Bravo! I wish I had some of your skills to tame my B&W 685s. I think they have a very similar tweeter to CM9. I also want to lower the crossover frequency from 4kHz to somewhere between 2.5 and 3 kHz. Is it safe to run those tweeters that low with second or third order crossover?
I also want to check the lining of the back wall as I suspect there could be backward reflection adding to some sort of lower midrange confusion, sort of reverberation roughly speaking. I also feel a cup-like coloration. Can you share some details of the lining material and the modified xover?
Another reason I want to go lower is to escape more from the controlled breakup zone of the mid-bass unit.
The 685s have very simple first order crossover with a simple capacitor and inductor. What's the order of the original CM9 crossover?
I attach what Dirac+UMIK measured far-field. Besides the room augmenting bass, there is a bulge from 700 - 1500 Hz followed by a dip at around 3kHz.
Attachments
Here are the schematics for the original and modified CM9 crossovers. Tweeter at the top, woofers at the bottom.
The modifications are implemented in a way that permits easy removal. I was originally going to make one concession and solder-in the C5 caps but access to the crossover board is quite awkward when it is in the enclosure. I didn't want to remove the boards so I soldered a couple of big alligator clips to each C5 and clipped it across C1.
Not quite mil standard construction, but they haven't fallen off yet.
The other four components (R5, L5, C6 and C7) are mounted on a small piece of 1/4" ply located inside the midrange chamber. Faston connector tabs are used for the board inputs and flying leads and Faston connectors for the outputs. The existing speaker leads connect to the board and the flying leads to the drivers.
Original:
Modified:
The modifications are implemented in a way that permits easy removal. I was originally going to make one concession and solder-in the C5 caps but access to the crossover board is quite awkward when it is in the enclosure. I didn't want to remove the boards so I soldered a couple of big alligator clips to each C5 and clipped it across C1.
Not quite mil standard construction, but they haven't fallen off yet.The other four components (R5, L5, C6 and C7) are mounted on a small piece of 1/4" ply located inside the midrange chamber. Faston connector tabs are used for the board inputs and flying leads and Faston connectors for the outputs. The existing speaker leads connect to the board and the flying leads to the drivers.
Original:
Modified:
Thanks. First order networks are hard on tweeters because of the slow roll-off. The B&W tweeters seem to be designed accordingly. The CM9 tweeter has a compliant suspension and a resonance around 650 Hz; by conventional wisdom they should be OK above about 1.5 kHz. At 1.5 kHz the tweeter input level is 10 dB lower with the third order 3 kHz network than with the original first order ~5 kHz network.
I used R6.7 Ultratouch insulation for damping. Very effective and nicer to work with than fiberglass. I have not had much luck with polyester batting, which is what the CM9 mid chamber was lined with.
The CM9 uses a third-order network for the woofers, a second-order bandpass for the mid and a first-order for the tweeter. The bandpass network has a phase response that approximately matches that of a third-order low-pass or high-pass, which is why the first-order tweeter network is not a good match.
Now that is interesting. Here's hoping they manage to keep the moving mass of the driver low and the sensitivity high. Either that or they can beef up the motor some
CM9 tweeter responses at 1m. Top to bottom: on axis, 15 degrees off horizontally, 30 degrees off. On axis, the bump centered on 1800 Hz and the dip centered on 3 kHz are due to baffle edge diffraction. So is the dip at 6 kHz in the 30-degree response. Sample rate was 44100, hence the 20 kHz limit.
ZMA and FRD files are here. Phase is measured with the peak of the impulse response centered on zero time. The average file is the average of the 0, 15 and 30 degree responses. Levels are arbitrary.
Last edited:
800 series reborn (or should that be reloaded, with those matrix enclosures)
Redefining the Legend: 800 Series Diamond - Bowers & Wilkins
Some of the changes include a new FST mid, new bass drivers, and a new cast aluminium head.
However, it's still the same basic 3 way passive design so the changes are most likely driven by the marketing department.
Redefining the Legend: 800 Series Diamond - Bowers & Wilkins
Some of the changes include a new FST mid, new bass drivers, and a new cast aluminium head.
However, it's still the same basic 3 way passive design so the changes are most likely driven by the marketing department.
What’s wrong with having a 3 passive way? It doesn’t have to be active to be revolutionary nor to reach the pinnacle of performance IMHO.
