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Sub Positioning

Discussion in 'Audio' started by maxq15, Feb 10, 2002.

  1. maxq15

    maxq15 Registered Member

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    OK CK5 audiophiles, I've seen alot of discussion about mounting subs of various sizes in the rear side panels. I seem to also remember a post discussing mounting them in the doors. My question......has anyone ever installed, or seen installed, a pair of 8's mounted in a downward-facing box, one under each front seat?

    In my mind I'm struggling with rear side panel mounting, building boxes that intrude into the rear cargo space, and all of the other combinations I've seen. I'm just kicking the under-the-seat idea around in my head and figured I'd throw it out here for discussion.

    Those who think money can't buy happiness don't know where to shop.
     
  2. 1986Blazer

    1986Blazer 1/2 ton status

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    Under the seat would work great! Alot of home stereo systems have hidden sub boxes that are about the correct size to fit under a seat in the K5. You would need to make it custom yourself but I should fit. Greg72 can probably help more that I can. The sub box I am making now (pics are on my webpage) only intrudes 4" out from the rear side panels. Granted my design is overly complex due to the materials I am using but Greg72 can help you in making a smiliar box with wood.

    <a target="_blank" href=http://www.geocities.com/keywestk5/KeyWestK5.html>http://www.geocities.com/keywestk5/KeyWestK5.html</a>
    So I says to him, I said, "get your own monkey."
    1986 K5, 350 GM Crate, 700R4, NP208
     
  3. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    MAxq,

    The problem is going to be finding the space under those seats! I know that on my '72, there's quite a bit of room on the passenger side because the seat is non-adjustable to there are no tracks or return springs. The driver's side has a LOT of gizmos under there!!!! I was able to get an amplifier mounted to the underside of the seat (not on the floor, actually under the seat and above the mechanisms)....but there's NO way I could've gotten a subwoofer under there.

    Remember the seat foam sags when you are actually sitting in the seat, so if you take a "static" measurement, it won't be right. Trust me, when you sit down... the seat foam will hit that obstruction underneath and you'll feel like you're sitting on a pile of bricks.....not a seat!!! [​IMG]

    Unless you're thinking about raising the seat mounts substantially, I think you are simply not going to have the room to do it..... If it was easier, that's what I might have done myself! [​IMG]



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  4. Itali83

    Itali83 1/2 ton status

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    I kicked around that idea too about under the seats with 8" subs. But there just isn't enough room down there. Once you calculate the area inside the box you are looking at about .5 cu.ft. or so. I thought about it for a long time and just couldn't seem to make it work. I'm not saying don't think about it and try stuff, becuase I'm not the most ingenios guy when it comes to building boxes and figuring out cu. ft etc. etc. Good luck to ya and if you do get it to work. I wanna see some pictures!!!!!! if all else fails, I built a rectangle box put my 2 10's in there and put it behind my rear seat. I used velcroe so when the seat folds, the box moves, and so forth, it isn't bad at all and takes up very little space. I was totally against cutting my side panels so I had to go that route. good luck to ya man!
    Ben 87 Jimmy
    <font color=blue>Rust=Bad</font color=blue>
    <a target="_blank" href=http://www.bens87toy.alloffroad.com>www.bens87toy.alloffroad.com</a>

    P.S. Greg is the man, so if you have questions ask him!! One of the nicest guys on this board!
     
  5. bassplayer4x4

    bassplayer4x4 Registered Member

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    Greg, I am considering the same path with my new (built) 72, but what about using a "free air" sub in the side panels in the back? Right now the vehicle has no side panels in the rear at all, there seems to be enough space to flush mount a nice 8 or 10" sub in there, so long as its free air, it should sound good. Not all the subs need boxes, unless you just want to super thump at the stop lights. Do you or anyone here have a template for the side panels, it would be nice to have some to start from, but there are none there now. Anybody ever drawn them up?
    Thanks,

    Phillip
     
  6. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Phillip,

    I think that you may be able to do something in those side panels.....but the limiting factor will be the mounting depth. I can't recall exactly how deep those bedwall areas are, but it can only be around 4 - 5" at most. I think most reasonably sized subwoofers are going to be too deep to "flush mount" as you suggest....though I've seen a number of folks use a spacer ring to "cheat out" an extra inch or so!!! [​IMG]

    As far as a template....I'd spend about 20 minutes making one out of cardboard....it's easy to do, just cut each shape and start taping them all together.....you don't have to make it all in one BIG piece....in fact its a lot easier to do it in multiple small parts. Once you complete your "collage of cardboard" you could trace that shape onto a single piece of cardboard just to double-check everything. Or if you're feeling confident, you could go straight to MDF, or whatever you decide to use for the side panels.

