Thanks Kindhornman and bare for exposing these truths.
As I said, it is maybe enough talk and now we want some braves that actually build something with big coaxials...and lets see if they can return to multi(point)-drivers...
Some options:
Buy Audio Nirvana 15" coaxial and use a single cap to a high crossover point to tweeter.
Buy a Tannoy or its "imitators" and build a big enclosure, either a ported or horn loaded, but make it big
. I own Beyma 15KX coaxials and for years I wanted to "upgrade" to PAudio big, macho coaxials (Beyma has something like a waveguide) but then I varnished the woofer cone with Dammar and my desire to upgrade got away...which reminds me that this month I have to put the second hand of varnish on them!
Another option is building a monster trapezoidal speaker with a 12" or 15" coaxial and putting it above a sibling trapezoidal box with a 15" or 18" to reinforce the bass, all activelly triamped, something like a Kingdom
yeah, I would do it if I weren't into big horns.
Have fun.
M.
As I said, it is maybe enough talk and now we want some braves that actually build something with big coaxials...and lets see if they can return to multi(point)-drivers...
Some options:
Buy Audio Nirvana 15" coaxial and use a single cap to a high crossover point to tweeter.
Buy a Tannoy or its "imitators" and build a big enclosure, either a ported or horn loaded, but make it big
. I own Beyma 15KX coaxials and for years I wanted to "upgrade" to PAudio big, macho coaxials (Beyma has something like a waveguide) but then I varnished the woofer cone with Dammar and my desire to upgrade got away...which reminds me that this month I have to put the second hand of varnish on them!Another option is building a monster trapezoidal speaker with a 12" or 15" coaxial and putting it above a sibling trapezoidal box with a 15" or 18" to reinforce the bass, all activelly triamped, something like a Kingdom
yeah, I would do it if I weren't into big horns.Have fun.
M.
Been done Max. The P.Audio 18" coax on open baffle. It's amazing.
Manzanita Audio Solutions . Manzanita MBBC
Manzanita Audio Solutions . Manzanita MBBC
the altec biflex and tannoy concentrics seem like the best ideas to me. Ive never heard either. I envision an inner roll surround between centre cone and the outer ring of the woofer. In the same way i like the dual concentrics. Both diaphragms moving in unison. Its got to be the best way. A CD firing thru a vented pole is a simple botch if you ask me. Same for dodgy tiny segmented horn attachments and domes on stalks...even dual VC biflex type ideas arent ideal, unless both have very little excursion.
Have a look at the design of Audio Nirvana 15" coaxial. It has a whizzer that is shaped like like a beautiful waveguide. The photos don't do justice of how good it actually is
Are you speaking from experience, or just guessing? How many of these have you worked with?
You're welcome, Max.Thanks Pano.
I think this speaker almost made SY like open baffles, almost.
Hi Steven,
I agree with most of your statements to the coaxial drivers, although you forgot to mention for type 2 that the high frequency response is highly modulated by the cone. It is quite easy to circumvent: use a separate woofer and do not crossover too low. Result is a fairly good 3-way, but the polar pattern is not always good, depending on the coaxials cone shape, surround, tweeter coupling to the cone and so on.
Here I disagree. Many of these designs have drawbacks, of course, but that's why I wanted you to take closer look on the Geithains.
Although very popular with audiophiles, time alignment is not that important in speaker design. Especially with such coaxials, how many microseconds is the woofer delayed?
The polar response can be good, too, when choosing the crossover frequencies carefully. Remember, many of the car audio coaxials are 3-way, so it is possible to build a very wide dispersion speaker (the main drawback with these are their poor overall performance).
Cavity resonances can happen, but again, this depends on the crossover frequency. Choose it low enough, and you won't have that problem (if 3-way coax).
Let's have a look at the Geithain RL 901 K. It is a mains monitor, so for listening distances beyond 3 meters. In this distance, there is no need for a real coax, because the listening distance is big compared to the distance of midrange and tweeter. However, if you choose to place the woofer below midrange, and crossover fairly high to improve maximum level (the RL 901 K crosses at 550 Hz and 2.8 kHz), then their might be some vertical polar and localization problems, even at big distances. That's why the mids/highs are placed in front of the woofer (it is a 400 mm woofer).
