Kef R7 Meta bi amping

[TheOneTruePath]

I'm taking delivery of a nice new pair of R7 Metas in a few days. I have a Yamaha RX-A1010 amp which seems to allow bi amping. But I'm not sure I should even bother as presumably:
1. The amp is going to send the 'full frequency range' to each driver
2. The speaker is then going to filter out the frequencies for the particular driver

So my question is... what happens to the 'unused frequencies' which are filtered out? I'm pretty sure the energy isn't dissipated in the crossover, so presumably the amp just sees a very high impedance for those frequencies and not much energy goes into amplifying them.

Which makes me wonder... does the amplify as a result generate more distortion than it otherwise would? Or does it just put the energy into the unfiltered frequencies and give the desired result, ie more watts available per driver and less low frequency energy 'interfering' with the high/mid amp circuit/speaker wires/driver (and/or less high frequency energy mucking with the woofer stuff).

I'm not convinced that low frequency energy can in any way 'interfere' with high frequencies in an amp circuit and/or speaker wires in the first place...

So realistically, with an amp that can output 110W per channel into 8 ohms (with two driven) and presumably somewhere from 150W to 170W or so into the Kef's 4 ohms, bi amping will give me only a bit more power per channel. And nearly all the energy is going to the woofers anyway. So to get a significant power increase would I need to try and drive one low and one high driver from each channel?

And will I see an improvement in reduced distortion from separating frequencies at the speaker... it's not clear to me that this is going to happen.

What's the prevailing feeling on this, should I even bother? I see plenty of people trumpeting the virtues of bi amping from the rooftops, but plenty more saying it's just oxygen-free copper all over again...

 

[MacCali]

I'm taking delivery of a nice new pair of R7 Metas in a few days. I have a Yamaha RX-A1010 amp which seems to allow bi amping. But I'm not sure I should even bother as presumably:
1. The amp is going to send the 'full frequency range' to each driver
2. The speaker is then going to filter out the frequencies for the particular driver

So my question is... what happens to the 'unused frequencies' which are filtered out? I'm pretty sure the energy isn't dissipated in the crossover, so presumably the amp just sees a very high impedance for those frequencies and not much energy goes into amplifying them.

Which makes me wonder... does the amplify as a result generate more distortion than it otherwise would? Or does it just put the energy into the unfiltered frequencies and give the desired result, ie more watts available per driver and less low frequency energy 'interfering' with the high/mid amp circuit/speaker wires/driver (and/or less high frequency energy mucking with the woofer stuff).

I'm not convinced that low frequency energy can in any way 'interfere' with high frequencies in an amp circuit and/or speaker wires in the first place...

So realistically, with an amp that can output 110W per channel into 8 ohms (with two driven) and presumably somewhere from 150W to 170W or so into the Kef's 4 ohms, bi amping will give me only a bit more power per channel. And nearly all the energy is going to the woofers anyway. So to get a significant power increase would I need to try and drive one low and one high driver from each channel?

And will I see an improvement in reduced distortion from separating frequencies at the speaker... it's not clear to me that this is going to happen.

What's the prevailing feeling on this, should I even bother? I see plenty of people trumpeting the virtues of bi amping from the rooftops, but plenty more saying it's just oxygen-free copper all over again...

I think the simple breakdown, and I’ve actually purchased two amps for this bi amping in line with an active crossover.

But the bad news is you would need to remove the internal crossover. So if it’s not a strictly power based situation I would not do it.

Also not an audio expert and personal I did not notice a difference with one of these steps.

1. Make your own jumper using speaker cable. As in disconnect the internal jump by rotating the nob and add any speaker cable to connect
2. Put the speaker cable input into the top inputs and not the bottom.

All a bunch of boulder dash really, but it may help you sleep better at night. Just a much cheaper route.

 

[fpitas]

the energy isn't dissipated in the crossover, so presumably the amp just sees a very high impedance for those frequencies and not much energy goes into amplifying them.

Exactly.

 

[fpitas]

I'm not convinced that low frequency energy can in any way 'interfere' with high frequencies in an amp circuit and/or speaker wires in the first place...

Conceivably it might in a badly designed amp. Not in wires unless they have poor connections.

 

[fpitas]

But the bad news is you would need to remove the internal crossover.

And that crossover offers individual driver EQ, tailored to the driver response in the box. You will have to replicate that EQ if you go fully active.

 

[fpitas]

Some light reading: https://sound-au.com/biamp-vs-passive.htm

BTW, I use an active crossover. But it has challenges if you aren't technical.

 

[Tovarich007]

Kef R7 Meta is a very well designed and optimized speaker as a passive design. Why do you want to bi amp it ?
Unless you're a quite seasoned Diyer and you have good measurements tools, it's not worth the game.

You'll have to withdraw the passive filter, risking some damage to the fine esthetics of this speaker, then you'll have to design, implement and precisely calibrate your own active filter, which isn't an easy task, and then measure the results and if necessary modify the active filter and/or recalibrate the DSP if you use one.

My advice, keep everything simple, that means keep the original design and enjoy the music ! this is one of the best passive speaker out there on the market, and a good passive is far better than a bad active one.

 

[TheOneTruePath]

Kef R7 Meta is a very well designed and optimized speaker as a passive design. Why do you want to bi amp it ?
Unless you're a quite seasoned Diyer and you have good measurements tools, it's not worth the game.

You'll have to withdraw the passive filter, risking some damage to the fine esthetics of this speaker, then you'll have to design, implement and precisely calibrate your own active filter, which isn't an easy task, and then measure the results and if necessary modify the active filter and/or recalibrate the DSP if you use one.

My advice, keep everything simple, that means keep the original design and enjoy the music ! this is one of the best passive speaker out there on the market, and a good passive is far better than a bad active one.