    The stock panels were only around 1/4" thick....too thin to support the weight of a subwoofer, and certainly NOT rigid enough to contain the airpressure of a sub. That will be your next challenge.....figuring out how the make sure that the subs are the ONLY thing vibrating!!!! [​IMG]

    Good Luck....



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  7. rebelk5frk

    rebelk5frk 1/2 ton status

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    Another option if you aren't out for a TON of bass and only wanted one subwoofer you could build a custom console/hidden speaker box in between your front seats. I go the idea from some JL audio hidden boxes for the 92 and up Yukon's etc. You should be able to fit a single 10" or 12" and have the bass right up in the middle of the passenger area and not really lose any cargo space.
     
  8. maxq15

    maxq15 Registered Member

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    I thought of going that route as well, since I don't really like the stock center console that I have. Although I haven't had the time to actually plan any of it out, for some reason I am having a hard time visualizing the actual size of a .5 cf box. Another question for anyone out there.......if I have 2 subs in the same enclosure, are the space requirements additive?

    Those who think money can't buy happiness don't know where to shop.
     
  9. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Max,

    A simple way to visualize it......a 1 cubic foot box is 12" x 12" x 12"....for a .5 cubic foot box, you need to cut one of those dimensions in half (12" x 12" x 6").....you could also stretch one dimension and shorted another (16" x 9" x 6")......you get the idea.

    Keep in mind those are "net" values.....which means that they are the "internal" measurements for the box. To get the overall dimensions, you will need to add the thickness of the materials you are using to those dimensions.....also, most manufacturers expect you to subtract the displacement of the speaker from your box calculations too (the speaker magnet, frame, etc).....they'll give you the spec (usually in cubic inches) but it's your responsibility to factor that in also.

    As for you question about 2 subs......YES! If the sub is designed for a .5 cu ft. enclosure, then you can run 2 of them in a 1 cu ft. enclosure.



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  10. maxq15

    maxq15 Registered Member

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    What are the effects of a box that is slightly larger than optimal or slightly smaller than optimal?

    Those who think money can't buy happiness don't know where to shop.
     
  11. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    MaxQ,

    Let's talk about sealed boxes....since it's easier.

    When a speaker is mounted in an enclosure, and it receives a positive electrical signal, the speaker will begin to move 'outward'. In the most simplified description, the thing that stops the speaker from moving outward is the "vaccuum" created behind it inside the subwoofer enclosure. When the speaker receives a negative signal, the speaker is pulling itself 'inward' and compresses the air inside the enclosure. The limiting factor is the amount of air available to compress.......more air is easy to compress......less air offers MORE resistance to being compressed.

    SO.....All other things being equal, the smaller the box is the more it will limit the "excursion" of the speaker...this is a factor called 'damping'. The air in the box is creating resistance against the speaker. Damping is sort of analagous to a shock absorber on your truck. You may get more suspension motion without it.....but you may not like the way it rides at all!!! [​IMG] The same is true for speakers and damping.

    An overdamped speaker will not be able to play low frequencies as well, and it will use up a LOT of amplifier power but achieve very unimpressive sound pressure levels. An Underdamped speaker will allow the speaker to hit lower notes.....but will lose control of the speaker.....and it will sound "sloppy"......sort of like the way your truck drives with no shock absorbers!!!! [​IMG]

    If you study the response graphs for a speaker in an "optimum" enclosure, the frequency response should be fairly "flat"....that is, it should play all of the frequencies at about the same volume level.....there's shouldn't be any "boominess"....

    A box that is too small will have an exaggerated "bump" in one frequency range, and the rest of the frequencies will be substantially lower in output. In a box that's too big....the frequency response is likely to be flatter, but the output volume will begin to suffer.

