MJL21193 said:
Try and raise the xo point and see what happens 😉 and maybe use a ribbon instead
MJL21193 said:
NO, that is not what I said to RCW. I objected to his assumption that a dome in a conical horn was the "optimum" approach. That I don't agree with. But a dome in a conical horn is far far better than a dome in a baffle.
I know that its not your fault, but it is so very difficult when people misunderstand what is said and then I take heat for it. RCW's discussion and mine was on a fairly small point, nothing that would completely invalidate what he suggests. I just believe that there are better ways to do things. But as I told him, in one of my designs I actually did use a dome tweeter on a conical horn just as he suggests - because it is dirt cheap, not because it is the optimum.
So I could play with a dome tweeter version to see how I like the results, then if I did, I'd go to a compression driver.
For me, the construction is not the hard part, so I can easily spare a few hours to mock up a viable example.
Here's a quick section view. Is this approximately correct?
For me, the construction is not the hard part, so I can easily spare a few hours to mock up a viable example.
Here's a quick section view. Is this approximately correct?
Attachments
Why when you can make it better?
Or better yet, use a compression driver that can play lower, has less distortion, and more output.
Or better yet, use a compression driver that can play lower, has less distortion, and more output.
gedlee said:
I realize that the shorter distance would come about with the long axis horizontal. What I was thinking is that the large axis would provide a more narrow polar response than the narrow axis, and therefore you'd want the long axis vertical to narrow the vertical response.
If the long axis has a wider response, is it due more to the angle of the waveguide?
A point about dome tweeters that Earl made is that various makes of them have domes of different curvatures.
Metal domes are generally too flat for 80-90 degree waveguides, and ideally a transition region to "bend" the wavefront onto a different curvature should be used.
With the D25AG I put a 50mm. hole saw through the face plate and provided the waveguide mounting plate with a spigot that fits into the hole and clears the center of the surround by a half millimeter.
The seas 29mf has a rated .5mm. peak diaphragm excursion and I modeled it on winisd.
With a biquad at 1500Hz. and a fourth order L-R filter at the same frequency it can produce peaks of 113db. with a 90Watt input and the excursion has a maximum of 0.27mm.
In a wave guide you can expect at least 5db. more output bellow the mass corner, meaning in the average room a pair can give short peaks of 120db. at only half the rated linear excursion, that should be about enough for anybody.
rcw
Metal domes are generally too flat for 80-90 degree waveguides, and ideally a transition region to "bend" the wavefront onto a different curvature should be used.
With the D25AG I put a 50mm. hole saw through the face plate and provided the waveguide mounting plate with a spigot that fits into the hole and clears the center of the surround by a half millimeter.
The seas 29mf has a rated .5mm. peak diaphragm excursion and I modeled it on winisd.
With a biquad at 1500Hz. and a fourth order L-R filter at the same frequency it can produce peaks of 113db. with a 90Watt input and the excursion has a maximum of 0.27mm.
In a wave guide you can expect at least 5db. more output bellow the mass corner, meaning in the average room a pair can give short peaks of 120db. at only half the rated linear excursion, that should be about enough for anybody.
rcw
rcw said:
Hi RCW,
This is not a criticism of your idea, but just some food for thought. You can pump 90 watts into a dome tweeter for a short duration, or you can furnish an 108dB sensitive compression driver 16 watts all day long. Both equal 120dB (tweeter per your analysis). However, the compression driver will have multiples less distortion and will not go up in a poof of smoke. Why chase down this path? If its just in the spirit of DIY, then that's cool. It just doesn't seem a logical path to me. Once again, no offense intended, just sharing ideas here.
Rgs, JLH
rcw said:
... reminds me of that '640K ought to be enough for anybody' quote.
Above everything here, we are talking about the qualities and properties of the waveguide. Maximum sound pressure is not one that seems to be lacking in any way (as used on the Summa speakers), and 'about enough' is certainly not something that I have in mind.
It is certainly interesting to see what does and does not work in a waveguide though.
hi Earl
i don't know it this is offtopic, but something i would like to know your opinion. I had a 300hz tractrix horn with BMS 4592nd compression driver in the past, which was covering all the way up to 20khz. The treble was not sound right to me . Thinking about it, i can immagine, that the reason was HOM. Now i used a Radian 8" coax driver for a project, with a 1" compression driver covering from 1,2khz up, for a small room, about 4m x 4m . It has a 90 degree opening like your waveguide, but is not OS. Well, the treble is simply perfect . I did't here anything, that might bother me because of HOM. Since it is a point source, the sound is so coherent, no phase shift, no detection of the source, the sound simply flows in the room. If it would be 2 channels, with a woofer and a wave guide above, certainly the source would be detectable, and the sound not so coherent as with a coax. What makes you prefere the Summa design to a design with a coaxial driver ? I mean , the advantage of a point source is not insignificant, while i didn't bother with HOM, and directivity might be the same as your OS.
Angelo
i don't know it this is offtopic, but something i would like to know your opinion. I had a 300hz tractrix horn with BMS 4592nd compression driver in the past, which was covering all the way up to 20khz. The treble was not sound right to me . Thinking about it, i can immagine, that the reason was HOM. Now i used a Radian 8" coax driver for a project, with a 1" compression driver covering from 1,2khz up, for a small room, about 4m x 4m . It has a 90 degree opening like your waveguide, but is not OS. Well, the treble is simply perfect . I did't here anything, that might bother me because of HOM. Since it is a point source, the sound is so coherent, no phase shift, no detection of the source, the sound simply flows in the room. If it would be 2 channels, with a woofer and a wave guide above, certainly the source would be detectable, and the sound not so coherent as with a coax. What makes you prefere the Summa design to a design with a coaxial driver ? I mean , the advantage of a point source is not insignificant, while i didn't bother with HOM, and directivity might be the same as your OS.
Angelo
pooge said:
Yes, the angle of the walls determines coverage angle if 1) the waveguide is large enough 2) the frequency is high enough such that there is more than a wavelength across the mouth. Below this frequency, the polar response gets very complicated and hard to predict.
rcw said:
We don't agree on this point as I would caution that while you may not burn up the dome, thermal compression will be quite evident at these levels. The compression driver will still be idling.
angeloitacare said:
These comments are all subjective based on some causual listening and they are being compared to a situation that you have not heard. I have heard both and I don't find your comments correct. "the treble is simply perfect " - these kinds of superflous statements are always disturbing to me.
I would rather use a "optimum" waveguide, even if it can't be coaxial, than the highly compromised waveguide required for coaxial mounting. In my experince the tradeoffs are not good ones - the treble is simply "not" perfect.
hello Earl
my comments come not as a scientist, as you are, but based on what counts, which are the normal subjective listening experiences in a home environment . I know the setbacks of more than one source, it can be perceived clearly when sound comes from more than one source, integration is never as perfect, as from one point source. The treble is perfect for me, when i am satisfied and pleased with most kind of music. Of course, this is a personal subjective opinion, which others might not agree with.
the quest remains which trade-off is worse, two different sources, or a highly compromised waveguide, which does not aloud a " perfect " performance .
Angelo
Well if your minds made up then there is no point in any further discussions I guess.
And what counts is not what one person thinks, like you, but what a group of unbiased people think like Summa Recomendations
And what counts is not what one person thinks, like you, but what a group of unbiased people think like Summa Recomendations
gedlee said:
I must also admit that I wont bet my money on a coax either, though I haver never heard one
