What reelections are you referring to here? Reflections off of the driver/horn interface?
David Gunness describes the reflections within the phase plug in this 2005 white paper:
https://www.fulcrum-acoustic.com/wp...ker-transient-response-with-dsp-2005.pdfAudio Engineering Society
"The openings in a phase plug are arranged in such a way that, from any point on the diaphragm, the path to an opening is relatively short. The designer of the compression driver intends for all of the sound power produced within the driver to leave via the “nearest exit”. However, a significant fraction of the sound energy arriving at a phase plug opening will either continue past it or reflect back from it; in either case arriving later at other phase plug slots where the sound is divided again, ad infinitum. Rather than a single acoustical impulse, the response exhibits a decaying sequence of impulses. "
Figure 3.1.1: Schematic Compression Driver Cross- Section, Showing Transmission Line “T”
Acoustical horn resonances and mechanical radial resonances in loudspeaker cones also may be corrected with pre-conditioning filters.
Art
https://www.fulcrum-acoustic.com/wp...ker-transient-response-with-dsp-2005.pdfAudio Engineering Society
"The openings in a phase plug are arranged in such a way that, from any point on the diaphragm, the path to an opening is relatively short. The designer of the compression driver intends for all of the sound power produced within the driver to leave via the “nearest exit”. However, a significant fraction of the sound energy arriving at a phase plug opening will either continue past it or reflect back from it; in either case arriving later at other phase plug slots where the sound is divided again, ad infinitum. Rather than a single acoustical impulse, the response exhibits a decaying sequence of impulses. "
Figure 3.1.1: Schematic Compression Driver Cross- Section, Showing Transmission Line “T”
Acoustical horn resonances and mechanical radial resonances in loudspeaker cones also may be corrected with pre-conditioning filters.
Art
Kyle, awesome post, thank you for sharing your experience and taking the time to provide the links.
Yep. I've looked into Fulcrum Acoustic's processor settings for Q-sys, for a number of their speaker models. First thing that jumps out is the use of only 384 taps, which clearly precludes any kind of heavy handed impulse inversion. Also noticed the FIR impulse peak is generally before center, and the presence of the IIR filters in the containers along with xovers.Without going into too much detail, they aren’t using simple IR inversions from an acoustic measurement. That simple inversion process is easy to do, and it makes a pretty graph but rarely a good sounding speaker. Unless you stay fixed in a very small physical position, never turn it up (or down), the parts don’t age
I think disappointing overall results from tuning to a spot is what has caused a lot of folks to dismiss FIR.
Cool. That's getting to dig deep in.
It's been educational for me to run transfers on FA's Q-sys containers, and ponder them against the speakers they go with.
It's easy to see that a manufacturer needs to measure lots of devices given the prospect of unit to unit variability. It makes sense that a speaker model would be best tuned to an average of a number of units, just like a single box is best tuned to a spatial average.
It seems to me this is where DIY has a little advantage, and can safely tune a specific box to tighter specs than manufacturers can.
I had the good fortune to briefly meet Dave G at a trade show and tell him I was trying to copy his patent for DIY work. He laughed and was friendly and generous. At the time I was trying to understand his patent using a coax CD, one section as the driver and the other as a microphone to measure returning discontinuities. Told me that would work.
I kept at it for a while, making a filter for horn reflections back to the throat (my version of 'preconditioning' lol), putting that filter in place and then making a normal set of far fields, and multiplying the convolutions. Can't say I really heard/measured any difference than from simply building a single FIR filter straight from the far-field set.
Probably my lack of knowing how to optimize the 'preconditioning'
+1 use it all the time
It really does make the integration so much easier. I often wonder if that isn't the prime factor with the good results i feel i'm getting.
Ditto with regards to what I think I hear, and no chance to do do double blind.
Yep. Completely agree with getting minimum phase right first before attempting FIR...with one exception.
(I think the minimum phase stuff are the only EQ corrections that should be made to the drivers.)
The one exception I'd suggest is to use complementary linear phase xovers. So much easier than IIR, when learning to integrate drivers. And safe.
Heck, if lin phase xovers were the only use of FIR, FIR is more than worth it in my book...especially for a beginner.
Forgive how blurry this image is - it's cropped from a low-resolution scan of an old EAW magazine advert - but think the effect of these phase plug reflections is a little more obvious in a coloured Wavelet plot than in the greyscale version on the AES paper:
https://patents.google.com/patent/US20180234758A1/en?assignee=elettromedia&oq=elettromedia
For the sake of completeness, here is the other pair of before & after wavelet plots for the original Gunness cone resonance filter:
These are acoustic measurements, but the filters are generated from two-port models, as shown in the Di Cola paper I linked previously:
Hi camplo,
it seems that this issue is going on... When do you finally hook up your equipment and if it is only for a quick and dirty assessment and report about the sound impressions? All the things you insisted to say us that such an e-trac horn is better than whatever. We wait for your listening report and not endless of confusing "measurements" and pictures.
