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Any Rules For Mixing Cabinets?

#121
Mike SS said:
I have always used combo amps, so I am not too informed when it comes to stacks.
I recently acquired a Crate BT350 head for my 15 year old son, and picked up a near new GK BLX 4X10. It's an 8 ohm cab so his amp is putting out 200 watts. Adding a second 8 ohm cab will give him 350 watts, and a 4 ohm load, according to the manual I scrounged. Now I have read on a recent thread that if you mix cabinets with different speaker configurations, like a 2X10 and a 4X10, the 2X10 will end up getting more power directed to it. Would this also be the case if I made his second cab a 1X15? Would it be easier/better to just get a single 4 ohm cab to maximize his amp output? I was kind of hoping to mix a 8 ohm 2X10 and a 8 ohm 4X10 as a stack and this would also give him the option of using one, or both of the cabinets depending on gig requirements.

Any suggestions would be appreciated.
Click to expand...
Hope this helps :


My current setup consists of a GK 1001 RB 2 x 10 combo, and extension cabs Backline 4 x 10 and SBX II 1 x 15. My question relates to speaker cab combinations. With my current set up I can use a 6 x 10, 2 x 10 and 1 x 15 or 4 x 10 and 1 x 15. All of which I enjoy the sound variation this provides.

• I have been advised that it is not a good idea to mix and match speaker cab combinations
• Therefore using a 1 x 15 SBX II and a 4 x 10 Backline may not be a good choice according to some
• There are some purists who recommend only using matching cabs i.e. two 4 x 10 cabs @ 8 ohms to reach a 4 ohm load
• Is there any problem with mixing up these cabs as I have described

Can you please speak to this, and lay it to rest once and for all. I have seen different artists utilize different extension cab combinations. For larger venues I prefer the 1 x 15 and 4 x 10. I enjoy the sound I get from all of my GK cabs. Can you offer any technical advice ?

Answer from GK:

The only concern to have is the ohm load. The 1001RB is stable down to 4 ohms. This will accommodate the internal speakers plus one 8 ohm cab or 2 external 8 ohm cabinets. It sound like you are aware of this but I want to make sure you are.

Beyond the ohm load consideration, I would say use whatever combinations you like. There are many “experts” online that love to share their opinions. Many of these guys are informed but many are not. Some people will attempt to apply hi-fi concepts to musical instrument amplification that are either not applicable or have no real benefit outside of a controlled acoustical environment.

Thanks,
Jason
GK


I don’t claim to be an expert on much but I have seen guys obsess over inconsequential things and forget to actually play the gear. Meanwhile, there are a lot of guys out making a living using the rigs that the “experts” claim are inferior.

I am of the mindset that blending the response of multiple speakers can yield great results. One speaker may lack somewhere and another driver can compliment it in a positive way to “complete” the sound you are CREATING. If you want to play pre-recorded music and sit between two speakers in an acoustically neutral room it may make a difference I suppose. However, you are making the sound you want to hear with an instrument that is imperfect in a room that is almost always the worst possible environment acoustically. To make any nuance even more difficult to perceive, you are usually standing next to a guy who is banging on a plastic skin stretched across a wooden hoop and flattened pie tins 

Let me know if I can assist in the future.

Jason
GK
 
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#125
Ric5 said:
Check out the pa system that Pink Floyd was using back in the early 70s ... all sorts of different cabs mixed together ... it was probably the best PA system of any major band at that point in time ... go to about 10 minutes into the video

Click to expand...

Thanks for sharing the video of Pink Floyd. I saw them live in Chicago back in 1977 during the Animals tour...they were awesome !!!
 
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#131
Sorry to change the subject just to talk about Bag End again.. I have a Bag End 12 on top of a 15. Definitely more woof comes out of the 15, more zing from the 12. I think they sound great together. Both 200 watt/8 ohm. Works great.
 
#132
.. there is already more than enough to boggle ones mind in this thread, BUT, with that said, lets just say that not all cabs are created equal ... so when I read:

"I recently acquired a Crate BT350 head for my 15 year old son, and picked up a near new GK BLX 4X10. It's an 8 ohm cab so his amp is putting out 200 watts. Adding a second 8 ohm cab will give him 350 watts, and a 4 ohm load, according to the manual I scrounged ..."

.. then I read all the posts suggesting another matching cab, it is with all due respect that I would qualify the recommendation with 'unless it is a GK Backline Series cab' ... I know they are inexpensive, but again... not all cabs are created equal (as not to offend any that happen to like/own the Backline series cabs) ... I would not be a fan of compounding an earlier expense on a 'marginal' cab in the quest of achieving a slight increase in overall amp output ... there are much better options available for cabs in not all that much more $$ range ...

