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Thread: Got a somewhat crazy idea for my truck, you tell me what you think.

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    Noob mikeyt's Avatar
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    Got a somewhat crazy idea for my truck, you tell me what you think.

    I've got a 2006 GMC Sierra that I'm building a system for. I'm going with a 5 channel amp, 4 of them for the fronts and rears, and one for the sub out. The sub channel puts out 600 watts rms @ 2ohms. I'm going to get a under the seat box for it using dual 10's. Now the possible crazy part I was thinking about was this. I'm thinking about adding a third subwoofer utilizing the OEM location, it'll be a small 6.5". I was thinking if I were to use a distribution block and get all three subs rated at 200 watts rms @ 2ohms I could do that. Would it sound like crap though? Not sure if anyone has done this or utilized the OEM location with an aftermarket sub. This is the seven speaker BOSE system and while I was driving home, I was feeling what little bass it puts out and came up with this thought. My other thought was that having a sub between the seats I would be able to increase my xover point on the front 6.5" components since the bass is right there, maybe cross them at 85 or 90 and keep the sub channel up that high? Your thoughts please.

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    Noob mikeyt's Avatar
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    Re: Got a somewhat crazy idea for my truck, you tell me what you think.

    I forgot to mention it was a crew cab

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    Noob TheTodd's Avatar
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    Re: Got a somewhat crazy idea for my truck, you tell me what you think.

    In theory your distribution block idea would work, you’d just have to make sure the impedance would be acceptable for your amplifier... however... I don’t think it’ll sound that great. My thought process says that, even if your 6.5” can handle 200w, the 10s & 6 responses with that 200w will be different. You could possibly destroy that 6 trying to play lower than the sub/enclosure is capable of while those 10s are just happily chugging away. And it’s also possible you’d never hear that 6 begging for mercy.

    My thought would be to get that distribution block and get a small 2ch (& bridge it) or mono amp to run the 6 but high-pass it at, say, 40Hz or something which will give you that extra oomph up front and let those 10s free to dig the lower stuff. Again, just my thoughts. Your idea just might work and you may be very happy with it. Only one way to find out though.

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    Re: Got a somewhat crazy idea for my truck, you tell me what you think.

    Two 10's in that truck will be plenty loud. I know I have one. I run 1 10' in a center console box (It's 700 watt, 38mm xmax beast). It's probably similar to what two normal 10's can do.

    So I'm saying avoid the complications and do the 2 under seat.

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    Re: Got a somewhat crazy idea for my truck, you tell me what you think.

    Quote Originally Posted by mikeyt View Post
    "....The sub channel puts out 600 watts rms @ 2ohms. I'm going to get a under the seat box for it using dual 10's..."
    "adding a third subwoofer utilizing the OEM location, it'll be a small 6.5"...
    Your thoughts please.
    Very doable and could be fun, but will require some math building an external X-Over.
    Things to focus on:
    * ensure is that with the combination of the 3 speakers your total impendence doesn't drop below 2 ohm.
    * Build an external high-pass/Infrasonic X-Over to keep your 6.5 from playing lower than the mechanics would be happy with (personally i would try to stay between Fs and 1.5 x Fs)
    * And you might consider User a higher Ohm 6.5 so that you can naturally reduce power going into this speaker

    Now with all that said, this might not be the best option for you, but it is doable

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    Re: Got a somewhat crazy idea for my truck, you tell me what you think.

    Quote Originally Posted by mikeyt View Post
    ...Now the possible crazy part I was thinking about was this. I'm thinking about adding a third subwoofer utilizing the OEM location, it'll be a small 6.5". I was thinking if I were to use a distribution block and get all three subs rated at 200 watts rms @ 2ohms I could do that. Would it sound like crap though?
    First off, yes, if I'm thinking of how you are thinking. There's reasons it would sound like crap:

    If you think you could run two tens AND a 6.5 off the same subwoofer channel - this idea is doomed to fail. This is along the lines of all the people who had a light bulb appear over their heads and said "Hey... if a 15 can play super low but sounds muddy... and 10's can be super accurate but not play as low or as loud... what if I did BOTH a 15 and a 10?" ...and sadly all that happens in this case is you are limited by the worst of both. You don't get the best of both. You get a 15 that is barely warming up on the low stuff when your 10's start bottoming out, and you get the nice snappy kicks of the 10's ruined by the thwumping of the 15.
    Same would be the case for your 6.5 vs 10s on the same channel. Bad news, definitely don't.

    But if you are just itching to take advantage of that factory 6.5" subwoofer - I could see a way that is possible. One of the ways that most vehicles are lacking isn't sub-bass, but mid-bass. Let's give you some kick-ass kick drum.

    Assuming your components are going to be 4 ohm, you could pick up a dual-4-ohm dual voice coil 6.5" subwoofer (if anyone makes one, that is), and mount it up in that factory location. Maybe beef up that enclosure a bit, damping material on the outside, stuffing on the inside, at least. Wire up the one voice coil in parallel with your right component set and wire up the other voice coil in parallel with your left component set.

    ...And I need to clarify this, because I assume you are using the passive crossovers for your component sets...

