Wrote:
I've gotten some RTA (real time analysis) equipment, and I RTA'ed my
car, and the result is found he www.geocities.com/bryan1232 under
loudspeakers, at the bottom.

Does the bass cut off from 40 to 200hz look basically like an x-over
error. I have not touched the x-overs from where my installers left
them. The MTX amps have no x-over marking for frequency, but I could
always do so with this setup. For the other 3 humps, I think a
parametric EQ would do nicely.

Any suggestions?
Phew...

I can tell by the response plot that you have a ported box, tuned to
about 40hz - resulting in that big peak in the 40-45hz range.
...or, in terms that you no doubt are experiencing... some songs really
"hit", while others just seem weak.

It may also be that your crossover is set too low...
I'd personally start you out by setting your sub crossover somewhere
around 75-80hz.

The dip in the 100-200hz range doesn't necessarily mean your component
high-pass crossover is set wrong - although that would certainly do
that also.

But, it's more likely that you have speakers installed as "drop in
replacements" in your doors...
...and no matter how good your new speakers are, this problem isn't
their fault - it's the fault of your doors... they simply aren't good
speaker cabinets.
What's going on is that the rear sound energy off the back of the
speaker is able to leak out of the door cavity via all those big access
holes in your inner door structure, and is cancelling, getting worse
and worse the lower in frequency you go.

If you know anything about a home-audio concept called "dipole" -
that's essentially what's going on here. Whatever frequency's
wavelength fits from the center of your speaker's cone, to the closest
access hole in your inner door structure, is about the lowest those
speakers will be able to play without cancellations existing... just
like figuring out how low your dipole speakers could play.

The peak between 300hz and 400hz could either be ignored, or ironed
out, likely with EQ (resolving it naturally, by aiming the speakers, or
damping surfaces on your car's interior is quite involved).

The dip between 500hz and 700hz is the one that causes me the greatest
concern... it might be difficult to boost up, EQ might not help.
It's low enough that it's not due to your crossover between mid and
tweet, and low enough that it's not due to natural inductance in the
midrange.
Blame car acoustics, or speaker aiming.
The fact that the response rises pretty steadily as you go higher from
that point might highlight a speaker aiming issue... but it might
simply be acoustic cancellations in your car interior.
Try to EQ them - you might not be able to get far with that, if it is
cancellations, though.

Right at 1.5khz, there's a peak that needs to be knocked down.

The dip between 2khz and 4khz may be due to your having a component set
in your car (do you?), and having the tweeter and mid some distance
apart from each other. Really, I'm suspecting it's not so much a
"dip", as it is that you just have a peak at 1.5khz, and 5khz-8khz.

In the 5khz to 8khz range, that also needs to be brought down...
I'd suspect that your tweets are simply too "hot" (are they near the
windshield?), but above 8khz, they do fall off very rapidly.
Are they soft dome tweets by chance?
Or cheap tweeters?
I'd fear using attenuation to knock the tweet down uniformly, because
that'll knock everything down above 4khz or so... and you really need
to give a little lift in the 10khz-20khz octave... although there's not
a lot of music in that final octave anyway, so possibly no big deal
ultimately.

I'm not personally a fan of EQ'ing - it's a pain in the butt to get
right.
BUT - it'll quickly become apparant where you have simple EQ issues -
and where you have phasing issues - whether they are in an absolute
sense, an electrical sense, or a reactionary sense.

Good luck - I'm curious if I'm right on my guesses!


--
geolemon


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I've gotten some RTA (real time analysis) equipment, and I RTA'ed my
car, and the result is found he www.geocities.com/bryan1232 under
loudspeakers, at the bottom.

Does the bass cut off from 40 to 200hz look basically like an x-over
error. I have not touched the x-overs from where my installers left
them. The MTX amps have no x-over marking for frequency, but I could
always do so with this setup. For the other 3 humps, I think a
parametric EQ would do nicely.

Any suggestions?

1. Yes, I do have coaxials. I have no idea where my x-overs are at,
because my amps do not say what the frequency is when you turn the
knob, so that will be trial and error. I know my doors suck as far as
speaker cabinets, but fixing it is too complicated and costly for me.
If anything, maybe components.

2. Nope, it's a sealed box.

3. The 2-4khz is not due to that because I have coaxials in the doors
:-)

4. Yes! My tweeters hurt my ears! Especially female vocal "s"'. They
are decent speakers. Polk MMC525. Best I heard when I was auditioning
speakers. They have an outboard x-over, I know that has nothing to do
with the tweets, though! :-) They are silk dome tweeters.

