Bi-amping with crossovers

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Restlesstj
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Bi-amping with crossovers

Post by Restlesstj » Fri Jan 28, 2022 1:13 pm

Could someone please help me set up a stereo biamping system. I have a cs400 and cs800 both are from the 1980's. I am using a Tascam M-312 mixing board which gives me the option of sending a balance or unbalance signal to the power amp with either XLR or 1/4. My speakers are: for the subs I am using JBL E-140'S and my mids and highs are Altec lancing 1202 voice of the theater cabinets with a built-in crossover at 800hz. I have the following crossovers 1-PL-1200, 1-PL-1200E.Q. 2- PL-500, and 1-PL-150. I also have an Electro-voice EX-18 rack mount electronic crossover. I am missing the dust covers on the back of the cs800 for the crossover plug in. Could someone please tell me how to wire this up the best way to have a stereo biamp system. Thank you in advance for your help.

Bartman
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Re: Bi-amping with crossovers

Post by Bartman » Mon Jan 31, 2022 9:20 am

Since you have an electronic crossover, use that instead of the PL modules. Connect mixer outputs (L&R) to the inputs of the EX-18, connect the LO OUT jacks to the inputs of the CS800... that amp will power the subs. Connect EX-18 HI OUT jacks to the CS400 to power the 1202 speakers.
Settings on the EX-18 for both channels, set the same:
Frequency between 100-150, (probably closer to 150, but use you ears for what sounds best)
Range x1
Phase Normal
And the button in the middle set to 2 way.

Restlesstj
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Re: Bi-amping with crossovers

Post by Restlesstj » Mon Jan 31, 2022 4:09 pm

Thank you Bartman for your help. I have one more thing I hope you can help me with. On my first post I was incorrect about having XLR and 1/4 main outputs to the power amp. I just have stereo XLR output jacks there is a switch under each to switch from unbalanced to balanced. Now the EV EX-18 crossover has just a 1/4 input that says it will take balanced or unbalanced line in. My question is what kind of cable do I need to feed the crossover from the mixer. Do I need anything with a transformer? Do I feed it from the board unbalanced or balanced? Thank you again for all your help.

Bartman
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Re: Bi-amping with crossovers

Post by Bartman » Tue Feb 01, 2022 2:17 pm

It's always best to use balanced whenever you have that option, so to connect the mixer XLR outputs to the EX-18 1/4" inputs, you would need a couple F-XLR to 1/4" TRS cables, no transformers involved (see picture below). The cables would be wired Pin 1 to Sleeve (ground), Pin 2+ to Tip, and Pin 3- to Ring. HOWEVER, wiring standards were not yet "standard" back in the 80s, so there is a possibility that you might need to reverse pins 2 and 3 (to Ring and Tip, respectively). Alternatively, if polarity is Pin 3+ and Pin 2-, the standard wiring cable could still be used and then simply press the phase reverse buttons on the EX-18 to get things back into correct phase. If you're just listening as a home stereo, then this part doesn't make much difference, but it's nice to know that your speakers are moving out on a positive voltage, and in on a negative voltage.
XLRtoTRS.jpg
XLRtoTRS.jpg (14.3 KiB) Viewed 4231 times

Restlesstj
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Re: Bi-amping with crossovers

Post by Restlesstj » Tue Feb 01, 2022 7:39 pm

Bartman thank you so much for all your help. Can you tell me if there is a simple way of telling what the pin configuration on the stereo xlr outputs of the Tascam M-312 mixer will be when I flip the switch to balanced? You said back when this board was made there wasn't a "standard" wiring standard. I really don't want to screw this up and have it out of phase or anything.
Again you are the man and thank you for all your patience and help.

Bartman
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Re: Bi-amping with crossovers

Post by Bartman » Fri Feb 04, 2022 10:44 am

I would have to search the manual if it can be found, but you won't hurt anything if the pins are reverse polarity from what is standard today. If the back of the mixer doesn't have the pin configuration labeled and you don't have a manual for it, then connecting an oscilloscope to it might be the only sure-fire way of making that determination.

Restlesstj
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Re: Bi-amping with crossovers

Post by Restlesstj » Fri Feb 04, 2022 11:07 am

Thank you Bartman.
I don't have a oscilloscope so I will have to see if I can find anything online to tell me what the pin configuration is for the M-312.

Bartman
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Re: Bi-amping with crossovers

Post by Bartman » Mon Feb 07, 2022 8:42 am

If the polarity is reversed from what is standard today, you can still use the same standard cable and then push the polarity reverse buttons on the crossover to get everything back to normal polarity.

One way you might could tell if you can watch closely, tap on a microphone and see if the first movement of the subwoofer speaker cone is out. If the speaker cone moves inward first, then polarity is reversed.

Restlesstj
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Re: Bi-amping with crossovers

Post by Restlesstj » Mon Feb 07, 2022 9:03 am

Thank you for all your help Bartman you are the best!

Dookie
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Re: Bi-amping with crossovers

Post by Dookie » Tue Feb 08, 2022 4:40 am

Bartman wrote:
Mon Feb 07, 2022 8:42 am
If the polarity is reversed from what is standard today, you can still use the same standard cable and then push the polarity reverse buttons on the crossover to get everything back to normal polarity.

The older CS series amps had Pin 2 and Pin 1 connected together through a Qusi-balanced circuit. So it is "very" important to make sure Positive input is going into Pin 3 on these older amps. If a person can find the "balancing transformer cans" for the amps, then it wouldn't matter as these give true transformer balanced input so the qusi-balanced circuit is no longer strapping pin 2 to pin 1 ground together. As you say above if you have a crossover that has a polarity reverse switch you can do that. Or another easy way is to have the crossover put in the amp rack (closer than 3 feet or so away from the amps) and go unbalanced from the crossover into the amps. Hopefully the crossover has unbalanced 1/4 inch outputs. This will put Tip to Pin 3 inside the amp and the sleeve will be going to pin 1.

Doug

Bartman
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Re: Bi-amping with crossovers

Post by Bartman » Tue Feb 08, 2022 8:58 am

From the pictures I looked up online for this crossover, they do appear to be unbalanced 1/4" output jacks (but the inputs are labeled as balanced). So, yes, from the crossover to amp, just use a plain "guitar cord" patch cable.

Restlesstj
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Re: Bi-amping with crossovers

Post by Restlesstj » Thu Feb 10, 2022 5:25 pm

Mr. Bartman can you tell me are the jumpers or dust covers that are in the back of the cs800 the exact same ones in the transformer input and the crossover input or are they specific to each input and will the cs800 work correctly if the jumpers for the crossover inputs are missing? Wiring it up the way you told me to do with the EV EX-18.
Thank you again for all your help.

Bartman
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Re: Bi-amping with crossovers

Post by Bartman » Fri Feb 11, 2022 9:23 am

I'm not aware of any "jumpers", but dust covers are just that... covers, that do nothing but cover the sockets. The two sockets do different things though, and cannot use a PL crossover in the Balancing Transformer socket, nor vice versa. With noting inserted in these sockets, the amp will work fine with just the regular plain 1/4" TS (Tip-Sleeve) "guitar cord" patch cable coming from the crossover's output.

Restlesstj
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Re: Bi-amping with crossovers

Post by Restlesstj » Fri Feb 11, 2022 10:04 am

Perfect thank you, thank you,thank you.

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