The plate in front of the woofer does affect the polar response of the woofer, but at which frequencies? I know measurements of the Geithains, and there is definitely no such effect (or, at least, not so obviously visible).
The same is the damping of sound output. This is a 400 mm monster, the midrange is a 125 mm type. Come on, is this really a problem?
Cavity resonances? See above. No problem when you crossover sufficiently low.
The size and shape of the front plate is carefully designed to improve the polar pattern of midrange and tweeter. The tweeter will have a distinct peak in the diffuse field at 3 kHz. This helps, according to Geithain, for naturalness in the far field. This might be disputable, but is a hallmark of the far field monitors of Geithain.
So, don't judge too early on the Geithains. They are well engineered, and have a high reputation, at least in Germany.
Best
Baseballbat
I agree with most of your statements to the coaxial drivers, although you forgot to mention for type 2 that the high frequency response is highly modulated by the cone. It is quite easy to circumvent: use a separate woofer and do not crossover too low. Result is a fairly good 3-way, but the polar pattern is not always good, depending on the coaxials cone shape, surround, tweeter coupling to the cone and so on.
Here I disagree. Many of these designs have drawbacks, of course, but that's why I wanted you to take closer look on the Geithains.
Although very popular with audiophiles, time alignment is not that important in speaker design. Especially with such coaxials, how many microseconds is the woofer delayed?
The polar response can be good, too, when choosing the crossover frequencies carefully. Remember, many of the car audio coaxials are 3-way, so it is possible to build a very wide dispersion speaker (the main drawback with these are their poor overall performance).
Cavity resonances can happen, but again, this depends on the crossover frequency. Choose it low enough, and you won't have that problem (if 3-way coax).
Let's have a look at the Geithain RL 901 K. It is a mains monitor, so for listening distances beyond 3 meters. In this distance, there is no need for a real coax, because the listening distance is big compared to the distance of midrange and tweeter. However, if you choose to place the woofer below midrange, and crossover fairly high to improve maximum level (the RL 901 K crosses at 550 Hz and 2.8 kHz), then their might be some vertical polar and localization problems, even at big distances. That's why the mids/highs are placed in front of the woofer (it is a 400 mm woofer).
The plate in front of the woofer does affect the polar response of the woofer, but at which frequencies? I know measurements of the Geithains, and there is definitely no such effect (or, at least, not so obviously visible).
The same is the damping of sound output. This is a 400 mm monster, the midrange is a 125 mm type. Come on, is this really a problem?
Cavity resonances? See above. No problem when you crossover sufficiently low.
The size and shape of the front plate is carefully designed to improve the polar pattern of midrange and tweeter. The tweeter will have a distinct peak in the diffuse field at 3 kHz. This helps, according to Geithain, for naturalness in the far field. This might be disputable, but is a hallmark of the far field monitors of Geithain.
So, don't judge too early on the Geithains. They are well engineered, and have a high reputation, at least in Germany.
Best
Baseballbat
Pano, I am certainly NOT speaking from experience. I am merely postulating from my POV and from the design schematics that i have seen, and stating which types are IMO the most compromised. I believe the Tannoy dual concentric has the most ideal design, and also the dual VC dual diaphragm 'section' types. Biflex right? I havent heard most of the types mentioned, merely commenting on the relative flaws in each, as i see them. Nothing to become defensive of.
The market maybe happy (who cares?) but I'm not ! For a standard multiway speaker with treble on the top and bass on the bottom it is fairly easy for me to hear sounds coming from different heights according to frequency bands each element is playing. Unless the speaker is vertically symmetric. But making fully vertical symmetric means speaker become extreme in height. Coaxial can relax this situation.
Of course all this is due to the curse of too much of direct sound !
More into diffuse field and no such problems occur. - Elias
Greetings from Serbia!
