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traw 15th August 2006 03:31 AM

rational approach
 
Here's the story...

I know this is not the recommended starting point, use recommended or educated (via experience) matching, measure, work magic, etc.

Have 3 drivers i wish to use to make a speaker in similar physical format to spendor sp100's... 3 way, stand mounted. I have lspcad and soundeasy. Drivers: acoustic research 4ohm coated paper 10 inch, scan speak 8640 paper for for mid, and usher 9950 silk tweet. Problem is, can i make an educated guess on enclosure volume, assuming will just make a .25 cu ft or so sealed cavity for mid, tweet self enclosed into the woofer space and remainder space for woofer thus simplifying volume calc.

worried about baffle layout, but thinking have some play being mid-woof xover point gives some distance and will have mid tweet very close. also believe can make main cab and just heavily clamp baffle to box...

i need some instructions in a nutshell. really do not want to have to make test box for woofer ( i have no specs on it ) ... will impendence measurement on it be enough to start? then could make first attempt baffle, take measurements near field, drivers mounted in enclosure and work out initial xover with software?

aaaarrrrghhh... scrambling. just give me some basic steps. know once i get rolling in procedure will repeat and refine

thanks

Henckel 15th August 2006 06:47 AM

Closed box for bass:

- Estimate between 50-80 liters volumen - heavy stuffing as a starting point.

Bass reflex box for bass:

- You need to make an estimation on the thiele-small parameters of the bass unit. http://sound.westhost.com/tsp.htm is a good starting point. It might show that the bass unit is unfit for Bass reflex use though. in that case back to the closed box.



Build a test box with the needed volumen and intended baffel layout - mid and tweeter needs to be close together.

Measure( 1 meter) frequency and impedances of individual units in box.

Start simulating cross overs in LSPCAD et al.

build first prototype of crossover - measure listen - revise ( and on and on it goes)

Shaun 15th August 2006 07:39 AM

Hi traw
 
You don't have to use the test box method; try added mass (using coins or some other measured mass) to determine the T/S parameters. I guess if you're building it yourself you might as well invest some time in modelling the enclosure. The enclosure and driver work together to form a system. You must do this at least to determine the woofer's suitability for the intended purpose, else you could find yourself badly disappointed.


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