planet10 said:
Yes, the Tannoy CMS12 TDC looks interesting. Too bad, like the TAD professional drivers, there's no curves, which would tell us so much.
I heard the 6.5" consumer version of the Tannoy a few years back at the CES - and mmhh - it was just sort of OK. No big-driver magic, just another audiophile-balanced speaker, with pretty typical small-driver dynamics. It didn't do any of the holographic whiz-bang 3D things like the exotics, or even my speakers, which do the 3D hyperspace thing quite nicely.
The little Tannoy sounded like an entry-level audiophile speaker, like NHT or Boston Acoustics or similar. I was kind of disappointed, really, since I was expecting the single-point source would have MBL-type imaging. Nope, not there, just sort of generic image quality, and not the last word in smoothness or resolution at all (single-driver speakers way ahead there). Nothing stood out, really, and I was a bit surprised it sounded the way it did. I was expecting/hoping for that 12 or 15-inch Tannoy Monitor Gold magic, but it wasn't there.
It did make me wonder if the good engineers who designed the classic speakers had left the company, since engineers always like to leave their "stamp" on the sound of a company's products. Anyone that hears my speakers or electronics will hear what I'm aiming for, and it hasn't changed that much since I designed the Shadow Vector quadraphonic decoder - very deep-sounding with smooth, continuous soundfield with no sharp boundaries, vivid tonality, and a strong sense of being right there at the original performance. I aim for that - don't always get there, but that's the goal.
Other engineers aim for other things - the classic Tannoy sound, to me, is big and vivid, a sort of "right-there" quality, very impressionistic tone colors, image quality on the diffuse side, no extra-width effects, but a strong sense of "presence", but without the raucous and harsh presentation of the West Coast Altec/JBL sound. I'm not sure there is even a "Tannoy Sound" anymore - I have dinky little Tannoy HT speakers, but frankly, they sound pretty awful, not much like Tannoy at all.
But maybe they reserve the traditional sound for the Tokyo market at astronomical prices, and aim the other speakers at other markets. They're a big company, after all. Which leaves the sound of the CMS12 TDC an open question - sure would help to have response curves of the LF and HF drivers by themselves, as we have with other prosound vendors, even if it ain't the prettiest thing to look at.
Re: Re: Tannoy DC...
Have you ever heard any of the smaller ones? I turned a few heads of people who had pretty much that same experience, having them come up after demoing the Fonkens (FE127e) and say that they had never heard a Fostex they liked before -- and now with treated drivers they are better yet. Bud has a pair now to see if his process can further improve the driver.
This one doesn't fall into your efficiency requirements thou.
dave
Lynn Olson said:
Have you ever heard any of the smaller ones? I turned a few heads of people who had pretty much that same experience, having them come up after demoing the Fonkens (FE127e) and say that they had never heard a Fostex they liked before -- and now with treated drivers they are better yet. Bud has a pair now to see if his process can further improve the driver.
This one doesn't fall into your efficiency requirements thou.
dave
dmason said:
OK, I see three 10-inch drivers over at Tone Tubby site. The Alnico, the Ceramic 40/40, and the new Super Boy Bass driver (ceramic). I'm drawn to the Alnico, of course, but the Theile/Small efficiency is a bit on the low side, 94.6 dB/metre with 2.83V rms excitation. The high Qts of 1.39 points towards a magnet that needs to be a bit stronger, or at least focus more gausses in the gap. Frustratingly, the other two ceramic-magnet drivers are quite a bit more efficient, at 98 (40/40) and 97 (Bass) dB/metre with 2.83 V rms excitation.
Out of curiousity, when you were at the NAMM show, which driver was it? The gloss-red Alnico, the British-racing-green Ceramic 40/40, or the Super Boy for Bass in black?
I'd be the first to admit that hemp cones really are the thing - so much better than those awful carbon-fiber, Kevlar, and metal cones, and they bring a whole new dimension to paper, getting rid of the "cone cry" and compression of ordinary cones.
