The hemp cone Eminence speakers are called cannibas rex
http://www.eminence.com/pdf/cannabisrex.pdf
http://www.eminence.com/pdf/cannabisrex-16.pdf
On the other hand, we can probably get the HempAcoustics 12" coaxial for a pretty good price if we order 100. I am thinking around $300 each.
Although Romy the Cat's posts are a bit on the "poetic" side, he's got a good point about crossing ribbons too low. Ribbons have essentially zero linear travel, unlike most conventional VC+magnet assemblies. This means getting greedy and crossing them too low is asking for a massive jump in coloration and an even bigger drop in resolution - the whole point of using a ribbon. Remember, the analog is a ribbon mike - and ribbon mikes are easily overloaded by modest wind currents.
But using ribbons to complement a compression driver makes sense - they're usually starting to fade at 15 to 18 kHz, and notching out the typical aluminum or titanium peak is a good idea, even if the peak is at 22 kHz (it is STILL audible in terms of increased IM distortion).
It always makes sense to use drivers well within their useful bandwidth - horns are not happy handling energy close to the edge of the bandpass (the region of greatest HOMs and greatest impedance variation), and running drivers where they exhibit HF peaks isn't such a great idea either. I'm one of those guys that prefers to select cone drivers with very smooth rolloff characteristics, cross them an octave higher than most folks, and use the tweeter very conservatively. That results in low tweeter IM distortion and much more relaxed and natural sound.
Accordingly, I'm looking at a coax with the best-looking rolloff regions from the bass cone, and plan to cross somewhere between 1.8 and 3.2 kHz, depending on what I can get away with. Yes, I plan to rely on the proposed cone treatments to optimize the cone performance - at least I'm not trying to get the bandwidth the Walsh folks are aiming for over in their thread.
With a ribbon taking over at the highest frequencies, the performance of the compression driver above 12 kHz is less critical. Squeezing extra bandwidth out of a horn is always difficult - they are not intrinsically wideband radiators, so attempts to extend the HF exacts a cost at the other end.
But using ribbons to complement a compression driver makes sense - they're usually starting to fade at 15 to 18 kHz, and notching out the typical aluminum or titanium peak is a good idea, even if the peak is at 22 kHz (it is STILL audible in terms of increased IM distortion).
It always makes sense to use drivers well within their useful bandwidth - horns are not happy handling energy close to the edge of the bandpass (the region of greatest HOMs and greatest impedance variation), and running drivers where they exhibit HF peaks isn't such a great idea either. I'm one of those guys that prefers to select cone drivers with very smooth rolloff characteristics, cross them an octave higher than most folks, and use the tweeter very conservatively. That results in low tweeter IM distortion and much more relaxed and natural sound.
Accordingly, I'm looking at a coax with the best-looking rolloff regions from the bass cone, and plan to cross somewhere between 1.8 and 3.2 kHz, depending on what I can get away with. Yes, I plan to rely on the proposed cone treatments to optimize the cone performance - at least I'm not trying to get the bandwidth the Walsh folks are aiming for over in their thread.
With a ribbon taking over at the highest frequencies, the performance of the compression driver above 12 kHz is less critical. Squeezing extra bandwidth out of a horn is always difficult - they are not intrinsically wideband radiators, so attempts to extend the HF exacts a cost at the other end.
DougL said:
My thoughts: the floor transition should be left alone, no treatment whatever. The floor reflection is there no matter what you do.
However, the sides and top edges do need treatment. I'd space the holes closest to the edge most closely together, and open up the spacing for the rows further away. Maybe you could follow a golden-section ratio (0.618:1.0:1.618:2.618) for the spacing of the rows as they get further away from the edge of baffle. Again, make the holes small, no more than 1/4" across, and maybe smaller, like an 1/8" or less.
You don't need to go crazy drilling holes over the entire edge of the baffle - the regions closest to the driver are most important, while the regions 2 or 3 feet away are less important, since local surface pressures drop off rapidly with distance.
I'd simply round-over the edge of the baffle, so a 3/4" baffle has a round-over with a 3/4" diameter.
