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lithium

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Everything posted by lithium

  1. lithium

    Buick Century - active 3way + sub w/ nexus 7

    anyone know if running 1 rca input to a bridged 2 channel amp causing issues? should I use a splitter for any reason?
  2. lithium

    Buick Century - active 3way + sub w/ nexus 7

    So the issue with the midbass is pretty much solved. see this thread: I'm planning to start the A pillar pods this weekend. But first I made a small upgrade to the amps. Polk must be clearing old stock because you can grab the PAD2000.2's for $50 each (these are the same as the PPI 600.2). Great $/watt. I'm running one to each midbass. These replaced some very old Kicker 250.2's I bought 10 years ago. I was planning to grab a second nvx 4 channel to clean up the install a bit but this was such a great deal. I considered grabbing another to replace the subwoofer amp. https://smile.amazon.com/gp/product/B07HNRLCXC/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 some before and after pics. apologize for the wiring disaster.
  3. So I decided to post this outside my build log to see if anyone might have any ideas to help me solve this issue. Equipment: SLS 8inch Midbass Drivers running 60hz - around 200 i think. Mounted in the doors w/ a pretty solid treatment of SDS MLV, CCF, and CLD. Shitty GM doors aside, its a pretty solid installation. kicker 250.2 bridge to each side Description of problem: Midbass from left side is quieter by rough 1/2 to the ear w/ an 80Hz sine wave tone (measures around 8dB lower IIRC). I don't remember there being a huge difference between left and right previously, though I didn't really touch the stereo for over a year. My understanding of interaural time difference suggests that I could have overlooked this issue after setting my TA correctly. Stuff I've Tried: The only thing I've done recently with respect to the installation of the drivers was rebuilding the left door baffle after the MDF was exposed to water. I used 3/4 in cutting boards to build the replacement to the exact same shape. Maybe I didn't build a robust replacement but it seems to be fine when I feel for vibration and so forth (feel solid when speakers are playing). More CLD in the left door. I had a resonance issue in the door at 75hz so I went after it. Did not improve output. swapped drivers around to rule out issues with amps, speakers, difference between doors, etc. measured speaker voltage to rule out amps Ideas acoustic mode maybe I can build a small enclosure that I can move around the foot well to test this out? I suck at building speaker baffles out of cutting boards (I didn't find a great glue so I used machine screws) fuck IB door speaker, build door enclosure or IB kickpanels Take some nearfield measurement of the midbass to see what they're doing. Probably do these doors open and use a sweep I'll take some measurement later and post them.
  4. lithium

    Where did my midbass go?

    I figured that at the frequencies I was concerned with it would be fine if I wasn't sitting in the driver seat. I know from work that head position can have a huge impact on operator measurements. We have a 6'4" coworker and any operator measurements we get with him are a dB or two louder overall compared to someone who's average height.
  5. lithium

    Where did my midbass go?

    Thanks for this. I was messing around with the tweeter and mid range xover point and started way to high initially. The mark audio drives are pretty decent up high but a tweeter can do a bit better it seems. I just roughed things in for now and will do a full tune after building the A pillar enclosures.
  6. lithium

    Where did my midbass go?

    Ok, new measurement time. These are white noise, 65536-point spectrum using Rectangular window, and around 60 averages per measurement. It settled in about 20-30 averages but I let it run longer. 4 pink - Left midbass, 5 blue - right midbass same w/ 1/12 smoothing I have a decent amount of amplifier headroom so I tried some pulling down the peaks at 115 hz and 180 hz on the left driver to flatten the response. I also messed around with the gain to level match the right driver. I need some more seat time to see if this sounds ok to the ear. Pink is no EQ, Blue is after EQ and bumping up the level. 1/12 smoothing Here is the measured comparison between the left and right after some EQ. I took this so I can do some listen later and see if the changes worked as intended. With such aggressive EQ on the Left Midbass it looks like the effective Xover points are different between left in right. Maybe I will not be able to hear a difference or perhaps I'll need to change the xover to better restrict the low and high frequency content played through the driver. blue is left after eq, green is right after eq - 1/12 smoothing. Additional level matching later by ear. I think that this addresses the issue unless I'm overlooking something like not having enough amplifier headroom. There's nothing I can really do about speaker placement. I thought it would be fun to do a kick panel IB midbass install but not on this car. The more I listen to the midbass the less happy I am with their current performance. The doors are just not handling the 8s as well as I would like. After I finish the A pillars I might attempt some door enclosures. I think it would cool to make some door enclosure that are iso mounted on the door frame. I think that would eliminate most of the buzz, squeak, rattle. I'm not sure if 20 year old door hinges will handle more weight but at least I would have an excuse to buy a new car if the fucking doors fall off.
  7. lithium