You seem to be very different from the average user who can hardly wait to use new equipment and just listen to music instead of talking about pseudo technology.
I said that? Quote me
"When do you finally hook up your equipment and if it is only for a quick and dirty assessment and report about the sound impressions?"
I've done this already for the mid and sub woofer....I also did a brief comparison of the horn vs mid within a small range of 300hz to 800hz or so.
I guess I could try to give it another go... anything specific you want to know?
The most important thing to me was that the Horn seemed to have more direct energy and the midwoofer seemed to excite the room more... I made this conclusion at a mere ~16" listening distance... I didnt think it was something to tout strongly since I didn't attempt to create similar positioning...
This horn is huge and I have no idea how to mount it 🤣
The horns HF is wider than I thought it would be, to my ear.... standing above it, shuffling from side to side. The thing about HF being limited to approximately, eye sight of the throat, seems to be true
"You seem to be very different from the average user who can hardly wait to use new equipment and just listen to music instead of talking about pseudo technology."
The mid and sub experience... the small amount of demoing the horn... its turning out as I predicted concerning the direct energy. The horn is better than I thought it would be and I wonder if I'll turn into one of those guys with the giant snail horns🤣.... I'm sure @docali horns are better.... but the point is if you don't have a large horn, imo, you are missing out! It was @mitchba comment that inspired me... he said the one thing he wished had, was a bigger horn.... he already has TMM 15's.... hes a drummer and sound engineer...so am I.... maybe it's the drumming experience? We are direct energy junkies 😃
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You selected this e-trac horn. What else was the reason?
Not really. iirc you were flooded with designs but we told you about the restrictions of those horns and of them was called by me as Jericho - think about why.
After all these months of planning and waiting. Really? lol
and forget about to listen to music? Mmmmhhh, why not simply put the horn alone fullrange and listen to it? Just use your crossover slope and make the driver flat with DSP and just listen music with this combo. This will tell very much about the sound of your horn. Just listen to voices, Ella, Nat, Elvis, etc. and listen if it sounds natural.
1/12 smoothing if I recall correctly
17.5" above center in Red
8" below center in blue
17.5 to the right in green
The above is without a XO and has eq on the top end. This voicing measured more neutral...outside, than what I get here in this crowded living room space.
The sound is very neutral...I can hear into the mix very well with these.. I listened first with the 300hz XO and was moved by the natural presentation of the music on each reference song I chose, Of course, I chose songs that I knew for a long time, and the voices sound amazing. The Victor Wooten bass solo sounded amazing, Then after I decided to listen without XO, it just got better lol. I had the cliche experience of hearing details I did not notice before etc etc....About 2hrs of straight listening btw.....I've things to do lol! But as a musician and music lover it can be easy to fall into a session like this especially when everything is so revealing. I definitely heard aspects of the songs that I feel would not be so easily conveyed by other systems....And I believe it has to do with direct energy.....the in your face-ness that can happen.....its just a large dose of direct energy drowning out the airiness of the room. Direct vs reverb, thats all.
I wonder what an even bigger horn, with a lower turning, would sound like,....Maybe I will try a 50hz elliptical type horn.....The truncated mouth seems to be no harm in the measurements or my ears, but I do listen very close,... The bigger the mouth, the more forgiving. right? I wonder exactly how big a 50hz elliptical tractrix would be and what it would sound like on the axi....Can a horn be too big for a driver?
This LR48 at 178 business seems pretty cool. I'll have to play around some more... A ways to go.
I've had similar experiences playing with just the woofer section. The mid blends with the subwoofer very well. Much better than it would appear judging by the physical distance. The horn in my opinion will provide clarity in the top range but the question is how will it sum sitting above the woofer, at such close distance of listening. If I could get the Axi playing low enough in a big enough horn, I could cross to the PPSL 18"s and make a MTM. That would be something to see lol.
I'll get there.
As far as why did I choose this horn? To experiment with? Its big, and it was available as a completely designed horn someone claimed to be ready to produce....So I could have something in case my manufacturing goals fell through....something like that. Now I am only interested in building an even bigger horn or at least learning why it wouldnt work.
17.5" above center in Red
8" below center in blue
17.5 to the right in green
The above is without a XO and has eq on the top end. This voicing measured more neutral...outside, than what I get here in this crowded living room space.
The sound is very neutral...I can hear into the mix very well with these.. I listened first with the 300hz XO and was moved by the natural presentation of the music on each reference song I chose, Of course, I chose songs that I knew for a long time, and the voices sound amazing. The Victor Wooten bass solo sounded amazing, Then after I decided to listen without XO, it just got better lol. I had the cliche experience of hearing details I did not notice before etc etc....About 2hrs of straight listening btw.....I've things to do lol! But as a musician and music lover it can be easy to fall into a session like this especially when everything is so revealing. I definitely heard aspects of the songs that I feel would not be so easily conveyed by other systems....And I believe it has to do with direct energy.....the in your face-ness that can happen.....its just a large dose of direct energy drowning out the airiness of the room. Direct vs reverb, thats all.
