4th order bandpass, wheel well design :) (design inside) - diyAudio
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Old 5th January 2008, 09:39 PM   #1
TWOJZ is offline TWOJZ  Australia
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Default 4th order bandpass, wheel well design :) (design inside)

going to attempt to make something like this.

its not drawn to scale, but it was rather difficult explaining to people what I wanted to make without having a pic.

so, there it is!

going to have a semi circle perspex window in the top, 4th order bandpass, using the spare tyre well, and the area available above it.

vented through the rear deck

basically no trunk space used!

anyone see any massive problems with the general design? lol, ofcouse, nothing is to scale, so volumes arent correct, that will all be worked out once I start building, or atleast after I measure the car

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Old 6th January 2008, 01:36 AM   #2
TWOJZ is offline TWOJZ  Australia
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hmm
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Old 6th January 2008, 04:38 AM   #3
ppia600 is offline ppia600  United States
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Looks like one I built, but mine wasn't in the wheel well. I actually built it against the rear seat but still in the trunk. It vented into the cabin and was VERY loud. I just didn't build the sealed side large enough and the response dropped off quickly under 40hz. The woofer I used was an early ImageDynamics IDQ 12. It was cool because there was absolutely no loss into the trunk and it didn't move the trunk lid at all. I say go for it, you'll definately need to do a lot of tuning but surely it will be fun. What size sub do you plan on using, an 8 maybe?
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Old 6th January 2008, 02:56 PM   #4
Eva is offline Eva  Spain
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Your port is way too narrow and long for proper front chamber tuning, it would only work as a rear port or as part of a conventional reflex enclosure. In practice you need a big front chamber (like 20 liter for a 12 inch driver) and a very short front port (a few cm long) with large surface (1/3 driver SD or better).

Consider a 6th order bandpass with a low Q rear chamber tuned low (36Hz), a high Q front chamber tuned high (95Hz) and a tilted downwards (6 to 12dB/oct) frequency response (that integrates very well with cabin gain and front speakers). While the proposed rear vent provides little improvement in output, it reduces cone excursion (and the resulting distortion) and improves power handling. As a result, efficient drivers (low Qts like 0.3) with moderate Xmax (+/-5mm) and clean midbass output are suitable for this arrangement.

Leading the ports to the cabin produces the best results, particularly for the front port, but since it must be short, it becomes a difficult chamber layout task.

Alternatively you can consider a tapped horn (take a look at the loudspeakers forum).
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Old 6th January 2008, 06:57 PM   #5
TWOJZ is offline TWOJZ  Australia
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^^

the proposed design has a 60 litre sealed chamber, 15litre ported chamber, tuned to 50Hz, with a 6inch diameter port, which needs to be 53 inches long.

the design was never drawn to scale, however, the area of the port is, but not the length.

sorry about the big graphs...

you really should all buy bigger monitors


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Old 7th January 2008, 02:53 AM   #6
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Default Re: 4th order bandpass, wheel well design :) (design inside)

Quote:
Originally posted by TWOJZ
going to attempt to make something like this.

its not drawn to scale, but it was rather difficult explaining to people what I wanted to make without having a pic.

so, there it is!

going to have a semi circle perspex window in the top, 4th order bandpass, using the spare tyre well, and the area available above it.

vented through the rear deck

basically no trunk space used!

anyone see any massive problems with the general design? lol, ofcouse, nothing is to scale, so volumes arent correct, that will all be worked out once I start building, or atleast after I measure the car

Click the image to open in full size.
Yes, I built one of these - almost identical to this, about fifteen years ago. It was louder than your average twin 8", but I think it was mainly attributed to the lack of energy spent rattling the trunk lid. Since it was so long ago...I don't remember what it sounded like. After all, it was one of dozens of "custom installs" our shop did at the time - every year. Can't keep them all straight...
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Old 7th January 2008, 04:45 AM   #7
ppia600 is offline ppia600  United States
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WOW, just noticed you have an mtx 9500 woofer in your calculations. That thing is a monster, you must have a huge well to put the box in.. Better use some thick mdf for sure
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Old 7th January 2008, 06:42 AM   #8
TWOJZ is offline TWOJZ  Australia
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just measured the space I was planning on using

seems I'd have to extend the box about 5cm higher than the spare tyre well to get the sub to fit sideways like that.

no big deal really
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Old 7th January 2008, 02:11 PM   #9
ppia600 is offline ppia600  United States
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You could also mount the sub at an angle.
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Old 7th January 2008, 06:37 PM   #10
TWOJZ is offline TWOJZ  Australia
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Quote:
Originally posted by ppia600
You could also mount the sub at an angle.

not really... although mounting it at an angle may reduce the height needed for mounting the basket, the basket will then stick up higher... if that makes sense?

http://www.mtx.com/caraudio/products..._slideshow.cfm
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