Lynn Olson said:
I suspect that this data may well be in the EASE file downloads -- but i can't figure out what software reads the files -- they aren't text, but there is enuff text to imply they are dat fles for a piece of software called ease -- google does turn up a couple hits but they don't seem appropriate.
dave
These were the Alnico 10. I wasnt interested in the ceramic jobs, and am equally frustrated with their higher SPL rating. The guys at TT seem to be in love with SuperBoy 10 for whatever reason; they put some in for Chris Squire and now he is the "poster boy" for this bass driver, and Ampeg followed on, with the SB10 as an option in their bass cabs. Sales took off. SuperBoy would work well too, I would imagine.
They also have their hands on some innovative ribbon driver which they are playing around with here in SD, mated to the 6.5 midwoof, and especially the 8 inch .... so absolutely, the 8 inch is in line for some sort of scaled down invention.
The Alnico 12&10 are the schnitz IMO, and NOTHING I have heard can touch the gestalt of the big cone HempTone. Except maybe the smaller ones....
Off topic, I have a pair of prototype 4.5 with Nd magnets, and they too are extremely nice.
They also have their hands on some innovative ribbon driver which they are playing around with here in SD, mated to the 6.5 midwoof, and especially the 8 inch .... so absolutely, the 8 inch is in line for some sort of scaled down invention.
The Alnico 12&10 are the schnitz IMO, and NOTHING I have heard can touch the gestalt of the big cone HempTone. Except maybe the smaller ones....
Off topic, I have a pair of prototype 4.5 with Nd magnets, and they too are extremely nice.
dmason said:
Well, I have to report the 12" Alnico TT with no crossover at all was simply stunning, with beautiful tonality and "tactility", and vocals were surprisingly good despite some forwardness - I was surprised at the 5 dB elevation for the 1.5 to 5 kHz region, it didn't sound like that much on audition. Kind of the opposite of an MTM, which measures good and sounds like ----.
One of my more perverse thoughts on EQ-ing the 12" with its crazy plateau was to "build up" the frequencies below 1.5 kHz, instead of attenuating the 1.5 to 5 kHz range. EQ-ing a speaker, especially passively, can rob it of life and sparkle, which would be tragic with something with the immediacy of the 12" Alnico TT (something the Alnico TT shares with the best Lowthers).
The "building-up" could be done by running the 12" TT full range, no attenuation, no nothing, and having another driver of good quality come in just below with a 1.2 kHz 12 dB/oct lowpass filter. Working together, they would produce a nice even 102 dB/metre over the full working range, and with no requirement to EQ the main 12" driver at all.
This technique might even work with the 10" driver, since I would bet the range above 1 kHz is elevated, maybe not as much as the 12" TT, but elevated all the same. This gives you a de facto higher efficiency, since the T/S efficiency is now dominated by two drivers in parallel, and one where directivity effects start coming in to raise the midband efficiency.
You can see how the idea for overlapping crossovers developed for the dipole - instead of pulling down the response through EQ or crossover shaping, you add to it by bringing in other drivers to complement the areas where the "main" driver is sagging. Do a little vector math (when in-phase, voltages add) and it turns out that even a somewhat less efficient driver can "help out" by 1, 2, or 3 dB.
agent.5 said:
Two differences: the heavier VC is going to roll off earlier, maybe be a little bumpier at the top of the range (VC mass is parasitic and does nothing good for the cone). Bu this usually isn't a big deal unless you're talking Lowther with its ultralight cone.
The other difference is the efficiency as driven by a 2.83V rms source - this is the dB/metre efficiency spec of interest. Even tube amps are mostly voltage sources, so dB/volts is of more interest than dB/watts, which are only meaningful if each driver has its own personal variable-ratio transformer.
The 16-ohm VC certainly makes life simpler if you're planning on pairs, as for example the bass module of the new speaker.
Moving on to more general topics, I can easily see a mix of 18Sound and TT drivers for the new system - 10's, 12's and 15's, or pairs of 12's for the bass module. Although the two vendors are totally different - one retro and one modern - they're both very good at what they do.
What properties (or combination of) make Hemp such a good material for speaker cones? I mean, fiber length, tensile strength/weight, etc? I ask, because there are other "hemps" other than cannabis sativa hemp (Yucca, Bowstring, Manila, etc) which surpass "hemp" on some points.
