Ty so much! I have no idea what formula that is, but I looked up the specs for a 1", 2" and 3" dome and copied the trend to 4" and got ~83cm^2 but it appears that you have a better understanding....
I am having a moment....between the frustration of manufacturers not sharing thiele specs for compression drivers and horn resp cutting off my response display at 2000hz for no apparent reason, I'm almost certain I will have to watch my blood pressure from this point on in life....the ignorance is just uncanny. No wonder old people hate everybody....
Btw 72cm^2 is that of a 3" dome....
I am having a moment....between the frustration of manufacturers not sharing thiele specs for compression drivers and horn resp cutting off my response display at 2000hz for no apparent reason, I'm almost certain I will have to watch my blood pressure from this point on in life....the ignorance is just uncanny. No wonder old people hate everybody....
Btw 72cm^2 is that of a 3" dome....
Piston Excursion calculator
You can use this site for a rough estimate of a piston on a flat baffle/closed box.
A horn/wave guide will give you more output due to higher directivity.
You can use this site for a rough estimate of a piston on a flat baffle/closed box.
A horn/wave guide will give you more output due to higher directivity.
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Thank you Earnie! Heres what I have concocted using the 72cm^2 for SD and 2.77 for MD
I spoke of a transition where the detriments of performance at cutoff become a non issue....I think this helps prove my theory...it also aligns with discussion that I have had suggesting the 350hz JMLC is the biggest horn one would use for full range...I feel the resonate of larger horns becomes too exaggerated to play anywhere near the Fc but this isn't the case with smaller horns. Where to draw the line in the sand...might be 350hz. I'm not sure but I think Hornresp measures at 1m correct>?
ps if you calculate HR shows all the range selected...*duh* and *face palm*
I spoke of a transition where the detriments of performance at cutoff become a non issue....I think this helps prove my theory...it also aligns with discussion that I have had suggesting the 350hz JMLC is the biggest horn one would use for full range...I feel the resonate of larger horns becomes too exaggerated to play anywhere near the Fc but this isn't the case with smaller horns. Where to draw the line in the sand...might be 350hz. I'm not sure but I think Hornresp measures at 1m correct>?
ps if you calculate HR shows all the range selected...*duh* and *face palm*
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Even better with the 1.4"/311-90 combo
: http://greatplainsaudio.com/wp-content/uploads/2016/06/311-Series_hfhorn_spec_sheet.pdf
GM
GM I like how you sit in the shadows waiting for a point in the discussion worth your time you've been like a guardian angel through out this project.
The bi-radials I spoke of (made by Docali), I just made the connection that they are reminiscent of the Altecs...I hope he shares his Bi-Radial JMLC when its finished
Now that I can estimate excursion, combined with my theory that smaller horns can be used below cutoff....I can potentially model towards an even smaller horn that will potentially allow me to crossover at 350hz. The counter balance is the loss of directivity...So I still love the big horns, but in the thought of experimentation, I can make educated guesses before making a move. Also, Docali has shown the ability to model horns that can maintin a width while adjusting the fc...so with that in mind, directivity by width can be maintained!
It is completely disrespectful that manufactures are not sharing the thiele specs needed to model by excursion at the very least!!!! I've been blessed with the sd and xmax figures for my driver but there are how many other compression drivers that you guys love that you have no idea what the SD and xmax are !?!?!
you've been like a guardian angel through out this project.The bi-radials I spoke of (made by Docali), I just made the connection that they are reminiscent of the Altecs...I hope he shares his Bi-Radial JMLC when its finished
Now that I can estimate excursion, combined with my theory that smaller horns can be used below cutoff....I can potentially model towards an even smaller horn that will potentially allow me to crossover at 350hz. The counter balance is the loss of directivity...So I still love the big horns, but in the thought of experimentation, I can make educated guesses before making a move. Also, Docali has shown the ability to model horns that can maintin a width while adjusting the fc...so with that in mind, directivity by width can be maintained!
It is completely disrespectful that manufactures are not sharing the thiele specs needed to model by excursion at the very least!!!! I've been blessed with the sd and xmax figures for my driver but there are how many other compression drivers that you guys love that you have no idea what the SD and xmax are !?!?!
