Eliptrac 240

[Guest David H]

Dave.. ah Dave....what are you up to Dave? Will we soon have a K-402 sized eliptrac?

I think we could shoe horn this Eliptrac 240 into your KHorns.

Might go nice with those BMS Drivers.

Dave

Edited December 19, 2013 by GotHover

[babadono]

Hmmm....great minds think alike.

Eric

[Guest David H]

Hmmm....great minds think alike.

Eric

[ClaudeJ1]

Dave.. ah Dave....what are you up to Dave? Will we soon have a K-402 sized eliptrac?

I think we could shoe horn this Eliptrac 240 into your KHorns.

Might go nice with those BMS Drivers.

Dave

If you look at John Warren's "Super Khorns" you will note that he crosses at 300 Hz. into a rare Altec horn. I'm currently crossing my K-402 at 320 Hz. and it sounds fantastic. So I believe your new horn to be the cat's meow as a Khorn upgrade because Khorns bottoms get pretty funky between 300-400 Hz, so it they can be bypassed by your horn, that would be a great thing. I think you are going the right direction here based on intuition and experience.

[Guest David H]

Dave.. ah Dave....what are you up to Dave? Will we soon have a K-402 sized eliptrac?

I think we could shoe horn this Eliptrac 240 into your KHorns.

Might go nice with those BMS Drivers.

Dave

If you look at John Warren's "Super Khorns" you will note that he crosses at 300 Hz. into a rare Altec horn. I'm currently crossing my K-402 at 320 Hz. and it sounds fantastic. So I believe your new horn to be the cat's meow as a Khorn upgrade because Khorns bottoms get pretty funky between 300-400 Hz, so it they can be bypassed by your horn, that would be a great thing. I think you are going the right direction here based on intuition and experience.

Thanks for the comments.

BTW, I talked to ALK about crossing the Khorn lower. He advised me that he develoved an ES 300 network specifically for this type of application.

Dave

[greg928gts]

The mid horn would need to be Fc200 to be crossed over at 300Hz, and of course the driver would need to be able to handle being crossed that low.

Greg

[Guest David H]

The mid horn would need to be Fc200 to be crossed over at 300Hz

True, Half an octave above the horns Fc is the typical rule of thumb for the crossover cutoff, However the Exteme slope networks offers signifiantly more protection than the typical 1st and 2nd order filters typically found in Klipsch speakers.

For instance a 400hz 2nd order network only offers 12db rejection at 200 hz.

ALK's ES-300 network crossed at 300hz ( thats half an octave lower than the 2nd order example) offers vastly more protection (25db) rejection at 200hz.

The half octave rule of thumb can basically be thrown out the window when using ES Networks.

and of course the driver would need to be able to handle being crossed that low.

No argument there, though I believe there are a few drivers available capable of such performance.

Dave

Edited December 21, 2013 by GotHover

[greg928gts]

I believe the half-octave rule has more to do with the horn's ability to accurately and adequately reproduce frequencies a half-octave above Fc, and not so much to do with protection of the driver. I notice my Fc260 horns really start to poop out at 400Hz and are not much good at all below 350Hz; which has nothing to do with the driver. It's simply the size of the horn mouth and length of horn. Larger horns (lower Fc) that I've tested, are more capable of getting down to 350Hz and lower with the same BMS driver.

I'd love to know what other 2" compression drivers can get down to 300Hz, it would be nice to have another option or two.

The Elliptrac 240's really look great!

Greg

[Guest David H]

I'd love to know what other 2" compression drivers can get down to 300Hz, it would be nice to have another option or two.

I looked into this a bit last night, seems the BMS 4592 says it goes to 300hz, yet the graphs and independent testing shows it capability is limited to around 350-400hz.

The DCM-50 (designed for a 400hz crossover) has very little to offer below 400hz, though successful tests were done down to 350 hz (performs better a reccomended 400hz).

The JBL 2482 (no longer in production) was the only driver I could find that performs down to 300hz.

That being said, I retract the previous statement about there being a few drivers capable of performing to 300hz. (compression drivers that is)

The Elliptrac 240's really look great!

Thanks Greg, it was quite a project.

Dave

Edited December 21, 2013 by GotHover

[Guest David H]

I believe the half-octave rule has more to do with the horn's ability to accurately and adequately reproduce frequencies a half-octave above Fc, and not so much to do with protection of the driver.

I believe the main purpose of the half octave rule is to keep the crossover point high enough to keep the driver from unloading.

I have no desire however to debate this, it is just my understanding. Either way, It really doesnt matter, its a good rule to follow.

Dave

Edited December 21, 2013 by GotHover

[greg928gts]

I believe the half-octave rule has more to do with the horn's ability to accurately and adequately reproduce frequencies a half-octave above Fc, and not so much to do with protection of the driver.

I believe the main purpose of the half octave rule is to keep the crossover point high enough to keep the driver from unloading.

I have no desire however to debate this, it is just my understanding. Either way, It really doesnt matter, its a good rule to follow.

Dave

That makes sense, whether using a first order or ES, unloading can be an issue if enough power is going to the drivers. I was thinking of it more from a listening perspective, which is something I tend to focus on a little too much sometimes.

