Hi ! I hope someone can help me please?
I'm using ( i.e. trying to, lol) the FRD Tools, specifically BDS, the Baffle Diffraction simulator to model my old Vifa P25WO-00-08 , a 10inch woofer and my 'proposed' mid, a 5inch midrange, the Seas MCA15RCY.
The manufacturers test boxes indicate Finite baffles with volumes of 50 and 20 Litres respectively. But BDS requires baffle dimensions. I have been unsuccessful trying to email Vifa/Peerless and Seas. So, I'm wondering please if anyone has experience with these drivers, and could suggest appropriate test box baffle dimensions, please?
I know they are not IEC and therefore not 'infinite'.
Interestingly, the MCA15 SPL specs say a 'dotted line' indicates an infinite baffle response, but it is not shown on the graph!
My friend Omni, is using the Seas CA15RLY 5" mid/woofer in a similar 3-way and its 'dotted line' infinite baffle response IS shown on its SPL
graph. If anyone could help please, I'd be very gratefull...thank you! grant
I'm using ( i.e. trying to, lol) the FRD Tools, specifically BDS, the Baffle Diffraction simulator to model my old Vifa P25WO-00-08 , a 10inch woofer and my 'proposed' mid, a 5inch midrange, the Seas MCA15RCY.
The manufacturers test boxes indicate Finite baffles with volumes of 50 and 20 Litres respectively. But BDS requires baffle dimensions. I have been unsuccessful trying to email Vifa/Peerless and Seas. So, I'm wondering please if anyone has experience with these drivers, and could suggest appropriate test box baffle dimensions, please?
I know they are not IEC and therefore not 'infinite'.
Interestingly, the MCA15 SPL specs say a 'dotted line' indicates an infinite baffle response, but it is not shown on the graph!
My friend Omni, is using the Seas CA15RLY 5" mid/woofer in a similar 3-way and its 'dotted line' infinite baffle response IS shown on its SPL
graph. If anyone could help please, I'd be very gratefull...thank you! grant
Model the drivers in WinISD, or Unibox in your intended enclosures, and splice those responses to the MFG's plots at around 300 Hz.
To believe the MFG's anechoic plots are accurate below 200 Hz is wishful thinking anyway.
C
To believe the MFG's anechoic plots are accurate below 200 Hz is wishful thinking anyway.
C
Hello 'C' ! Thanks for your comments.
I had already saved the results from Unibox for both mybox and the manuf's test boxes. So I think that part is ok. My problem seems to concern BDS (baffle diffraction simulator) , and if I understand it correctly - it computes baffle-step/diffraction for each driver (as distinct from Unibox results) for both box types.
To do this in BDS for a say 50L closed testbox it requires baffle dimensions. 'CC" are you saying I can approximately?
model baffle-step and diffraction in Unibox by 'splicing? I don't know a lot about the FRCtools, but this is an interesting concept. I note your comment about mfg's plots below 200Hz - thanks, grant
I had already saved the results from Unibox for both mybox and the manuf's test boxes. So I think that part is ok. My problem seems to concern BDS (baffle diffraction simulator) , and if I understand it correctly - it computes baffle-step/diffraction for each driver (as distinct from Unibox results) for both box types.
To do this in BDS for a say 50L closed testbox it requires baffle dimensions. 'CC" are you saying I can approximately?
model baffle-step and diffraction in Unibox by 'splicing? I don't know a lot about the FRCtools, but this is an interesting concept. I note your comment about mfg's plots below 200Hz - thanks, grant
'CC'
I might have misread / misunderstood your post, sorry. I do have WinISD Pro here somewhere, so I'll try to learn it better and see how my BStep/Diffraction (in unknown baffle dimensions) question might be
resolved. cheers, grant
I might have misread / misunderstood your post, sorry. I do have WinISD Pro here somewhere, so I'll try to learn it better and see how my BStep/Diffraction (in unknown baffle dimensions) question might be
resolved. cheers, grant
Hi , to anyone who would like to kindly advise me please!
The Seas CA15RLY SPL plot shows an Infinite Baffle response about maybe 2dB? higher from say 100 to 500Hz, than the 20 Litre closed box response. I'm wondering if it would be valid to (very) approximate the MCA15RCY's Infinite Baffle response based on the CA. Different drivers I know, my MCA is a midrange, the CA is a mid/woofer.
What do you think, please? Would my very rough MCA graph, attached, be slightly appropriate? thanks, grant
The Seas CA15RLY SPL plot shows an Infinite Baffle response about maybe 2dB? higher from say 100 to 500Hz, than the 20 Litre closed box response. I'm wondering if it would be valid to (very) approximate the MCA15RCY's Infinite Baffle response based on the CA. Different drivers I know, my MCA is a midrange, the CA is a mid/woofer.
What do you think, please? Would my very rough MCA graph, attached, be slightly appropriate? thanks, grant
G’day, Grant.
Yes, the red trace appears to be the in-box response, but unless you are going to put your mid in a 20 liter enclosure, it doesn’t help you much.
In general: To effectively model a driver in-box., the anechoic response needs to be modified to resemble the effects the enclosure volume has on the response, and the diffraction effects of the baffle. The impedance files should also be modified to represent the changes due to the enclosure. Done properly, and assuming the manufacturers data is accurate, the resultant files will closely emulate actual measured data.
