Hi everyone,
Would someone be kind enough to help me,
I am replacing the 8 inch drivers in my dynaudio profile 3 speakers ( Driver 21W54 ) with the SB23NRXS45-8
They mate to a Dynaudio D54AF dome midrange
The crossover network as all first order with the inductor to the bass driver 1.8 MH Crossover point 700 HZ
I obviously need to keep that inductor and crossover point for integration to the midrange.
The original bass driver had no cone breakup filter on it but my question is the new replacement SB23NRXS45-8 driver will .
The cone breakup un the graph looks to be between 1000HZ to 4000 HZ
Can someone please point me in the right direction to calculate a notch filter for this driver.
Regards
Would someone be kind enough to help me,
I am replacing the 8 inch drivers in my dynaudio profile 3 speakers ( Driver 21W54 ) with the SB23NRXS45-8
They mate to a Dynaudio D54AF dome midrange
The crossover network as all first order with the inductor to the bass driver 1.8 MH Crossover point 700 HZ
I obviously need to keep that inductor and crossover point for integration to the midrange.
The original bass driver had no cone breakup filter on it but my question is the new replacement SB23NRXS45-8 driver will .
The cone breakup un the graph looks to be between 1000HZ to 4000 HZ
Can someone please point me in the right direction to calculate a notch filter for this driver.
Regards
Hi AllenB,
Thanks for your response
I don't know how to do that.
I was just looking at the driver graph of the SB 23 and can see the cone breakup at 1000 hz and above,
As the crossover point has to be 700 hz with only a first order crossover i assume the cone breakup of this driver has to be greatly reduced
Thanks for your response
I don't know how to do that.
I was just looking at the driver graph of the SB 23 and can see the cone breakup at 1000 hz and above,
As the crossover point has to be 700 hz with only a first order crossover i assume the cone breakup of this driver has to be greatly reduced
Kind of. The peak is probably only on-axis and not representative of the whole picture.
Still, it's a start. If you'd like to post the response plots you have, and some idea of the existing crossover I'll run up some basic sims to get you started.
Still, it's a start. If you'd like to post the response plots you have, and some idea of the existing crossover I'll run up some basic sims to get you started.
Out of curiosity what happened to the 21W54s?
The 700 hz crossover may be low enough that the breakup of the new driver may not matter so much.
Have a mic good enough for measurements and a copy of REW?
You may be close enough with that driver.
Have a full schematic of the crossover? Mostly looking to see if the low pass has any sort of zobel or not.
The 700 hz crossover may be low enough that the breakup of the new driver may not matter so much.
Have a mic good enough for measurements and a copy of REW?
You may be close enough with that driver.
Have a full schematic of the crossover? Mostly looking to see if the low pass has any sort of zobel or not.
Hi. This reminds me of an exercise we worked on some time ago, where the frequency response of a known crossover was replicated with a substitute driver.
I did a quick and dirty from an old 21W54 datasheet and the SB23 datasheet.
This is roughly what the 1.8mh coil does to the 21W54 - very easy compared to modern drivers.
Editing for 8ohm version of SB23.
I did a quick and dirty from an old 21W54 datasheet and the SB23 datasheet.
This is roughly what the 1.8mh coil does to the 21W54 - very easy compared to modern drivers.
Editing for 8ohm version of SB23.
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That's a good comparison motokok. (Hoping the datasheets have also presented everything fairly.)
EDIT: Holding for the update.
EDIT: Holding for the update.
Sorry my internet went down.
Here's best I could do quickly with the SB23 8OHM. It is not as sensitive vs the Dynaudio and the 4ohm version. Can't do anything about that.
The cap and resistor both knock down the 1k spike as well as roughly tracking the original rolloff (navy colored line).
Maybe the Seas U22 would allow a closer 1st order rolloff, but hey.
Here's best I could do quickly with the SB23 8OHM. It is not as sensitive vs the Dynaudio and the 4ohm version. Can't do anything about that.
The cap and resistor both knock down the 1k spike as well as roughly tracking the original rolloff (navy colored line).
Maybe the Seas U22 would allow a closer 1st order rolloff, but hey.
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Hey Allen B and motokok, thanks for your response,
Yeap the old dyn 21w54 was obviously a very easy driver to rol of first order
that is why i think i need to to get rid of the upper end hash as a replacement driver
i will post the crossover schematic when i can ( please be patient with me i am working the next few days )
Yeap the old dyn 21w54 was obviously a very easy driver to rol of first order
that is why i think i need to to get rid of the upper end hash as a replacement driver
i will post the crossover schematic when i can ( please be patient with me i am working the next few days )
No problem. If you look at the top end (on the datasheet) you'll see that the general output of the driver is much less than the peaks on axis.
You'll also see it's pistonic below 1kHz, then it begins to narrow but is still well behaved until around 2kHz. Then it's time to bail out. This is common for 8" drivers.
You'll also see it's pistonic below 1kHz, then it begins to narrow but is still well behaved until around 2kHz. Then it's time to bail out. This is common for 8" drivers.
My guess would be the foam surrounds have gone to speaker heaven. I still have a few 30W54 lying around with that issue. Fixing it hardly is worth the trouble, since these drivers (the 21W54 also) have quite limited Xmax to modern standards. A pity for these are quite well engineered units otherwise.
If the foams were shot, then it would have made sense to glue new ones. Dust caps stay intact, anyway.
Hey Everyone ,
Thanks for your interest in helping me out !.
Yes you are right Lojzek the Midrange is the D52AF
I am trying to find the schematic from the original paperwork other than that i will draw it and then post
One of the the 21W54 Bass drivers has a scraping sound now which sounds like distortion when playing ( Id say voicecoil )
As they are nearly 30 years i have refoamed them twice
Thanks for your interest in helping me out !.
Yes you are right Lojzek the Midrange is the D52AF
I am trying to find the schematic from the original paperwork other than that i will draw it and then post
One of the the 21W54 Bass drivers has a scraping sound now which sounds like distortion when playing ( Id say voicecoil )
As they are nearly 30 years i have refoamed them twice
Have taken x over values and and posted it
As for the original Dynaudio 21w54 Bass driver,
one shows 5.5 ohm across the terminals and the other show's nothing ?
Hey Lojzek,
I never thought of rotating the driver
and i have now laminated a new 25 mm front baffle on the old one with the rebate for the SB23 woofer.
Hey motokok.
That simulation looks great
I have the 3.3 ohm resistor but would a 40 uf bennic cap be ok instead of the the 33 uf one you suggest as i have it on hand
As for the original Dynaudio 21w54 Bass driver,
one shows 5.5 ohm across the terminals and the other show's nothing ?
Hey Lojzek,
I never thought of rotating the driver
and i have now laminated a new 25 mm front baffle on the old one with the rebate for the SB23 woofer.
Hey motokok.
That simulation looks great
I have the 3.3 ohm resistor but would a 40 uf bennic cap be ok instead of the the 33 uf one you suggest as i have it on hand
