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Author Topic: Crossover, L-Pad, Impedence, Resistance question  (Read 10160 times)

Paul G. OBrien

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Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #70 on: November 23, 2017, 12:27:44 am »

No, as pictured, the input to the crossover is switched out.  It shown in Biamp mode. 

No it isn't!!!!!!

Here is what Bi-amp mode looks like.
« Last Edit: November 23, 2017, 12:41:22 am by Paul G. OBrien »
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Jeff Schoonover1

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Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #71 on: November 23, 2017, 09:12:41 am »

No it isn't!!!!!!
Okay, now I see where the miscommunication lies. 
Ivan Beaver and Paul G. Obrien are referring to Paul G. Obrien's drawing in post 17 (re-posted in post 70). 
I have always been referring to MY drawing in post 24.

I see what Paul did in post 17.  and what both Ivan and Paul are saying.  In post 18 though, several of us began the conversation regarding the positive leads to/from the X-Over.  This led to my drawing and the beginning of all this confusion.
I get Paul's drawing now.  I can use just one 4-pole Speakon and it will work.  I also see where I went wrong with the common connections.  There is no need to lift the common in Biamp mode, as I did with mine.
Sorry for all the confusion.
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Paul G. OBrien

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Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #72 on: November 23, 2017, 11:03:39 am »

Okay, now I see where the miscommunication lies. 
Ivan Beaver and Paul G. Obrien are referring to Paul G. Obrien's drawing in post 17 (re-posted in post 70). 
I have always been referring to MY drawing in post 24.

OH sorry if I was mistaken on that. Your schematic has a couple issues including the fact that the crossover inputs need to be on 1+/1- of the speakon. This allows one to use use a standard straight through 4 core speakon cable for both modes.. which is always a good idea. If you want to use a bridged amp when in fullrange mode that is fine but you need to make the wiring adjustment at the amplifier end and ideally with a patch panel in the amp rack if your amp doesn't have a dedicated bridged output connector.
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Jeff Schoonover1

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Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #73 on: November 23, 2017, 12:11:20 pm »

OH sorry if I was mistaken on that. Your schematic has a couple issues including the fact that the crossover inputs need to be on 1+/1- of the speakon. This allows one to use use a standard straight through 4 core speakon cable for both modes.. which is always a good idea. If you want to use a bridged amp when in fullrange mode that is fine but you need to make the wiring adjustment at the amplifier end and ideally with a patch panel in the amp rack if your amp doesn't have a dedicated bridged output connector.
LOL, No worries.  It's funny now :)
Yes, yes, yes, and yes!  I understand completely now.
I already have made the two cables, one for bridged, and one for 4-way, I was hoping to figure out how to use the same Speakon input with either cable and here we are, thanks! 
Patch panel - A good idea, I even have one I can use for this.
Just to be sure, here's your idea using one input.
Oh - What was the 20uF cap for in your drawing? Can I not connect 1- and 2-, run the tweeter's common back through the X-over like the woofers?  Thereby eliminating that switch as well?
« Last Edit: November 23, 2017, 12:30:21 pm by Jeff Schoonover1 »
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Ivan Beaver

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Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #74 on: November 23, 2017, 12:57:41 pm »

No it isn't!!!!!!

Here is what Bi-amp mode looks like.
I'm sorry, but the input to the xover IS disconnected.

YES, the common is hooked up to the xover-but SO WHAT?  There is no path for it to go, therefore none of the components in the crossover do anything-no matter how they are wired.

The common is hooked to the neg of the woofer and the biamp input-but it doesn't matter.

It will take a lot more convincing (which I don't see how it can be done) to convince me it would nto work.

Hooking a single wire to something does nothing, ONLY if there is a path to somewhere-which there isn't in this case
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Jeff Schoonover1

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Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #75 on: November 23, 2017, 01:19:18 pm »

I'm sorry, but the input to the xover IS disconnected.
I see what you're saying.  No matter what, this configuration will take two different cables to work.  A standard 4-conductor with 4-pole Speakons, and a special adapter cable for bridge mode with 1+ and 2+ at the Amp end (Negatives are not used for Bridge Mode) connected to 1POSITIVE and 1NEGATIVE on this diagram. 
The Speakon in the diagram isn't drawn the way a Speakon is in real life.  But it should work if connected by the diagram, not the number labels...  I'll fix the drawing tonight.
« Last Edit: November 23, 2017, 02:14:36 pm by Jeff Schoonover1 »
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Ivan Beaver

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Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #76 on: November 23, 2017, 02:51:00 pm »

I see what you're saying.  No matter what, this configuration will take two different cables to work.  A standard 4-conductor with 4-pole Speakons, and a special adapter cable for bridge mode with 1+ and 2+ at the Amp end (Negatives are not used for Bridge Mode) connected to 1POSITIVE and 1NEGATIVE on this diagram. 
The Speakon in the diagram isn't drawn the way a Speakon is in real life.  But it should work if connected by the diagram, not the number labels...  I'll fix the drawing tonight.
Whether or not the amp is bridged has nothing to do with switching the cabinet from passive to biamp.

