In a 2-way, if you put XO right about where baffle step occurs, the BSC can be handled as a system rather than just trying to burn off the response in the tweeter or the woofer. In general, the woofer is the rate limiting driver and it will have typically -4dB to -5dB of bass falloff below the baffle step frequency (except for BLH and FLH where actual acoustic gain occurs in bass frequencies), all other alignments cannot have *true* sensitivity of the system any higher than woofer minus 5dB. Almost all commercial speakers lie about their sensitivity by quoting sensitivity at 1kHz or something. They should quote sensitivity at 100Hz if not 60Hz, where it matters and is rate limited. So for a bass driver with 89dB sensitivity, the overall system can be no higher than 85dB. You can see this with studio monitors from trusted brands where their monitors are rated typically 85dB maybe 86dB (and they have nice efficient 8in or 12 in woofers). Compare that to typical bass reflex HiFi speakers with ratings like 89dB or 92dB, or even an absurd 96dB, which is a bunch of hyperbole of course...
If the alignment is a BLH or even ML-TQWT, like a Karlsonator, there is actual acoustic gain in bass frequencies. Take for example, the 0.53x Karlsonator with dual 91dB 3FE35-16ohm drivers in parallel, it is a true 97dB sensitive 8-ohm speaker at 80Hz (as there is about 5dB of bass gain due to the speaker cabinet itself), no BSC circuit is used.
So having said that, the sensitivity of the 10F/RS225-8 is about 82dB at 60Hz. So we need to pad down the midtweet by about 5dB to 7 dB to get a balanced output. This is where a second woofer in a bipole can help to bring that -5dB loss back and overall system can then be 87dB.
If the alignment is a BLH or even ML-TQWT, like a Karlsonator, there is actual acoustic gain in bass frequencies. Take for example, the 0.53x Karlsonator with dual 91dB 3FE35-16ohm drivers in parallel, it is a true 97dB sensitive 8-ohm speaker at 80Hz (as there is about 5dB of bass gain due to the speaker cabinet itself), no BSC circuit is used.
So having said that, the sensitivity of the 10F/RS225-8 is about 82dB at 60Hz. So we need to pad down the midtweet by about 5dB to 7 dB to get a balanced output. This is where a second woofer in a bipole can help to bring that -5dB loss back and overall system can then be 87dB.
Last edited:
In a nutshell...Baffle step happens because the wavelength of lower frequencies is longer than the width of the baffle. Being so, some of the sound energy radiates to places other than toward the listener (the sides and back of the enclosure); therefore, some of the volume/loudness of the bass is lost. The high frequency has a shorter wave length, so it doesn't "wrap around" the enclosure. It radiates toward the listeners; therefore, doesn't lose any volume/loudness like the bass. An infinite baffle will not really have any baffle step issues.
Mike
BSC made simple (and why it may be important to you) – Audioblog
Loudspeaker Diffraction Loss and Baffle Step Compensation Circuits
10F/8424 & RS225-8 Transient Perfect XO
Here is the Xsim results using my measured FRD and ZMA files from early on this project. Nowadays, I would have used FDW gating of 6 cycles rather than the 1/12th octave smoothed data as shown here.
Here is the schematic (with 4.4uF & 0.47R filter added for woofer):
Here is the predicted frequency response & phase, it would appear that the XO frequency is visually somewhere closer to 800Hz:
Here is the predicted impedance:
Here is the predicted step response:
Here is the predicted square wave at 1kHz:
The Xsim project file is attached as a zip file.
Here is the Xsim results using my measured FRD and ZMA files from early on this project. Nowadays, I would have used FDW gating of 6 cycles rather than the 1/12th octave smoothed data as shown here.
Here is the schematic (with 4.4uF & 0.47R filter added for woofer):
Here is the predicted frequency response & phase, it would appear that the XO frequency is visually somewhere closer to 800Hz:
Here is the predicted impedance:
Here is the predicted step response:
Here is the predicted square wave at 1kHz:
The Xsim project file is attached as a zip file.
Attachments
Last edited:
How about these graphs X : ) its still a 1st order XO and still 10F and AC130 can sit its own small enclosure with mid tweeter below woofer and then place SB23 on floor.
In theory think many improvements will happen, one is break up areas for AC130 and SB23 is relative better depressed, one is 10F/AC130/SB23 all show their own good distortion figures and smooth response inside these bandwidths, one is with these less driver diameter steps off axis coherency should be better covered between bands.
Target curve verse 10F datasheet:
Target curve verse AC130 datasheet:
Target curve verse SB23 datasheet:
System sum 50Hz-18kHz band pass (transient perfect):
In theory think many improvements will happen, one is break up areas for AC130 and SB23 is relative better depressed, one is 10F/AC130/SB23 all show their own good distortion figures and smooth response inside these bandwidths, one is with these less driver diameter steps off axis coherency should be better covered between bands.
Target curve verse 10F datasheet:
Target curve verse AC130 datasheet:
Target curve verse SB23 datasheet:
System sum 50Hz-18kHz band pass (transient perfect):
Attachments
I looked up the SB23, and was pleasantly surprised they share a lot of TS params with my TB drivers... and then Vas, impedance curve, and a couple of others looked totally different. Too bad.
In the mean time, I've been looking around, and it looks like some have taken your idea of salvaging inductors. I think I will go dumpster truck diving soon!
In the mean time, I've been looking around, and it looks like some have taken your idea of salvaging inductors. I think I will go dumpster truck diving soon!
Attachments
The SB23 is a really low distortion driver - perhaps one of the best I have seen when it comes to sealed woofers. The measurements from Bushmeister’s speaker were amazing. Anyhow, it deserves a box to be made around it. I think with a 24L box it will get about 50Hz and with low distortion.
A Bookshelf Multi-Way Point-Source Horn
This is with two SB23’s in a Pointsource Bookshelf Horn but at 50Hz and 100dB 1m, it was like almost -50dB THD.
A Bookshelf Multi-Way Point-Source Horn
This is with two SB23’s in a Pointsource Bookshelf Horn but at 50Hz and 100dB 1m, it was like almost -50dB THD.
Last edited:
