Resonances of open air columns
This isnt perfect but it might be close if you set it up
For the TS parameters sized as a pipe. Note: open and closed are inside the pipes(1/3-1/3-1/3)
This isnt perfect but it might be close if you set it up
For the TS parameters sized as a pipe. Note: open and closed are inside the pipes(1/3-1/3-1/3)
TVR-
Unibox takes damping and leakage into account, and guess-what? It does bandpass models too! That's what I used to do mine.
FWIW, I modeled the RSS265 at one point, and it did not look like a good driver for a bandpass alignment for my own objectives. It would work in a bandpass, but not the direction I wanted to go. There are just drivers that were better suited.
I still say the PR-Bandpass is the novel approach to streamline and slim down a bandpass design, while fixing the inherent problems average bandpass designs with ports inherently possess.
At least you learned a lot in the endeavor,
Wolf
Unibox takes damping and leakage into account, and guess-what? It does bandpass models too! That's what I used to do mine.
FWIW, I modeled the RSS265 at one point, and it did not look like a good driver for a bandpass alignment for my own objectives. It would work in a bandpass, but not the direction I wanted to go. There are just drivers that were better suited.
I still say the PR-Bandpass is the novel approach to streamline and slim down a bandpass design, while fixing the inherent problems average bandpass designs with ports inherently possess.
At least you learned a lot in the endeavor,
Wolf
In WinISD, click on "advanced" below the dialogue box for port tuning frequency to access Q values for overall box losses, (Ql) Absorption (Qa) and port losses (Qp).
HTH,
David.
Attachments
Reality Check
HR Z-Max 40.8 Ohm @ 44.89 Hz It have no Ff or Qtc I could find.
Peak of response, 66 Hz, 89.4 dB. 20 Hz, 73 dB, 200 Hz, 84.5 dB
WinISD
Z-Max 28.9 Ohms @ 45.4 Hz. Fc 47.55 Qtc .622
Peak of response 110 Hz, 89 dB, 20 Hz 72 dB, 200 Hz 87.1 dB
Bagby
Z-Max 33.12 Ohms @ 45.4 Hz Fc 45.55, Qtc .580
Peak response > 100 Hz ( shows flat line) 89 dB 20 Hz 73 dB
Measured
Z-Max 33.9 Ohms @ Fs 44.6 Hz, Qtc .705
See graph for actual acoustic response
Who is correct? None. Who is closest? Well not any of them really. HR on the "hump" center, Bagby on Z max, None of them on HF slope at all believable, though I guess the assumed flat line from Bagby to be closest. So, they are clearly making different assumptions as the T/S parameters are the same. Fc did come pout very close, so I am not going to pull out the old books and try to calculate it by hand. That Qtc was so far off is concerning, but thinking of all the boxes I have built, I cut to a simulated .6 and then try to stuff to .5. Don't always get there and have had to make a bigger box. (RSS265's won't, but my Peerless XLSS did. Little Dayton Rs150's built matched WinISD pretty well)
Fl and Fa, 10, 100. box tested with no leaks.
If anything is to be learned, it is why one must prototype and test. I see so many threads about first time builders with beautiful woodwork and no data.
I used this sub in my office for several years using just the plate amp crossover and an HP cap on the amp to the mains. It worked pretty well. Better than the simulations really.
Actually, driver in-box is far better than the Dayton data sheet would suggest as it shows the steeper LP response. ( OBE driver but datasheet still posted is you search)
Can of worms is getting fuller. Next is to model a QB4 or C4 to learn HR and Bagby better. Put a port on this box ( 30L) and measure it. Then BP-4. It could be one tool is better for one and another for a different alignment.
I do not have any paid programs like BB-Pro.
HR Z-Max 40.8 Ohm @ 44.89 Hz It have no Ff or Qtc I could find.
Peak of response, 66 Hz, 89.4 dB. 20 Hz, 73 dB, 200 Hz, 84.5 dB
WinISD
Z-Max 28.9 Ohms @ 45.4 Hz. Fc 47.55 Qtc .622
Peak of response 110 Hz, 89 dB, 20 Hz 72 dB, 200 Hz 87.1 dB
Bagby
Z-Max 33.12 Ohms @ 45.4 Hz Fc 45.55, Qtc .580
Peak response > 100 Hz ( shows flat line) 89 dB 20 Hz 73 dB
Measured
Z-Max 33.9 Ohms @ Fs 44.6 Hz, Qtc .705
See graph for actual acoustic response
Who is correct? None. Who is closest? Well not any of them really. HR on the "hump" center, Bagby on Z max, None of them on HF slope at all believable, though I guess the assumed flat line from Bagby to be closest. So, they are clearly making different assumptions as the T/S parameters are the same. Fc did come pout very close, so I am not going to pull out the old books and try to calculate it by hand. That Qtc was so far off is concerning, but thinking of all the boxes I have built, I cut to a simulated .6 and then try to stuff to .5. Don't always get there and have had to make a bigger box. (RSS265's won't, but my Peerless XLSS did. Little Dayton Rs150's built matched WinISD pretty well)
Fl and Fa, 10, 100. box tested with no leaks.