I don't have the cash for an EQ right now. It's awesome being a
college student with interests in home theater and car audio! I get to
spend a lot of time searching for the best deal. I think that
adjusting my x-over is the best bet for now. For all I know there is a
12db/octave x-over that takes it down after 40hz

1. Yes, I do have coaxials. I have no idea where my x-overs are at,
because my amps do not say what the frequency is when you turn the
knob, so that will be trial and error.

That's good. I like amps that don't say. First, it doesn't bias the user.
Second, in some amps the discrepancy between the value on the dial and the
true xover point is quite large.

snip
4. Yes! My tweeters hurt my ears! Especially female vocal "s"'. They
are decent speakers. Polk MMC525. Best I heard when I was auditioning
speakers. They have an outboard x-over, I know that has nothing to do
with the tweets, though! :-) They are silk dome tweeters.

Have you tried simply turning down the treble? Don't despair when you first
do it. Things will sound flat and muffled at first. But as your ears
readjust themselves to the modification, you may find that this problem goes
away. That's the thing about audio - it usually takes a period of extended
listening after you make an adjustment. You have to get used to the change
before you're able to appreciate whether or not there's an improvement in
sound.

I don't have the cash for an EQ right now. It's awesome being a
college student with interests in home theater and car audio! I get to
spend a lot of time searching for the best deal. I think that
adjusting my x-over is the best bet for now. For all I know there is a
12db/octave x-over that takes it down after 40hz

Are you sure it's not a byproduct of the measuring equipment itself? Some
mic's exhibit a rolloff at really low frequencies. But if it's real, who
cares? Some people go through a lot of effort to eliminate the 40Hz
content.

As always, my advice is to put away the RTA and make the adjustments using
your ears as the guide. It may be fun later on to see what the results are.
I'd bet that the RTA would look even more screwed up after you further
adjusted the system to better suit your tastes.

I have turned down the treble (I have controls for 10 12 14 and 17khz),
and none of them ever really made me very happy.

I think the 40hz hump could be the microphone, but not the roll off
because I have tested my home sub and it was pretty flat down to 20hz.
This did confirm some things I thought though, such as the sub level is
higher than the rest. It felt like I was lacking a lot of punchy
midbass.

I do think that I need to work on my x-overs though.

Somewhat related question, since I don't use my rear speakers (unless
people in the rear seats want them on, but that's very rare) would it
be to my advantage to bridge my 4channel amp to 2 channels for the
175wpc output even though I'd never use it that high, atleast I'd have
a lot of headroom.

MZ wrote: "I'd bet that the RTA would look even more screwed up after you
further
adjusted the system to better suit your tastes."

So very, very true. I've tweaked my system by ear untill it sounded so good
it brought tears to my eyes. Then, when I measure it the response curve
looks like the Swiss Alps!

Tony


--
Eclipse CD8454 Head Unit, Phoenix Gold ZX475ti, ZX450 and ZX500 Amplifiers,
Phoenix Gold EQ-232 30-Band EQ, Dynaudio System 360 Tri-Amped In Front and
Focal 130HCs For Rear Fill, 2 Soundstream EXACT10s In Aperiodic Enclosure

Somewhat related question, since I don't use my rear speakers (unless
people in the rear seats want them on, but that's very rare) would it
be to my advantage to bridge my 4channel amp to 2 channels for the
175wpc output even though I'd never use it that high, atleast I'd have
a lot of headroom.

Yeah, it would be advantageous to do so. You'd be surprised how easy it is
for the transients to reach that kind of output level.

MZ wrote: "I'd bet that the RTA would look even more screwed up after you
further
adjusted the system to better suit your tastes."

So very, very true. I've tweaked my system by ear untill it sounded so
good it brought tears to my eyes. Then, when I measure it the response
curve looks like the Swiss Alps!

Yeah, I did it once a while back and the highs and lows appeared to dip
pretty dramatically, and the midrange was all over the damned place. Some
of it was predictable, based on my listening habits, but some of it was
surprising.

Chad Wahls Wrote:
"MZ" wrote in message
...
MZ wrote: "I'd bet that the RTA would look even more screwed up
after you
further
adjusted the system to better suit your tastes."

So very, very true. I've tweaked my system by ear untill it sounded
so
good it brought tears to my eyes. Then, when I measure it the
response
curve looks like the Swiss Alps!

Yeah, I did it once a while back and the highs and lows appeared to
dip
pretty dramatically, and the midrange was all over the damned place.
Some
of it was predictable, based on my listening habits, but some of it
was
surprising.


Plug one ear and listen, that's effectively what the RTA is doing. I
tell
people that RTA's can hear just fine, they just can't listen

Chad
Interesting that you mention that!