I have a pair of Bentwood horns that I bought years ago and never used. Not sure what the Fc is, but they are very big - maybe three times the size of my Fc260 horns. I'm pretty sure Andrew had the 2482 in mind with those horns. I was able to get the BMS 4592's to test better in the 300Hz - 400Hz range than with my Fc260 horns. I could get the FR curve to react with larger caps, which is something that doesn't happen with the Fc260's. This is what leads me to believe I was experiencing the limit with the horn and not the driver at around 400Hz.

No debate, just talkin.

Greg

[jwc]

This baby does the job nicely...

http://www.jblpro.com/pub/obsolete/2482.pdf

These come up more rarely....never heard em...

http://www.jblpro.com/pub/obsolete/2485.pdf

I just noticed Jamminjersey has a pair of the 2482's.

http://jamminjersey.com/speakers.php?prod=jblcomp

[seti]

This baby does the job nicely...

http://www.jblpro.com/pub/obsolete/2482.pdf

These come up more rarely....never heard em...

http://www.jblpro.com/pub/obsolete/2485.pdf

I just noticed Jamminjersey has a pair of the 2482's.

http://jamminjersey.com/speakers.php?prod=jblcomp

Don't post this until I get mine............ lol

[Fjd]

I believe the main purpose of the half octave rule is to keep the crossover point high enough to keep the driver from unloading.

I agree with this statement and I have used compression drivers close to the cut-off point of a tractrix horn with Al's ESN cross-over networks and my low power SET amps.

If a horn is constructed to the minimum dimensions, then I believe that a steep sloped high pass filter should be used, as mentioned in this thread, to protect the compression driver as it becomes unloaded and we don't really want it to operate in this unloaded region (in my set up the ESN's pretty much reduce, to negligible, any signal to the compression driver by the time the cut-off of the horn is reached).

The interesting thing I find is that in modeling (i.e. hornsrep) of the tractrix horns I’ve noticed that acoustic output tends to be low for about an octave above the flare rate or low end cut-off of the horn, but I’m not sure how to test if the driver is actually operating in an “unloaded” state in this range?

In addition, for home HiFi use, as long as a compression driver is operating above the horn cut-off and negligible signal is reaching the compression driver at the horn cut-off frequency (the compression driver being used at its fundamental resonance by considering the impedance curve for the driver mounted in a plane-wave tube), I’m curious how much of an actual problem this first octave is given how much we pad these high efficiency horn and driver combinations down to match the bass efficiency.

When thinking about a compression driver operating in the “unloaded” range, think about the similarities and differences with a direct radiating driver in an Altec 816a cabinet or the djk ported La Scala. The 816a is a combination front-loaded horn-bass reflex enclosure. The front-loaded horn portion loads the bass driver down to about 200 Hz, while the bass reflex porting extends the useful response to about 50 Hz. The djk ported La Scala is a similar concept where the horn loading is useful to a certain response level and the porting extends the useful low frequency response.

As described above, we see variouis examples of a driver operating loaded in a horn and simultaneously operating as a direct radiating driver. However, in general, direct radiating drivers do not have phase plugs and low excursion diaphragms to contend with. Although, I suspect that the proximity of the phase plug causes displacement limitations on diaphragm movement long before its suspension limits are met.

When thinking about how the 816a functions or the La Scala modification, it would seem that a diaphragm in a compression driver should load down to the point where the horn ceases to work (I’m not sure why this would not be a function of the mouth freq/size of horn). In theory, if a diaphragm is operating in the horn loading range, that will tend to keep the diaphragm in check.

Essentially, eliminating input below the lowest useful horn frequency and above the point where the compression driver operates in an unloaded state would both seem to be important because when the diaphragm becomes unloaded, it has nothing but the “surround” or suspension to control it. I suspect this may be one reason that we see high slope cross-overs and conservative compression driver cross-over designations in sound reinforcement and PA use. This may be a reason why many of the diaphragms are controlled by how “stiff” the suspension/surround is created. When using a material such as aluminum, the diaphragm only has so much movement, and then it starts to get non-linear near the maximum. Diaphragms with a phenolic suspension should have greater “xmax” type of movement.

I’ve read where the WE555 compression driver with its aluminum diaphragm was used to 100hz. It seems like some type of ‘shim’ or spacer between the diaphragm mounting ring and the body of a compression driver would provide a bit of extra “Xmax” or distance for the diaphragm to travel before hitting the phase plug. A person could probably modify the back volume if needed. While this may help prevent the diaphragm crashing into the phase plug, I suspect is would “cost” (as there is no free lunch) some very high frequency range of the compression driver.

Edited December 22, 2013 by Fjd

[BEC]

I think a Selenium D405 should do all right at 300hz on the right horn.

[Guest David H]

Hi Bob, I forgot all about that driver.

I do remember doing some testing on the D405 phenolic, I will have to see if I can find those plots.

Dave

[seti]

Doesn't selenium make drivers for JBL?

[BEC]

Doesn't selenium make drivers for JBL?

JBL (actually parent company Harmon) bought Selenium a few years ago. I don't know if any production sharing is going on.

Edited December 22, 2013 by BEC

[Guest David H]

I took a look at the plots on the D-405 phenolic, it looks about like the rest -10 to -15db at 300hz.

I did not do any distortion testing on these.

Fortunately there is not a real big need to crossover at 300hz anyway, and if there is there are still a few JBL 2482's around.

Dave

[Guest David H]

JBL (actually parent company Harmon) bought Selenium a few years ago.

Yes, and that's about the time Selenium's prices went up.

I see a lot of Craig's List sellers trying to pawn off Selenium drivers as JBL's

Dave