I was never considering 'fully active' bi amping, ie using a crossover in front of the amplifier power section to restrict the frequencies supplied to the amplifier circuit. I'm pretty sure you can't easily do that with my Yamaha RX-A1010 integrated amp, also there's no way I'm going to either hack into the speaker cabinet or second guess the Kef crossover designers.

It was never my plan to modify the speaker or change the crossovers except by rotating the knob to disconnect the internal jumper so that I can drive the two sets of drivers with two amplifier channels. This is well within the Kef designers' plans - they do after all supply two pairs of terminals with jumper knobs specifically for bi amping. And I won't need to do any tuning of crossovers or measuring. The speakers will be using the standard built in crossovers to supply the same frequencies to the drivers that the designers intended. Just supplied from an extra (identical) pair of volume-linked amplifier channels, also 'as intended'.

Probably I'll use 'horizontal bi amping' as opposed to vertical. In other words, I'll connect 'Front Left' to the bottom pair of terminals on the left speaker and 'Front Right' to the top terminals on the right speaker, then 'Spare Left' to the top terminals on the left speaker and 'Spare Right' to the bottom terminals on the right speaker. Obviously on the Yamaha I then go into the menu and turn on the 'bi amp' option. Thus allowing 'Front' circuit to drive one low frequency driver and one mid/high, and the 'Spare' circuit the same. Ie dividing the LF/high power job between the two amp circuits. It means there is an asymmetry between power going through left/right channel on each circuit, with the left producing most of the power on one circuit and right on the other. I'm hoping that the Yamaha is designed well enough that this doesn't introduce distortion. Also I'm hoping that you do actually get more headroom doing that. If the left and right channels on each circuit have completely separate power supplies there would be very little 'power headroom benefit'. The alternative, ie vertical bi amping, would have nearly all the power used by one amp circuit and the high frequencies by the other. I figure that giving the amp more power headroom has greater potential to improve things. But this is just a guess.

Both vertical and horizontal bi amping could have the potential to sound better, and I don't have to buy another amp since it already has a spare (identical) circuit and bi amping capability. All I have to do is run another pair of speaker cables and do two minutes of reconfiguring.

My question is, can I expect any difference at all with either horizontal or vertical bi amping? Will I have to turn the volume up to 90% and rattle the windows before I notice a difference? Or will I have to turn the volume up *and* measure the distortion with an expensive device to notice the difference?

I'll probably be attempting to answer this myself soon as the Kefs arrived today, and I can tell you that they sound amazing, apparently my early 80s B&W DM2000 speakers weren't as marvellous as I thought they were for the last 30 years. I have a subwoofer filling in the low frequencies, when brand new the Kef's base is a bit lacking. I have a friend that bought R3 Metas a month ago and he was worried for two weeks before the base filled in. Also he went out and bought a sub after I took mine around there so he could hear the difference.

 

[TheOneTruePath]

I tried horizontal bi-amping and could not hear a difference at all. Probably there was more headroom for turning the volume up, but not down at the levels I was prepared to go to. Also, the Yamaha RX-A1010 loses the two 'back surround' channels if you enable bi-amping. No big deal if there was an audible improvement for stereo music as those speakers are not much good on my system anyway, but with no improvement that I could discern I may as well keep the 7.1 capability. On the plus side, I tried one of the Kef R7 metas in the centre channel just to see how much clearer movie dialog would sound, and I now have an R6 meta on order. They really are super clear. Of course the HiFi guy said I would eventually end up with side and rear Kefs as well, but that's his job. I can live with super clear stereo music, super clear movie dialog and the surround stuff can be as messy as it wants.

Proper active bi-amping sounds very interesting, but I guess now I've gone a different way by putting pretty much all my upgrade budget into really well integrated 3-way speakers.

 

[popej]

I have Yamaha receiver with too. I'm tempted sometimes to make a use of free channels for bi-amping fronts. But I just think, it is not worth all the trouble with connecting more wires

That being said, your speakers have crossover at about 400Hz, which more or less divides power at equal level for each way. If you bi-amp them, than all 4 amps will share similar load. I think this would make a very slight improvement in cooling. Nothing you would notice, but still some advantages

 

[MacCali]

I tried horizontal bi-amping and could not hear a difference at all. Probably there was more headroom for turning the volume up, but not down at the levels I was prepared to go to. Also, the Yamaha RX-A1010 loses the two 'back surround' channels if you enable bi-amping. No big deal if there was an audible improvement for stereo music as those speakers are not much good on my system anyway, but with no improvement that I could discern I may as well keep the 7.1 capability. On the plus side, I tried one of the Kef R7 metas in the centre channel just to see how much clearer movie dialog would sound, and I now have an R6 meta on order. They really are super clear. Of course the HiFi guy said I would eventually end up with side and rear Kefs as well, but that's his job. I can live with super clear stereo music, super clear movie dialog and the surround stuff can be as messy as it wants.

Proper active bi-amping sounds very interesting, but I guess now I've gone a different way by putting pretty much all my upgrade budget into really well integrated 3-way speakers.

I think bi amping is probably best thought of as a way to add flavor. Not a very fun way to do it, since from what I’ve seen people will do tubes or class D on top and A or A/B for bass.

Also if a speaker needs massive power to fill a giant room.

Also if you did have a massive room and tried to push it to the upper registers you would probably need to do a few more things.

 

[Daka]

Let me add my two cents on this old post.
Passive Bi amping when using quality amps makes no difference. In the other hand when using reciever’s ratherpoor integrated amps (those rated to 6ohms and not performing well when it drops below 4 like Kefs do) - in this situation yes you might hear a difference by separating mid highs amplification from low.