I am running a 2x12 inch sub system in a ported box tuned to 40Hz. I've found that I get the best SPL when the box is face up (facing the boot lid) right at the back of the boot, so ports and subs are about 10 inches from the boot lid. No biggy.
The problem I have is that if I feed in 200WRMS into each sub I get 139dB and if I feed in 800WRMS I still get 139dB! There's no gain in pressure. I know that the amplifier is not limiting and it's within the sub limits as they're not distorting (as I've done and out of car test).
I'm assuming that the reason for this is that I'm getting a loss in pressure somewhere along the line. Can anyone shed some light on this? I'm running this system in a 1996 Holden VS Calais. At the moment the boot is stock. I've got some ideas on what to do, such as tighten the boot latch, glue the struts of the boot lid to the boot skin, and seal the vent holes. Is there anythign else that anyone has done or can think of??? I don't think any of this will make a huge difference.
Is there anyone that has got over 142dB in a commodore before?
Full Version: SPL in Sedan Problem
QUOTE
Originally posted by Roddas77:
Is there anyone that has got over 142dB in a commodore before?
yeh a few of us have Is there anyone that has got over 142dB in a commodore before?
you said your boot is currently stock, so if the subs sitting face up on the floor playing into the lid is must be making a heck of a racket on the outside right? sound deadener is your friend, use it if you get really excited, might i suggest a fibreglass bootlid cover also, i mean theres a fair bit u can do, but first id be making that boot panel as stiff/heavy as possible instead of sitting there vibrating and resonating its head off
what meter did you test it on, cause down my way theres these boobs that own a shop, and every one thats tested on that meter have got no more then 124 db (its always 124 db) so it might pay off to test it somewhere else.
QUOTE
Originally posted by GMHVNS:
yeh a few of us have
Hehe - I don't think it counts when your two back seat passengers are 18" RF Subs yeh a few of us have
I'm with Adam on this one - SD up your boot lid - then possibly look for cancellations that could occur with your sub mounted like that. It seems the popular method for subs facing up in a commodore is to have the sub face being the new boot floor.
Like This:
Sir - Nah, it was tested with proper equipment and calibrated mic and everything. Got higher on another car.
Yeah I value my backseat a bit more than some, occassionally I have more than one passenger, although putting two 18" subs in there like GMHVNS would soon fix that.
Is the main reason for the SD to add weight to the boot lid so it doen't resonate? Doesn't SD absorb sound though? Or have I got it all wrong?
Yeah I value my backseat a bit more than some, occassionally I have more than one passenger, although putting two 18" subs in there like GMHVNS would soon fix that.
Is the main reason for the SD to add weight to the boot lid so it doen't resonate? Doesn't SD absorb sound though? Or have I got it all wrong?
Often SDing can help SPL, as your panels vibrations are esentially losing energy (SPL) out in to the outside world. Rather than sound absorbtion, or the softer SD product, get the thickest, toughest, stickiest crap you can get. Dynaplate being one of the best known to man, FG being another good one
fibreglass the boot lid, it will help a fair bit. First i would fill up all teh gaps in the boot lid and see how that goes, should reduce rattles dramaticaly and give a bit more sound energy
As a simpler and cheaper option maybe try adjusting the boot lid lock so the boot is held a bit tighter - I did that with my hatch and is stops the hatch flexing as much. I now have to close the hatch, them push down on it to get it to clip fully.
Would facing the sub and port up at the boot lid help with one ten in a ford fairmont sedan. It did 141 db regrdless of where i rear loaded the sub (rear corners and right in the middle.
I have seen a 15 with 1000w amp do 140db from 35hz all
the way up to 50hz used 3 differant boxs still same added more power a bit better changed to 12s
got a big number just saying your not alone keep
testing
the way up to 50hz used 3 differant boxs still same added more power a bit better changed to 12s
got a big number just saying your not alone keep
testing
Try getting a few people to sit on your bootlid. That will stop the flex .
Although I gained .5-1dB by not having someone sit on my bootlid and letting it flex.
Although I gained .5-1dB by not having someone sit on my bootlid and letting it flex.
Bobic:
Yeah my tests revealed the same thing. Pushing down on the boot lid actually made it drop by 1dB.
Yeah my tests revealed the same thing. Pushing down on the boot lid actually made it drop by 1dB.
maybe try a new port ? ?
Well after I do all the other stuff I will porbably try new port settings. By then I will be desperate as f**k. I'll probably even try giving the exhaust a blow job to see if that helps, although that's probably going a bit far!
I'm also going to try adding another 2 subs! Hmmmm 4 12" 4Ohm subs running ~350WRMS each. I'll be pissed if I'm still getting 139dB.
I'm also going to try adding another 2 subs! Hmmmm 4 12" 4Ohm subs running ~350WRMS each. I'll be pissed if I'm still getting 139dB.
we run a vn commodore and run 146-147 all day on the normal mics
we have tried just about everything to get the best results
and have discovered the best formula for us
sealed box = rear loaded
ported box = fire forward
what subs are you running ?
we have tried just about everything to get the best results
and have discovered the best formula for us
sealed box = rear loaded
ported box = fire forward
what subs are you running ?
QUOTE
Originally posted by Roddas77:
Bobic:
Yeah my tests revealed the same thing. Pushing down on the boot lid actually made it drop by 1dB.
same for me at final battle! but wasn't a huge diff only like 0.2db higher without holding the bootlid... that was when I was rear-loading. firing forward is heaps louder in my car.
Bobic:
Yeah my tests revealed the same thing. Pushing down on the boot lid actually made it drop by 1dB.
When we have Test/tune next, mabey, cover over your ports, and find the resonant frequency of the car, then port 5-7db below that. Worth a try.
(ohhhh and once again i hit 139.x db, talk about consistancy 4meters all within 0.5db)
(ohhhh and once again i hit 139.x db, talk about consistancy 4meters all within 0.5db)
ur prolly hiting the limit or ur subs that is why i am wanting so desparatly to get bluedogs subs that will eb suicide to sit in
I'm definately not hitting the limit of the subs. They can do much more....
Walk:
Yeah I saw the other posting saying that you got 139dB. Bloomin consistent. Atleast you can tell us whether the mic is calibrated!
I'm gonna make a 4x12" sub box soon, so I might try sealed first and test it, then I'll port it and test it again, and see the difference. I tried sealing the ports of the old box and it resulted in a 2dB drop. Which is what I expected.
I think the peak of the car was about 54Hz, but I might need to try that again at full power and make certain, as I had most of the car in pieces when I was testing it.
Walk:
Yeah I saw the other posting saying that you got 139dB. Bloomin consistent. Atleast you can tell us whether the mic is calibrated!
I'm gonna make a 4x12" sub box soon, so I might try sealed first and test it, then I'll port it and test it again, and see the difference. I tried sealing the ports of the old box and it resulted in a 2dB drop. Which is what I expected.
I think the peak of the car was about 54Hz, but I might need to try that again at full power and make certain, as I had most of the car in pieces when I was testing it.
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