A Compartive Study of Loudspeaker Frequency Response in Car Doors - Page 2 - Car Audio | DiyMobileAudio.com | Car Stereo Forum

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Old 07-14-2007   #26
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

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Originally Posted by npdang View Post
Try sitting in the driver's seat when measuring. It throws everything out of whack Also, can you do any sort of spatial averaging?
Another great point to concider a JBL MS-8 with its wear while tuning binaural microphone.
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Old 07-14-2007   #27
 
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

Great idea to compare the two drivers!!

I used ARTA (with a ECM and MobilePre) for some measurements as well, and the only problem was the inability to save data with trial version.

I was undecided on whether the drivers or Car were responsible for the frequency response i was getting, but your results make it pretty clear.

In my tests, there were variations in the midrange depending on microphone placement (+/- 2 inches made a huge difference). The midbass and high end seemed pretty stable.

I was going to try moving the microphone around like npdang had done to average the "left and right ear" response, but I hadn't figured out a good way to do that with a free program yet. I tried moving it between passes, but i'm not sure the results are accurate that way.

I would be interested to know if you observed the same thing with microphone placement considering that you are using the exact same setup i tried.

Last edited by jmelan; 07-14-2007 at 08:55 AM..
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Old 07-14-2007   #28
 
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

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Originally Posted by chuyler1 View Post
The open door idea sounds good...and place the mic about 1 meter away outside the car. That should give you a readout of the enclosure as if it were in a vacuum...well almost.

That is just such a huge difference in output below 100Hz between L and R it makes me wonder if that is what you hear when you listen.

Perhaps the seal around the driver wasn't as good on the left?
I had very similar results in my Car with RS180s right below 100 Hz. The left drops off faster than the right in every test I have done.
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Old 07-14-2007   #29
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

Quote:
Originally Posted by npdang View Post
Try sitting in the driver's seat when measuring. It throws everything out of whack Also, can you do any sort of spatial averaging?
Time to read the ARTA manual more thoroughly. I thought it has something like that built in, but I'll have to double check. Sounds like jmelan didn't have any luck though...

Quote:
Originally Posted by jmelan View Post
Great idea to compare the two drivers!!

In my tests, there were variations in the midrange depending on microphone placement (+/- 2 inches made a huge difference). The midbass and high end seemed pretty stable.

I was going to try moving the microphone around like npdang had done to average the "left and right ear" response, but I hadn't figured out a good way to do that with a free program yet. I tried moving it between passes, but i'm not sure the results are accurate that way.

I would be interested to know if you observed the same thing with microphone placement considering that you are using the exact same setup i tried.
I'm going to play around more today and tomorrow and see. I'll let you know. I'm thinking of trying "left ear" position (already did "right ear"), center of car, and passenger side to be thorough.

Quote:
Originally Posted by jmelan View Post
I had very similar results in my Car with RS180s right below 100 Hz. The left drops off faster than the right in every test I have done.
Very interesting.... and good to have some other confirmation of these results!

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Old 07-14-2007   #30
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

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Originally Posted by shinjohn View Post
I could probably do that. At this rate, I'm going to be generating tons of plots/data. Hope I don't crap out the server even more!
It might be kind of hard to get good results if your environment around you isn't quiet. I tried something like this before but the garage was way too noisy to get good results or anything worth a crap for analyzing. I hope it works out.

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Old 07-15-2007   #31
 
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

this is probaly to much to ask, but if you get a chance to measure some doors with AP enclosures in the future would love to see how that helps or not, thanks for the results
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Old 07-18-2007   #32
 
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

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Originally Posted by jmelan View Post
I had very similar results in my Car with RS180s right below 100 Hz. The left drops off faster than the right in every test I have done.
Is your leg getting in the way?

I'd bet just having a "soft" mass in the general vicinity of the front of the Speaker would cause a loss of output. Well, a loss of energy from the speaker, to the diaphram of the mic...especially if you are between them.





I'm not calling you soft. hehe
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Old 07-20-2007   #33
 
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

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Originally Posted by chuyler1 View Post
The open door idea sounds good...and place the mic about 1 meter away outside the car. That should give you a readout of the enclosure as if it were in a vacuum...well almost.

That is just such a huge difference in output below 100Hz between L and R it makes me wonder if that is what you hear when you listen.

Perhaps the seal around the driver wasn't as good on the left?
I found similar measurements in my Car and I also thought that the seal was not as good, but I remember the results being reversed when I moved the mic to the other side.

