Car audio - subwoofer's lowest frequencies too loud?

Discussion in 'Audio Hardware' started by supermd, Aug 29, 2019.

  1. carrick doone

    carrick doone Whhhuuuutttt????

    Location:
    Vancouver, Canada
    Ok, good. Now you are finding out what your system is physically doing.

    I'm going to give it more of a think but I'm interested in your sub now (Put a pin in the out of phase / in phase thing for now). I will defer to someone here who is a pro installer but I have a guess as to the problem.

    If the sub gets sound when both channels are in action but not when one is off that COULD, and I say could, mean it is receiving a signal from only the positive or negative wires of your amp/headunit and not a positive AND negative wire. You don't indicate if you have a centre channel or if your amp provides for one adn I'm not going to go search for your amp manual. The centre channel needs information from the left and right input to operate. Take one side away and it has no reason to give centre information. What I need to understand is why the sub would go out when the signal is out of phase.

    The next part is a huge guess - I am only skilled at installing the stereos I have done over the last 30 some years and I can't play with yours to find out where wiring is going. Ideally a sub uses summed mono information from the negative and positive signal coming from either the head unit or amp. It will use either left OR right or both channels to push signal the sub. That way you could have a bass playing in the left channel and still hear it from the sub. The amp should have a dedicated set of connections labelled SUB but it doesn't have to. The installer could have wired the sub in as part of the front speaker set. The guess is that it is possible you have the wires coming from a CENTER connection to your sub. The other guess is that the sub is miswired with signals from only a negative or positive set of connections. Both of those may cause the sub to go out when one side is playing.

    You don't mention if this is happening only with the fronts. I will presume it is. If you haven't done yet can you check to see if the same thing happens with just the rears?

    So here's the next step from my humble position. If you don't want to take it to the same or a different installer (I would imagine and hope the same installer would recheck their work no charge) or have a friend who is good at this stuff (or fly me down :)) I would suggest taking your amp manual and walk through the wiring positions on the actual amp. You need to know your sub is being powered by the right connections. And this assumes the amp is operating properly. You have 3 weeks into tuning this beast and you seem dedicated to getting a good sound. Take your time and go through this step and you will at least know more.

    The good part is that your initial guess is right - there is something going on with the wiring that causes the audio problem you have.

    Does anyone else have thoughts? Am I completely off base with this path? As I said I am not a pro so I may be missing something about car amps.
     
  2. avanti1960

    avanti1960 Forum Resident

    Location:
    Chicago metro, USA
    forget the sub for now and focus on getting good bass from your front main speakers. once you have that sorted get back to us.
     
  3. head_unit

    head_unit Forum Resident

    Location:
    Los Angeles CA USA
    Yeah, a lot of funny things going on. I spent many years as an automotive sound engineer, but it's too late at night so I can't quite wrap my head around your results. Clearly though you need to isolate to fewer things going on at once, that is basic scientific practice. Maybe like:
    - DISCONNECT the sub.
    - Get some MONO tracks with bass-early Elvis, Buddy Holly, Bill Haley and the Comets, Stones, Beatles (check all the tracks in headphones to be sure they are really mono). Also some kind of noise tracks...mono noise...ideally filtered to like below 500 Hz only for less distraction. (Anyone know of such?)

    1) Fader all the way front-is there bass? Move balance L/R: does each side have bass? How about when centered, there should be MORE bass. If not, one side's polarity* is wrong.
    2) Fader all the way back-is there bass? Move balance L/R: does each side have bass? How about when centered, there should be MORE bass. If not, one side's polarity is wrong.
    3) Fader centered-there should be even MORE MORE bass, presuming the polarities are OK. If not, the whole front or rear is miswired to the wrong polarity.

    Now the sub. Yes, the sub vs fader/balance can be weird depending how the sub is wired. What is going into the sub amp? RCA or speaker level? Sometimes as @carrick doone noted you get convenient but odd wirings tapping off some speaker wires, but no actual ground, giving odd results.

    Assuming 1-3 came out OK or are fixed, now you can check the phase* between the sub etc. This is not as simple as polarity, due to phase shifts of the various drivers.
    4) Fader all the way front, no sub. Listen. Shut off, connect the sub, there should be MORE bass. If not there is a phase problem. Remedies are changing polarity and/or fiddling with the crossover points...interdependent so tricky, sorry to say. From long experience, with your system I cannot imagine why any of the crossover points should be above 100 Hz. Note that highpass and lowpass often can end up spread apart to different frequencies.
    5) Repeat with fader all the way back.

