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post #1 of 15 (permalink) Old 02-12-2005, 06:12 PM Thread Starter
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Need help with sub box.

Need to beef up the bass in my bike hauling van. I built a box as big as I could get it and still fit it under the bench seat ( 8 x 16 1/2 x 24 1/2 internal dimensions). I put a pair of 10" MTX subs in the box but it sounds boomy and muddy. What direction should I go to get some tight bass out of this? Add packing to increase effective volume? Decrease the box volume? Go with only one 10" subwoofer? I'll be searching the net tonight but any help (or links) would be appreciated.

Also should point out that the amp is set up with the Low Pass Filter at 300 Hz and driving the speakers in stereo, not mono.

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Last edited by 12RPilot; 02-12-2005 at 06:15 PM. Reason: more
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post #2 of 15 (permalink) Old 02-12-2005, 06:34 PM
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Quote:
Originally Posted by 12RPilot
Need to beef up the bass in my bike hauling van. I built a box as big as I could get it and still fit it under the bench seat ( 8 x 16 1/2 x 24 1/2 internal dimensions). I put a pair of 10" MTX subs in the box but it sounds boomy and muddy. What direction should I go to get some tight bass out of this? Add packing to increase effective volume? Decrease the box volume? Go with only one 10" subwoofer? I'll be searching the net tonight but any help (or links) would be appreciated.

Also should point out that the amp is set up with the Low Pass Filter at 300 Hz and driving the speakers in stereo, not mono.
Did you use MDS board and there a formula on builting box for different size woofers. Also are you using a choke or eletronic crossover HZ rating. Is the box port which I recommend for 10in my opinion. 50-80 hz should be cut off.

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post #3 of 15 (permalink) Old 02-12-2005, 06:44 PM
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the low pass cross over is set at 300, you need to set it at something more like 80.

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post #4 of 15 (permalink) Old 02-12-2005, 06:50 PM Thread Starter
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I built the box out of 3/4 plywood. I didn't get any specs with these speakers. I can change the low pass filter to alot of values less than 300 so I'll give that a try tomorrow. Don't want to piss off the neighbors anymore tonight. I'm giving this website a try right now: http://www.diysubwoofers.org/

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post #5 of 15 (permalink) Old 02-12-2005, 08:44 PM
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Is it a sealed box, or ported? I like sealed boxes for tighter bass. If it's sealed you may have air coming through the cracks and you need to the seal the seams. Also you box may be to big, bigger is not always better. You should be able to find the air space specs online.

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post #6 of 15 (permalink) Old 02-12-2005, 09:02 PM
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Have you checked polarity of the wires? Changing to a low crossover point will help a ton too.

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post #7 of 15 (permalink) Old 02-12-2005, 09:11 PM Thread Starter
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I have the polarity of the two drivers matched. I could do a better job of sealing the box but it doesn't have the weird sounds that air leaks usually make. I'm going to experiment with box volume and crossover frequencies next. I appreciate all the help, folks.

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post #8 of 15 (permalink) Old 02-12-2005, 09:23 PM
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If I did my calculation right right now you have somwhere around 1.85cu ft. of air space in your box. MTX recomends for one 10 sub that there is .75cu ft, so you want 1.50cu ft. Box is just a little bigger than recommended.

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post #9 of 15 (permalink) Old 02-12-2005, 11:32 PM
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Quote:
Originally Posted by QulkDeAtH
If I did my calculation right right now you have somwhere around 1.85cu ft. of air space in your box. MTX recomends for one 10 sub that there is .75cu ft, so you want 1.50cu ft. Box is just a little bigger than recommended.

12rpilot,
Plywood is not good for building speaker enclosers. Particle board is ok but MDF (medium density fiberboard) is better. Use Liquid nails to seal the box then screw it together.
1st find out the required VAS (volumetric air space) and recommended application (sealed or ported) by the Manufacturer. Hopefully your box is sealed tight. Try filling your box with poly-fil tightly (available at any fabric store-it's the stuff pillows are filled with!) Then set the -x-over freq to 60 or 80 hz like was said above. If it doesn't sound any better, add a divider between both subs (so that each speaker has it's own chamber).
If QuickDeath's findings of MTX's specs are correct, your box is slightly overbuilt but it should still be ok (You'll get deeper bass but lose some power handling). He also says that each speaker requires .75cu ft EACH!....That usually means each speaker needs to be "in" it's own chamber..or else they'll cancel each others' waves resulting in muddy bass.
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post #10 of 15 (permalink) Old 02-13-2005, 02:23 AM
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Ditto on what everyone is saying about the box being to big which usually results in a muddy/boomy bass.


