DerrickM

Hi Everybody. This is really directed at Elduderino, but please feel free to jump in with any insights.

It's been a couple of months and I finally got my hands on an RTA with an instrument-grade microphone. (Behringer 8024). The system has been sounding great with the eq set flat, but I still wanted to put an RTA on it to see if any tweaks needed to be made.

Here's a sample of the first reading. I have a spike around 50Hz, but I can't tell how bad it really is until the wind dies down. (It's showing a bunch of signal at the low end even with everything turned off because of the weather).

I like my treble kind of low, so my crossovers are set with the tweets in the low position up front, and the medium position in the rear.

How does this look? (I don't know how to figure dB from the little display, since it doesn't seem to be labelled).

DerrickM

That sure came out small; here's the original jpeg:

http://img.photobucket.com/albums/v6...kM/RTA0004.jpg

elduderino

1) Where was the mike?

2) Was anyone in the car when the measurement was taken? I've found that humans soak up HF energy : )

3) What is the vertical scale? (Between the dots?) Oh, it's not labeled... just read that. Is there a mode that changes the scale, so you can re-check what mode it's in?

4) You have a/d/s/ in the F of the car, right? It looks like youhave a spike at the xover point (2500 Hz) I would try reversing polarity to both tweeters and see if that smooths out.

5) Any "distance" to vocals? That dip at 400 Hz might indicate that... but it's at a freq that can become really honky if you boost it. If it's an artifact of the car and the speaker location relative to the mike location, AND the mike is located at the listener's head position, you might have to live with it... or you might reverse polarity of the R speaker relative to the F speaks and re-check.

6) That drop at 16k and more at 20K might be an artifact of mike location ... but you might be able to get some more "air" if you EQ that. Usually the notes we associate with the differences between silk-dome and metal-dome tweeters are significantly lower than that...

See what tuan209 thinks...

dark inspire

wow, this thread is way above my head

DerrickM

Hi.

I started with the mic at head level, but then moved it to the center console--the readings seemed pretty consistant. (I was in the driver's seat at the time--main reason I moved it; so I could get readings with my body in the seat).

I did some research, and the dots on the display are 6dB apart. Yikes, the response is much further off than I would have guessed.

The DLS are in the front, the a/d/s are in the rear. Nope, don't hear any problems such as distant vocals.

Also, my test disk sucks. I don't have a steady white noise track--one track alternates between left and right, and the other alternates between in-phase and out-of-phase. I need a better test disk.

Also, I'm loathe to admit it, but the rears are much further off than the fronts and my eq only does 3 bands in the rear. Rear fill issues...

elduderino

http://www.crutchfield.com/S-TopYWHV...asp?i=503CD103

I would not aim for flat, but for a shape like a Fl-Mun curve.

elduderino

Oh, and Derrick, your RTA ain't that bad... try RTA'ing your home stereo setup.

DerrickM

Okay, here's the latest. I used EAC to make an 8 minute pink noise track so I didn't have to deal with the on/off test disk that I had.

My eq settings ended up being:

30 -6
45 -6
270 +3
400 +6 (sounds a little boomy, i'll put that down a bit)
840 -1
1.2k -6 (I adjusted it to -4 after listening to some music)
1.7k -3
3.6k +2 (crossover region)
16 +6 (I adjusted it to +3 after music listening)

I discovered that the peak at 40/50Hz could not be corrected with the EQ, so I put it at -6. I might adjust that up after hearing more music.

I didn't worry too much about smoothing the sub-125Hz with the above 125Hz because that's my sub crossover--I can just turn down the sub if I think it sounds better.

I'm not sure how much faith to put into this whole exercise, because when I open the trunk the bass is overwhelming, but the RTA only indicated a moderate increase in the sub-125 frequencies.

I'll spend a couple days switching back and forth from flat to the new eq curve to verify that this is an improvement.

Here's the RTA readout:

http://img.photobucket.com/albums/v6...kM/RTA0007.jpg

elduderino

Pic looks good... but you neglected to say if you thought it sounded better... : )

DerrickM

Well, it'll take me at least a day or two to decide if it sounds better. I mean, we're talking about small changes.

The most noticable changes were the boost at 400 and the cut at 1.2 and 1.7. Both of those I'm cutting back after listening to music. +6dB @ 400Hz gave it a slight boominess. -6dB at 1.7k seemed to take a little something out of the upper mids.

I had no idea this would be so difficult. Like I said, it sounded great before; but without instrumentation I'll never know if there's peaks or valleys that need attention.

Tomorrow I'll drive the car with my normal *insane* volume levels and see how it sounds...