Zonker92
All shiny and chrome
Last week I made an essentially free, reversible, and fairly easy modification to my 4430s that dramatically improved their sound.
As a preface, I would say that if you've read many of my postings here, you may know that I'm pretty skeptical about the audible benefits of some changes involving things like cables, caps, coils, etc. I may believe that a change makes an improvement, but I'm also quick to doubt my own ability reliably to perceive the improvement, as compared to wanting to believe I hear a change.
With this modification, though, there is no question in my mind that I have achieved a dramatic sonic improvement, as I will explain below.
So what is it? It's getting rid of the rotary switch in the N3134 factory passive crossover and direct-wiring the inputs. It's very easy to do.
The back of the 4430 has high level and low-level inputs, with a rotary switch to select between using an external crossover and the internal crossover. Here is the factory schematic. As you can see, turning switch does not bypass the internal crossover all the way. Instead, it breaks the LF and HF inputs apart and changes the internal crossover circuit to work with an OEM JBL external network.
And here's how it looks from the factory, with the switch in the middle:
So what does that mean? It means that you cannot directly, passively biamp (or biwire for that matter) the 4430 using the factory switch and configuration, unless you're using the JBL external network. That's not a big deal, because the internal network is excellent. However, it does prevent you from using separate amps for the LF and HF, and it does require you to use the rotary switch.
I wanted to bypass that switch AND enable passive biamping, and I found that by removing the woofer, I could remove the crossover simply by unscrewing six screws that held it to the back panel of the cabinet. The wires all unplug, and on my speakers, here is the wiring color code that I wrote up:
I figured out how to hard-wire the switching points thusly, and reassign (break out separately) the HF input (E3), so as to "lock in" the internal network while separating the LF and HF inputs from each other:
To do this, I just unscrewed the printed circuit board, unscrewed the nut holding the switch to the back panel, gently unplugged all the wires (none is soldered to the board), then unsoldered the switch. Then I installed three jumpers (using gold-plated wires left over from some film cap leads) and moved the E3 (HF) input to one of the switching points:
I put it all back together and plugged the hole using a black plastic (3/8"?) plug from the hardware store.
The result? I found a massive increase in lower bass response. Previously, the lower octave was present but not particularly strong. Now it's up several decibels (to my ears) and it will actually cause objects in the room to vibrate audibly, and the walls to creak, under high volume. This never happened before, at any output levels. My subwoofer has gone from being my major source of lower bass, to being merely a supplement from 20-35 Hz or so.
Why the difference? The only thing that occurs to me, is that there was a lot of oxidation in the crappy OEM rotary switch. I examined it and found that while it looked pretty good overall, the blades were oxidized and must have been choking off a lot of current.
Sure, I could have just cleaned it (although some of the blades are extremely hard to reach in a tiny gap above the board), but now I don't have to worry about it oxidizing again, and I can passively biamp the speakers if I so desire. (Right now I have the speaker cables connected to both sets of inputs.) If you don't want to break out the inputs, then you can just put a jumper in the final position on my diagram, and omit reassigning E3.
Now, if anything, the bass is a bit much, whereas before it was too little. But I understand that from the factory, the cabinet is tuned to around 32 Hz (or is it 34?), and along the lines of what Zilch once suggested, I plan to re-tune it to around 29 Hz for a smoother bass response. I also plan to raise the cabinets on stands maybe 4-6 inches to get the woofers away from the floor and have them behave more like the OEM soffit-mounting that the engineers intended for the speakers. (That is a mod suggested on the LH forum by JBL experts.)
But, I can assert with confidence, this inexpensive mod made a huge difference with the speakers.
(I have not looked at the 4435 schematic, but I'm sure there's a very similar mod to be done there, too.)
As a preface, I would say that if you've read many of my postings here, you may know that I'm pretty skeptical about the audible benefits of some changes involving things like cables, caps, coils, etc. I may believe that a change makes an improvement, but I'm also quick to doubt my own ability reliably to perceive the improvement, as compared to wanting to believe I hear a change.
With this modification, though, there is no question in my mind that I have achieved a dramatic sonic improvement, as I will explain below.
So what is it? It's getting rid of the rotary switch in the N3134 factory passive crossover and direct-wiring the inputs. It's very easy to do.
The back of the 4430 has high level and low-level inputs, with a rotary switch to select between using an external crossover and the internal crossover. Here is the factory schematic. As you can see, turning switch does not bypass the internal crossover all the way. Instead, it breaks the LF and HF inputs apart and changes the internal crossover circuit to work with an OEM JBL external network.
And here's how it looks from the factory, with the switch in the middle:
So what does that mean? It means that you cannot directly, passively biamp (or biwire for that matter) the 4430 using the factory switch and configuration, unless you're using the JBL external network. That's not a big deal, because the internal network is excellent. However, it does prevent you from using separate amps for the LF and HF, and it does require you to use the rotary switch.
I wanted to bypass that switch AND enable passive biamping, and I found that by removing the woofer, I could remove the crossover simply by unscrewing six screws that held it to the back panel of the cabinet. The wires all unplug, and on my speakers, here is the wiring color code that I wrote up:
I figured out how to hard-wire the switching points thusly, and reassign (break out separately) the HF input (E3), so as to "lock in" the internal network while separating the LF and HF inputs from each other:
To do this, I just unscrewed the printed circuit board, unscrewed the nut holding the switch to the back panel, gently unplugged all the wires (none is soldered to the board), then unsoldered the switch. Then I installed three jumpers (using gold-plated wires left over from some film cap leads) and moved the E3 (HF) input to one of the switching points:
I put it all back together and plugged the hole using a black plastic (3/8"?) plug from the hardware store.
The result? I found a massive increase in lower bass response. Previously, the lower octave was present but not particularly strong. Now it's up several decibels (to my ears) and it will actually cause objects in the room to vibrate audibly, and the walls to creak, under high volume. This never happened before, at any output levels. My subwoofer has gone from being my major source of lower bass, to being merely a supplement from 20-35 Hz or so.
Why the difference? The only thing that occurs to me, is that there was a lot of oxidation in the crappy OEM rotary switch. I examined it and found that while it looked pretty good overall, the blades were oxidized and must have been choking off a lot of current.
Sure, I could have just cleaned it (although some of the blades are extremely hard to reach in a tiny gap above the board), but now I don't have to worry about it oxidizing again, and I can passively biamp the speakers if I so desire. (Right now I have the speaker cables connected to both sets of inputs.) If you don't want to break out the inputs, then you can just put a jumper in the final position on my diagram, and omit reassigning E3.
Now, if anything, the bass is a bit much, whereas before it was too little. But I understand that from the factory, the cabinet is tuned to around 32 Hz (or is it 34?), and along the lines of what Zilch once suggested, I plan to re-tune it to around 29 Hz for a smoother bass response. I also plan to raise the cabinets on stands maybe 4-6 inches to get the woofers away from the floor and have them behave more like the OEM soffit-mounting that the engineers intended for the speakers. (That is a mod suggested on the LH forum by JBL experts.)
But, I can assert with confidence, this inexpensive mod made a huge difference with the speakers.
(I have not looked at the 4435 schematic, but I'm sure there's a very similar mod to be done there, too.)
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