    You would want (NEED) to wire that DVC mini-subwoofer to the input side of the passive crossover. AKA... the same as wiring it in parallel right to the amp. AKA... NOT to the output side of the passive crossover.
    That's important, because passive crossovers are designed for a specific impedance (meaning JUST the 6.5, and JUST the tweeter that the component set came with, on the output side of that crossover), so if you wired to the output side, then the crossover would see a different impedance and wouldn't produce the right frequencies. Bad.
    So... wire the DVC midbass driver in parallel to those front amp channels, one voice coil per channel, left and right.
    ...No, that isn't bad for a DVC midbass. And it isn't bad for your amp - it would see 2 ohms on that channel, make more power, which would be split between your three speakers (four voice coils) evenly.

    Now - this midbass is ALSO going to need it's own crossover. I assume you'll probably have the amp crossover set to filter the sub-bass from your front channels, so that will also take care of that for your midbass. But you don't want the midbass playing any higher than probably 300hz or 400hz, so I'd just add a simple 6dB/octave (that's a shallow slope) inductor starting at about 300hz. So you'd buy two of these:
    https://www.parts-express.com/dayton...-coil--257-554 and just wire that in-line on the positive lead to each voice coil on that DVC midbass.
    That'll start to filter the midbass off at 300hz, but it's a shallow slope so it'll only be 6dB down at 600hz, 12dB down at 1200hz. Should work decent for midbass support, then fading off as you go higher, without ruining your imaging.

    But if you don't want to try that, then I'd just skip it. You'll probably be fine with your components and the subs.
    Last edited by geolemon; 06-10-2020 at 04:16 PM.

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    Re: Got a somewhat crazy idea for my truck, you tell me what you think.

    @geolemon I just want to ensure that i am understanding your basic premise correctly... Are you saying that in the below picture, there would be equal power share? That each driver would receive 100 watts?

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    Noob mikeyt's Avatar
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    Re: Got a somewhat crazy idea for my truck, you tell me what you think.

    Each driver would receive 200 watts. taking the 600 using the distribution block. One lead would go straight to the 6.5" the other two would go to the box, one per sub. I would use dual voice coil 4 ohm DVC 10" and one 6.5" single voice coil 6.5" at 2 ohms. I came up with this to be able to use one amp if possible. Maybe I should just use two amps, one just for the 6.5, wouldn't that make it easier? I could use a full range and keep it around 90hz?

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    Senior Member Smitty's Avatar
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    Re: Got a somewhat crazy idea for my truck, you tell me what you think.

    Geolemon is on the right track but I will let you in on the lessons I learned in a similar quest. I had a 2005 Wrangler with a soft top and a laughable "Premium" factory stereo. The OEM sub in the console was comical as were the 4x6's in the dash.

    I put 5.25's in the dash and tried to wire a dvc 6.5 in parallel with the highs. The only dvc I could find was a cheap $20 dual 8 ohm unit. I had trouble getting the levels to match and the cheap 6.5 couldn't hang. Lasted about a day. I ended up swapping the 2 ch amp for a 4 channel and using a better 6.5 to fill the 250hz to 80hz region.

    It can work, but if your mids are blending well with your subs, I may not be worth the trouble. I was just trying not to put a sub in my Jeep...still installed a sub.
    Meh, it'll play.

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    Re: Got a somewhat crazy idea for my truck, you tell me what you think.

    So here's a diagram, since a picture is worth a thousand words. Pardon my crappy art skills.
    The trick here is to find a DVC 4 ohm 6.5" to use in that factory box:
    Click image for larger version. 

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    And I drew a 2 channel amp just to simplify things.
    Again, I'm assuming on these two amp channels that you have a high-pass filter turned on, to block the bass for both the midbass and component set.

    And like Smitty said - you might shop around for a good driver.
    But, fortunately, I'm again NOT proposing that you use this for a subwoofer - this is repurposing that 6.5" box with a new DVC 6.5" strictly for midbass support duty. Way easier than trying to get a 6.5 to do subwoofer duty.

    EDIT:
    Also, you will want a 6.5 that handles your amp's power. Each voice coil is getting as much power as each channel of your amp, so if your amp was 50x2 then you'd need it to handle 100 RMS. And if your amp is 100x2 then you'll need one that can handle 200w RMS.

    From a SQ standpoint, I think it could work out nicely - It really should add midbass, but shouldn't distract from your component set for two reasons:
    1) you are filtering it to only play midbass, with those coils. Humans are less able to audibly locate sound sources, at lower frequencies.
    2) It'll be receiving 2x the power as one of your component speakers, but it won't be 2x as loud as each of them. Higher power handling speakers are less efficient (that heavier voice coil is the culprit), and also "add power!" is always an inefficient way to get louder. It takes a 4x increase in power to get 2x as loud, for any given speaker, and even that doesn't account for various efficiency losses. So I'm confident that it'll be putting out more bass than having just one more [of your component set's] 6.5", but not so much that you have this distracting jackhammer pounding away... unless something attached to it or near it starts vibrating.

    I think it could work out nicely - I know if it were me, I'd at least have to give it a try. Cheap experiment with a high likelihood of success.
    Last edited by geolemon; 06-11-2020 at 07:56 AM. Reason: added EDIT comment

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