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My new system! pics


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kfr01 
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Posted: July 27, 2004 at 8:12 PM / IP Logged  

Thanks for the post, Dave.  Quite informative.  Your soapbox info re: EQ's is something you just can't find anywhere other than from the mouth of pros.

New Project: 2003 Pathfinder
Leif 
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Posted: July 27, 2004 at 8:26 PM / IP Logged  
Thanks for your reply Dave, you're absolutely right!
It's not that great (i really only bought it because it was inexpensive) - and I really couldn't flatten out the RTA response all that much. I attribute most of the peaks/valleys to room response / microphone placement, but the EQ wasn't able to correct narrow peaks and valleys. It IS able to correct for the resonance in the kickpods around 150hz though, and phase errors really only occur if you do wild boost/cuts, which I'm not doing.
Hum was a (barely) audible problem, but it's not any more. I went through the entire system with a scope, making sure the signal is as hot as possible every step of the way, while still staying a couple of dB's from clipping.
For example, I learned that over volume 25, the alpine head unit adds nothing but distortion. (Volume control goes up to 35).
Utilizing the +18dBu output stage of the alesis eq (that's 6 volt pre-out in car audio language) and turning the gains on the amps all the way down, I was able to get rid of the noise completely. As in, with the engine on and my ear against the speaker, I can't hear it at all :). Neither hum nor alternator whine.
That being said, at some point I certainly wouldn't mind upgrading. Being an audio software engineer, it really bugs me how much gear you need to accomplish such simple things as crossovers and equalization!
It'd take me less than a day to write software to do this. With an FFT I could do completely phase linear equalization.. So, next time i feel the need to upgrade I'll probably have to go digital. A 2-in 6-out programmable DSP platform (something like a UCS PRO I guess, except I'd rather do it myself) would be ideal. Maybe later :).
At the moment, the MEQ-230 does much more good than bad. In fact I don't hear any phase problems at all, and it does have convenient bypass switches so I've been able to A/B it easily.
///Leif
Leif 
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Posted: July 27, 2004 at 8:35 PM / IP Logged  
By the way, here's my measured RTA response. (I used the TrueRTA application, with a Behringer ECM8000 microphone connected to a Motu 828 firewire audio interface.)
My new system! pics - Page 3 -- posted image.
I've never used (or had) an RTA system before, I just bought the microphone although I had the other parts already.
It seems that the placement of the microphone matters a lot for high frequency response. Even just moving it a couple of inches changes things. I had the microphone between the driver seat and headrest, pointing forward (i.e. right about where my nose would be had I been sitting there), windows down, and I was outside the car when I measured.
Anyway, is this a workable RTA approach, or should I rethink/redo things?
///Leif
Leif 
Copper - Posts: 71
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Posted: July 27, 2004 at 8:43 PM / IP Logged  
Man, that response looks really sh*tty, doesn't it?
///Leif
kfr01 
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Posted: July 28, 2004 at 1:51 PM / IP Logged  

Leif, I also just bought the same mic and truerta software.  It seems to be a pretty good solution considering that stand alone RTA's are much more expensive.

I think your response looks pretty good! I'm just starting to play around w/ RTA / EQing too, but I read somewhere that a good goal to start with is to smooth the 1/3 octave transitions to around less than +-3db.  I can only count 5 places on your curve where this isn't true on your curve.

As I'm going through the same experience here's a shot of the critical midrange area I'm working on now:

This whole process is fairly frustrating.  The Eclipse Hu 5 band quasi-parametric EQ isn't doing the trick.  The Q is either too narrow or too wide with the 3 position Q configuration on the unit. 

My new system! pics - Page 3 -- posted image.

New Project: 2003 Pathfinder
kfr01 
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Posted: July 28, 2004 at 5:25 PM / IP Logged  
Sorry for the crappy cropped picture.  30k limit on pic uploads gets small.  :-)
New Project: 2003 Pathfinder
DaGr8n8 
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Posted: July 28, 2004 at 7:58 PM / IP Logged  
pretty freake n tite system if i have to say so my self!!!!!!!!!!!!!!!!!!!!!
Leif 
Copper - Posts: 71
Copper spacespace
Joined: July 15, 2004
Location: United States
Posted: July 28, 2004 at 10:02 PM / IP Logged  
Kfr01, I do wonder how much of this is due just to microphone placement. I mean, for higher frequencies moving the mic really changes things.. Although the same can't be said for midrange frequencies like this, I suppose.
How are your speakers mounted?
Oh, and check this out:
My new system! pics - Page 3 -- posted image.
Just finished that :).
///Leif
kfr01 
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Posted: July 29, 2004 at 12:05 AM / IP Logged  

Looks great man.  I also wonder about the accuracy of the truerta/behringer mic setup.  Almost makes me want to call around to car audio stores and see if they'll just take 5 minutes to measure my system to compare the results. 

My components are mounted in the lower door position. 

New Project: 2003 Pathfinder
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