Axiom Home Page Forums General Discussion Home Theater Onkyo receiver NR900

Hello, I'm new to the HT market, so I jumped in and bought the M80's, QS-8's, and the VP-100 (returning for the 150) and the Onkyo NR900. The speakers sound great, and the receiver seems to work great, but I'm not sure if it's enough power. It's rated at 110w/ch at 8Ohms, it goes down to 4 ohms at 145w/ch (current setting is 4 ohm).
I can turn the receiver up and the speakers are clear and clean, but they don't seem loud enough. I just don't think that I should be able to turn the receiver all the way up and stand it. This is a first for me, are the speakers just so clear that I can turn them up and enjoy the music.

Also, I know that the M80's are rated up tp 400w, is underpowering them going to hurt them?

Thanks,

Rick

Rick, I can't comment directly to your situation because i'm not familiar with your receiver, but the receiver i have, the Onkyo DS797, is rated for 100w over 6 channels (this is Onkyo's listing) and i have to turn my receiver up to 70-75% to get the maximum loudness i would prefer.
In fact, i know that several other ppl on the forums have the same receiver and also commented on how any volume setting less than 45% using this Onkyo was really quite useless since you couldn't hear anything at all.
I wasn't sure originally if this was an underpowered situation when i first tested my speakers but now i know, it was not. It just happens to be the way the receiver works and pushes power.
I should also note, i cannot put my volume above the 82% mark on the Onkyo b/c the sound physically becomes painful.

Quite a few people find they need to turn up the volume on their receivers well past the magical 50% level for movie watching. Just turn up the gain until you're satisfied...your ears will let you know if there's a problem.

Underpowering speakers is the biggest risk of causing damage, but a well-built SS amp shouldn't have a problem with the M80s.

Hi Ralderman,

If you can turn the Onkyo's volume control all the way up, I suspect the NR900 has a current-limiting protection circuit that's limiting the output power available to 4-ohm loads. The M80ti's are 4-ohm speakers and many multi-channel HT receivers have protection circuitry to reduce power output into 4 ohms so the output transistors don't overheat or get damaged with the increased current flow.

The M80's are the most sensitive speaker in the Axiom line and will play very loud on comparatively few watts. A conventional stereo amp with a robust output section and plenty of heatsinking (to dissipate heat) would normally drive the M80s to extremely high volume levels--either your ears would give out or the speaker would reach its output limits (likely the former). Onkyos tend to have aggressive protection circuitry that greatly reduces output into 4-ohm loads.

It's unfortunate that the power output ratings of multichannel receivers are so misleading and no longer monitored by the Federal Trade Commission (FTC). The power output of most HT receivers is almost always rated with one channel driven (not five) into an 8-0hm load and more often than not at a single frequency, usually 1 kHz. Only a few very expensive top-of the line models that are huge and heavy (Denon, etc) will actually approach their rated output with all channels driven.

Regards,

Hey guys,

I have the Onkyo TX-DS787 (the precursor) to the 797, do you think this thing has the juice to run the M80's in a home theatre setup? I had thought that originally it wouldn't be able to run 4 ohms speakers, but just wondering if anyone here is running an 787 with the M80's? If so, I may have to try out Marc's trade up specials with my M50's.

ralderman, you said that your receiver is set to 4 ohms. Is that a switch somewhere? I would try setting it on 8 ohms. You should get some better dynamics which could translate into increased "loudness" for any given volume level.

I just realized I think you said you have the receiver turned all the way up. That surprises me for the Onkyo. Sounds like something isn't working right.

Also, when talking about volume settings, I don't think that "50%" - or any percentage - really means anything.
For example, my Denon 1803 has a volume range from "-80dB" to "+18dB." That's a 98 increment difference. I listen at a minimum of about "-30dB" or else it's too quiet. So I guess that puts me at over "50%" of the way up the scale.
My friend's Sony ES receiver, on the other hand, doesn't have this representaion, it only has the knob's marking for reference. His receiver never goes much above "33%" on the dial, or else it's too loud.

