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Author Topic: Renkus CFX121 Bi-amping  (Read 186 times)

Mario Savard

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Renkus CFX121 Bi-amping
« on: March 23, 2020, 09:48:03 pm »

Good day everyone,

This might be a relatively simple or stupid question but i'm reading too many forums that conflict each other and it is leaving me confused. Also the user manual has limited in information.

I am installing some Renkus-Heinz CFX121 speakers and they run at 4ohms. They have a 4ohm LF driver and a 8ohm HF driver.

When i biamp, what is the new impedance of the LF and HF signals? Are they both 4 ohms , or LF @ 4ohms and HF @ 8 ohms?

Also, if anyone has insight on proper crossover setting as the user manual has no specs for crossover for bi-amping. I'm using a DBX driverack PA2.

Thank you for your knowledge!

Mario Savard
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Caleb Dueck

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Re: Renkus CFX121 Bi-amping
« Reply #1 on: March 24, 2020, 03:00:28 am »

Good day everyone,

This might be a relatively simple or stupid question but i'm reading too many forums that conflict each other and it is leaving me confused. Also the user manual has limited in information.

I am installing some Renkus-Heinz CFX121 speakers and they run at 4ohms. They have a 4ohm LF driver and a 8ohm HF driver.

When i biamp, what is the new impedance of the LF and HF signals? Are they both 4 ohms , or LF @ 4ohms and HF @ 8 ohms?

Also, if anyone has insight on proper crossover setting as the user manual has no specs for crossover for bi-amping. I'm using a DBX driverack PA2.

Thank you for your knowledge!

Mario Savard

These aren't bi-amped speakers.  500@4 for the regular model CFX121, or 500@8 for the CFX-121-8 model.

If you think biamping without factory settings, through a Driverack, will improve performance - better to save your money for better speakers and DSP. 

I've used those speakers, they were designed to hit a price point.  They're OK, for the price. 
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Chris Grimshaw

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Re: Renkus CFX121 Bi-amping
« Reply #2 on: March 24, 2020, 05:04:26 am »

IMO:
- Up to around 500w continuous power ratings, it's best to leave speakers with the passive crossover in place, and just get some EQ settings together. My small FOH mains are 10" coaxials rated at around 300w, so I designed and built a ~2kHz passive crossover for them.

- Above 500w, I'd bi-amp. My big FOH mains are 2x10"+HF. The 10"s are rated for 600w continuous each, so the amplifier I use is happy to drop a few kilowatts into that box. A passive crossover at 900Hz would've been a huge undertaking, requiring many large components, so I keep those bi-amped.

The speakers you have are well under 500w, so I'd leave them be. There's not much to gain with bi-amping them, and you've the potential to blow out a few HF drivers before you figure out the crossover.

Spend the money that would've gone to extra amp channels, and put it towards a measurement setup so you can get the best out of the existing crossover.

Chris
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Mario Savard

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Re: Renkus CFX121 Bi-amping
« Reply #3 on: March 24, 2020, 09:45:59 am »

Thanks for the advice. I'll consider.

I have another question.

The CFX121 can be fit with a 120x60 dispersion.  Doing so, do you lose "throw distance" or any intelligibility as opposed to using the 90x60 pattern?

Thank you for your insights

Mario Savard
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Chris Grimshaw

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Re: Renkus CFX121 Bi-amping
« Reply #4 on: March 24, 2020, 11:51:18 am »

By spreading the sound out wider (by using a different HF horn), you'll lose a little on-axis sensitivity. I would hope there are connections in the crossover to adjust for this.

Please note that simply swapping the horn out will only affect the dispersion over a fairly narrow frequency range. YMMV.

Chris
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Luke Geis

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Re: Renkus CFX121 Bi-amping
« Reply #5 on: March 24, 2020, 03:46:12 pm »

Don't bother with bi-amping, they are great speakers and are rather efficient. I own a set of the CFX121M's and they have been wonderful for me.

As to the horn width. Throw is not a word that has much meaning in audio. While it would be nice to think that a speaker with narrower coverage throws audio further it isn't quite like that. I prefer to think of it as focusing. If you have a narrow coverage horn, you have the majority of the energy focused into a smaller area. Because the energy is focused it holds together over distance and beams at you a little more. The problem is that it does this only at frequencies that the horn can control. For most horns, the area of actual control is around 5khz and above. If you look at the polar graphs of most speakers, the higher frequencies often cover a smaller area than the nominal coverage the horn suggests. All this means is that while the horn may be crossed over at 2khz, it can't really control the direction of the sound to a great degree until around 5khz or higher. So a narrower horn will just have beamier HF output that you can hear better over distance, but only on-axis. Wider horns take that small bit of on-axis energy and trade it for a little wider sweet spot. So at distance, you may have a little bit less output, but you have a wider area in which the sound should be more uniform.

So for the purpose of " throw ", I would not worry about the coverage of a speaker. 50' is the practical limit for most conventional speakers to cover, regardless of coverage. Now where coverage is of much more importance would be when the speaker is near walls or in close proximity to another speaker, or perhaps when the speaker is pointed at a specific zone that you need to reduce splash off of other hard surfaces. If the HF content is allowed to bounce off of hard surfaces it will quickly wreak havoc on it. Same with Lo and MID frequency content, but the majority of intelligibility is held together in the upper octave between 1k and 4k. So having a horn that can do good to control frequencies from 1khz and above will help greatly and the added beaming of the focussed on-axis sound will help in the small area that the speaker is directed at. A wider coverage speaker is great for larger areas or where wider coverage is needed of course.

If you can get EASE Focus 3 from QSC, you can model some predictions using a generic speaker to get an idea of what will work for your establishment.
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Re: Renkus CFX121 Bi-amping
« Reply #5 on: March 24, 2020, 03:46:12 pm »


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