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Building Keyboard Amp - Questions

Posted by RBS (P) on January 11, 2007 at 12:09:44

Hi all,

I got back into gigging recently. Play keyboards – piano and organ clone rig. Sometimes bass. Rock/jazz/blues for fun mostly. Went looking for a keyboard amp and guess what. Most are crap. Underpowered and expensive too. There’s plenty of great guitar and bass rigs but the offerings for keyboard just didn’t sound that good to my ear. So I’m thinking of building my own setup that should sound better than any commercially available amp. The setup would consist of a rack mixer and power amp with two speaker boxes. My idea is like a hi-end Roland jazz chorus amp. However I’d like to make two boxes – each with a 12” woofer and tweeter. That way I can elect to take one or both depending on the gig/rehearsal. Box size will be around 1.5-2.5 sq ft. I’d like to use neo magnet drivers to keep weight down (not getting any younger). I’ve looked at Bill Fitzmaurice’s dr horns and while they would be the ultimate solution, I don’t have the time nor woodworking skills to construct them. So it’s direct radiators in either closed or vented boxes.

Driver candidates:

Eminence Beta 12 http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-408
Eminence Delta 12 http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-414
Eminence Delta 12LFA http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-416
Eminence Deltalite 12 http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-593
B&cC 12HPL76 neo 12 http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=294-680

I’m leaning toward the B&C because of its smoother mid response ( the deltalite and most of the eminence drivers have a pretty big peak around 2K which might be fine for a bass and guitar but might make keys sound honky). The Eminence Beta and Delta drivers are lower cost solutions and may be more appropriate if the neo drivers are overkill for this application. On paper the B&C response is flatter in the mids and seems to be a beautifully constructed driver.

Can’t decide on closed or vented. I played around with winisd and it seems that a closed box will help limit cone excursion which may help power handling. Sometimes I may play electric bass through this system so don’t know if that becomes a factor for choosing closed or vented.

I’ll use a piezo tweeter for the top end for simplicities sake. Don’t want to get into horns and compression drivers with crossovers. Not sure what tweeter to use though. There seems to be a lot of 99 cent piezo available but I’m sure that they don’t have the power handling for gigs. Can you guys recommend a piezo for this aplication. Whatever thoughts or opinions you all have on this project is greatly appreciated.

Thanks in advance and ready to spin up the table saw,

Bob

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