PaulW over at the
Large midrange for OB
thread now uses a quad midrange array of 6.5" drivers (in open baffle with damped backwave) to control directivity in the midrange, and a waveguide above. I use a 15" up to 320 Hz and a 6.5" from 320 to 2000 Hz, both in open baffles, what I still lack is a waveguided HF section. Now, these solutions might not achieve ideal or perfect "Geddes waveguide" type off axis curves in the midrange. But I still believe they offer significant benefits compared to a monopole bass slowly narrowing in directivity. The overall power response match between HF and midbass/bass is better, and well, they *are* more directional below 800 Hz than monopoles. Not as controlled as a waveguide, because the acoustic elements involved have hard to manage idiosyncrasies (baffle foldback, rear driver frequency response aberrations etc), but much easier to achieve than a WG at these frequencies. Active crossovers and multi-amping give the required freedom for crossovers and filtering, that may appear complex but somehow I got used to cobble together active filters and it doesn't bother me...
Large midrange for OB
thread now uses a quad midrange array of 6.5" drivers (in open baffle with damped backwave) to control directivity in the midrange, and a waveguide above. I use a 15" up to 320 Hz and a 6.5" from 320 to 2000 Hz, both in open baffles, what I still lack is a waveguided HF section. Now, these solutions might not achieve ideal or perfect "Geddes waveguide" type off axis curves in the midrange. But I still believe they offer significant benefits compared to a monopole bass slowly narrowing in directivity. The overall power response match between HF and midbass/bass is better, and well, they *are* more directional below 800 Hz than monopoles. Not as controlled as a waveguide, because the acoustic elements involved have hard to manage idiosyncrasies (baffle foldback, rear driver frequency response aberrations etc), but much easier to achieve than a WG at these frequencies. Active crossovers and multi-amping give the required freedom for crossovers and filtering, that may appear complex but somehow I got used to cobble together active filters and it doesn't bother me...
Whether a certain directivity is optimal for all room conditions or not still needs to be tested. While CD can give a good sense of stage width and depth, the image still will shift as one moves sideways. Properly designed wave guides to have the advantage of smoothing off-axis pressure transition.
gedlee said:
Not quite. My point was, use optimal where feasible (true CD using waveguides at frequencies where size is acceptable), and "almost as good as" (dipoles, cardioids) where waveguided CD not acceptable due to size.
If you merge a waveguided HF section with a monopole woofer that transits into its directional range, you get a smoothly narrowing directivity. You must, however, get a power resonse that is tilted towards the low end this way. Depending on application this may or may not be an issue, you discuss dipoles and conclude that the effort is not worth the cost for your aims and I'm perfectly fine with that.
But wouldn't you agree that the optimal arrangement would be one where the radiation patterns match at *all* frequencies, and where the power response is flat as well? Dipoles can't get you there to perfection, but they do go a long way, especially in getting the power response down. And the cost (excursion) does not have to be too large as long as you don't go into subwoofer territory. My 24" wide 7" deep open baffles lose me just 6 dB in output between the points of output equal to a monopole on-axis (ca. 140 Hz), and woofer cutoff (ca. 70 Hz). In a domestic situation using a 15" pro woofer that's acceptable to me.
"But wouldn't you agree that the optimal arrangement would be one where the radiation patterns match at *all* frequencies, and where the power response is flat as well? Dipoles can't get you there to perfection, but they do go a long way, ..."
You're talking about dipoles using uses direct radiators, right?
In which case the directivity is not constant, it varies continuously with freq.
You're talking about dipoles using uses direct radiators, right?
In which case the directivity is not constant, it varies continuously with freq.
As I said "Dipoles can't get you there to perfection, but they do go a long way".
As far as I know any kind of transducer will achieve any desired behaviour only within a certain bandwidth. Waveguides too. So, we're back to square one, left with the decision as to what trade-offs we find acceptable and what parameters we believe are most important to get "as right as possible" (and I think Earl would agree with that last statement).
Again I am not putting up waveguides "against" dipoles. But below a certain frequency waveguides become impractical in size. As Earl said in terms of image we may not have a problem below say 800 Hz. But in terms of total radiated power into the room we still do have a problem and if so desired it is fixable, by dipoles, or cardioids.
As far as I know any kind of transducer will achieve any desired behaviour only within a certain bandwidth. Waveguides too. So, we're back to square one, left with the decision as to what trade-offs we find acceptable and what parameters we believe are most important to get "as right as possible" (and I think Earl would agree with that last statement).
Again I am not putting up waveguides "against" dipoles. But below a certain frequency waveguides become impractical in size. As Earl said in terms of image we may not have a problem below say 800 Hz. But in terms of total radiated power into the room we still do have a problem and if so desired it is fixable, by dipoles, or cardioids.
Lots of statements some correct some not correct.
MBK - there actually is no theoretical bandwidth limitation on the diretivity of a waveguide and even in practice it is way beyond any other technique.
"But wouldn't you agree that the optimal arrangement would be one where the radiation patterns match at *all* frequencies, and where the power response is flat as well?"
I would call that perfect, but not feasible which makes it less than optimal. Semantic perhaps, but from my point of view a very big distinction.
