1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Should my system put out more db's?

Discussion in 'Car Audio / Security / Electronic Accessories' started by trappd-in-859, Nov 15, 2007.

  1. trappd-in-859

    trappd-in-859 New Member

    Messages:
    595
    Likes Received:
    0
    Joined:
    Jan 17, 2005
    Location:
    burlington, ky
    When I took my car to a local audio shop it read at 132db with the driver door opened slightly and half of the rear seat folded. The subs are firing toward the trunk and I have no sound deadening to speak of. Do you guys think the reading sould have been higher? My system specs are listed below.Car: '01 monte carlo Subs: 2 JL 13w1v2 Amp: JL 500/1 slash series v2 HU: Clarion (forget model# but it's an '06 $500 HU) Stock 6x9's in the doors and rear deck Stock alt 110A 0ga wiring stock battery If the reading I got was accurate, what would you suggest, besides changing subs and/or amp, to increse SPL to somewhere around 140db's? Only thing that I know of that would help would be to get a ported box.TIA for all replies
     
    Last edited: Nov 15, 2007
  2. trappd-in-859

    trappd-in-859 New Member

    Messages:
    595
    Likes Received:
    0
    Joined:
    Jan 17, 2005
    Location:
    burlington, ky
    Sorry if that is a little hard to read. Something is messed up with my computer or the reply box. For some reason I can't space out paragraphs.
     
  3. alEXej8

    alEXej8 New Member

    Messages:
    236
    Likes Received:
    2
    Joined:
    May 5, 2007
    Location:
    Hubbardston, MASS
    First off whats are the subs RMS, not MAX rating? Second what is the rms rating of the amp? also what are the subs ohm resistance? and how are the subs wired? all of these wil make a difference in Db ratings. Plus upgrade you from your stock speakers to a nice set of Aftermarket ones. the doors have 6.5" and the rear deck has 6x9's.
     
  4. trappd-in-859

    trappd-in-859 New Member

    Messages:
    595
    Likes Received:
    0
    Joined:
    Jan 17, 2005
    Location:
    burlington, ky
  5. norcalgsr

    norcalgsr Honda Master Technician

    Messages:
    1,168
    Likes Received:
    17
    Joined:
    Oct 10, 2007
    Location:
    NorCal
    The driver's door being open probably cost you a good amount of SPL..

    It also has a lot to do with where the mic was positioned in your car.
     
  6. trappd-in-859

    trappd-in-859 New Member

    Messages:
    595
    Likes Received:
    0
    Joined:
    Jan 17, 2005
    Location:
    burlington, ky
    I've actually heard that opening the door increases your decible level by like 2db's. I could be wrong though.

    Also, to make things clear, I'm not some SPL nut who will do anything for an extra db or two. I guess I'd be better classified as an SQL person. IMO my system sounds pretty good the way it is now, but I would like to be a little louder.

    Another question I have would be about my lights dimming while hitting a heavy bass note. I've recently replaced my old battery with a diehard platinum, but my lights still dim a little when the amp's at full power. I was thinking maybe add a battery in the trunk? Or do you think the only solution would be to get a high output alternator?
     
  7. norcalgsr

    norcalgsr Honda Master Technician

    Messages:
    1,168
    Likes Received:
    17
    Joined:
    Oct 10, 2007
    Location:
    NorCal
    I think it depends on the car.. so try both ways and see which works out better to be sure. In my old car I got better SPL by closing everything up, but it was an Integra hatch so that may have had something to do with it.

    Do you happen to know if you have the 4 ohm or 8 ohm subs, and how they are wired(parallel or series)? That will make a big difference on the output power of your amp depending on the ohm load it is seeing from your subs.

    As far as the lights dimming a second battery should definitely fix the problem. If you don't already have a capacitor around 1.5 farad or so I would add that first and see if it helps. The alternator would be the last step in the chain, and most likely isn't going to be needed for that setup.
     
