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Discussion in 'Amps and Cabs [BG]' started by estimated_eyes, Aug 28, 2019.
Nope, and especially not so with the old 800RB.
Just curious what makes bi-amping any different with the 800RB as opposed to the 700RBii
Would like to eventually be able to do this with my head.
IIRC the 700RBII has a fixed crossover point at around 5KHz (@50 watts max), so it's really kind of just meant for the "air" thing. You also need to break out the high and low outputs outboard unless using a GK cab meant for biamping. I.E. a breakout box, split Speakon cable, or custom wiring at the cab end.
The 800RB crossover is variable and works at much lower frequencies, and therefore can be used sensibly with cabs like 110s, for example. It also has a separate output jack for the HF output, and that output is infamously only rated for an 8 ohm minimum (@100 watts max), with potentially dire consequences for those who ignore that.
The older series stuff had a variable crossover frequency that could sweep over a pretty broad range, IIRC. Plus they had enough power in the HF section to driver another modest-sized speaker cabinet. The newer stuff is set up with a fixed frequency (IDK what freq.) and has only 50 watts. It seems they intend for it to only be used with a compression-type horn driver, such as found in their cabs. The older ones are a little more versatile, but also more vulnerable to misapplication.
Ahhh this makes sense. Thank you both for the replies!
more like 68 watts the actual rating from national semiconductor for the chip being used.
And yes its just a matter of time before a typical 4 ohm cabinet goes on that 8 ohm min output. kaboom lol
68 watts is perfectly fine for 5k and above. mainly cause there really isnt anything over 3.6k for bass. so it doesnt take much power to accurately reproduce amplifier hiss and fret noise lol.
if you really really wanted top end clarity from bass. its ideal id say for acoustic or clean electric bass tone. youd actually use a horn designed to go down to 800 or 1.2k hz. likewise use a compression driver that would go anywhere close to that. which means a somewhat large horn and somewhat very expensive driver.
recent attempts that would be better design would be using 5" or 6" mid drivers. still limiting and somewhat waste of time. efficiency is low and would require 2 or more drivers. and highend still doesnt get much better above 3k
Right way to do it, would be using 2" or 3" drivers for highs. again same problem, efficiency is very low would require at least 3 to 5 drivers.
and it appears GENZ BENZ has been the only one that gets it. And pretty much did exactly that.
Assuming they understand basic correction networks for a amplifier. Knowning the oscillation and horrors any passive crossover network will cause. which is pretty simple and well known. and im sure hopefully covered by any manufacture.
GKs failure with using chipamps. would have been been easily solved if they realized the thermal drawbacks of smaller chips. you would simply use 2 chips in parallel, with DC correction. And unfortunately like always National had datasheets that well covered the limits of the chips and included designs as described with anywhere from 2 to 8 chips in parallel . also with correction networks to stabilize a amplifier being used with passive crossovers....people just cant read datasheets and application papers apparently. there is a little graph lol at the bottom of the page showing thermal limitations. likewise a formula for the heatsink. meaning if you checked your numbers. the one you used is too small. lol as always
IME with the chip amp used in that amp, and I've only used maybe 10k of them in my design career, they are just about bulletproof. The protection systems (there are many) within the IC are very, very robust and comprehensive. In fact, when doing fault testing for safety certification, the test lab was unable to damage the IC no matter what they did to it and out of the 10k that we used, we only saw a few fail over 10+ years.
Where GK (and others, this is not a manufacturer issue) had a problem was with their discrete tweeter amp. No matter how comprehensive you try to make such protection networks, it's virtually impossible to make them as good as when they are fabricated on the same piece of silicon, as in the IC being discussed above. The thermal feedback (which governs VI protection and bias tracking) is almost instantaneous compared with a discrete design, and all elements of the protection also track thermally.
The only way that I know of to increase the changes of failure (from outside the amp) is to connect the output of the high frequency amp to that of the low frequency amp. Generally it will survive but not always.
Since y'all were mentioning the B115-M and B215-M, I thought this might be appropriate to add:
https://www.electrovoice.com/binary/B115-M and B215-M EDS.pdf
Note the pre-shaping filter with -3dB at 100Hz, which becomes -6dB at 50Hz. -6dB is 1/4-power, which corresponds to a mechanical test limit of 200 watts at 50Hz. This is, I believe, one of the primary causes of failures in real world bass guitar speaker applications when actually used with amps greater than say 300-400 watts RMS. When this driver came out, most bass amps were small enough that these limits were not an issue, but that's far from true these days.