If you read my work you will see that I propose very high sound absorption at LFs which offests the higher power response. Its all one big design, room, speakers, listening space - you have to design for the total system and not just one piece of it.
I have looked at dipoles and cardioid's (there is a whole section in my book on cardioid's) fro exactly the reasons that you state. They are just not that easy to do correctly. They are very easy to do marginally - "almost as good".
To repeat what I said before, to make dipoles and cardiods work as you suggest requires several stages from the lowest frequency to the midrange. Probably one from 70 Hz to 140 Hz, another from 140 hz to maybe 300 hz, and that still leaves a big gap to fill with yet a third system before a reasonable waveguide can be matched. I've done these models, it just is not that attractive to me because of the size and complexity. The ESP12 is about 20" high by 13" wide and 8" deep. The response is almost as well controlled as the ESP15. In terms of trade offs this is by far the best that I have seen.
MBK - there actually is no theoretical bandwidth limitation on the diretivity of a waveguide and even in practice it is way beyond any other technique.
"But wouldn't you agree that the optimal arrangement would be one where the radiation patterns match at *all* frequencies, and where the power response is flat as well?"
I would call that perfect, but not feasible which makes it less than optimal. Semantic perhaps, but from my point of view a very big distinction.
If you read my work you will see that I propose very high sound absorption at LFs which offests the higher power response. Its all one big design, room, speakers, listening space - you have to design for the total system and not just one piece of it.
I have looked at dipoles and cardioid's (there is a whole section in my book on cardioid's) fro exactly the reasons that you state. They are just not that easy to do correctly. They are very easy to do marginally - "almost as good".
To repeat what I said before, to make dipoles and cardiods work as you suggest requires several stages from the lowest frequency to the midrange. Probably one from 70 Hz to 140 Hz, another from 140 hz to maybe 300 hz, and that still leaves a big gap to fill with yet a third system before a reasonable waveguide can be matched. I've done these models, it just is not that attractive to me because of the size and complexity. The ESP12 is about 20" high by 13" wide and 8" deep. The response is almost as well controlled as the ESP15. In terms of trade offs this is by far the best that I have seen.
What about this speaker?
Dipole woofer, cardioid midrange, waveguide tweeter.
Looks interesting.
Betto
An externally hosted image should be here but it was not working when we last tested it.
Dipole woofer, cardioid midrange, waveguide tweeter.
Looks interesting.
Betto
gedlee said:
I completely agree here. Without active filters and multi-amping, and a fair deal of measurements with diverse methods and means you are getting "nice" but only "almost". It's very easy to cobble together an open baffle system that sounds "OK", it takes a while to make it sound great. To confess, I spent 5 or 6 years in several implementations with mine to be satisfied, and I still lack the waveguide HF section that would make it truly consistent as a design. But this is a hobby, I enjoy building as much as listening, mine may have room for improvement, but well, they're mine!
gedlee said:
Actually I am really curious to see/hear your ESP line in action.
Betto,
I understand this is the new Gradient? I suppose they have a lot of experience but somehow this seems an effort in a) design (possibly over function) and b) possibly trying to do one thing very well while doing other things not very well.
The dipole woofer has very little separation distance so it is losing a lot of power. The null or quasi null lobe from the woofer points at the listener. In terms of lateral bass mode excitation (see Griesinger's discussion) this may be a good thing but I can't imagine how the crossover region would have any decent response characteristics with such a setup. And mid and HF section pointing upwards while ostensibly directional in intent, well I don't see the point; for all I know floor reflections appear more benign and psychoacoustically beneficial (if one has to have reflections) than ceiling reflections. Also, rugs are easier to place than ceiling panels.
But yes it looks great and who knows maybe I am missing something here.
I understand this is the new Gradient? I suppose they have a lot of experience but somehow this seems an effort in a) design (possibly over function) and b) possibly trying to do one thing very well while doing other things not very well.
The dipole woofer has very little separation distance so it is losing a lot of power. The null or quasi null lobe from the woofer points at the listener. In terms of lateral bass mode excitation (see Griesinger's discussion) this may be a good thing but I can't imagine how the crossover region would have any decent response characteristics with such a setup. And mid and HF section pointing upwards while ostensibly directional in intent, well I don't see the point; for all I know floor reflections appear more benign and psychoacoustically beneficial (if one has to have reflections) than ceiling reflections. Also, rugs are easier to place than ceiling panels.
But yes it looks great and who knows maybe I am missing something here.
Member
Joined 2003
Here is the "quad" midrange MBK referenced. The concept is to achieve the directivity of a 15+" with the energy storage characteristics of a smaller driver. This isn't new as I've seen similar designs from Europe...the only significant difference here is the use of a heavy wool felt half-cylinder to damp the rear-wave for a smoother transition to a forward firing waveguide (felt is not shown in these photos). This midrange is used with a BMS4552ND in either a DDS Eng-1 or PHL/MSC/PE 12" waveguide.
The quad mids work well, but I also heard the Emerald Physics 2x15" dipole + waveguide do a great job in an impossibly small hotel room at RMAF...so there are multiple paths to improved room interaction.
The quad mids work well, but I also heard the Emerald Physics 2x15" dipole + waveguide do a great job in an impossibly small hotel room at RMAF...so there are multiple paths to improved room interaction.
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