Post by SubDevo on Feb 25, 2009 4:52:22 GMT -5
Ok everyone here we go...
My question to harristech:
The response from harristech:
Ok, I don't accept this. So I did some testing on my own...
Software used for testing:
UniBox
Subwoofer Simulator
LSD (Loudspeaker System Design - my own software - unreleased)
WinISD Pro
BassBox 6 Pro
These are the steps taken to help ensure these comparisons are valid.
All softwares used in this test were set to the following parameters:
Speed of Sound = 343.68 m/s
Air Density = 1.2009 kg/m^3
Closed Box (least amount of variables)
Unlined, All Losses set to 10,000 (infinite/lossless)
Qtc = .707
0 ohms Series Resistance
Le NOT Modeled
500 watts input
NOTE: Subwoofer Simulator only accepts Voltage.
Equation used: Vin = sqr(Pe*Re) = 40.447 Volts
These are measured parameters, not manufacturer specs. I own this Driver.
Driver: DAYTON Titanic MKIII (TIT320C-4)
Fs=26.433 Hz
Vas=57.443 L
Qes=0.5448636
Qms=6.6803
Qts=0.5037743
Re=3.2719 ohm
Pe=500W (RMS)
Le=2.5102 mH (NOT USED IN TESTS)
Xmax=18.7 mm
Diam=23.857 cm
Sd= 447.0145 cm^2
Bl=13.3664
Mms=179.1391 grams
Rms=4.453698 kg/s
Cms=202.3751 uM/N
Results: All values at 10Hz
Click link below to view an html page of more images from test.
lsdp.100webspace.net/test5.html
(The last image on this page is an animated gif, with the PEAK excursion graphs scaled and overlayed. )
Observations:
You need to double the power input for BB6P to bring it inline with the other simulations.
And even then, excursion is 1.85mm greater than PEAK avg @ 500w. 1.31mm greater than RMS avg @ 250w. IMO, something strange is going on in BB6P.
I can't account for these small differences. (rounding errors?)
EDIT:
I figured out the small differences are mainly attributable to the way BB6P converts Power to equivalent Voltage. BB6P uses Znom instead of Re. So Vin = sqr(Pe*Znom).
BB6P computed Znom = 3.92628 ohms (1.2*Re) for this driver.
In SubSim @ 250watts this becomes 31.33V. SubSim excursion is then 18.732mm. BB6P excursion is 18.3mm. The .432 difference is then probably due to rounding.
BB6P only shows excursion limiting with 1000w input, leading me to believe that BB6P is assuming input power is PEAK not RMS. With this assumption, BB6P graphs are inline with PEAK values (and correct excursion limiting), ONLY if input power is PEAK (2*PeRMS).
Conclusion:
BB6P assumes input power is PEAK (2*PeRMS) then excursion graphs are realistic(PEAK), and results are similar to other simulations. If WinISD is changed to RMS, you will note that Xmax line changes and the project is still excursion limited. This is correct. WinISD assumes input power is RMS. Now, this excursion graph is similar to BB6P, but in BB6P it does not show excursion limiting!
The other 4 simulation softwares assume input power is RMS and scales graphs correctly as PEAK.
This really bothers me.
If harristech specifies that the graphs are PEAK, then why are they so different? I believe BB6P is giving a user a false impression that a driver will not exceed xmax in their simulations. If using BB6P, you MUST enter PEAK input power (2*PeRMS) in order for the results to be relevant.
Hopefully, you will be able to understand my post! ( I did repeat myself a few times)
If anything is confusing or unclear, feel free to ask!
I welcome any and all comments regarding this test.
Regards,
Michael
My question to harristech:
Hello,I have a pre-purchase question. I was wondering if graphs of excursion and port velocity, reflect RMS or Peak values. In BBP help on cone excursion page, it states peak excursion, but results seems to indicate RMS when compared to other softwares. (I have read conflicting responses as well, on the web). Please clear this up for me.