One of the more fascinating pieces of test equipment that I've had the
pleasure to learn of was at David Clarke's DLC labs in Detroit,
Michigan...

He's invented (or one of his partners) a device called the Spectral
Transfer Function Measurement Device...

And roughly, it's an RTA.

The catch is, it has two mics, positioned on a "dummy head", to hear as
your ears do. The whole assembly is positioned on a motorized track
that slides gently forward and backward to iron out minor phase issues.


Pretty cool, invented under the same train of thought that you mention.


Another interesting FYI about that particular test equipment:
The Chrysler corporation contracted with DLC to perform acoustical
testing in their vehicles - this was the year the Jeep Liberty was
introduced, and was the first Chrysler production vehicle to benefit
from this testing.
Essentially, DLC took the absolute RTA measurements from this
measurement device, and burned them to a DSP chip that exists in the
head unit of those cars.
Many Chrysler products these days benefit from one heck of a fancy RTA.


--
geolemon


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MZ Wrote:
Interesting that you mention that!

One of the more fascinating pieces of test equipment that I've had
the
pleasure to learn of was at David Clarke's DLC labs in Detroit,
Michigan...

He's invented (or one of his partners) a device called the Spectral
Transfer Function Measurement Device...

And roughly, it's an RTA.

The catch is, it has two mics, positioned on a "dummy head", to hear
as
your ears do. The whole assembly is positioned on a motorized track
that slides gently forward and backward to iron out minor phase
issues.


Pretty cool, invented under the same train of thought that you
mention.

snip

Ah, a crash test dummy with ears. Excellent!

The fact that the frequency content of the signal is modified
extensively by
the pinna of the ear and by the head before it even reaches the ear
drum is
too often overlooked when it comes to these sorts of measurements.

However, I suspect that the corrected signal wouldn't be very pleasing
to
the ear. I would think that this would require an even more dramatic
boost
to high frequencies. And, in my experience, many people find a
spectrally
flat high frequency portion to be much too bright as it is. I'm
guessing
that the spectral sensitivity of the ear must also be taken into
account
when it comes to devising the "ideal" setup.
While I can't say that I know the final curve shape... I do know it's
nothing resembling flat, and I do know that Chrysler's do sound quite a
bit better than your typical system these days... maybe lacking a bit
in the bass department, maybe not having the fastest decay drivers...
but definitely great in terms of overall frequency response.
Next time a Liberty or other newer Chrysler product is in your shop (or
have a chance to sit in one), take a minute to do a little unexpected
critical listening.
Fun.

Anyway... I know it's nothing resembling flat, because David Clark told
us himself that the measured frequency response wasn't compared to a
"flat" response, but rather a curve that was essentially the product of
his, and a bunch of other audiophiles (AES members?) collective
"average" (if you will) of what they believed to be an ideal frequency
response.
THAT curve is what the EQ chips are encoded to aspire to.

And the head wasn't a crash test dummy-like head... it was a treatment
to the heads of the mics, essentially, as I understood. I didn't get
to witness a run of it, unfortunately... I saw the comparator in the
rack of equipment, and got the description.
It was something that Dr. Clark was quite proud of!


--
geolemon


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"MZ" wrote in message
...
MZ wrote: "I'd bet that the RTA would look even more screwed up after you
further
adjusted the system to better suit your tastes."

So very, very true. I've tweaked my system by ear untill it sounded so
good it brought tears to my eyes. Then, when I measure it the response
curve looks like the Swiss Alps!

Yeah, I did it once a while back and the highs and lows appeared to dip
pretty dramatically, and the midrange was all over the damned place. Some
of it was predictable, based on my listening habits, but some of it was
surprising.


Plug one ear and listen, that's effectively what the RTA is doing. I tell
people that RTA's can hear just fine, they just can't listen

Chad

MZ wrote:

Are you sure it's not a byproduct of the measuring equipment itself? Some
mic's exhibit a rolloff at really low frequencies.

This would be my concern. How well calibrated is the gear, does the mic actually
have the capability of showing a FLAT readout on the screen if a FLAT source is
encountered... Without KNOWING the mic and analysers characteristics it is
pretty hard to rely on the results of the RTA... Most RTAs I have seen are very
unreliable when used by someone that does not really understand them...

Eddie Runner
http://www.installer.com/tech

Interesting that you mention that!

One of the more fascinating pieces of test equipment that I've had the
pleasure to learn of was at David Clarke's DLC labs in Detroit,
Michigan...

He's invented (or one of his partners) a device called the Spectral
Transfer Function Measurement Device...

And roughly, it's an RTA.

