The SEOS-15 already offers that XO point. Its foolish to get a bigger waveguide and then not allow for even lower XO Point. A 1.5" throat gives us the ability to have a bigger CD.
If someone is thinking about building bigger horns they have to understand really why they are choosing the SEOS-18 over the SEOS-15.
The decision of someone wanting the SOES-18 to XO at 900Hz still is a silly decision when the SEOS-15 gives them that and matches already with a 15" woofer and it looks far better being that the sizes match. It already takes more skill to have a quality XO at 900Hz with a 1" CD (minus TADs), why fight logic and not go with a 1.5" or 2" CD that allows for a much lower XO point??
I will ask you this, why would you buy the SEOS-18 over the SEOS-15??
We will disagree, the measurements show directivity down below 1KHz (900Hz is just fine), I guess we are looking at different measurements 
Go to the AVS forum and ask that question if you like, no one else has posted any opinion so far that agrees with your 1.2KHz comment.
From coctostan
I like his opinion over yours so far
Go to the AVS forum and ask that question if you like, no one else has posted any opinion so far that agrees with your 1.2KHz comment.
From coctostan
I like his opinion over yours so far
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Also remember Geddes summa (The perfection of OS speaker design with a 15" OS waveguide with XO around 900Hz) so to debate if the SEOS-15 is suitable to be XOed at 900Hz seems to be silly considering we have the ultimate precedence set already.
Heck, the design around the SEOS-15 used the 15" Summa waveguide, 900Hz point as the starting point back when the AVS thread started. I know because I forced that reference point
Honestly, The SEOS-15 design would be a failure in my books if it lost directivity at 1.25KHz.
Heck, the design around the SEOS-15 used the 15" Summa waveguide, 900Hz point as the starting point back when the AVS thread started. I know because I forced that reference point
Honestly, The SEOS-15 design would be a failure in my books if it lost directivity at 1.25KHz.
tit for tat aside, take a look at post #591 in this thread and tell me where you think the horizontal directivity loses control. All other data that I have seen shows similar so far. Also one needs to look at impedance and distortion to show where the waveguide is really loading to. I am pretty confident that will back up what I am saying.
I think your recollection of Geddes's design specifications overlooks some critical points. His choice of 900hz was on the overall design, not proof that the 15" OS WG held exactly to 900hz. He said is that same thread that he thought 18" would be more ideal (look it up). But, even still, the axisymmetric 15" waveguide has a lot more mouth area than the SEOS15, which was a tradeoff, known from the get-go in order to more optimize on CTC spacing. There is no free lunch. More mouth area will give more loading down low all else being equal. The measurements of the round WGs versus the square ones (QSC) clearly show this if you study them long enough and fits well with horn theory. But we intended this set of tradeoffs on purpose. I know, I was one of those helping with the design in the first place.
I am not saying that you can't mate a SEOS15 with a 15" woofer and get good results, just not the compromise I want to take. You choose your own set of compromises.
You can listen to whomever you wish. I don't care if you respect the opinions of others over me (I don't give two *****, but i did find that comment extremely childish). You follow whomever you like, but if you'd like to debate facts or compromises, then I am here to discuss with you. Otherwise your on your own.
I think your recollection of Geddes's design specifications overlooks some critical points. His choice of 900hz was on the overall design, not proof that the 15" OS WG held exactly to 900hz. He said is that same thread that he thought 18" would be more ideal (look it up). But, even still, the axisymmetric 15" waveguide has a lot more mouth area than the SEOS15, which was a tradeoff, known from the get-go in order to more optimize on CTC spacing. There is no free lunch. More mouth area will give more loading down low all else being equal. The measurements of the round WGs versus the square ones (QSC) clearly show this if you study them long enough and fits well with horn theory. But we intended this set of tradeoffs on purpose. I know, I was one of those helping with the design in the first place.
I am not saying that you can't mate a SEOS15 with a 15" woofer and get good results, just not the compromise I want to take. You choose your own set of compromises.
You can listen to whomever you wish. I don't care if you respect the opinions of others over me (I don't give two *****, but i did find that comment extremely childish). You follow whomever you like, but if you'd like to debate facts or compromises, then I am here to discuss with you. Otherwise your on your own.
P.S. also look up augerpro's measurements of the QSC horn and comments as to how low that WG held directivity and I think you'll find the same 1.25khz comment (i think Zilch said it, iirc). Seeing as the SEOS15 was meant as a replacement with some more modernization, it too should also hold to 1.25hz, and the measurements I see confirm this.
umm....went looking for other measurements other than the ones posted in this thread, so we could have something concrete to discuss. I too have seen comments thrown around as to what these WGs hold directivity to and wondered if they were looking at the same things as me. (it looks like people are looking at FR going down to 900hz, not the width between subsequent angle FRs which shows directivity)
....well I came across, who other than cocostan's response that says
AVS Forum - View Single Post - Waveguide and Horn Delivery (Photos)
....well I came across, who other than cocostan's response that says
AVS Forum - View Single Post - Waveguide and Horn Delivery (Photos)
FWIW, I'd look at the 45 degree line vs the 0 degree line. That is the -6db line, which defines constant directivity. Again, its hard to be definitive with that graph and not expanding it a lot in paint or some other program. I would say it is not collapsing, which is why I think its ok with 900hz, just maybe not "ideal". That is my point. Plus if you looked at things like distortion graphs, impedance and phase you'd get a more complete picture.
