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Thread: B&W |
    
New member Username: Dikkelu
Post Number: 1
Registered: Aug-09
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| Posted on Saturday, August 29, 2009 - 03:51 pm: |
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hi, I bought some B&W speakers CM7, now I have a Yamaha 2x70W amplifier. Which amplifier fits best with the CM7 series ? I heard about NAD and Arcam. Which output fits best ? The CM7 series is 30-150W. I do like some rock and jazz music with bass. |
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Platinum Member Username: Nuck
Post Number: 13308
Registered: Dec-04
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| Posted on Saturday, August 29, 2009 - 05:10 pm: |
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Rotel comes to mind, but others may vary with those speakers.
Ignore wattage #'s, they mean nothing. |
Gold Member Username: Dmitchell
Ottawa,
Ontario
Canada
Post Number: 2949
Registered: Feb-07
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| Posted on Sunday, August 30, 2009 - 08:19 am: |
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Those are reasonably easy speakers to drive. All the brands you mention would be just fine. A local audioshop here in Ottawa pairs them with Rotel quite often, but I'm not a fan of the combination, even though I do like Rotel. |
Platinum Member Username: Nuck
Post Number: 13314
Registered: Dec-04
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| Posted on Sunday, August 30, 2009 - 11:15 am: |
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Stryvn here has a nice Rotel pre/power for sale... |
Silver Member Username: Edison
Glendale,
CA
US
Post Number: 908
Registered: Dec-03
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| Posted on Tuesday, September 01, 2009 - 06:34 am: |
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I listen to the audiosource power amp 300 - it has toroidal power supply, and quite a bit of power.
I like it better than the NAD monitor series amp I have.
Audiosource is affordable and good. They have a pre amp as well. You can get them on ebay for a good price.
When you buy anything on ebay, as you must know, one has to be careful - check the seller's rating, and make sure you are getting a working one. |
Gold Member Username: Nickelbut10
Post Number: 2741
Registered: Jun-07
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| Posted on Tuesday, September 01, 2009 - 10:45 pm: |
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if you want audiosource products from a dealer, they can be had from www.partsexpress.com
They are owned by Pheonix Gold the famous car audio amplifier manufacturer.
FWIW |
Gold Member Username: Frank_abela
Berkshire
UK
Post Number: 3798
Registered: Sep-04
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| Posted on Thursday, September 03, 2009 - 10:18 am: |
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Although the numbers indicate that the speakers should be easy to drive, I've found that they seem to have a weird impedance load, causing trouble to even quite nominally powerful amplifiers. I did find that the Arcam A28 drove them very well indeed, but that the Naim SuperNait (some 2.5 times more expensive and nominally more powerful) couldn't drive them as well. So you do need to partner the amplifier carefully. |
Gold Member Username: Dmitchell
Ottawa,
Ontario
Canada
Post Number: 2980
Registered: Feb-07
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| Posted on Thursday, September 03, 2009 - 05:30 pm: |
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Interesting Frank. I had no idea. |
Platinum Member Username: Nuck
Post Number: 13337
Registered: Dec-04
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| Posted on Thursday, September 03, 2009 - 09:25 pm: |
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Some things don't go so well together that way. Sigh.
Did you sell the Mani 2's yet frank? |
Silver Member Username: Magfan
USA
Post Number: 499
Registered: Oct-07
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| Posted on Friday, September 04, 2009 - 03:34 am: |
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Frank, if the speakers are indeed a 'weird load' as you indicate, the problem may be phase angle, in combination with a low impedance dip.
IMO, Power Factor is the biggest 'killer' of amps out there. An amp may have a high enough power rating for a given speaker, but be unable to deliver the goods when presented with a largely reactive load... be that capacitive or inductive. |
Platinum Member Username: Nuck
Post Number: 13348
Registered: Dec-04
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| Posted on Friday, September 04, 2009 - 08:07 pm: |
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Output transformers should negate the back EMF of an capacitive load, or so my thinking went.
Speakers in question had a broad 65 phase shift, but not in such an abrupt range.
On paper, it didn't look toooo bad...
Huh. |
Gold Member Username: Frank_abela
Berkshire
UK
Post Number: 3801
Registered: Sep-04
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| Posted on Saturday, September 05, 2009 - 09:25 pm: |
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Nuck,
No I haven't. Not only that, I haven't even had any enquiries...
Frank. |
Silver Member Username: Magfan
USA
Post Number: 500
Registered: Oct-07
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| Posted on Saturday, September 05, 2009 - 11:34 pm: |
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Nuck,
Do I read 65 degrees correctly?
If so, that is a pretty big phase angle at which time an amp will only be good for a fraction of its rated resistive output.
If, in the same frequency range, there is a nice dip in impedance, you are cooked.
That is why the top name amps (fill in blank) are worth it. Also, what got me going down this path was the original statement by Jan that 'speaker builders and amp designers don't talk.'...
Very true, if some speaker load measurements are to be believed.
From the industrial end of things, a factory with too low a power factor can incur an electric bill surcharge. This can kick in for what in speaker design is an almost unavoidable .85 to .9 |
Silver Member Username: Magfan
USA
Post Number: 501
Registered: Oct-07
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| Posted on Sunday, September 06, 2009 - 05:29 am: |
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The Math part:
65 degrees is a PF of about .423 which means that if you want 100 watts to the speaker, you will need an amp which kicks out about 237VA, at that frequency.
When asking for dynamic peaks, as you can see, it'll get worse fast.
I'm not saying the data isn't there, but I've not seen amp data working into anything but a resistive load.
I also figger that all amps are not equal in there ability to power hi phase angle loads. Better is better, of course. I also don't know what effect the transformer has on vacuum tube equipments ability to drive such loads.
More questions than answers, but the basic idea is there. |
Platinum Member Username: Nuck
Post Number: 13354
Registered: Dec-04
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| Posted on Sunday, September 06, 2009 - 08:17 am: |
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You got the right figures, Leo!
I was referring to the 200wpc SS Mac6900 specifically, with it's transformers. |
