. I searched and people say that a flat frequency response doesn't sound good. What does? 

What kind of frequency response have you measured in cars that sound great? Which areas do you like to have boosted/cut and by how much?


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## azngotskills (Feb 24, 2006)

Is this for competition? If not, trust your ears on what sounds best to you.

Best to listen to a reference home setup, then try to replicate in the car IMO


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## 00poop6x (Jan 20, 2007)

azngotskills said:


> Best to listen to a reference home setup, then try to replicate in the car IMO



Mark, why would you do that to the OP??

And look what that got all of us into, a never ending battle. My car can't touch what's in the home


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## azngotskills (Feb 24, 2006)

00poop6x said:


> Mark, why would you do that to the OP??
> 
> And look what that got all of us into, a never ending battle. My car can't touch what's in the home


Well Chris, its something to strive for then   (note i said "try")


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## michaelsil1 (May 24, 2007)

dbiegel said:


> I'm struggling trying to figure out how to best shape my frequency response. I searched and people say that a flat frequency response doesn't sound good. What does?
> 
> What kind of frequency response have you measured in cars that sound great? Which areas do you like to have boosted/cut and by how much?


Danny,

I like my response to read flat B Weighting. Kevin K. has his tuned that way as well.


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## 14642 (May 19, 2008)

+9dB from 20-60Hz, smooth transition from 60 to 160. Flat from 160-about 3K, gentle slope downwards from there (adjust this slope and the amount of bass for personal preference). I've used this for nearly 20 years and no one has ever complained.


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## BMWturbo (Apr 11, 2008)

Andy Wehmeyer said:


> +9dB from 20-60Hz, smooth transition from 60 to 160. Flat from 160-about 3K, gentle slope downwards from there (adjust this slope and the amount of bass for personal preference). I've used this for nearly 20 years and no one has ever complained.


Thanks for that Andy, I might try retuning to somthing similar to this and see if I like it


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## Foglght (Aug 2, 2007)

Andy Wehmeyer said:


> +9dB from 20-60Hz, smooth transition from 60 to 160. Flat from 160-about 3K, gentle slope downwards from there (adjust this slope and the amount of bass for personal preference). I've used this for nearly 20 years and no one has ever complained.


Maybe I'm just losing my hearing, but I generally boost 12k+ to get some added sparkle. The negative slope at the high end makes it seem lo-fi to me.


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## Mooble (Oct 21, 2007)

Ditto. I boost gradually from about 8k+, but my tweeters roll off a little on the top end so it helps balance things out.


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## michaelsil1 (May 24, 2007)

Foglght said:


> Maybe I'm just losing my hearing, but I generally boost 12k+ to get some added sparkle. The negative slope at the high end makes it seem lo-fi to me.


A lot of people don't like sparkle; I personally love it. The cymbals need to sizzle and horns need to have some bite.


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## 14642 (May 19, 2008)

Are you guys referring to boosting your EQ or are you referring to a measured response curve that includes accentuated high frequencies? Those are two completely different things. If you're using tweeters that are larger than 1" or have them mounted off axis, some boost on your EQ may be necessary.


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## vecc205 (Nov 18, 2007)

Get some binaural microphones like these Stereo microphones, USB Microphones, Preamplifiers, Digital Recorders, Cables and more at Rock Bottom Prices from The Sound Professionals - Great deals on Microphone, Preamplifier, Digital Recorder, Cable and more!. All measurements are done with these mics in your ear while you sit in the listening positions.

I take a spatial average of the drivers side while I am in the driver's side seat. I take a spatial average of the passenger's side while I am in the passenger's seat. I do this with the binaural mics shown above for both sides and aim for the frequency response in the attachment matching them as closely as I can. After that is done I sum the two sides while in the driver's seat and aim for the curve shown in the attachment. This is all done after the gains have been set correctly and the speakers have been positioned in the right location. Below is the way I do the spatial average.

To do the spatial average I look at the drivers side mirror and do a measurement. Then I position my head where it would normally be driving and do a measurement. Then I look at the passenger's side mirror and do a measurement. 