The response from harristech:
Both the Cone Displacement graph and the Vent Air Velocity graph are based on the peak diaphragm displacement assuming a constant input voltage that the user can control. Perhaps the confusion is due to the fact that both of these graphs default to using the max power rating (Pe) of the driver. We normally recommend that designers take a conservative approach and enter an RMS steady-state maximum power value for the Pe parameter. If they do, then the default voltage used for the Cone Displacement and Vent Air Velocity graphs will be based on the peak excursion at the rated RMS max power of the driver. But the user can enter their own input power or input voltage for these graphs. Internally, the program uses input voltage so an input power level will be converted to voltage based on the nominal impedance of the driver.
Best regards,
Harris Tech Support
support@ht-audio.com
Best regards,
Harris Tech Support
support@ht-audio.com
Ok, I don't accept this. So I did some testing on my own...
Software used for testing:
UniBox
Subwoofer Simulator
LSD (Loudspeaker System Design - my own software - unreleased)
WinISD Pro
BassBox 6 Pro
These are the steps taken to help ensure these comparisons are valid.
All softwares used in this test were set to the following parameters:
Speed of Sound = 343.68 m/s
Air Density = 1.2009 kg/m^3
Closed Box (least amount of variables)
Unlined, All Losses set to 10,000 (infinite/lossless)
Qtc = .707
0 ohms Series Resistance
Le NOT Modeled
500 watts input
NOTE: Subwoofer Simulator only accepts Voltage.
Equation used: Vin = sqr(Pe*Re) = 40.447 Volts
These are measured parameters, not manufacturer specs. I own this Driver.
Driver: DAYTON Titanic MKIII (TIT320C-4)
Fs=26.433 Hz
Vas=57.443 L
Qes=0.5448636
Qms=6.6803
Qts=0.5037743
Re=3.2719 ohm
Pe=500W (RMS)
Le=2.5102 mH (NOT USED IN TESTS)
Xmax=18.7 mm
Diam=23.857 cm
Sd= 447.0145 cm^2
Bl=13.3664
Mms=179.1391 grams
Rms=4.453698 kg/s
Cms=202.3751 uM/N
Results: All values at 10Hz
Click link below to view an html page of more images from test.
lsdp.100webspace.net/test5.html
(The last image on this page is an animated gif, with the PEAK excursion graphs scaled and overlayed. )
Observations:
You need to double the power input for BB6P to bring it inline with the other simulations.
And even then, excursion is 1.85mm greater than PEAK avg @ 500w. 1.31mm greater than RMS avg @ 250w. IMO, something strange is going on in BB6P.
I can't account for these small differences. (rounding errors?)
EDIT:
I figured out the small differences are mainly attributable to the way BB6P converts Power to equivalent Voltage. BB6P uses Znom instead of Re. So Vin = sqr(Pe*Znom).
BB6P computed Znom = 3.92628 ohms (1.2*Re) for this driver.
In SubSim @ 250watts this becomes 31.33V. SubSim excursion is then 18.732mm. BB6P excursion is 18.3mm. The .432 difference is then probably due to rounding.
BB6P only shows excursion limiting with 1000w input, leading me to believe that BB6P is assuming input power is PEAK not RMS. With this assumption, BB6P graphs are inline with PEAK values (and correct excursion limiting), ONLY if input power is PEAK (2*PeRMS).
Conclusion:
BB6P assumes input power is PEAK (2*PeRMS) then excursion graphs are realistic(PEAK), and results are similar to other simulations. If WinISD is changed to RMS, you will note that Xmax line changes and the project is still excursion limited. This is correct. WinISD assumes input power is RMS. Now, this excursion graph is similar to BB6P, but in BB6P it does not show excursion limiting!
The other 4 simulation softwares assume input power is RMS and scales graphs correctly as PEAK.
This really bothers me.
If harristech specifies that the graphs are PEAK, then why are they so different? I believe BB6P is giving a user a false impression that a driver will not exceed xmax in their simulations. If using BB6P, you MUST enter PEAK input power (2*PeRMS) in order for the results to be relevant.
Hopefully, you will be able to understand my post! ( I did repeat myself a few times)
If anything is confusing or unclear, feel free to ask!
I welcome any and all comments regarding this test.
Regards,
Michael