You might want to consider using an external amp with your M80s. Either the IRD Audio MB-100 monoblocks or the Outlaw Audio M-Blocks would be a perfect companion for the M80s (neither would have a problem w/ the 4ohm load) and both are relatively inexpensive at $500/pair. Another option would be using a reciever with a more robust amplifier section like the Nad T762 which is in the same price range as the Onkyo NR900.

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ralderman, you said that your receiver is set to 4 ohms. Is that a switch somewhere? I would try setting it on 8 ohms. You should get some better dynamics which could translate into increased "loudness" for any given volume level.

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Receivers with said switch, in my experience, use this to determine the power safety circuitry. Were you to switch it to 8ohms, the system would detect a power draw that is too high and trip the circuit breaker.

Thanks to all for your info, I normally listen to regular TV arount 45 - 50 percent, movies are around 70+. (Until my wife tells me it's too loud.) It get's very loud, I just didn't think I should be able to do that. If I switched to 8ohm on the receiver, would that damage the speakers. If anyone has links on info explaining ohms, and speakers and watts I would like to read. I understand slightly, just not completly.

The switch to 4 ohms was in the setup program, no a physical switch.


Rick

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If I switched to 8ohm on the receiver, would that damage the speakers.

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Shouldn't. It should just turn off the receiver, assuming good fault protection.

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If anyone has links on info explaining ohms, and speakers and watts I would like to read. I understand slightly, just not completly.

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Electrical Engineering 101 (VERY simplified):

An Ohm is a rating of resistance. You could sort of think of it like weight. The higher the weight, the harder you have to push to move it. Voltage, rated in Volts, is the electrical potential on both sides of the load (rated in Ohms). Current, is kind of like how much water moves through a stream. I know I'm mixing my metaphors, but I'm trying to leave the office.

Ohms law:

Voltage = Current * Resistance.

Watts are the unit of measurement for the amount of power something has. Power is calculated by multiplying the voltage potential by the current.

What does this mean to you?

The wattage spec'ed by a receiver is theoretically how much power it's capable of putting out. The more power, the louder your speaker will go, in general (how sensitive it is to that power plays a big part in how loud it actually gets). The wattage rating on a speaker is the maximum amount of power it can take. So long as the speaker can take enough and your receiver can put out enough power that you're never near the maximum of both, you won't have any trouble. If you hit the maximum power output of the receiver, it will no longer be able to correctly amplify the signal, sending some very dangerous and very ugly signals to your speakers. We call this clipping. If you try to force too much power through a speaker that can't take it, you'll fry the poor little components of the speaker.

What the resistance means to you:

Using the equations I mentioned before, the lower the resistance, the more current it will draw.

If V=I*R, and P=V*I, P=I^2/R

Therefore, at a given current, the increase in power is proportional to the decrease in resistance.

All this means that a receiver should be able to put out more juice to a speaker with a lower resistance rating. In reality, you run into the capabilities of the amplifier and you can draw too much power, hence the fault circuitry you're looking at.

If you want more detailed info, I suggest you pick up an introductory circuits book and laugh at my gross over simplification.

Regards,
Semi

Rick, try the 8 ohm setting. It may well be that the M80s won't draw enough current to cause a problem, even though they have a 4 ohm rating. If they do, and the receiver shuts off, return the setting to 4 ohms. At least try removing the restriction.

Forgot that we're talking about the NR900. Should have said to try the 6 ohm setting.

Duffin, the 'percentage' of the volume i was referring to might be specific to some receivers.
My Onkyo has 2 settings for volume, one of which is called 'absolute' which uses a 1 to 100 scale (or basically percentage) and the other which also uses the dB scale as you mention. I use the percentage scale b/c i find the dB scale a bit odd. The percentage is a bit more universal for ppl to understand.