sub sound output explanation
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=96179
Printed Date: May 01, 2024 at 1:54 AM
Topic: sub sound output explanation
Posted By: tdsteele
Subject: sub sound output explanation
Date Posted: August 05, 2007 at 4:38 PM
Ok, so I have been working on a friends 2000 Chevy truck, full size standard cab, and I built and installed an enclosure for a single 10" Diamond CM3 sub, which sits between/ behind the 2 seats with the sub basically positioned over the center console, so its right next to your head. It is powered by a JBL CS 300.1 amp, 400rms @ 2 ohms. So, we started with the enclosure sealed, .75 ft^3, and while waiting for the JBL amp he had the sub powered by an old Pioneer 2 channel that put out like 75 watts, and sounded pretty good, just not very loud. So, we got the JBL amp in and installed and the sub was alot louder, but sounded like it was distorting real bad when we really cranked it up, so I decided to port it since I have better luck with ported boxes anyways. So, got it ported and back in and better, but still some distortion. So i'm getting frustrated at this point and then the weird thing happens, he opens the door to get out and bam, this sub is pounding and sounding great! So, the sub doesn't sound worth a crap with doors closed and windows up, but open up both windows and the thing sounds awesome, why is that? Is it the fact that the trucks cab is too small for this sub to perform well? First time I have experienced this so looking for information as to whats going on. Thanks guys.
Replies:
Posted By: cutlass013
Date Posted: August 06, 2007 at 2:21 AM
not really sure but i tend to have the oppisite with ym setip with the trunk on my car down it sounds great but with it open sounds kind of sad
Posted By: pendulum
Date Posted: August 06, 2007 at 4:52 PM
I have heard something about tuning to the wavelength of the vehicle or something. I do know that in my Camry when I had my 10, it did sound better with the windows down. In my first car, two 12's, sounded better with everything closed/rolled up.
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1999 Toyota Camry
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Pioneer DEH-P3700MP
Lightning Audio Strike S4.15.VC2
Lightning Audio Strike S4.500.1
Majestic 6.5"
Posted By: tdsteele
Date Posted: August 08, 2007 at 8:49 PM
So, any ideas on this? Has to be a common occurrence I would think.
Posted By: dwarren
Date Posted: August 09, 2007 at 12:04 AM
I'd guess you are getting some sort of cancellation, I'd try reversing the polarity of the sub. Either that, or the sub has some terrible motor noise. One thing that bothers me, is that a box with an internal volume of .75cu. ft. can be so easily changed to a ported version? Sounds a little fishy...How about that gain and bass boost... -------------
Posted By: Flakman
Date Posted: August 09, 2007 at 12:09 AM
I agree with dwarren. Cancellation is probably what is going on. Try moving the box to different spots in the back. Having it centered may be causing some of the cancellation. Also check the gains and boost if it is truly distortion.
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The Flakman
I feel strange. I have deja vu and amnesia at the same time.
John | Manteca, CA
Posted By: tdsteele
Date Posted: August 09, 2007 at 6:11 AM
I will try reversing the wires tomorrow when I see him again, see what that does. As far as the box size, per Diamond, sealed boxes .5 to 1.0 ft^3, ported .75 ft^3, so based on that, I built it with porting in mind. And with this vehicle, there is no moving the box around to different positions, it is the way it is because there absolutely no room behind the seats.
Posted By: haemphyst
Date Posted: August 09, 2007 at 7:59 AM
Is the .75 cu ft you have provided gross (box volume ONLY) or net (box volume, plus vent, plus woofer, plus bracing)?
What I mean is this: If your woofer displaces .1 cu ft, (typical) and your vent displaces .2 cu ft (again, typical, for a deep tuning), and your bracing displaces .2 cu ft (hopefully AT LEAST that much...), did you add those, for a NET box volume of 1.25 cu ft, or did you build your box to .75 cubes, and then stuff everything into THAT volume...
If you stuffed everything into .75, you're working with a volume that is FAR too small to be vented. Now, this isn't an answer to your question, but it IS an issue.
As to your answer, I can't tell you, but it most likely has something to do with the transfer function of the cab. In my car, my bass drops off DRAMATICALLY when I close the windows, but with them open, I get deep, tight, LOUD... I don't hear "distortion" as you say, but there is a noticeable difference in response, open vice closed I'll ask someone I know if they might have an idea...
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: tdsteele
Date Posted: August 10, 2007 at 8:57 PM
The .75 is the net volume. I had built the box with the idea that if we didn't like the sealed, we could port it and be at the recommended size. I had meant to swap the wires around today at work, but never got time to so, maybe in a couple of days when i see him again I can try that.
Posted By: tdsteele
Date Posted: August 16, 2007 at 8:24 AM
So a little update, plus still looking for answers. I reversed the wires, no change at all, we laid the box on its side so the sub was facing the back of the lower passenger seat, seemed to make it hit lower and clearer, but still not near as loud than when we opened the doors. So, still at a loss here. Thinking about asking Diamond if they have any recommendations.
Posted By: ophidia31
Date Posted: August 16, 2007 at 11:01 AM
do you have the rear of the enclosure almost butt up against the back of the cab? you could be gettng cancellation issues and when you open the window/door it gives those waves somewhere to go besides the front wave of the subwoofer. it sounds like what was going on in my old setup. i had my sub forward facing in a sealed enclosure, behind the fold down seat. sounded like ass until i opened the trunk to give the rear waves somewhere to go instead of being out of phase with the fronts from the reflection off the back of the trunk lid. moving it further back up against back of the trunk yeilded better results. since that wasnt what i wanted, i had to seal the front of the sub almost 90% from the trunk area to get what i wanted. now i know what some of you might say that there are no rear waves when a sub is in n enclosure, but just through my experimentation with that setup led me to believe otherwise. i dont have any scientific backup from test equipment like alot of guys might have and just use my ears, but thats what i found out. but, pretty much any vehicle is going to have louder bass from their subwoofer systems with any sort of window open or vent in the cabin area.
Posted By: tdsteele
Date Posted: August 16, 2007 at 4:29 PM
Yes the enclosure is flush with the back of the cab, in this truck there is NO choice on that. It is a standard cab, absolutely no room to work with.
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