Lynn: you have mentioned you like alnico more than ceramic magnets (immediacy, that "certain something"). What is your take on Neodymium?
The TT drivers may be worth every penny (musically) but from the web site pics (specially the chassis) they seem to me a little pricey.
Lynn: you have mentioned you like alnico more than ceramic magnets (immediacy, that "certain something"). What is your take on Neodymium?
The TT drivers may be worth every penny (musically) but from the web site pics (specially the chassis) they seem to me a little pricey.
Lynn Olson said:
Are there any woven kelvar cone speakers that get good reviews? I purchased a B&W midrange on eBay that has a curve-linear profile, woven with variable thickness kevlar cone... very good sounding and better behaved than metal cones. The technology to weave one continuously variable profile cone seems critical. The Auto woofers use cut Kevlar and carbon fiber sheets with straight profiles, and the glassy thermal resins seem to create fast moving high frequency noise.
Hot pressing paper or hemp fibers in a form seems like lower tech that more shops can afford.
http://www.bwspeakers.com/index.cfm.../ObjectID/3808A254-3AB8-11D4-A67F00D0B7473B37
Attachments
LineSource said:
Well, if the opinion of $tereophile and Absolute Sound are important to you, Kevlar is the way to go. When I think of Kevlar, I think of the Focal Kevlar driver shown below, which was used in Wilson Audio and other extremely expensive speakers of the day.
It is significant that Kevlar and carbon-fiber cones are typically used with 24 dB/octave crossovers, which tells you something about the out-of-band performance. Reviewers who have never designed a speaker confuse the characteristic upper-mid harshness with "detail" - when it is nothing of sort, it's just a series of resonances in the upper-mid region.
After following the B&W link above, I find it a significant that after writing at considerable length about the superiority of their proprietary Kevlar cone, there are no impulse response and no frequency response curves of the driver by itself. If it is as good as they say, where's the raw, unsmoothed data of the raw driver? B&W certainly owns MLSSA and even more powerful measurement systems- where's the data to support the claims?
Attachments
Good vs Bad FR Curves
I was a little too quick to dismiss Kevlar and carbon-fiber cones - the ones I measured were some ten years ago, and were pretty bad examples of the breed. Surely by now, they've improved - I would hope so, after all the money that's been thrown at them by big-name vendors like B&W, Celestion, Focal, Audax, and others.
I admit when I see a low-efficiency 5" to 7" driver with severe resonances, I get annoyed - little drivers are easier to get right than big ones, and with efficiency in the very modest 86 to 89 dB/metre range, there's room for a couple of dB of efficiency to throw away on cone-damping techniques. There are plenty of smooth-measuring drivers in this size and efficiency category - although there are plenty of dogs too.
The reason for developing little drivers with rigid cones is to satisfy the market and the magazine reviewers, who are endlessly thrilled with each and every tiny speaker with "bass slam". While this might seem laughable to anyone that loves 12 and 15-inch drivers and horns, the reviewers really get off on the whole "bass slam" thing.
There's only one way to stuff a big-bass quart into a pint pot - linearize the gap geometry and magnet structure as much as possible (which can cost efficiency), select a 200-watt high-damping amplifier to overcome the low efficiency with brute electro-motive force, and use the most rigid cone possible (to minimize cone flexing in the midbass region). There's your slam for you - which is all about midbass performance. Car-audio vendors in particular have gone down this road to an absurd extent, with kilowatt amplifiers being nothing special anymore.
But nothing is for free. Rigid cones, although good for midbass, are more prone to standing-wave resonances, which exacts a cost at higher frequencies. This tradeoff goes unmentioned by the rigid-cone advocates, just as the converse tradeoff occurs with floppy poly cones in any size beyond 6 inches. Paper has the charm of being a good all-around compromise, and of course there are a zillion ways to add this or that composite to the mix, which is nothing more than a slurry of paper fibers. Paper itself can be made from ground-up fibers of any sort - wool, cotton, wood pulp, and the historic favorite, hemp. I'm surprised nobody's tried papyrus yet.
