Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Craig Hamilton]

Thanks! This is awesome!

If you were to wire it like this, the L1 and C1/C2 combo would totally short out the tweeter as they need the speaker load to work correctly. The correct schematic lifts the C1/C2 connection and bypasses L1.

As I stated before, just wire it like JBL did. The SR4722a is different because of the factory Speakon but operates exactly the same in the end. Normal convention is LF and Full range as the same input.

[Steve M Smith]

One question I have is whether L1 serves any function in biamp mode with respect to the woofer.

In my equivalent circuit, L1 and C1/C2 are still connected across the HF input.  Personally, I don't think it will make much difference as you are only feeding it higher frequencies and they are directly across the amplifier output, not the HF driver.  However, if you are worried about it, you could source a three pole switch and arrange it to disconnect it when switched to biamp mode.


If you can't find a three pole switch and don't intend to drive the speakers with bridge configured amplifiers, leave the negative side of the LF driver connected, isolating just the positive side and use the second pole to isolate L1 and C1/C2.

Normal convention is LF and Full range as the same input.

Yes.  If you are using all four connections of an NL4 Speakon, it makes sense to arrange it as +1/-1 to be full range or LF and +2/-2 to be HF in biamp mode.


Steve.

[Steve M Smith]

Re-arranging so it conforms to LF/Full Range on +1/-1 as Craig suggests, I get this.  It needs a 3 pole changeover switch.  Note I have used the 4722A HF circuit but it will work with the 4722 as well.




Steve.

[Peter Johnson 793]

Re-arranging so it conforms to LF/Full Range on +1/-1 as Craig suggests, I get this.  It needs a 3 pole changeover switch.  Note I have used the 4722A HF circuit but it will work with the 4722 as well.




Steve.

Spent some time with this over the weekend. 


Thanks guys, in terms of accessing solder points, minimizing soldering and utilizing traces in the PCB I think Steve's first diagram is easiest to use, with a mod based on Craig's observation.

I will hard wire points 6 and 7 together on the imprint for the LF BI Amp switch then put an on off switch on the green black wire after the feed wire for the Tweeter and before C1 and C2 which  opens that circuit in  Bi amp mode and closes it in FR mode.  Hence no signal will pass thru C1, C2 or L1 when in biamp mode.

I don't mind that FR and Hi Bi amp share a jack.  I will label everything very conspicuously.  And my compression drivers are fused as a backup precaution against bumping the switch to BIamp by mistake  and inadvertently sending  FR thru the tweeters.   

It's more important to me that I minimize trying to solder a very old PCB and the risk that I might raise traces and the like.

Thanks again for your help.   

Pete

[Steve M Smith]

It doesn't really matter if Biamp/HF share the same connector.  Craig was right though about the convention when using all four contacts of an NL4 Speakon as the full range would only use the +1/-1 pair and biamp would put LF on +1/-1 and HF on +2/-2.

However, if it's only going to be you using them, you can wire them up the most convenient way with no ill effects.


Steve.

[Craig Hamilton]

Stevens schematic looks to be exactly the same as JBLs. When I modded the 4 I did, I just threw away the pub with the 4 1/4" jacks and hard wired a new 1/4" jack for full range and mounted the switch and speakon at the top where the Biamp jacks used to be. I put the new Biamp switch right next to the horn boost switch. Use the terminals on the new switch as a point to wire the incoming jacks to and out to the crossover board.

[Peter Johnson 793]

Stevens schematic looks to be exactly the same as JBLs. When I modded the 4 I did, I just threw away the pub with the 4 1/4" jacks and hard wired a new 1/4" jack for full range and mounted the switch and speakon at the top where the Biamp jacks used to be. I put the new Biamp switch right next to the horn boost switch. Use the terminals on the new switch as a point to wire the incoming jacks to and out to the crossover board.

Thanks to all -- I feel well armed - hopefully not too dangerous(!) - and ready to tackle this project.

 

[Tim McCulloch]

Thanks to all -- I feel well armed - hopefully not too dangerous(!) - and ready to tackle this project.

Cool.  Post back and let us know how things worked out.

[ProSoundWeb Community]