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Thread: Sharing my tune for feedback: GB60, GB25, GB10. DSP408

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    Noob Julian's Avatar
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    Re: Sharing my tune for feedback: GB60, GB25, GB10. DSP408

    I created a new pink noise file using REW to use. I changed my RTA settings to match it.

    I will post a better photo of acoustic response of the gb25. I had one but I left a filter on in my DSP and then my laptop ran out of juice.
    Last edited by Julian; 05-15-2021 at 10:40 PM.

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    Noob Julian's Avatar
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    Re: Sharing my tune for feedback: GB60, GB25, GB10. DSP408

    GB25 acoustic crossovers:

    Passenger:




    Driver:


    Based on the sharp drop starting at 3k I decided to set my filter to 2500 hz.

    I played around with the crossovers in the DSP to try to get a better match to my target and then tuned.
    I relied too much on the REW auto filters, but tried to make them a bit more efficient manually since I only have 10 filters in the DSP408.



    This is the driver's side after tuning:




    And the passenger side:


    free image hosting service

    And now both together:




    I know it could be better, but I am still learning and it was a good learning experience. If there is anything glaring you see, please let me know. I run out of filters because I am not that efficient.

    Thanks!
    Last edited by Julian; 05-16-2021 at 09:26 PM.

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    Wave Shepherd - aka Jazzi Justin Zazzi's Avatar
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    Re: Sharing my tune for feedback: GB60, GB25, GB10. DSP408

    I also like the idea of using high resolution in the RTA window like 1/48th, then smoothing later when you get to the main REW window since you can change the smoothing afterwards.

    The Max Overlap doesn't need to be that high, could be as low as 50%, but it's a tiny detail that's not too important.

    For matching a target, try to match all the way to at least -20dB down below the average spl level, and down to -30dB if you can. This will help you get the phase to be more textbook-like so that your speakers will sum together better.

    Using a smaller number of eq filters is both challenging and rewarding. I find the highpass and lowpass filters can be very powerful if you're willing to set them unconventionally and they can reduce the number of eq filters you need later. Similarly, shelf filters are also very powerful coarse adjustments. Learning how to be efficient with the number of filters you use is a great skill, but can be very frustrating initially. Try to look for areas where two (or more) filters overlap eachother and see if you can get a similar effect by removing one.

    Jdunk54nl has a lot of good ideas too, please try those.

    If you want to make the center image more focused, you would benefit from more filters. You'll want to play narrow-band pink noise tracks (like 1/3rd octave pink noise) and then listen to where the "center" is for that frequency range. Do this for many different frequencies and you'll find trends like 300-600hz pulls left, 600-1300hz is mostly centered, 1300-3000hz is fuzzy, etc. Then you can make small adjustments to the left and right channels to move the noises towards the center that you want.

    You can make coarse adjustments for frequencies above ~500hz by changing the output trim of the left and right channels. To move the image to the right, drop all of the left channels by -1dB and increase all of the right channels by +1dB. Lower and increase them by the same amount so the overall loudness stays similar.

    You can make adjustments below ~500hz by very subtly changing the time delays. Add or subtract 0.2ms from the left channels and you'll notice the lower frequencies will shift left or right. It doesn't take much. This is easy to notice with a solo deep male vocal like the intro tracks to the Chesky Ultimate Demonstration Disc.

    Keep it up! You're doing great.
    Measure with mics, mark with chalk, cut with torch, grind to fit, sand to finish, paint to match.
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    Senior Member jrwalte's Avatar
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    Re: Sharing my tune for feedback: GB60, GB25, GB10. DSP408

    Very interesting points, Justin. I appreciate it.

    You can make coarse adjustments for frequencies above ~500hz by changing the output trim of the left and right channels. To move the image to the right, drop all of the left channels by -1dB and increase all of the right channels by +1dB. Lower and increase them by the same amount so the overall loudness stays similar.
    I would always just adjust down the side that was pulling the stage and not also increase the other. I feel over time, my total output keeps going down and I had to bump it overall. This is probably why.

    You can make adjustments below ~500hz by very subtly changing the time delays. Add or subtract 0.2ms from the left channels and you'll notice the lower frequencies will shift left or right. It doesn't take much. This is easy to notice with a solo deep male vocal like the intro tracks to the Chesky Ultimate Demonstration Disc.
    I never considered this. Do you feel this is a hard rule, or can you still use EQ to adjust it? Like I notice sometimes adjusting the EQ makes little to no difference until it is a massive change, say 9dB. So in this case, changing time delay may be what helps. But what if 1dB change does shift it? Should you still use time delay instead?

    What about when your mids play down to 300? Should you time delay for it's 300-500 response or just EQ?

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    Noob Jdunk54nl's Avatar
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    Re: Sharing my tune for feedback: GB60, GB25, GB10. DSP408

    In the EQ window, set the scale to 5db increments, you are still at 10 db increments. You have 6-12db swings in some of your frequency response, you need to try to limit that big of a swing.

    I am also going to suggest upping your volume some when tuning. It looks like on the drivers side and when both are playing together, your noise floor is around 30-35db. You can't follow Justin's advice above if your volume is only about 45-50db. Noise floor should stay at the 30-35db, so you need to eq around 70db to be well above that noise floor.
    Last edited by Jdunk54nl; 05-17-2021 at 09:57 AM.
    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

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    Noob Jdunk54nl's Avatar
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    Re: Sharing my tune for feedback: GB60, GB25, GB10. DSP408

    Quote Originally Posted by jrwalte View Post


    I never considered this. Do you feel this is a hard rule, or can you still use EQ to adjust it? Like I notice sometimes adjusting the EQ makes little to no difference until it is a massive change, say 9dB. So in this case, changing time delay may be what helps. But what if 1dB change does shift it? Should you still use time delay instead?

