# Cabin cancelation issues



## Bugflipper (Apr 16, 2010)

I am having trouble with rear seats eating up the bass in a vehicle.With the seats down and the subs loaded on the back gate everything is perfect. When the seats are up, they are at such a steep angle it just cuts the bass to nothing. They are plastic backed, such as a cargo area. I have tried to load the subs on the back of the seats but the same thing happens. 

Years back when I owned a shop I designed some boxes for a guy into spl competition. I tried to draw a sketch (sorry). The front would be open. Lets say 5" above the woofer so it could load. Then it would be above the rear seat facing forward. The original design was with 4 boxes with 8 15" and 4 hcca 2100's. Believe it or not sq was very good. Just way to much spl.

I am open to any ideas since this has me baffled. This is the grocery getter/ t-ball vehicle so I want to stay small on power if I can.

HHR SS 
JL 10w3v3 x 2
Orion HCCA 250 running at 400 rms total (200 per sub)
Box is slot ported tuned to 26 hz.
I am into rock and don't like boomy. Only tight bass.
I have not really kept up with current events. Just looking for ideas on what to do. Normally I only run 1 10 in a vehicle but this was a very large area. Thought about even angling at a 45 to the rear wall to get it to bounce over the rear seat but would loose the loading. Any ideas will be very much appreciated. Please ask to clarify that lousy sketch if needed. BTW box would be closed on all sides but one. Ramp on inside was phase 2 of what we started with. Increased output and sharpened punch.
Thanks


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## Lanson (Jan 9, 2007)

have you read this:

Aiming a woofer box in a car trunk - bass cancelation -


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## Bugflipper (Apr 16, 2010)

Very good article. This is the problem, now searching for the solution. I have tried the box in every conceivable location firing up and to every direction besides down. The angle of the seat must direct it downward. Then it bounces off the flat back wall then to the seat back and downward in a continuous loop. Which cancels the new waves? There is turbulence in the interior from the pressure waves. In the front the wind can be felt on the arm hairs from the excursion. Just very little sound. Seats down there is a lot of bass. Today I put the spl meter on it with an Owl City song. 140 with seats down. 118 when up. With subs off it is 114 db. So pretty well dead. I am truly not into pounding bass anymore, the 140 was too much for me. But almost no sound at the 118 isn't getting it either. Most of my other cars run in the 130-136 db range with the subs blended for transparency with a bit of punch, not high spl.

BTW up firing does not cancel but output is only 120-125 or so on most of the music I listen to. Without the subs being loaded does not blend well with the millies. I have relied on loading subs for years to keep the rms low and significantly increase output. It makes the equipment last much longer. A lot of my subs and all the hcca amps are 15 or 20 years old with daily use.
Thanks


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## galacticmonkey (Apr 28, 2010)

Just do a small cutthrough for a port or something and do a bandpass.


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## Bugflipper (Apr 16, 2010)

Sorry these are 10w7 subs. Had a brain fart. I picked them up used a while back. When searching for the price online I paid less than w3 cost new.


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## Lanson (Jan 9, 2007)

I think you should try firing down. Put your test box up on some boards, and get a little height off the floor. Let me know how that sounds.


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## Bugflipper (Apr 16, 2010)

fourthmeal said:


> I think you should try firing down. Put your test box up on some boards, and get a little height off the floor. Let me know how that sounds.


 Fired them down stacked on 4x4" posts (3 3/4" gap to floor). Seats down 138 seats up 118.
When I was messing around in the shop I noticed the plywood sheets and decided to try one. I put the base at the box which was facing rear. And made it lay over the back seat. It made a ramp towards the drivers seat. So anyways 140 with seat up. My plan now is 3/4 mdf covered with vinyl. Hinged to back of box with subs loading on rear wall. And some wheels to ride the seat as it goes up and down. When down it will be flat enough for groceries. When up It could be used for storage of sports gear.

Right now it is too loud for me so I may have to play around with the gain. I haven't had the best luck out of JL with low wattage. Worst case scenario I can seal the ports or kick one sub out.


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## Ginobli07 (Jan 21, 2010)

Bugflipper said:


> Fired them down stacked on 4x4" posts (3 3/4" gap to floor). Seats down 138 seats up 118.
> When I was messing around in the shop I noticed the plywood sheets and decided to try one. I put the base at the box which was facing rear. And made it lay over the back seat. It made a ramp towards the drivers seat. So anyways 140 with seat up. My plan now is 3/4 mdf covered with vinyl. Hinged to back of box with subs loading on rear wall. And some wheels to ride the seat as it goes up and down. When down it will be flat enough for groceries. When up It could be used for storage of sports gear.
> 
> Right now it is too loud for me so I may have to play around with the gain. I haven't had the best luck out of JL with low wattage. Worst case scenario I can seal the ports or kick one sub out.


Can you take pictures of the setup and post them? I sounds like an interesting idea, and I would love to give it a try in my own car.


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## Lanson (Jan 9, 2007)

Interesting solution! Just shows that experimentation usually reveals a solution, even if it is a wild one.


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