    Where did my midbass go?

    Thanks for the clarification. I should have known better at the time. I'm going to repeat the measurements today. I want to see how severe the mode is.
  8. lithium

    Where did my midbass go?

    gotcha. I'll repeat the measurements with significantly more averages. Would you recommend changing any other settings or measurement signal?
  9. lithium

    Where did my midbass go?

    I've been doing some reading. If this is just a cabin mode there is little I can do to fix it. Some solutions like boosting 75hz and 150hz with eq have some obvious drawbacks. Another idea would be to xover the midbass/sub at 80hz but that defeats the purpose of running large midbass drivers. I'm thinking about building a small enclosure for a smaller woofer to try out other locations for midbass in the car, like kick panels. If a kick panel location doesn't excite the same mode then I could move the 8s there. I've seen people vent kick panels thru the tire well.
  10. lithium

    Where did my midbass go?

    That's a good point. I think I just rolled with the defaults in REW. Probably should have spent some time thinking about how to take good measurements with REW before hand. I did have fairly good agreement with repeated measurement. Edit: After some reading I think I should have performed this test with some different settings. If the current data looks questionable I fine with repeating the test later. Sample rate is 48kHz so I have 6hz resolution. Orange is full range with all left side speakers and sub enabled. Green, blue, and purple are just the LT mid bass driver. Blue and Purple are taken at a higher signal level obviously.
  11. lithium

    Where did my midbass go?

    15 dB of attenuation at 75 hz with a pretty narrow Q. Hopefully its not my HVAC acting as a resonator. I guess I can remove my dash trim and block all the vents.
  12. lithium

    Where did my midbass go?

    Oh man, I got some data. I'll try not to make a giant post here. So at this point I know the amps and drivers are fine. I matched the amp output voltage and disabled EQ. Lets start with some 1/12th octave RTA pink noise measurements. Mic at driver head position and was pointing straight forward (dayton ecc6). Just playing the individual drivers with xover at 50hz and 175hz (4th order i think) everything else is disabled. 5 - teal is left driver, 6 -gold is right driver. Have some pretty big nulls at 75 and 150hz when playing the left midbass. No idea what the 35hz peak is, cabin mode or something. When I measured with the sub ON it doesn't show up. [I reviewed some backround measurements, this is noise from the car running at idle] Near field measurements. I believe the settings I used were 30 Hz to 200 Hz over 5 seconds. I think we can ignore the level difference, I might have changed the output level to avoid clipping the microphone. I didn't take time to measure out the distance or anything. Just got the microphone a few inches from the cone and measured. pink - 9 is left, blue - 10 is right. This measurement was taken with the doors open as well. I repeated the near field measurements with the doors closed. I thought that the latched door might constrain the doors differently, green 12 is right, dark blue 13 is left. Im not sure what to make of this. Maybe I should have shortened the sweep length.. I any case, I think we can see that the midbass drivers are performing fine. Next I moved the mic around the cabin a bit and measured some additional 1/12th octave rta pink noise responses. Only left midbass is playing. Dark blue/green - 15 is measured 2 ft forward of the driver (just above the steering wheel almost). Gold - 16 is measured at the front passenger head. Green - 17 measured between front seat at head level. Purple - 18 Driver position baseline measurement. plots with 1/12 oct smoothing. Easier to read IMO So I'm starting to get the idea that this is some kind of cabin mode or some structure in the cabin is creating this null. Perhaps something in/under the dash. Here is one more plot that might demonstrate this the most. These are all measurements with only the left driver playing. purple - 18 measured at driver head. Red - 21 measured at driver head and right door is open. Green - 22 measured at driver head with all doors closed and Left driver window rolled down. I think its very interesting that null at 75 hz is complete missing with the Rt door open. Rolling down the driver window didn't help too much but I think the window glass is very close to the rear of the driver so perhaps that is not helping and this is a bad measurement. Going forward, I think I will try filling some cavities with some denim insulation material I have lying around. Open to any suggestions...
  13. lithium

