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GK Legacy 1200 Have Bi-Amp Mode?

Schemaman

Schemaman

Jun 16, 2018
29
83
#1
I have a GK Legacy 1200 Head and a GK Neo 115 III cabinet. The manual for the cabinet references amps that support Bi-Amp mode and the concept makes sense to me. However, I see no reference to Bi-Amp mode in the GK Legacy 1200 manual (or in my Interwebs searching) so believe I should set my cabinet to full-range. I am wondering if I am missing something so am appealing to the wisdom of the TB crowd to see what you think. I have the 4 conductor Speakon cable so am good there if the Legacy 1200 actually does support bi-amp but for now I am not sure which way I should set full-range switch on the cabinet.

On a related note, I have been considering adding my Genz-Benz 8 ohm 12" cabinet to have 2 x 8 ohm cabinets for my amp, so am assuming I'd have to use full-range in that configuration even if the 1200 does support Bi-Amp since that would add a non-GK cabinet into the mix.

Thanks!
 
#4
For the most part it doesn’t make any sense to biamp a standard bass cabinet, as even multi-driver cabinets (like Acme or AccuGroove for instance) have them all well integrated. It would mainly make sense in a situation where you were using say, a 10” cabinet along with a 15” or 18”, in order to keep them from overlapping (and therefore doubling) the frequencies that both reproduced. The idea would be the 10” cab would (theoretically) do better at reproducing the mids and upper mids, while big cabinet would deliver the lows that the smaller cab couldn’t do as well.

Regards,
Wayne A. Pflughaupt

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#5
As mentioned, GK biamping ended with the discontinuation of the RB series.

The benefit as I see it YMMV: It nice to be able to adjust the tweeter from the front panel of the amp. Then again, it can also be a hassle.

GK's claimed benefit. Many of their amps have a boost circuit that consists of a potentiometer and a FET that is set up to emulate a pushed tube. The Boost circuit is only in the woofer's signal path. The idea is you can crank up the Boost and get a bit of tubey grind in the woofer, while keeping the distortion out of the tweeter. In general, people do not like the sound of distortion through little horn tweeters.

GK crossed the tweeter over rather high at 5kHz and the HPF is always in the circuit. The woofer signal path could be run full-range or a 5kHz LPF could be switched into the circuit. It's not a problem to fun the woofer amp into a full-range cabinet.

If you want to take advantage of the unique biamp capability you need a compatible GK cab. The RBH series cabs and series III and older Neo cabs could be run in biamp mode or full range mode. The current Neo IV cabs are full range only. You may actually see images of Neo IV cabs with the biamp feature, but per GK these were pre-production mockups.
 
#6
Thank you Wayne and Wasnex!
I have tried connecting my 8 ohm Genz-Benz 12" cabinet along with my Neo for 2 x 8 ohm speakers to the Legacy 1200 to get a bit more juice going. I think the GK cab is rated at 400 W and the Genz-Benz at 375 W so I have to be a little bit careful with how much energy they get from the amp. But I am wondering if I ought to do something like what you suggested and, using the control on the back of the cabinets, have the Genz-Benz cabinet handle higher freqs and the GK cab handle lower freqs since it's a bigger driver. Do you think that would work and be smart or would it be better to just send the full range signal to both cabs, being careful with output?
 
#7
Schemaman said:
Thank you Wayne and Wasnex!
I have tried connecting my 8 ohm Genz-Benz 12" cabinet along with my Neo for 2 x 8 ohm speakers to the Legacy 1200 to get a bit more juice going. I think the GK cab is rated at 400 W and the Genz-Benz at 375 W so I have to be a little bit careful with how much energy they get from the amp. But I am wondering if I ought to do something like what you suggested and, using the control on the back of the cabinets, have the Genz-Benz cabinet handle higher freqs and the GK cab handle lower freqs since it's a bigger driver. Do you think that would work and be smart or would it be better to just send the full range signal to both cabs, being careful with output?
Click to expand...

You will be sending a full range signal to the cabs as the Legacy 1200 has no crossover capabilities. The tweeter control on the cabs allows you to adjust the highs to taste. IMHO try it both ways.

Mixing random cabs is not generally a recipe for good sound. Dissimilar cabs are likely to have variances in phase and group delay that degrade the sound. Two identical cabs will have the same phase and group delay characteristics. I suggest you find a cab you like, and then buy as many of them as you need/want.

The Legacy 1200 has two output channels. Each channel is rated for 400W at 8 ohms, and 800W at 4 ohms. So yes, you probably have enough power to destroy both of your cabs, but it is not huge mismatch. Use a bit of discretion and self-control and you should be fine.

The amp's 1200W power rating is total power when running a 4 ohm load on each channel. If you only run one output into a 4 ohm load, the amp can make 800W. But if you run two 4 ohm loads, each output makes 600W. Also, if you run 4 ohms on one channel and 8 ohms on the other, total power is 950W.
 
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#9
Wasnex said:
You will be sending a full range signal to the cabs as the Legacy 1200 has no crossover capabilities. The tweeter control on the cabs allows you to adjust the highs to taste. IMHO try it both ways.

Mixing random cabs is not generally a recipe for good sound. Dissimilar cabs are likely to have variances in phase and group delay that degrade the sound. Two identical cabs will have the same phase and group delay characteristics. I suggest you find a cab you like, and then buy as many of them as you need/want.

The Legacy 1200 has two output channels. Each channel is rated for 400W at 8 ohms, and 800W at 4 ohms. So yes, you probably have enough power to destroy both of your cabs, but it is not huge mismatch. Use a bit of discretion and self-control and you should be fine.

