hello , im puzzled by the freq response of my dual 6" bass drivers , wired in parallel , 3 way foorstander ( SD Acoustics 'SD5' , from 2001 )
drivers unknown, no labels , but seem to be giving an incredible in room response of +/- 1db 30-1khz, which seems bizarre ( well that seems incredible to me )
basically, im trying to lower the crossover point to 200hz , but i can not get the woofer to stop outputting , its pretty flat to 1khz ( I used a textbook filter of 6.7mh + 100uF 2nd order ) ....those values should produce approx a 200hz crossover with 4ohms
the drivers have combined DCR of 3.3R , plus 0.8R inductor DCR
please see the graphs , one taken 10cm away, with the above filter applied ( both 1/48 smoothing)
other graph is with no filter , taken 40cm away
- I dont understand how 6.7mH + 100uF can produce a crossover point at 1khz?
drivers unknown, no labels , but seem to be giving an incredible in room response of +/- 1db 30-1khz, which seems bizarre ( well that seems incredible to me )
basically, im trying to lower the crossover point to 200hz , but i can not get the woofer to stop outputting , its pretty flat to 1khz ( I used a textbook filter of 6.7mh + 100uF 2nd order ) ....those values should produce approx a 200hz crossover with 4ohms
the drivers have combined DCR of 3.3R , plus 0.8R inductor DCR
please see the graphs , one taken 10cm away, with the above filter applied ( both 1/48 smoothing)
other graph is with no filter , taken 40cm away
- I dont understand how 6.7mH + 100uF can produce a crossover point at 1khz?
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waterfall ( with filter ) ;
how am i able to get these woofers to crossover at 200hz?
PS: the original woofer xover used is 4.3mH + 60uF , which was giving a xover point of 800hz.... the midrange uses no xover, SD Acoustics call it ' semi active design ' (!) .... the midrange is flat to 200hz , so I dont understand why they crossed the bass at 800hz ?
my plan is to add a band-pass filter to the mid >200hz <3.5khz
the cabinets are made from a gravity cast resin , so are not wood, and are and heavy ( 32kg )
how am i able to get these woofers to crossover at 200hz?
PS: the original woofer xover used is 4.3mH + 60uF , which was giving a xover point of 800hz.... the midrange uses no xover, SD Acoustics call it ' semi active design ' (!) .... the midrange is flat to 200hz , so I dont understand why they crossed the bass at 800hz ?
my plan is to add a band-pass filter to the mid >200hz <3.5khz
the cabinets are made from a gravity cast resin , so are not wood, and are and heavy ( 32kg )
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I remember when Steve Deckert published similar results for his fullrange on open baffle. Too flat to believe. After few month of internet arguing he discovered his measuring mistake. How embarasing. His ob speaker had flatter response than original driver manufacturer.
thanks... ive disabled all audio card inputs on the PC , which REW recommend to avoid a feedback loop
i took a measurement with the mic disconnected ( but USB interface still connected ) , see graph. the 50hz spike must the the UK mains frequency.... im guessing the high freq. noise is electrical noise from the PC itself and/or USB interface
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Hi buganna, sorry for delay, forum was upgrading. Yes, your measurement looks realistic now. Are you using calibrated mic? Your scale looks suspicious. Are you truly measuring at 105dB? That seems loud. Normally i target 80-90dB.
What are you trying to achieve? Optimize crossover?
What are you trying to achieve? Optimize crossover?