If anything is to be learned, it is why one must prototype and test. I see so many threads about first time builders with beautiful woodwork and no data.
I used this sub in my office for several years using just the plate amp crossover and an HP cap on the amp to the mains. It worked pretty well. Better than the simulations really.
Actually, driver in-box is far better than the Dayton data sheet would suggest as it shows the steeper LP response. ( OBE driver but datasheet still posted is you search)
Can of worms is getting fuller. Next is to model a QB4 or C4 to learn HR and Bagby better. Put a port on this box ( 30L) and measure it. Then BP-4. It could be one tool is better for one and another for a different alignment.
I do not have any paid programs like BB-Pro.
Attachments
Unibox is new to me. I'll check it out.
Yea, neither the Titanic nor RS265 look to be well suited for BP.
Every build is to learn something. Not really any other reason to have such an expensive hobby. Smart people just go buy something which is far cheaper in the long run.
Yea, neither the Titanic nor RS265 look to be well suited for BP.
Every build is to learn something. Not really any other reason to have such an expensive hobby. Smart people just go buy something which is far cheaper in the long run.
Quick load into Unibox. Nifty program. Sealed comes out similar to WinISD, but with the assumes no LP roll-off just like Bagby. I have not moved down to examine the BP alignment carefully, but I can see it is quite different from WinISD.
To compare apples to at least round red things, I am setting for a no-leak and no stuffing loss parameters. I test for leaks with a stethoscope and tune with stuffing.
I am not opposed to PRs, just this project did not have the physical space for it, the sub being set into a cubical over an adjacent closet with limited dimensions. In most instances, one would have room for equivalent PR's one size larger on the other walls. If I had known the need for a larger cabinet, I might have made the linen closet shorter to give a bigger shelf facing the HT.
To compare apples to at least round red things, I am setting for a no-leak and no stuffing loss parameters. I test for leaks with a stethoscope and tune with stuffing.
I am not opposed to PRs, just this project did not have the physical space for it, the sub being set into a cubical over an adjacent closet with limited dimensions. In most instances, one would have room for equivalent PR's one size larger on the other walls. If I had known the need for a larger cabinet, I might have made the linen closet shorter to give a bigger shelf facing the HT.
OK, on to BP-4. HUGE difference. Only if ignoring port resonance is there any correlation between WinISD and Unibox. Add in port resonance, and I think I can believe Unibox by the basic shape trend as what I saw with the RSS265's and basic shape in HR. WinISD to Unibox do have the same port calculations for the same box and target. So maybe one mystery solved.
So this lesson is WinISD is not suitable for BP-4 ported design.
Unibox also lets you see how to tune a PR for good response and how it does not have quite the extension as ported. I knew that, but had not bothered to model as I never needed to. None of these look like the simulate a BP with a PR.
So this lesson is WinISD is not suitable for BP-4 ported design.
Unibox also lets you see how to tune a PR for good response and how it does not have quite the extension as ported. I knew that, but had not bothered to model as I never needed to. None of these look like the simulate a BP with a PR.
Did you use the driver's semi-inductance parameters in the Hornresp sim?
In any case, Hornresp models the power response, not the frequency response if measured at 1M in front of the subwoofer. So, above say 200 Hz I'd expect to see deviations between the Hornresp and the measured response.
Makes even less sense. For my real measurement, I should have laid it on the ground outside for realistic 2 pi. FR and not just rely on Holm gating to clean up the reflections. I measured with it conveniently on a table @ 1M. The sweep based tools were of course all over the place higher.
Ah, found the semi inductance parameters. Not a clue how I would determine them; Leb, Le, Re', Ke, Rss So, for sure I had that turned off. Not quite sure even what the Le as calculated by DATS comes from. It is sure not with the VC bound immobile.
YUP! Lossy LE is what shifts the peak. One mystery solved. So, it suggests the other tools are not as accurate for drivers with massive motors.
So next remaining mystery is the LP slope.
Another is how my first sim has Fta in the upper right and this one Cir. Was very obstinate getting F23 on set to zero.
Datapoint: Just for reference, best I could so stuffing is reduce Qtc by .1. About what I have done elsewhere. So roughly .7 to .6. It takes progressively larger box as the Q goes down.
Ah, found the semi inductance parameters. Not a clue how I would determine them; Leb, Le, Re', Ke, Rss So, for sure I had that turned off. Not quite sure even what the Le as calculated by DATS comes from. It is sure not with the VC bound immobile.