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Old 07-20-2007   #34
 
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

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Originally Posted by shinjohn View Post
One thing I am considering is buying a (better) calibrated mic. The ECM seems to work fine, but it doesn't have a calibration curve, so there's some (unknown) absolute measurement error. For this study, it's no problem because I'm looking more for relative results. But if I want to be more serious about this in the future, a better mic is probably in order. Just FYI.
ECM is pretty darn flat. TrueRTA software comes with a calibration file for it and I'll try to find and post a screenie of the correction here, but I recall that it was just very slight roll-off in the highest highs and lowest lows, something on the order of 1-3db.

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Last edited by Astral; 07-20-2007 at 03:41 PM..
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Old 07-20-2007   #35
 
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

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Originally Posted by Astral View Post
ECM is pretty darn flat. TrueRTA software comes with a calibration file for it and I'll try to find and post a screenie of the correction here, but I recall that it was just very slight roll-off in the high and mid freqs, something on the order of 1-3db.
Here's a good thread on the ECM-8000.
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Old 07-20-2007   #36
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

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Originally Posted by Locke View Post
this is probaly to much to ask, but if you get a chance to measure some doors with AP enclosures in the future would love to see how that helps or not, thanks for the results
It won't help at all in that respect.

A speaker is only as good as the room you put it in.
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Old 08-02-2007   #37
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

Bump for updates and any of those whom may find this post interesting. I know I did. :]
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Old 08-03-2007   #38
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

Sorry.
Just been a little busy (and I must admit, lazy) these days...
I have data from other positions, door open, and I deadened a door last weekend. I'll post some new results this weekend.

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Old 08-04-2007   #39
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

Haha, sounds like me and my current install. There gear is coming in, yet the install is at a stand-still. I mainly wanted other users to check out your findings :] I'd be interested in finding out the thickness of f/b required to simulate a type "x" wood enclosure and compare the various "matting" fabrics for better responses. Seeing as how many of diy go the f/b route or mdf baffle door installs. Density consistency is a big factor in choosing an enclosure. So, I'll stop rambling and await new results.
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Old 09-30-2007   #40
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

OK, I'm going to attempt to "catch up" a bit on what I've been up to.

First, here are measurements I took varying microphone position across the vehicle.

Setup
  1. doors not yet deadened in these measurements
  2. Seas Lotus RW165s
  3. 5 mic. positions, about head high, approximating:
    • driver's left ear
    • driver's right ear
    • center of vehicle
    • passenger's left ear
    • passenger's right ear
  4. everything else as before

Results
Left Speaker Measurements:


Right Speaker Measurements:


Note that, as expected, microphone position dramatically impacts measured response.

Here's what interesting: the Car does, for the most part, act quite symmetrically. Below, I've plotted symmetric measurement positions across the vehicle, and you can see that responses are very similar. Of course a Car isn't perfectly symmetric, but my car isn't too bad in this regard.





Looking at the responses more carefully, there's lots of interesting things to note. A couple of comments:
  • bass response is worse as you get closer to the speaker
  • cone breakup for this speaker is MUCH more noticeable the more on axis you are.
  • even frequency response in two seats is not an easy accomplishment.

much more soon to come....

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Old 09-30-2007   #41
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

Excellent... let's see the time response for those measurements

A speaker is only as good as the room you put it in.
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Old 09-30-2007   #42
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

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Originally Posted by npdang View Post
Excellent... let's see the time response for those measurements
LOL. Unfortunately, I only exported the frequency domain plots of all my measurements and ARTA (demo) doesn't allow me to save the raw data. I need to upgrade my setup.


Last edited by shinjohn; 09-30-2007 at 07:10 PM..
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Old 09-30-2007   #43
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

Here's my attempt to "eliminate the room" by measuring door Speaker response with the door wide open. Here's what my setup looked like:



I plotted response against right door Speaker response measured at driver's ear inside the vehicle. One thing to note is that I significantly increased drive level with the door open so as to reduce the impact of outside ambient noise (I live near a freeway). Keep that in mind when looking at the next plot.



If this isn't proof of Nguyen's quote: "A speaker is only as good as the room you put it in." then I don't know what to say.

It's very easy to see how much smoother the response is without the harsh room (car) environment. It is also very obvious that cabin gain has a HUGE impact on bass response. Bear in mind that the door in these measurements has yet to be deadened, so you wouldn't expect the response to be super smooth; the enclosure still sucks rocks.

More coming....

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Old 09-30-2007   #44
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

OK. Let's now look at door treatments.

Click here to see how I treated the front doors:

http://www.pbase.com/shinjohn/accordstereo2&page=all

I pretty much did it the Rick McCallum (Raamaudio) way.