Each measurement will be what the left ear hears and what the right ear hears (dual channel measurement), so after the three positions you will have 6 measurements. Take these 6 measurements and average them. Use the averaged curved to aim for the curve in the attachment using only cuts on the eq to obtain that response.

I have had excellent results with this method and even before I tweak with the ear I get a smooth non fatiguing sound. Hope this helps.


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## 14642 (May 19, 2008)

The post above IS precsely the measurement method for MS-8, except MS-8 will do all 4 seats (if you want to) calculate the arrival times and the EQ. It will provide an optimum tuning for each front seat, a compromise between the two front seats, and one for the back seats. Then, if you want to make adjustments, you can do that with a 31-band graphic.

Well...one day it will.


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## Foglght (Aug 2, 2007)

Andy Wehmeyer said:


> Are you guys referring to boosting your EQ or are you referring to a measured response curve that includes accentuated high frequencies? Those are two completely different things. If you're using tweeters that are larger than 1" or have them mounted off axis, some boost on your EQ may be necessary.


Whatchu talkin bout willis?

I hook things up, set my x-over points/gains/phase, then eq to my satisfaction. I used to RTA the crap out of my cars. I gave up after a while. To set a permanent RTA position would require some work and fabrication on my part. Otherwise the response curve was different every time I did it, and especially in the higher frequencies. Plus, because of the wide dynamic range of my car itself between sitting at a light and driving 80mph, measuring a response curve is almost pointless, imo.

Its kind of like engineering suspension. The mx''+cx'+kx = 0 equation of motion is only about 93% accurate. It is now known that really, it is more like cx'^1.2

Doing the extra math to get another 4% isn't worth it, unless you're talking F1 cars, or just really anal. Not that I advocate being lazy, but being able to hear the difference at 80mph, you'd have to have superman hearing.

I understand you though Andy. I know where ur goin.


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## GlasSman (Nov 14, 2006)

Andy Wehmeyer said:


> +9dB from 20-60Hz, smooth transition from 60 to 160. Flat from 160-about 3K, gentle slope downwards from there (adjust this slope and the amount of bass for personal preference). I've used this for nearly 20 years and no one has ever complained.


Nice curve you got there.

I might shoot for that once the current Ice Age is over.


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## kevin k. (May 5, 2005)

vecc205 said:


> Get some binaural microphones like these Stereo microphones, USB Microphones, Preamplifiers, Digital Recorders, Cables and more at Rock Bottom Prices from The Sound Professionals - Great deals on Microphone, Preamplifier, Digital Recorder, Cable and more!. All measurements are done with these mics in your ear while you sit in the listening positions.
> 
> I take a spatial average of the drivers side while I am in the driver's side seat. I take a spatial average of the passenger's side while I am in the passenger's seat. I do this with the binaural mics shown above for both sides and aim for the frequency response in the attachment matching them as closely as I can. After that is done I sum the two sides while in the driver's seat and aim for the curve shown in the attachment. This is all done after the gains have been set correctly and the speakers have been positioned in the right location. Below is the way I do the spatial average.
> 
> ...


Thanks for an informative post and detailed post, vecc205.  I've got the opportunity to use a stereo mic'd Praxis setup in the not-too-distant future, so this is right up my alley. Two comments / questions...

1) My emphasis is provided above, but I'm interested as to why you recommend eq cuts only when trying to obtain the desired response. No boosting, whatsoever? I'd like to know your thoughts, please, if you'd be so kind.

2) And, some credit to Jon Whitledge as your source for the target response graph you've posted... if I'm not mistaken, that data is pulled from his site...

www.whitledgedesigns.com

Thanks, again.


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## kevin k. (May 5, 2005)

michaelsil1 said:


> Danny,
> 
> I like my response to read flat B Weighting. Kevin K. has his tuned that way as well.


Well, truth be told... not entirely.


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## ErinH (Feb 14, 2007)

kevin k. said:


> Thanks for an informative post and detailed post, vecc205.


x2. I'm going to look into binaural headphones and re-read your post a few imes. This seems like something very worthwhile to try.