    So that's about it. This is a VERY oversimplified example....but the bottom line is that you should build a box that's as close to the manufacturers specs as possible. If you don't have the space to build that box, you should look at another brand of speaker, or size of speaker, that has been designed to work in the space you've got....

    Hope that makes it clearer.....and not WORSE!!!! [​IMG]



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  12. maxq15

    maxq15 Registered Member

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    Hey Greg, hopefully this is the last of the "stupid" questions.....at least on this topic. The Subs that I have are Boston Accoustics ProSeries 8.5lf's. According to BA's tech sheet, they recommend an enclosure that is .33cu ft and go on to recommend 6.5" high x 9" wide x 9" deep (internal). Do you still think those will not fit under the seats up front? Next question is, assuming I get them to fit, where should I face them, up, down, front, back?

    Those who think money can't buy happiness don't know where to shop.
     
  13. tightwork 82 K5

    tightwork 82 K5 Registered Member

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  14. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Maxq,

    Well assuming you used 3/4" MDF for the cabinet.....you'd need to add 1.5" to each of those dimensions to get the "external" dimension. So your 6.5" height is up to 8".....and you still haven't left any room for the cone's excursion (either up into the seat, or down towards the floor)....I'd say you'd want at LEAST an inch for that....probably more. Now you're looking at 9".....!!!

    I know that I don't have 9" of room under my seats.....even as a "static" measurement. Once you've got someone's butt in the seat pushing it down.....you'll lose a couple inches off whatever static measurement you take.

    So I think my answer is still "NO" it wouldn't work.....or it would be SO much work, that for an 8" sub it wouldn't be worth the effort.



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  15. maxq15

    maxq15 Registered Member

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    Curses, foiled again!!!

    Geez Greg, you're not going to cut me any slack on that under-the-seat location, are you? I'll have to play around with some cardboard and a tape measure.
     
  16. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    MaxQ,

    Hey man.....I'm not saying it's impossible! /forums/images/icons/laugh.gif

    ....just that the whole "Return On Investment" (Time &amp; Labor vs. Result) is very poor. It will take you HOURS &amp; HOURS to figure out how to make that work, and you still only get an 8" sub in there.......that's really not going to pay the big dividends for all your labor.

    I spent LOTS of hours building my sub cabinets, but the payoff was good because I got two ported 10's working and they have MUCHO bass...... /forums/images/icons/cool.gif

    Look on the bright side.....if you DO figure it out, you'll be a hero!!!
     
  17. creampuff90k5

    creampuff90k5 1/2 ton status

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    Not sure if you have seen these, but there are a couple of small, self-amplified subs available that will easily fit under a seat or inside a center console. In particular, check out Clarion's SRV303 and Kenwood's "woox".

    Now granted, you are not going to be able to rattle windows and set off car alarms with the bass, but they're perfect for that little extra punch needed with the windows down or top off while on the highway. Easy to install and cheap (about $150) too.
     
  18. ChevBlazin

    ChevBlazin 1/2 ton status

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    You may have already gotten your answer, but here is what I have dona and found. Forst of all, The farther the sub is from you the better it will sound. So putting it in the back is your best option. Subs need to have a certain ammt of air space to work with also so jsut cutting holes in the side panels and mounting them there will not sound very good, it is not sealed off good enough. A sealed box is cheaper and easier, but a bandpass box will usually make a smaller sub sound larger (the ones with plexiglas covers and ports out the back) If you go to www.crutchfield.com they will usually say next to each sub how much air space is needed for both types of boxes. I tired a different approach when I installed my sub. I made a bandpass box that fits between the two front seats (where the center console used to be) There is a clear window on top where you can see the sub (I think it looks cool that way) and the ports are on the bottom and face the rear of the truck. The setup sounds great in the front two seats, but gets kinda lost sitting in the back. I dont know what taking the hard top off will do to any of these setups so that is totally different. in case you are wondering I have an 8" Rockford Fosgate and a Pioneer (i think 150 watts bridged) amplifier. I'll try to post some pictures when I get a chance. hopefully some of this can help
     
  19. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    ChevBlazin,

    Could you tell me more about "why" a sub mounted futher away from you will sound "better"? /forums/images/icons/crazy.gif
     
  20. maxq15

    maxq15 Registered Member

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    That was going to be my question too.
     

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