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Thread: Tuning midbass drivers...the struggle continues

  1. Back To Top    #11

    Re: Tuning midbass drivers...the struggle continues

    Quote Originally Posted by Pb82 Ronin View Post
    Why use a "box" at all? Is it not possible to just run an adapter and use the door as the box (like a factory install)? I run an 8" Dayton woofer in my door (in a Corvette) and it only took 2 EQs to get it almost perfectly flat. Another question is, what is yours doing? When you make EQ changes, does the curve even move?
    The location of the woofer on a door - regardless of a good baffle, enclosure, etc - just the physical location at the front corner of VERY many doors, relative to the dash, seats, console, glass, roof, etc...
    The complex reflections from that location to the listening location at your head VERY often results in a common midbass null.
    A corvette is a wider, lower-roof car with a more angled windshield and entirely different shape hatch and taller center console, so you may simply be lucky with that car.

    And to the OP - I suspect this is the real issue you are facing, although that plot looks like an oddly shallow rolloff rather than a sharp dip like most reflection/cancellation interior/location based nulls...
    So the first thing I'd try is replacing the eights (which might be in a "too small" enclosure) with 6.5s that have a low Fs - to eliminate the chance that the cavity is simply too small.

    (And if it is - one option for running the eights would be drilling a big hole or three with a hole saw right through the rear of that enclosure, so that they are actually running open baffle)

    You don't necessarily need to go to the extreme of running a midbass in an infinite baffle outside your car (although DumDum is and it's impressive - see his build thread), but moving the midbass cabinets under the seats is a strategy to eliminate the midbass nulls by fundamentally changing where the primary sound source is located - therefore changing ALL the reflections and sound paths to your ears.

    So is adding additional identical midbass drivers elsewhere in the car - either equal distance to your ears, or delayed to effectively be time aligned.

    Or even, you could run your sub up higher, to be that additional midbass driver.

    Sent from my LM-G710 using Tapatalk

  2. Back To Top    #12

    Re: Tuning midbass drivers...the struggle continues

    Quote Originally Posted by geolemon View Post
    The location of the woofer on a door - regardless of a good baffle, enclosure, etc - just the physical location at the front corner of VERY many doors, relative to the dash, seats, console, glass, roof, etc...
    The complex reflections from that location to the listening location at your head VERY often results in a common midbass null.
    A corvette is a wider, lower-roof car with a more angled windshield and entirely different shape hatch and taller center console, so you may simply be lucky with that car.

    And to the OP - I suspect this is the real issue you are facing, although that plot looks like an oddly shallow rolloff rather than a sharp dip like most reflection/cancellation interior/location based nulls...
    So the first thing I'd try is replacing the eights (which might be in a "too small" enclosure) with 6.5s that have a low Fs - to eliminate the chance that the cavity is simply too small.

    (And if it is - one option for running the eights would be drilling a big hole or three with a hole saw right through the rear of that enclosure, so that they are actually running open baffle)

    You don't necessarily need to go to the extreme of running a midbass in an infinite baffle outside your car (although DumDum is and it's impressive - see his build thread), but moving the midbass cabinets under the seats is a strategy to eliminate the midbass nulls by fundamentally changing where the primary sound source is located - therefore changing ALL the reflections and sound paths to your ears.

    So is adding additional identical midbass drivers elsewhere in the car - either equal distance to your ears, or delayed to effectively be time aligned.

    Or even, you could run your sub up higher, to be that additional midbass driver.

    Sent from my LM-G710 using Tapatalk
    Thanks for the reply,

    I've already cut a 4" vent directly behind the driver that vents into the door cavity. I was assuming that would adequately make the enclosure IB.

    I'm aware that moving the drivers could help eliminate nulls.

    Sealing the enclosures back up and installing a proper sized 6" driver is tempting but finding something with enough output to blend with my subs could be challenging.

    The reason I went with 8" midbass was for more output and the ability to set HPF lower. It turns out that wasn't really necessary needed but i do enjoy the extra output.

