Dear wise HR gurus, can I ask your advice? I am attempting to sim this cab to learn a bit more about horns and bonus points for finding a good driver for it on the cheap.
Some basic questions:
Single driver, right?
This is a unique flare but use exp?
Can you confirm I calculate interior cab area less horn volume in schematic diagram screen for Vrc?
Thoughts on Atc and Vtc? I assume not needed.
Lpt is just thickness of horn material?
I assume I have to take the sums of the horn output and the vented (data for horn removed) to get the cabs output?
What I am getting with PA380 (goal driver) is attached.
As usual, ridicule and sarcasm encouraged... 😀
Some basic questions:
Single driver, right?
This is a unique flare but use exp?
Can you confirm I calculate interior cab area less horn volume in schematic diagram screen for Vrc?
Thoughts on Atc and Vtc? I assume not needed.
Lpt is just thickness of horn material?
I assume I have to take the sums of the horn output and the vented (data for horn removed) to get the cabs output?
What I am getting with PA380 (goal driver) is attached.
As usual, ridicule and sarcasm encouraged... 😀
Attachments
Spent some more time fooling around and on a whim I put in the JBL 2220 and I really like how it sims so surely I am doing something wrong... 😀
Gray line is vented with horn data removed (S1,S2,L1) and black line is horn with vent removed (Ap, Lpt). Strangely enough, the horn sims the same with the vent...
Not looking for someone to run numbers just some criticism, like this wrong/off etc. THANKS
Gray line is vented with horn data removed (S1,S2,L1) and black line is horn with vent removed (Ap, Lpt). Strangely enough, the horn sims the same with the vent...
Not looking for someone to run numbers just some criticism, like this wrong/off etc. THANKS
Attachments
Hi Zwiller,
Looking @ the Hornresp Input screen in Post #1, you are using Ap1/Lpt this does not look right. This should be Ap/Lpt for a vented rear chamber port, or, Ap1/Lp for a throat adaptor. Something strange there, maybe an older version? I'm comparing to 3920-150611. The throat chamber data just looks wrong.
You may also try the Compound Horn (CH) driver arrangement, this allows you to use the S5/S6 segment for the port. The first three segments are still for the horn. This arrangement is particularly designed for this type of enclosure (I think 🙂 ).
Also, have you masked resonances (Tools/options/...)?
Regards,
Looking @ the Hornresp Input screen in Post #1, you are using Ap1/Lpt this does not look right. This should be Ap/Lpt for a vented rear chamber port, or, Ap1/Lp for a throat adaptor. Something strange there, maybe an older version? I'm comparing to 3920-150611. The throat chamber data just looks wrong.
You may also try the Compound Horn (CH) driver arrangement, this allows you to use the S5/S6 segment for the port. The first three segments are still for the horn. This arrangement is particularly designed for this type of enclosure (I think 🙂 ).
Also, have you masked resonances (Tools/options/...)?
Regards,
Oliver,
Thanks. Good eye! Just updated HR today so I am running same same as you now. Corrected Ap/Lpt. Now I can finally choose output to see horn vs port. So the sim shows both now! Port response seems rather peaky. Maybe this is intended or old school bass but if I reduce the port area the response flattens and deepens and I likey! Curious about the ports data. Gonna double check my math on that.
I posted the wrong image of the HR inputs... There's no data in the throat (Vtc/Atc). I was just throwing some data in there to see what it did and saved it by mistake and posted it.
With CH, if S5 is inside port and S6 is outside? It won't let me add L56? File attached if you want to play with it.
Yes, resonances masked.
Parabolic is working now... That a better sim for this horn you think?
Thanks. Good eye! Just updated HR today so I am running same same as you now. Corrected Ap/Lpt. Now I can finally choose output to see horn vs port. So the sim shows both now! Port response seems rather peaky. Maybe this is intended or old school bass but if I reduce the port area the response flattens and deepens and I likey! Curious about the ports data. Gonna double check my math on that.
I posted the wrong image of the HR inputs... There's no data in the throat (Vtc/Atc). I was just throwing some data in there to see what it did and saved it by mistake and posted it.
With CH, if S5 is inside port and S6 is outside? It won't let me add L56? File attached if you want to play with it.
Yes, resonances masked.
