Lol tell that to the filter! In hornresp, the filter barely attenuated the lower spectrum....in vituixcad the same type filters did what my dsp did in real life...the 25db on gain in vituixcad is from a time in the same when I had realistic gainstaging within the sim....the sim now is only good for the FR....and GD
I'm going to get up and go check and make sure everything I told you was accurate to my experience lol
ok I can see it but can I convey it....I'm not sure if I can create the same hf roll off slope without executing this combination of filters.
The sub and mid bass initially have about the same FR. The low pass pushes a good portion of the subs upper FR down, while the range around 30hz is already of lo sensitivity, hence the gain to bring the levels back up....putting 30-20hz within levels of the midrange without the use of Peak filters....looks like a book door for lower filter induced, group delay. The low end roll off is coincidental yet, acceptable enough for room eq to doctor up.
Executing the Filters in this manner results in lower filter induced group delay.
Non of this can be accurate sim until I take measurements at a static input level....I am going to start now, but my first question was already formed,....I'm getting like not even 85db at 1inch, with 4 volts at 30hz....how? The sim suggest 95db with 4 volts at 30hz, whats the disconnect?
The sub and mid bass initially have about the same FR. The low pass pushes a good portion of the subs upper FR down, while the range around 30hz is already of lo sensitivity, hence the gain to bring the levels back up....putting 30-20hz within levels of the midrange without the use of Peak filters....looks like a book door for lower filter induced, group delay. The low end roll off is coincidental yet, acceptable enough for room eq to doctor up.
Executing the Filters in this manner results in lower filter induced group delay.
Non of this can be accurate sim until I take measurements at a static input level....I am going to start now, but my first question was already formed,....I'm getting like not even 85db at 1inch, with 4 volts at 30hz....how? The sim suggest 95db with 4 volts at 30hz, whats the disconnect?
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This is my suggestion. Measure the speakers as close to the centre of the room as you can get them.
With a known voltage from the amplifier (1V 2.83V) Take a nearfield measurement of the sub, put the microphone in between the two drivers in the slot on the axis of the dust caps. Make a measurement at the same position but 1m further out.
Use the nearfield measurement as the input to a baffle diffraction sim. Try both a rectangle the same size as the slot to represent the driver on a baffle of the right size and shape. Try an 18" round driver centred and generate the off axis responses. Compare the two look at the differences in directivity.
Take a nearfield of the mid as close to the centre of the dustcap and as near to it as you can get without it hitting due to excursion.
Take a measurement 1m further away. Generate the baffle diffraction for a 15" driver on a baffle of the same size and shape that you have.
Using the same voltage and gain on the mic preamp should let the two 1m measurements show the sensitivity differences between the sub and mid and help to scale the levels of the nearfield measurements.
Put these and these only into a Vituix sim making sure to ground the source and branch both drivers off from the same source.
Before I get into this, heres the trend of the process.
Similar FR from, each driver, on the bass side.
Heres after 21.5hz 2nd order LP Butterworth
Heres after what I called make up gain.
These are my first set of measurements.....I was noticing that voltage changed if I changed frequency on the signal Generator, thats why I asked,..
what ever the 90 and 70 issues are, they'll likely be there in the next measurements, just ignore them. I also have a room full of woofers that aren't shorted....maybe thats it.
Similar FR from, each driver, on the bass side.
Heres after 21.5hz 2nd order LP Butterworth
Heres after what I called make up gain.
These are my first set of measurements.....I was noticing that voltage changed if I changed frequency on the signal Generator, thats why I asked,..
what ever the 90 and 70 issues are, they'll likely be there in the next measurements, just ignore them. I also have a room full of woofers that aren't shorted....maybe thats it.
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Blue- as close as possible to the 15m's non moving phase plug lol
LightGreen/Blue - Just slightly in front of slot boundary...
Red- inside the slot in between non moving phase plugs of the 18h+'s
0.48V because 4v is crazy loud for this moment in time haha.
70 and 90 could also be the slot modes, and are being activated in the 15m? measurement?.....or several other things.
This below, is the sub after the XO filter, measured right in front of the slot
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Sorta of, a high DI actually retains its intensity, farther, than a low DI...
The reference to "near-field" listening and high DI has to do with balance of direct and indirect energy. The direct energy will dominate at a closer listening position, thus drowning out the "flaw" of the rising power response
A System with a constant DI will have more nuetral reverb, and more reverb... and at the same listening distance will produce more total indirect energy than the DI system Im working on...
Both Systems will go omni somewhere in the transition to lower frequencies, so neither one truly has constant directivity....just one has more parts of spectrum as constant directivity and my system has high DI over more of the spectrum.....
raising DI increases SQ
Creating constant directivity raises SQ
no ones winning, per say.
I think it's possible to create constant directivity waveguide that has higher DI than what we commonly see applicated and maybe higher than the DI of a large horn? But Im not sure. So I set the stage for the commonly seen 15" waveguide made to match a 15" woofer along with the approximate 30degree or so wide pattern from like 10khz to about 700hz or so...