    I'm going to spend some more time tinkering with things this weekend. Some test boxes and moving the midbass to the kick panel area sounds like a fun experiment.


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  3. Back To Top    #13
    Noob Jdunk54nl's Avatar
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    Re: Tuning midbass drivers...the struggle continues

    Peerless sls 6”. Cheap, perfect for 3 way (they don’t work well over 500hz), and they keep up in my truck and Justin Zazzi’s car (quite a bit of Xmas too, way more than your sw800’s).
    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 Ge0's Avatar
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    Re: Tuning midbass drivers...the struggle continues

    Not bad for your first attempt. Good enough for what you are trying to do now. You can always go back and make them look prettier later.

    I'm curious, what is the internal volume? Seems big enough for a midbass. Did you experiment with packing the cavity with more polyfill?

    What is stumping me is the rapid drop off in response around 130Hz, especially with a hole cut in the box behind the driver.

    Also, what the heck is causing your right midbass to attenuate above 180Hz?

    Ge0
    Scanspeak - Dynaudio - Helix - Bose

  5. Back To Top    #15
    Noob Ge0's Avatar
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    Re: Tuning midbass drivers...the struggle continues

    I just thought of something. Most drivers require 2" or more of clearance behind the magnet structure for the pole piece to vent properly. Are you sure the 4" hole you hogged out is directly behind the driver? Or, in other words, does the speakers pole piece vent directly into the hole or is it partially obstructed by the back surface of the box?

    Maybe leave the AD SW800's for now and try making that 4" hole a 6" hole? As others have said, try adding a few more holes to the back side of your box to make sure it vents well enough. Maybe you're getting some weird pressure build up even though you cut a 4" hole.

    Ge0
    Scanspeak - Dynaudio - Helix - Bose

  6. Back To Top    #16

    Re: Tuning midbass drivers...the struggle continues

    Quote Originally Posted by Ge0 View Post
    I just thought of something. Most drivers require 2" or more of clearance behind the magnet structure for the pole piece to vent properly. Are you sure the 4" hole you hogged out is directly behind the driver? Or, in other words, does the speakers pole piece vent directly into the hole or is it partially obstructed by the back surface of the box?

    Maybe leave the AD SW800's for now and try making that 4" hole a 6" hole? As others have said, try adding a few more holes to the back side of your box to make sure it vents well enough. Maybe you're getting some weird pressure build up even though you cut a 4" hole.

    Ge0
    No way its exactly centered. I literally just grabbed my hole saw and ran it through without much thought. I was assuming air wouldn't care. I think it's time for a bigger hole.

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  7. Back To Top    #17

    Re: Tuning midbass drivers...the struggle continues

    Quote Originally Posted by JerryGash View Post
    No way its exactly centered. I literally just grabbed my hole saw and ran it through without much thought. I was assuming air wouldn't care. I think it's time for a bigger hole.

    Sent from my SM-G955U1 using Tapatalk
    Or just behind the driver.

    Any speaker that has a vent out the back of the speaker needs rear clearance equal to the diameter of that vent, or else there will be a vacuum effect that restricts cone motion. That can definitely impact frequency response progressively, as it directly impacts excursion (which naturally increases exponentially as frequencies decrease).

    Ge0 could be dead on correct.

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  8. Back To Top    #18

    Re: Tuning midbass drivers...the struggle continues

    Quote Originally Posted by Ge0 View Post
    Not bad for your first attempt. Good enough for what you are trying to do now. You can always go back and make them look prettier later.

    I'm curious, what is the internal volume? Seems big enough for a midbass. Did you experiment with packing the cavity with more polyfill?

    Ge0
    I had to do some searching through my old build threads to find it but the measured volume ended up to be around. 37 cu. ft.

    I think the Peerless SLS recommended volume was .7 cu. Ft.