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## michaelsil1 (May 24, 2007)

kevin k. said:


> Well, truth be told... not entirely.


You sly devil.


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## vecc205 (Nov 18, 2007)

kevin k. said:


> Thanks for an informative post and detailed post, vecc205.  I've got the opportunity to use a stereo mic'd Praxis setup in the not-too-distant future, so this is right up my alley. Two comments / questions...
> 
> 1) My emphasis is provided above, but I'm interested as to why you recommend eq cuts only when trying to obtain the desired response. No boosting, whatsoever? I'd like to know your thoughts, please, if you'd be so kind.
> 
> ...


Yes, I apologize the posted graph came from John's website. I had used my binaural mics to measure my sennheiser headphones and got this exact curve. It wasn't coming in as an attachment so I used John's graph. I also put in test tones through the headphones and the level stayed equal through the frequency spectrum. I believe they call this diffuse field equalized if I am not mistaken. The reason I usually do all cuts is because dips in the frequency response are usually caused by cancellations, so boosting them may not be the best option. I find after I position the speakers by ear and testing there are not many drastic eq changes.


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## Bluto Blutarsky (Apr 1, 2007)

Danny, just keep turning screws until it sounds like Kevin's, then..............stop.


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## 14642 (May 19, 2008)

Foglght said:


> Whatchu talkin bout willis?
> 
> Otherwise the response curve was different every time I did it, and especially in the higher frequencies.


This is the reason for the spatial average.

Oh, and I guess my car is an F1-Audio car.


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## Foglght (Aug 2, 2007)

Andy Wehmeyer said:


> This is the reason for the spatial average.
> 
> Oh, and I guess my car is an F1-Audio car.


I have no doubt Andy. I am unaware of a fairly simple way to take spatial averages without a crazy mic setup in my car. Last one I saw was at Tom Nousaine's (sp?) house, and it belonged to the Alpine guy. Something like that ain't cheap.

They don't provide that in the headunit kit, probably for good reason.


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## smellygas (Feb 21, 2008)

Foglght said:


> I have no doubt Andy. I am unaware of a fairly simple way to take spatial averages without a crazy mic setup in my car. Last one I saw was at Tom Nousaine's (sp?) house, and it belonged to the Alpine guy. Something like that ain't cheap.
> 
> They don't provide that in the headunit kit, probably for good reason.


I use an ECM8000 mic, TrueRTA, and pink noise, and take 4 different measurements from the driver's seat by moving the mic by an inch or two each time. The 4 different readings can then be averaged in TrueRTA and you get the equivalent of a spatially averaged curve.

I found that ruler-flat tends to overemphasize the highs in my car setup. I'm not entirely sure why, but based on listening, I have the best results when have a flat response from ~200Hz to about 4kHz, then a slope down, maybe 5-8db total, until 20kHz. I'm still playing with the 20Hz-200Hz range. Interestingly, someone else here posted a similar preferred response curve! I have a suspicion that something in the car is creating a measurement artifact in the highs, because at home, using the same measuring equipment, a flat response from 100Hz to 20kHz seems to have a similar tonal balance. Weird.

SG


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## Foglght (Aug 2, 2007)

smellygas said:


> I use an ECM8000 mic, TrueRTA, and pink noise, and take 4 different measurements from the driver's seat by moving the mic by an inch or two each time. The 4 different readings can then be averaged in TrueRTA and you get the equivalent of a spatially averaged curve.
> 
> SG


Interesting, I use the same stuff. I didn't know that true RTA can average readings and display that curve. Though, I believe you aren't talking real time measurement. That would require taking measurements one at a time, removing it all, making adjustments, setting it back up, and repeating. 

Geo had some bin-aural mics (think that's what they're called) where he actually sat in the car and took a real time measurement. That would be more accurate, but if you move your head slightly, the response changes, and nevermind the passenger, if one exists. 