Parabolic is working now... That a better sim for this horn you think?
Attachments
Hi Zwiller,
It's hard to tell how this port will interact w/ the horn opening. I changed the simulation to CH, and added a small throat chamber and duct coupling over to S1. I tried different value for S6, finally typed in your horn opening using S6/L56 as place holders; that got rid of the peak. Another one that will take some measurements to verify the simulation. Could also be (and I'm purely guessing here) that the opening was to be used w/ some damping material over it? Have you found any additional data on the Community horns original use?
Regards,
P.S.: Is the box depth correct? I forgot about adding a 2nd segment to get the Wizard to turn on, e.g.: S3 same as S2, and L23=0.01.
It's hard to tell how this port will interact w/ the horn opening. I changed the simulation to CH, and added a small throat chamber and duct coupling over to S1. I tried different value for S6, finally typed in your horn opening using S6/L56 as place holders; that got rid of the peak. Another one that will take some measurements to verify the simulation. Could also be (and I'm purely guessing here) that the opening was to be used w/ some damping material over it? Have you found any additional data on the Community horns original use?
Regards,
P.S.: Is the box depth correct? I forgot about adding a 2nd segment to get the Wizard to turn on, e.g.: S3 same as S2, and L23=0.01.
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Yep. beat me to it except......... the vent's in the horn, not outside it, so it's a hybrid 6th order that as best I can tell can't accurately be simmed in HR unless the new 8th order option can do it.
GM
Thanks guys. Community is not 100% sure this is theirs but I will reach out to them again and see what shakes out. Oliver, did you see my other thread? http://www.diyaudio.com/forums/subwoofers/275639-id-mid-horn-2.html#post4362105 If so, what other data might help?
Box depth is was 8" from rear of port to interior cabinet back. Does this need to be from rear of woofer, down back of cabinet, and to port/horn 2 now?
You guys think the 2220 is a suitable driver for this cab without getting overly critical of the sim?
Box depth is was 8" from rear of port to interior cabinet back. Does this need to be from rear of woofer, down back of cabinet, and to port/horn 2 now?
You guys think the 2220 is a suitable driver for this cab without getting overly critical of the sim?
Hi Zwiller,
The direct acoustic short circuit between the rear chamber and the front horn just does not look right. As to the box depth , you need to insert a number that gives a schematic in Hornresp, that looks at least remotely like the original (good luck w/ that in this case).
I tried to move the Hornresp simulation into AkAbak. To do that I had to change the horn flare to Con, and make the front horn from three segments to simulate the exponential flare. The exported Akabak script SPL looks different from the Hornresp SPL. I changed the AkAbak script to more closely reflect the vented horn by adding a 4th horn segment, and venting the rear chamber into the junction between horn segment 3 and 4 w/ a duct using your duct length of 0.32cm. Now the simulation got even worse.
I'll attach the simulations, that way you may be able to sort it out. From what I'm seeing so far this does not look good. (I had to change the extensions on the AkAbak files from .aks to .txt for diyaudio to accept the files.)
Regards,
The direct acoustic short circuit between the rear chamber and the front horn just does not look right. As to the box depth , you need to insert a number that gives a schematic in Hornresp, that looks at least remotely like the original (good luck w/ that in this case).
I tried to move the Hornresp simulation into AkAbak. To do that I had to change the horn flare to Con, and make the front horn from three segments to simulate the exponential flare. The exported Akabak script SPL looks different from the Hornresp SPL. I changed the AkAbak script to more closely reflect the vented horn by adding a 4th horn segment, and venting the rear chamber into the junction between horn segment 3 and 4 w/ a duct using your duct length of 0.32cm. Now the simulation got even worse.
I'll attach the simulations, that way you may be able to sort it out. From what I'm seeing so far this does not look good. (I had to change the extensions on the AkAbak files from .aks to .txt for diyaudio to accept the files.)
Regards,
Attachments
Thanks again! Wow those look bad. This is starting to go beyond my knowledge, no akAbak. Do you think my sim in post 4 be correct if the port was not located in the horn but below it? Trying to remain optimistic...
From here I am thinking a more practical approach, throw a driver in and measure it. If it works, great, if not, move on. Since audiohack said he liked the 2220 in his that is the direction I'll probably go first.
