I have just about completed the system - Audison amp, Focal fronts and Alpine CDA-9857 head unit. BTW the Alpine head unit has a fantastic iPod interface. I needed some more mid-bass control so I added the Alpine PXA-H701 audio processor with a RUX-C701 controller.

The H701 provides full control of the audio sound stage in the car which creates the questions of how do I tune this system. With so many options I may go crazy tweaking the system. However, I figured there must be a rational way to achieve a solid baseline for the sound in my car. Any suggestions or web pointers?

I was thinking of using a Radio Shack Digital-Display Sound-Level Meter with some sort of "test tone" CD - similar to the Avia disk I use to set up my DVD home theater.

Is there any type of "how to guide" out there to get me started?


Thanks!
Jerry

 

http://www.avsforum.com/avs-vb/showt...7&page=1&pp=30
This should help you plenty. It explains how to set up your system using an RTA.

 

use your test tone and set it such that the response curve is flat.

From there, tune to your liking.

 

Update.

I used the Alan Parson Sound Check2 CD with a Radio Shack Sound Level
Meter. Attached is the curve I got - any suggestions?


Thanks!
Jerry

Head: Alpine CDA-9857
Amp : Audison VRx 4.300
Processor: Alpine PXA-H701; Controller: RUX-C701
Sub: JL Audio stealthbox - (2) 10W3v2-D4

 

Your bass at 60 hertz is 30 dB hot - about 1000 times more energy - then the frequencies between 500 Hz and the end of the graph. You need to lower that bass a whole bunch. That's a really rough chart as there's a whole bunch going on inside those points that you've not measured - but it is a really good start.

Here's where I started from using a 1/24th octave analyzer.



I ended up lowering the bass between 20 to 60 hertz about 10 dB and raising the center of the graph - from 100 to about 3K about 5 dB using the two parametric equalizers my Pioneer AVIC N2 has. I've been looking at a 31 band x4 AudioControl equalizer for my next project.

 

Can you point me to the device you used to generate that response curve?

 

I used a spreadsheet. With the following columns:

Frequency
Value (calculated by: SPL measurement + correction)
Measured (SPL measurement)
Correction

Sheet two is the graph of frequency vs. value - automatically updates
when the number change.

It is an OpenOffice spreadsheet - it is attached. I renamed it .doc so it
could upload (it is really .sxc; but should work regardless).


/Jerry

 

that is cool, so you used the meter to get the measured values and individually input them into the spread sheet?


What sort of resolution did you get out of that, sorry I cant open the file to look at it just yet.

 

For each frequency step I recorded the SPL value I got into the spreadsheet. At the end I had the graph I previously posted.
I used a test CD to walk though all the frequencies:


http://www.alanparsonsmusic.com/home.html
Click on "AP Shop"
Click on "Misc Items"
Sound Check 2 $35

 

Cool, I got the file open. So it really is only limited by number of steps the user wants to make.

What is the correction factor?

sorry I am asking all these questions.




Also... as for tuning. I do understand response graphs and with the 30 band EQ you have you can pretty well do anything.

First I would start out with the time alignment thing. The user manual pretty well explains how to do that. From there, take your readings again or just listen for areas you think need to be played with.

 

No problem - same questions I was asking a couple weeks ago when
I started looking into this.

The correction factor is to account for the fact that the SPL is not
totally linear in its accuracy. The correction factor is to fix this
an provide an accurate reading. The SPL should be set to the
slow "C" weighting.


/Jerry

 

I finally got some time over the weekend to tune the system. I knocked down the high 4K frequency just a little. However, when I adjusted the cross overs I was able to get rid of the "harshness" of the sound. Now I'm very happy with the fullness of the sound stage and the imaging is very good - dead center.

Here are the adjustments I made to the cross overs. I'm new to this so any recommendations of other setups to try would be appreciated:

Fronts:
HPfc : 50
HPslope : 6
LPfc : 20K
LPslope : 6

Sub:
HPfc: 20
HPslope: 6
LPfc : 63
LPslope : 12

I'm really happy with the sound now. I'm going to keep my hands off the ***** for a little while to give myself a chance to enjoy the system instead of fiddling with it. Then I will try some other options. I really did not know what I was doing with the slopes - that will be something I will likely tweak. Any guidance?


Thanks,
Jerry

BTW, before I started the cross overs were set as follows:

Fronts:
HPfc : 20
HPslope : -
LPfc : 4K
LPslope : -

Sub:
HPfc: 20
HPslope: -
LPfc : 80
LPslope : 18