Getting big, efficient drivers to behave - now, that's more interesting. What's been sad has been discovering just how bad coaxial drivers are - B&C is a solid, well-respected vendor making top-flight pro drivers, but the curves for coaxes they make are just horrendous, way worse than the 5" Focal 5K013L I was banging on in the last post. And B&C has plenty of company in the pro world - even the 18Sound coaxials are only just OK in the measurement department. Other vendors like to conceal the true state of affairs by only publishing a smoothed composite curve, never a good sign.
When you see 15 dB peak-to-valley ratios, that points to geometric problems (resonant structures) that I'm pretty sure are beyond the range of cone treatments to remedy. The small area where the coaxial horn joins the bass cone just seems to be a very difficult design problem, both for the horn termination and the VC former/center-of-cone area of the bass driver.
I was a little too quick to dismiss Kevlar and carbon-fiber cones - the ones I measured were some ten years ago, and were pretty bad examples of the breed. Surely by now, they've improved - I would hope so, after all the money that's been thrown at them by big-name vendors like B&W, Celestion, Focal, Audax, and others.
I admit when I see a low-efficiency 5" to 7" driver with severe resonances, I get annoyed - little drivers are easier to get right than big ones, and with efficiency in the very modest 86 to 89 dB/metre range, there's room for a couple of dB of efficiency to throw away on cone-damping techniques. There are plenty of smooth-measuring drivers in this size and efficiency category - although there are plenty of dogs too.
The reason for developing little drivers with rigid cones is to satisfy the market and the magazine reviewers, who are endlessly thrilled with each and every tiny speaker with "bass slam". While this might seem laughable to anyone that loves 12 and 15-inch drivers and horns, the reviewers really get off on the whole "bass slam" thing.
There's only one way to stuff a big-bass quart into a pint pot - linearize the gap geometry and magnet structure as much as possible (which can cost efficiency), select a 200-watt high-damping amplifier to overcome the low efficiency with brute electro-motive force, and use the most rigid cone possible (to minimize cone flexing in the midbass region). There's your slam for you - which is all about midbass performance. Car-audio vendors in particular have gone down this road to an absurd extent, with kilowatt amplifiers being nothing special anymore.
But nothing is for free. Rigid cones, although good for midbass, are more prone to standing-wave resonances, which exacts a cost at higher frequencies. This tradeoff goes unmentioned by the rigid-cone advocates, just as the converse tradeoff occurs with floppy poly cones in any size beyond 6 inches. Paper has the charm of being a good all-around compromise, and of course there are a zillion ways to add this or that composite to the mix, which is nothing more than a slurry of paper fibers. Paper itself can be made from ground-up fibers of any sort - wool, cotton, wood pulp, and the historic favorite, hemp. I'm surprised nobody's tried papyrus yet.
Getting big, efficient drivers to behave - now, that's more interesting. What's been sad has been discovering just how bad coaxial drivers are - B&C is a solid, well-respected vendor making top-flight pro drivers, but the curves for coaxes they make are just horrendous, way worse than the 5" Focal 5K013L I was banging on in the last post. And B&C has plenty of company in the pro world - even the 18Sound coaxials are only just OK in the measurement department. Other vendors like to conceal the true state of affairs by only publishing a smoothed composite curve, never a good sign.
When you see 15 dB peak-to-valley ratios, that points to geometric problems (resonant structures) that I'm pretty sure are beyond the range of cone treatments to remedy. The small area where the coaxial horn joins the bass cone just seems to be a very difficult design problem, both for the horn termination and the VC former/center-of-cone area of the bass driver.
Hi Lynn,
Much of the upper range colouration (UK) and increase in output from a driver arises from the centre region.
I know you mention using an additional driver to lift efficiency at the lower frequencies, but this still won't give us clean HF.
Using a coaxial gives point source. Using mid, tweeter etc. gives us a reproducing panel where the sound changes as you move about, and in stereo there are two independent changes arising about what ought to be the original image. To me the 'field' errors due to flat panel driver arrangement far exceed those due to coaxial anomalies.
I have not yet seen any discussuion in this thread about bra-strap or pole piece mounting a mid/high cone driver in front of say a 12" running full range, with the back of the central driver being covered in sound absorbent material to both absorb centre of main cone HF disturbances and protect the mid/high from cone excitation.