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post #11 of 15 (permalink) Old 02-13-2005, 03:23 AM
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I didn't take the time to calculate the enclosure volumes like calculated above. That said, if your bass is too boomy, or if the calculations are correct and you built your enclosures a little too big, DO NOT use the poly-fill. Poly-fill makes the speaker think that the enclosure is actually larger than it really is. You would be actually compounding the problem. Ditto on what was mentioned earlier, don't use plywood to build the enclosures, use MDF. Much heavier and denser. Much better for a sub enclosure.
Also, a sealed enclosure has a much tighter, clean sound than a ported enclosure. Generally speaking, the larger the air volume behind the speaker, the lower the speaker can go, but the bass output will be more sloppy. The reverse is true for smaller enclosures.

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post #12 of 15 (permalink) Old 02-14-2005, 07:28 AM
 
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Quote:
Originally Posted by QulkDeAtH
If I did my calculation right right now you have somwhere around 1.85cu ft. of air space in your box. MTX recomends for one 10 sub that there is .75cu ft, so you want 1.50cu ft. Box is just a little bigger than recommended.
Unless you know the exact speaker he is using, the values you quote don't mean squat......RT10-04's need 1.82 cu.ft. EACH.... so having that speaker x 2 in his box = box too SMALL.
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post #13 of 15 (permalink) Old 02-14-2005, 09:02 AM
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first change your crossover, its much too high!!!


like others said, mdf would have been a better choice of materials. try caulking the seams internally.

Chris
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post #14 of 15 (permalink) Old 02-14-2005, 05:45 PM
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Quote:
Originally Posted by taziscool
Unless you know the exact speaker he is using, the values you quote don't mean squat......RT10-04's need 1.82 cu.ft. EACH.... so having that speaker x 2 in his box = box too SMALL.
This may be true, but, if the output is boomy it can be assumed that the enclosure is to large. Most MTX woofers play well in smaller enclosures. If the woofer model was posted, the recommended airspace could be found.

Plywood enclosures do seem to be boomier that particleboard or MDF. However, internal bracing of the box will help to reduce this tendency. Make sure that the box is sealed well. An airtight enclosure is critically for the subs to be efficient and to sound good.

Last, the crossover is set too high. Typically, subs are set between 50-80 hz. In some circumstances, they could be set higher to compensate for a lack of midbass, but this can produce a muddy, boomy sound.

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post #15 of 15 (permalink) Old 02-14-2005, 06:01 PM
 
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Much good advice here, so I'll just try to add a little.

Some subs are designed for a ported enclosure, and some are designed to work best in a sealed enclosure. You have to find the manufacturers information specs on your exact woofers and build the boxes exactly to spec. I can't stress how important it is to have the right size enclosure and be ported correctly if it needs to be ported. Either way, sealed or ported you will get tight bass if you've built the box correctly and drive them with a good clean signal and proper power. Sealed is generally tighter, but ported will be great also if you do it to spec.

What kind of amplifier are you running and what kind of head unit or signal source? I've seen guys with amps that have "bass gain" that the owner will turn way up, then crank up the gain too high and both overdrive the amp and distort the signal worse by using the stupid bass gain.

Reduce crossover to 80-100hz
build boxes exactly to spec, including port tube diameter, depth ect. Making a perfect shape box with a port tube that isn't right will result in shit bass. It all needs to be to spec.
If you have a bass gain on the amp, set it to zero - set bass gain on the headunit to zero.

You could also have the drivers facing the wrong way. They called it "transfer function" when I was into this stuff, not sure if it's the right term, but it's basically positioning of the speakers in the car to get the best performance from the shape of the vehicle. Sometimes facing backwards away from you, pointed at the rear of the truck will improve performance drastically. You just have to play around a bit and adjust, listen, adjust listen.
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