LX 300b Cross-over

[bert58]

Hi guys:

Back in the mid 70's I bought a JBL driver kit consisting in a pair of 077 tweeters, a pair of LE85/HL92 mid-horns and a pair of LX300b cross-overs.(N.B. not N333)
I didn't have the money then to purchase the matching 136a woofers, but years later I bought a pair of 2235h woofers to complete my home made equivalent L300 Summits. I now know that the 136a pro equivalent was the 2231a. I also know that many 136a have been reconed as 2235h. The 2235h is apparently still one of the best woofers ever made. I'm sure that there must be a mismatch either because of the 2235h or the lx300b cross-overs because I'm sure I'm not getting the sound that I should. I use to use a 100wpc Toshiba receiver from the 70's and had to turn up the bass control to +2 or +3 to get proper bass. Deep, low bass was always impressive but bass in general kind of thin. With controls on the receiver in flat position the sound was just not very satisfying. I've recently gone to audiophile equipment and I'm now using a Bryston 11b pre-amp and a Mc Cormack amplifier. The overall sound is much cleaner but again I'm lacking bass and the mids and highs were so bright I've had to turn down the mid and high frequency speaker level controls to less than flat or 12 o'clock. Mids come screaming out. The sound at low listening levels is just too thin and lacking in bass since I no longer have a loudness switch nor bass and treble controls. It does get sort of better a higher listening volumes but I constantly get complaints from my wife to turn it down!!
My questions are as follows...
1. Has anyone out there ever experience the same problems I'm having?
2. Has anyone ever heard of the LX300b cross-over? Is it identical to the N333? If so, does anyone have a schematic for it?
3. When going from a 136a/2231a to a 2235h must cross-over mods be made, if so to what?
4. Has anyone out there built a cross-over, either passive or electronic using the components I have. If so can a schematic and list of materials be found somewhere?
5. Would it be just better to find a pair of 136a/2231a to replace my 2235h?
6. Are there plans to build replica L300 cabinets somewhere?

[Rolf]

Hi bert58, and welcome to the forum.


Hi guys:
Back in the mid 70's I bought a JBL driver kit consisting in a pair of 077 tweeters, a pair of LE85/HL92 mid-horns and a pair of LX300b cross-overs.(N.B. not N333)


I am not familiar with the LX300b network, but since you are using this x-over to make a L300 clone I guess they have the same x-overs as the N333 and the 3133, that is 800Hz and 8500Hz. The difference between the N333 and the 3133 is that you can not bi-amp with the N333.



I didn't have the money then to purchase the matching 136a woofers, but years later I bought a pair of 2235h woofers to complete my home made equivalent L300 Summits. I now know that the 136a pro equivalent was the 2231a. I also know that many 136a have been reconed as 2235h. The 2235h is apparently still one of the best woofers ever made.


You are right in this, the 2235H is superior to the 2231A,2231H,136A and the 136H.



I'm sure that there must be a mismatch either because of the 2235h or the lx300b cross-overs because I'm sure I'm not getting the sound that I should. I use to use a 100wpc Toshiba receiver from the 70's and had to turn up the bass control to +2 or +3 to get proper bass. Deep, low bass was always impressive but bass in general kind of thin. With controls on the receiver in flat position the sound was just not very satisfying. I've recently gone to audiophile equipment and I'm now using a Bryston 11b pre-amp and a Mc Cormack amplifier. The overall sound is much cleaner but again I'm lacking bass and the mids and highs were so bright I've had to turn down the mid and high frequency speaker level controls to less than flat or 12 o'clock. Mids come screaming out.


There should not be any mismatch between the 2235H and the LE85 (2420) and the 077 (2405). Using your old Thosiba will of course not give you what you want. The Bryston and Mc Cormack I am not familiar with, but the speakers needs quite a lot of power to do their best.

In my setup with the 4343B's the mid control is -2 (LE85/2420) and the hi control is -1 (077/2405). I seem to remember it was about the same when I used the 4333A's, but it also depends on your room.



The sound at low listening levels is just too thin and lacking in bass since I no longer have a loudness switch nor bass and treble controls. It does get sort of better a higher listening volumes but I constantly get complaints from my wife to turn it down!!


There should no use for a loudness button. A hi quality amp should do the work, and those amps normally lack the feature of both loudness and tone controls. Many of the members here use a equalizer on there systems, but I don't. (Don't need it).



My questions are as follows...
1. Has anyone out there ever experience the same problems I'm having?
2. Has anyone ever heard of the LX300b cross-over? Is it identical to the N333? If so, does anyone have a schematic for it?
3. When going from a 136a/2231a to a 2235h must cross-over mods be made, if so to what?
4. Has anyone out there built a cross-over, either passive or electronic using the components I have. If so can a schematic and list of materials be found somewhere?
5. Would it be just better to find a pair of 136a/2231a to replace my 2235h?
6. Are there plans to build replica L300 cabinets somewhere?

I leave these questions the the more skilled than me, but I do not believe the speaker components are the trouble. It might be the network, but do not forget what the room can do with the sound.

Good luck.

[speakerdave]

I've tried the 2235H in my 4333A and though the improvement in bass was evident, it was also evident there was something wrong with the midrange. On looking at the available frequency response curves of the two woofers there is apparently a stronger rise in the crossover region and just above in the response of the 2235. I think this would require an adjustment in the crossover/filter, but since I am not able to do that, I just went back to my 2231A's (the pro equivalent of the 136A).

David