opinions & help about my JBL 4520

[retro soulman]

hello ! Here is my pair of 4520. I use K140 for lows (uncrossed ) with 2445j and 2404 (cant remember the cross points). I use a sound valves vta 70 tube amp for the system. I have read many opinions about the 2445 but i believe they got much detail in sound and they are not so harsh in sound as many say! I can find a pair of 2441 diaphragms and im wondering if they will fit and improve the already nice sound of my 2445! Also i was thinking of change the K140 with 2225 drivers... i hope with the same watts the scoop will go a little lower !

[more10]

The 2360 will go down to about 300 Hz:

http://www.jblpro.com/pub/obsolete/23606566.pdf

Full horn loading to 350 Hz

I believe that with Radian diaphragms you will be able to cut the 2360 at 350, improving voices.

The big differences parameter wise between K140 an 2225 is fs an Q. K140 has lower Q and lower fs. The 4520 wants higher fs. Horns like lower Q, at least frontloaded horns, backloaded I am not so shure. Try them and publish here what you think.

[retro soulman]

The 2360 will go down to about 300 Hz:

http://www.jblpro.com/pub/obsolete/23606566.pdf



I believe that with Radian diaphragms you will be able to cut the 2360 at 350, improving voices.

The big differences parameter wise between K140 an 2225 is fs an Q. K140 has lower Q and lower fs. The 4520 wants higher fs. Horns like lower Q, at least frontloaded horns, backloaded I am not so shure. Try them and publish here what you think.

the horns are the 2365

[more10]

Still. Useable low frequency limint is 300 Hz.

[Horn Fanatic]

hello ! Here is my pair of 4520. I use K140 for lows (uncrossed ) with 2445j and 2404 (cant remember the cross points). I use a sound valves vta 70 tube amp for the system. I have read many opinions about the 2445 but i believe they got much detail in sound and they are not so harsh in sound as many say! I can find a pair of 2441 diaphragms and im wondering if they will fit and improve the already nice sound of my 2445! Also i was thinking of change the K140 with 2225 drivers... i hope with the same watts the scoop will go a little lower !

Hi RS -

First order of business. The K140 is a bass instrument speaker, and it makes for a marginal horn loader. The 2225 also, is not a decent horn loader. I highly recommend not using either. Even though JBL offered the rear loaded horns with the 2205, with an EBP of 136 it also wasn't the best choice. With an EBP of 190 you could do quite nicely with the E130, and the 2227 would work quite well also, if you can find them.

But what ever you chose to use, you must cross your woofers over. You can either use a compression driver with a phenolic diaphragm to cross over between 300 & 500Hz, or use a metal diaphragm crossed over at 500Hz. Since you're using the Bi-Radial horn you shouldn't need a tweeter with a large format metal diaphragm unless you like the sizzle, but you'll definitely need one with the phenolic. The next thing to check is the lowest recommended cross over point for the Bi-Radial horn you're using. I'm unfamiliar with it's parameters.

The driver that rightfully belongs in the 4520 & 4530, is the 2220A or B, depending on the load impedance you desire. The 130A or B will operate in identical manner, as it shares identical T/S parameters as the 2220. Put a 140 in a C34 or a C40, and see what you get. The ultimate choice of driver would be the 150-4C, but for most mortals the cost is out of reach. The 150 was the original driver that was loaded in the Westrex and Ampex theater horns, the Paragon, the Hartsfield, and offered in the C34. As we all know, the 150 & 375 were designed for Westrex.

One parameter I have yet to see addressed on this forum other than what I have posted, is the Efficiency Bandwidth Product, fs/Qes. Richard Small saw fit to write a paper on it. The EBP for the K140 is 136.3, for the 2225J it's 129. The EBP for the 2220J & 130B is 205.5. The lower the number, the larger the chamber that is required. The chambers for the 4520 & 4530 are too small for the 140, 2205, and 2225 to acoustically operate properly. The throat area and chamber volume are ideal for the 2220, but not so for the other drivers. The 2220 works quite well in a Klipschorn also. There are folks who like to use the E145 as a horn driver, but with an EBP of 134 I wouldn't recommend that one either. I also think the fs is far too low for use in the rear loaded horns. For those who think the Paragon sounds awesome with the LE15, have never heard one with the 150-4C. The difference is like night and day. In the day, the replacement driver for the Paragon should have been the 130B or 2220B.

