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Old 23rd June 2006, 04:52 AM   #1
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Default Help on sub enclosure:

I have two G5 DVC 10" Boston subs, and need to build an enclosure. I have enough power to use a fully sealed enclosure. however, i am not sure if it is optimal for sound quality to enclose both subs in once box, or use two separate, as outlined in this specificaitons brochure by Boston: http://www.bostonacoustics.com/manuals/G5_GTR_Man.pdf

Any input as to the box , material, etc which will result in the best tight bass, please let me know. thanks for reading.
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Old 24th June 2006, 03:30 PM   #2
hooha is offline hooha  Canada
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They look like pretty nice units...

Having two subs mounted in one box vs. separate IMO is largely dependent on the environment they're going into. IOW, can your vehicle accomodate room for one box or two? Bass in music is largely in mono anyway - separating your subs to achieve "better sound" in such a small compartment is moot.

Mounting two subs in one box is fine, so long as you build the box strong enough to handle the stress of two drivers.

MDF is common, but you can use baltic birch which is lighter but more expensive. I'd probably go with 1" thickness. Brace it well (if you go with 2 in 1) and seal it well. With that, you'll have bass that will part your hair.

Mark
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Old 26th June 2006, 04:52 AM   #3
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Default Thanks...

hooha, thanks for replying.

I have a 4Runner, SUV, which has plenty of space in the rear cargo area- about 4 cubic feet +.

I want to use a detachable enclosure (so i can remove it in case I need the space). I can fasten it securely via very strong bungee hooks (I have spots to attach them).

In this case, I will build one box, divided in the middle, as to mimmic the dimensions of the individual chambers perscribed by Boston. Do you agree? As you said, shouldn't make much of a difference, especially since this is for mobile use.

So, you advise sealing, without a port hole? These are the amps I will be powering the subs with:
Audiobahn A12005DN

I have two of these. Since the subs are dvc, I plan on doing a parallel setup, which should give me 2 ohm load to each amp = 600W rms. Reason I got these is because they seemed relatively cheap ($156 + shipping USD/ amp), and the THD seemed reasonable. Again, I'm an amateur, and far from savvy when it comes to this, but I'm trying to learn as I make my system. What you think?

Now, for material. Is the sound better with either MDF or birch. I'm not concerned with the weight of the material; just the quality of sound. If It's just a weight difference, I will likely go with the 1" MDF board (because it easily available at most Home Depot stores nearby. I'm not sure if they stock birch, but if it leads to better sound, I will try to get a hold of some.

Sealing the box. I assume just using screws is not enough as there are little spaces left where the boards meet. Do you recommend any liquid fasteners/ glues/ sealants for the areas where the board ends meet? Strive to make it air-tight and solid as possible?

Thanks for the input. Sorry for the longwinded post. Trying to be as clear as possible.
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Old 26th June 2006, 06:34 AM   #4
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Default Another thing.

Perhaps I should start a new thread about this. Anyway.

My car's alternator outputs 70 amps. I am planning on replacing it with one which produces 160. Will that be enough to power my car's accessories, the two amplifiers listed above, and also another 4 channel amp powering 80-100w RMS speakers?

The sub amps are class-d. The 4-channel amp, which I haven't purchased yet would preferably be around 400w rms, and be a/b or d class.

I am wondering how many amps the three amps will likely draw at the most; 1) if all are class d; 2) or if the two are class d, and one is a/b?

I've looked around, but haven't found much useful info. The crutchfield site (http://www.crutchfield.com/S-WRJqReu...ech/kb147.html) has some sort of info, but doesn't state for which class of amps the calculations are. Any help will really be appreciated, as it is crucial to what type of alternator I need. Thanks for looking.
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Old 26th June 2006, 05:36 PM   #5
hooha is offline hooha  Canada
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Class of amplification is not relevent when determining total current draw. Using Ohm's Law (Current = Power/Voltage) based on your requirements you will have:

1600watts/14 volts = 114.3 amps current draw from your power amplifiers alone.

Your idea of getting a 160amp alternator is a good one. You may find however that even that won't be enough when you're pushing your system hard. I would suggest getting a separate battery for the system on top of your big alternator - forget about adding caps.

Follow Crutchfields recommendations for power wires.

Now, onto the boxes...

You mentioned you want 'sound quality' out of your subs. For clean output go sealed. If you want volume and boom, go ported. A partition between the subs is good - it will act as your brace for the box. Go 1" MDF all around, use plenty of wood glue and caulk the inside edges. Mount the drivers using a good gasket material - the subs probably come with them.

You're going to get a lot of cabin gain in the bass region. Therefore for sound quality you probably won't need to play with the bass boost on the amps - but you be the judge.

Best of luck.

Mark
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Old 26th June 2006, 06:11 PM   #6
dfdye is offline dfdye  United States
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Sweetrobot,

I like your idea of using a divided single box. This would be my preference if I were building an auto box for these. I would add some general box building tips:

1) For these subs, I would use two sheets of 3/4" MDF for the front of the boxes for additional mechanical support (or double up 1" if you are already using 1" for the rest of the box). This will help stiffen the enclosure and reduce box vibrations. Unfortunately your car's vibrations will probably be much worse, but you can always try for perfection! Use regular wood glue (Titebond II is my personal favorite) to laminate these two sheets together. You may want to cut the mounting hole in one of the sheets first and use a router with a pattern bit to cut the holes in the second sheet after you glue them together. This has worked well for me in the past, but be aware that this can generate a lot of MDF dust, so wear a mask!!! If you donít, you will have papery snot for a few days. Donít ask how I know.