Even at that point, you still have to break this down to bare basics. Most people install, then tune, if they do any tuning at all. I could see it being fairly easy to tune tweeters, as they are easily placed in many different places in the vehicle, but when we're talking mid-basses which can sometimes be 8" drivers, its pretty difficult to screw around with mounting and aiming positions, especially within the confines of a car. 

At this point, I haven't listened to a TON of nice system builds, but probably 20-30. They all have different staging and artifact definition, some I like, some I don't. Even in my own car (shaggin wagon), I don't like some of the imaging. RTA'ing the car would almost be pointless, as I have no desire to mount the drivers differently, which is probably the case for most people (maybe not on this site though). I have my SQ disc. I play it and EQ till it sounds good, which is already a predetermined set of qualities that were burned into me long before I started into car audio.


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## vecc205 (Nov 18, 2007)

This is the frequency response of my Sennheiser HD25-1's with the binaural mics in my ears and the headphones on my ears. Everything above 8k I don't believe is accurate and I dial that in by ear. Look at the above thumbnail I posted from John Whitledge's website, the high end response should look similar to that.


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## sqshoestring (Jun 19, 2007)

Compared to a good home setup I'd say I add more <40Hz progressively, where the home system fails for the most part though I might go a little too far.


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## kevin k. (May 5, 2005)

vecc205 said:


> This is the frequency response of my Sennheiser HD25-1's with the binaural mics in my ears and the headphones on my ears. Everything above 8k I don't believe is accurate and I dial that in by ear. Look at the above thumbnail I posted from John Whitledge's website, the high end response should look similar to that.


Now, don't forget that the response he shows in that graph is B-weighted... the unweighted (or Z-weighted, technically) graph is shown on the same page and is illustrative as to the different appearance of the same curve, but with alternate weightings applied...

Thanks again, for your help, vecc205... I love this stuff.


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## dbiegel (Oct 15, 2006)

michaelsil1 said:


> Danny,
> 
> I like my response to read flat B Weighting. Kevin K. has his tuned that way as well.


Ok so I looked up the B weighting curve online to see what it means:










Since this is an RTA filter, and you tuned it to be flat, your actual frequency response curve would be the *inverse* of this. More bass boost at the lowest frequencies than Andy, but much less in the 60 region. Practically flat from 160-4khz like Andy's and others... but then you boost the high frequencies (up to +14db at 20khz) rather than attenuate.

I'd think this would make the bass muddy and bottom heavy and the highs ear-bleeding. However, in your car it sounded great with lots of clear midbass and "bite," certainly not piercing and muddy.

Andy, smellygas, vecc, kevin -- do you measure flat or with weighting applied? Looks like that can make a huge difference.

Good stuff guys, keep it coming.


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## dbiegel (Oct 15, 2006)

azngotskills said:


> Is this for competition? If not, trust your ears on what sounds best to you.
> 
> Best to listen to a reference home setup, then try to replicate in the car IMO


Not for competition, just for myself... though I'd love to know what competition winning frequency responses look like  From what I've seen they're certainly not flat.

I've been trying to trust my ears, but I'm having a hard time tuning for different tracks and genres. If I tune using piano and cello, and then play something like Tool or Metallica, the drums completely lack any impact, etc. I guess its all a compromise in the end, and seeing what people have come up with would definitely help.


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## smellygas (Feb 21, 2008)

Foglght said:


> Interesting, I use the same stuff. I didn't know that true RTA can average readings and display that curve. Though, I believe you aren't talking real time measurement. That would require taking measurements one at a time, removing it all, making adjustments, setting it back up, and repeating.


Nah. Each measurement takes 15 seconds. Take a reading, save it, move the mic, take a reading, save it, move the mic, etc. 4 curves, each saved to memory, then use TrueRTA to average the 4 corresponding memorized curves, and voila - u have an averaged response curve from the "head region." 



> Geo had some bin-aural mics (think that's what they're called) where he actually sat in the car and took a real time measurement. That would be more accurate, but if you move your head slightly, the response changes, and nevermind the passenger, if one exists.


That's a pretty cool idea, because it accounts for the effect of the driver, but you still need to move the mics around and take multiple measurements, then average them.