Don't forget to use golden-section ratios for the L/R distances. For example: for a 15" driver, imagine the distance between the Left edge and the driver centerline is 10". If you choose 10", then the distance between the driver centerline and the Right edge should be 16.18". I'd split the difference going to the top, so the distance between the driver centerline and the top would be about 12.5" or so.
(The baffles should be mirror-imaged, of course. This example only applies to the Right speaker. The Left speaker should be the mirror image of the Right.)
For a coax, is a compression tweeter mandatory but still not end up with something like a car audio driver? eg Using one of the Eminence coax woofers there is plenty of room in that CD horn to mount a small tweeter. For pro applications or if you're shooting for close to 100db/w/m, I understand the need for the high efficiency, but in the 93-95 sensitivity range doesn't a non-compression tweet make sense? I understand some kind of waveguide may be necessary, but otherwise is there anything inherently wrong in that approach, especially since it offers the opportunity for more ideal physical alignment?
Big Driver, Big Sound
People ask why I'm interested in such a big midrange driver, when the most straightforward way to get flat response and an easy join to the HF driver is an 8-incher - which goes out to 5, 8, or even 10 kHz without breaking a sweat.
Well, it was listening to the 12-inch wideband driver in the Bastanis Apollo that left such a strong impression. Yes, there were issues (but then every speaker has "issues") but the commanding in-the-room presence and the impression of weight and size from pianos and drums was unmatched by any speaker with smaller drivers - including small-driver arrays and planars. At the same time, vocals were realistically sized, and most important of all, unstressed, with almost no "loudspeaker" coming-out-of-a-box impression. That, of course, is the sound of a big pro-quality driver, in an open baffle.
That's what big drivers do - and without that "projected", in-your-lap quality of horns. Getting big drivers to behave well above 1.5 kHz is difficult, challenging maybe, but not impossible. Robert Bastani succeeded with his very exotic cone treatment - which led to thinking about other ways to get good performance in the 1.5 kHz to 5 kHz region - and then on to this thread here in diyAudio.
It was that experience that made me realize the way forward wasn't to wait patiently from the Loudspeaker Gods for new wonder drivers, but take things into your own hands and make the drivers that needed to be created. I'd been waiting 15 years for Scan-Speak, Vifa, Seas, and Dynaudio to come through with high-performance high-efficiency drivers, and you know what, 15 years is too long to wait!
People ask why I'm interested in such a big midrange driver, when the most straightforward way to get flat response and an easy join to the HF driver is an 8-incher - which goes out to 5, 8, or even 10 kHz without breaking a sweat.
Well, it was listening to the 12-inch wideband driver in the Bastanis Apollo that left such a strong impression. Yes, there were issues (but then every speaker has "issues") but the commanding in-the-room presence and the impression of weight and size from pianos and drums was unmatched by any speaker with smaller drivers - including small-driver arrays and planars. At the same time, vocals were realistically sized, and most important of all, unstressed, with almost no "loudspeaker" coming-out-of-a-box impression. That, of course, is the sound of a big pro-quality driver, in an open baffle.
That's what big drivers do - and without that "projected", in-your-lap quality of horns. Getting big drivers to behave well above 1.5 kHz is difficult, challenging maybe, but not impossible. Robert Bastani succeeded with his very exotic cone treatment - which led to thinking about other ways to get good performance in the 1.5 kHz to 5 kHz region - and then on to this thread here in diyAudio.
It was that experience that made me realize the way forward wasn't to wait patiently from the Loudspeaker Gods for new wonder drivers, but take things into your own hands and make the drivers that needed to be created. I'd been waiting 15 years for Scan-Speak, Vifa, Seas, and Dynaudio to come through with high-performance high-efficiency drivers, and you know what, 15 years is too long to wait!
Hi Lynn, have a look at the P.Audio SN15B which seems to have a smooth rolloff at about 3kHz. This is, of course, if you believe the P.Audio graphs are accurate - and in some cases they're definitely not. However, I have a custom pair of coaxes made by P.Audio from SN15B chassis/cones with SD750N compression drivers. OB mounted of course. I'm running the woofers virtually full-range, compression driver kicks in at about 3K 1st order with a Fostex Ft17 helping out at the top and they sound pretty good to me!Lynn Olson said:
Cheers,
Mike Spence
johninCR said:
This problem partitions quite easily - the Qts of the wideband driver doesn't matter if another driver is helping out at lower frequencies - and the LF driver does have an appropriate Qts between 0.65 and 1.1. The LF can have a complementary "flavor" since it shares the 80 to 300 Hz region with the wibeband driver. For example, a pair of 12" Alnico Tone Tubby's (mounted right at floor level) might be just the perfect complement for the P.Audio SN15B mentioned below.
