# Can someone explain this about amp wattage?



## enrique (May 24, 2007)

I've always heard that more watts is always better,yet some use lower wattage amps to drive their speakers.what i mean is say someone like myself who has a rotel rsx1056 receiver and wants to add a 2 channel amp for the front 2 do i need an amp thats twice the rec. wattage.i mean do i need a 200 watt amp as opposed to a 100 watt amp.I've been reearching as much as possible since i plan to get a class d amp(low profile & cool running).But because of cost would the 100 watt amp be as good as a 200 watt amp.I'm not one for playing at extreme levels for either music or HT.Freeing up stress on my receiver is my first reguirement,and adding an amp for the front 2 or 3 i'm assuming would do this to keep my rec. from stressing out in the long run due to 4ohm speakers all around.


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## Otto (May 18, 2006)

*Re: can someone explain tis about amp wattge?*

Hi rick,

Generally, what you need is an amplifier that's able to supply the amount of power that you need, and that has some headroom above and beyond that for dynamics. This depends on your listening habits and your speakers' sensitivity, among other things.

Is your receiver able to handle a 4 ohm load at all? It may be if you are playing at reasonable volumes. I generally understand about impedance matching, and the power requirements of driving low impedance loads with an amp that's generally not specified for them. Now, that said, I really don't think twice about hooking up a 4 ohm load to a receiver if it's going to be played at reasonable volumes. For example, I run my "Zone 2" with two sets of speakers wired in parallel, yielding a 4 ohm load. No problems. Man, when I was a kid and had no idea, I ran something like four pairs of _car speakers_ in parallel using a Technics receiver. Now that guy would get hot and shut down at high volumes, but again, no problems at low volumes. So use your best judgment there...

I believe that 100 W amp will be enough for most listening sessions, even at somewhat high volumes. Unless you are getting into some seriously demanding speakers, 200 W is probably overkill (Indeed, I'm using 400 W per speaker (bi-amped) right now, and yes, it's overkill). 

Tell us, what speakers are you using? You indicate that you aren't really interested into getting it too loud. What does that mean, really? How much power do you currently have in your receiver, and what receiver is it?

Good luck.


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## enrique (May 24, 2007)

*Re: can someone explain tis about amp wattge?*

thanks,my receiver is a rotel rsx1056,speakers are sytem audios.Mains are SA1750(90db 4-8ohm)center sa720av(89db 4-8 ohm),surrounds sa505's(88db 8ohm).Just for reference i had also calibrated with spl meter and my mains and centr i'm able to get to 75db but the surrounds i cannot.I have them set to max and still no 75db on the surrounds.Had to go down to 72db for all speakers to be equvalent.I'm assuming this is because my rec. driving the fronts and not enough for the surrounds.And if i get the amp i would assume since the amp would drive my front 2 or 3 it would free up the rec. driving the surrounds and i would then be able to calibrate 75db all around.does this make sense?


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## Otto (May 18, 2006)

*Re: can someone explain tis about amp wattge?*

Oops, sorry -- I did read that you had the Rotel in your original post, but forgot it in my response. Will think about it and post later.


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## Otto (May 18, 2006)

*Re: can someone explain this about amp wattge?*

OK. So your receiver is a healthy 75 WPC. I do believe that it should be sufficient for you to get to reasonable listening levels. Your surrounds are spec'd at 2 dB lower than your mains, and 1 dB lower than your center. Also, your mains are rated at 4-8 ohms, from what you have posted, and your surrounds at 8 ohms. I understand that the impedance of a speaker will fluctuate over the frequency spectrum, but speakers are usually spec'd at a certain impedance. It's also interesting that the speaker manufacturer has chosen to spec some of its speakers over an impedance range (e.g., 4 to 8 ohms) and some at a specific impedance (e.g., 8 ohms). Anyway, the sensitivities of the speakers do not constitute a large disparity, in my opinion. I'm not sure what to think of the difference in impdeance specifications. 