    I've seen people have tiny enclosures for midbass drivers before. I'm not versed well enough to understand if the recommended volume is only if you plan on playing them down to Fs or if a smaller volume is OK if you plan on crossing them higher.

    In my mind if crossing well above Fs the enclosure could be smaller than the recommended volume but that's only my assumption.

    I had them stuffed tightly with poly-fil at one time.



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    Last edited by JerryGash; 12-18-2020 at 06:53 AM.

  9. Back To Top    #19

    Re: Tuning midbass drivers...the struggle continues

    I guess that midbass plot doesn't look all that bad to me. Are you primarily concerned with the lower end rolloff ? Its not like its that steep ? Or you could shelf filter the upper end and just play it. I admit I woudl expect there to be a little more bass given the expected acoustical loading. If it was a too small enclosure issue then I would expect a big high q frequency bump before the rolloff. Maybe that's as good as it gets for those drivers ? Another experiment, open your door all the way and put the mike close to the speaker and see what that response looks like.

    I am a little intrigued by this post because I'm a huge believer in door enclosures so I am inclined to defend them. If you stick with the 4" hole you might also expeiment with putting some screen on both sides and stuffing it with insulation to make an AP vent, with the purpose not so much to affect the response although it will but to continue to attenuate the back wave into the door metal. This resonance is the main reason i build enclosures. Anywhere near .37 ft3 seems like plenty that' as big as you're going to get with a door box. I am running Satori 9.5" woofers in a .32 ft3 enclosure and loving it. I did put an AP vent in there but I measure with it sealed and it wasn't a night and day difference.

    If you're really motivated, put the speaker on a big open baffle and measure it close field as well, then compare that to the measurment from the open door test. Try and determine how much of your response is the box vs the car vs the speaker.

  10. Back To Top    #20

    Re: Tuning midbass drivers...the struggle continues

    Quote Originally Posted by preston View Post
    I guess that midbass plot doesn't look all that bad to me. Are you primarily concerned with the lower end rolloff ? Its not like its that steep ? Or you could shelf filter the upper end and just play it. I admit I woudl expect there to be a little more bass given the expected acoustical loading. If it was a too small enclosure issue then I would expect a big high q frequency bump before the rolloff. Maybe that's as good as it gets for those drivers ? Another experiment, open your door all the way and put the mike close to the speaker and see what that response looks like.

    I am a little intrigued by this post because I'm a huge believer in door enclosures so I am inclined to defend them. If you stick with the 4" hole you might also expeiment with putting some screen on both sides and stuffing it with insulation to make an AP vent, with the purpose not so much to affect the response although it will but to continue to attenuate the back wave into the door metal. This resonance is the main reason i build enclosures. Anywhere near .37 ft3 seems like plenty that' as big as you're going to get with a door box. I am running Satori 9.5" woofers in a .32 ft3 enclosure and loving it. I did put an AP vent in there but I measure with it sealed and it wasn't a night and day difference.

    If you're really motivated, put the speaker on a big open baffle and measure it close field as well, then compare that to the measurment from the open door test. Try and determine how much of your response is the box vs the car vs the speaker.
    Thanks for the reply! Honestly, I'm not sure what I'm concerned with. I don't have much experience measuring. I watch a lot of YouTube videos and it seems like when I see people measure midbass drivers the response is a lot more linear than what I measure. I wasn't expecting to see such a lower end roll off nor was I expecting to see all those peaks and dips all across the pass band.

    I was hoping to just do some minor EQ work but I dont even really know where to start with the right driver measuring like that.

    I'm planning on hooking the battery charger up to the car tomorrow and spending a good chunk of the day experimenting.

    I really don't want to give up on my door enclosures. I didn't really want to vent them. Eric Steven's recommended the vent when I ran the MB8's.

    Either way, I'll have more information tomorrow. Who knows maybe I just need to get to work on the EQ and everything will turn out fine?

    Sent from my SM-G955U1 using Tapatalk
    Last edited by JerryGash; 12-18-2020 at 08:43 PM.

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