Firing the Subs

Discussion in 'Car and Home Audio' started by ForistellFord, Nov 5, 2013.

  1. ForistellFord

    ForistellFord In Maximum Overdrive

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    So, the folks with sub boxes in your cheros... Where to do you fall in the old argument- having the subs fire up or fire down, or front or back? What sounds best in these beasts?
     
  2. TestDummy

    TestDummy In Maximum Overdrive SILVER MEMBER

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    I would guess firing back, because of the small cab. That worked best in my F150, back in the day.
     
  3. burninbush

    burninbush In Maximum Overdrive

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    If it's really only handling low frequencies then which way it points matters not at all. Depends on the crossover design. By the time you get up to ~70hz or so then you begin to be able to discern the direction to the source.

    The driver in the speaker box won't care which way it's pointed. A purist might argue for the traditional mounting orientation of a cone speaker, i.e., cone moving on a horizontal axis, less distortion due to gravity effects.

    Try it every which way you can -- pick one.

    One sub fact that bears mention: you can hear ALL of the distortion products emanating from a bass driver. Unlike for treble frequencies (3rd harmonic of a 5khz tone comes in at 15khz, which most adults can't hear.) So think of this when you go to buy that cheapo speaker and amp; 3rd, 5th, 7th harmonics of a 50hz tone fall right in the range of where humans hear the best. Subs really need to be the most hi-fi pieces in your system.

    p.s. -- drivers in my home subs point down
     
  4. Rancherous

    Rancherous Administrator Staff Member

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    For sound quality use a 10 or 12 in a sealed box stuffed with polyfill you get from the craft section in Wal Mart, in the standard configuration, magnet inside the box. Check the manufacturer specs of airspace needed for optimum frequency response. For example a 12 inch J/L Audio 12W3 in a 1 cu/ft sealed box. Make sure the box is air tight by using silicon on the edges and inputs, I find a lot of pre fab boxes do not do a good job of siliconing the edges well. Sonic Electronix is about the cheapest place for boxes and stereo equipment. Stay away from Sony and other cheap brands.
     
  5. ForistellFord

    ForistellFord In Maximum Overdrive

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    How about mounting them inverse from one another, and reversing the polarity on one?
     
  6. ribald1

    ribald1 In Maximum Overdrive PLATINUM MEMBER

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    Sometimes that creates a clearer bass sound, but you get a weaker output as a trade off.
     
  7. ForistellFord

    ForistellFord In Maximum Overdrive

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    So, it basically all comes down to 'test out different options and choose which one you personally like best'. No definitive correct answer.
     
  8. ribald1

    ribald1 In Maximum Overdrive PLATINUM MEMBER

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    Pretty much. There are just too many variables.
    If you buy high quality speakers and amps it will sound good just about no matter what you do, so the easy solution is to spend $1200-$2000 and be done with it.:D
     
  9. ForistellFord

    ForistellFord In Maximum Overdrive

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    I'm a cheap bastard so I'll do the trial and error. Not like Sparkomatic cheap, but Kenwood cheap.
     
  10. Rancherous

    Rancherous Administrator Staff Member

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    What vehicle is this going in?

    The box type is key here.
     
  11. ForistellFord

    ForistellFord In Maximum Overdrive

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    Big old Ford conversion van.
     
  12. Rancherous

    Rancherous Administrator Staff Member

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    How much room you want to dedicate to Subs? What equipment do you have?
     
  13. burninbush

    burninbush In Maximum Overdrive

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    No ... it's just a piston, regardless of how many drivers you have in the box. All cones should move in the same direction [out or in] at the same time. Virtually to make the volume of the box bigger or smaller depending on the current polarity of the signal.

    I use an AA cell and a helper watching the cone to ID the connection polarity.

    There is in fact a school of design thought about bass boxes that requires two identical drivers, on opposite sides of the box. This is a mitigation for that cone-suspension problem I mentioned up the thread. Supposedly makes less distortion than a box with a single cone. Speaker cone suspensions are not linear except for very small excursions. You would like the voice coil to see the same physical load resistance whether moving in or out, but that is rarely achieved.

    As an aside, some modern surround receivers these days come with a microphone which you will place during setup at the position of the listener's ears -- and it has an internal test routine to self-adjust all connected speakers. Pioneer claims it will at need electrically reverse the phase and set delay of all speakers such that an impulse sound from all speakers gets to the ear at the same instant. Also does a room equalization at the same time. Result sounds so good to me that I just bought a second box that does this for my upstairs system.
     
