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#204978 - 04/21/08 03:00 PM M80v2 with NAD bridged amps
ClayB Offline
buff

Registered: 04/19/08
Posts: 40
Loc: Minneapolis,MN USA
Hi All,

I ordered a set of M80s last week, after weeks of research and pondering to replace a set of JBL Northridge E100s in my 2-channel setup.

Here's my question:
I use a pair of NAD amps (C370 and C270) in BRIDGED MODE to drive my speakers (300 watt/ch). However, the nature of bridged mode halves the impedance that each amp 'sees', and with the M80, that becomes a very hungry 2-ohm load. My real question is, are the M80 truly 4 ohm loads, and has anyone else done this? The NAD manual recommends against it, saying that the thermal switches might trip at high listening levels.

I'm not sure what to do when the M80s arrive. Super-Don in tech support is asking Ian and Alan, but I wanted to see if the user community has any real-world experience. I can't be the first person to run into this...

Regards to all,

Clay - Minneapolis

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#204983 - 04/21/08 03:29 PM Re: M80v2 with NAD bridged amps [Re: ClayB]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13337
Loc: Iowa
Hey Clay,

Can't provide any input on bridging amps. All I can say is my Odyssey monoblocks drive my 80's to sonic bliss. In fact, the 80's are very efficient and easy to drive, most AVR's by themselves will impress.

No speaker is just ONE ohm rating across the frequency range, it varies. The 80's do not dip below 4 ohms across the freq range, I can tell you that much.
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#204995 - 04/21/08 04:10 PM Re: M80v2 with NAD bridged amps [Re: SirQuack]
ClayB Offline
buff

Registered: 04/19/08
Posts: 40
Loc: Minneapolis,MN USA
I know that EITHER one of the amps by itself will be perfectly fine with the 4-ohm load. NADs are capable of delivering huge amounts of current. Its the nature on bridging that creates the problem.

I'll start out by un-bridging the amps, using the 370 as pre-amp only, and drive the M80s with the 270 only. 'Only' in this case a 120w/ch, so I should be OK.

If anyone has any experience with bridging, I'd be interested to hear it. Alan has chimed in and recommended following NADs advice, and not to bridge due to the 4-ohm load.

In any case I'm eager to get the speakers and have a go. I ordered them on Thursday and got the shipping email on Friday, and am waiting for them to show up on the DHL tracking site! I assume Axiom uses a freight forwarder in Canada to get them to the USA, where DHL takes over. That would explain the two day delay in the tracking numbers showing up. When I get other international shipments from DHL, I can track them all the way in.

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#204996 - 04/21/08 04:15 PM Re: M80v2 with NAD bridged amps [Re: SirQuack]
ClayB Offline
buff

Registered: 04/19/08
Posts: 40
Loc: Minneapolis,MN USA
PS - Odyssey Monoblocks, eh?? nice!

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#205008 - 04/21/08 04:48 PM Re: M80v2 with NAD bridged amps [Re: ClayB]
jakewash Offline
shareholder in the making

Registered: 12/26/03
Posts: 10398
Loc: Calgary, Alberta
For the States, the speakers would go directly to Fed Ex, then down or Purolator to DHL then down to the states.
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#205009 - 04/21/08 04:51 PM Re: M80v2 with NAD bridged amps [Re: jakewash]
ClayB Offline
buff

Registered: 04/19/08
Posts: 40
Loc: Minneapolis,MN USA
Thanks Jason. My email said DHL so I assume they will be bringing them to the door. Just not sure how much advance warning I'll get re the expected delivery date; I travel often and would like to plan my travel around that day!

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#205012 - 04/21/08 05:03 PM Re: M80v2 with NAD bridged amps [Re: ClayB]
jakewash Offline
shareholder in the making

Registered: 12/26/03
Posts: 10398
Loc: Calgary, Alberta
If they don't get held up too long in customs I would bet you get them in 2-4 days.
_________________________
Jason
-----------------
TTTHHHPPPPPTTTT!

My HT

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#205047 - 04/21/08 10:57 PM Re: M80v2 with NAD bridged amps [Re: ClayB]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10395
Clay, welcome. You shouldn't need to bridge your NADs to have plenty of power for the M80s, which are slightly above average in sensitivity and are by no means "power hungry", to use the term that's sometimes used without any thought behind it.

Incidentally, on bridging, although the language about the amplifier "seeing" an impedance cut is half is seen fairly often, it's technically incorrect. The windings in the speaker drivers establish the impedance of speakers and can't of course be changed by the amplifier. What's actually happening is that when bridged the amplifier is theoretically delivering twice the voltage into the speaker. Due to to Ohm's Law(I=E/R), current(I)is proportional to voltage(E)and when the voltage is doubled the current is also doubled, as it would also be if the impedance(R)was cut in half.
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#205061 - 04/22/08 02:54 AM Re: M80v2 with NAD bridged amps [Re: JohnK]
Haoleb Offline
connoisseur

Registered: 09/25/02
Posts: 1488
Loc: Maine
Having had a C370 powering my M80's at one time I can assure you that it will drive them well enough on its own. If you want even MORE power instead of bridging the amps and using them as mono blocks you can biamp instead using say the C370 for the mids and tweeter drivers and the C270 on the woofers. Thanks to the second preamp output on the C370 you can do this. The amplifier sections are identical in both of those amplifiers as I am sure you are well aware.
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#205063 - 04/22/08 03:18 AM Re: M80v2 with NAD bridged amps [Re: Haoleb]
ClayB Offline
buff

Registered: 04/19/08
Posts: 40
Loc: Minneapolis,MN USA
Haoleb,
Thanks, that's a great point. I guess that an external crossover before the amps would be ideal in this case, but is actually not needed, I could remove the bi-jumpers and send the full spectrum signal to each set of drivers, and the let the internal networks do the work. Great tip!

I'm a big believer in the having power reserves to accurately deliver transients; its what makes music 'real' to me..

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