SG


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## michaelsil1 (May 24, 2007)

dbiegel said:


> Not for competition, just for myself... though I'd love to know what competition winning frequency responses look like  From what I've seen they're certainly not flat.
> 
> I've been trying to trust my ears, but I'm having a hard time tuning for different tracks and genres. If I tune using piano and cello, and then play something like Tool or Metallica, the drums completely lack any impact, etc. I guess its all a compromise in the end, and seeing what people have come up with would definitely help.


Keep in mind that using a RTA or MLS will only get you in the ballpark if you want a Cello to sound like a Cello proper T/A is also necessary; if you have it sitting in the Bass Violin section it's not going to sound right. 

I think that is why Kevin K. has alignment as the first priority. 


I listen to an orchestra for hours before I tweak again; classical has the best recordings and is a great reference source providing you know what the instruments are supposed to sound like.


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## smellygas (Feb 21, 2008)

dbiegel said:


> Andy, smellygas, vecc, kevin -- do you measure flat or with weighting applied? Looks like that can make a huge difference.
> 
> Good stuff guys, keep it coming.


No weighting applied (flat). Again, at home, TrueRTA measures pretty flat up to 20kHz on my reference speakers. It's only in the car that I need to tune with the high freq rolloff. 

I think this has something to do with the reflections in the car environment throwing off the RTA measurement. In the car, all the "walls" are a few feet away and they're fairly reflective (i.e. glass). There may be reflected sound that is not "perceived" as belonging to the original sound because of a delay in arrival (Haas effect), but is still picked up and registered by the pink noise + RTA set up. The solution would be to take measurements with something gated, like a gated sine sweep or a gated MLS signal with a very short measurement window. I don't have the software for that. Oh well.

SG


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## kevin k. (May 5, 2005)

michaelsil1 said:


> think that is why Kevin K. has alignment as the first priority.


It's definitely a priority, although I'm not sure that it it's my first... too many to choose from! :laugh:

Hey, dbiegel... if you're interested, you're welcome to give me a call and we can talk about this stuff at length and share info back and forth. Where are you in San Diego? I'm in North County. My car is up and running, at the moment, although it will be without amps pretty soon... if you want to get together, do some listening, measuring, whatever, just let me know. My # is in your pm...


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## kevin k. (May 5, 2005)

dbiegel said:


> I'd think this would make the bass muddy and bottom heavy and the highs ear-bleeding. However, in your car it sounded great with lots of clear midbass and "bite," certainly not piercing and muddy.


Some recordings will sound just the way you described... last meet I was at I demo-ed for Michael how one recording can sound spot-on while another sounds totally overblown...

Too bad we all hear differently and listen to music that's been produced differently...! A good recipe for a passion.


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## michaelsil1 (May 24, 2007)

kevin k. said:


> It's definitely a priority, although I'm not sure that it it's my first... too many to choose from! :laugh:



Kevin,

Don't make me look up where you said it was first on your list.


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## dbiegel (Oct 15, 2006)

kevin k. said:


> It's definitely a priority, although I'm not sure that it it's my first... too many to choose from! :laugh:
> 
> Hey, dbiegel... if you're interested, you're welcome to give me a call and we can talk about this stuff at length and share info back and forth. Where are you in San Diego? I'm in North County. My car is up and running, at the moment, although it will be without amps pretty soon... if you want to get together, do some listening, measuring, whatever, just let me know. My # is in your pm...


PM sent.


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## vecc205 (Nov 18, 2007)

When I use the binaural mic measurement to get this curve I don't use any weighting. Weighting curves try to replicate the frequency response of our hearing at different levels. When using the binaural mics to measure unweighted and the response I have shown, it is very close to flat to you ear and not flat to a mic. I tested this by using my Sennheiser's and playing test tones through them while they were on my ears and the binaural mics were in my ears showing the sound level presented to each mic in my left and right ear. When I did this, the sound level from frequency to frequency didn't change, so the perceived sound level was flat to the mic sitting in my ear canal. 