From here I am thinking a more practical approach, throw a driver in and measure it. If it works, great, if not, move on. Since audiohack said he liked the 2220 in his that is the direction I'll probably go first.
Hi Zwiller,
Using your Hornresp Export file from Post #4 I generated the AkAbak export, and the SPL graphs do not agree. So there must be something wrong w/ the simulation. Maybe the input data, e.g.: what is the free internal volume, or any of the other dimensions?
Playing around for a moment in AkAbak it looks much better w/ a smaller V_int, and a longer vent, but none of that helps if we don't know that the starting enclosure and driver data is correct.
So, you may have to measure w/ a known driver, and make sure that the enclosure dimensions/data are correct.
Regards,
Using your Hornresp Export file from Post #4 I generated the AkAbak export, and the SPL graphs do not agree. So there must be something wrong w/ the simulation. Maybe the input data, e.g.: what is the free internal volume, or any of the other dimensions?
Playing around for a moment in AkAbak it looks much better w/ a smaller V_int, and a longer vent, but none of that helps if we don't know that the starting enclosure and driver data is correct.
So, you may have to measure w/ a known driver, and make sure that the enclosure dimensions/data are correct.
Regards,
Assuming the earlier HR sim and using an expo flare, which is typical for truncated horns [at least older ones], these sims aren't even remotely correct since this truncated horn's gain BW by itself will be much lower as noted by the sim's 146.07[Hz] Fc [F12], so a bit larger, ergo a bit lower loading than Altec's small A5, A7 series mid-bass/lower mids horn and the vent-in-horn will mostly just cause a notch in its HF response, though with one as big as shown will be a significant one, though for PA it will be mostly 'drowned out' ['lost' in the PA's total distortion].
If it's a low power app, then a small slot vent will suffice and if positioned right at the terminus, then it isn't audible to most folks. For that matter, many folks love these big vent horns [816, 817] in HIFI/HT apps, so have to wonder if the Community's distortion is acceptable at low power: http://www.lansingheritage.org/images/altec/catalogs/1993-pro/1993-40.JPG
GM
here's a hypex flare horn with 2220H (green trace), 80 sq.in. throat, 20.5x20.5" mouth - about a 20" path from mouth to throat, small back chamber - would be interesting to see how your Community (or similar) performs in comparison. Mice have probably eaten the cones as my horns have been stored in a shed for a decade. That distortion was for the K43 - 2220H had roughly 10dB more H2 with a 100Hz fundamental.
An externally hosted image should be here but it was not working when we last tested it.
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Hi GM,
Post #11: "...these sims aren't even remotely correct..."
I think you hit the nail on the head.
There is an error(s?) in the T/S, and probably in the enclosure dimensions.
For starters, the internal volume has to be smaller for the 2220H(or J) (using JBL's T/S) even for a simple vented enclosure, and the duct has to have a smaller cross-section and greater length.
What bothers me more than this particular case, is that I cannot make Hornresp and AkAbak correspond. I need to find the time to look into this some more. I'll probably start w/ a simple vented enclosure, and work my way around from there.
Regards,
Post #11: "...these sims aren't even remotely correct..."
I think you hit the nail on the head.
There is an error(s?) in the T/S, and probably in the enclosure dimensions.
For starters, the internal volume has to be smaller for the 2220H(or J) (using JBL's T/S) even for a simple vented enclosure, and the duct has to have a smaller cross-section and greater length.
What bothers me more than this particular case, is that I cannot make Hornresp and AkAbak correspond. I need to find the time to look into this some more. I'll probably start w/ a simple vented enclosure, and work my way around from there.
Regards,
Hi Y'all,
I just tried a few simulations again, and a bass reflex transfers quite well from Hornresp to AkAbak, but the SPL curves of the BR/FLH that we are looking at in this thread look substantially different between both simulations. I asked a question pertaining to this in the Hornresp thread, and hope that David will find the time to take a look at this.
Regards,
I just tried a few simulations again, and a bass reflex transfers quite well from Hornresp to AkAbak, but the SPL curves of the BR/FLH that we are looking at in this thread look substantially different between both simulations. I asked a question pertaining to this in the Hornresp thread, and hope that David will find the time to take a look at this.
