The affect on bass response by the loading caused by the vehicle
Hi all,
I'm trying to get a more precise understanding of how much of an affect a vehicle plays in figuring the bass response you'd get from an enclosure in it. Is there a general 'rule of thumb' of how much gain centered at what frequency can be expected? I would imagine it would be different in a small car vs a truck with woofers in the bed with a connected camper shell. Anyone have any data/experience with this. Its awesome when it works in your favor but its a PIA when it works against you.
Hi all,
I'm trying to get a more precise understanding of how much of an affect a vehicle plays in figuring the bass response you'd get from an enclosure in it. Is there a general 'rule of thumb' of how much gain centered at what frequency can be expected? I would imagine it would be different in a small car vs a truck with woofers in the bed with a connected camper shell. Anyone have any data/experience with this. Its awesome when it works in your favor but its a PIA when it works against you.
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In a large vehicle interior location is key. I can tell you that sub placement in a van is more critical than I thought. I have two 15" subwoofers in a 4.5 cf enclosure @800 watts per and assumed that at this power level it really wouldn't make much difference where they were placed. I was wrong, its actually very much the same as dialing in the perfect sub location in a typical room in your house.
Placed in the center of the van, I get almost nothing out of them. Might as well have two 10's @100 watts because thats what they sound like in that location. Did some research and the consensus was that subs only work efficiently in a large empty van when placed at the rear, within one foot of a wall.
This is because a 40hz tone has a wavelength of 28 feet. The average compact car has a (roughly) 12 foot long by 3 foot tall interior if we include the trunk. A small vehicle like that exhibits greater cabin gain. Frequencies below approx 80 - 90hz in this space will have greater amplitude due to cabin gain aka transfer function. 12db gain per octave is the number I've read and that seems about right based on what I've seen on my various installs.
Moving the subs to the rear in my van results in >12db gain at all frequencies under 90hz measured with my old cheap Realistic SPL meter. Frequencies under 40hz gain closer to 15db.
I can fire them at the back doors from about one foot away or fire them upwards with box placed as far back as it goes. Either orientation produces the same db levels but firing backwards is louder outside the van vs. upwards which produces slightly cleaner/tighter bass.
Placed in the center of the van, I get almost nothing out of them. Might as well have two 10's @100 watts because thats what they sound like in that location. Did some research and the consensus was that subs only work efficiently in a large empty van when placed at the rear, within one foot of a wall.
This is because a 40hz tone has a wavelength of 28 feet. The average compact car has a (roughly) 12 foot long by 3 foot tall interior if we include the trunk. A small vehicle like that exhibits greater cabin gain. Frequencies below approx 80 - 90hz in this space will have greater amplitude due to cabin gain aka transfer function. 12db gain per octave is the number I've read and that seems about right based on what I've seen on my various installs.
Moving the subs to the rear in my van results in >12db gain at all frequencies under 90hz measured with my old cheap Realistic SPL meter. Frequencies under 40hz gain closer to 15db.
I can fire them at the back doors from about one foot away or fire them upwards with box placed as far back as it goes. Either orientation produces the same db levels but firing backwards is louder outside the van vs. upwards which produces slightly cleaner/tighter bass.
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Thanks. Strangely enough this is something I've never taken the time to measure. I've taken the 'Build it and they will come' approach in the past. I'm trying to actually plan it this time.
Any links to good reads are welcome. Thanks.
Any links to good reads are welcome. Thanks.
Meant to add:
A small(er) cabin space creates high cabin gain due to the fact that low frequency waves build up in a small space rather than simply dissipating as they do in a large auditorium.
A small(er) cabin space creates high cabin gain due to the fact that low frequency waves build up in a small space rather than simply dissipating as they do in a large auditorium.
No problem, personally I find it very interesting to test various speakers in different enclosures and different locations as the results are sometimes quite surprising.
Not sure if this forum allows links to other forums, so I won't. But a quick google search for "cabin gain transfer function" will give you some additional info.
Hi baronw'
I definitely can confirm your statement. Like you, I'm using quite a bit of hardware regarding the sub-woofer system in my suv; 4) JL 10's (partitioned) in a 3.5 cf sealed box and two JL HD-750 mono-blocks... 2-10's per amp. I have the box anchored (strapped) directly behind the second row seat, dead center; two drivers face the back, and two face upwards: http://www.diyaudio.com/forums/attachment.php?attachmentid=405771&stc=1&d=1394765072
One day just out of curiosity, I moved the box to the left rear corner hoping to capitalize on some "corner load" gain, as well as some extra space in the cargo area. To my surprise, not only did I lose some low-end with this experiment, I lost an AUDIBLE TON of of sub-bass from the system! I couldn't believe how drastically just moving the box a couple of inches affected the sound; it was like (no exaggeration) losing three of the four 10's, or 10db's of cabin gain, that's HUGE!
Needless to say, I quickly moved everything back to the way it was... "before my brainstorm!"
rigtec, cheers
Hi rigtec,
Wow, that sounds like a pretty dramatic difference! I can believe it based on the experiments I've done.
