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fraid of hurtin em..


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Hi - been around Klipsch long b4 there was anything but the Heritage, fell in love with the openness of B&W's but ended up in a small home with a pair of RB35's 

These were bi-amped on an old classic Sansui QRX 6500 and sounded GREAT! BUT life goes on and furniture changes and The Sansui is setting in a shed. (sin)

Now the newest amp to power these RB35's is a Sony STR DH770 which is Bi-Ampable. BUT is rated at 145 per - RMS! (RB35's are rated for  125 - 500 peak)


Am I going to hurt the rb35s with the 145 per component (bi-amped) and if so what will I be hearing as they start to deteriorate?


Since I have bi-amped them I have come as close as I can to that sweet sound I got from the QRX 6500 - but that beast is not welcome in the house (size and looks per the wife - I know - nuther story..)

BUT the Sansui was only rated at 35 rms per (discrete) channel.. 


All you newbies to the field  :-) - give me you thoughts.. 


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Funny you ask questions of newbies :D but I'll give it a try.


Your speakers are moderately efficient and if you don't have a large room, you will likely start hearing the speaker sounding strident or hard (you'll know when you hear it).  When it gets that way, you will know it.  That's when it's time to turn it down.  Bi-amping should not matter much as you are still using the passive crossovers which should give adequate protection unless you push the receiver to beyond where it is comfortable (remember wattage is the ceiling and music is not constant so likely has 10db+ peaks depending on what you listen to requiring 4+ times the power).  That's where you will get in trouble due to:


The 145 watt per channel rating is with a really good  tail wind.... Amazon likes to state the peak power because it sells.  90 watts if lucky running 1 or to channelsl at 6 ohms puts the receiver at probably 65 watts into 8 ohms single channel.  If you try to bi-amp you'll likely end up with half that per channel so be careful with that receiver.  I've never seen a manufacturer's site not list wattage ratings, unless I missed it.

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you didn't miss it , I just spent an hr searching and I could not find the specs for watts rms @8 ohms /chn for that avr.

But , I do own the DH750 and run RF-280 based 5.2 surround with mains bi-amped to last surround channel. RF-280 spec  is 150rms/600peak so similar to yours.

I've play that setup in 2.2 and 5.2 as loud as I could take in a 12x13 room(and I love loud :) ) without an issue.

As pzannucci stated turn it up if you hear distortion back off.

Based on my experience with a similar setup just don't push it into distortion and you should be fine, I'll bet you get to the "ok that's loud enough " long before then.



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Fantastic! Glad to hear what you are both saying. I was looking at the specs on those RF-280's as replacements and noticed they were in the same ball park as the older models.

Some of my music choices can include soft passages (as in Chick Corea.. from Stanley Clark's bass solo to - OH MY GOD that was loud!!!) and i was worried about an old adage that dirty power is more damaging to speakers than high power. I think this Sony should be clean enough to not worry. 


Thanks guys!

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I doubt you will damage them, but remember, the volume control is like the accelerator on a car.  Your engine might have enough power to smoke the tires, but you can use the accelerator properly and prevent that.  If you hear brittleness or extra harshness, turn it down until you don't. 

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Looking at the specs and price point of the Sony, I would be more concerned with under powering them than over powering.  IMO, not the best choice to drive a nice pair of speakers like the RB-35's.

4 hours ago, benaround said:

i was worried about an old adage that dirty power is more damaging to speakers than high power. I think this Sony should be clean enough to not worry. 

I really doubt the Sony will provide "clean" power once you twist the knob a bit.  I have not heard this AVR but non ES Sony AVR's are not the choice of most on this forum. 

I am not a brand snob but Sony is not an AVR brand that is on my "got to have" list.



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Thanks Bill, Yea I have heard that 37 watts RMS  in 1975 is a complete different value today. Never did get a grip on if possible or how to compare the values from different ereas.

I remember when some unsavory marketing was being allowed to boast of ridiculous power ratings at stupidly low prices. Started around the time Pyle was brought to the market.

I can say with confidence that the Sansui sounds as good if not better at 37 watts RMS into 8 Ohms as the so called 145 watts RMS into 6 OHMS (factory rating) of the Sony.

Some day I hope to at least get back to the NAD or Denon level of quality.

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The NAD level should be a worthy goal.  Or, for Home Theater, Denon or Marantz, to get Audyssey.


Sounds like you have a small room.  Is it live or dead or typical?  With your speakers, you will get THX/Dolby cinema Reference level peaks of 105 dB at 13 feet, in a 3,000 cu.ft.room with a good and true and honest 32 watts.  More about that later ... 


Don't turn up the bass control very much -- the bass capacity of the  RB35s is not very deep.  This is true of almost all bookshelf speakers.   If you were to turn up the bass too far, and there was loud bass below the - 3 dB point of the speakers (F3), there could be a problem.  It looks like that point may be just below 45 Hz on your speakers. 


2 hours ago, benaround said:

Never did get a grip on if possible or how to compare the values from different ereas.


Well, ratings were relatively honest in the '50s and early '60s, certainly with McIntosh, Marantz, Leak, Harman Kardon, H. H. Scott, Fisher, Dynaco etc.  Even Eico and Heathkit were probably O.K., although they might label their ratings something like, "18 watts, 12 watts Professionally Rated."   I've heard Arkay was not O.K. that way, because their 12 watt amp was more like 9 watts.  Then power hit the fan.  A 30 w.p.c. amp became a 60 watt amp [because it had two channels, and they added to 60!].  Pretty soon the same amp became, maybe, 80 watts, [because both channels, added together,  could peak there for some milliseconds].   Finally, the Federal Trade Commission stepped in and scotched the snake of outrageous power claims.  Meanwhile, to make matters worse, some manufacturers piled on negative feedback, so they could advertise 0.0001% distortion -- but the amps sounded harsh and pretty terrible.  Then Dr. Otala discovered Transient Intermodulation Distortion (TIM), which increased with negative feedback, so that some amps that had higher THD, actually sounded better, by virtue of the TIM being lower!  Paul Klipsch celebrated by urging that the new kind of distortion be called Otala distortion, to give credit where credit is due, but nobody paid attention.   IMO, there is no safe way to compare values from different eras, to get good and true and honest ratings other than insisting on knowing the continuous power per channel, all channels operating [to properly stress the power supply], but measured separately, so what you are getting is w.p.c., 20 to 20K Hz, into 8 Ohms, at some low level of THD, like .08% or below.  Unfortunately, they won't be giving you the TIM, but most amp makers have eschewed piling on negative feedback.  About the only way to get power with all channels operating is to find a review in some magazine for which they did a Bench Test.  Unfortunately, many online "reviewers" simply reprint the manufacturers' misstated specs.   About a decade ago, it was suggested that 80% of the continuous power rating with 2 channels operating, would equal a realistic figure for 5 channels operating.  But who knows?  Maybe things are now worse!

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  • 2 weeks later...

From the owner's manual for the STR-DH770:
Minimum RMS Stereo Output Power = 90 watts per channel (6 ohms, 20 Hz – 20 kHz, THD 0.09%)


That is likely around 70-80 watts per channel RMS at 8 ohms.  This is stereo of course.  If you are running a full 7 channel surround sound setup this thing's power supply might only be capable of 30 or 40 watts per channel concurrently.  I've seen independent testing of a 2011 Sony model that was rated for 100 watts per channel RMS in stereo, 8 Ω, 20 hZ - 20 kHz, 0.09% THD and when driving all seven channels at once it could muster all of 55.3 watts per channel at 8 Ω and 0.1% THD.

Edited by blue72
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