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Home audio sub using 18" passive
Home audio sub using 18" passive
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Old 16th September 2005, 08:40 PM   #1
eRiCdWoNg is offline eRiCdWoNg  United States
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Default Home audio sub using 18" passive

...I have a rather heavy sub I used to use in my car, but it was too heavy. It it this one: a 15" thats essentially a Kove Audio Z15D car audio sub. I got it from parts express, I will post a link when their site works again. Its a great sub but its just too darn heavy so I took it out of the car. Soooooo... here comes my next wild idea. I've never used a passive radiator before and would like to try. I know not many manufacturers make 18" PR's but I found this one:

http://yellow.mynethost.com/~bv12636...bb16566df0dbf0

Its not terribly expensive and I don't care how large of a box I would need to use, but the tunability with weights and no port noise and low end response of a PR is appealing. The next question is I have no idea how to begin designing one of these except the passive should be larger then the active. I'd use this for home theater where ultra low infrasonics will be required.

The woofer has a good amount of excursion and power handling although its Fs is a little high, probably because it is a car audio sub. Can I touch the 20's maybe teens in FR?
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Old 16th September 2005, 09:02 PM   #2
LineSource is offline LineSource  United States
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I think the most common solution is to build a small sealed, well braced, box and use equalization like a Linkwitz transform circuit to get low freq bass extension at the cost of much higher power(watts).

The math says you can only have two of these three features.

1) low frequency bass
2) low power (efficiency)
3) small cabinet


If you want a small cabinet and low frequency, you will need high power amplifier and equalization.
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Old 16th September 2005, 10:06 PM   #3
bigwill is offline bigwill  United Kingdom
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I'll pick 1 & 3 then
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Old 16th September 2005, 10:24 PM   #4
eRiCdWoNg is offline eRiCdWoNg  United States
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Thanks for the response, but I dont think I will be going sealed on this design. Ive done sealed boxes before and want to try a passive radiator. Since I am shooting for low bass, I think it will be better then a port which would loose control of the woofer below its resonate freq.

I want low frequency bass no matter what the cost (almost). I have a Crown MacroTech 5000VZ as a bass amp (5000 watts continuous, 4 ohms bridged) so power is not a problem. I also have a graphic and parametric EQ's to use if needed. Box size, I don't care if it is the size of a refridgerator, if thats what it takes. So small size does not matter either. Any tips on calculating the box size/weights to use on the PR?
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Old 17th September 2005, 12:10 AM   #5
95Honda is offline 95Honda  United States
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Figure on 2x the driver displacement for passive radiator displacement.

If you don't care about box size, then you could build a port big enough to not worry about any noise......
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Old 17th September 2005, 12:57 AM   #6
simon5 is offline simon5  Canada
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You should order your passive radiator from Acoustic Vision website, someone heard that Acoustic Elegance is mostly stalled right now.

It's the same one and it's in stock.
http://www.acoustic-visions.com/~aco...s/stryke_pr18/

To find the correct box size, you could download WinISD Pro or Unibox and find by yourself.
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Old 18th September 2005, 06:17 AM   #7
Ron E is offline Ron E  United States
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Quote:
Originally posted by eRiCdWoNg
...I... want to try a passive radiator. Since I am shooting for low bass, I think it will be better then a port which would loose control of the woofer below its resonate freq.

Any tips on calculating the box size/weights to use on the PR?
PR's unload below tuning the same as a port. Depending on size not quite to the extent, but very near so. It is fine to want to try something new, but PR's are not much different from ports excepting the ease with which they may tune a mall box to a low frequency. If you want something that protects the driver at low frequencies, try a 4th order bandpass.

To design a PR box, simply design with a ported box calculator. Find out how long a port must be that is the same diameter as the PR piston. Calculate the volume of the port, then the mass of the air in a cylinder the length of the port plus approx 0,75 times diameter of port. Subtract this value from the PR stock mass and that is the amount of mass you must add.
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Old 18th September 2005, 07:05 AM   #8
kelticwizard is offline kelticwizard  United States
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Home audio sub using 18" passive
You can download Subwoofer Simulator and find the mass which needs to be added to the passive radiator, (Drone Cone).

Or you can give us the Thiele-Small parameters of the subwoof you are referring to and we can make recommendations.
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Old 18th September 2005, 05:36 PM   #9
eRiCdWoNg is offline eRiCdWoNg  United States
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Thanks for the replys guys. This is the woofer, now the PE page is working again:

http://www.partsexpress.com/pe/showd...number=299-665

An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.


Specifications: *Power handling: 1050 watts RMS *VCdia: 3" *Le: 2.8 mH *Nominal impedance: 4 ohms per coil *Re: 3.0 ohms per coil *Frequency response: 20-250 Hz. *Magnet weight: 192 oz. *Fs: 37 Hz *SPL: 90 dB 2.83V/1m *Vas: 2.63 cu. ft. *Qes: 0.53 *Qts: 0.48 *Xmax: 20mm *Manufacturer model number: Z15D *Dimensions: Overall Diameter: 15-1/2", Cutout Diameter: 13-7/8", Mounting Depth: 7-1/2", Magnet Diameter: 7-3/4", Magnet Height: 3"
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Old 22nd September 2005, 05:13 AM   #10
tade is offline tade  United States
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have you purchased that sub yet? i was curious as to its performance.
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