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Thank you Earnie! Heres what I have concocted using the 72cm^2 for SD and 2.77 for MD
I spoke of a transition where the detriments of performance at cutoff become a non issue....I think this helps prove my theory...it also aligns with discussion that I have had suggesting the 350hz JMLC is the biggest horn one would use for full range...I feel the resonate of larger horns becomes too exaggerated to play anywhere near the Fc but this isn't the case with smaller horns. Where to draw the line in the sand...might be 350hz. I'm not sure but I think Hornresp measures at 1m correct>?
ps if you calculate HR shows all the range selected...*duh* and *face palm*
I have a JMLC 350hz horn with a 2 inch throat. I currently use an adapter on it to take it down to 1.5 inch.
What kind of beaming would I expect with using this driver at 2"?
I assume I could get it down to 500hz with a steep crossover? Currently using it at 800hz with Linkwitz Riley 12db/oct but would love to play down lower! I get a tiny bit of horn honk at 800hz at the moment.
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I thought horn honk was something that can be eq'd out
How are you voicing the driver? If your driver supports down to 500hz then I'd think yes...http://www.jblproservice.com/pdf/Discrete Sales Models/2452HJ.pdf
You want to trade me for my 1.5" 350hz? I need a 2" to use on the Axi...
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I thought horn honk was something that can be eq'd out
If your driver supports down to 500hz then I'd think yes...
You want to trade me for my 1.5" 350hz? I need a 2" to use on the Axi...
I get honk when I play the driver too low it seams. This could be driver distortion as it is below optimum for a JBL 2452SL (4 inch dia), or the fact that I'm using a 2nd order filter, or somthing wrong with the crossover etc.
I beleve the 2452 has quickly rising distortion below 1000hz (circa 1% by 700/800hz, so it could well be this I am hearing, I have no way of knowing though.
The recommended crossover for a JMLC 350 hz is 520hz, but I do not know the steepness of the curve that assumes.
I bought the 2" inch JMLC with the purpose of having the flexibility of using different drivers (as I can 3D print up to 400mm3), so I might sell for a CD horn, but not looking to trade for a 1.5" sorry!
I am using digital active crossovers. (Hypex Fusion) + convolution and RePhase.
I was under the impression that 2" throats beamed too much for using up to 20khz? Or do I have that wrong?
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• Frequency Response: 500 Hz or Higher, 12 dB Octave Min
http://www.jblproservice.com/pdf/Discrete Sales Models/2452HJ.pdf
2" will beam more, that is correct
Just checked the measurements I found for it:
Shared album - lance bartlett - Google Photos
If this is correct, that would be the cause of the problem going below 800hz with this driver!
Isn't it great how the manufacturers leave us hanging....I know that we can use distortion figures to fill in the blanks but thats usually after you've bought it and measured it on whatever horn...and then hopefully the info gets passed around the DIY community...
Those measurements don't show you what you want, those aren't measurements on a Jmlc 350hz horn....
You have measurement equipment right? Take some measurements...The horn is usually alimiting factor on the low range of the compression driver....if the driver just can't play that low, then its a different story...but yours is rated to 500hz
You would need to monitor distortion with your measuring mic to be confident about whats going on...
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One of the claims of the Purifi Woofer is that Inter modulation Distortion is much lower than comparable drivers and that was one of their design intents.
I'm not trying to suggest it that it is better than the AE drivers you have only that in a space confined situation or one where large speakers are not wanted it offers something that was not available before and does not appear to be just smoke and mirrors.
Be wary of the specs gleaned from that power point as they are not really clear, there is 1mm peak displacement listed and a suggestion that there is only 1mm gap which may be been inferred from the 1mm displacement.
That sounds more like the mechanical limits of the driver and not linear xmax in the same way it would be listed for a dynamic driver.
Volume displacement is a simple formula Sd x excursion, just use the same units for both.
I'm not trying to suggest it that it is better than the AE drivers you have only that in a space confined situation or one where large speakers are not wanted it offers something that was not available before and does not appear to be just smoke and mirrors.
Be wary of the specs gleaned from that power point as they are not really clear, there is 1mm peak displacement listed and a suggestion that there is only 1mm gap which may be been inferred from the 1mm displacement.