    What about when your mids play down to 300? Should you time delay for it's 300-500 response or just EQ?
    That depends on what frequencies are pulling your soundstage. Is it below 500hz or above? How good is your EQ matching side to side? Or, is it an all pass filter needed and not eq or time alignment?
    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

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    Noob Julian's Avatar
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    Re: Sharing my tune for feedback: GB60, GB25, GB10. DSP408

    Thanks guys, I will take all that into memory and improve on round 2! There was a neighbor mowing while I was trying to tune and I had the truck running for part of the time. That must be what is affecting the noise floor. More volume next time then among the other great tips!

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    Wave Shepherd - aka Jazzi Justin Zazzi's Avatar
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    Re: Sharing my tune for feedback: GB60, GB25, GB10. DSP408

    Quote Originally Posted by jrwalte View Post
    I never considered this. Do you feel this is a hard rule, or can you still use EQ to adjust it? Like I notice sometimes adjusting the EQ makes little to no difference until it is a massive change, say 9dB. So in this case, changing time delay may be what helps. But what if 1dB change does shift it? Should you still use time delay instead?

    What about when your mids play down to 300? Should you time delay for it's 300-500 response or just EQ?
    This is not a hard rule since the effects below does not start and stop at an exact frequency, it's a smooth transition somewhere around 300hz to 1khz (ish).

    Lower frequency sounds have longer wavelengths and our heads are not a significant obstacle to the sound so the wave wrap around our head and keep going. To locate lower frequency sounds, our ears rely on the relative time of arrival between the left and right ears. The ear nearest the sound will hear the sound slightly before the other ear and so small amounts of time delay work great to shift the apparent source of a sound to the left and right. This is sometimes call interaural time difference (ITD).

    Our ears locate the higher frequencies based on the acoustic shadowing of our head because the size of our head becomes significant at the higher frequencies (shorter wavelengths). The ear further from the sound source receives less sound because it's partially blocked by your head so it's quieter, which means you can shift the apparent position of your sound stage by making one side louder than the other. This is often called interaural intensity difference (IID).

    So if your midrange driver plays down to 300hz then the left/right location should be affected by both time delay in the lower frequencies and also loudness in the higher frequencies so you'd want to make both EQ and time delay adjustments on those channels. You midbass drivers that play up to 300hz would benefit from slight time delay changes but you'll likely not hear a difference by making one quiet and one louder unless the change in volume is substantial, like you said 9dB or so. Similarly, your tweeters would likely not shift the sound stage left or right from time delay very much.

    However, time delay and eq changes should be the same for any particular quadrant of the car otherwise you risk upsetting the balance/summing between the speakers in that quadrant. For example time delay on your front-left tweeter won't help the stage move left or right, but it can help the tweeter blend with the front-left midrange driver in that same corner. So if you change the midrange time delay to shift the stage left/right, you might want to shift the tweeter by the same amount even though it won't help shift the image left/right.

    One last trick: sometimes I will adjust time delay by setting a very steep (temporary) lowpass on my front door speakers at like 200-300hz so that I can focus on the lower frequencies only. Then I'll do the opposite and replace that temporary lowpass filter with a temporary highpass filter on the same door speakers so I can focus on the higher frequencies and get the relative left and right loudness/levels correct. Hopefully I'm aligning the "center" for the lower frequencies and the higher frequencies to the same point in the vehicle, then when I take the temporary hp/lp filters off, the center image should be roughly correct although probbably not focused yet.

    Then you move to the 1/3rd octave pink noise tracks to focus the image to a pinpoint location at each frequency band and it's like freaking magic. This is the step that when done well, can really separate a good system from an astonishing system.
    Measure with mics, mark with chalk, cut with torch, grind to fit, sand to finish, paint to match.
    Updated Justin tuning sheet (Justin and Erica tuning companion for SMAART and REW)
    Do it for them.

  9. Back To Top    #19
    Noob Julian's Avatar
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    Re: Sharing my tune for feedback: GB60, GB25, GB10. DSP408

    Im thinking of getting a helix ultra. Eventually I want to be able to tune everything flat within 1-2 db. While that may be possible with 10 filters, it will be a lot easier with the helix and I can use my fiio high res player. Plus I might want to add some center speakers someday. Just not sure if its worth the $ for me and not trying to cop out on learning to tune. I will keep going with the dayton as this is a great way to learn. Kind of like learning to code efficiently when you are limited on memory and processor.

  10. Back To Top    #20
    Noob Jdunk54nl's Avatar
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    Re: Sharing my tune for feedback: GB60, GB25, GB10. DSP408

    You have a 3 way right? You shouldn’t need really more than 10 bands plus crossovers for each driver. I think I have 3-5 eq bands for each driver.

    I’ve found countless times, over tuning a driver and getting it ruler flat +- 1 dB doesn’t make it sound better. Usually this means you tried to fix things that shouldn’t be fixed.

    Your notion is also right. Spending more money isn’t going to fix knowledge. If you can’t maximize the tools you currently have, find THEIR limitations (not your limitations), then you don’t need to upgrade anything.
    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

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