NHT Power5 can't handle 4 ohms? - AVS Forum | Home Theater Discussions And Reviews

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post #1 of 7 Old 02-07-2012, 04:35 PM - Thread Starter
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Three channels on my NHT power5 started cutting out (going into protection mode) at reasonably high volumes. It will come back on after lowering volume. I am powering Salk HT2-TL's which are 4 ohms.

I called NHT and they told me that the power5 should not be used to power 4 ohm speakers, and I was lucky it has worked this long (I have been using it with these speakers for almost 4 years) He said that the amp should be fine since it works at lower volumes, but I should sell it or use 8 ohm speakers.

I seem to remember researching this amp and reading on this forum that the power5 should put out around 500wpc at 4 ohms. I also remember people telling me it would be a good match with my speakers.

Does it make sense that it would handle it for 4 years and then decide not to?

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post #2 of 7 Old 02-07-2012, 05:50 PM
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IMO, if it worked perfectly until now, and nothing obvious has changed, then the amp is not working as well as it used to.

"But this one goes up to 11"
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post #3 of 7 Old 02-07-2012, 08:30 PM
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If I am not mistaken, that amp is an older design class d. Those in general did not do well with 4 ohm loads.
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post #4 of 7 Old 02-09-2012, 08:21 AM
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I have the NHT Power5 and also experienced channel 1 cutting out intermittantly. I run Snell XA60's which are 4 ohm speakers but the channel dropped out without respect to high volume. I sent the amp in for service and they replaced the channel but after a few days it did the same drop on the same channel. Others on the NHTPower5 have had this same problem. I don't believe for a second it has to do with 4 ohm speakers. I've simply avoided that channel and haven't had the issue with any other channel. There must be an issue with the output as opposed to the channel itself. Very disappointed with NHT's support of this.
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post #5 of 7 Old 02-09-2012, 08:38 AM
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It is too bad that so many are having issues with their NHT amps. I have to be honest and admit I'm glad I sold my Power5 when I did. It is a great amp but certainly not good enough to put up with the reliability issues. So many great multichannel amps available that will offer just as good SQ with much better reliability IMO.

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post #6 of 7 Old 02-09-2012, 10:48 AM
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Quote:
Originally Posted by rnatalli View Post

If I am not mistaken, that amp is an older design class d. Those in general did not do well with 4 ohm loads.

Yeah it uses ICEpower, but IIRC it uses a power/slave configuration so each channel doesn't have it's own power supply. I think there's two 500ASP modules powering three 500AS modules. (The ICEpower "ASP" module uses a Switch Mode Power Supply, so each one is a mono-block. The "AS" modules have no power supply and must use that of the ASP or an external one.)

I know the 500ASP modules can easliy handle 4ohm loads and actually are stable down to 2ohms on their own, but I guess running slaves changes things considerably. One of the ASP's would have to power three channels total in that configuration.

If it were me, I'd try to figure out which channels are fed directly by the ASP modules and put my mains on those to see if that makes a difference.

It should be simple enough if you can find a schematic, or open it up and look for which speaker outputs / line inputs bypass the three AS modules and connect directly to the two larger ASP modules in the front.
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post #7 of 7 Old 02-09-2012, 10:54 AM
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I should have added that the original design concept for the ICE modules in a master (ASP)/slave (AS) configuration was for bi & tri amped powered speaker set ups. So each module would share a portion of one speakers' workload, with the ASP module handling the bass drivers.
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