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Everyone, big problem...

 

johnsimms
Unregistered guest
I've got two cerwin vega v-max 12" subs w/ a kicker kx600.1 mono d class amp and a pioneer premier deh-760 headunit. My box is tuned to 37 hz (i think) and it sounds really bad. The bass is too low, I'm not picking up any mid bass at all. My box is 2.0 cubic feet each chamber and my ports are 9.5 inches long. How can I make the mid bass louder? Should I tune the box differently? If so to what? and how long should the ports be to make it sound better? P.S. I have a little polyfill in the box also... about 8 ounces in each chamber.
 

Silver Member
Username: Fishy

Tamarac, FL USA

Post Number: 516
Registered: Sep-04
Is that the enclosure Cerwin Vega recommends? They don't give out any T/S parameters so its kinda hard to recommend another tuning point although you could experiment with shorter port lengths if you wanna tune higher.

Taking out the polyfil will help as well.

Where do you have it crossed over on that amp?

-Fishy
 

Silver Member
Username: Fishy

Tamarac, FL USA

Post Number: 517
Registered: Sep-04
How big are your port openings btw. A 4" round 9.5" long port gives about 36.5 Hz tuning in 2.0 ft^3.

-Fishy
 

johnsimms
Unregistered guest
hey fishy, its the guy with the grand marquise... The amp crossover goes from 50 to 200 its at about 150 now. My port opening is 4". Will shortening the pipe raise the frequency? if so will the mid bass become louder?
here are the specs...

SPECS FOR VMAX-12DVC

sensitivity(2.8v@1m): 92db
power handlingpeak: 800w
RMS: 300w
spkr. displacement: .13cu ft./ 3.7 liters

F s: 20hz
QTS: 0.31
QMS: 9.92
QES: 0.32
VAS: 3.28 FT3
XMAX: +/- 0.8"/20.3MM
REVC: 3.67 OHMS
TUNING FREQUENCY: 33HZ
PORT DIAMETER: 3.5"
PORT LENGTH: 17"
NUMBER OF PORTS: 2
TOTAL BOX VOLUME: 2.6FT
 

Silver Member
Username: Fishy

Tamarac, FL USA

Post Number: 533
Registered: Sep-04
Oh yeah, oops.

Did you ever make an opening in your rear deck to couple the airspace between your trunk and the cabin?

That might be why your only hearing the low stuff. Lower frequencies travel better through "solid" material. You're probably filtering out the upper bass frequencies through your rear seat. It seems from those specs that Cerwin Vega recommends a 33 Hz tuning frequency so I'm not sure raising the tuning frequency would help SQ much.

I'd work on creating an opening in you rear deck(you can cover with speaker cloth or leave whatever existing "thin" material thats already there in place) or maybe remove some insulation or other obstacles from behind your rear seat. I'd do that first before thinking about shortening the ports, but you might as well take out the polyfill.

-Fishy
 

Silver Member
Username: Fishy

Tamarac, FL USA

Post Number: 535
Registered: Sep-04
Well I plugged your speakers/enclosure into winISD and am not sure what can be done. I think actually lowering the tuning frequency might help more.

For what its worth here's what your box(2.0 ft^3 @ 36.5 Hz - green), that recommended box(2.4 ft^3 @ 33 Hz - white) and your box tuned to 30 Hz (1.9 ft^3 - yellow) looks like on winISD.

http://home.comcast.net/~guppyrig/wsb/media/322068/site1058.JPG

Your box and the recommended one are pretty "peaky" around 40 Hz which is pretty low. Tuning any higher will only increase this steepness, but altho tuning lower decreases gain in the upper region it decreases the lower stuff even more. If you have plenty of output as your box stands lowering the tuning point might be a better choice.

Really need to get to get an expert's opinion. I still think better airspace coupling will help more than anything.

sry I couldn't be of better help.

-Fishy

[note] to tune to around 30 Hz you need a 16.5" length of 4" pvc. I know that probably wont fit but you could use a 90 degree elbow fitting with another piece of pvc and give it a try. That way you don't have to cut or even remove your existing port. Just guesstimate the length through the center of the 90. I'd think you'd be adding about 6" of straight pipe.
 

johnsimms
Unregistered guest
Fishy, you were definitely right... I lifted the back deck up and low and behold the bass was amazing! And that was only with one port in the cabin, now I have to cut a hole in the back deck for the other port to come through the cabin. I adjusted the the gain all the way up, the hz's are at about 50, and the bass boost is about half way. The radio is at 80hz. It sounds pretty good, and if I change the ports to 16.5" than I would have to move the port it the front of the box. Is it that much of a difference?? and if I do change port position is it still going to sound good in the cabin??? Thanks John

p.s. i'm going to redo the back deck with 1/4 inch wood and fiberglass with holes for the port, so I can raise the ports to about 11 inches, but that is the max. What tune would that give???
 

johnsimms
Unregistered guest
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