They are not related to each other.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Paul G. OBrien

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Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #77 on: November 23, 2017, 05:22:03 pm »

I was hoping to figure out how to use the same Speakon input with either cable and here we are, thanks! 
Patch panel - A good idea, I even have one I can use for this.

Here is a way to use a patch panel and the same standard speakon cable for both modes, no special cable or adapters necessary. NL4 panel mount speakons fan out to banana plugs that can go to separate channels or be quickly moved across the red terminals for bridged operation. If your amps don't use that config for bridged then you just have to mount another connector on the patch panel wired specifically for bridged mode And all of these can stay connected to the amp all the time, you just plug into whatever one matches the speaker config in use.


Oh - What was the 20uF cap for in your drawing?
I was wondering when we were going to get to that. It's an insurance policy protecting the CD from accidents like somebody using the wrong cable or a mixup with processing where the low frequencies or a fullrange signal is sent to the CD. It is sized to filter ULF only with a corner frequency well below the active crossover so as to minimize unwanted phase shift.


Can I not connect 1- and 2-, run the tweeter's common back through the X-over like the woofers?  Thereby eliminating that switch as well?
Depends if you are always using the same 2 channel amp for biamp operation or not, if using two separate amp chassis then you may have a problem with that common neutral.
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Jeff Schoonover1

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Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #78 on: November 24, 2017, 11:09:37 am »

Ivan Beaver is correct, I believe.  The problem is that 2+ becomes negative and completes the circuit in bridge mode, and therefore has to be connected to the X-Over negative input at that time.  There will have to be a fifth switch. so that in Bi-Amp mode, 2+ can connect to tweeter +.
 
Since 2+ becomes negative, 1- negative may also need to be lifted in bridge mode, or it may short Channel 1's contribution to the bridge back through channel 1(?)  I don't know whether or not 1- and 2- are lifted at the amp when in bridge mode.

I think my original drawing stands, more or less.  Here's an update.



« Last Edit: November 24, 2017, 11:47:34 am by Jeff Schoonover1 »
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Jeff Schoonover1

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Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #79 on: November 24, 2017, 11:30:42 am »

Here is a way to use a patch panel and the same standard speakon cable for both modes, no special cable or adapters necessary.
I have a panel with one speakon mounted that will work just for this.  Like yours (I think, the pic is blurry),  my amp also has channel 1 as a 4-pole, able to output both channels independently, and can also be used for bridge mode with just the positive poles.  I can just use the Channel 1 output and put a piece of tape over Channel 2.  I love the idea of one cable, one connection, no matter what.  I understand the added safety value of what you suggest, as best practice.  Although I'm sure that when cycling through modes, my amp won't engage the circuit if it's shorted.  Not that I've EVER tried this accidentally ;) 
I was wondering when we were going to get to that. It's an insurance policy protecting the CD from accidents like somebody using the wrong cable or a mixup with processing where the low frequencies or a fullrange signal is sent to the CD. It is sized to filter ULF only with a corner frequency well below the active crossover so as to minimize unwanted phase shift.
I figured it was a filter, I didn't think of it for safety.  My tweeter is 16ohms, So something closer to 10uF for a ~1KHz roll-off might be better. 
Depends if you are always using the same 2 channel amp for bi-amp operation or not, if using two separate amp chassis then you may have a problem with that common neutral.
Actually, looking at it, tweeter common to the X-Over can't be done. 2+ becomes negative in bridge mode, so 2- has to be lifted, or it shorts to 2+.
 2- has to have it's own switched route to the tweeter, as it's the only route Channel 2 can complete its circuit in bi-amp mode.  This is what Ivan Beaver was talking about.
« Last Edit: November 24, 2017, 11:37:13 am by Jeff Schoonover1 »
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ProSoundWeb Community

Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #79 on: November 24, 2017, 11:30:42 am »


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