In my very limited experience the amount of BSC required with narrow baffles is rather substantial (I'm using more than 5dB) and the insertion loss of the BSC network at frequencies below the shelf is largely a function of the dcr of the choke used and the zobel network required due to the VC inductance and may be less than a couple of dB with care. Implementing BSC at line level does have the advantage of not requiring a zobel network across the driver which may contribute positively on the efficiency front.
What I am trying to say is that the required boost on the low end may eat more of the available power than anything else, and is in a region where the power is required - even line level BSC is not going to help a lot here..
There is no question that a good passive speaker level BSC network will cost a lot more than a passive line level device which would consist of just a couple of resistors and a cap. Speaker level requires a high quality choke, two power resistors and a good capacitor.
I used a passive BSC because I wanted a speaker that was reasonably flat in any situation and have no way of knowing in every situation what the source impedance of the pre-amplifier and input impedance of the power amplifier will be as these speakers will be used with other hobbyists designs in addition to my own.
I will probably design a simple passive line level BSC network for use with my electronics and these speakers - mainly because I am curious now..
With appropriate quality components either approach will work fine, however the line level device should be considerably less expensive to implement properly.
What I am trying to say is that the required boost on the low end may eat more of the available power than anything else, and is in a region where the power is required - even line level BSC is not going to help a lot here..
There is no question that a good passive speaker level BSC network will cost a lot more than a passive line level device which would consist of just a couple of resistors and a cap. Speaker level requires a high quality choke, two power resistors and a good capacitor.
I used a passive BSC because I wanted a speaker that was reasonably flat in any situation and have no way of knowing in every situation what the source impedance of the pre-amplifier and input impedance of the power amplifier will be as these speakers will be used with other hobbyists designs in addition to my own.
I will probably design a simple passive line level BSC network for use with my electronics and these speakers - mainly because I am curious now..
With appropriate quality components either approach will work fine, however the line level device should be considerably less expensive to implement properly.
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croat47> Not to sound ungrateful but I don't quite see the relevance with that link?
I have a line-level bsc allready and knows how to build a speaker level one if I wanted to.
My problem lies with impedance matchings.
If I have a... let's say 50ohm cdp output, bsc with 10kohm in/2.5kohm ut it's a rotten match with a 10kohm passive attenuator (LDR).
Put the bsc after the LDR and we get something like 5-10kohm out (LDR) vs 10kohm in (bsc).
Also a very poor match.
I haven't found a way to get it working propery without a buffer?
I have a line-level bsc allready and knows how to build a speaker level one if I wanted to.
My problem lies with impedance matchings.
If I have a... let's say 50ohm cdp output, bsc with 10kohm in/2.5kohm ut it's a rotten match with a 10kohm passive attenuator (LDR).
Put the bsc after the LDR and we get something like 5-10kohm out (LDR) vs 10kohm in (bsc).
Also a very poor match.
I haven't found a way to get it working propery without a buffer?
Aaron probably meant to grab the link from the next article down... Passive Line Level Baffle Diffraction Step Compensation
If you don't have the the impedance matches a buffer is a good solution.
We did a PLLXO with buffers at either end that worked quite well.
dave
That was actually a VERY good link for me. The bsc as such is no news to me since my existing bsc design looks exactly like it.
However in the comments he mentions that R1||R2 must be twice of Rsource, R1+R2 must be half of Rload and C1 must be 10 times greater than Cload.
Reading this opens up a new world for me. I could use a 750ohm R1&R2 and a 1uF C1 and still get away wth using a passive pre.
If the information in the article is correct...
This would just blow my previous issues right out of the water. All problems solved and the hero rides into the sunset... errr or something.
Sure it's a big and expensive cap but it's still doable and since it's not in the direct signal path it shouldn't be to bad on sound quality.
P.S.
I'm thinking a 7-10kohm passive attenuator as a pre. I'm guessing but 100ohms sounds like a fairly typical value for a cdp out?
Putting the bsc somewhere in the middle shouldn't be too hard.
However in the comments he mentions that R1||R2 must be twice of Rsource, R1+R2 must be half of Rload and C1 must be 10 times greater than Cload.
Reading this opens up a new world for me. I could use a 750ohm R1&R2 and a 1uF C1 and still get away wth using a passive pre.
If the information in the article is correct...
This would just blow my previous issues right out of the water. All problems solved and the hero rides into the sunset... errr or something.
Sure it's a big and expensive cap but it's still doable and since it's not in the direct signal path it shouldn't be to bad on sound quality.
P.S.
I'm thinking a 7-10kohm passive attenuator as a pre. I'm guessing but 100ohms sounds like a fairly typical value for a cdp out?
Putting the bsc somewhere in the middle shouldn't be too hard.
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Yeah, a 10kohm pot and a 100ohm source would give me 1:5 ratios all around if I opted for 1kohm resistors and a 0.75uF cap.
I'm happy.
Please say it'll work?
Should do... i got away with 5:1 on my last PLLXO
dave
I tried Rod Elliots variable Line level BSC: Baffle Step Compensation
can't say I liked it. I know it's not an option for you FR guys, but I then went 1st order PLLXO biamped, and use level adjustment to get my BSC.
can't say I liked it. I know it's not an option for you FR guys, but I then went 1st order PLLXO biamped, and use level adjustment to get my BSC.
Do you have a suggestion that would improve the circuit? Maybe experimenting with multiple capacitor values?
No filter will take into account the complexities of the baffle diffraction... unless it is applied to a very well behaved shape you will have ripple. (sphere or "teardrop")
The pot allows you to dial in the amount of cut for your room.
The F3 he uses is the standard value used for F3, a number literaly pulled from drawing a few lines on the charts from Olson research. This number is always a ballpark, and will need to be adjusted based on cabinet shape.
dave
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