Example: Nautilus is active but the same designer of nautilus and the N800 speaker who moved away from B&W, designed a new speaker line which is the continuation of the Nautilus and it is supposed to surpass it, decided to go down the passive way and he is not driven by marketing (which is the reason why he left B&W about 10 years ago).
Having active crossover forces the user to have more than one amplifier, thus raising the final bill to a higher amount (more amps, more cables, more stands, more space, active crossover), and most people who do this will likely use smaller amplifiers as opposed to a single big amp like most do for passive solution.
In my opinion a bigger amplifier will do better than more smaller for the same total power provided the quality of the bigger one equals the smaller ones as it is capable of delivering it’s max target power in case the woofer would need it.
Nevertheless I guess there are, as always, pro and cons with both solutions!
Regarding B&W I would be curious to take a listen to it! I feel they went down the commercial route with the last models. In the past days I directly compared N805 and Diamond 805 on A/B tests on different setups for the kick and the results were impressively in favor of the cheaper and older N805 on each and every setup I tried it.
So they hopefully have changed route with this new series because B&W is a great brand and I would hate to see it going lower and lower with the quality of their products. If the new 800 is great I might consider upgrading in the near future (it is supposed to cost around 30K for what I have seen)
Example: Nautilus is active but the same designer of nautilus and the N800 speaker who moved away from B&W, designed a new speaker line which is the continuation of the Nautilus and it is supposed to surpass it, decided to go down the passive way and he is not driven by marketing (which is the reason why he left B&W about 10 years ago).
Having active crossover forces the user to have more than one amplifier, thus raising the final bill to a higher amount (more amps, more cables, more stands, more space, active crossover), and most people who do this will likely use smaller amplifiers as opposed to a single big amp like most do for passive solution.
In my opinion a bigger amplifier will do better than more smaller for the same total power provided the quality of the bigger one equals the smaller ones as it is capable of delivering it’s max target power in case the woofer would need it.
Nevertheless I guess there are, as always, pro and cons with both solutions!
Regarding B&W I would be curious to take a listen to it! I feel they went down the commercial route with the last models. In the past days I directly compared N805 and Diamond 805 on A/B tests on different setups for the kick and the results were impressively in favor of the cheaper and older N805 on each and every setup I tried it.
So they hopefully have changed route with this new series because B&W is a great brand and I would hate to see it going lower and lower with the quality of their products. If the new 800 is great I might consider upgrading in the near future (it is supposed to cost around 30K for what I have seen)
I agree, there's nothing wrong with the 3 way driver array, I was simply pointing out that the new range appears to be a refashioned version of the series it replaces rather than a revolutionary or paradigm shift.
The diamond tweeter is unchanged but there's now a new FST mid driver, which is a woven fibre, apparently similar to kevlar, but not kevlar, and performance is apparently improved with the first break-up mode now well above the designed pass band.
However, looking at the pics I can see that the tweeter is still set well forward like its predecessor, so there's a fair chance that the crossover is exactly the same design. If that's the case it should sound very similar to the existing series, but time will tell. I'll audition them at the local dealer next month when they arrive.
The diamond tweeter is unchanged but there's now a new FST mid driver, which is a woven fibre, apparently similar to kevlar, but not kevlar, and performance is apparently improved with the first break-up mode now well above the designed pass band.
However, looking at the pics I can see that the tweeter is still set well forward like its predecessor, so there's a fair chance that the crossover is exactly the same design. If that's the case it should sound very similar to the existing series, but time will tell. I'll audition them at the local dealer next month when they arrive.
Interesting. I cannot see if they've changed the xover frequency at all, but I am guessing not, it's B&W they cross things over too high, why should that change.
Either way, regardless of the simplistic xover approach that B&W have taken in the past the biggest issue with the 800 series has been the uneven frequency response created by the breakup of the FST. If they have indeed solved this with a new cone material (it really looks like fibreglass to me) then good on them, it was about time they did something about it.
How well it behaves is still yet to be seen, but this is B&W and in another sense their level of engineering and attention to detail is first rate. I would doubt that they would change the midrange driver unless it really did fix the issues with the original Kevlar cone.
There is nothing inherently wrong with passive three ways and the hifi industry will keep going down this route for as long as they can. Just because audiophile companies don't go this route does not mean it's not preferred where absolute performance is required, it's just the way things are.
