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Belles for center channel


luddite

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A little help here.  I have a pair of Belles used as center channel speakers in a rather large listening room (approx 34' by 22').  I have Khorns in the corners, driven by a McIntosh MC 2720.  My preamp is a Macintosh C27, which has a dedicated center channel output.  That output is fed into a McIntosh MC 2125, and out to the Belles.  I have the McIntosh center channel amp set up as a mono block.  McIntosh says to wire the left and right 16 ohm taps together, hook the negative speaker wire to the left common tap, and hook the positive speaker wire to the left 16 ohm tap, when using the amp as a mono block .  I am using 2 speakers as my centers, not one.  Should I then hook up the positive speaker wires to the 8 ohm tap on my amplifier?  I am not sure what happens to speaker output when I have 2 speakers hooked up to the same output on the amp.  And should I still connect the 16 ohm taps on the amp to bridge the channels?  The system sounds OK as I have it, but I notice the output for the MC 2125 is much less than what I see for the MC 7270 when I crank things up.  I'd rather not cook the system...

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In that scenario, you would go from the amp positive to the positive of one speaker, the negative of the amp to the negative of the other speaker. Then, a single wire connects the two remaining post on the speakers.  That is a series connection which will raise the impedance seen by the amp. If the speakers are 8 ohm per, then I believe the 16 ohm taps would get used. 

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I'm a little surprised that Mac lets you do that.  But they must know what they're doing.

 

It seems to me that if you put the two 16 ohm outputs in parallel you're getting a combination having 8 ohms output impedance.

 

However, Belle's input impedance, like the K-Horn, dips to 4 ohms and thus you're getting a load impedance down to 2 ohms.  (Yeah I see that the amp is rated for that but the circumstances are not clear.  Maybe something to do with using a lower tap?)

 

Anyway, to me it seems kludgy to run the two channels of the amps in parallel and the two speakers in parallel.

 

So, I'd suggest just hooking up the respective amp channels to the speakers using the 4 ohm and ground taps on each channel. I.e. not trying to create a mono-block.   And use the 4 ohm taps for driving the K-horns too.  Then drive the center amps with a Y connector from the center channel output of the pre-amp.   The amps should be happy.

 

It would be interesting to experiment with just feeding the center Belles with one left and one right, assuming they're positioned cheek to cheek and in phase.  Just rely on their physical proximity to get a left plus right mix.  It's possible you'll get a variation on a pure L+R center, but I've never tried it. [Addition by edit.  Of course with this you lose the convenience of that one center volume level on the top of the preamp.]

 

Let us know.

 

WMcD

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I would use a single Belle, or stack them vertically (invert the top one).

 

While the Belle can drop down to 4Ω, the MC2125/2120 can drive it with ease on the 8Ω tap. You can strap the outputs in parallel (if the amp is perfect), use the 8Ω taps though. If you insist on using both of the Belle, I would run one per channel and use a 'Y' cord on the amplifier inputs.

 

The MC2125/2120 can take massive abuse, I have driven it into 2Ω on the 8Ω tap with the PowerGuard defeated! It will make popping and barking sounds when driven more that 6dB into clipping in this fashion (8 LaScala bass bins in series-parallel on one channel, mids and HF on the other channel).

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I sent an inquiry to McIntosh customer support.  I have had good luck over the years with their technical support guys.  Sometimes it takes a few days for a response, but they do follow up, even with equipment like mine which is way out of production.  I was told to run the 2 Belles in parallel:  2 black speaker leads to the left common tap on the MC2125, and 2 red speaker leads to the left 16 ohm tap on the amp.  I have bridged the left and right 16 ohm taps on the amp, and set the switch to mono.  I have a feeling the autoformers on the McIntosh SS amps make combined loads not as critical as with others.  I did try the speakers in series, and did not really notice much of a difference.  Think I'll stick with what the manufacturer recommends.  This system is a combination of 2 systems I had, with pieces I have accumulated over the years.  So it is overkill.  But the room can handle it.  I would like to include a picture, but would need a kind of panoramic shot because the wall the equipment in on is 30+ feet wide.  Kid's playroom over the garage turned into man cave...

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I have 2 Belles to use.  The speakers are on either side of a 4 foot wide component rack, so I am uncertain as to how much comb filtering effect there is.  I have an amplifier which can handle the load of the 2 speakers.  My understanding is that PWK designed the Belles as center channel speakers.  My listening room is large enough to handle Klipschorns in the corners and Belles as centers.  And, to my ears, the Belles, when played by themselves, place the sound in the center of the component rack, in the center of the room.  

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On ‎11‎/‎29‎/‎2017 at 10:19 PM, luddite said:

The system sounds OK as I have it, but I notice the output for the MC 2125 is much less than what I see for the MC 7270 when I crank things up.  I'd rather not cook the system...

 

Just to clarify are you talking about the output power level of the 2 amplifiers or the sound level output of the center Belles versus the Klipschorns?

 

 

miketn

 

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4 hours ago, luddite said:

I have 2 Belles to use.  The speakers are on either side of a 4 foot wide component rack, so I am uncertain as to how much comb filtering effect there is.  I have an amplifier which can handle the load of the 2 speakers.  My understanding is that PWK designed the Belles as center channel speakers.  My listening room is large enough to handle Klipschorns in the corners and Belles as centers.  And, to my ears, the Belles, when played by themselves, place the sound in the center of the component rack, in the center of the room.

 

I have run 2 Belles placed very similar to how you have described between Klipschorns and it can sound extremely close to using a single Belle for a center which I also have done.

 

The 2 Belles comb filtering issue was never an audible problem in my situation and I wouldn't hesitate to recommend it as a valid option when a single speaker can't be placed in the center of the flanking loudspeakers.

 

Comb filtering is something to be aware of and is always a part of any reproduction system in a room even if it is mono but it depends on the situation if or how audible of an issue it is.

 

miketn

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On ‎11‎/‎30‎/‎2017 at 4:39 AM, WMcD said:

Anyway, to me it seems kludgy to run the two channels of the amps in parallel and the two speakers in parallel.

 

So, I'd suggest just hooking up the respective amp channels to the speakers using the 4 ohm and ground taps on each channel. I.e. not trying to create a mono-block.   And use the 4 ohm taps for driving the K-horns too.  Then drive the center amps with a Y connector from the center channel output of the pre-amp.   The amps should be happy.

 

+1......... but I would suggest trying both 4 ohm and 8 ohm taps since each will create a slight difference in tonal balance from the loudspeakers and depending on your system components synergy and room acoustics you might prefer one over the other

 

miketn

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Thanks to all for the insights and recommendations.  Just to muddy the water even further, I received a follow up email from McIntosh today.  It seems they now recommend using the Belles hooked up in parallel to the 8 ohm tap of the MC2125 in mono mode.  When the amp is bridged to mono mode, the 16 ohm taps become 8 ohm, the 8 ohm taps become 4 ohm, etc  .  When I have 2-8 ohm speakers in parallel (the Belles), the load is 4 ohms.  So I would connect the speakers in parallel to the 8 ohm tap.  Or so McIntosh says.  Single speaker to each channel in stereo mode with the center channel input on a "Y" cord to left and right channel inputs does appear a simpler solution.  8 ohm VS 4 ohm taps for the Belles and Khorns sounds more like personal preference.  Just gives me more things to sample.  At this point I will keep the 2 center channel speakers.  I can always go to a single Belle if I ever get tired of the sound of the pair of centers.  

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