2 x 18NLW9400, 152 liters each closed box (or both in one box of 304 liters) - processing see MathCAD screenshot, next post.
2 x 15MI100, 91 liters each closed box, processing see MathCAD.
NO ANY resonator, filter corner frequency, steep phase decay, helmholtz, etc. between 20Hz and 400Hz -> Transient response at its best - tight controlled bass, group delay minimized. No Booming, no thunder, just pure signal. Absolutely perfect for home theater.
Crossover is done by pure mathematical magic
- see MathCAD.
Sensible Excursion distribution of both 15"s vs. both 18"s. So the 15s can go up to 400Hz without bad excursion caused intermodulation.
18s and 15s acoustically 100% in phase where it is most needed.
System level up to 108.75dBSPL undistorted, -3dB at 16.8Hz. (-10dB at 10Hz).
Aiming for below 17Hz may be BEYOND INSANE for music listening, but barely enough for some HT enthusiasts, over at avsforum.com. I am always wondering what kind of investment some guys there are doing to reach below 10Hz at medium SPL. This system is very cheap and light weight (at least in comparison to some avsforum freak systems).
Depending on the Amping used, the system may be below 170kg. Adding decent midrange and compression tweeter, DSP and amping, the whole system may be ~ EUR 6000 for DIY.
Next post is the MathCAD.
2 x 15MI100, 91 liters each closed box, processing see MathCAD.
NO ANY resonator, filter corner frequency, steep phase decay, helmholtz, etc. between 20Hz and 400Hz -> Transient response at its best - tight controlled bass, group delay minimized. No Booming, no thunder, just pure signal. Absolutely perfect for home theater.
Crossover is done by pure mathematical magic
- see MathCAD. Sensible Excursion distribution of both 15"s vs. both 18"s. So the 15s can go up to 400Hz without bad excursion caused intermodulation.
18s and 15s acoustically 100% in phase where it is most needed.
System level up to 108.75dBSPL undistorted, -3dB at 16.8Hz. (-10dB at 10Hz).
Aiming for below 17Hz may be BEYOND INSANE for music listening, but barely enough for some HT enthusiasts, over at avsforum.com. I am always wondering what kind of investment some guys there are doing to reach below 10Hz at medium SPL. This system is very cheap and light weight (at least in comparison to some avsforum freak systems).
Depending on the Amping used, the system may be below 170kg. Adding decent midrange and compression tweeter, DSP and amping, the whole system may be ~ EUR 6000 for DIY.
Next post is the MathCAD.
Those two 18sounds has same output as one bms 18n862 under 70hz.
Id say 862 bms is best infra sub from PA range.
Id say 862 bms is best infra sub from PA range.
Um, there is no "magic" going on here...
You simply have a closed box with a low Fc. The group delay curve is just what you would expect.
I wonder if you have done some calculations about the SPL you can generate at your F3 of 17 Hz with these drivers, while staying within Xmax?
Anyway, it all looks good, honestly. Unfortunately, the MathCAD screen shot is too low in resolution to make out anything except the general curve in the plots. Text is not legible at all. I would like to know more about your "magic" crossover. Can you break up the MathCAD image into parts: images, formulas, etc. so they are readable, and then post them?
Did you try opening pic using browser, then while open mouse over to the white X in the lower left corner of the pic and click on that for full res? Works fine here.
The "magic" is, that I use 2 filters of 20Hz corner electrically and what I get acoustically is a crossover of 65Hz WITHOUT ANY filter corner there.
By applying the electrical filter at 20Hz, I can compensate closed box rolloff and the rolloff will do the crossover "for free". So no extra group delay.
"I wonder if you have done some calculations about the SPL you can generate at your F3 of 17 Hz with these drivers, while staying within Xmax?"
-> the graph is in the mathCAD sheet: "Combined system output limited by XMAX..."
By applying the electrical filter at 20Hz, I can compensate closed box rolloff and the rolloff will do the crossover "for free". So no extra group delay.
"I wonder if you have done some calculations about the SPL you can generate at your F3 of 17 Hz with these drivers, while staying within Xmax?"
-> the graph is in the mathCAD sheet: "Combined system output limited by XMAX..."
Remember, at your 65 hertz, a single wavelength is at 5.217 Meters long, 17 hertz?, 20.176 Meters long...
----------------------------------------------------------------------Rick.......
----------------------------------------------------------------------Rick.......
Magic crossover ?
Phase ?
Delay ?
Maybe an integrator, like what bag end does.
You take a driver that is rolling 12db per octave in a sealed box (loosely, i think qtc 1.1 or higher), notch out fsb peak, then use a 12db low pass filter with a knee of 20hz.
Problem, 24db of boost at 20hz for a driver in a sealed box, not much output if you want flat 20-100hz.