Also, the sweet spot, is always highest resolution listening of any system, dead on axis or slightly off axis, with trend, the farther away you move from 0 axis the worst SQ gets....
My theory
The reference to "near-field" listening and high DI has to do with balance of direct and indirect energy. The direct energy will dominate at a closer listening position, thus drowning out the "flaw" of the rising power response
A System with a constant DI will have more nuetral reverb, and more reverb... and at the same listening distance will produce more total indirect energy than the DI system Im working on...
Both Systems will go omni somewhere in the transition to lower frequencies, so neither one truly has constant directivity....just one has more parts of spectrum as constant directivity and my system has high DI over more of the spectrum.....
raising DI increases SQ
Creating constant directivity raises SQ
no ones winning, per say.
I think it's possible to create constant directivity waveguide that has higher DI than what we commonly see applicated and maybe higher than the DI of a large horn? But Im not sure. So I set the stage for the commonly seen 15" waveguide made to match a 15" woofer along with the approximate 30degree or so wide pattern from like 10khz to about 700hz or so...
Also, the sweet spot, is always highest resolution listening of any system, dead on axis or slightly off axis, with trend, the farther away you move from 0 axis the worst SQ gets....
My theory
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There isn't something like a constant DI.
There is something that's called a constant directivity.
A constant directivity only says something about how linear the off-axis response is of a given speaker.
Reverb doesn't have anything to do with that.
Reverb will be less with a speaker with an high DI.
None of this applies to near-field listening, where any non-direct sound isn't of any (or very little) significance anymore.
There is something that's called a constant directivity.
A constant directivity only says something about how linear the off-axis response is of a given speaker.
Reverb doesn't have anything to do with that.
Reverb will be less with a speaker with an high DI.
None of this applies to near-field listening, where any non-direct sound isn't of any (or very little) significance anymore.
Once i have a real speaker or sub to measure, I quit using simulations for tuning.
Imo, sims are for helping get as close to the acoustic build as possible, but once built, reality / measurements is all that matters. (when using active..)
So yes, focus on measurements....raw measurements first, as i see you've been making ...good.
I'll be surprised if noise floor is an issue, but i definitely think the 24dB gain that's being applied to the very bottom end response, leaves very little dynamic headroom at 20Hz without greatly increased distortion. And thus limits the entire sub's max linear output.
I will if you like, but i don't think there's enough apples to apples for a fair comparison.
My dual 18" PPSL using bass reflex was tuned to f-3 @ 30Hz, with the need for only 2-3 dB boost at that low corner.
I'm unwilling to chase 20Hz with excessive gain, preferring to stay in the range where acoustic response is relatively flat..
So my measurements look alot nicer, albeit at the expense of not trying for response below 30Hz.
If and when i want 20Hz, i'll probably build something using larger cones, like ipal, or the SI-24. Again with the idea of choosing the most natural acoustic design for the task.
Great question. My answer, yes...all the same, other than low end extension, and max linear SPL.
(and i don't think a sub should ever be used too much above 100Hz.)
This of course is quasi-anechoic, which makes in-room integration more logical and easier ime.
I just put the 18H+ into my PPSL hornresp build. It looked good to 30Hz just like my bms 18n862. Nice driver.
But honestly, I don't think either of us should be trying for 20Hz out of our builds, other than for when low volume is totally cool.
That is one funny looking sim ! Sim art, nice!
Please show the raw response of the driver it took to pull that off.
Thank you for the detailed response. I am not sure what you mean by limiting the entire subs max linear output. Max linear output is determined by xmax not gain. How do I measure this?
The measurement below is pretty close to intended proximity.....This is very little headroom? Theres still more headroom than this.....but This, isn't enough already!?
I'm not ignoring your point btw, the pic is just a starting point of the real life measurements using the designed filter, as you said, start with sim but move to real life measurements and adjust accordingly. I could see my system rolling off at 30hz. if I chose to roll it off at 20hz....there is plenty of headroom, because the measurement below is very low distortion for the loudness and dept of frequency, as well, practically too loud, as well, at the 20-30db peak transient area meant for listening at 80db range. 30db was the requirement I have an amount that cannot be achieved for measurement because it would break something.
Do I recall correctly? 2nd order is near 7 or 10% rounding xmax? The pic shows 20hz at 115db with 4.5% 2nd order. In what size room would I NOT have enough headroom, that is the thing to discern! For the rooms of the Average middle class house, I think its just right lol. I think I might have enough headroom to power a small home theater with all drivers in motion, thats including the surround subs that are yet to be built.
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Well we don't know in what kind of echo chamber you're living.
But if the reverberation and reflections are that bad, I would be more worried about your comfort of living.
Second to that I would advice to spend all this time, effort and money in room treatment.
Btw, it's not just measurements (or ears) that only matter.
It's about understanding physics around it en getting a sense of significance.
Is it me or should the high and low pass be reversed?? Never used the program. I would expect a 20Hz high pass and 80Hz Low pass to do that. Just looking at a dummy load vs. sim filter response.
Rob