Too efficient to match the wideband driver? Excess efficiency, along with huge cone area, is exactly what we want in the 1/f rolloff region. Instead of a lot of equalization, we bring in extra drivers, and help them out by placing them next to the floor (which creates an image, thus doubling the effective radiating area).
The overlap in the crossover - by using tapped inductors or bi-amping with parametric EQ - is how the response in the midbass is shaped. Since listening rooms need to be individually compensated from 300 Hz and below, this adjustability is a good thing to have. In fact, in most listening rooms, you'll need different equalization for the L and R channels in the 100 to 300 Hz region.
mikey_audiogeek said:
Thanks for the tip, very much appreciated, especially the info about the custom SN15B + SD750N compression drivers. Sayonara, low-efficiency audiophile drivers!
Linkwitz's recent Epiphany is that the best dipole speakers maintain the dipole radiation pattern over the full frequency range. For the Orion+ he added an identical monopole rear tweeter back-to-back with the front tweeter, and is very positive about the audible improvement.
I live with full range dipole Apogees and also found that full range dipole radiation is best, and ended up with just a rear wall diffuser.
A coaxial speaker would add complications to maintaining dipole radiation over the full frequency range. A simple DIY dipole ribbon tweeter, large enough to be crossed at 1-1.5Khz to a standard mid-woofer, might be worth discussion if all-dipole becomes a lock-out spec as Linkwitz would recommend.
I live with full range dipole Apogees and also found that full range dipole radiation is best, and ended up with just a rear wall diffuser.
A coaxial speaker would add complications to maintaining dipole radiation over the full frequency range. A simple DIY dipole ribbon tweeter, large enough to be crossed at 1-1.5Khz to a standard mid-woofer, might be worth discussion if all-dipole becomes a lock-out spec as Linkwitz would recommend.
Lynn Olson said:
Hi Lynn, a bit more info: I'm powering the whole caboodle with a John Swenson transconductance amp, lightly modified to give an output impedance of about 20R. This "modifies" the Qts sufficiently such that the SN15B is flat to 40Hz (resonant freq) on an OB that measures 1200mm x 750mm. No sub!
LineSource said:
Not if you take the back off the compression drivers to expose the diaphragm for dipole operation, like I (and others) have...
OK, I agree that to make a coax with a ribbon is a tall order. I guess I was influenced by Lynn saying his fallback position was to use a ribbon with a large pro driver. It is hard to get a large enough ribbon to fit, AND it is true- you don't want to push the things. On the other hand, I use a small ribbon down to 4.5 khz and it sounds great- basically my speakers are the 8" with ribbon and large pro woofer option that Lynn says is the obvious solution, but that doesn't have the impact he is looking for. I can believe this, mine is a bit thin compared to what he is describing.
As Lynn said in the beginning, he seems most interested in a coax driver with a horn. Taming the horn is the challenge but if the proposed methods work then it could be amazing.
So, if we focus back on the coax, the Hemp Acoustics seems to be a must listen. Basically we are burning up time here - in a good way- getting lots of info- until the HA drivers are available.
As Lynn mentioned, working with a manufacturer closely is a very efficient process. HA has been able to do this, and since their intention is to produce a coax HiFi speaker, its seems that they are very likely to do a good job. Most home horn systems are adapting pro hardware for a different purpose: home hifi. The HA people are able to work directly with the manufacturer to make the driver work in the home context. This does make the comparison to Tannoy reasonably valid. If one does a search of all the pro co-ax drivers available , it's overwhelming- there are at least 25 out there easily available, and when you consider mixing and matching different horn drivers for the coax's that allow this, it is a lot of choices.
Probably we should all send Lynn $100 so that he can order all of the pro coax's out there!! Then he could listen to and measure just the bass cone without the tweeter on, and determine the "best". Then mix and match the horn drivers until he gets the right combo... I don't know if this could happen, but if it could, it would happen here.
