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1 PIs in 9ltr sealed box ?? [message #39334]

Wed, 04 December 2002 10:14

Scholl
Messages: 67
Registered: May 2009

Viscount

I'm thinking over a sat\sub system for HT mains and suround and the 1 PIs in 9ltr closed boxes look good for a Q of +-1 115hz F3. Has anyone built anything close?

How are the mid\highs on the Alpha 8s? New data sheets show a rise before rolloff. Is there a crossover on the 1s to smooth this?

this might make for a nice punchy little box.

Thanks, Scott

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Run 'em ported [message #39335 is a reply to message #39334]

Wed, 04 December 2002 12:18

Wayne Parham
Messages: 18836
Registered: January 2001

Illuminati (33rd Degree)

You could certainly run an Alpha 8 sealed, but as you've indicated, f3 would be pretty high at over 100Hz. The little one π's are ruler-flat for an octave lower in a 1ft3 bass-reflex box tuned to 60Hz. So in my opinion, there's no reason to use this speaker in a sealed box unless it is intended to be used as a midrange driver. As a midwoofer, I prefer to implement it in a bass-reflex configuration. It's bass is smooth, midrange is clear and all that's required for crossover is a 0.5mH coil to counter a slight bit of rising response.

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Re: Run 'em ported [message #39337 is a reply to message #39335]

Wed, 04 December 2002 12:50

Scholl
Messages: 67
Registered: May 2009

Viscount

Thanks, for the quick reply.

The intent of the design is to be used with a subwoofer with no crossover on the Alpha 8. A closed box reduces cone motion below rolloff and provides a nice rolloff. The box volume is chosen due to a nice available box from Madisound.

Thanks again

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My 2 cents... [message #39340 is a reply to message #39334]

Wed, 04 December 2002 14:11

mollecon
Messages: 203
Registered: May 2009

Master

It does look to me that 9 ltr's is a bit on the small size for this unit, even for a closed box. I say that based on the Thiele-Small parameters given for the Alpha 8's. I'd rather go for a box about twice as big, ~20 ltr's. But of course I can see the temptation of using an available & ready-to-use enclosure. I'm just afraid the sound will be a bit on the boomy side in the upper bass area, since the Qb will be well above 1... This might be faught with suitable damping of the box, though.

And as you say - it will be a nice little kick-ass satellite!

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Re: Run 'em ported [message #39342 is a reply to message #39337]

Wed, 04 December 2002 14:16

Wayne Parham
Messages: 18836
Registered: January 2001

Illuminati (33rd Degree)

Sounds reasonable. Keep us posted and let us know how they turn out.

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Re: My 2 cents... [message #39351 is a reply to message #39340]

Thu, 05 December 2002 04:07

Scholl
Messages: 67
Registered: May 2009

Viscount

I don't think the Q will be much above 1, I'd actually like a Q of 1.1 for max power and a small peak to help offset baffle step.

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You're right... [message #39361 is a reply to message #39351]

Thu, 05 December 2002 12:58

mollecon
Messages: 203
Registered: May 2009

Master

The Qbox will be more like 0.85-0.9 I think & the Fres at ~115-120Hz (as you mentioned) - should give a -3dB point at ~105-110Hz. Seems to be fine for a satellite speaker.

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