YUP! Lossy LE is what shifts the peak. One mystery solved. So, it suggests the other tools are not as accurate for drivers with massive motors.
So next remaining mystery is the LP slope.
Another is how my first sim has Fta in the upper right and this one Cir. Was very obstinate getting F23 on set to zero.
Datapoint: Just for reference, best I could so stuffing is reduce Qtc by .1. About what I have done elsewhere. So roughly .7 to .6. It takes progressively larger box as the Q goes down.
In Unibox, you have to design the bandpass, and then model the vented chamber with the driver and PR and adjust for the tuning, or vice versa. It's a 2-stage process, but it works.
That's how I did it...
Wolf
That's how I did it...
Wolf
"These additional parameters are not usually published for subwoofer drivers, but they can be derived from their measured impedance curves."
But the paper makes no hint of how. As the model with only lossy shows about a 6 dB slope and measured is about 2 dB, based on this example, it may be pretty close. I am just no closer to achieving it.
Thiele Small Parameters
Provides some additional insight, but references both motional and blocked impedance measure. That would imply destroying a driver by gluing the VC in place as best as I understand. Or for a big woofer, can you clamp it at some slight offset to be enough?
Then it comments " can be derived from the difference". No help. Unfortunately, my AES paper anthologies do not go as far as 2011.
OK, Found this
Semi-Le_Calc: Calculator for Advanced Inductance Model Incorporating Semi-Inductance
Did the add-ins for Excel. I will open it up AFTER coffee is ready. 😀
Making my head hurt, but I wanted to step it up and learn some more. The entire semi-inductance topic was not in the domain when I thought I understood this stuff. Post D'Apolitto.
Please, keep beating me up! This is fun. Odd. I did not remember reference to these features in Excel Scientific and Engineering Handbook Guess I had better go re-read it. Excel is an incredible program.
But the paper makes no hint of how. As the model with only lossy shows about a 6 dB slope and measured is about 2 dB, based on this example, it may be pretty close. I am just no closer to achieving it.
Thiele Small Parameters
Provides some additional insight, but references both motional and blocked impedance measure. That would imply destroying a driver by gluing the VC in place as best as I understand. Or for a big woofer, can you clamp it at some slight offset to be enough?
Then it comments " can be derived from the difference". No help. Unfortunately, my AES paper anthologies do not go as far as 2011.
OK, Found this
Semi-Le_Calc: Calculator for Advanced Inductance Model Incorporating Semi-Inductance
Did the add-ins for Excel. I will open it up AFTER coffee is ready. 😀
Making my head hurt, but I wanted to step it up and learn some more. The entire semi-inductance topic was not in the domain when I thought I understood this stuff. Post D'Apolitto.
Please, keep beating me up! This is fun. Odd. I did not remember reference to these features in Excel Scientific and Engineering Handbook Guess I had better go re-read it. Excel is an incredible program.
Hmmm. Looks like Woffer Tester may calculate Semi-Inductance. They just don't call it that.
Krm, Erm, Kxm, Exm , Kms and Rms
Though I do not know how to correlate them to Re', Leb, Le, Ke and Rss
I do have a calibrated low Ohms ( fluke) , so I guess I can measure Re' accurately and see how it differs from WT measurement @ 1 Hz.
Krm, Erm, Kxm, Exm , Kms and Rms
Though I do not know how to correlate them to Re', Leb, Le, Ke and Rss
I do have a calibrated low Ohms ( fluke) , so I guess I can measure Re' accurately and see how it differs from WT measurement @ 1 Hz.
Those are the Wright parameters, an earlier attempt to model the same sort of behaviour that the semi-inductance parameters are used to model. I don't think that they are interchangeable.
The semi-inductance parameters can be derived using an impedance ZMA file generated for the woofer and the semi-inductance workbook available from my website.
The semi-inductance parameters can be derived using an impedance ZMA file generated for the woofer and the semi-inductance workbook available from my website.
Brian,
Got it downloaded. Made the changes to Excel. ( never stops amazing me, Excel) Will give it a go after lunch.
They advertise improvements with DATS V3, so I asked them if they calculate it. I doubt it. Vituix also can accept semi-inductance in it's box designer.
I did not realize all that great stuff was your site. Super!
Ironic though. I am not likely to change out my living room Peerless XLSS, Qtc .5 sub as I don't have the room anyway, and my HT sub I just built ( twin RSS265, Qtc .65) will probably do, so the goal is to understand why the models were so far off, just because I am a bit A-R and want to know! I doubt the Dayton's are very well suited for BP-4, but if I assemble in place, there is a possibility a BP-4 cabinet with twin 12 PRs might physically fit. Never used a PR. So translating a port to PR specs is yet another exercise. I wonder, if using two, do they have the same mechanical asymmetry so reversing one as I have done on the DRs reduce their non-linearities?