The placement of damping material in front of a main driver will improve its entirel natural roll-off/crossover, and allow simple C filtering to the mid/high (with possible suitable R+C matching/damping) and produce a main assembly which needs only one amplifier.
Also the alignment (needs to adjusted empirically with C and damping material) can augment the crossover characteristics.
This allows most use of the main driver (with LF augmentation as/if necessary) with a much smaller one - short wavelength spaced in front....... any thoughts ?
Cheers ........... Graham.
Much of the upper range colouration (UK) and increase in output from a driver arises from the centre region.
I know you mention using an additional driver to lift efficiency at the lower frequencies, but this still won't give us clean HF.
Using a coaxial gives point source. Using mid, tweeter etc. gives us a reproducing panel where the sound changes as you move about, and in stereo there are two independent changes arising about what ought to be the original image. To me the 'field' errors due to flat panel driver arrangement far exceed those due to coaxial anomalies.
I have not yet seen any discussuion in this thread about bra-strap or pole piece mounting a mid/high cone driver in front of say a 12" running full range, with the back of the central driver being covered in sound absorbent material to both absorb centre of main cone HF disturbances and protect the mid/high from cone excitation.
The placement of damping material in front of a main driver will improve its entirel natural roll-off/crossover, and allow simple C filtering to the mid/high (with possible suitable R+C matching/damping) and produce a main assembly which needs only one amplifier.
Also the alignment (needs to adjusted empirically with C and damping material) can augment the crossover characteristics.
This allows most use of the main driver (with LF augmentation as/if necessary) with a much smaller one - short wavelength spaced in front....... any thoughts ?
Cheers ........... Graham.
Hmmm - some interesting thoughts here.
The drivers of interest have efficiencies in the 95.5 to 99 dB/metre range - this is the baseline T/S efficiency in the piston-band, so any peaks are elevated above that.
These figures rule out dome tweeters, which don't exist in this efficiency range. No old-school cone tweeters, either. We're left with with prosound ribbons and horns, each with their own set of problems.
Several pages back, we had an interesting proposal for a custom driver with a 4" VC assembly and a coaxially mounted ribbon where a pole-piece would normally sit. The ribbon could sit fairly deep in the woofer, almost touching the interior of the cone, or it could extend further out on a cylindrical pole-piece. The extended version would be compatible with your suggestion for local felt damping near the center of the cone, where it could do the most good.
As for horns, hmmm - most of them are kind of big, in order to have a successful 1.5 ~ 2 kHz crossover, which we're going to need. This means using the woofer cone as a horn extension, a la Tannoy, with all the problems we've seen so far, or a more Altec Duplex approach where the horn actually shades part of the cone.
The most extreme shading is on the BMS 15CN680, where the horn is certainly big enough, but the bass driver is looking distinctly unhappy around 1.2 kHz, which is obviously caused by the cavity between the horn and the woofer cone. But maybe a little bit of strategically placed felt would make a difference - at least de-Q the notch at 1.2 kHz.
The UREI-modified Altec Duplex took the approach of covering the surface of the small horn with foam, which had a modest degree in success in taming the raucous midrange of the 15" Duplex. But UREI Duplex was still a long way from flat in the midrange.
I guess the real way to test the theory is start with a known-good 12 or 15-inch driver, and suspend a damping pad in the center and seeing what it does. I'm not sure many drivers will tolerate a several cubic-inch object suspended in the center of the driver - although streamlining could make a quite a difference to the overall result, with the object ending up looking like a sort of an egg-shaped phase-plug as seen from the woofer cone.
In essence, a phase-plug, and a good one, has to be designed, and then a very compact horn fitted in the middle. This is do-able, I guess, but we're talking about a serious research effort just to optimize the phase-plug, so it improves the response instead of degrading it. The phase-plugs I've seen so far optimize the response off-axis, but have negative effects on the impulse response. Again, do-able, but with a different emphasis than we've seen so far.
The drivers of interest have efficiencies in the 95.5 to 99 dB/metre range - this is the baseline T/S efficiency in the piston-band, so any peaks are elevated above that.
These figures rule out dome tweeters, which don't exist in this efficiency range. No old-school cone tweeters, either. We're left with with prosound ribbons and horns, each with their own set of problems.