That sounds more like the mechanical limits of the driver and not linear xmax in the same way it would be listed for a dynamic driver.
Volume displacement is a simple formula Sd x excursion, just use the same units for both.
Fortunately the JMLC modelling worked for me, I tried to model a SWH and I don't see it making the response or length of horn I expect...
In the video, the guy says @ 50:50,
https://www.diyaudio.com/forums/attachment.php?attachmentid=847153&stc=1&d=1590370960
So if xmax and xmech are on top of each other thats fine. I don't want to hit 123db anyway....its nice to know I'm not going to hit xmax or xmech, in the non PA setting.
In the video, the guy says @ 50:50,
https://www.diyaudio.com/forums/attachment.php?attachmentid=847153&stc=1&d=1590370960
So if xmax and xmech are on top of each other thats fine. I don't want to hit 123db anyway....its nice to know I'm not going to hit xmax or xmech, in the non PA setting.
I use JBL 2450SL on a 240Hz jmlc horn and I have no problem of distorsion below 1khz... If the diaphragm is well centered (that is difficult to obtain).
Currently I use an active 24db/oct filter at 400Hz. It can work at 300 or 350Hz but That's risky.
In the past I've used several drivers on this horn, BMS coaxial driver was OK at 250Hz...with 8 watts SE 300B ,amplifier.
For Camplo, the real issue with this kind of horn (have build lots of jmlc horns in the past) associated with 2" CD driver is the lack of energy in the treble compared with the energy in the medium (due to of axis response).
My experience is that this kind of combo needs tweeter...But if you add a tweeter you need to look at the response of axis to choose the good filter, the good frequency, the good tweeter, to avoid a bump at the crossover frequency (with a CD tweeter for example, or with a High directivity tweeter but quite constant directivity).
It's probably the best way for the axi...But if you don't want a tweeter (the title of the thread is clear!), I think it's better to use a horn with less energy in the medium of axis...like a constant directivity one or like an hybrid (with conical part in the profile).
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It's difficult to explain the difference between horns, but we can exagerate and oversimplify (don't be too hard with me!):
JMLC horn could look like that. Good "loading", good frequency response on axis, induced directivity.
You "feel" lot of energy and presence in the medium (delicious for voices).
Constant Directivity horn could look like that. Little less "loading", Less perfect on axis frequency response but quite good off axis, directivity better distribued.
You feel the energy more distribued.
This picture can shows the difference between JMLC profile an "optimum" (a CD without defects?)
I think that it depends on taste, on room, on listenning distance.
I personaly tend to prefer JMLC but with tweeter but I'd like to try a big "hybrid" profile.
Concerning the Axi I'm afraid that with a big JMLC horn the treble will be "shy" but that's a compromise...We can run in circle but that will be always a compromise...and a matter of taste
JMLC horn could look like that. Good "loading", good frequency response on axis, induced directivity.
You "feel" lot of energy and presence in the medium (delicious for voices).
Constant Directivity horn could look like that. Little less "loading", Less perfect on axis frequency response but quite good off axis, directivity better distribued.
You feel the energy more distribued.
This picture can shows the difference between JMLC profile an "optimum" (a CD without defects?)
I think that it depends on taste, on room, on listenning distance.
I personaly tend to prefer JMLC but with tweeter but I'd like to try a big "hybrid" profile.
Concerning the Axi I'm afraid that with a big JMLC horn the treble will be "shy" but that's a compromise...We can run in circle but that will be always a compromise...and a matter of taste
AXi2050 ain't scared of the 1000hz jmlc either lol!...
...According to my completely skeptical calculations, God knows what I'm doing wrong....
If anyone sees some inputs that I could change to make this simulation more realistic please chime in...Its basically a diaphragm with a horn on top of it...I just made up the mmd and rear chamber size, it would be nice if I could get the top end response to appear more realistic to the Axi2050, I wouldn't know where to begin.
It appears, that the Axi can run to 300hz with only a waveguide, more or less...I'm guessing that 1mm of excursion is more than other compression drivers, considering the depth of performance, with a diaphragm that has less surface area than a 4" diaphragm or am I mistaken on my assumption the surface area of a 4" diaphragm.
Can anyone confirm the sd of a popular 4" compression driver diaphragm? how about the xmax?