But, it an option that keeps the phase right.
The bag end $4,200 21" did basically flat to 10hz at 95db.
Way Down Deep II Bag End S21E | Sound & Vision
Distortion is a bit high though, compared to other subs tested in the way down deep 2, especially the 2x12" snell for $2,600 .
Actually most retail subs are in a way too small box, with massive boost and subsonic protection.
Without an integrator, the delay (phase) of the crossover of the sub will do far more damage than even a 30hz tuned sub.
Phase ?
Delay ?
Maybe an integrator, like what bag end does.
You take a driver that is rolling 12db per octave in a sealed box (loosely, i think qtc 1.1 or higher), notch out fsb peak, then use a 12db low pass filter with a knee of 20hz.
Problem, 24db of boost at 20hz for a driver in a sealed box, not much output if you want flat 20-100hz.
But, it an option that keeps the phase right.
The bag end $4,200 21" did basically flat to 10hz at 95db.
Way Down Deep II Bag End S21E | Sound & Vision
Distortion is a bit high though, compared to other subs tested in the way down deep 2, especially the 2x12" snell for $2,600 .
Actually most retail subs are in a way too small box, with massive boost and subsonic protection.
Without an integrator, the delay (phase) of the crossover of the sub will do far more damage than even a 30hz tuned sub.
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@norman bates:
The bag end can do 17Hz at 'bout 101dB. It is quite expensive and non - flexible.
My dual 18 inch system can do 17 Hz at 105dB at XMAX. Using Gisen D415 and used Driverack 260, my system is more flexible (can be reprogrammed for outdoor party 130dB use by opening the ports and loading the other program in the driverack, which takes bout 2 minutes all together) AND cheaper (get full range party system for the cost of just one bag end plus its processor and amping) AND louder at 17 Hz, 20Hz, 30Hz, 40Hz, 60 Hz, 100Hz,...etc.... Due to the processing, my system may not beat bag end at 10Hz, but - honestly - I am into music listening and don't really care about the cannon shot fundamental at one special recording of Tchaikowsky's 1812 overture.
That said, for cinema use, bag end may be the better choice. But to get 10hz above the hearing threshold when masked by other frequencies of the cinema soundtrack, you really may need like 8 of those bag ends. And that is no more a 4 figure sound system. Completely different ballpark. A friend of mine used 32 x 15 inch closed speakers as a concrete "wall of bass" to reach 7Hz at body shaking levels in the so-called "club sub".
Don't dare to ask about the cost of that sound system.
The bag end can do 17Hz at 'bout 101dB. It is quite expensive and non - flexible.
My dual 18 inch system can do 17 Hz at 105dB at XMAX. Using Gisen D415 and used Driverack 260, my system is more flexible (can be reprogrammed for outdoor party 130dB use by opening the ports and loading the other program in the driverack, which takes bout 2 minutes all together) AND cheaper (get full range party system for the cost of just one bag end plus its processor and amping) AND louder at 17 Hz, 20Hz, 30Hz, 40Hz, 60 Hz, 100Hz,...etc.... Due to the processing, my system may not beat bag end at 10Hz, but - honestly - I am into music listening and don't really care about the cannon shot fundamental at one special recording of Tchaikowsky's 1812 overture.
That said, for cinema use, bag end may be the better choice. But to get 10hz above the hearing threshold when masked by other frequencies of the cinema soundtrack, you really may need like 8 of those bag ends. And that is no more a 4 figure sound system. Completely different ballpark. A friend of mine used 32 x 15 inch closed speakers as a concrete "wall of bass" to reach 7Hz at body shaking levels in the so-called "club sub".
Don't dare to ask about the cost of that sound system.
Im thinking 2x15" sealed.
Rss390hf
Ppsl
4-5ft3 each
Sealed f3 32hz
400w (for the 2 drivers) just skipping past 14mm xmax at 20hz for 108db.
20hz is approximately f9 for sealed.
Not a bad project for $400 plus box, no eq, no ports.
But box is 2' x 2' x 4'
Rss390hf
Ppsl
4-5ft3 each
Sealed f3 32hz
400w (for the 2 drivers) just skipping past 14mm xmax at 20hz for 108db.
20hz is approximately f9 for sealed.
Not a bad project for $400 plus box, no eq, no ports.
But box is 2' x 2' x 4'
Today I started testing with both 18"s and 15"s cabinets as closed box (ports stuffed.)
