Rear Speaker Suggestions Please

Discussion in 'Car Audio, Electronics & Security' started by Greg73Z28, Dec 19, 2012.

  1. Aceshigh

    Aceshigh Veteran Member Lifetime Gold Member

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    The answer depends on the speakers you choose.

    But for the most part I agree with Z28zz383.
     
  2. mjoc

    mjoc Veteran Member

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    THe 200 watts on the head unit is not as good a seperate amp that produces 200 watts.

    Michael
     
  3. AJ_72

    AJ_72 Veteran Member

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    There is no head unit that makes 200 watts.

    The best I've seen a head unit make is 22 watts RMS x 4 channels (That's what Pioneer claims), and even that's pushing it. Like the speakers ratings I mentioned earlier, that's at a very narrow frequency range, too. Usually 50Hz to 12kHz is the range tested for head units.

    If anyone plans on using a subwoofer/amp combo and doesn't want to fork over the extra dough for another amp for the regular speakers, find a head unit with a high pass filter for the other speakers. It's much easier for the full range speakers to play "louder" when they don't have to recreate the bass below ~80Hz to 100Hz or lower. It's because they'll be able to concentrate all the cone area to a more narrow frequency range.

    "Bass Blockers" work, too, but they're not as effective. They often only have a 6dB/octave slope which does help, but it usually requires them to be selected an octave higher than the LPF for the sub in order to achieve a full 12dB slope at the same frequency cut off point. Basically, bass blockers are a first order filter (6dB/octave).

    I.E., if the LPF on the bass amp is set for 80Hz, the bass blockers chosen should be 160Hz, or close to that in order to keep the cut off frequencies from interfering with each other.

    This graph should give you a good example of what the differences are.

    Cyan = 6dB/octave
    Red = 12dB/octave
    Green = 18dB/octave
    Violet = 24dB/octave

    [​IMG]

    Picture compliments of www.bcae1.com
     
    Last edited: Dec 24, 2012
  4. Aceshigh

    Aceshigh Veteran Member Lifetime Gold Member

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    Many car decks for years have advertised 50W x 4 on the front of the deck

    Peak power was his point, I knew what he meant.
    It' not RMS.....obviously.
     
  5. AJ_72

    AJ_72 Veteran Member

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    I was going to edit my original post, but since you were so quick on the trigger... ;)

    Here's an owner's manual of a new Pioneer CD Receiver. On page 33 it states
    http://www.pioneerelectronics.com/StaticFiles/Manuals/Car/DEH-X8500BH_OwnersManual100212.pdf

    I was wrong. 50Hz to 15,000Hz not 50Hz to 12,000Hz. (Missed it by 3,000Hz).

    Anyway, that's basically no sub bass figured in (bass below 60Hz http://en.wikipedia.org/wiki/Sub-bass ) and while 15,000 to 17,000 Hz is pretty close to 20,000Hz, it's not quite as high as most speakers are rated to play (which is 20,000Hz).

    The worst part, 5% THD.
    That's horrible. Anything below 1% is considered inaudible by the human ear. Anything above, is audible. So why would they rate them at 4% higher than the audible breaking point? If amps were rated that way for "Continuous Power" there would be many unhappy people with a lot of bloody ears. :p

    That is why an amplifier rated at 22 watts x 4 channels sounds so much better. The RMS of a CEA-Compliant amplifier is at 1% THD and from 20Hz to 20kHz. While that may not seem like a big difference, it is.

    BTW, peak wattage is equivalent to Peak HP. It's only good for bench racing.
     
  6. Greg73Z28

    Greg73Z28 Veteran Member Lifetime Gold Member

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    Been away for a while getting work done on the car and thought I would update real quick. Thanks for all the input and discussion on this. I researched all the equipment that was recommended here and landed on the JBL GTO 938, mainly because of the mounting depth. I mounted them under the deck and placed the seperate ring that comes with them on top of the deck as a spacer between the factory grills and the mid/tweeter. A little tedious to install them that way but worked very well. Once I had them installed, I trial fitted the full sized spare in the trunk. It did fit, but rested against the passenger side speaker. I didn't like that, so instead of ordering a new amp that also rested on the tire, I changed the spare from a 235/60/15to a 205/60/15. That gave me just enough clearance for everything, and let's face it, the bumper jack and spare won't be used anyway. I replaced the head unit with a JVC that I can plug my ipod in to and saved a little coin in the end. Again, thanks for all the feedback on this. Sounds strong and clean. Here's a couple of shots I took to show the finished installation.

    Greg

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  7. Z28zz383

    Z28zz383 Veteran Member

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    Very clean install job. I bet that it rocks.....
     
  8. Aceshigh

    Aceshigh Veteran Member Lifetime Gold Member

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    ^ Unfortunately that Amp should not be mounted upside down.

    The heatsink is now under neath it and heat rises, which essentially makes it useless.
    The Amp gets hot, the heat instead of being pulled AWAY from the component boards
    will get soaked into it more, and can cause premature failure depending on how hard
    you drive the amp.

    It needs enough space above the amp to dissipate the heat also,
    since there's no moving air in the trunk........

    Just something to consider. :)
     
    Last edited: Jan 30, 2013
  9. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    I don't know how much of a true heat sink those are vs machined-in fins to look cool. The profile of a functional heat sink would be much thinner and taller to get more surface area. And class D automotive (switching type) amplifiers do not get hot like a class A/B does
     
  10. Greg73Z28

    Greg73Z28 Veteran Member Lifetime Gold Member

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    I worried about possible heat issues when I installed it originally, especially since I only drive the car in the summer (July and August in Joplin, it's not uncommon for triple digits). That added with the stock style muffler which mounts basically right below the amp on the bottom side of the trunk pan, I thought might give me troubles. Since hiding the system for a stock appearance was more important to me, I decided to go ahead and try it out there. The car was on the road from 2005 until the tornado took it out of commission in May of 2011. I don't drive the amp really hard, but I do crank it up some. I have had no heat issues so far. It is a realatively inexpensive amp, so if it goes, it goes. I still like the fact that the only way you know it's there is stand on your head in the trunk.

    Good observations for everyone to consider.

    Greg
     

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