    *to make some crude definitions, polarity is whether the cone moves in or out with a positive DC voltage applied. Phase is a byproduct of time response, kinda sorta like polarity but at higher frequencies and changing with frequency, not fixed like polarity which is + or -
     
    carrick doone likes this.
  4. supermd

    supermd Forum Resident Thread Starter

    Location:
    Campbell, CA
    Since I didn't use the sub at all during this test, I'll have to get around to your sub advice at a later time. I have been too busy. Thanks for all your help so far!!

    I did some tests today with a 160hz test tone from my iPod and an app on my Android phone called "Sound Analyzer App." The sub's amp was turned all the way down for this test. My speakers' crossover point is 80hz.

    When centered and fronts active only, 160hz sounds like it is mostly coming from the front left (FL). It sounds more centered at 20% FR (which is natural since I am closer to the left side in the driver's seat?).

    The rear has a lot of sound space fluctuation when going RR to RL, with a quiet pocket at 20% RL. In the driver's seat, rear bass is lowest at center.

    When I move my head to the center between the two front seats, bass isn't much louder, if at all, when going from FL to FR at 160hz.

    Using the app, I got some dB readings holding the phone at my face (Driver) and on the center armrest. I used C-Weighting and Slow weighting. Here are some numbers:

    Driver
    FL - 60dbc
    FC - 63dbc
    FR - 60dbc

    RL - 56dbc
    RC - 46dbc
    RR - 57dbc

    Middle/center of fade/balance - 62dbc

    Center
    FL - 55dbc
    FC - 60dbc
    FR - 60dbc

    RL - 49dbc
    RC - 57dbc
    RR - 53dbc

    Middle/center of fade/balance - 64dbc

    So... thoughts?
     
  5. supermd

    supermd Forum Resident Thread Starter

    Location:
    Campbell, CA
    Also, I did a phase test again (sub off), this time putting my head in the center, facing forward. While the IN PHASE section doesn't seem to be super focused, the OUT OF PHASE, by contrast, sounds like it's coming from off to the sides and funky. It was this way for the front and rear.
     
  6. avanti1960

    avanti1960 Forum Resident

    Location:
    Chicago metro, USA
    a 160Hz tone is not going to be of much help. at this point just run your front mid and tweeters for a few weeks by themselves. you should be able to get decent sound without the rears and sub.
    make sure the high pass filter on your amp is off for the channel feeding the front woofers. just run them wide open for a while.
    switch the tweeter to its lowest level on the speaker crossover to "0" db. By the way your crossover woofer to tweeter is a high 4000 Hz.
    run that for now and see if you can get decent bass and become accustomed to the sound. also adjust the balance by ear, a single frequency test tone is worthless.
     
    supermd likes this.
  7. head_unit

    head_unit Forum Resident

    Location:
    Los Angeles CA USA
    That likely means things are partly in phase, but not 100%. What were the conditions for this test?

    I partly agree with @avanti1960; single tones in a car can have weird effects. Their best use is using quite low frequency tones to see if the front L/R are in phase with each other (fader left, then center should be louder, then right. Sit in the middle somehow, yeah, it's uncomfortable). Not 20 Hz, but as low as you can but still get decent audible output without the volume control jacked way up. You can repeat to check it rear L/R are in phase with each other. Then again balance centered fade front --> both should get louder --> rear.
     
    supermd likes this.
  8. carrick doone

    carrick doone Whhhuuuutttt????

    Location:
    Vancouver, Canada
    It reads like you have some good advice going on here supermd so I will read and learn.
     
  9. supermd

    supermd Forum Resident Thread Starter

    Location:
    Campbell, CA
    My test conditions were me sitting in my car with a test tone on repeat, using the app mentioned above to measure volume in two different positions. I can see how a single test tone can be pointless, but I was using it to see if the frequency range I say is lacking truly is lacking, and also to measure how the sound waves bounce around. Which "quite low frequency tones" do you recommend? 45hz? I have a range.

    I'm taking your advice with my light fiddling throughout the week and focusing way more on my main front speakers. I can hear lower tones when they are on full range frequency, but not in my "sweet spot." My current on-the-fly test setup is putting the hi-pass crossover to 60hz and the sub low-pass crossover to 80hz. Then, I have upped the bass on my head unit's EQ to try and get the bass frequencies higher on the front speakers in the ranges I want while allowing the sub to be monitored separately via the separate volume control. I'm still having problems...

    I have yet to do any major tweaking, such as messing with the tweeters. I have no idea how the audio place installed those, but I do currently think they are too loud. I have to turn the treble EQ to -9 (out of 10) to get it in a more manageable range, which I think makes the other highs suffer as a result.

