How to Use a Linkwitz (1 Viewer)

[JimRHIT]

Ok, I have read(and got really excited) about the BP1803, and keep seeing everyone say that it would be great sealed with Linkwitz....and I have no idea what that exactly mean

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Questions:
- how does one use this method?
- how does one accquire one of these(what do they look like)?
- how much power would be required to drive this sub?
- how large of a box is needed?
Sorry for not being up to date, but I am new to this, so someday I will repay the favor to someone...just need to learn from you gentlemen first.
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Jim Walter
- my system -
Marantz SR7000
Sansui QRX9001
Klipsch Reference
Rectilinear III(ancient)
Velodyne VA810

 

[Brian Bunge]

Jim,
It's a Linkwitz Transform Circuit. It allows you to put the driver in a relatively small enclosure and "transform" the response to whatever you'd like it to be. For instance, I'm looking at an 1803 in a 5ft^3 enclosure (including stuffing) that will end up with an Fb of 18Hz and a Qtc of .5. The Fb before the transform is around 46Hz and a Qtc around .6.
You have to either use the Marchand BASSIS unit (around $400 complete or $250 for the kit), or you can build a specific circuit for less than $20 (that's my guesstimate). It's basically an opamp with a few resistors, capacitors, and a power supply. I'm looking at about 2000 watts for my alignment. The smaller the enclosure the more power required. I had looked at a 2.5ft^3 enclosure but I think this was going to require over 3000 watts.
Here's a link for more information.
http://sound.westhost.com/project71.htm
Jack will be along with the link for the spreadsheet!
Brian
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[Edited last by Brian Bunge on November 06, 2001 at 09:18 PM]

 

[Jack Gilvey]

http://www.pvconsultants.com/audio/utility/downloadlt.htm
S'more links:
http://sound.westhost.com/linkwitz-transform.htm
http://www.trueaudio.com/st_lkxfm.htm

 

[Brian Bunge]

Damn, that JG guy sure is punctual!

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[JimRHIT]

Thanks so much for everything guys. I know that it isnt easy to sit and retype what you told someone two weeks before, but I want you to know that I appeciate it. I found a lot of stuff in the archives here on HTF and I am really impressed with this idea. One problem, I only have about 400wRMS to throw at it.
My options are to either sell my Tempest to a friend(actually trade for another NAD 216THX amp, or to EBAY it and see what kind of pro amp I could get).
I know it says I will need a lot of power, so I think that the two NAD's would be enough....right?
Thanks again, James J Walter

 

[Brian Bunge]

James,
Since the 1803 is a single VC driver you can't use two separate amps to power it. In order to truly find out how much power you need you'd have to at least decide on an initial enclosure size, tuning frequency (I guess that's correct even though we're talking a sealed enclosure) and a Qtc. I think even Jack's proposed 7ft^3 enclosure was going to require in the neighborhood of 1500 watts.
Otherwise, you're looking at a big ported enclosure for the 1803. I believe a 14ft^3 tuned to 18Hz will rock your world with about 1000 watts.
If neither of these works for you then I think dual Tempest enclosures would be the way to go.
Brian

 

[Jack Gilvey]

Anytime, Jim. I'm not familiar with those amps, but that spreadsheet will give you an idea of the power required based on the driver, box size, and frequency response you want. Remember, the bigger the box, the less power you'll need, as you'll see in the sheet.
FYI, I just got an e-mail from American Musical Supply with some great closeout deals on the QSC RMX series amps, some real steals here:
http://www.americanmusical.com/AMSNwsltr.asp