I am using 10 inch Tannoy K2558 professional Dual Concentric kit from the late 80s in a 30 litre vented box. This driver uses ferrite magnet and pepper pot waveguide on compression HF driver and Sync Source passive module for time alignment . Unlike Tannoy home models from the same period, factory fitted xovers use film and foil caps which you rarely see today even in indecently overpriced high end products. For me, this is the most elegant solution for coaxials with compression horn HF drivers. I can not say that I hear discontinuities at crossover region at 1.2 kHz and if you like higher SPLs at home this combination is unsurpassed. Earlier Tannoys with Alnico magnets sound even better but I think that it is not consequence of better natural phase alignment but of less second harmonic distortion. Alnico magnets are famous for much lower 2nd harmonic. This problem with ferrite magnets is usually solved with symmetrical magnetic field geometry as in some JBLs and ScanSpeaks. In practice, the dispersion of this Dual Concentric is not worse than dispersion of other high quality loudspeakers using discrete drivers. In fact, in mid field I think it is even better and the sound stage is more coherent than with ordinary loudspeakers.
I admit that I never tried to disconnect SyncSource module and listen loudspeakers without it, if it is true that module messed up some things.
I am using 10 inch Tannoy K2558 professional Dual Concentric kit from the late 80s in a 30 litre vented box. This driver uses ferrite magnet and pepper pot waveguide on compression HF driver and Sync Source passive module for time alignment . Unlike Tannoy home models from the same period, factory fitted xovers use film and foil caps which you rarely see today even in indecently overpriced high end products. For me, this is the most elegant solution for coaxials with compression horn HF drivers. I can not say that I hear discontinuities at crossover region at 1.2 kHz and if you like higher SPLs at home this combination is unsurpassed. Earlier Tannoys with Alnico magnets sound even better but I think that it is not consequence of better natural phase alignment but of less second harmonic distortion. Alnico magnets are famous for much lower 2nd harmonic. This problem with ferrite magnets is usually solved with symmetrical magnetic field geometry as in some JBLs and ScanSpeaks. In practice, the dispersion of this Dual Concentric is not worse than dispersion of other high quality loudspeakers using discrete drivers. In fact, in mid field I think it is even better and the sound stage is more coherent than with ordinary loudspeakers.
I admit that I never tried to disconnect SyncSource module and listen loudspeakers without it, if it is true that module messed up some things.
Thanks Mondo. Reading your sig line again, it makes more sense.
There are a lot of speaker designs that I might look at and think, "Oh man, that's gotta be awful" but they ain't. A walk around any large audio show will teach you that very fast. Of course the reverse is sometimes true - what looks great may not sound it.
I've heard a lot of coax drivers and worked with a few. They have their challenges, but until you've actually worked with them, it's hard to say what. The challenges are not immediately obvious just looking at them.
Biflex: To me this means the Altec drivers with the ridge in them. A sort of two part cone. It does work OK to extend the HF over what it would be with a conventional cone, but I wouldn't use them full range, too dull. A true coax has a real HF driver built in and needs a crossover.
from my limited knowledge of concentrics i would say that the tannoys with integral tweeter membrane and 'induced' drive of the tweeter, are my faves. It just appears to me like they are the closest to a single diaphragm. They avold the need for a 1 or 2 inch tunnel, they are perhaps better time aligned, though whether that really matters is not for me to argue. My thinking is just that its closest to the ideal of a single driver or fullrange. This is, of course the ultimate goal of coax or concentric drivers.
A modified biflex idea with dual VC and 2 part cones also seems a good approach. I never like the sound of a bare CD, and i doubt id enjoy a CD with a 3inch or longer tube attached to it.
A modified biflex idea with dual VC and 2 part cones also seems a good approach. I never like the sound of a bare CD, and i doubt id enjoy a CD with a 3inch or longer tube attached to it.
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Looking at a lot of coax drivers with the big CD hanging off the back and a horn throat going thru the woofer, one might wonder how the two drivers could ever be in phase. The HF sits too far behind the LF.
Happily, with the right crossover point the phase of the woofer will shift right back to the diaphragm of the tweeter. Phase match achieved. It all kinda works out.
Happily, with the right crossover point the phase of the woofer will shift right back to the diaphragm of the tweeter. Phase match achieved. It all kinda works out.
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