Several pages back, we had an interesting proposal for a custom driver with a 4" VC assembly and a coaxially mounted ribbon where a pole-piece would normally sit. The ribbon could sit fairly deep in the woofer, almost touching the interior of the cone, or it could extend further out on a cylindrical pole-piece. The extended version would be compatible with your suggestion for local felt damping near the center of the cone, where it could do the most good.
As for horns, hmmm - most of them are kind of big, in order to have a successful 1.5 ~ 2 kHz crossover, which we're going to need. This means using the woofer cone as a horn extension, a la Tannoy, with all the problems we've seen so far, or a more Altec Duplex approach where the horn actually shades part of the cone.
The most extreme shading is on the BMS 15CN680, where the horn is certainly big enough, but the bass driver is looking distinctly unhappy around 1.2 kHz, which is obviously caused by the cavity between the horn and the woofer cone. But maybe a little bit of strategically placed felt would make a difference - at least de-Q the notch at 1.2 kHz.
The UREI-modified Altec Duplex took the approach of covering the surface of the small horn with foam, which had a modest degree in success in taming the raucous midrange of the 15" Duplex. But UREI Duplex was still a long way from flat in the midrange.
I guess the real way to test the theory is start with a known-good 12 or 15-inch driver, and suspend a damping pad in the center and seeing what it does. I'm not sure many drivers will tolerate a several cubic-inch object suspended in the center of the driver - although streamlining could make a quite a difference to the overall result, with the object ending up looking like a sort of an egg-shaped phase-plug as seen from the woofer cone.
In essence, a phase-plug, and a good one, has to be designed, and then a very compact horn fitted in the middle. This is do-able, I guess, but we're talking about a serious research effort just to optimize the phase-plug, so it improves the response instead of degrading it. The phase-plugs I've seen so far optimize the response off-axis, but have negative effects on the impulse response. Again, do-able, but with a different emphasis than we've seen so far.
Phase plug - like a felted Lowther one with a tweeter cone in the end.
Are there any high sensitivity mid/high cone drivers as made for professional horns ?
That small Tannoy above with its own conical felted rear damping layer and running for hi-mids upwards in front of a 12" or 15" ?
Depth likely a problem though.
Cheers ........ Graham.
Are there any high sensitivity mid/high cone drivers as made for professional horns ?
That small Tannoy above with its own conical felted rear damping layer and running for hi-mids upwards in front of a 12" or 15" ?
Depth likely a problem though.
Cheers ........ Graham.
Raal and Hemp
Great thread, and right in line with my current interests, too.
I have read only to page 29 and expect it to take a couple of days to get to the last post and find out if this has been raised:
In looking at the Raal site, I see on the "news" page that they have apparently severed business relations with Hemp Acoustics, as of Nov 06.
I wonder what that's about.
http://www.raalribbon.com/news.htm
Russell
Great thread, and right in line with my current interests, too.
I have read only to page 29 and expect it to take a couple of days to get to the last post and find out if this has been raised:
In looking at the Raal site, I see on the "news" page that they have apparently severed business relations with Hemp Acoustics, as of Nov 06.
I wonder what that's about.
http://www.raalribbon.com/news.htm
Russell
Re: 12" Beyma... Liberty 8
It's funny since I was also thinking about Beyma drivers, as a local speaker company uses them in their high efficiency designs.
I was just doing a little browsing around on the Beyma site looking at the curves when I came across the curves for the 12G40, they look quite nice through the midband region with a peak at 5k, after which they drop off. The info can be found on the Beyma product page by selecting G40 series in the Low Frequency box under "Pro". The graphs are in the PDF downloads. There's probably several other useable drivers there, I haven't had the chance to go through them yet.
chrismercurio said:
It's funny since I was also thinking about Beyma drivers, as a local speaker company uses them in their high efficiency designs.
I was just doing a little browsing around on the Beyma site looking at the curves when I came across the curves for the 12G40, they look quite nice through the midband region with a peak at 5k, after which they drop off. The info can be found on the Beyma product page by selecting G40 series in the Low Frequency box under "Pro". The graphs are in the PDF downloads. There's probably several other useable drivers there, I haven't had the chance to go through them yet.