The amp's 1200W power rating is total power when running a 4 ohm load on each channel. If you only run one output into a 4 ohm load, the amp can make 800W. But if you run two 4 ohm loads, each output makes 600W. Also, if you run 4 ohms on one channel and 8 ohms on the other, total power is 950W.
Click to expand...

hi really interested in this post. I have just purchased this amp and want to run three 8 ohm cabs of it ( don’t ask ). How would I do this please ?
 
#10
johnthebass said:
hi really interested in this post. I have just purchased this amp and want to run three 8 ohm cabs of it ( don’t ask ). How would I do this please ?
Click to expand...

From the Legacy OM:
upload_2022-9-11_13-24-5.png


The minimum load is 4 ohms per channel, so you can't run all three cabs on one side of the amp. Why? Three 8 ohm cabs present a 2.6 ohm load, which <4 ohms.

Notice the red brackets. You can put 4 ohms on one side of the amp and 8 ohms on the other, and the outputs are fine with the different impedances. The amp does not care about how many cabs are used, it only cares about the resulting impedance.

Two 8 ohm cabs will present a 4 ohm load. Connect this to one channel of the amp.

One 8 ohm cab will present an 8 ohm load. Connect this to the other channel.

Back of the amp:
750-Legacy1200_detail2.jpg.auto.webp


Close up on output jacks and power matrix chart:
upload_2022-9-11_13-35-9.png


Notice the bottom line. The amp is spec'ed to produce 950W with this setup.
 
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#11
Wasnex said:
From the Legacy OM:
View attachment 4811210

The minimum load is 4 ohms per channel, so you can't run all three cabs on one side of the amp. Why? Three 8 ohm cabs present a 2.6 ohm load, which <4 ohms.

Notice the red brackets. You can put 4 ohms on one side of the amp and 8 ohms on the other, and the outputs are fine with the different impedances. The amp does not care about how many cabs are used, it only cares about the resulting impedance.

Two 8 ohm cabs will present a 4 ohm load. Connect this to one channel of the amp.

One 8 ohm cab will present an 8 ohm load. Connect this to the other channel.

Back of the amp:
750-Legacy1200_detail2.jpg.auto.webp


Close up on output jacks and power matrix chart:
View attachment 4811223

Notice the bottom line. The amp is spec'ed to produce 950W with this setup.
Click to expand...
Really appreciate this advice. Can you please clarify why it has a 2 ohm selection please. I was thinking that three 8 ohm cabs could run of the 2 or ohm selection or indeed the 2.6. Not that I want to do this just wanted to clarify my understanding. I.e divide 8 ohms by 3 ( three 8 ohm cabs). gives 2.6. Thanks for you previous reply
 
#12
johnthebass said:
Really appreciate this advice. Can you please clarify why it has a 2 ohm selection please. I was thinking that three 8 ohm cabs could run of the 2 or ohm selection or indeed the 2.6. Not that I want to do this just wanted to clarify my understanding. I.e divide 8 ohms by 3 ( three 8 ohm cabs). gives 2.6. Thanks for you previous reply
Click to expand...
There isn't a 2 or 2.6 ohms option. @Wasnex provided both photos of the back of the amp and the table from the manual to illustrate that 4 ohms is the minimum.
 
#15
johnthebass said:
Thanks for your response. See quote from the description:

“
- Twist Lock Speaker Outputs
- 2, 2.7, 4 and 8ohm Load Capacity
- Dimensions - 11.5” Width x 11” Depth x 2 3/8” Height“.
Click to expand...

The manual is generic to three different models: Legacy 500, Legacy 800, and Legacy 1200. The 500 and 800 can be used down to 2 ohms.

There are snips from the manual.
upload_2022-9-12_12-57-24.png



Notice the note says "500 and 800 watt models only."

AFAIK, If your amp has this switch it's not a 1200.

Here is an image for the 800
upload_2022-9-12_13-0-56.png

Compare to the image of the 1200 I posted earlier.
 
#17
johnthebass said:
Many thanks. It does not have that switch. So it’s a misleading description on eBay. I will notify the supplier. It’s no issue just wanted clarification. Appreciate your help
Click to expand...
Not misleading at all.

To run 3 x 8 ohm cabinets, run 2 on one side off the amp and one on the other.

The amp supports 2 x 4 ohm cabinets (effective 2 ohm load) by connecting 1 x 4 ohm speaker to each side of the amp.

Please re-read the manual, it’s all there.
 
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#18
The 1200 is a dual amp configuration. Up to 600 watts per speakon output. No lower than 4 ohms pre output. You can run 8 ohms on one channel and 4 ohms on the other. Or 4 ohms on each output.

REMEMBER.

GK uses NL2 speakon jacks. NL4 WILL NOT plug in. If your speaker cable does not easily go into the plug DO NOT FORCE the issue.
 
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#19
joel406 said:
The 1200 is a dual amp configuration. Up to 600 watts per speakon output. No lower than 4 ohms pre output. You can run 8 ohms on one channel and 4 ohms on the other. Or 4 ohms on each output.

REMEMBER.

GK uses NL2 speakon jacks. NL4 WILL NOT plug in. If your speaker cable does not easily go into the plug DO NOT FORCE the issue.
Click to expand...

If I'm recalling correctly, Forest @fgallien mentioned that they had returned to NL4s but I am not sure of the production date when it changed. As you say, safety first…
 
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