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Old 11th June 2007, 10:51 PM   #1
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Default Design Challenge #2

Design Challenge #2 from this rookie - I want to make a smaller sub for off-grid usage, so minimal power usage is important. I found an AudioFile Home Theater VRS 1205 Power output: 150Watts RMS at 4 ohm and at least 100W RMS at 8 ohm that fits the ticket as it uses a maximum of 2.5 ohms.
For the driver I'm looking at a single Apex Jr Super 8" Subwoofer:
FS=47.75Hz
Qms=7.334
Qes=.552
Qts=0.514
Vas=0.376 cu. ft.
Re=2.653 ohms
Le=0.157mH
Spl=85.22 @ 1w/1m
He recommends a .83f3 13"X13"X13" Ported Box With a 2"x6" Port.
The challenge: I want this to sound snappy, but I'm NOT trying to shake my teeth! 10" H is preferable, as is parallel in its vertical planes but revising the w & d is fine as is a specially tuned shape. I know nothing about engineering it; I just need to build it! THANKS!
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Old 11th June 2007, 11:24 PM   #2
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Default Re: Design Challenge #2

Quote:
Originally posted by kgillies
Design Challenge #2 from this rookie - I want to make a smaller sub for off-grid usage, so minimal power usage is important.
You will need an efficient amp.

Quote:
[i]I found an AudioFile Home Theater VRS 1205 Power output: 150Watts RMS at 4 ohm and at least 100W RMS at 8 ohm that fits the ticket as it uses a maximum of 2.5 ohms. [/B]
2.5 amps?

Quote:
[i]For the driver I'm looking at a single Apex Jr Super 8" Subwoofer:[/B]
Nice bass driver.

Quote:
[i]FS=47.75Hz[/B]
Rather high if you are looking for a "subwoofer"

Quote:
[i]Spl=85.22 @ 1w/1m[/B]
So so. Pretty standard for that size driver but not great considering it's Fs.

Quote:
[i]The challenge: I want this to sound snappy, but I'm NOT trying to shake my teeth! [/B]
This is a good all round driver. Not snappy like a PA driver though.

Quote:
[i]10" H is preferable, as is parallel in its vertical planes but revising the w & d is fine as is a specially tuned shape. I know nothing about engineering it; I just need to build it! THANKS! [/B]
I think you will be fine with changing the internal dimensions (to a point) provided the volume remains the same.
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Old 12th June 2007, 04:27 AM   #3
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Default Sealed vs. Ported

Aloha and thanks for the input. Yes, of course, 2.5 amps!

I forgot to ask, in the car audio world I prefer the sealed subs to ported as they sound tighter (not looking for deep thuds, just good clean lows). Is there any translation here to home audio? I seem to see everything ported. And I forgot to mention this will be built in, so front-firing is it on this.

My current sub (see Design Challenge #1) is a dual chambered affair - does any of that matter or is a single chamber box just as good for this situation.

Any recommendations of alternate drivers or configurations is welcome!
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Old 12th June 2007, 06:05 AM   #4
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I doubled up the ApexJr suggested design for a push-push woofer. It works well with 2 50W amps.

3rd one down

http://www.planet10-hifi.com/boxes-other.html

dave
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