JMHO .. as always ;)
 
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#133
If this has ever been done, I apologize. I'm a visual person, so I figured I show some illustrations relating to phase differences between cabs and why mixing cabs can be a bad idea. If you have no idea what any of this means, just enjoy the pics. I used WinISD and LTspice.

This pic shows 3-100Hz sine wave signals. Green is perfectly in phase (consider it the reference). Blue is 60 degrees out of phase relative to green. Red is the sum of the two signals. Notice the reduction in level of the red signal. In theory, two signals that are 180 degrees out of phase with each other will completely cancel out.

mixed sig.png


This pic shows a frequency response plot of 4 different ported speaker cabinet concepts:

Yellow = a single 15 cab tuned low
Blue = a more different single 15 cab
Pink = a typical 2-12 cab
Green a typical 4-10 cab

mixed tf.jpg


This pic shows the phase response for the same 4 cabinet concepts:

mixed phase.jpg


Phase plots can be a little strange if you're not used to seeing them. I typically think of the area between 60Hz and 100Hz the "money zone" for bass guitar, so focus on that. Look at the phase differences between these cabs! You may be thinking, hey, none are perfectly in phase! Well, that's a more complicated subject. Speaker cabinets introduce phase shift as well as the speakers themselves--can't be avoided. EQ's mess with the phase as well. We're talking about mixing cabs here, so we're concerned with relative phase to each other.

Anyway, let's pick a frequency...80Hz. 80Hz is close to the second harmonic of a low E string...in other words, money.

Yellow = 58 degrees
Blue = 95 degrees
Pink = 128 degrees
Green = 139 degrees

They are all somewhat out of phase with each other, so they would all have some cancellation when used together. The worst case is Yellow and green, which in this case happens to be a 115 and 410--they are 81 degrees out of phase at 80 Hz. The best case is Pink and Green, which happens to be a 212 and 410--they are 11 degrees out of phase at 80Hz. Those would probably play okay together because the phase between them is consistently not too far off. Check out yellow and blue from 200 to 1K--they are pretty much perfectly in phase in that range. Down low, not so much.

Anyway, think about the first pic that shows a 60 degree cancellation. If you pick any two of the phase plots at a given frequency, you can probably imagine the resulting signal loss.
 
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#134
BbbyBld said:
If this has ever been done, I apologize. I'm a visual person, so I figured I show some illustrations relating to phase differences between cabs and why mixing cabs can be a bad idea. If you have no idea what any of this means, just enjoy the pics. I used WinISD and LTspice.

This pic shows 3 100Hz sine wave signals. Green is perfectly in phase. Blue is 60 degrees out of phase relative to green. Red is the sum of the two signals. Notice the reduction in level of the red signal. In theory, two signals that are 180 degrees out of phase with each other will completely cancel out.

View attachment 834870
Click to expand...
Why 3100 Hz, wasn't 3kHz sufficiant enough? Green is perfectly to what kind of reference?
At this (very top) frequency range coil inductance dominates the Impedance and phase thus drivers/woofers are very equal in phase.
BTW Lorentz force (i*B*l) does not include any spring constant (suspansion rate).

Either way the samples are not suitable to prove reasonable "phase issues" myths anyway.
 
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#136
BbbyBld said:
This pic shows a frequency response plot of 4 different ported speaker cabinet concepts:

Yellow = a single 15 cab tuned low
Blue = a more different single 15 cab
Pink = a typical 2-12 cab
Green a typical 4-10 cab

View attachment 834877
Click to expand...
I'd call it confusion cause the very deep low going one is of very likely of very poor efficience and not suitable to cope with the other ones in SPL, actually impractical.
The custom SPL is not shown but, I ain't *****.
 
#137
Nothing really in print but should you proceed with the aforementioned topic and actually mix cabinets prepare to receive a harsh reprimand from the SFPOMC (Society for the prevention of mixing cabinets). There are a number of charter members here on TB.
 
#139
BbbyBld said:
Yellow = a single 15 cab tuned low
Blue = a more different single 15 cab
Pink = a typical 2-12 cab
Green a typical 4-10 cab

View attachment 834877
Click to expand...
Blue 115 looks like it could be become problematic in some sensitive rooms enviroment due to highish Qtc, either way mixed or matched.
The remaining two cabs seem to be good allrounder. But very likely designed for smaller cab chambers in this case to emphasize phase issues with the other ones (I think).
BTW the remarkable humps are typical with some eminence drivers (which I assume strongly), no need to talk home about.

edit,
In addition, the blue 115 phase response looks like there is some Group Delay deviation in relation to the other ones.
 
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