  14. Rancherous

    Rancherous Administrator Staff Member

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    A 9v battery is easier to do the polarity test both contact on top. You can also test to see if the speaker is blown that way as well.
     
  15. ForistellFord

    ForistellFord In Maximum Overdrive

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    I want to fire them down so I can have a good sized box in the rear yet still load groceries and miscellany on top of it when needed.

    Currently have a Kenwood KDC-155U head unit. Van has six 6.5" speakers scattered about but all are old and sound pretty crappy. Head unit has pre-amp out so I want to get an amp and a sub box (currently have neither). Main purpose will be for the kids watching movies on long trips or playing a video game. I want a good sound experience. Also want the usual good quality output for the stereo part as well, when I feel like introducing the younger generation to Moxy, Neil Young, Skynyrd, etc. Open to any and all suggestions.

    BB I don't need technology like that in Bubba (van) but when I upgrade the home theater, I will have more questions for you. And I guess Billy too because you're the two main audiophiles here I assume.
     
  16. burninbush

    burninbush In Maximum Overdrive

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    I suggest that you build your own sub box. Use high-density particle board and goodly amounts of Elmers white glue. Use sheetrock screws to hold the joints tight while it dries. Then mount the speaker (with a gasket) onto a hole cut into one side. Place some small feet in the corners to keep the cone from hitting the floor.

    Thicker particle board is much better than thin. You do not want the sides flexing while it is working, that is the same as no box. Bigger box is generally better than smaller box -- up to you to decide how much intrusion you can live with. If you place the speaker into a corner [rather than centered on the panel] that might leave room later for a decision to put in a port [to tweak deepest range].

    Doing this, you can spend more on the driver, and then boast that you built it yourself.
     
  17. ForistellFord

    ForistellFord In Maximum Overdrive

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    Sounds like a plan... but I want to use two subs and have the box cover the entire cargo area, so in essence the cargo area is simply elevated but still usable. Thinking maybe dual 10's? I have zero experience in this area, it probably shows. I can build a box, probably will. Any 'decent' sub or amp recommendations? And I suppose that head unit will do the job OK?
     
  18. burninbush

    burninbush In Maximum Overdrive

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    Wish I could recommend brands, but don't have that info. You could probably find reviews on the web for any piece you might want to buy. Last drivers I bought were brand Hella-Beat ... 10inchers in fact. That was probably 20 years ago, they still work very well.

    I'd start with one sub -- you might decide you don't need two, and you could then spend the same money on just one better driver. Like with cubic inches, there is no substitute for magnet weight in a bass driver. Look for that spec rather than some meaningless "power-handling capacity" number.

    Any box big enough to hold 2 @ 10" drivers is going to present serious wall flexing issues. Plan on doing lots of internal bracing.
     
  19. Rancherous

    Rancherous Administrator Staff Member

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    www.sonicelectronix.com go to the bottom of the page click on the Closeouts they have some screaming deals there and I have bought a lot of stuff from them quick shipping and ask them to ship from the Kentucky warehouse, you will have it in a couple days.
    When looking at amps and subs look at RMS or continuous power NOT Peak Power. Peak power is a marketing ploy for uneducated buyers and teens. I have seen Amps say 1,000 watts peak that are about 125watts RMS. Check out Sony or Dual to prove my point. Look to see if the amp is CEA compliant, this will pretty much guarantee you you are getting the power stated in the specs sheet of the amp.
    You will also need an amp wiring kit for the power you are going to be using, I would say a 4-8 gauge depending on amp. I use all 0 gauge OFC but I am running mega power, if you can get good OFC do it, Oxygen Free Copper.
    I would still go with a pre fab box, for what Sonic charges for a prefab I can't build one as good for the price. Just make sure you run another bead of silicon around the corners and inputs.
     
  20. Rancherous

    Rancherous Administrator Staff Member

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    BB that is why I suggested prefab box. I have 2 10 inch 1,000 watt RMS subs in a 3/4 inch sealed MDF box stuffed with polyfill driven by a MMATTS D300-HC amp which puts out 1,748 watts RMS @ 2 ohms and does not flex one bit. Front and rears are driven by a 125x4 RMS amp with 125w RMS 5 1/4s. I have not heard many systems that are as loud and clear as mine. I get lots of compliments on the Sound Quality of the car. I know I am driving a ton of power but I did it right, I did the Big 3 upgrade, upgraded to a police alternator, all wire is 0ga OFC, and the battery is a Die Hard Platinum. I could actually use to run a second battery as I still get light dimming at high volume levels even after all of the upgrades.
     

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