The catch is, it has two mics, positioned on a "dummy head", to hear as
your ears do. The whole assembly is positioned on a motorized track
that slides gently forward and backward to iron out minor phase issues.


Pretty cool, invented under the same train of thought that you mention.

snip

Ah, a crash test dummy with ears. Excellent!

The fact that the frequency content of the signal is modified extensively by
the pinna of the ear and by the head before it even reaches the ear drum is
too often overlooked when it comes to these sorts of measurements.

However, I suspect that the corrected signal wouldn't be very pleasing to
the ear. I would think that this would require an even more dramatic boost
to high frequencies. And, in my experience, many people find a spectrally
flat high frequency portion to be much too bright as it is. I'm guessing
that the spectral sensitivity of the ear must also be taken into account
when it comes to devising the "ideal" setup.

geolemon wrote:
..

MZ Wrote:
Interesting that you mention that!

One of the more fascinating pieces of test equipment that I've had
the
pleasure to learn of was at David Clarke's DLC labs in Detroit,
Michigan...

He's invented (or one of his partners) a device called the Spectral
Transfer Function Measurement Device...

Actually it is called the Perceptual Transfer Function (PTF)



And roughly, it's an RTA.

It would be more correct to call it an RTA-based ot RTA-like measurement scheme
for part if its measurement suite ...it tests more than frequency response and
uses test signals other than pink noise as well.


The catch is, it has two mics, positioned on a "dummy head", to hear
as
your ears do. The whole assembly is positioned on a motorized track
that slides gently forward and backward to iron out minor phase
issues.

Phase has nothing to do with it. It uses 2-microphones with 4 different
positions. The idea here is to average response over an area that represents
the sound that arrives at normal listening positions for a range of body/head
sizes.



Pretty cool, invented under the same train of thought that you
mention.

snip

Ah, a crash test dummy with ears. Excellent!

The fact that the frequency content of the signal is modified
extensively by
the pinna of the ear and by the head before it even reaches the ear
drum is
too often overlooked when it comes to these sorts of measurements.

The foam "head" is not meant to be a susbstitute for the head related transfer
function (HRTF) but to simulate the directivity characteristic of sound
reaching humans in the car.


However, I suspect that the corrected signal wouldn't be very pleasing
to
the ear. I would think that this would require an even more dramatic
boost
to high frequencies. And, in my experience, many people find a
spectrally
flat high frequency portion to be much too bright as it is. I'm
guessing
that the spectral sensitivity of the ear must also be taken into
account
when it comes to devising the "ideal" setup.
While I can't say that I know the final curve shape... I do know it's
nothing resembling flat, and I do know that Chrysler's do sound quite a
bit better than your typical system these days... maybe lacking a bit
in the bass department, maybe not having the fastest decay drivers...
but definitely great in terms of overall frequency response.
Next time a Liberty or other newer Chrysler product is in your shop (or
have a chance to sit in one), take a minute to do a little unexpected
critical listening.
Fun.

The 'target' curve for good sounding cars has a shaped and downward slope to
higher frequencies. A perceptually "flat" response in the car has an overall
3-dB per octave downtilt from bottom to top with a flattened-spot in the
center. The target curve was developed based not only on opinions of other
experts but also on the measurements of vehicles which had high subjective
listening scores based on the Audio Performance Reports that DLC performs for
OEM manufacturers and their suppliers.


Anyway... I know it's nothing resembling flat, because David Clark told
us himself that the measured frequency response wasn't compared to a
"flat" response, but rather a curve that was essentially the product of
his, and a bunch of other audiophiles (AES members?) collective
"average" (if you will) of what they believed to be an ideal frequency
response.

The target curve was based on Subjective Evaluations conducted at DLC Design. I
know this because over the past 5-6 years I've evaluated nearly 600 OEM
vehicles using this technique. FWIW I've also conducted several hundred
aftermarket speaker products for Car Stereo Review and Mobile Entertainment
over the past decade.


THAT curve is what the EQ chips are encoded to aspire to.

And the head wasn't a crash test dummy-like head... it was a treatment
to the heads of the mics, essentially, as I understood. I didn't get
to witness a run of it, unfortunately... I saw the comparator in the
rack of equipment, and got the description.
It was something that Dr. Clark was quite proud of!


--
geolemon

Another way to think about equalization at the listening position is to
consider that if you had a speaker system was perfectly "flat" measured in an
anechoic chamber or in its near field when you re-measure that speaker at a
listening position it will no longer be "flat" but will have a downward sloped
frequency response. The total slope rate will be 1.5 dB/octave in a listening
room or 3 dB/octave in a car.