You bet. Yeah, there's a lot of speculation about where QSC is headed. Seems QSys has become such a giant install platform, live sound and other such markets may not matter to them anymore.
I hear you re the PLDs. I like the built-in RMS and peak voltage limiters, but past that I'd rather have outboard DSP that's a lot more capable.
If the QSys Core110f Version 2 become available (and affordable); or if the original 110fs return back to the low $1000 range in the used ebay market, that would be a good solution for 14+ch output, imo.
Please let me second the request to hear the errors/misconception you think we should be aware of..
Did "the guy" have any measurements to back up his comments?
Effectively, what you have drawn is a small, short port with a larger resonator at one end.
The restriction would result in an acoustic Low Pass (high cut) filter, and lower Fb than the full sized cylinder (if that's what the cross section is supposed to be) but the reduced port area would make it whistle at high velocities. OK for low dynamics, fart generator when turned up.
Core 110f Version 2
Q-SYS network + analog I/O processor (v2)
https://www.qsys.com/products-solutions/q-sys/processing/core-110f/
Version 2 available? Maybe? Price? I'll keep it in mind for now.
Edit - Went looking for prices used. Out of sight!
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https://www.subwoofer-builder.com/flare-it.htm
This program is helping me figure some stuff out....
The thing is Velocity is effected by tuning and CSA.....
This program is helping me figure some stuff out....
The thing is Velocity is effected by tuning and CSA.....
This is one of my Axi+Horn sim, at high spl
I know my Hornresp simulation is lacking BUT.....is there a reason why the excursion doesn't continue to go into oblivion on the LF side?....Is this what the excursion trend line, of a 15", looks like past F on a BR, if we could see the rest of the trend past 10hz??? I think so...
Sooo, I think I missed something. Its been sort of confusing jumping between trying to keep track of where excursion is, via THD and where THD is at, 1m....Horns are complicated in that manner and spl gets high quickly within the throat.
Turns out I have a lot more headroom than I thought and that the 200hz XO is not only, a likely reality, but I could potentially go lower with a steep enough filter....🤯
Huge plot twist for me at least
So heres my last effective voicing in blue (actual measurement NA ATM) 115db, ~1m, indoors, THD peaks at the 200hz ~24% 2nd order but is lower below and above....Looking at the null in the raw outdoor response in green...makes perfect sense....So even though THD high, it would lower if we lowered the mic or and there is no issue that I can tell yet, below 150hz.....I was just thinking that I need to run 2 tone test for modulation and see what it shows me. In the past I've ran one tone at say 20hz and another at maybe 7khz and played with EQ until I found good a good voicing. Not sure how that played out with the current voicing.
With the addition of the mid woofer, Thd will lower at 200hz.
While playing passband at 115db/1m, 200hz is at 109db...add another channel for stereo and we are down to 106db. Thd is fine in both cases.
So....I need to verify what it is, I think I know. I do know that I can use steeper filters, that will improve excursion, ever more. If things are looking up, I could be inspired to do something different with the woofer section, being that 200hz is well within 18" territory.
Turns out I have a lot more headroom than I thought and that the 200hz XO is not only, a likely reality, but I could potentially go lower with a steep enough filter....🤯
Huge plot twist for me at least
So heres my last effective voicing in blue (actual measurement NA ATM) 115db, ~1m, indoors, THD peaks at the 200hz ~24% 2nd order but is lower below and above....Looking at the null in the raw outdoor response in green...makes perfect sense....So even though THD high, it would lower if we lowered the mic or and there is no issue that I can tell yet, below 150hz.....I was just thinking that I need to run 2 tone test for modulation and see what it shows me. In the past I've ran one tone at say 20hz and another at maybe 7khz and played with EQ until I found good a good voicing. Not sure how that played out with the current voicing.
With the addition of the mid woofer, Thd will lower at 200hz.