    I have an idea that I'd like to run past y'all. I currently have an Lc6i running between my factory head unit and my amps. Could removing that help restore the frequencies I crave? I did not have a problem with the factory speakers/setup hitting the range I desire, but they did feel "congested" and "boxed in," in that there was a high they couldn't reach and a low they couldn't reach. It sounded limited in the extremes, which I thought was due to the speakers used and some kind of limiting done on the output to not damage their factory speakers. Could removing the Lc6i give me the frequencies I want, under the assumption that the old speakers were benefiting using EQ from the head unit specially formulated to sound good in my car, regardless of speaker used?

    To give you all an example, listen to the 1967 stereo mix of "When I'm 64." The bass should be loud with a nice, warm, solid thump. That "sound" is very low in my car.
     
    Last edited: Sep 11, 2019 at 12:26 PM
  10. avanti1960

    avanti1960 Forum Resident

    Location:
    Chicago metro, USA
    the Lc6i is a line converter- it should not affect frequency balance- unless it was wired strangely to make a quasi active system with separate channels for the front woofer and tweeter. if so, this would comtrol the level of the woofer and tweeter individually and you need to lower the tweeter / raise the woofer.
    there are so many things that could be the cause .
    can you get access to the kicker crossovers to set the tweeter level to zero db?
    do you know how your woofers were installed in the door? did they make a good seal to your inner door panel? if the back wave of the woofer can "see" the interior of your car all of the bass will cancel and you can crank the EQ all day long and still not get any bass.
    you should be able to get good bass from the front set of speakers on flat with no EQ.
    your system needs a thorough check of wiring, speaker installation and adjustments by someone who knows what they are doing
     
    Last edited: Sep 11, 2019 at 7:40 PM
    supermd and carrick doone like this.
  11. head_unit

    head_unit Forum Resident

    Location:
    Los Angeles CA USA
    That should be low enough is my feeling, assuming the speakers have decent output at that frequency. Good luck!
     
  12. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    You should be able to enjoy the music of the main speakers even without sub and crossover, especially when parked and not overcoming road noise. If the main speakers have poor bass and even a mid-bass suck-out, that needs to be addressed before you start fiddling with the sub.

    I have a feeling the most basic problem is that the speakers are just installed into the door sheet metal and stock location, with no provision for making a proper enclosure. Every other hole in the door panel becomes a leaking box where the out-of-phase unmanaged back wave of the speaker cancels out the front output.

    You need a proper baffle-board to mount the speakers and to block the rest of the door openings. Additionally, the outer door skin vibration can be managed with lots of dynamat, and fiberglas mat where it doesn't interfere with the window operation.

    The speakers don't have published Thiele-Small parameters, and saying they are "free-air" in the Kicker manual is just a cop-out. Your door is still an enclosure, and you need to tune the speakers so they operate well down to a 60-80Hz crossover (where subwoofer frequencies aren't locatable as coming from the back of your hot hatch.)

    [​IMG]
     
    supermd likes this.
  13. supermd

    supermd Forum Resident Thread Starter

    Location:
    Campbell, CA
    Thank you for the response. This baffle board you speak of... Is that all I really need to help my bass issue?

    Boom Mat 6-1/2" Speaker Baffles (Regular: 3" depth)

    What am I looking at in the photo above? Dynamat? These are foreign things to me haha.
     
  14. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    You link to some styrofoam speaker weather sealer thing - no. That is not a "baffle", in that it would barely attenuate the back wave of the speaker; that is a bastardization of the word.

    A baffle is the front panel board of a speaker, where the drivers are mounted. It separates the front output of the speaker from the back wave that would otherwise interfere and cancel out the bass output. We think of speakers mounted in a box, so the output of the back stays in the box, but the back of the speakers can also go into another room, into the trunk of a car, or an "open" baffle board can be very large, so waves would have to go all the way around the board to interfere.

    [​IMG]

    A normal car door is mostly holes, for servicing the motors and locks:
    [​IMG]

    The holes need to be sealed up, by screwing custom-cut MDF panels over them with sealant or foam behind, fiberglassing over them, or at a minimum, covering with several layers of asphalt-based noise-deadener.

    [​IMG]

    The speaker itself will benefit by having a firmer sealed mounting surface, an actual baffle board instead of the stock location, where it is merely screwed to steel or via plastic inserts..
    [​IMG]
     
    Last edited: Sep 12, 2019 at 4:22 AM

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