The binaural mics also have the benefit of taking into account your head related transfer function. The shape of your torso, where your legs are when you are listening, the shape of your outer ear etc... all play a role on the perceived frequency response. That's why I find it is such an advantage over using an rta mic.

Hope this helps...and thanks for all the input.


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## vecc205 (Nov 18, 2007)

O I almost forgot. You can get a little sneaky here with the binaural mics. You can make your own binaural recordings to use as a reference. No more guessing what the engineer intended it to sound like, your ears become the mic. Although with headphones you get a full 360 degree effect with a binaural recording (pretty cool stuff), when played back over loudspeakers you won't get a 360 degree effect. Everything you recorded that comes from behind will come from in front of you because the acoustical crosstalk in a loudspeaker setup and the lack thereof in a headphone setup. Keep it coming this is getting good!


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## npdang (Jul 29, 2005)

You're ignoring one very vital issue... how are you measuring said frequency response?


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## 14642 (May 19, 2008)

dbiegel said:


> If I tune using piano and cello, and then play something like Tool or Metallica, the drums completely lack any impact, etc.


Pay close attention to the transition between bass and midbass. Don't be afraid to have plenty of bass BELOW 60Hz and be sure it's back to flat by 160Hz and you'll find that the piano still sounds accurate and the bass and midbass are good too.

One thing to keep in mind, though, is that no standard exists for studio setups. If he monitoring system is bass heavy, the recording will probably be bass shy and vice versa. It's a little scary to think that someone might actually monitor a mix using the Sennheiser headphones in one of the previous posts. This is one reason that a bass control is so handy.


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## 14642 (May 19, 2008)

smellygas said:


> I think this has something to do with the reflections in the car environment throwing off the RTA measurement. In the car, all the "walls" are a few feet away and they're fairly reflective (i.e. glass). There may be reflected sound that is not "perceived" as belonging to the original sound because of a delay in arrival (Haas effect), but is still picked up and registered by the pink noise + RTA set up. The solution would be to take measurements with something gated, like a gated sine sweep or a gated MLS signal with a very short measurement window. I don't have the software for that. Oh well.
> 
> SG


The first part of this post is correct. In a car we hear the speaker's power response (a combination of the on-axis response and all of the off axis sound reflected from all the interior surfaces). This is why a crrect directivity index is o important for car speakaers, but it's something that's not often considered in the design of component systems and crossovers. There's no HAAS effect in cars, because the reflections are too short to be perceived as a second event. We hear all of them as modifications of the original event. Using a gated measurement would give you the anechoic response of the speaker at high frequencues (no way to do a full-band gated measurement in a car with enough resolution to tell you anything below 1kHz or so), but anechoic response isn't what you hear. 

Finally, for those of you who are using binaural mics, the target curve at high frequencies with the binaural mics will be different than for a single mic or mic array that isn't attached to someone's head. Our heads provide significant masking of high frequencies, so the target with the binaural mic sould have less high frequency than with a standard mic.


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## michaelsil1 (May 24, 2007)

npdang said:


> You're ignoring one very vital issue... how are you measuring said frequency response?


Please elaborate.


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## Fish Chris (Dec 14, 2008)

Ya' know, to me a totally flat "show quality" system, sounds like $#!+......

However, one of my eventual goals, is to be able to 1) add a sound proccessor, 2) do the electronic reading of my system (do they call that RTA'ing ? 3) flatten my system as completely as possible, and 4) save that flat setting in the memory of my sound proccessor. 

"Then" from there, I can start with a clean (flat) slate, making EQ adjustments that sound best to "my ears".... to hell with everybody else. I'm the one that paid for this freaking $#!+ ! ;-)

Peace,
Fish


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## vecc205 (Nov 18, 2007)

michaelsil1 said:


> Please elaborate.


Yes please elaborate more for us... Thanks


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## mvw2 (Oct 2, 2005)

My ideal response is ear flat. I don't know what response this is though. My method uses pink noise (unbiased towards any song/artist). I run through the EQ and balance all levels so no one frequency overshadows another and no frequency lacks. What I end up with is a response that is flat to my ears. This is the best method I've found.


