DiyMobileAudio.com Car Stereo Forum banner

41 - 60 of 67 Posts

·
Registered
Joined
·
849 Posts
Discussion Starter #43
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. :D

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....
 

·
Registered
Joined
·
849 Posts
Discussion Starter #44
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)
 

·
Registered
Joined
·
849 Posts
Discussion Starter #45
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. :p :D ;)

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

·
DIYMA Founder
Joined
·
4,786 Posts
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.
 

·
Registered
Joined
·
2,414 Posts
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.:D 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.:D

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.
 

·
Registered
Joined
·
1,778 Posts
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.
 

·
Registered
Joined
·
849 Posts
Discussion Starter #49
Yep, that's a golf club. I think it was my 3 iron. I really like those velvet cord grips too. :D 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....
 

·
Registered
Joined
·
849 Posts
Discussion Starter #50
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!
 

·
DIYMA Founder
Joined
·
4,786 Posts
Were the door treatments going from nothing, to fully treated? I measured a substantial increase in low end sensitivity below 60hz.

I think you'd notice a big difference in your time measurements as well using an accelerometer on the door.
 

·
Registered
Joined
·
849 Posts
Discussion Starter #52
Were the door treatments going from nothing, to fully treated? I measured a substantial increase in low end sensitivity below 60hz.

I think you'd notice a big difference in your time measurements as well using an accelerometer on the door.
Yeah, measurements are comparing nothing to fully treated.

Like your experience, my measurements do also show quite a difference below 50 Hz. I just figured that I'd see a bit more difference in the mid-bass region...

Next time I pull out the laptop and mic, I'm definitely going to look more closely at the time domain responses.

Thanks!
 

·
Registered
Joined
·
114 Posts
shinjohn,

great job with all of the different comparisons!! i have been checking this thread once a week hoping to see your results for a while now.

i had tried measuring with the windows open as well thinking that i would see the effect of fewer reflections and saw very little change of the overall response.

Also, have you found any easy way of averaging readings together (eg. left ear plus right ear) with free software? my past method was to hurry up and move the mic between a series of tests, but it is difficult to see what effect it has that way.

i really like the calibration method that is described for the jbl ms-8, with simultaneous left and right ear capture, but there are no cheap solutions for that right now.
 

·
Registered
Joined
·
849 Posts
Discussion Starter #54
shinjohn,

great job with all of the different comparisons!! i have been checking this thread once a week hoping to see your results for a while now.

i had tried measuring with the windows open as well thinking that i would see the effect of fewer reflections and saw very little change of the overall response.

Also, have you found any easy way of averaging readings together (eg. left ear plus right ear) with free software? my past method was to hurry up and move the mic between a series of tests, but it is difficult to see what effect it has that way.

i really like the calibration method that is described for the jbl ms-8, with simultaneous left and right ear capture, but there are no cheap solutions for that right now.
Glad the data is of some interest to the community here. :D

So far, I have not found an easy way to do spatial averaging, but to be honest, I haven't really tried hard to get more capability with my ultra-cheap measurement setup. I was thinking of buying a nicer setup, but I realize that making time for this hobby is increasingly difficult, however fun it may be.

One thing is for sure though: I have learned a bit about the acoustics of my vehicle, and that has given me some good ideas on how to better tune my system. Of course my ears are the final judge, but sometimes they can use some help! :p

Good luck to you too! Keep up your great work!
 

·
DIYMA Founder
Joined
·
4,786 Posts
If you can dump your IR plot into a txt file... doing a straight average is pretty easy. You could also do it with a FR plot, but may not be as accurate. I mean, let's say at 100hz your left side is 90db, and on the right side is 95db... what's the average right? X+Y/2.
 

·
Registered
Joined
·
630 Posts
shinjohn,

Can you do a comparo between a high qts mid vs a low qts mid? I've always found any low qts mid to sound like what you have measured...can extend very low but not much midbass response despite the deadening.
 

·
Registered
Joined
·
982 Posts
Can you turn the car upside down and suspend it from an 18 foot beam, and then do spatial averaging?

Just kidding. :)
 
41 - 60 of 67 Posts
Top