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Old 20th July 2015, 12:24 PM   #1
oculi is offline oculi  Australia
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Default Too small sealed box, driver size. doing it properly now

Quick dumb question, I think it is more relevant to Subwoofers than car audio, at least academically so that's why i've posted the question here and not there.

If I was to build a sealed subwoofer box small enough to fit under, oh I don't know a seat in a car, would I get better low frequency performance using a 10" woofer or an 8" woofer?

I think the easy thing to do is buy an 8" woofer, buy a 10" woofer, make two boxes as big as I can, stuff them, then try both. the winner can go in my car, the loser can go in my wife's car.

Last edited by oculi; 15th January 2016 at 02:10 PM.
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Old 20th July 2015, 12:46 PM   #2
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It's a question that unfortunately the answer to is "it depends". It all comes down to the parameters of the drivers that are available to you.

It is possible - choosing the best mix of parameters - to get a box that the 10 inch performs better than some other 8 inch driver. But equally it is possible for an 8 to outperform a 10. Very generally speaking, it will take a more expensive driver to outperform as the suspension will need to cope with extra travel and the voicecoil will need to cope with more power.
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Old 21st July 2015, 04:14 PM   #3
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Your way to go is measuring the internals for your targets enclosures and go from there. After that you have the problem of what driver to get or buy in your country Australia.
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Old 6th October 2015, 04:53 AM   #4
oculi is offline oculi  Australia
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ended up building these, bought some 8" sherwood carbon fibre woofers off ebay as cheap speakers arent common in AU that do a pretty good fullrange impersonation. boxes are 9mm MDF (i hate MDF) as it was free, light and will give (marginally) more internal volume. had to rear mount the drivers due to space restrictions.

the boxes are wedge shaped as they had to go behind the seats, not enough room under them (they are in a small pickup truck)

bit too much midrange now so i'm kludging a low pass filter, the inductors I need cost about as much as the drivers did so i'm using some out of an off the shelf crossover, will add capacitor/s too.

Last edited by oculi; 6th October 2015 at 04:57 AM.
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Old 6th October 2015, 11:20 AM   #5
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Get a used car amp with low pass filter built in. Probably cost about the same as the inductors but far better results.
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Old 6th October 2015, 01:22 PM   #6
oculi is offline oculi  Australia
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Originally Posted by richie00boy View Post
Get a used car amp with low pass filter built in. Probably cost about the same as the inductors but far better results.
I've got a spare I've been testing various crossover configurations with, it has a LP filter which confirms you are right, don't want to use it unless I have to as I can't be bothered running the power/ground/RCA cables for it and it runs the portable sound system for my projector.

I think i'll get there with the inductors I have and the capacitors that are on the way.
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Old 25th December 2015, 04:30 AM   #7
oculi is offline oculi  Australia
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Default i have no idea what i'm doing.jpg

bit of an update, have been running two of these in my small pickup, in general they sound "bad" and surprisingly don't go much lower than the 4" coaxials in the dash.

did a bit of tinkering today, first of all I holesawed a hole in the baffle of one, sounded marginally louder but definitely lost bass, then liberated that driver from the box and kludged an isobaric enclosure with the other one. Definitely has more low frequency response but still sounds bad.

might see if I can make another box to go with the isobaric theme, but space is pretty limited. might try building a box with the 10" sub out of my harman kardon HT sub that blew up its plate amp.

and a photo of my handiwork so far for anyone's amusement, rear mounting the loudspeakers had predictable consequences.

Click the image to open in full size.
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Old 25th December 2015, 05:48 AM   #8
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In order to produce satisfying bass from a small cabinet you will need a driver with more motor strength .... You can derive motor strength figures by comparing the "BL factor" to the "Re" (voicecoil DCR), the formula is BL^2/RE , these numbers (BL and Re) should be provided by the manufacturer of any decent speaker .... If these parameters are not listed or not made available by the manufacturer then it is probably not a very good speaker , at least not good enough for critical applications such as this ....


Your best bet is too explore the options in "shallow mount" subwoofers for car audio ..... Some car audio subs are made specifically with "small box" parameters (strong motor and tight suspension) , because a small box is precisely what you are trying to accomplish here ...


as an example (even though these aren't all made specifically for car audio) : Dayton Audio LS10-44 10" Low Profile Subwoofer Dual 4 Ohm

or

http://www.parts-express.com/tang-ba...8-ohm--264-955

or

http://www.sonicelectronix.com/item_...-REF1000S.html

or

http://www.sonicelectronix.com/item_...-R2SD4-10.html

Last edited by Matthew Morgan J; 25th December 2015 at 06:15 AM.
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Old 7th January 2016, 08:49 AM   #9
oculi is offline oculi  Australia
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Quote:
Originally Posted by Matthew Morgan J View Post
In order to produce satisfying bass from a small cabinet you will need a driver with more motor strength .... You can derive motor strength figures by comparing the "BL factor" to the "Re" (voicecoil DCR), the formula is BL^2/RE , these numbers (BL and Re) should be provided by the manufacturer of any decent speaker .... If these parameters are not listed or not made available by the manufacturer then it is probably not a very good speaker , at least not good enough for critical applications such as this ....


Your best bet is too explore the options in "shallow mount" subwoofers for car audio ..... Some car audio subs are made specifically with "small box" parameters (strong motor and tight suspension) , because a small box is precisely what you are trying to accomplish here ...


as an example (even though these aren't all made specifically for car audio) : Dayton Audio LS10-44 10" Low Profile Subwoofer Dual 4 Ohm

or

Tang Band W8-2022 8" RBM Subwoofer 8 Ohm

or

Infinity REF1000S 800W 10" Reference Series Shallow Mount Single Voice Coil Selectable Smart Impedance Car Subwoofer

or

Rockford Fosgate R2SD4-10 10" Shallow Prime Stage 2 Subwoofer
Thanks for that, the tang band looks great, oddly lowish power rating though.

keeping with the low budget theme I tried fitting a 10" sub from a ported HT sub I had lying around (amp blew up long ago) but it was too big to fit behind the seat.

I bought one of these via ebay as it was cheap and should just fit (Fusion isn't exactly a well regarded brand in Australia but I was going to buy a generic sub anyway) which was $40 AUD 10? Subwoofer (EN-SW101) | FUSION Entertainment

they recommend 15 litres for a sealed box, which should be doable, have roughed out a design but won't do more until it arrives as they don't have a drawing for it.

Last edited by oculi; 7th January 2016 at 08:52 AM.
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Old 8th January 2016, 08:13 PM   #10
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by oculi;... $40 AUD [url=http://www.fusionentertainment.com/car/products/subwoofer-encounter/en-sw101
10? Subwoofer (EN-SW101) | FUSION Entertainment[/url]

they recommend 15 litres for a sealed box, which should be doable, have roughed out a design but won't do more until it arrives as they don't have a drawing for it.
Hi oculi,

Have a look at my of Sims and Calculations:

b

PS: The 15 Liter Sealed Box needs an Amp. with a built in PEQ.
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File Type: jpg Fusion Electronics EN-SW101.JPG (785.4 KB, 186 views)
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