While playing passband at 115db/1m, 200hz is at 109db...add another channel for stereo and we are down to 106db. Thd is fine in both cases.
So....I need to verify what it is, I think I know. I do know that I can use steeper filters, that will improve excursion, ever more. If things are looking up, I could be inspired to do something different with the woofer section, being that 200hz is well within 18" territory.
I ran some dual tone test, and I am learning new things....I use the lowest tone to cause excursion and test for THD/IMD and highest tone as a contrast. I think I've learned that higher signals are generally easier to reproduce so are less vulnerable to IMD.....Its the frequencies, that are lower, that in combination with other, excursion hungry frequencies that can turn to "mud" or IMD starts to be exposed, almost in harmonics, as you lower the upper tone.
If thats true, then I should be concerned about distortion near F, as higher frequency seems to be less vulnerable until excursion increases even more.
An easy and revealing test would be to low pass somewhere right before the knee of F, then listen....Signal generator and Music, etc at different volumes. Maybe move the low pass to left of the cutoff knee and see what it sounds like with more spl.
It also seems IMD is vulnerable to 2 signals placed near each other....with higher frequency, the "near" area gets tighter
If thats true, then I should be concerned about distortion near F, as higher frequency seems to be less vulnerable until excursion increases even more.
An easy and revealing test would be to low pass somewhere right before the knee of F, then listen....Signal generator and Music, etc at different volumes. Maybe move the low pass to left of the cutoff knee and see what it sounds like with more spl.
It also seems IMD is vulnerable to 2 signals placed near each other....with higher frequency, the "near" area gets tighter
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Change the frequency range to 1 - 2000 Hz to see down to 1 hertz on the chart, and to sample down to 0.1 hertz.
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I'm not so sure what you said, but it seems wrong. The ear is most "sensitive" to freqs 700<3500 so tolerance for "errors" is probably low.
I tend to agree that higher excursions will make things "muddy" from the LF modulation of the HFs and all speakers will reach this level at some SPL. The key is to design such that this doesn't happen in the range of desired SPLs. Your requirements seem extreme by my standards, but in any case its certainly always achievable. Keep excursion within the linear range and limit the bandwidth of each driver and the "muddy" situation won't happen.
Keep the LF source - high excursion - below the "sensitive" range (above) and the LF modulation of the HFs is not a big issue. My mains hardly have any excursion at all being minimal contributors to the VLF stuff <100 Hz.
Hi Mr. Geddes
I have read my way through your thread: Multiple Small Subs - Geddes Approach. From that I did understand, that the mains in your system do play full-range, in that way being part of the multiple sub array (randomly placed in the room).
Are you with the above comment saying that you actually do high-pass-filter your mains? Did I miss something? I am very interested in that approach.
Regards
Steffen
I need some opinions, I am playing devils advocate with my current design. Being that I can most likely, easily cross at 200hz, to the horn.
.If I use Offset horn and a little bit of stuffing I can clean up the FR pretty good. Offset horn, automatically generates Path parameter, and allows damping in the sim. BR does allow damping in the simulation and I think I should have set a Path....not sure yet.
So now the question is....should I Lol
2 18"s facing front, to create a TMM crossed at 200hz....~500 liter enclosure tuned to 22hz (approximately the above sim)
Or
1 15" sealed mid crossed to 2 18"s PPSL(sealed or vented)....
Both situations, as long as the 18's are vented, excursion is below 1.5mm, when an approximation of all drivers are included in sim. Below 1.5mm at 116db/1m...When looking at mains and rear subs ballpark dynamics, half space.
The PPSL has some phase issues that limit summing to mid 15". That can be fixed with phase EQ, supposedly, and the PPSL is good to 200hz
The PPSL could be sealed or vented. Right now its sealed.
