The impedance curve suggests 6th order system, but that's a pretty wide bandwidth (30 Hz to over 200 Hz). That is a pretty decent response curve, and there are no out of band funnies either.
The impedance curves in #11 and #19 would indicate the excursion minima would be around 29 Hz, maxima around 48 Hz, so a 38 Hz HP would not be a logical excursion protection point, regardless of driver choice.
Looking at the FR and impedance curves, looks more like a typographic error, HP should be 28 Hz, not 38.
103dB/1w/1m@30Hz from a :
562 mm (22.1”), Width1226 mm (48.3”), Depth 903 mm (35.6”)
(642L external volume) cab seems impressive or implausible?
The SKHORN manages around 99dB/1w/1m and is: 32 in, 24 in, 54 in (679.6L external): Data-Bass: Subwoofer Measurements
Am I making a mistake here?
562 mm (22.1”), Width1226 mm (48.3”), Depth 903 mm (35.6”)
(642L external volume) cab seems impressive or implausible?
The SKHORN manages around 99dB/1w/1m and is: 32 in, 24 in, 54 in (679.6L external): Data-Bass: Subwoofer Measurements
Am I making a mistake here?
but so is the SKHORN as far as I know.
I found this post regarding the construction:
I found this post regarding the construction:
STASY X GUESS WHAT? - Speakerplans.com Forums - Page 4
About the SKHORN measurement on the Data-bass page: Voltage Sensitivity
Sensitivity was measured at 14.1 volts. Corresponding to 100 watts nominal into a nominal 2ohm load. The overall sensitivity is good. We can see that the measurement at 10 meters is a bit higher than the 1 meter measurement when normalized. This is due to the separation of the acoustic radiators on the front of the cabinet face. The 1 meter measurement is a bit under-representative. Either was we see that the sensitivity is in the range of 105-107dB at 70Hz. It remains at 100dB or greater down to about 34Hz with all vents open. With only a single vent per side open it maintains a 90dB sensitivity way down at 20Hz.
Sensitivity was measured at 14.1 volts. Corresponding to 100 watts nominal into a nominal 2ohm load. The overall sensitivity is good. We can see that the measurement at 10 meters is a bit higher than the 1 meter measurement when normalized. This is due to the separation of the acoustic radiators on the front of the cabinet face. The 1 meter measurement is a bit under-representative. Either was we see that the sensitivity is in the range of 105-107dB at 70Hz. It remains at 100dB or greater down to about 34Hz with all vents open. With only a single vent per side open it maintains a 90dB sensitivity way down at 20Hz.
Those plots are for the V1 Stasys X which was a bandpass design.
Re the 38Hz high pass, I thought the same about it being strange, I think most likely a miss print and should be 28Hz.
I made some LEM sims in Akabak and must say I'm pretty confused.
BEM setup - half-space ground measurement 1m
This is what I got with horn-loaded re-entrant ports going from rear chamber.
As you can see these charts are far from original stasys measurements.
However I tried to close rear ducts at the horn throat side and result is much nicer. The impedance chart almost copies the original stasys chart.
Next step is to sim the system as BEM+LEM so that in BEM will be the full geometry except the front circular ports which can be added easily as lumped elements.
BEM setup - half-space ground measurement 1m
This is what I got with horn-loaded re-entrant ports going from rear chamber.
As you can see these charts are far from original stasys measurements.
However I tried to close rear ducts at the horn throat side and result is much nicer. The impedance chart almost copies the original stasys chart.
Next step is to sim the system as BEM+LEM so that in BEM will be the full geometry except the front circular ports which can be added easily as lumped elements.
Repeating myself, the "horn loaded" ports are a lot longer than the circular ports. The longer "ports" alone would result in an Fb lower than 29Hz, the shorter ports alone much higher, mixed together they result in an Fb of 29Hz, assuming your depicted design and previously posted impedance and FR plots are from the design you are simulating.
As a simpler example of mixed ports (photo below), using standard 1.5” PVC schedule 40 plumbing parts, pipe couplings for “built in” ports, then adding 90 degree slip elbows, then adding pipes from the elbows allows quick tuning changes on a pair of studio monitors/PA speakers I have been using.
Hot Rod 8” 2-Way PA/Studio Monitor
Net cabinet volume of the monitors=15.9 L or .5618 cubic feet net.
The various tunings (Fb) are roughly:
76 Hz with no elbows, both pipe coupling ports open
62 Hz with 1 elbow added to one port
60 Hz with 2 elbows added to both ports
48 Hz with two elbows and one 5" tube (past elbow)
44 Hz with elbows and two 5" tubes (past elbow)
40 Hz with elbows and one 5" and one 8" tubes (past elbow)
35 Hz with elbows and two 8" tubes (past elbow)
In each example, the addition of an extension to just one duct resulted in a lower Fb.
In the design you are considering, the VTC of the "V" horn coupling may also effectively function as a tuned resonant absorber in the "horn loaded" ports, smoothing response by reducing "pipe resonance".
Lots of interesting stuff Rog Mogale/Void incorporated in this design!
Art
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weltersys,
Thanks for the pictures now I understand what you mean by "the rear ports are much longer than the circular ones".
I've been modelling the system in a different way. I consider the rear ports to be just that short 3 ducts along the rear wall. The rest of the path is just folded horn.
1, 2, 3 are the rear ports
A is a duct, B, C are waveguides
Thanks for the pictures now I understand what you mean by "the rear ports are much longer than the circular ones".
I've been modelling the system in a different way. I consider the rear ports to be just that short 3 ducts along the rear wall. The rest of the path is just folded horn.
1, 2, 3 are the rear ports
A is a duct, B, C are waveguides
The ducts starting at the corner of "1,2,& 3" don't end when turning around the next corner simply because the divider/braces stop there.
"1,2,& 3", and "A, B, C" are all part of the same air column, pipe, duct, port, or horn whatever you want to call it, but a "waveguide" must be large enough to guide waves ;^).
"1,2,& 3", and "A, B, C" are all part of the same air column, pipe, duct, port, or horn whatever you want to call it, but a "waveguide" must be large enough to guide waves ;^).
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Hi Maple have you tried a full Bem simulation?...
it would be interesting to analyze the propagation behavior of the waves inside the enclosure, i've tried tu set up a comsol simultion years ago whitout luck
