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Thread: REW and System Baseline Tune Help

  1. Back To Top    #21

    Re: REW and System Baseline Tune Help

    Quote Originally Posted by ckirocz28 View Post
    Yeah, you'll be hard-pressed to get that 6 db increase from speakers a car width apart, they need to be within a quarter wavelength of each other to get the full coupling effect. Subs and midbass are fairly easy to couple like that, mids and tweets are not. And the reflections absolutely figure into that problem, and all the other nastiness our cars provide.
    It seems that you are absolutely right! I found some old measurements and this is what I see:

    3.5" coaxial dash speakers (play 500hz->20khz) - about a 3dB increase for the entire range of frequencies they play - slightly more at bottom end of frequency range
    6x9" midbass door speakers (play 65hz->500hz) - Mostly ~6dB increase - slightly less at upper range of frequencies
    6.5" coaxial rear-deck speakers (play 75hz->4khz) - ~6dB increase as lower end and ~3db at upper end.

    So it looks like speaker position, frequencies played and possibly reflections and/or phase can all play into this. But generally speaking, at least in my car, the midbass freqs seem to add closer to 6dB and the mid/treble freqs only closer to 3dB.

    In the end, I guess it's really not even a big deal as long as you tune for the difference appropriately. At this point, I'm not going to change anything because of it since I had already taken the relative levels between midbass/mid/treble into account when I originally tuned, so as they say "it is what it is". :-)

  2. Back To Top    #22
    Noob ejeffrey's Avatar
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    Re: REW and System Baseline Tune Help

    I played around more with both REW and the auto-EQ function today and was able to get a good baseline tune that I'll be happy with for a while. The car sounds really good and I'm sure there's a decent amount of improvement to be made by someone who knows what they are doing, so I'm really encouraged.

    Also, I found out what my original issue on this thread was caused by. I had the mode in REW set to "Spectrum" and not one of the RTA settings. So, yeah, don't use that...

    A massive thanks again to those who helped out with this!

  3. Back To Top    #23
    Noob ejeffrey's Avatar
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    Re: REW and System Baseline Tune Help

    After more listening (actually just jumping in the car yesterday morning) I noticed that the most of the image was skewed over to the right, which was mostly corrected by 2 clicks to the left on the balance. Because of this I figured that I may have set the levels wrong before tuning, so I went through the whole process again tonight. Interestingly enough, I ended up with pretty much the same result.

    Is this common? Or more user error?

  4. Back To Top    #24
    Noob Jdunk54nl's Avatar
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    Re: REW and System Baseline Tune Help

    You are on to the tuning by ear part now. Play correlated pink noise and adjust levels on speaker pars until they are centered. Then play band limited pink noise with speaker pairs to center the frequencies even more.
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

  5. Back To Top    #25

    Re: REW and System Baseline Tune Help

    Quote Originally Posted by ejeffrey View Post
    After more listening (actually just jumping in the car yesterday morning) I noticed that the most of the image was skewed over to the right, which was mostly corrected by 2 clicks to the left on the balance. Because of this I figured that I may have set the levels wrong before tuning, so I went through the whole process again tonight. Interestingly enough, I ended up with pretty much the same result.

    Is this common? Or more user error?
    That happens when you use REW's level (calculate target level from response) for each speaker instead of setting them all to the same level (in the eq window, target settings tab, target level). I usually pick the lowest level from the calculated levels and set them all to that. You can just manually adjust the gains in the dsp accordingly.

  6. Back To Top    #26

    Re: REW and System Baseline Tune Help

    So while investigation the whole "how much of an increase do you see when playing both left/right speakers at the same time?" thing, I noticed what appear to be some phase-related issues with my current setup (at least I think they are phase-related issues).

    The picture below shows the individual left/right door speaker and individual left/right dash speaker responses - along with the purple "both speakers playing" response. I'm guessing that the circled areas are caused by phase issues? The one dip also causes my crossover area to go from 500hz down to 435hz when both left and right speakers are playing.