This is another example, as mentioned above, that a company has some advantages over us- like that ordering $15,000 worth of drivers isn't that big a deal!
The hobbyist advantage is that we can take a great product and make it better, because we have the time to sweat the details. The various ways mentioned that can control standing waves and diffraction are examples of what we can work with.
Another example is the idea of opening the back of the horn driver. That is a pretty exciting idea, not only giving us a dipole, but also changing the damping of the driver maybe. If we played around with the idea and it worked well, I'm sure that someone would pop up that could make a custom backplate with a built -in rear horn if it were required for loading or volume. Probably owners could just modify the existing backplate with an opening. Or Hemp Acoustics might be convinced to make it an option on their open baffle driver.
Hemp Acoustics is introducing a lot of products at the same time so it is understandable that it is taking a while. If their coax's are as good as we hope, they are worth supporting. As far as I can see, they are about the only manufacturer doing this for the home market that is striving for the highest quality.
IMHO they should speed a pair to Lynn ASAP!
Homestar Runner avatar? yup It's the coolest!
As Lynn said in the beginning, he seems most interested in a coax driver with a horn. Taming the horn is the challenge but if the proposed methods work then it could be amazing.
So, if we focus back on the coax, the Hemp Acoustics seems to be a must listen. Basically we are burning up time here - in a good way- getting lots of info- until the HA drivers are available.
As Lynn mentioned, working with a manufacturer closely is a very efficient process. HA has been able to do this, and since their intention is to produce a coax HiFi speaker, its seems that they are very likely to do a good job. Most home horn systems are adapting pro hardware for a different purpose: home hifi. The HA people are able to work directly with the manufacturer to make the driver work in the home context. This does make the comparison to Tannoy reasonably valid. If one does a search of all the pro co-ax drivers available , it's overwhelming- there are at least 25 out there easily available, and when you consider mixing and matching different horn drivers for the coax's that allow this, it is a lot of choices.
Probably we should all send Lynn $100 so that he can order all of the pro coax's out there!! Then he could listen to and measure just the bass cone without the tweeter on, and determine the "best". Then mix and match the horn drivers until he gets the right combo... I don't know if this could happen, but if it could, it would happen here.
This is another example, as mentioned above, that a company has some advantages over us- like that ordering $15,000 worth of drivers isn't that big a deal!
The hobbyist advantage is that we can take a great product and make it better, because we have the time to sweat the details. The various ways mentioned that can control standing waves and diffraction are examples of what we can work with.
Another example is the idea of opening the back of the horn driver. That is a pretty exciting idea, not only giving us a dipole, but also changing the damping of the driver maybe. If we played around with the idea and it worked well, I'm sure that someone would pop up that could make a custom backplate with a built -in rear horn if it were required for loading or volume. Probably owners could just modify the existing backplate with an opening. Or Hemp Acoustics might be convinced to make it an option on their open baffle driver.
Hemp Acoustics is introducing a lot of products at the same time so it is understandable that it is taking a while. If their coax's are as good as we hope, they are worth supporting. As far as I can see, they are about the only manufacturer doing this for the home market that is striving for the highest quality.
IMHO they should speed a pair to Lynn ASAP!
Homestar Runner avatar? yup It's the coolest!
For a top quality unit I don't think that's out of line, and hey- you get 2 drivers! Is that for the 12"?
I thought that they wanted over a thousand for the 15".
We've gotten some great group buys in the past, from the likes of Cardas and other high end brands. Who knows? maybe a one time introductory offer to DIY Audio members?
I thought that they wanted over a thousand for the 15".
We've gotten some great group buys in the past, from the likes of Cardas and other high end brands. Who knows? maybe a one time introductory offer to DIY Audio members?
I saw a couple posts talking about dumping the compression driver in a coax and using the 'horn' to mount a ribbon -or other.
I was thinking about this too...
I was thinking of taking a tweeter like this one. Remove the rear chamber cover. Affix (seal) the rear of the tweeter to the horn and use the horn's internal volume as the tweeter rear chamber.
