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#283053 - 12/19/09 04:13 AM ROTEL RECEIVER not RATED FOR 4 Ohm?,
Captain4105 Offline
veteran

Registered: 01/11/09
Posts: 133
Loc: Southern California
I read a review today indicating that the new Rotel 1550 AVR is rated at 75 watts per channel into 8 ohms. The review goes on to say that the receiver is not rated for 4 ohm use. Does this mean that its OK to use this receiver with 4 ohm speakers but the receiver wasn't tested for them and thus is still unrated? I believe that this receiver is capable of driving M80's. What is your opnion? See http://www.rotel.com/content/reviews/15%20series/rsx1550-equip_rotel_cm.pdf Thanks...Lee

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#283057 - 12/19/09 09:55 AM Re: ROTEL RECEIVER not RATED FOR 4 Ohm?, [Re: Captain4105]
RickF Offline
axiomite

Registered: 02/26/05
Posts: 5210
Loc: Vero Beach, Florida
Lee, everything I've read suggest that yes you can drive the 4 ohm 80s with the 1550 without any problems and I personally believe there should not be any issues but you may want to ask the question over on the Club Rotel forums...

Club Rotel

This looks like a very nice AVR, I like it!
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Our Room

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#283058 - 12/19/09 10:05 AM Re: ROTEL RECEIVER not RATED FOR 4 Ohm?, [Re: RickF]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6789
Loc: The Peoples Republic of Il.

No where in the manual of the RB1080 does it say it's rated at 4 ohm but it sure does a nice job with the 80s. I'm sure the 1550 will work fine.
_________________________
Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud


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#283122 - 12/19/09 09:32 PM Re: ROTEL RECEIVER not RATED FOR 4 Ohm?, [Re: Captain4105]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10621
Lee, the reason that the 1550 and so many other receivers that can handle 4 ohm rated speakers with no problem in real-world home use can't claim an "official" 4 ohm rating is the severity of the tests they would have to pass. The FTC(Federal Trade Commission)has regulations for amplifier power ratings which have to be followed for any units sold in the U.S(and which, as a practical matter, are the same as those sold in Canada), and the UL(Underwriters Laboratory)tests for overheating. In brief, for an official 4 ohm rating the unit would have to be operated at the full rated power for at least five continuous minutes into a 4 ohm load. Most units aren't designed for such an ordeal without overheating and having their protective circuits shut them down.

Nevertheless, for actual home use the 1550 and many other receivers are serving their owners well driving speakers, including the M80s, which are rated at 4 ohms. Incidentally, you might also note that the M80s are 8 ohm speakers over the majority of their frequency range.
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#283129 - 12/19/09 10:18 PM Re: ROTEL RECEIVER not RATED FOR 4 Ohm?, [Re: JohnK]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6789
Loc: The Peoples Republic of Il.

That's not what I see when looking at the M80 impedance graph John. While a majority of the graph shows the M80s above their 4 ohm rating it certainly does not show them to be "8 ohm speakers over the majority of their frequency range".
_________________________
Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud


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#283177 - 12/20/09 12:35 PM Re: ROTEL RECEIVER not RATED FOR 4 Ohm?, [Re: Wid]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13565
Loc: Iowa
Here is the graph for reference. Looks like it is 8ohm or above from around 700hz - 2K, and 5K to 20K Hz.


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#283179 - 12/20/09 12:47 PM Re: ROTEL RECEIVER not RATED FOR 4 Ohm?, [Re: SirQuack]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6789
Loc: The Peoples Republic of Il.

Yes it is from 700hz - 2K but it is not up to 20K, it shows it from 5k to around 12k. Put a straight edge on the graph and it will show it. The point being it does not show the 80s as being "8 ohm speakers over the majority of their frequency range".
_________________________
Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud


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#283181 - 12/20/09 01:04 PM Re: ROTEL RECEIVER not RATED FOR 4 Ohm?, [Re: Wid]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13565
Loc: Iowa
Which is why I showed the graph, to confirm your statement. Didn't take the time to use a straight edge, to lazy.
_________________________
M80s-VP180-4xM22ow-4xM3ic-EP600-2xEP350
Anthem AVM60 Outlaw 7700 Emotiva A500 Epson 5040UB



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#283183 - 12/20/09 01:07 PM Re: ROTEL RECEIVER not RATED FOR 4 Ohm?, [Re: SirQuack]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6789
Loc: The Peoples Republic of Il.

Got ya.
_________________________
Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud


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#283226 - 12/20/09 09:36 PM Re: ROTEL RECEIVER not RATED FOR 4 Ohm?, [Re: Wid]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10621
Speakers are rated on an average of their impedances, not the minimum. The NRC graph does in fact show that the M80s are 8 ohm speakers over the majority of their frequency range.
_________________________
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Enjoy the music, not the equipment.



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