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## vecc205 (Nov 18, 2007)

Andy Wehmeyer said:


> Pay close attention to the transition between bass and midbass. Don't be afraid to have plenty of bass BELOW 60Hz and be sure it's back to flat by 160Hz and you'll find that the piano still sounds accurate and the bass and midbass are good too.
> 
> One thing to keep in mind, though, is that no standard exists for studio setups. If he monitoring system is bass heavy, the recording will probably be bass shy and vice versa. It's a little scary to think that someone might actually monitor a mix using the Sennheiser headphones in one of the previous posts. This is one reason that a bass control is so handy.


Why would it be so scary if someone was monitoring a mix through headphones? I understand that using monitors for the final touches is necessary, why is it scary to use headphones at all? Thanks


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## vecc205 (Nov 18, 2007)

mvw2 said:


> My ideal response is ear flat. I don't know what response this is though. My method uses pink noise (unbiased towards any song/artist). I run through the EQ and balance all levels so no one frequency overshadows another and no frequency lacks. What I end up with is a response that is flat to my ears. This is the best method I've found.


Same thing here, hence the binaural mics and the curve posted.


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## 14642 (May 19, 2008)

vecc205 said:


> Why would it be so scary if someone was monitoring a mix through headphones? I understand that using monitors for the final touches is necessary, why is it scary to use headphones at all? Thanks


The headphone curve posted here is anything but flat. If the "mixologist" mixes the track so it sounds natural and balanced, then the playback system has to have the same curve as the headphones to sound "natural and balanced". If the mixologist built the mix with a flat monitoring system, then that wouldn't be the case. THe point is that if the mix is based on flat response, then there's a well-known baseline. If the mix is built using some arbitrary system with peaks and dips all over the place, it'll be less likely to sound good on a good system.


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## vecc205 (Nov 18, 2007)

Andy Wehmeyer said:


> The headphone curve posted here is anything but flat. If the "mixologist" mixes the track so it sounds natural and balanced, then the playback system has to have the same curve as the headphones to sound "natural and balanced". If the mixologist built the mix with a flat monitoring system, then that wouldn't be the case. THe point is that if the mix is based on flat response, then there's a well-known baseline. If the mix is built using some arbitrary system with peaks and dips all over the place, it'll be less likely to sound good on a good system.


The headphone curve isn't flat by looks, but it is flat to the ear. In fact many of the audiophile open cans and studio headphones are diffuse-field equalized like this. Why then are these headphones described as being natural or realistic sounding and to be used for mixing? I am not disagreeing with I am just confused about the diffuse-field equalized headphones being used for mixing applications.


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## 14642 (May 19, 2008)

My understanding of diffuse field EQ is that it's designed to sound the same for a bunch of different listeners with different heads and different ears, not that it's designed to replicate the frequency response of a real room--except that the headphone curve above appears to be the inverse (or an approximation of the inverse) of the directivity curve for a speaker that would probably sound good in a reflective environment. Well...except for the high frequency stuff...


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## smellygas (Feb 21, 2008)

Andy Wehmeyer said:


> The first part of this post is correct. In a car we hear the speaker's power response (a combination of the on-axis response and all of the off axis sound reflected from all the interior surfaces). This is why a crrect directivity index is o important for car speakaers, but it's something that's not often considered in the design of component systems and crossovers. There's no HAAS effect in cars, because the reflections are too short to be perceived as a second event. We hear all of them as modifications of the original event. Using a gated measurement would give you the anechoic response of the speaker at high frequencues (no way to do a full-band gated measurement in a car with enough resolution to tell you anything below 1kHz or so), but anechoic response isn't what you hear.