2) If you do go with the sealed boxes (which I would recommend), I would run a bead of silicone caulk around the interior corners of the boxes after you have finished building to minimize air leakage from the edges.

3) Use regular wood glue for the joints. Anything else is overkill.

4) BRACE BRACE BRACE!!!! Braces between the faces of the wood will reduce box vibrations which result in you hearing more of the speaker, and less box vibration. Be sure to brace asymmetrically so you don't get standing waves between faces.

Hope these help, and good luck! Remember, though, that the noisiest part of your system will inevitably be your car's vibrations! So if you don't get everything perfect, the chances of your box causing ridiculous sound issues is minimal.

David
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Old 1st July 2006, 10:24 AM   #7
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you said best tight bass???????

not gonna happen so much in that big of a car if you plan on putting the subs in the way way back.
low frequincie sound waves have alot of distance and develop quite easily in that enviroment, tight notes just decay really fast in big suv's with subs mounted in back. therer is no "best" box for tight notes in suv with subs in back is some vented enclousure but with 20,25,31.5, down allot at least -10db and 40 50 and 63 hz climing up back and 80hz at --zero and than 100hz diveing off to -12db 125 at -12db and a slow climb back up to 400 being at zero.. and taking into concideration you have a 45hz boost on a "bass knob" or a bass boos on amp. that gives you head room to enjoy the bass boos knob and still get good sound out of it.

Rember you mids and midbass IS what mostly determines to you ear and brain how tight the bass is. I can make a 15 inch woofer in a big big vented box sound as punchy as 8 8inch woofers in small sealed boxes.. careful eq'ing and get you midbass in sealed enclousures, that is most important.

But if what i am saying makes no sence and you feel likle slaping me for telling you what you didnt want to hear than i guess you could go with plan B and put the subs in small sealed enlousures and put them in the kick panneles. you will like the way that sounds allot. but it might be kinda hard to drive so you might want to make the driver side speaker wire have quick disconnects on it so you can ditch a sub to back of car when in dribing mode
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Old 11th July 2006, 04:33 PM   #8
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Default ...

hooha & dfdye,

I have a question about this:

"Mount the drivers using a good gasket material - the subs probably come with them."

and

"You may want to cut the mounting hole in one of the sheets first and use a router with a pattern bit to cut the holes in the second sheet after you glue them together."

I haven't looked into the box of the subs yet, but I am not sure if they come with good gasket material. A big question mark to me is how will I actually mmount the subs within the enclosure? Will I mount via the magnet end / bottom, or the other way around? I have no clue on how to mount in completely enclosed box. I've seen boxes where the face of the subs is revealed, like a typical speaker setup, but never the inside of a fully enclosed.


dfdye,

Not sure what exactly you mean by your "4) BRACE BRACE BRACE!!" bit. Dy bracing, do you mean I make the box itself asymmetrical? What would I use for bracing? I am sorry for the odd question, but I'm really confused for some reason, regarding the bracing. If possible, can you dumb it down any more?




30bandgeek,

just to clear it up, I have a 4Runner, which has an interior volume equivalent to a typical hatchback sedan. The only difference is that there are no obstructions between the cargo area, and the passenger space. the subs will be no more than about 3-4 feet from me (driver, unless i'm drunk), and 1.5 feet from the rear passengers. factoring in and waves that must travel to the very rear will add no more than 2 feet. I don't know if htis makes any sense. I think it will not make much of a difference, as I stated above, the interior volume is not quite like an escalade/ navigator.
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Old 11th July 2006, 05:53 PM   #9
hooha is offline hooha  Canada
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What? You have the subs but haven't opened the boxes to look at them yet?? Geez, what are you waiting for?!

A lot of subs these days come with thick rubber that wraps around the edge of the driver. This rubber can be removed if it gets in the way of the cabinet design/mounting. If your drivers come with this thick rubber it will be fine. If not, you can use standard foam stripping available from any hardware store.

I would suggest to swing by an audio shop like Best Buy and take a look at some of the sub boxes they have there. Check the double sub boxes like this one to get an idea of how to partition your box (the one I linked is a ported one but you should get the idea).

Mark
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Old 11th July 2006, 08:39 PM   #10
dfdye is offline dfdye  United States
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Default Re: ...

Quote:
Originally posted by Sweetrobot
[B]hooha & dfdye,

I have a question about this:

"Mount the drivers using a good gasket material - the subs probably come with them."
Good weather striping from a hardware store will work well. I use it all of the time. I use the foam double stick tape style which is about 1/4 to 1/2 inch wide and 1/8 to1/4 inch thick depending on what the application is. I run a strip around the driver and pull the backing off of the foam right as I am about to install the driver into the cabinet.
Quote:
A big question mark to me is how will I actually mmount the subs within the enclosure? Will I mount via the magnet end / bottom, or the other way around? I have no clue on how to mount in completely enclosed box.
I mount from the top side of the box with the magnet inside of the box. I usually run a rabbet inside of the hole to flush mount the sub, but this is just for looks and isn't necessiary on most boxes.
Quote:
Not sure what exactly you mean by your "4) BRACE BRACE BRACE!!" bit. Dy bracing, do you mean I make the box itself asymmetrical? What would I use for bracing? I am sorry for the odd question, but I'm really confused for some reason, regarding the bracing. If possible, can you dumb it down any more?
by bracing I mean putting additional pieces of MDF in to make the long faces of the box less resonant. For example, if I take a 2" wide strip of MDF and attach it perpendicular to the face of the box, then I will stiffen the face and cut down on internal box resonances.

I'll post more info later, and I may even be convinced to draw you up some plans if I can get a few minutes later tonight.

David
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