Hello experts. I am currently bi-amping my Klipsch Heresey iv speakers with a C55, MC275 for the highs and mids, and a MC152 for the woofers. I have the C55 set to bi-amp in split mode with crossover frequencies set at 3000hz low pass and “bypass” for high pass. Currently the speakers are connected to the 8ohm connectors on both amps and the gold bridges are removed on the Klipsch speakers. I was thinking that the woofers are likely running at a lower nominal impedance (but can find it for these speakers) than the 8ohms listed for the entire speaker. To that end, I was thinking about using the 4ohm taps on the MC152 that is powering the woofers and the 8ohm taps (as currently setup) on the MC275 for the mids and highs tap on the Klipsch. Thoughts on sound quality, burden on the amps, any other considerations would be appreciated.
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Bi-amp Klipsch w/MC275 and MC152 at different Ohms
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I can’t offer answers to your biamping questions, but I’ve owned both the 275 and the 152 and used them on my Klipschorns. I prefer the 275 by no small margin. I agree that you don’t need to biamp the Heresys. But “need” is different for different folks. If it were I, I’d sell the Heresys and the 152–and invest in much bigger Klipsch Heritage speakers. Good luck. And Godspeed.
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Likely the 8 Ohm taps are best for both. You can test the LF in your speakers with a DMM, if you see below about 4 Ohms of DCR it is likely a lower impedance speaker and should be on the 4 Ohm taps (DCR will be lower than impedance). The 4 Ohm tap will have lower gain so you will likely need to compensate and whatever measurement equipment you’re using to balance the system should show you that.
A bigger ;problem IMO is your crossover frequencies. There is no way the LF driver in Hereseys can handle 3kHz, and the MF/HF should not be running full-range. The Heresey was not designed as a full-range music speaker and rolls off IIRC around 50Hz and can use a subwoofer for most any music, which might be a better application for the MC152 and run the Hereseys full-range from the MC275.
A bigger ;problem IMO is your crossover frequencies. There is no way the LF driver in Hereseys can handle 3kHz, and the MF/HF should not be running full-range. The Heresey was not designed as a full-range music speaker and rolls off IIRC around 50Hz and can use a subwoofer for most any music, which might be a better application for the MC152 and run the Hereseys full-range from the MC275.
Thanks for the reply SaturationPT. I don’t have that measuring equipment and was hoping someone on the forum was a “Klipsch expert” and would know the nominal impedance of the Heresey woofer. I may just try the 4ohm taps for the woofers and see, but didn’t want to accidentally damage anything.
Regarding the C55 crossovers, the instructions for setting up bi-amping in split mode are confusing to me. I can set it up in “fixed mode” and the crossover is set at 150, 350, or 900hz. I set it at 900hz since the woofers on the Heresey are 850hz. That outcome is pretty good. However, the C55 additionally allows for a “split-mode” so you can adjust the corner frequencies. That’s where it confuses me because the choices in “split-mode” are Low Pass - 600, 1200, or 3000hz. And for high pass, the options are bypass, 50, 100, or 250hz. The frequencies seem backwards and il-conceived, or I don’t understand what it’s doing. Most likely the later. If I understand what it’s doing and I choose low pass 600 for example, then all signals below 600 go to the woofer, and above 600 go no where, which is fine except my woofer handles up to 850. But 1200 or 3000hz seem way too high for low pass filters. Since it sounded better on 3000hz, that’s where I set it. Similarly, the high pass doesn’t make sense to be so low. I thought the objective would be to not send signals to the amp (MC275 in my case) that don’t need to be amplified for the mids and tweeter. So why are the filters so low? It would seem like 1000hz or higher should be the options. Why is bypass even an option? Further, none of the frequency choices between high pass and low pass match, so won’t there be a “gap” of missing frequencies in the middle range if I choose any options other than bypass??? I’m definitely confused by the McIntosh c55 explanations in the owners manual and could use some help.
Regarding the C55 crossovers, the instructions for setting up bi-amping in split mode are confusing to me. I can set it up in “fixed mode” and the crossover is set at 150, 350, or 900hz. I set it at 900hz since the woofers on the Heresey are 850hz. That outcome is pretty good. However, the C55 additionally allows for a “split-mode” so you can adjust the corner frequencies. That’s where it confuses me because the choices in “split-mode” are Low Pass - 600, 1200, or 3000hz. And for high pass, the options are bypass, 50, 100, or 250hz. The frequencies seem backwards and il-conceived, or I don’t understand what it’s doing. Most likely the later. If I understand what it’s doing and I choose low pass 600 for example, then all signals below 600 go to the woofer, and above 600 go no where, which is fine except my woofer handles up to 850. But 1200 or 3000hz seem way too high for low pass filters. Since it sounded better on 3000hz, that’s where I set it. Similarly, the high pass doesn’t make sense to be so low. I thought the objective would be to not send signals to the amp (MC275 in my case) that don’t need to be amplified for the mids and tweeter. So why are the filters so low? It would seem like 1000hz or higher should be the options. Why is bypass even an option? Further, none of the frequency choices between high pass and low pass match, so won’t there be a “gap” of missing frequencies in the middle range if I choose any options other than bypass??? I’m definitely confused by the McIntosh c55 explanations in the owners manual and could use some help.