  8. TommyTheCat

    TommyTheCat Gonzo Scientist

    Messages:
    1,248
    Likes Received:
    11
    Joined:
    Sep 29, 2002
    Location:
    Minneapolis, MN
    1) It is vehicle and install dependant whether or not sealing the car (or not) will gve you more or less db. So it could have helped you or hurt you.

    2) It doesn't matter what resistance that slash amp is seeing. If it's between 1-4ohm it'll put out close to the same 500W.

    3) My Accord handled ~1000W with the stock 90A alt. And you're using 1/0ga wire? Something isn't right with your grounds or the charging from the alt. This is a different story if you're talking about lights dimming after you've been sitting.

    4) I think you're getting around the potential for your equipment. The only way to get more out of what you have is to put it in a crx.

    So if you've got the space and the time/money - port those suckers. But dont get caught up in numbers - if you get a gain of more than 3db at your peak freq you're going to start killing the "SQ" of the system. If you do it right you'll only meter 2-3db higher (because these are peak-single frequency reading) but you'll have a lot more lower bass.

    (This post is quite simplified - take it as a guide, not as rule)
     
  9. trappd-in-859

    trappd-in-859 New Member

    Messages:
    595
    Likes Received:
    0
    Joined:
    Jan 17, 2005
    Location:
    burlington, ky
    Well, I went from a 325/1 rockford to the JL amp. I had no dimming issues with the rockford, but when I turn the bass knob to about 3/4 of the way on the JL, I get slight dimming. I was told that this JL amp only takes about 48amps at full tilt, so I should not have dimming lights if this is true. Wether the car is sitting in park or I'm driving, still has the same dimming problem.

    The only thing I can think of is checking the ground on the amp like you said. If that doesn't fix the problem I guess its time for a new alt.
     
  10. cheese9988

    cheese9988 Senior Member VIP

    Messages:
    1,989
    Likes Received:
    251
    Joined:
    Apr 25, 2003
    Location:
    Lowell, MA
    Most of the time, sealing the car as tight as humanly possible will increase the volume. As the sound will not be allowed to interact with the outside air. With sound you create compressions and retractions, you essensially pressurize the air. If opening the the windows creates more sound, why not put the speaker on the roof?

    Resistance makes a huge difference. When the voice coil in the sub is cold is where the resistance will be less. Although music is dynamic, and the actual power will change with frequency due to the fact that the voice coil in itself is an inductor and the speaker is a motor and both of these have thier own resonant frequencies. When the voice coil is cold the nominal resistance for dc is approximetely 4 ohms for most speakers. Like all metal, copper has a heat coeficient, the resistance of the copper will increase with temperature at a rate of ~0.00393 per deg C.

    So if the voicecoil heats to 200 deg C during use, the resistance will increase to 4.7074 ohms. So at 20 deg C the resistance is 4 ohms and the voltage output is 40Vrms, the wattage used by the coil would be 400W. But at 200 deg C the wattage used by the coil would be 340W.

    Adding or subtracting speakers will change the resistance as well, less resistance will = more power. But can the amp handle it? 40V output from the amp on a 1 ohm load = 1600watts but at a 4 ohm load = 400 watts. How is this the same? I hope you have spare fuses.

    To get more power from a higher load, you will have to increase the voltage. So you will have to turn the volume up on the deck, and at some point you will overdrive the amp into distortion which is bad for both the amp and the speaker.

    Also, there is efficiency. Volume will increase at a rate of 3dB ever time the power is doubled. Take a 1000W speaker with a 87dB efficiency (1W @ 1meter) and a 500W speaker with a 92dB efficiency (also 1W @ 1meter). So using a log2(500)*3+92 = ~119dB for the second speaker. log2(1000)*3+87 = 117dB. To get 3 more dB out of any situation requires you to double the power. I forget the exact number, but I believe you can gain an extra 6dB from just adding one speaker of equal power.

