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GK Biamp Cabinet Wiring

J

JohnLochner

Feb 27, 2009
5
0
#1
Hello,
Long time reader, first time poster here. I have a quick question on the wiring of a GK cab.

When you use the Speakon input of a GK cab, and set the 'mode' switch to 'biamp', does this simply send Speakon pins 1+/1- to the woofer, and 2+/2- to the tweeter? In other words, is there anything else going on inside a GK cab besides a direct connection to the drivers (when using Speakon input set to 'biamp' mode)?

Thanks ya'll.

best,
John
 
#3
According to GK when you use a GK bi-amp head (700RB), the Biamp mode connects the 1+/1- to the woofer and the 2+/2- to the tweeter. With any other amplifier, mono or bridged, you should use the cab on the full range mode. which means that 1+/1- connect to the woofer and the tweeter in one circuit.
 
#4
That's right. Also, if you have a normal two wire speakon lead wired 1+/1- and whatever amp, if the switch is on bi-amp the tweeter is disconnected because when the switch is in bi-amp the tweeter is not connected to the crossover and instead is connected to 2+/2- on the cabinet's speakon socket.

Therefore, if you don't want to use the horn at all, you can protect the tweeter by using a normal 1+/1- speakon lead with the switch set to bi-amp. I do it on one of my cabs and have done with no problems for years, although if I use that cab on its own , I just use my GK speakon lead.

This post is no doubt very badly worded as it's 4am here as I type. Heh, I know what I mean! :hiding:
 
#5
Femto said:
That's right. Also, if you have a normal two wire speakon lead wired 1+/1- and whatever amp, if the switch is on bi-amp the tweeter is disconnected because when the switch is in bi-amp the tweeter is not connected to the crossover and instead is connected to 2+/2- on the cabinet's speakon socket.

Therefore, if you don't want to use the horn at all, you can protect the tweeter by using a normal 1+/1- speakon lead with the switch set to bi-amp. I do it on one of my cabs and have done with no problems for years, although if I use that cab on its own , I just use my GK speakon lead.

This post is no doubt very badly worded as it's 4am here as I type. Heh, I know what I mean! :hiding:
Click to expand...

WHAT??
Just kidding I understood you fine :D
 
#7
Heheh nice one. Thanks. :hyper:

You US guys make me laugh..in a good way though. London is bloody miiiiiles away. You think nothing of driving 2 hours for your groceries and then 2 hours back. I mean, I think it's a long way down the street to the post office. That's just peanuts to you guys. What the hell am I going on about!? Sorry...I'll get me coat.
getmecoat.gif
 
#8
Femto said:
..... when the switch is in bi-amp the tweeter is not connected to the crossover and instead is connected to 2+/2- on the cabinet's speakon socket.
Click to expand...
I think I'm missing something? There's a knob on the 800RB amps that lets you select the bi-amp frequency, and it's varialble betweek 100Hz and 1k. If you set it to 100Hz, does that mean the tweeter is getting fed frequencies down to 100Hz? Wouldn't those low frequencies damage the tweeter?
 
#9
Petebass said:
I think I'm missing something? There's a knob on the 800RB amps that lets you select the bi-amp frequency, and it's varialble betweek 100Hz and 1k. If you set it to 100Hz, does that mean the tweeter is getting fed frequencies down to 100Hz? Wouldn't those low frequencies damage the tweeter?
Click to expand...

IIRC G-K's more modern cabs which support the Horn Bi-amp System are designed to work with the 700RB or later RB series amps (which sport a fixed 5 KHz X-over, and a 50 Watts RMS max. tweeter amp which can only output frequencies above 5KHz).

In contrast, the variable X-over in the venerable 800RB (introduced in the early '80's?) was designed to drive say.., an 8 Ω min. 2 X 10" cab via the 100 Watt RMS tweeter amp, and a larger, 4 Ω min 2 X 15" cab via the 300 Watt RMS woofer amp.

I believe that the 800RB's tweeter amp can alternately be run in full range mode which allows for an 8 Ω 1 X 15" cab + a 4 Ω 2 X15" cab.

The speaker sizes aren't important as long as they can handle the amp's Wattage, and (this is important) the tweeter amp sees no less than an 8 Ω load, and the woofer amp, no less than a 4 Ω load.

A good number of 800RB tweeter amps were fried by folks plugging 4 Ω cabs into them. :eek:
 
#10
Petebass said:
I think I'm missing something? There's a knob on the 800RB amps that lets you select the bi-amp frequency, and it's varialble betweek 100Hz and 1k. If you set it to 100Hz, does that mean the tweeter is getting fed frequencies down to 100Hz? Wouldn't those low frequencies damage the tweeter?
Click to expand...
Yes, low frequencies would damage a tweeter but you're comparing two different situations.
The 800RB has nothing to do with the current G-K "HMS" (horn management system), found on the current 700RB, 1001RB, and 2001RB lines, as well as most of the current cabs. These have a dedicated 50w amp to feed the tweeters above 5K in the "bi-amp" mode.

The 800RB has an excellent (IMO) true bi-amp capability with adjustable crossover frequency, which is intended for a separate cabinet to handle mid-high frequencies. The 800RB doesn't even have Speakon outs.

I have both types and always run my 700RB II full-range, but would sometimes (late eighties) bi-amp my 800RB into a 1x15 (lows) and 2x12 (mids/highs). With today's modern cabs that have tweeters and a crossover, I find that full-range works just fine for me, regardless of which amp I use.
 
#12
I have a GK 1001RB II

My plans is to find a way to reside my crossovers in a Epifani NYC 410
Cab to take the advantage of the biamp system on the amp.
Is there any precautions I should take and in general, can it be done?
 
#13
Yes it can be done if the HF driver in the Epifani already rolls off at 5KHz. Bypass the crossover in the cab and wire it to 2+,2- on a four pole speakon. Woofers wire to 1+,1- if the crossover point is much different on the cab you may notice "holes" in the sound of the cab (towards the upper end).
 

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