twiiii
Lunatic Member
As the passive crossover components in the system stay in place there is no real advantage to using any form of bi wiring or bi amping . Well if you want to place the 275 on top and the 152 on the bottom then you need some form of HP filter for the 275 set below the range of the mid driver by about 1/2 octave to protect the amp and in order to get a bit of difference in the midrange sound. . Tubes don't like to drive unloaded circuits. Most tube lovers like to cover the 250 and up area to emphasize concert hall depth and to get more spaciousness around instruments. As a Hersey crossover to woofer is so much higher that prevents the real advantages of using a tube amp for the mid and highs.
Without reading the C55 manual, and I'm not home where it is convenient, I don't understand either what the split-mode is designed to do but it seems like it would work well for a subwoofer with main speakers running full-range. Fixed mode at 900Hz would more closely match what you're trying to do.
The 4 Ohm taps won't hurt anything. Most likely the speakers are 8 Ohm drivers, I'd be surprised if they are less and if the speaker is 8 Ohms nominal/rated then you certainly have an 8 Ohm LF/woofer.
The end result of splitting this into two amplifiers will however be less accurate if you are not able to balance the gain of the two amplifiers, so whatever sounds good to you will be the best result. Unfortunately it does take some instrumentation to be able to bi-amp without losing accuracy. As Twiiii mentioned, the crossover is still in circuit in the speakers, so you could run the amplifiers full-range and lose only efficiency, but it is best to high-pass the tube amp (in theory) to ensure that there isn't a lot of energy sent to the amp (and therefore output transformer) where there isn't a significant load (the LF music). That's in theory of course, and with a high NFB design it is unlikely that the output transformer will be able to go into any oscillation because of it (my opinion), still good practice to avoid potential problems and high-pass the output from the HF amplifier. Less concern about the amplifier driving the LF.
The 4 Ohm taps won't hurt anything. Most likely the speakers are 8 Ohm drivers, I'd be surprised if they are less and if the speaker is 8 Ohms nominal/rated then you certainly have an 8 Ohm LF/woofer.
The end result of splitting this into two amplifiers will however be less accurate if you are not able to balance the gain of the two amplifiers, so whatever sounds good to you will be the best result. Unfortunately it does take some instrumentation to be able to bi-amp without losing accuracy. As Twiiii mentioned, the crossover is still in circuit in the speakers, so you could run the amplifiers full-range and lose only efficiency, but it is best to high-pass the tube amp (in theory) to ensure that there isn't a lot of energy sent to the amp (and therefore output transformer) where there isn't a significant load (the LF music). That's in theory of course, and with a high NFB design it is unlikely that the output transformer will be able to go into any oscillation because of it (my opinion), still good practice to avoid potential problems and high-pass the output from the HF amplifier. Less concern about the amplifier driving the LF.
I am currently bi-amping my speakers (different speakers, different solid state Mac amps)
#1, bi-amping with tubes, getting the crossover in line on that tube amp should be the priority as mentioned. Your 275 will run cooler and you will be rewarded.
I have my lows on the 8 ohm tap of a pair of monos and the mid / high on the 4 ohm tap of the stereo amp.
I understand the gain structure between the monos and stereo is different on the different tap settings, however I am really enjoying this current configuration.
I’ve used these speakers with 4 different 2 ch amps, 2 different sets of monos and now currently bi-amping. I have tried a few different tap configurations between the 3 amps. I usually listen to a setup for a few weeks/months then try something different. I rarely leave anything set for an extended period.
I like the flexibility of having different tap settings for the lows than the mid / high. I understand this is boosting the woofers by a few dB, one because the monos have more power and two because I’m using different taps. But this has been a fun experiment and I am enjoying the sound the most this way in my room.
Right now output 1 is going to my lows and output 2 is going to mid/high. Being able to toggle either output off by the remote is nice.
Your mileage may vary.
#1, bi-amping with tubes, getting the crossover in line on that tube amp should be the priority as mentioned. Your 275 will run cooler and you will be rewarded.
I have my lows on the 8 ohm tap of a pair of monos and the mid / high on the 4 ohm tap of the stereo amp.
I understand the gain structure between the monos and stereo is different on the different tap settings, however I am really enjoying this current configuration.
I’ve used these speakers with 4 different 2 ch amps, 2 different sets of monos and now currently bi-amping. I have tried a few different tap configurations between the 3 amps. I usually listen to a setup for a few weeks/months then try something different. I rarely leave anything set for an extended period.
I like the flexibility of having different tap settings for the lows than the mid / high. I understand this is boosting the woofers by a few dB, one because the monos have more power and two because I’m using different taps. But this has been a fun experiment and I am enjoying the sound the most this way in my room.
Right now output 1 is going to my lows and output 2 is going to mid/high. Being able to toggle either output off by the remote is nice.
Your mileage may vary.
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