Either way, regardless of the simplistic xover approach that B&W have taken in the past the biggest issue with the 800 series has been the uneven frequency response created by the breakup of the FST. If they have indeed solved this with a new cone material (it really looks like fibreglass to me
) then good on them, it was about time they did something about it. How well it behaves is still yet to be seen, but this is B&W and in another sense their level of engineering and attention to detail is first rate. I would doubt that they would change the midrange driver unless it really did fix the issues with the original Kevlar cone.
There is nothing inherently wrong with passive three ways and the hifi industry will keep going down this route for as long as they can. Just because audiophile companies don't go this route does not mean it's not preferred where absolute performance is required, it's just the way things are.
As previously discussed, the kevlar breakup issue could easily be resolved by moving the crossover frequency down to 2.5kHz, which is more ideal anyway for a 6 inch did driver, but that would require 3rd or 4th order HP for the tweeters.
Whether the new FST trades some performance advantages for others remains to be seen of course, but if the press hype is to be believed they're on a winner.
I'm also curious to know whether the tweeter crossover design has been enhanced to mitigate the effects of using mechanical alignment instead of reversing the tweeter polarity, as this is the primary cause of the S shape in the response through the crossover region in the D1&2 series.
A future Stereophile review will hopefully provide some insights.
Whether the new FST trades some performance advantages for others remains to be seen of course, but if the press hype is to be believed they're on a winner.
I'm also curious to know whether the tweeter crossover design has been enhanced to mitigate the effects of using mechanical alignment instead of reversing the tweeter polarity, as this is the primary cause of the S shape in the response through the crossover region in the D1&2 series.
A future Stereophile review will hopefully provide some insights.
Last edited:
I don’t feel it is completely accurate that B&W always changes their drivers for the best.
As an example the diamond tweeter clearly reduced the performance of the speaker setting it behind its predecessor.
Whether it is a problem with the material or the way they use it, I don’t know!
I would be very cautious when saying the new driver will of course better the old one, at least, until the speaker has been carefully auditioned.
Like Art has highlighted earlier the tweeter is still aligned with the front of the speaker which seems a little suspicious to me.
THE Nautilus is still the most revolutionary speaker in my book, its design is really unique and sets it apart from all the other more conventional speakers.
I wish the Nautilus wouldn’t require to be multi-amplified; if it wouldn’t I would think about it as soon as my finances would allow it.
However, the thing I am asking myself and that I would like to ask people around, is: how better does it get when someone already has a 800 (or equivalent speaker for what matters) and can properly drive it to max potential?
Myself, I have auditioned several speakers that were up to twice the price of my sig800 and found them to not bring much more to the plate as opposed to what I would have expected at that price point.
Maybe I am just oversimplifying things, but speakers nowadays are pretty similar and again, to me, the Nautilus seems to be still the speaker to beat at 60K.
I really hope the new series can take back the new Nautilus series capabilities of being analytical but yet musical and take it to the next level. If this is the case, then 30K for a new 800 would still be a “great deal” considering the price of similar items in the audio market.
As an example the diamond tweeter clearly reduced the performance of the speaker setting it behind its predecessor.
Whether it is a problem with the material or the way they use it, I don’t know!
I would be very cautious when saying the new driver will of course better the old one, at least, until the speaker has been carefully auditioned.
Like Art has highlighted earlier the tweeter is still aligned with the front of the speaker which seems a little suspicious to me.
THE Nautilus is still the most revolutionary speaker in my book, its design is really unique and sets it apart from all the other more conventional speakers.
I wish the Nautilus wouldn’t require to be multi-amplified; if it wouldn’t I would think about it as soon as my finances would allow it.
However, the thing I am asking myself and that I would like to ask people around, is: how better does it get when someone already has a 800 (or equivalent speaker for what matters) and can properly drive it to max potential?
Myself, I have auditioned several speakers that were up to twice the price of my sig800 and found them to not bring much more to the plate as opposed to what I would have expected at that price point.
Maybe I am just oversimplifying things, but speakers nowadays are pretty similar and again, to me, the Nautilus seems to be still the speaker to beat at 60K.
I really hope the new series can take back the new Nautilus series capabilities of being analytical but yet musical and take it to the next level. If this is the case, then 30K for a new 800 would still be a “great deal” considering the price of similar items in the audio market.
Also, this catches my attention...thought of bringing it up to this table...
Vivid Audio G1Giya loudspeaker Measurements | Stereophile.com
Vivid Audio G1Giya loudspeaker Measurements | Stereophile.com
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.