Regards,
Hmm, I used the PA380 since this was the 'goal', not to mention a good choice, so while the basic horn response will be pretty much the same regardless of driver specs, the JBL 2220 has a much higher mass corner, so now I'm thinking that what we're seeing is its extreme rising on axis response when coupled to a large throat, but need to sim it to be sure.
In short, the 2220 may not be a good choice unless a more restrictive throat to accommodate a >~500 Hz XO is desired.
GM
In short, the 2220 may not be a good choice unless a more restrictive throat to accommodate a >~500 Hz XO is desired.
GM
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Yup, that's what it was........sorry for the misdirection. Unfortunately, HR can't sim combined output and horn directivity, so AkAbak ideally needs to be used to sim this.
GM
GM
Anyway, back to our regularly scheduled program.............
I did a quick calculation for the PA380 and used HR to fine tune the vent a bit and for a 450-500 Hz XO with a low power at the terminus rather than in the horn that generates lots of reflections back to the throat, it's limited to an 80 Hz XO.
For a high power vent, change AP = 200, Lpt = 15.
GM
I did a quick calculation for the PA380 and used HR to fine tune the vent a bit and for a 450-500 Hz XO with a low power at the terminus rather than in the horn that generates lots of reflections back to the throat, it's limited to an 80 Hz XO.
For a high power vent, change AP = 200, Lpt = 15.
GM
Hi Y'all,
Naturally, it was just my fading mind that was the problem. See:
http://www.diyaudio.com/forums/subwoofers/119854-hornresp-556.html
Posts #5551 - 5556.
As David points out, the power response in AkAbak corresponds to the SPL chart in Hornresp. Neo Dan has an example Hornresp simulation in Post #5553, which is basically where all this started.
The 2220H will need a small rear chamber, about 80L to 100L, and the duct needs to be reduced in cross-section and needs to be lengthened.
I need to concentrate better, and Zwiller needs to get the correct T/S parameters for the 2220 and measure/calculate the enclosure. It's always something. 🙂
Regards,
Naturally, it was just my fading mind that was the problem. See:
http://www.diyaudio.com/forums/subwoofers/119854-hornresp-556.html
Posts #5551 - 5556.
As David points out, the power response in AkAbak corresponds to the SPL chart in Hornresp. Neo Dan has an example Hornresp simulation in Post #5553, which is basically where all this started.
The 2220H will need a small rear chamber, about 80L to 100L, and the duct needs to be reduced in cross-section and needs to be lengthened.
I need to concentrate better, and Zwiller needs to get the correct T/S parameters for the 2220 and measure/calculate the enclosure. It's always something. 🙂
Regards,
More like 50 L tuned to around 75 Hz based on ancient published specs, but it doesn't affect the extreme rising on axis response that AkAbak highlights, so combined with its low power handling it's not a good option unless a > ~500 Hz XO is desired.
GM
GM
Didn't think you guys would dive in but THANKS! Can't keep with y'all!
Thinking more about my measurements... Cabinet is 32x33.5x24.75 OD and I subtracted .75" from each and think it should have been 1.5". So 30.5x29.75x22.5=20,415.94/1728=11.81ft3=334.42liters gross volume. If I subtract the horn volume from schematic screen of 108.424 that takes us to 226liters. I did not go as far as to remove volume of driver but that appears to be 3.02liters per schematic. Nor did I remove bracing, but that could be a few liters. I am interested in removing the horn to see if there is ID on it and then I get better data. So we're at 222.98liters. Am I way off? Not really looking to reinvent the wheel and mod the cab that much. Double checking TS data next....
Thinking more about my measurements... Cabinet is 32x33.5x24.75 OD and I subtracted .75" from each and think it should have been 1.5". So 30.5x29.75x22.5=20,415.94/1728=11.81ft3=334.42liters gross volume. If I subtract the horn volume from schematic screen of 108.424 that takes us to 226liters. I did not go as far as to remove volume of driver but that appears to be 3.02liters per schematic. Nor did I remove bracing, but that could be a few liters. I am interested in removing the horn to see if there is ID on it and then I get better data. So we're at 222.98liters. Am I way off? Not really looking to reinvent the wheel and mod the cab that much. Double checking TS data next....
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