Driver w/Goofy Parameters. What to Build With It? - diyAudio
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Old 19th October 2006, 01:26 AM   #1
Ron101 is offline Ron101  Canada
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Default Driver w/Goofy Parameters. What to Build With It?

Hey all,

New to the speaker game. I have this Precision Power PC8 8" driver in one of the recommended size sealed enclosures (0.75 cu ft) but it doesnt sound very good; this is for a car stereo application. I did some basic research and d/l winISD to see what this driver was doing. T/S parameters are:

from: http://www.precisionpower.com/ppipdfs/subs/pc81011.pdf
Nominal Power Handling = 200W
Resonant Frequency = 35Hz
Qts = 0.25
Qms = 1.28
Qes = 0.32
Vas = 17.91L = 0.632 cuft
DC Resistance = 3.4 Ohm
Sensitivity 1W/1m = 85.7dB
Linear excursion = +/- 7.98mm
Mms - Total Mass = 59.98g
Sd - Piston Area = 0.0191 sq.m
Bi-Magnet Product = 11.83 TM
Mounting Dia. = 7.125"

Aiming for a Qtc of 0.707 winISD calculates a Vb=0.09 cu ft! Quite a bit different than the recommended sizes of 0.5, 0.75, and 1.0 cu ft.

So I read that lower Qts drivers are better suited to vented enclosures. For vented winISD calculates Vb=0.13 cu ft, tuning freq=57 Hz, but the port lengths are rediculously long (eg. 1.9m for a single 10cm diameter port).

So any suggestions what can be done with this driver for a more 'correct' enclosure or is best for a paper weight? Thanks in advance.
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Old 19th October 2006, 01:50 AM   #2
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Hi Ron,

How about this one?

http://www.billfitzmaurice.com/AutoTuba.html

Regards Philip
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Old 19th October 2006, 01:55 AM   #3
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Default remember cabin gain?

car subs take advantage of the impact that a small cabin has to offer. So with car subs You ought to run a design program to see what size box to use. If you don't have or want to run a simulation then use the largest volume recommended cabinet and then if you find you need a little more umph you can either fire the sub into a corner or just place the cabinet in the corner of your room with the longest diagonal dimension. Regards Moray James.
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Old 19th October 2006, 02:08 AM   #4
Volenti is offline Volenti  Australia
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Another option would be a Transmission line, I've been using TL's in cars for some time, your's I would put in a tube 8'' in dia by 45'' long, lightly stuffed along the whole length with polyester fill, you'll need to put mesh or a grille on the open end to stop the fill from coming out.

Position the tube at the far back of the car/trunk for best results.
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Old 19th October 2006, 02:55 PM   #5
Did it Himself
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If those parameters are right, a sealed box is useless and I find it hard how any manufacturer could even think about suggesting to use a sealed box. It's power handling will be poor and it will quite severely lack bass and punch. I would go vented, but with Qts that low it's never going to be a stormer.
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Old 19th October 2006, 03:18 PM   #6
Ron101 is offline Ron101  Canada
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Default Re: remember cabin gain?

Quote:
Originally posted by footstony
How about this one?

http://www.billfitzmaurice.com/AutoTuba.html

Regards Philip
Looks interesting but beyond my construction resources.

Quote:
Originally posted by moray james
car subs take advantage of the impact that a small cabin has to offer. So with car subs You ought to run a design program to see what size box to use. If you don't have or want to run a simulation then use the largest volume recommended cabinet and then if you find you need a little more umph you can either fire the sub into a corner or just place the cabinet in the corner of your room with the longest diagonal dimension. Regards Moray James.
Any details or links on how to go about running a simulation? Is it a strictly virtual exercise or does it involve measuring interior acoustics? Is there shareware software available?

Quote:
Originally posted by Volenti
Another option would be a Transmission line, I've been using TL's in cars for some time, your's I would put in a tube 8'' in dia by 45'' long, lightly stuffed along the whole length with polyester fill, you'll need to put mesh or a grille on the open end to stop the fill from coming out.
This looks like a doable project. What do you use for tube construction? Can you get away with ABS/PVC piping?

Thanks,
Ron
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Old 19th October 2006, 03:43 PM   #7
Ron101 is offline Ron101  Canada
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Quote:
Originally posted by richie00boy
If those parameters are right, a sealed box is useless and I find it hard how any manufacturer could even think about suggesting to use a sealed box. It's power handling will be poor and it will quite severely lack bass and punch. I would go vented, but with Qts that low it's never going to be a stormer.
Lack of punch is right; the sound is very squishy. Ironic that PPI is not exactly entry level gear.

I was going to try vented but I have no knowledge on how to get around the very long port length. Can it be snaked back and forth without drastically affecting the tuning?
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Old 19th October 2006, 03:45 PM   #8
sreten is offline sreten  United Kingdom
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Hi,

Seems like it has a dual voice coil ?
Qts can be varied at the cost of efficiency.

To port it you would need a passive radiator.

/sreten.
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Old 19th October 2006, 03:50 PM   #9
Volenti is offline Volenti  Australia
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Default Re: Re: remember cabin gain?

Quote:
Originally posted by Ron101



This looks like a doable project. What do you use for tube construction? Can you get away with ABS/PVC piping?

Thanks,
Ron
Yea most of the TL's I've done with 8'' drivers have used pvc pipe, sono tube (used in construction as moulds to make pillars out of concrete) works well too if you can get it, it's like a thick walled cardboard tube.

You don't need to use a tube though, I've made folded lines out of wood that work just as well.
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Old 19th October 2006, 03:52 PM   #10
Volenti is offline Volenti  Australia
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And the finished result;
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File Type: jpg tlbox3.jpg (42.0 KB, 121 views)
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