I read a comment here about the 4520 wanting a higher fs, and I'm curious how the author of that comment arrived at his conclusion. But he is correct with his assertion that horns operate better with drivers with low Q's, rear and front loaded, makes little difference if the horn is designed properly. It's the throat area that determines the efficiency of the system. The throat area and chamber volume are interrelated. To change one, so change the other.

The choice between the 2441 and 2445 diaphragms is simple. Do you like the sound of aluminum diaphragms, or titanium? My preference is aluminum, because to me, titanium diaphragms sound like broken glass. Radian is offering Beryllium diaphragms now, but I'm unsure if they're in production of diaphragms for other brand drivers.

I hope I have been of help,

H.F.

BTW - My dream system would consist of a pair of reproduction C55's loaded with the 2220, a pair of 2395's with Radian Beryllium drivers, and a pair of 2405's, driven by an all tube front end.

[Mostlydiy]

Beautiful setup RS!

I dont think K140 is bad for the 4520. E140 would also be a good candidate as well as the 2220/130 and 2205. The 2227 would be very interesting and probably the best if you want to play really loud. The 2225 that you are considering is not very good Im afraid. As I understand it you are looking for more output at lower frequencies. Im not sure you will get much more bottom end with any driver since that is almost exclusively horn dependent. If you are familiar with hornresp you could make a model of the 4520 and try different woofers to get a clue of the result. My experience with hornresp is that it models the actual response very good.

/Mostly

[retro soulman]

Hi RS -

First order of business. The K140 is a bass instrument speaker, and it makes for a marginal horn loader. The 2225 also, is not a decent horn loader. I highly recommend not using either. Even though JBL offered the rear loaded horns with the 2205, with an EBP of 136 it also wasn't the best choice. With an EBP of 190 you could do quite nicely with the E130, and the 2227 would work quite well also, if you can find them.

But what ever you chose to use, you must cross your woofers over. You can either use a compression driver with a phenolic diaphragm to cross over between 300 & 500Hz, or use a metal diaphragm crossed over at 500Hz. Since you're using the Bi-Radial horn you shouldn't need a tweeter with a large format metal diaphragm unless you like the sizzle, but you'll definitely need one with the phenolic. The next thing to check is the lowest recommended cross over point for the Bi-Radial horn you're using. I'm unfamiliar with it's parameters.

The driver that rightfully belongs in the 4520 & 4530, is the 2220A or B, depending on the load impedance you desire. The 130A or B will operate in identical manner, as it shares identical T/S parameters as the 2220. Put a 140 in a C34 or a C40, and see what you get. The ultimate choice of driver would be the 150-4C, but for most mortals the cost is out of reach. The 150 was the original driver that was loaded in the Westrex and Ampex theater horns, the Paragon, the Hartsfield, and offered in the C34. As we all know, the 150 & 375 were designed for Westrex.

One parameter I have yet to see addressed on this forum other than what I have posted, is the Efficiency Bandwidth Product, fs/Qes. Richard Small saw fit to write a paper on it. The EBP for the K140 is 136.3, for the 2225J it's 129. The EBP for the 2220J & 130B is 205.5. The lower the number, the larger the chamber that is required. The chambers for the 4520 & 4530 are too small for the 140, 2205, and 2225 to acoustically operate properly. The throat area and chamber volume are ideal for the 2220, but not so for the other drivers. The 2220 works quite well in a Klipschorn also. There are folks who like to use the E145 as a horn driver, but with an EBP of 134 I wouldn't recommend that one either. I also think the fs is far too low for use in the rear loaded horns. For those who think the Paragon sounds awesome with the LE15, have never heard one with the 150-4C. The difference is like night and day. In the day, the replacement driver for the Paragon should have been the 130B or 2220B.