I wonder what an even bigger horn, with a lower turning, would sound like,....Maybe I will try a 50hz elliptical type horn.....The truncated mouth seems to be no harm in the measurements or my ears, but I do listen very close,... The bigger the mouth, the more forgiving. right? I wonder exactly how big a 50hz elliptical tractrix would be and what it would sound like on the axi....Can a horn be too big for a driver?
This LR48 at 178 business seems pretty cool. I'll have to play around some more... A ways to go.
I've had similar experiences playing with just the woofer section. The mid blends with the subwoofer very well. Much better than it would appear judging by the physical distance. The horn in my opinion will provide clarity in the top range but the question is how will it sum sitting above the woofer, at such close distance of listening. If I could get the Axi playing low enough in a big enough horn, I could cross to the PPSL 18"s and make a MTM. That would be something to see lol.
I'll get there.
As far as why did I choose this horn? To experiment with? Its big, and it was available as a completely designed horn someone claimed to be ready to produce....So I could have something in case my manufacturing goals fell through....something like that. Now I am only interested in building an even bigger horn or at least learning why it wouldnt work.
You’re still not documenting your measurement data well enough to be useful to anyone. At what listening distance? What are the distances from source to boundaries?
Regardless, two initial comments:
1. The presence of strong comb filter effects from 400Hz up suggests that you’re either still hearing plenty of reflected energy, you measured with left & right speakers on, or both.
2. While you might like the sound for listening to music playback, a falling slope with a 10dB level variance even with a smoothed magnitude variance from 400Hz up is not a response that response of my studio clients would accept at the listening position for mixing or mastering purposes.
Regardless, two initial comments:
1. The presence of strong comb filter effects from 400Hz up suggests that you’re either still hearing plenty of reflected energy, you measured with left & right speakers on, or both.
2. While you might like the sound for listening to music playback, a falling slope with a 10dB level variance even with a smoothed magnitude variance from 400Hz up is not a response that response of my studio clients would accept at the listening position for mixing or mastering purposes.
What is exactly meant by pattern flip? I assumed you were talking about phase....why does it matter?Yeah, beaming and pattern flip never goes completely out of style
I would assume it was soft, considering, how "hard" I've driven it and never heard the "clacky clacky" thats supposedly supposed to happen. I couldn't even tell you what the sound sounds like lol....anyone got a video or recording of said event.
If xmax is generally conceived as 7-10% at xmax. What happens at 65%? How about a 142%
I'd guess that distortion increases until you hit xlim...Axi is not making this matter clear but at the same time I'm glad to not have hit xlim, if thats whats happening....
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A horn might be described as having a dispersion pattern of 60 horizontal x 30 vertical.
"Pattern flip" is when the vertical dispersion becomes wider than the horizontal as frequency drops, as it does with horns (like yours) with a wider horizontal width than vertical height.
Off-axis reflections shift from side walls to the floor and ceiling as frequency drops, if that matters...
If you were to use the 1/3 octave wide CEA-2010 Burst test signal at 200 Hz and advance level one dB per test, you should easily hear a rather distinct difference in the sound when the diaphragm hits the phase plug, or stretches to the limit of the suspension, which ever happens first.
With music, unless you use a very narrow band pass on the horn/driver, like 200-315Hz BW24, the upper transients that accompany the fundamental's high excursion may mask the noise.
When the SPL of a harmonic rises above the fundamental, distortion is above 100%.
The level at which you recognize distortion is another question, and is dependent on the order of distortion- higher orders are generally more objectionable, as they may occur where hearing is more sensitive.
Distortion increases drastically when Xlim is reached.
The Axi's titanium diaphragm can probably withstand a fair amount of hammering without fracture.
The same can't be said about aluminum or beryllium.
Art
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True enough!
That diaphragm probably sounded bad for quite a while before the surround gave up.
what would a 50hz, tractrix, do, with the Axi? An interesting question; how far can one stretch this aspect and achieve high SQ.... 10hz horn?
Regarding pattern flip...this horn should hold some directivity till about 700hz or just below, based on mouth height ...I thought it a plus, being below the critical range.
Something like your tractrix does now- beam in the high end, drop off in response at the bottom...
The answer would depend on how "high" you are
.The pioneers of horns usually agreed that a decade of operation was about as far as one should push a horn if good sound quality is desired, 50-500Hz, 500-5kHz.
I'm getting more and more convinced, arounf a decade is all a driver section should try to cover for best SQ, in any kind of conventional or horn design.
I was hoping to hear something with an axi2050 and be convinced a 400 hz and up horn was possible. I have yet to hear something that I liked doing that.
Too bad COVID killed RMAF.
I think that 1 decade is a bit conservative for waveguides. With a good design it is possible to extend this by an octave (and sometimes nearly two.) Surely in days past a decade was the norm.