Never-the-less, i think they are great waveguides and measure up. My own rep was at stake since I argued for a particular design, and am not bashing in any way. I just was arguing a particular interpretation.
Never-the-less, i think they are great waveguides and measure up. My own rep was at stake since I argued for a particular design, and am not bashing in any way. I just was arguing a particular interpretation.
JoshK and Brett. Im sorry but you are still wrong about any collapse above 1KHz. You definition of collapse is your own but hardly a scientific one, Remember that 15" should hold direcitivity below 1.2K in theory anyways. "Weakened" has no meaning in audio either to me, its either sounds fine or it does not. If its a compromise then its not good.
Many people always will believe what they want to believe so no reason to have a back and forth discussion. Here is the conclusion of this.
If you believe the SEOS-15 should be used to 1.2K then only use it to that point and I do understand why you would argue for the SEOS-18 is okay with 1" (just disagree because you limit the SEOS-18s potential). Many others will be building incredible waveguide designs with XO points below 1KHz and therefore the idea of the SEOS-18 only being a 1" exit is a waste and does not allow for the maximized advantage of the SEOS-18 which is directivity down closer to 700Hz.
I personal have never built a product or offer anything to customers that had a limitation taking away the products full potential but that is just me and how I have run my company.
Many people always will believe what they want to believe so no reason to have a back and forth discussion. Here is the conclusion of this.
If you believe the SEOS-15 should be used to 1.2K then only use it to that point and I do understand why you would argue for the SEOS-18 is okay with 1" (just disagree because you limit the SEOS-18s potential). Many others will be building incredible waveguide designs with XO points below 1KHz and therefore the idea of the SEOS-18 only being a 1" exit is a waste and does not allow for the maximized advantage of the SEOS-18 which is directivity down closer to 700Hz.
I personal have never built a product or offer anything to customers that had a limitation taking away the products full potential but that is just me and how I have run my company.
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Here's some distortion data - I put together a crossover crossing a DE-250 in an 18" rectangular waveguide (mostly conical, roughly OS with large mouth roundovers) and crossed over at 750Hz, which is just above where the inherent response starts to roll on the driver'/waveguide. The midwoofer is a TD15M. The 750Hz point just happened to be where the setup seemed to want to crossover based on the different depths of the drives (when I go active, I'll be able to deal with delays better). Also, the waveguide level looks (and sounds) like it needs to be reduced about 4dB or so.
The levels shown are actual SPL, obnoxiously loud, at 6ft from the cabinet.
The distortion is visible between 800 and 1800Hz (second harmonic) and 800 and 1200 (third harmonic), but really aren't bad in either case. There is something screwy around 380Hz, too, but I think that might be from furniture buzzing (a CD cabinet nearby wants to sing along at these levels).
I don't know whether this says anything about low-end crossover point for the 1" DE250 in a home setting, but it certainly doesn't look like a disaster at least.
The levels shown are actual SPL, obnoxiously loud, at 6ft from the cabinet.
The distortion is visible between 800 and 1800Hz (second harmonic) and 800 and 1200 (third harmonic), but really aren't bad in either case. There is something screwy around 380Hz, too, but I think that might be from furniture buzzing (a CD cabinet nearby wants to sing along at these levels).
I don't know whether this says anything about low-end crossover point for the 1" DE250 in a home setting, but it certainly doesn't look like a disaster at least.
I need the phase. Best is a set of impulse responses at a sampling rate of 44.1 kHz, but the sampling rate is not critical. I usually do 0, 5, 10, 15, 20, 30, 40, 50, 60, 80, 100, 120, 150, 180 degrees. That's because the resolution required is greatest where the rate of change of the polar response is the greatest and that, of course, is on axis. I can interpolate to these angles from any set of angles but thats just another set of calculations. I can also get by without the rear data, but again, the rear data helps to improve the forward data.
Sorry, I don't have the waveguides anymore, and didn't save impulse responses. I just had the horns a few days (along with a bunch of others) and just saved response patterns as described, 0 degrees to 75 degrees off-axis at 7.5 degree increments. Wish I had saved IRs but it was hot out where I was doing it, I didn't have a lot of time, and wasn't as thorough as I might have been. The responses should be minimum phase, though, so the phases (and IRs) should be derivable via Hilbert transform, right? Or do you expect some non-minimum phase from the edge reflections (or HOMs)?
I can remap the data to "FFT" format at 44.1k, though data below 500Hz will be absent (0) if that matters. The responses drop pretty well by 19kHz, so not having anything between 20kHz and 22.05kHz shouldn't be an issue, I don't think.
I can remap the data to "FFT" format at 44.1k, though data below 500Hz will be absent (0) if that matters. The responses drop pretty well by 19kHz, so not having anything between 20kHz and 22.05kHz shouldn't be an issue, I don't think.