This response relates to the 700RB and 1001RB amps.
From a practical sense that is true. Who else makes a bass cab where the woofer is connected to pins 1+,1- and the tweeter is connect to 2+,2-?
From a theoretical standpoint, you could use some PA cabs as the connection scheme is not unusual. However some things to keep in mind that may degrade your experience with a PA cab: GK uses a 5K HPF that is always engaged on the tweeter. The LPF on the woofer is selectable. In other words you can run the woofer full range or apply a 5khz LPF.
If you made your own it would work fine. Just honor the impedance limits of the GK power amps and use drivers that would be compatible with a 5khz crossover.
FYI, the older 2000RB biamping capability was more like the 800RB. The 2000RB was essentially a dual mono amp that could be biamped or setup for bridged mono. Each output section was rated for 225W at 8 ohms, 350W at 4 ohms, and 500W at 2 ohms. In bride mode that amp was rated for 700W at 8 ohms or 1000W at 4 ohms. In biamp mode, the outputs were still on pins 1+,1- of the respective outputs. A variable crossover could be set from 100hz to 1khz.
Early 2000RBs actually were voiced more like modern RB series amps. But over time, updates were released that changed the voicing subtly to be more like the 800RB.
That’s how I used to blow my SWR 10”s...using 1400watts
That’s true of modern “horn crossover” GKs.
I use an 800RB. 300watts below 250hz into TL606 and 100watts above 250hz into EV 12. It’s like having a guitar amp handling the mids/highs up top and the TL606 handling the omph below. Killer and super efficient/loud rig. Too loud, really!
Ahh man thats awesome!
I've been running something similar lately, without the bi-amping.
Right now I have my 700RB going into my 606 cab and I'm running a split from my pedalboard into my small Kustom 112 combo (35 watts?). Sounds awesome.
Found a Mesa Boogie Diesel 215 for sale locally, but the guy is asking too much for the cab IMO. Speakers have already been re-coned.
Which reinforces my point that the EVM drivers are not as robust as some think they are for bass guitar applications, especially when driven beyond their "RMS" (or continuous average power) rating. There simply isn't enough mechanical robustness for this application.
That said, with lower powered amps there is a unique openness to the mid voicing that is what drove some of us designers to those drivers in the first place. When bass amps were 200 watts into 8 ohms and 400 watts into 4 ohms, there wasn't much of a problem. That all changed with bigger amplifiers that even the modifications of the ProLine version couldn't fully overcome. In real world terms, they increased the rated power (in my experience) from roughly 150-200 watts RMS to 200-300 watts RMS depending on the effectiveness of any highpass filtering that the amp might have. With a Subway, I would suggest that 300 watts would be ok, but with a Carbine maybe 2002225 watts would be more appropriate for a long service life.
Funny, @agedhorse , when I asked the owner if they were ever re-coned and he said yes, I actually thought of you
I like to see those who take the effort to read and learn about this stuff actually be able to be at an advantage when dealing with it. Knowledge really is power, I'm in admittedly unique position in that I have been on this industry for a long enough time to have actually designed with this technology and know first hand the benefits as well as the limitations that different parts or approaches might bring.
I share this because I get so many PM's from guys here who are desperate to learn more and to cut through the BS and bad (or misleading) information to reduce confusion. I'm paying back for the opportunities I had early on when this information was just about impossible to get. I learned from some really sharp guys in the 1970's and early 80's, so I didn't have to make as many mistakes by myself. It's always better to learn from somebody else's mistakes... especially when it comes to things like skydiving
Thanks to the knowledge from agedhorse and TB in general I’ve been able to get incredibly satisfying results with my live sound using “outdated” gear. I actually prefer the tone of lower wattage equipment, and learning how to use it properly has been a godsend. It’s actually stopped me wasting money on gear I don’t really need!
This is a very similar solution. Good work!
This current setup is probably plenty loud for the volume I need on stage, as most gigs we play are going through a house system. I know I'm not the only one here who likes my sound to kick me in the chest, but it also doesn't always make sense.
It would be ideal if I could push more than 35 watts out of my Kustom, but that is what it is for now. I think I'll keep an eye out for another 606 or a 210 if they happen to pop up used.