Vented Dual 18's in a TMM in combo with rear subs, has not a lot of excursion. This is ~116db with FR forced flat, in green
I think the imaging would be better with a TMM, midrange might be better as well... The effect of spaced out, multiple, redundant, bass sources would stronger with with TMM, resulting in a smoother FR in the room....It looks good on paper but I am unsure. I'm sure I can get some good remarks to help me see clearly
@GM @gedlee @weltersys @fluid @b_force @mark100 @Ro808 @mitchba @AllenB
.If I use Offset horn and a little bit of stuffing I can clean up the FR pretty good. Offset horn, automatically generates Path parameter, and allows damping in the sim. BR does allow damping in the simulation and I think I should have set a Path....not sure yet.
So now the question is....should I Lol
2 18"s facing front, to create a TMM crossed at 200hz....~500 liter enclosure tuned to 22hz (approximately the above sim)
Or
1 15" sealed mid crossed to 2 18"s PPSL(sealed or vented)....
Both situations, as long as the 18's are vented, excursion is below 1.5mm, when an approximation of all drivers are included in sim. Below 1.5mm at 116db/1m...When looking at mains and rear subs ballpark dynamics, half space.
The PPSL has some phase issues that limit summing to mid 15". That can be fixed with phase EQ, supposedly, and the PPSL is good to 200hz
The PPSL could be sealed or vented. Right now its sealed.
Vented Dual 18's in a TMM in combo with rear subs, has not a lot of excursion. This is ~116db with FR forced flat, in green
@GM @gedlee @weltersys @fluid @b_force @mark100 @Ro808 @mitchba @AllenB
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Good question, very perceptive. Clearly you understand the concepts.
But, no, I do not HP the mains electronically. The situation is that I always design for a slight LF boost (and HF cut) and I never add gain to the mains, cut only (with subsequent DSP.) This means that the dominate subs <100 Hz are not the mains. They still play, but at much lower levels than the other subs. This limits their excursion.
Fluid - I have 5 of those drivers < 100 Hz so there is more than enough headroom in my system.
what exactly? is anyone else confused, plz let me know, which part exactly, I did not explain clearly. So that I can elaborate. Cause I really want to know your opinions.
I may be forgetting what it is that you don't already know, causes one to explain things, as if you already know the backstory, etc.
My woofer section is in the picture above. I am contemplating, an alternative configuration known as TMM. Also pictured above
The excursion of a TMM with 18"s plus the planned rear subs...looks like this at 116db/1(green)
The reason I am contemplating this is because I am much more confident that I will be able to cross over the Axi+Horn at 200hz. I am trying to weigh pros and cons of switching the woofer section to Dual 18"s vent tuned to 22hz. I forced FR flat on the above Green plot. Excursion is below 1.5mm with the vented 18"s at 116db/1m
The Dark Blue line is actually 4 15" sealed, representing that portion of the spectrum, if I kept my current set up, and added rear subs. it is not forced flat but is rolled off at 65hz with a 4th order Hp in addition to the natural roll off.
In light blue is 8 sealed 18"s representing the current sub section (pictured above) plus rear subs that I have yet to build.
Everything is at 116db/1m force flat, except for the sealed 15, which is 116db/1m but with a roll of at 65hz.
In trying to nit pick the designs, I suggested that the PPSL has some phase flipping that limits the amount of summing/coupling to occur between the PPSL and the 15" sealed mid in their crossband. With dual 18"s on the face of the enclosure they would sum about perfect from 200hz down to cutoff.... I could theoretically fix phase with dsp and the PPSL would sum better with the 15. Potentially. I haven't tried in simulation yet, to get a picture of what can be done. The PPSl has usable output to 200hz it could play to XO if desired.
Once again, if I chose a TMM, excursion is still very low in comparison to my current configuration... It would be also, essentially, "Simpler"....We have talked about how, Simple, in an engineering perspective, is desirable.
So woofer section faceoff......
sealed 15+Sealed or vented 18' PPSL
vs
Dual Vertical stacked 15's in really big box tuned to 22hz, lightly dampened.
all while trying to including rear subs to show final excursion.
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