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Old 7th February 2007, 11:59 AM   #1
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Default Linkwitz sub

Hi

I have a Beyma G550 18" woofer and I plan to build a subwooferwith it using either a Linkwitz transform or EAS controller from sound.westhost.com (project 48) in a 60 - 80 liter cabinet and a 600 watt d-class amplifier.

Now is this a good idea or .. ?

I aim for a response from 80 to 20 hz hz flat.

Any sugesstions something I should be carefull with?

best regards

Heinz
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Old 7th February 2007, 12:05 PM   #2
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Sounds OK initially with the limited information provided. Just keep Xmax and voicecoil power handling in check, also watch how much gain you need to hit your target F3.

Also bear in mind your room construction may mean that you don't need a flat response all the way down - room gain may give you some natural boost.
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Old 7th February 2007, 12:14 PM   #3
Dag is offline Dag  Sweden
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Sounds like a VERY fun idea.....if you don't have (or want to get rid of) your neighbours

I think flat down to 20Hz is a bit too much because roomgain will give up to 10dB(???) gain at 20Hz. I have heard people say that f=30Hz and Q~0.6 is a good choise for the Linkwitz transform. But it is of cource depending on the room and personal preferences.

Have fun!!
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Old 7th February 2007, 01:16 PM   #4
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Hi
some additional information

Sd for the woofer is 1200 cm2

Continious power handling 750 watt

Xmax (linear) = +/- 7 mm

Xdamage = 40 mm

And I don't have any neighbours.

thanks for the responses so far
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Old 7th February 2007, 01:25 PM   #5
sek is offline sek  Germany
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Hello Heinz,

I have an 18G50 in 35l. I'm currently working on the Linkwitz transform PCB. Power will be delivered by a UCD module.

Fun to see that I'm not the only one who is crazy enough to try this (after the consensus for such projects is 10" cone diameter).

Things to look for: cone stiffness, enclosure stiffness and enclosure sealing. In that order. Because a tight enclosure doesn't help you with a ripped up cone!

Project 48 is essentially a hefty EQ which you would have to adjust accordingly as good as it gets, while a Linkwitz transform circuit does apply a correction on the driver's transfer function. It can be calculated and simulated (preferrably with driver measurement response data in it's final enclosure). I prefer Linkwitz's solution - well designed it performs as good as the driver can and keeps it safe, at least according to the simulation.

Will you be able to do measurements?

Cheers,
Sebastian.

PS: Those parameters are alike for nearly all Beyma 18" drivers. So it's enclosure volume and driver resonance frequency in-box that determine the response (and the difference between our projects).
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Old 1st October 2007, 01:55 PM   #6
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boompity bump
would like to hear how this project went so far?
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Old 1st October 2007, 06:12 PM   #7
mikee55 is offline mikee55  United Kingdom
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Default I got a 12" on LT

Hi all,

Quote:
I think flat down to 20Hz is a bit too much because roomgain will give up to 10dB(???) gain at 20Hz.
I'm @20hz, and I think its ok! Even room gain isn't a problem. My sub is close to a corner, but doesn't boom. Then again, I have an undersized amp. Music is helped immensley an I watched Robocop last night, do I need to say more. I was expecting loads of neighbourupsetting LF's but was greeted with a more realistic rendition of a footstep of the ED209 droid's foot coming down on the office floor of OCP and then gun fire ringing(!!) out nicely, even explosions could just be felt, but heard through my mains.
Listening done 10'o'clock at night with the kids in bed, even WAF approved, she was suprised and the first to moan if I start booming

Mike
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Old 1st October 2007, 07:09 PM   #8
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hi

I'm sorry to say that the project is on hold.

No funds.

Insted I mounted the Beyma in a 160 l basreflex cabinet made out of some fiberboard I had laying around.

I only have an old cheap Monacor Carstereo amp with aprox. 100 watt in 8 ohm to drive it.

Still plenty of bas and better than I thought
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