I would have assumed the same as you since corner loading a subwoofer is usually is good for at least 3db gain. But the bigger the interior volume, the trickier the speaker placement seems to be. The interior volume of my van is 280 cubic feet. Really, the only typical "car stereo trick" I've been able to use in this install is mounting tweeters in dash and bouncing high frequencies off the windshield. Everything else I know about car stereo speaker installation just doesn't seem to work the same way in this van. If your SUV is fairly big I would assume you are facing similar challenges.
I have my two 15" subwoofers all the way back against the rear doors as I've described, then over the rear axle I have a bank of four 8" mid-bass support in individual custom enclosures firing forward. I designed them using an online speaker enclosure calculator over the winter and just finished building/carpeting them.
Interesting part - and pertinent to this thread topic - is that the mid-bass speakers sound best in the center of van.
I intend to add two (or maybe four) more but first I need to build two 5 cubic foot boxes for my subs so thats my next project. They aren't performing at their optimal level in the pre-built (Atrend B-box). Bbox's aren't terrible, they are good enough to run tests with and perfect for temporary installs. But in the end I feel its always worth whatever time and effort it takes to design and build a box that properly matches your drivers, whatever they may be.
Thank you for sharing the results of your test.
Wow, that sounds like a pretty dramatic difference! I can believe it based on the experiments I've done.
I would have assumed the same as you since corner loading a subwoofer is usually is good for at least 3db gain. But the bigger the interior volume, the trickier the speaker placement seems to be. The interior volume of my van is 280 cubic feet. Really, the only typical "car stereo trick" I've been able to use in this install is mounting tweeters in dash and bouncing high frequencies off the windshield. Everything else I know about car stereo speaker installation just doesn't seem to work the same way in this van. If your SUV is fairly big I would assume you are facing similar challenges.
I have my two 15" subwoofers all the way back against the rear doors as I've described, then over the rear axle I have a bank of four 8" mid-bass support in individual custom enclosures firing forward. I designed them using an online speaker enclosure calculator over the winter and just finished building/carpeting them.
Interesting part - and pertinent to this thread topic - is that the mid-bass speakers sound best in the center of van.
I intend to add two (or maybe four) more but first I need to build two 5 cubic foot boxes for my subs so thats my next project. They aren't performing at their optimal level in the pre-built (Atrend B-box). Bbox's aren't terrible, they are good enough to run tests with and perfect for temporary installs. But in the end I feel its always worth whatever time and effort it takes to design and build a box that properly matches your drivers, whatever they may be.
Thank you for sharing the results of your test.
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Hi baronw,
Absolutely! As I know you know, "Timing is everything"! I think by me moving the sub such a small amount and getting the huge reaction that I did, any gain that might have been achieved by corner loading, was more than lost due to some phase anomalies created by poor positioning. Problem w/this application is, there is no formula (that I know of), for calculating soundwave phase time/alignment in a 180 cf arena. When on a stage in a large concert hall, the do's and don'ts of good low frequency sound management and control do apply. But in the truck, the low frequency wavefront is so large (by comparison), that some of those rules 'regarding distance', are no longer relevant, and positioning becomes ultra critical right down to the sq ft.
How far down do you want to drive the two 15's? Ten cf is a considerable net for these two drivers, and w/1.6kw rms behind them, you can move A LOT of air!!! 😉
rigtec, best to you.
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hello again rigtec,
Exactly. Working in these spaces is kindof a black art: sometimes speakers work exactly as predicted and other times they don't work at all 🙂
I appreciate your interest in my next project so I will created a new thread for that, I'd prefer to keep this thread from sliding off-topic.
Exactly. Working in these spaces is kindof a black art: sometimes speakers work exactly as predicted and other times they don't work at all 🙂
I appreciate your interest in my next project so I will created a new thread for that, I'd prefer to keep this thread from sliding off-topic.
Jon Whitledge (whitledgedesigns.com) did an excellent job on examining low frequency reproduction in a large (Sprinter van) vehicle interior using a scientific methodology.
Best and easiest way to figure out a good placement is to put the bass-enclosure (Box) on your driverseat and find a spot by your ears where the best response is. Than just change location. 😀
Soon I hope
I am very interested in 'sub-woofer design theory' in all aspects. I also have questions regarding just why increasing the net volume of my sealed 4x10 sub, doesn't result in lower f3/Fb; at least according to winISD. I'll be sure to chime in when you post your next project!
Greg, (rigtec) Best!
What if you put the box in the driver's seat and it sounds best in the driver's seat?
You just plan on knocking a big hole in the roof, and affixing 'LARGE BLOCKS' to the gas and brake pedals... Problem solved hahahahehe!
Soon I hope
I am very interested in 'sub-woofer design theory' in all aspects. I also have questions regarding just why increasing the net volume of my sealed 4x10 sub, doesn't result in lower f3/Fb; at least according to winISD. I'll be sure to chime in when you post your next project!
Greg, (rigtec) Best!
Thanks, and me too. Lots of experience with car audio but the more projects I actually finish, the more complex my next questions become. I'm used to building test enclosures and then dialing things in from there. I did track down and install winISD on the windows box but havent gotten around to figuring out how to use it.
http://www.diyaudio.com/forums/car-audio/252875-enclosure-design-mofo152x.html
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