Got it downloaded. Made the changes to Excel. ( never stops amazing me, Excel) Will give it a go after lunch.
They advertise improvements with DATS V3, so I asked them if they calculate it. I doubt it. Vituix also can accept semi-inductance in it's box designer.
I did not realize all that great stuff was your site. Super!
Ironic though. I am not likely to change out my living room Peerless XLSS, Qtc .5 sub as I don't have the room anyway, and my HT sub I just built ( twin RSS265, Qtc .65) will probably do, so the goal is to understand why the models were so far off, just because I am a bit A-R and want to know! I doubt the Dayton's are very well suited for BP-4, but if I assemble in place, there is a possibility a BP-4 cabinet with twin 12 PRs might physically fit. Never used a PR. So translating a port to PR specs is yet another exercise. I wonder, if using two, do they have the same mechanical asymmetry so reversing one as I have done on the DRs reduce their non-linearities?
I get "runtime error, subscript out of range"
.zma file with Z and Phase, space delimited generated by Woffer Tester. Stripped the comment lines.
Is the "+" for positive numbers a problem?
File as attached
.zma file with Z and Phase, space delimited generated by Woffer Tester. Stripped the comment lines.
Is the "+" for positive numbers a problem?
File as attached
So, I modeled 4 enclosures with two drivers. ( Dayton Titanic 10 and RSS265) One low Qts, mode moderate. Used WinISD and ignore the inaccuracies for this exercise as I now understand them.
Sealed, ported, BP-4, and PR, ported.
I then applied the expected 4th order LP crossover of 100 Hz.
I applied a 4th order HP of 20 Hz. I am not a deep special effects fan.
I then filtered to approximate room gain. (basically close to the low Q sealed) This was verified by looking at the ARC EQ curve and room mode simulations. Very close so believeable.
FWIW, after one applies the crossover and simulation to the mid-bass, the group delay difference was not great.
For the same 1.5 cu ft space available.
Ports on both ported were unworkable, but good for simulation ( 2 to 3 foot port)
PRs were able to tune very close to the ported curve, both QB4 ad BP-4
All said and done, all 4 (8) can have about the same FR in use.
A single big 12 inch PR was sufficient for the two ported, but would have required two for the BP-4.
All said and done, using the same total Vb, a pair of the drivers as sealed still fits the as expected use curve better with significantly less excursion and more overhead. PR-s could make the BP-4 work, but at the cost of lower efficiency and far worse transient response.
So, all done. Finished. I go back to what I learned 40 years ago. For music and high fidelity, sealed low Q is still the better solution. Protect with a HP filter ( all drivers should have this protection) If I were to build a separate LFE sub, I might choose BP-4 or PB-6. ( two PRs for either) with bigger drivers.
I learned HornRes gives a better simulation of a design, but WinISD is still easier for the initial design.
For my education, I still want to get the semi-inductance simulation to work. ( error inputting data to the spreadsheet)
Sealed, ported, BP-4, and PR, ported.
I then applied the expected 4th order LP crossover of 100 Hz.
I applied a 4th order HP of 20 Hz. I am not a deep special effects fan.
I then filtered to approximate room gain. (basically close to the low Q sealed) This was verified by looking at the ARC EQ curve and room mode simulations. Very close so believeable.
FWIW, after one applies the crossover and simulation to the mid-bass, the group delay difference was not great.
For the same 1.5 cu ft space available.
Ports on both ported were unworkable, but good for simulation ( 2 to 3 foot port)
PRs were able to tune very close to the ported curve, both QB4 ad BP-4
All said and done, all 4 (8) can have about the same FR in use.
A single big 12 inch PR was sufficient for the two ported, but would have required two for the BP-4.
All said and done, using the same total Vb, a pair of the drivers as sealed still fits the as expected use curve better with significantly less excursion and more overhead. PR-s could make the BP-4 work, but at the cost of lower efficiency and far worse transient response.
So, all done. Finished. I go back to what I learned 40 years ago. For music and high fidelity, sealed low Q is still the better solution. Protect with a HP filter ( all drivers should have this protection) If I were to build a separate LFE sub, I might choose BP-4 or PB-6. ( two PRs for either) with bigger drivers.
I learned HornRes gives a better simulation of a design, but WinISD is still easier for the initial design.
For my education, I still want to get the semi-inductance simulation to work. ( error inputting data to the spreadsheet)
Youre placing the simmed HR speaker design results into REW ‘room’ profile to sim the expected audible result? Im curious as to the ways you can skew that if wanting to look at certain ideas! I never thought of such a thing until i read this(if i read it correctly)? But the potential here is exciting
Ive done the opposite (loooking for dsp) but never thought of the acoustical solutions to the room inside the box?!
Ive done the opposite (loooking for dsp) but never thought of the acoustical solutions to the room inside the box?!