    Where did my midbass go?

    Just checked the voltage at the amps and at the driver, measured the same. So amps are good, drivers are good, so now its probably installation issues...
  14. lithium

    Where did my midbass go?

    I'm just comparing the midbass drivers by themselves.
  15. lithium

    Where did my midbass go?

    Measurements where with a dayton emm6 and taken at the driver's head position (no one sitting in the seat), swept the mic around and averaged. I was using pink noise for an RTA measurement. I'll get some measurements today if the weather cooperates. I'll also disconnect the drivers and measure output at the amps(AC voltage). They're pretty old refurb kicker kx250.2 so it not impossible that one is on the way out. I've ruled out the drivers at this point (surprised these guy are still working after 10+ years in a car door).
  16. lithium

    Buick Century - active 3way + sub w/ nexus 7

    Hey guys, small update. I've been spending some time tuning the car and its going pretty well. I think the 4s are going to work great. In their current enclosure they can reach low enough to meet up with the midbass which was the whole goal of this build up till now. I've been doing some of tuning using REW and letting the AutoEQ generate corrections to a house curve that I've set up (I picked a popular one and plan to try some other out). The autoeq seems to work great at doing a first pass of everything before fine tuning by ear. I'm planning to start the A pillar build soon but first I need to figure out another issue that I'm having. I think I'll post the issue outside the build log so folks will see it.
  17. lithium

    What the tweeter. Try #2

    If you're planning to drop the Xover why are you buying car audio components to begin with?
  18. lithium

    Can someone review my box design

    Seems fine assume these calculators are doing everything correctly. I'd consider a double baffle for the top. Designing and building enclosures should involve some trial and error so worse case you're out a sheet or two of mdf. Test the box in the vehicle before you do all the finishing touches (carpet or paint).
  19. lithium

    Welcome to the IHoP v.2

    I haven't followed any car audio stuff in quite a while. Anyone have the scoop on why Don shutdown SDS? Not enough business or just wanted out? I'm surprised he didn't sell it..
  20. lithium

    Buick Century - active 3way + sub w/ nexus 7

    everything is active, which is preferable since the left and right are so different.
  21. lithium

    Buick Century - active 3way + sub w/ nexus 7

    yeah you're right. The mounts aren't strong enough to lift the right speaker pod off the dash so this is how it will work for now. I can rotate the tweeter such that it's level with the left. Fortunately, the human ear is shit at localizing sound vertically.
  22. lithium

    Buick Century - active 3way + sub w/ nexus 7

    i was actually thinking about that. I'll have to look around the interwebs for something.
  23. lithium

    Buick Century - active 3way + sub w/ nexus 7

    Since i'm rebuilding my midbass door baffles I wouldn't mind some suggestions on what drivers might be good options to swap into the doors (for mounting clearances). As I said before I'm trying to address the gab between midrange and midbass 150-300hz area.
  24. lithium

    Buick Century - active 3way + sub w/ nexus 7

    updated pics. I'd like to get the left midrange a bit more to the left as it sounds very much from in front of me rather than the side.
  25. lithium

    Buick Century - active 3way + sub w/ nexus 7

    A few other notes. I sealed the wire hole in the back of the MR pod with duct seal (love this stuff) and I add some poly fill to them as well
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