What I’d suggest is to model your drivers in Unibox (or WinISD) to your intended parameters and save that modeled response as a .frd file. It doen’t appear Unibox exports .frd files, (and WinIDS does not either) but you can cut and paste it into SPLtrace to create the appropriate .frd and .zma files.
Using the FRC in editor mode splice the modeled box response to the anechoic response for each woof at around 300 Hz, and save this file.
Now using BDS model your baffle size, speaker position, and edge choice, and save those files. Note that with respect to the anechoic responses, these should represent a loss at lower frequencies of –6 dB from nominal.
Finally, in FRC, import your files, sum, and derive minimum phase. Don’t forget to sum the tweeter diffraction effects as well. Typically they will make a significant impact around the crossover frequency.
Roman Bednarek has written a tutorial on using the FRD tools you might find helpful:
http://www.rjbaudio.com/Audiofiles/FRDtools.html
If this all seems too daunting, email me with details of your design and I’ll generate the appropriate files for you.
cc00541@neb.rr.com
Curt
Yes, the red trace appears to be the in-box response, but unless you are going to put your mid in a 20 liter enclosure, it doesn’t help you much.
In general: To effectively model a driver in-box., the anechoic response needs to be modified to resemble the effects the enclosure volume has on the response, and the diffraction effects of the baffle. The impedance files should also be modified to represent the changes due to the enclosure. Done properly, and assuming the manufacturers data is accurate, the resultant files will closely emulate actual measured data.
What I’d suggest is to model your drivers in Unibox (or WinISD) to your intended parameters and save that modeled response as a .frd file. It doen’t appear Unibox exports .frd files, (and WinIDS does not either) but you can cut and paste it into SPLtrace to create the appropriate .frd and .zma files.
Using the FRC in editor mode splice the modeled box response to the anechoic response for each woof at around 300 Hz, and save this file.
Now using BDS model your baffle size, speaker position, and edge choice, and save those files. Note that with respect to the anechoic responses, these should represent a loss at lower frequencies of –6 dB from nominal.
Finally, in FRC, import your files, sum, and derive minimum phase. Don’t forget to sum the tweeter diffraction effects as well. Typically they will make a significant impact around the crossover frequency.
Roman Bednarek has written a tutorial on using the FRD tools you might find helpful:
http://www.rjbaudio.com/Audiofiles/FRDtools.html
If this all seems too daunting, email me with details of your design and I’ll generate the appropriate files for you.
cc00541@neb.rr.com
Curt
Curt,
Wow! and g'day mate! lol Thank you so much! I am 'stunned' to read your extremely generous offer of generating files for me! Awesome kindness indeed on your part. Yes I am very much a beginner with
the FRD tools and speaker building in general!. I was 'FRD simming' at the local library, but unfortunately, today lost access to the PC. So, now I'm 'up the creek' so to speak.
Omni today very kindly emailed to me a Madisound MCA15RCY plot in an Infinite baffle. Thanks Omni! The IB response looks lower dB wise than I would have expected - its attached. Its very late here now, so if its ok, I'll read your post thoroughly tomorrow, and hopefully make a sensible reply then. cheers! grant (many thanks for Roman's link also) I shrank the file to 90kB but it won't load?
Wow! and g'day mate! lol Thank you so much! I am 'stunned' to read your extremely generous offer of generating files for me! Awesome kindness indeed on your part. Yes I am very much a beginner with
the FRD tools and speaker building in general!. I was 'FRD simming' at the local library, but unfortunately, today lost access to the PC. So, now I'm 'up the creek' so to speak.
Omni today very kindly emailed to me a Madisound MCA15RCY plot in an Infinite baffle. Thanks Omni! The IB response looks lower dB wise than I would have expected - its attached. Its very late here now, so if its ok, I'll read your post thoroughly tomorrow, and hopefully make a sensible reply then. cheers! grant (many thanks for Roman's link also) I shrank the file to 90kB but it won't load?
Hi Curt,
I re-read your very considered reply, but unfortunately its late here again now, and I didn't understand all of it. I haven't yet 'played with' the FRC Combiner , and unfortunately have lost access to the s'sheet as I mentioned.
I am still amazed to learn of your offer. It seems like a whole lot of work on your part just to help me out. Of course I'd be thrilled, and extremely appreciative but are you really sure you want to invest so much time in doing this for me? I don't want to lose such a valuable opportunity, but I couldn't repay your effort , except by being
extremely grateful! If you still want to proceed, I guess you need to know drivers, placement on baffle, box size, port dimensions,
basically everything. many thanks and cheers, grant
I re-read your very considered reply, but unfortunately its late here again now, and I didn't understand all of it. I haven't yet 'played with' the FRC Combiner , and unfortunately have lost access to the s'sheet as I mentioned.
I am still amazed to learn of your offer. It seems like a whole lot of work on your part just to help me out. Of course I'd be thrilled, and extremely appreciative but are you really sure you want to invest so much time in doing this for me? I don't want to lose such a valuable opportunity, but I couldn't repay your effort , except by being
extremely grateful! If you still want to proceed, I guess you need to know drivers, placement on baffle, box size, port dimensions,
basically everything. many thanks and cheers, grant
Hi Curt,
If you would like to join our little thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=88567
you'd be very welcome , of course! grant
If you would like to join our little thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=88567
you'd be very welcome , of course! grant
- Status
- Not open for further replies.