Maybe you could treat the sides and rear of the tweeter with a damping material and turn the edge of the tweeters waveguide/flange into 'swiss cheese' a la mamboni(?).
edit: or chuck it up in the lathe and take the flange right down
I was thinking about this too...
I was thinking of taking a tweeter like this one. Remove the rear chamber cover. Affix (seal) the rear of the tweeter to the horn and use the horn's internal volume as the tweeter rear chamber.
Maybe you could treat the sides and rear of the tweeter with a damping material and turn the edge of the tweeters waveguide/flange into 'swiss cheese' a la mamboni(?).
edit: or chuck it up in the lathe and take the flange right down
Daryl Hawthorne ( Mr. Silver Iris) is currently polling for consensus on how to evolve the specs for higher end drivers with his moniker.
He has a well established business arrangement with Eminence, and has sold many more than 100pairs of drivers, to very satisfied DIYers in over 17 countries, including I believe some posters to this thread.
Rather than wait for HA to ramp up production of their new coax drivers, why not enjoin him in this endeavor? As has been noted, with appropriate minimum orders, Eminence engineers are more than happy to assist in meeting custom specifications. They certainly have a reputation for quality, value, reasonable production schedules, and customer service, all to a level that HA has yet to demonstrate.
I doubt very much that Daryl would object to any increase in his sales from such a custom spec'd driver.
He has a well established business arrangement with Eminence, and has sold many more than 100pairs of drivers, to very satisfied DIYers in over 17 countries, including I believe some posters to this thread.
Rather than wait for HA to ramp up production of their new coax drivers, why not enjoin him in this endeavor? As has been noted, with appropriate minimum orders, Eminence engineers are more than happy to assist in meeting custom specifications. They certainly have a reputation for quality, value, reasonable production schedules, and customer service, all to a level that HA has yet to demonstrate.
I doubt very much that Daryl would object to any increase in his sales from such a custom spec'd driver.
ChrisB,
While Eminence seems to run a tight ship schedule-wise, I've been waiting for the 10" coax that was expected to be out last July, so your comparison to HA is without full info. When Darrel comes out with something new, I'll be more than happy to give it a twirl. A group buy that I'd like to be part of would be trying to come up with something different and save money too, especially since it could eliminate an extra layer of profit.
While Eminence seems to run a tight ship schedule-wise, I've been waiting for the 10" coax that was expected to be out last July, so your comparison to HA is without full info. When Darrel comes out with something new, I'll be more than happy to give it a twirl. A group buy that I'd like to be part of would be trying to come up with something different and save money too, especially since it could eliminate an extra layer of profit.
SI has certainly staked out a claim for HiFi consideration.
Here's the Eminence custom info:
http://www.eminence.com/custom.asp
HiFi buzzwords I like:
Do they really mean anything? I don't know...
Deltalite minimal basket with neodymium magnets
The weight savings alone for shipping covers the cost.
OK, could also consider Alnico magnets..
Hemp cone- that's trendy...
It would be very cool to be the first to get a Deltalite based coax.
But the Deltalites have a 2.5 " coil which is different than the beta coax has and they probably aren't interchangable.
There is only one basket made for coax I believe That's a steel one in the Beta line and the beta's have a 2" coil. That would probably be easy to rig with an Alnico magnet and hemp cone as they use that for their instrument speakers.
Here's the Eminence custom info:
http://www.eminence.com/custom.asp
HiFi buzzwords I like:
Do they really mean anything? I don't know...
Deltalite minimal basket with neodymium magnets
The weight savings alone for shipping covers the cost.
OK, could also consider Alnico magnets..
Hemp cone- that's trendy...
It would be very cool to be the first to get a Deltalite based coax.
But the Deltalites have a 2.5 " coil which is different than the beta coax has and they probably aren't interchangable.
There is only one basket made for coax I believe That's a steel one in the Beta line and the beta's have a 2" coil. That would probably be easy to rig with an Alnico magnet and hemp cone as they use that for their instrument speakers.
Variac said:
For various secondary sources, it is $600 MRSP for the 12" coaxial and $1200 MRSP for the 15" coaxial. Knowing that virtually nobody pays MRSP, street prices will be lower. And if we can pool a big order, we can aim right at wholesale price -- my guess will be around 1/2 of MRSP.