    To get the most amount of flux, you must have a large magenet as close to the coil as possible. If thin wire is used, you could save space by having little expansion due to heat, and increase the closeness of the magnet to the coil, although power handeling would be limited. Do the opposite with thicker wire to handel more power and you would have to wrap the wire many more times, increasing the gap around the voicecoil, decreasing the efficiency of the motor. Now you must use a larger magnet. Larger parts = an increase in mass. Then there is saturation, which I don't know as much about.

    Basically what I'm trying to say is, buy more speakers, not more power. One extra speaker will make the world of difference. A lower power amp with more lower power speakers and some time to shop around can yeild the same results without hurting your wallet.

    Next off, your lights dim in your car simply because of the alternator. The sensors adjust field windings inside of the alternator, and cannot adjust at the rate the audio does. So as the bass hits the voltage can go from 14.4 to 12 before they catch up. The field windings increase alternator life, if the alternator ran without these you could run the alternator at its fullest potential and it would burn out real quick or fry some belts from the excess torque it would need. If your really worried about it, get a capacitor.

    Excuse my grammer.
     
  11. TommyTheCat

    TommyTheCat Gonzo Scientist

    Messages:
    1,248
    Likes Received:
    11
    Joined:
    Sep 29, 2002
    Location:
    Minneapolis, MN
    I believe that when you open a window or door it creates a bandpass effect that can create or change the way pressure "builds up" in the cabin. This can change how the peak response of the system is by either increasing or descreasing it at the measurement position.

    The pressure inside a ported enclosure when driven at resonance(of the box) can have much more pressure on it than a sealed enclosure.

    Typically the dc resistance is 1/2-3/4 of the rated nominal impedance level. A 4ohm rated impedance could have a resistance of 3.2ohms while a 8ohm Z could be like 5.6ohm.

    The resonance situation you describe is wrong on both parts. Neither the inductance of the driver nor the motor structure form resonant circuits. The spring-mass system of the moving mass(cone, coil, etc.) and the suspension(spider, surround) provide the one resonance referred to as the Fs of the speaker. The inductance merely forms a low-pass filter that makes the driver "roll-off" on the top end. This is (hopefully) out of the region we wish to use our driver in.

    This is called "power compression". Resistance change is the big factor provided the speaker isn't moving near its' mechanical limits (when motor force drops and creates the dominant compression).

    I hope you aren't referring to my post about this. The JL amp has a regulated supply that provides a non-constant amount of rail voltage for the amp at different impedances. The power supply is rated at 500W and so the peak voltage/current levels are changed.

    True, by doubling cone area and power you will gain 6db (assuming proper summation of the waves).

    But sometimes high power is fun! Really the best bet is to survey how much volume(airspace) you can afford and then obtain a proper amount and size of woofers that will work. Then you just see how much you're willing to spend on power and decide if you need Pyle Blue Wave's or DD951X's.
     
  12. cheese9988

    cheese9988 Senior Member VIP

    Messages:
    1,989
    Likes Received:
    251
    Joined:
    Apr 25, 2003
    Location:
    Lowell, MA
    Your compressing the air within the car. Rapid air compression and expansion is how we hear. If you compress air within a pipe and then open the pipe, what happens to the pressure? The bandpass systems are completely inside the car and should have no contact with the outside air. Are there people at competitions opening their windows or are they plexiglassing them closed, why is it that the glass pops out?

    I would hope a high end brand would have those characteristics as it is impossible to get around these proporties, even when using rare metals. It would be nice to have each one individually tested and characterised as well.

    I may have written it wrong, but the speaker does have a resonant frequency as a result of the electrical inductance rolloff and the mechanical characteristics of the driver itself. Both of these combined will peak at some point which is what resonance is.