I read a comment here about the 4520 wanting a higher fs, and I'm curious how the author of that comment arrived at his conclusion. But he is correct with his assertion that horns operate better with drivers with low Q's, rear and front loaded, makes little difference if the horn is designed properly. It's the throat area that determines the efficiency of the system. The throat area and chamber volume are interrelated. To change one, so change the other.

The choice between the 2441 and 2445 diaphragms is simple. Do you like the sound of aluminum diaphragms, or titanium? My preference is aluminum, because to me, titanium diaphragms sound like broken glass. Radian is offering Beryllium diaphragms now, but I'm unsure if they're in production of diaphragms for other brand drivers.

I hope I have been of help,

H.F.

BTW - My dream system would consist of a pair of reproduction C55's loaded with the 2220, a pair of 2395's with Radian Beryllium drivers, and a pair of 2405's, driven by an all tube front end.

thank u for your help! but ... here in Greece the 2220 is more rare than a ferrari dino so i want to play with what i can find! So i can only find (from vintage drivers) the 2225. 2225 vs K140? ... Also my other question is : the jbl 2441 diaphragm fits as is in the 2445 driver?

[more10]

I read a comment here about the 4520 wanting a higher fs, and I'm curious how the author of that comment arrived at his conclusion.

A driver will generate output down to its fs. If the fs of the driver is lower than the horns cutoff frequency, signals between these frequencies will move the diaphragm. This is of no importance if you use an active filter with highpass at the horn cutoff.

2441 diaphragms will fit the 2445.

[more10]

http://www.jblpro.com/pub/obsolete/L...nclosures2.pdf

Model 4520 Dual Driver Horn
Thirteen-foot folded horn provides maximum loading to 42 Hz,
usable response to 30 Hz

The fs should be above 30 Hz.

The K140 has an fs of 30, keep them.

[more10]

Radian is offering Beryllium diaphragms now, but I'm unsure if they're in production of diaphragms for other brand drivers.

Actually it is Truextent. And they will fit JBL 4" VC drivers. The 1,75" VC diaphragms fit only Radian drivers.

[martin2395]

I wouldn't bother with D16R2441 diaphragms when you have Radian 1245-16's available for 1/3th of the price! I paid around €119 each for my Radians at Thomann.

A couple of days ago someone listed 4 4520's and 4530's for sale in Belgium, if I only had enough room for them!

[retro soulman]

I wouldn't bother with D16R2441 diaphragms when you have Radian 1245-16's available for 1/3th of the price! I paid around €119 each for my Radians at Thomann.

A couple of days ago someone listed 4 4520's and 4530's for sale in Belgium, if I only had enough room for them!

i found a pair of original NOS 2441 diaphragms here in Greece for 200euros.

[more10]

That is a good price. Sell the titanium diaphragms on ebay and get Radians as well.

[Horn Fanatic]

A driver will generate output down to its fs. If the fs of the driver is lower than the horns cutoff frequency, signals between these frequencies will move the diaphragm. This is of no importance if you use an active filter with highpass at the horn cutoff.

2441 diaphragms will fit the 2445.

Since it is good practice to design the fc lower than the fs, I have a set of equations I use in my program which gives me a symmetrical phase angle between the acoustical resistance and reactance of the throat, in conjunction with equations for the chamber volume which calculate proper reactance annulling between the throat and chamber. I have a built in redundancy with some of these equations for a cross check to see if my calculations are correct, and I have found errors in manufacturer data using my program. Needless to say, the procedure is quite complicated. Typically, the fc is within five to seven cycles lower than fs.

H.F.

[more10]

Retro soulman, if you take the time to make a physical model of the 4520, I will make an Akabak (or Hornresp) model of the horn. Using this model different drivers can be compared (in theory).

The physical model is a table of distance/area. The tricky parts are the bends. The length of the bend is calculated from entrance area, exit area and the volume of the bend.

Mårten