I use a mono sine signal going through Driverack 260. I disabled all XOVER etc from driverack to have an easy start. Mono sum for the 18"s and one stereo channel for the 15s (both in parallel at one poor amp channel). Since the test signal is mono, all channels would get the same signal. Amp is DSP-free (or "DSP off" mode actually)
Starting at 12Hz, I can feel the trembling of my wooden wall. I adjust the relative channels volume until trembling amplitude is same with the 15s and the 18s. Then I enable both channels (all 4 speakers) and play with delay and polarity. I can perfectly compensate (zero) the wall trembling caused by the 15s by turning on the 18s (and vice versa), IF I give the 15"s signal a delay of 12.5ms vs. no delay on the 18"s channel. (Of course, I can flip polarity then and have perfect +6dB).
Same is true at 18Hz - I need 12.5ms delay. Also at 24Hz. 12.5 - 13ms of delay will give perfect match / cancellation.
Any idea what's wrong?
I use a mono sine signal going through Driverack 260. I disabled all XOVER etc from driverack to have an easy start. Mono sum for the 18"s and one stereo channel for the 15s (both in parallel at one poor amp channel). Since the test signal is mono, all channels would get the same signal. Amp is DSP-free (or "DSP off" mode actually)
Starting at 12Hz, I can feel the trembling of my wooden wall. I adjust the relative channels volume until trembling amplitude is same with the 15s and the 18s. Then I enable both channels (all 4 speakers) and play with delay and polarity. I can perfectly compensate (zero) the wall trembling caused by the 15s by turning on the 18s (and vice versa), IF I give the 15"s signal a delay of 12.5ms vs. no delay on the 18"s channel. (Of course, I can flip polarity then and have perfect +6dB).
Same is true at 18Hz - I need 12.5ms delay. Also at 24Hz. 12.5 - 13ms of delay will give perfect match / cancellation.
Any idea what's wrong?
The issue seems to be driverack 260 related. If I go directly from signal generator to the amp channels, phase is perfect.
The problem is related to the 260s subharmonic synth. If I do a setup without it, everything is OK.
If I put it into the signal path, it messes with the relative delays / phases.
For 2 reasons, it should not do so:
1. I disabled it. A module, that is described as a sidechain mixed into the main signal, should do NOTHING if disabled.
2. It is a stereo module within the INPUTs, so the relative phases should not be messed, even if it was set to ON with synth amplitude to zero.
Looks there is a real issue with that module. I love what it can do, especially with closed subwoofers, but if I cannot get phase alignment, I cannot use it.
If I put it into the signal path, it messes with the relative delays / phases.
For 2 reasons, it should not do so:
1. I disabled it. A module, that is described as a sidechain mixed into the main signal, should do NOTHING if disabled.
2. It is a stereo module within the INPUTs, so the relative phases should not be messed, even if it was set to ON with synth amplitude to zero.
Looks there is a real issue with that module. I love what it can do, especially with closed subwoofers, but if I cannot get phase alignment, I cannot use it.
Today I found out, I was wrong. The Sub Synth is perfectly OK, what is messing with the Phase response is the crossover filters itself.
If I set up a high pass 19.7Hz BW 12dB and a lowpass, 19.7Hz BW 12dB, it looks the driverack does not calculate them correctly. Difference in phase shift between the two filters should at all frequencies always be exactly 180°, but is not the case with the 260's implementation. Any idea what's wrong?
If I set up a high pass 19.7Hz BW 12dB and a lowpass, 19.7Hz BW 12dB, it looks the driverack does not calculate them correctly. Difference in phase shift between the two filters should at all frequencies always be exactly 180°, but is not the case with the 260's implementation. Any idea what's wrong?
So, you basically are seeking a time aligned / phase aligned setup for the subwoofer ?
I think there are transient perfect 24db, but I know nothing about that stuff except a bit about 6db crossovers.
Phase is time, as the phase changes, so does the time, or delay.
I think there are transient perfect 24db, but I know nothing about that stuff except a bit about 6db crossovers.
Phase is time, as the phase changes, so does the time, or delay.
Hi, How are you going about comparing the difference in phase between the high passed 19.7Hz BW 12dB, and the same thing low passed?
There's not much of a frequency overlap to compare is there?
The two sides summed with neither inverted, should show pol+, and a deep magnitude notch at 20Hz, with otherwise flat mag.
The two sides summed with high pass inverted, should show pol-, and a +3dB magnitude hump at 20 Hz, with otherwise flat mag.
So if you're not getting a summed 180 degree out of phase (once above a few hundred Hz) along with the flat mag, 3dB hump at 20Hz....it sounds like a polarity issue...
What about using the Linkwitz transform or some other topology to create a pole shift for the sealed box alignment. It allows you to emulate a low Fs sealed box for a sealed alignment at a much higher frequency. The gotcha is that the EQ gets pretty extreme at low frequencies in the same way it does in the Bag End dual integrator. Knowing that going in, you can evaluate power and Xmax x SD to determine the max output and also decide if you will need a HPF. As always there is no free lunch!