Here's the problem I have. In free-air or anechoic measurement conditions, the loudspeakers that sound better are the ones with relatively smooth and flat frequency response curves over the entire listening range. In a room, however, reflection and reverberation are added. Some of these spurious sounds, which arrive later than the direct sound, are not "processed" by the listener as affecting the tone of the loudspeaker (because of the Haas effect). However, the RTA will "sum" the reflected/reverbed sound with the direct sound and cause peaks in the response. This is why equalizing based on an RTA in a room can yield poor results. This also explains why the power-response curve that is measured by an RTA can exhibit exaggerated highs when equalized flat. This is because the tweeters have downsloping off-axis response, that is picked up on the power-response measurement (which is weighted on- and off-axis). However, off-axis sound contains a lot of reflected/reverb sound that won't be registered as affecting the perceived response curve because it is delayed.However, by gating the measurement to include just the direct sound, you can measure what the ear processes. Depending on the gating window, you should be able to get useful measurements down to 300Hz or so, or so I've read.

Here's the problem: In a car, I agree - there shouldn't be a significant Haas effect. We would need at least 30ms of delay from reflections, which would imply multiple multiple reflections off each car surface, each reflection attenuated in volume. The car walls are so close together, I would expect all of the reflected sound to register equivalently with the direct sound. That is, the power-response represents the "perceived response." 

So WHY does a flat RTA measurement in a car yield poor results (i.e. exaggerated highs)? A flat ANECHOIC frequency response is generally desirable, and this is well-established. So clearly, some aspect of the MEASUREMENT PROCESS using an RTA with pink noise in a car is inaccurate. Why does a sloping-down curve after 2-3kHz, measured via RTA, sound better? Interestingly, another person and myself both described an "ear-tuned" curve that looks exactly like the Boner preferred listening curve
http://www.prosonicsolutions.com/articles/Equalization Revisited.pdf

Any takers?

SG


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## 14642 (May 19, 2008)

Because flat response in a car sounds too bright. It's also well established that a speaker with flat power response sounds too bright in a room, especially a highly reflective room. This is the reason that real speaker companies measure directivity and figure that into the design. A flat on-axis response and gently rising direcitivity index yields a speaker that sounds natural in a room. In cars, many of the reflective surfaces (boundaries) are very close to the speaker, so the intensity of the sound that arrives at our ears is very similar to the direct sound. If the reflections include a lot of high frequency content, the car sound too bright. Where is the mystery? 

Maybe I don't understand the question.


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## smellygas (Feb 21, 2008)

Andy Wehmeyer said:


> Because flat response in a car sounds too bright. It's also well established that a speaker with flat power response sounds too bright in a room, especially a highly reflective room. This is the reason that real speaker companies measure directivity and figure that into the design. A flat on-axis response and gently rising direcitivity index yields a speaker that sounds natural in a room. In cars, many of the reflective surfaces (boundaries) are very close to the speaker, so the intensity of the sound that arrives at our ears is very similar to the direct sound. If the reflections include a lot of high frequency content, the car sound too bright. Where is the mystery?
> 
> Maybe I don't understand the question.


In a room, measuring direct + reflected lows/mids, but only direct highs (due to poor tweeter off-axis response). Reflections are mostly from off-axis radiation bouncing off walls. The measured power response curve therefore slopes down in the highs. However, since the REFLECTED lows/mids are not perceived by the ear, the component of the sound that is direct-only (essentially the anechoic response) is relatively flat. This is why correcting the downsloping highs in a power response curve actually boosts the highs and makes the result sound bright. 

HOWEVER, in a car, the reflected sounds are so close in timing to the direct sound that they should both be perceived together, as one sound. Therefore, everything you measure by the RTA should be used. Unlike in the room, when the lows/mids measure artifically high because it also sums the reflections, the car's measurement isn't artifically inflated inthe lows/mids because the reflected sound IS perceived along with the direct sound. This would imply that the RTA measurement is accurate as-is and shoot for a flat response. Indeed, in Jon Whitledge's magic car, his response was an actual upsloping of the lows and highs. 

This makes me worried that in the process of making my RTA response flat, I am over-EQ'ing something and increasing distortion, which is giving me a harsher sound. Turning down the tweeter volume may decrease distortion levels, and also make me think that I need a downsloping RTA curve. I'm going to re-EQ my system this weekend.

SG


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