A couple of notes on my method:
  • I like to work fast and efficiently, so you'll notice I cut rectangular strips and used the overlap method.
  • This also allowed me to put extra layers where I needed it more, and less material in places that were very solid.
  • I used the tap test and my own threshold of what I thought was "dead enough".
  • I put ensolite on the door panel instead of directly on the door itself for better future ease of service.
  • I avoided covering fasteners because I've had to get inside these doors more than once!

Now the data:
Left door, in comparison with untreated baseline:


Right door, in comparison with untreated baseline:


My key take aways:
  1. Door treatments do improve bass response. (correlates to subjective experience)
  2. Door treatments (foam) do smooth out midrange response. (correlates to subjective experience)
  3. The Car transfer function is still the most dominant factor in frequency response. (i.e.- regardless of what you do with install/speaker placement, you'll need to do some electronic manipulation/eq if you are aiming to get relatively flat frequency response)

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Old 09-30-2007   #45
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

Moving on.....

What happens when you open the windows?

Plots below comparing windows open vs. windows closed baseline. Mic still at driver's ear, doors have been treated per above post. Both front windows were open during measurements. Rear windows were still up.

Left Door Speaker


Right Door Speaker


Take away:
Don't drive around with your windows open.

I think you guys have enough data for today. Questions, comments, suggestions always welcome. Enjoy!

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Old 10-01-2007   #46
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

Is that mic taped to the end of a golf club :P

Glad to see you taking your own measurements. I've had such a hard time trying to find a way of measuring that actually correlates well with what I'm hearing.

So far, what I find measuring most useful for is 1) level setting 2) verifying crossover points 3) time alignment 4) and finding unusually large peaks in the midrange.

What I find it completely useless for (as far as the methods I've tried) is actually tuning for flat response, setting up the subwoofer tonally, and tuning from the upper midrange and top end beyond 10khz.

A speaker is only as good as the room you put it in.
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Old 10-01-2007   #47
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

Quote:
Originally Posted by npdang View Post
Glad to see you taking your own measurements. I've had such a hard time trying to find a way of measuring that actually correlates well with what I'm hearing.

So far, what I find measuring most useful for is 1) level setting 2) verifying crossover points 3) time alignment 4) and finding unusually large peaks in the midrange.

What I find it completely useless for (as far as the methods I've tried) is actually tuning for flat response, setting up the subwoofer tonally, and tuning from the upper midrange and top end beyond 10khz.
Cool. I think I have experienced the same things.

Thanks Shin John for taking the time out to do this and thanks for taking measurements with the windows down. I think I experience the peaky repsonse at 60Hz and then a massive dip around 100Hz with my windows down too. Note to self use A/C instead of windows.

Hey Shin-

When you tested at head positions, was the mic facing directly forward or was it turned to each side. I don't know how much it will affect your measurements but it seemed to make a difference for myself right aroudn the midrange area between 1-2Khz (might be window reflections I dunno). One of these days I need to start capturing data myself.

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Old 10-01-2007   #48
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

Quote:
Originally Posted by npdang View Post
Is that mic taped to the end of a golf club :P

Glad to see you taking your own measurements. I've had such a hard time trying to find a way of measuring that actually correlates well with what I'm hearing.

So far, what I find measuring most useful for is 1) level setting 2) verifying crossover points 3) time alignment 4) and finding unusually large peaks in the midrange.

What I find it completely useless for (as far as the methods I've tried) is actually tuning for flat response, setting up the subwoofer tonally, and tuning from the upper midrange and top end beyond 10khz.
Sounds like my experiences. My ears are a far better tuning instrument than any microphone/rta in a car. The RTA helps me find the right band to tune if I have already determined it by ear but any anomaly in the RTA curve that I haven't discovered on my own is usually not worth pursuing.

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Old 10-01-2007   #49
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

Yep, that's a golf club. I think it was my 3 iron. I really like those velvet cord grips too. Well, it's all that I had around at the time to use, LOL.

Anyhow, thanks for the comments, guys! My intent hasn't been to use this data as gospel per say in tuning my Car a particular way, but as a tool (just like anything else we do) to try to better understand and give me some direction. Also, what can I say, I was just curious how things would measure.

What's encouraging to me is that I can at least measure some differences (though there is also some measurement error) and many things seem to make some sense and echo my subjective experience. What I can't reconcile really is the absolute measurements themselves. A +/-10dB swing in response is pretty darn big, and to me it doesn't subjectively sound that bad....

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Old 10-01-2007   #50
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Default Re: A Compartive Study of Loudspeaker Frequency Response in Car Doors

One other thing I would say in this thread is that I really think that door treatments subjectively make the biggest difference in bass response; much more than the compartive measurements would suggest. Something I'm still scratching my head a bit on..... It's not subtle; it's very substantial subjectively!

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