The SB26CDC seems very much alike the SB26ADC but the dome resonance appears easier - my mic was calibrated from 6hz to 20Khz but the Beyerdynamic factory supplied measurement seems good enough to try it above 20Khz
I compared it to the Transducer Lab N26CR2A and liked the Transducer lab better (waveguide requires lots of modification due to the screws and plate glued suspension they used in the TLabs so I gave up) - the SB26CDC sounds somewhat sterille compared to the Tlabs, although both can be used really low. Looking at the waveguide measured performance, I can easily use a 1.5Khz crossover with it but the midrange of the Revelator is good enough to blend them at 1.9Khz or around.I really want to test the whole project outdoors, hoping for some good weather. Problem is, these are really heavy and not easy to carry around as I went for highly polished polyurethane coating and not its slippy...
Last edited:
I don`t like to test this way, prefer to test the real thing. I got an interesting solution to the measurements problem - outdoors can be done easily using one of those gearbox hydraulic lifts used by repair shops - they lift up to 1.8m which is absolutely superb for any measurement - any standard woofer will be like 2.2-2.3m away of the ground and one of these lifts that can do 250kg costs just 120 eur! I my area about any repair shop offered ot lend me one for free when I told them what I need it for.
Soo, I got a new pair of L22rnx/p - so new spiders were still sticky. The chassis is slightly larger so will need ot rerout the already finished speaker but a plan is in place - high rpm laminate trimmer with a small 8mm double sided bit should do without chirps.
Soo, I got a new pair of L22rnx/p - so new spiders were still sticky. The chassis is slightly larger so will need ot rerout the already finished speaker but a plan is in place - high rpm laminate trimmer with a small 8mm double sided bit should do without chirps.
Today got to finally pulling the speaker out and running a set of measurements. Besides birds, it was pretty quiet. Speaker was lifted to 70cm above ground and could do down to 170Hz for the tweeter and midwoofer, the Seas L22 woofer had reflections so measurement was valid only from 550Hz above but I set it to 170Hz to compare to the rest. Its close to the ground by design and will require the speaker to be lifted much higher for proper results.
As I had issues with the Seas units supplied by Falcon Acoustics that had large deviation from the published parameters, I bought a new set of L22rnx/p from another vendor and got them installed. These were produced in the same month I bought them, according to the label. A quick sweep showed they`re as specified by manufacturer.
I think the more interesting part would be the SB26CDC tweeter which I put in a Monacor WG300 shallow waveguide. The tweeter in the waveguide has very low distortion, the lowest I have seen from a tweeter so far. I will use it with a crossover point of 1.9-2Khz. The waveguide does a great job at lifting the low end and looks like crossover will not be hard at all for the mid to tweeter blend.
As I had issues with the Seas units supplied by Falcon Acoustics that had large deviation from the published parameters, I bought a new set of L22rnx/p from another vendor and got them installed. These were produced in the same month I bought them, according to the label. A quick sweep showed they`re as specified by manufacturer.
I think the more interesting part would be the SB26CDC tweeter which I put in a Monacor WG300 shallow waveguide. The tweeter in the waveguide has very low distortion, the lowest I have seen from a tweeter so far. I will use it with a crossover point of 1.9-2Khz. The waveguide does a great job at lifting the low end and looks like crossover will not be hard at all for the mid to tweeter blend.
Attachments
The 18w4531g00 midwoofer used selaed here. There is no mistake, the tweeter is actually less sensitive than the woofer - a part of the design - so may go without a resistor.
Attachments
Last edited:
I accidentaly tried to load another file and lost the on-axis measurements yesterday...So had to remeasure and this time raised the speaker even more - to 1.2m above ground with the woofer effectively being somewhere at 1.7m or so. With the exception of a very annoying dog barking all day, I managed to find a few quiet windows and run new sweeps. The first reflection was so far away that gating went down to 70Hz so glad I deleted my measurements.
Tonight will start the crossover design to see what will come up.
Tonight will start the crossover design to see what will come up.
So, the beta of the crossover is done. I tried to go for a 2nd order LR but it just didn`t work as I wanted it to. So, final one will be 4th order LR between midwoofer and tweeter and 2nd order between woofer and midwoofer. The mid band from 1Khz to around 9Khz is slightly depressed in the expected system response. It was indeed easier to make the speaker flat so this depression took me a while to implement properly, but I`ve never enjoyed the somewhat more aggresive sound of horns (even if this one is shallow) so decided to voice the speaker this way. Making it flat requires minor changes so can be done later during the listening sessions. The impedance should be tube amp friendly.
A few photos of the crossover and the expected performance. Note, this is based on measurements taken with the speaker lifted in free space with gating set at 70Hz so response is close to anechoic. When inroom the low end below baffle step will be lifted.
A few photos of the crossover and the expected performance. Note, this is based on measurements taken with the speaker lifted in free space with gating set at 70Hz so response is close to anechoic. When inroom the low end below baffle step will be lifted.
Attachments
Last edited:
More baffle step compensation - crossover can be tweaked quite a lot without serious phase or response issues and without changes to most components. I will be placing these in the long end of a room with about 60cm to walls so may go for modest bsc.
Attachments
The woofer has a drop in response right there. The summed response is 2db higher and is very narrow. Besides, it is at 80Hz so not very audible (may indeed create a perception of higher dynamics). I am not concerned about excursion as the 18W has high linear displacement and here it is used as a midrange. In theory with this crossover it will not exceed its linear stroke with over 100W and I will use it with 50.
Yes, a coil will solve it, although pretty big value (6.2-6.8mH in the case)...Its optional
Here`s a slightly improved version of the crossover and with the 6.2mH coil. First two are as I intend to voice the speaker, second one is with more treble. Two values are changed only. Impedance goes slightly under 4 ohms at 2.2Khz but this should be no issue for any amp, phase is at -12.4 degrees so should be ok. I did try a trap for the slight bump at 12Khz but it drops impedance there to under 3.2 ohms and while high in frequency, I think this bump may add a bit of sparkle so left it to be the speaker`s character
Attachments
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.