    Partially true. It may have a regulated power supply within the unit as alot of amps do. It will keep a constant voltage rail to the transistors as best as possible. However, you are really calibrating the amp yourself as clearly stated in the manual, and you can do the math yourself to confirm this. Wattage = Voltage^2/Resistance

    The manual has you set the input to the amp to 3/4 volume, which should be around max to avoid distortion. Then it says for you to adjust the output level using a dmm. At 4 ohms it wants you to set the amp for a "target" ac voltage of 44.7V. 44.7^2/4 =499.5 Watts. At 1.5 ohms 27.4V. Using the same equation it equals 500.5 Watts. The one watt difference is irralavant as the typical handheld dmm is not that accurate. So really, you are the one adjusting the unit. The output voltage will vary with the input signal as normal. It's just another sales gimmick. It would be nice for other manufactures to put that in their manuals, as most people do not know how to set up the amps for a max signal. You can do this with ANY amp that has a regulated power supply, and actually as long as the input signal never varies, any amp with a gain on the side of it.
     
  13. TommyTheCat

    TommyTheCat Gonzo Scientist

    Messages:
    1,248
    Likes Received:
    11
    Joined:
    Sep 29, 2002
    Location:
    Minneapolis, MN
    When you would open the pipe you would get a volume velocity which would create a pressure gradient away from the opening of the pipe. But I dont understand what that has to do with anything.

    As far as the bandpass comment goes - what im referring to is not a bandpass enclosure inside a vehicle. Im talking about the effect of placing your subwoofer enclosure inside a sealed cabin (which is an enclosure) and then creating a vent or port by opening a door or window. At low enough frequencies it should be clear that the cabin volume can certainly be thought of as enclosure. A big, leaky enclosure of course.

    And most competition organizations have rules that the vehicle must be sealed just because it allows for an easier comparison of systems/designs. If they had to have windows open many competitors would still use inches of plexiglass in order to keep their vehicles as rigid as possible.

    It takes a bit of consideration to believe that its not always best to just seal everything up because it "creates" or "holds the most pressure".


    I dont really understand what you mean. What "characteristics" do you find desirable?



    Ah, I see what you're saying. But as JL claims - they are using an "impedance optimization circuit" in order to vary the amount of maximum rail voltage. The gain setting instructions look to only serve as a guide to limit distortion.

    This would assume that for X amount of input voltage (which would be small) if you connected a 4ohm load and could get a (lets say) 20V maximum undistorted output (maximum gain setting) that with a 1.5ohm load you would only get 12V (at maximum gain setting). But this would have to be seen to be believed - as I have not personally used one (but most everyone seems to agree it does happen).

    Considering the price and JL's reputation - it might be more than just marketing.
     
  14. TommyTheCat

    TommyTheCat Gonzo Scientist

    Messages:
    1,248
    Likes Received:
    11
    Joined:
    Sep 29, 2002
    Location:
    Minneapolis, MN
    This is simply not true!

    The resonance of a loudspeaker is just as I described it before. It is the mechanical interaction of the moving mass and the suspension "spring". The inductance of the coil does not affect the resonance at all - it simply adds inductance to the impedance and creates a first order low-pass filter.
     
  15. TommyTheCat

    TommyTheCat Gonzo Scientist

    Messages:
    1,248
    Likes Received:
    11
    Joined:
    Sep 29, 2002
    Location:
    Minneapolis, MN
    Not a bad idea:
    [​IMG]
     
  16. norcalgsr

    norcalgsr Honda Master Technician

    Messages:
    1,168
    Likes Received:
    17
    Joined:
    Oct 10, 2007
    Location:
    NorCal
    Hey it's Alma Gates & "The Beast" :D

    That thing is fuckin crazy! Sit inside it and die lol
     
  17. 88blacksi

    88blacksi Grandpa

    Messages:
    220
    Likes Received:
    0
    Joined:
    Oct 16, 2007

    HAH HAH HAH HAH HAH
    That is some funny shet.
     
  18. norcalgsr

    norcalgsr Honda Master Technician

    Messages:
    1,168
    Likes Received:
    17
    Joined:
    Oct 10, 2007
    Location:
    NorCal
    Why is that funny?
     
Verification:
Draft saved Draft deleted

Share This Page