    So my question is... Should I attempt to "fix" the dips with EQ by adding equal amounts to both the left and right speakers in order to "fix' the dip when both speakers are playing (which would also bring my crossover freq back to 500hz)? Or should I just leave them be?

    Thoughts? Opinions? Also, note the small dB increase with both dash speakers playing compared to the larger dB increase with both midbass speakers playing (which was the topic originally being discusse here).



    Also, with the dash speakers, the areas to the left and the right of the red circle actually seem to be *higher* that normal (instead of a dip) - would I also decrease those areas with EQ (again, to help bring the crossover point back to 500hz)?

    Thank you!

  7. Back To Top    #27

    Re: REW and System Baseline Tune Help

    You seem to have a 6db summation (ideal) in some areas below the crossover on the dash speakers, and just under above that frequency also... personally as long as the frequencys around that point are centred when played on speaker pairs I wouldn’t adjust it, sometimes the mic picks up stuff that the ear doesn’t... sometimes the mic doesn’t pick up what the ear does... for fine tuning I prefer to check with test tones and the ears

  8. Back To Top    #28

    Re: REW and System Baseline Tune Help

    So I have a stupid question about tuning to a target curve... I've always noticed that my measured frequency response always came out different than the target curve I was tuning to and never understood why. However, when I found that I was getting ~6dB increase when both midbass speakers play and only about a ~3dB increase when both mids/tweeters play (2-way dash speakers), then it made sense. :-)

    So if I EQ each speaker towards a target curve in REW using the same "Target Level" value for each speaker, the midbass freqs will always end up about 3dB higher than the mid/high freqs, thereby making the resulting frequency response not match the curve I was tuning to.

    I'm thinking that the easiest way would probably be to set the "Target Levels" to different values in REW depending on whether I'm tuning a midbass speaker or a mid/highs speaker? For example, if my "Target Level" is 65dB for my mid/highs speaker, maybe I should set the "Target Level" to 62dB when EQ's the midbass speakers? That way, when both left/right speakers play together, the result should match my target curve correctly. At least that is my expectation... I think I'll give that a shot.

    Just curious how others handle this since the level of summation for left/right speaker pairs seems to be different depending on the specific speaker and frequencies it plays (at least in my car).

  9. Back To Top    #29

    Re: REW and System Baseline Tune Help

    You should get 6db of summation when two speakers play together, if not they are not in phase with one another (this is why LR 24db crossovers work, the crossover point is 6db down and in phase so the average level through the crossover becomes flat when summed

    watch some sound design videos from Nathan lively for more info, good guides on phase and levels (even though it’s more commercial sound and not automotive, the rules don’t change... we just get more phase anomalies to deal with )

  10. Back To Top    #30

    Re: REW and System Baseline Tune Help

    Quote Originally Posted by dumdum View Post
    You should get 6db of summation when two speakers play together, if not they are not in phase with one another (this is why LR 24db crossovers work, the crossover point is 6db down and in phase so the average level through the crossover becomes flat when summed
    Hmm... Well, if they are not completely in-phase, I'm not so sure I can really do anything about it. Wiring polarity is correct, time alignment is correct and I'm using LR 24dB xovers - what else can I do?

    Above, @ckirocz28 mentioned this:

    "Yeah, you'll be hard-pressed to get that 6 db increase from speakers a car width apart, they need to be within a quarter wavelength of each other to get the full coupling effect. Subs and midbass are fairly easy to couple like that, mids and tweets are not. And the reflections absolutely figure into that problem, and all the other nastiness our cars provide."

    and @SkizeR confirmed that:

    "Yup. Probably caused by reflections"

    I took those comments to mean that "it is what it is" and that there really isn't much I can do about it with the way the speakers are installed (factory locations - aiming striaght up into the windshield).

    If that is the case (that there is not much I can do about it), probably the best I can do is to add 1.5dB to "Target Level" when EQ'ing the dash speakers in REW and subtract 1.5dB from the "Target Level" when EQ'ing the door midbass speakers in REW. That would give me my 3dB difference and make it so the resulting frequency response would pretty much match my target curve. I think. :-)

    Or am I missing something here?

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