It sounds like you are having trouble calibrating the five speakers -- you can't get them to perform at the same relative level during set up tests. I think that you should be able to get them pretty close. Let me ask -- how are you calibrating them? What tone/noise source are you using? What SPL meter are you using? In what mode are you using the SPL meter (e.g., "A" weighted, "C" weighted, "fast" or "slow" mode, etc.?). Are your surround speakers very far from the testing/listening position when doing measurements? What "mode" is the receiver in when doing the measurements (e.g., "stereo", "Dolby Digital", some other processing mode, etc.).

When I do this, I generally start with my "trim" level for my mains at 0 dB and turn up the volume until I read 75 dB on my SPL meter. Note that the 75 dB reading is somewhat arbitrary; it's a commonly used reference number, but we could also use 80 or 85 dB as well, as long as all the electronics and transducers involved can handle it (which I believe they should in your particular case). Once I read about 75 dB on each of my mains, I go to the next channel (usually the center) and adjust its trim until it reads 75 dB as well. Repeat for the surrounds. Currently, since I'm bi-amping my mains, I have to turn the other speakers quite a bit hotter. I think my center is at +6 and surrounds at +4 dB. I have a swing of +/- 10 dB in each channel's trim level, so I'm not really getting toward the limits of my preamp.

If you are doing that, and you are turning the surrounds trims to their maximum, but you can still only read 72 dB when the mains read 75 dB, then you can drop your mains to, say -5 dB, and then you should be able to achieve a common reading of 75 dB for all channels in the system. From there, you should be able to turn up the system as a whole beyond the 75 dB level, but in reality that might be too loud for casual movie listening. I rarely listen to movies at "reference level" where I have done my setup (reference level being 75 dB in my system -- same as yours).

I don't think the problem lies with your receiver running out of power. Previously, I used a Denon receiver that I bought in 2000, rated at 70 or 80 WPC. I didn't read up on your particular receiver, but Rotel is a well-respected brand that I suspect would be "conservative" on their power ratings. In short, I believe your Rotel is superior to my Denon in terms of power, regardless of what ratings they have. I'd also imagine that the Rotel will probably be spec'd with "all channels driven." Do you know if this is the case or not? Either way, when you are doing a setup, all channels are NOT being driven, so you should have sufficient power to each channel during the test. So, getting a bigger amp isn't necessarily going to fix that problem. Also, it's my opinion that the surround channels aren't necessarily taxed all that much during "normal" movie sequences; therefore, you're really never going to run all channels at their max. Even during massive explosion scenes, not all channels are running at max. Furthermore, if you're at all using a sub and crossing your speakers over, a lot of the big power that's needed for bass will be diverted from your receiver and to the sub's amp, again taking power requirements off your amp.

I think something's wrong with your setup or perhaps connections. If you want to resolve these problems by buying a bigger amp, you might be disappointed. If you're just itching to buy a new amp, and a new toy, then hey, I totally understand that -- more power to ya! But I believe that you have a very capable amplifier section in your Rotel (especially, especially since you indicate that you don't want to get super loud), and that once you resolve these issues, you will be happy. If still want more power after that, go for it!

Let me know what you think...


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## enrique (May 24, 2007)

*Re: can someone explain this about amp wattge?*

I'll explain it as best i can.I have the analog meter for one.It's set to c and slow with the dial at 70.My rec. vol i have set to 75 since there is no 0 for ref. level.(marantz i had b4 had -to + w/0 as ref.).I use the test tone of the rec. when i calibrate.My mains and center using the test tones i'm able to set to 75db off the meter but when i do the surrounds at ref. level they are maxed out at 72db on the meter.So what i did was go back to the mains and center and reset them to read 72db like the surrounds.So now all speakers instead of being at 75db they are at 72db off the meter.My mains and center are about 9 ft from the sweet spot and my surrounds are 12ft.sub is 10ft.As far as what setting the rec was at(stereo,digital)i dont know what it was at when i did the calib. didnt know it would make a difference.


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## Otto (May 18, 2006)

*Re: can someone explain this about amp wattge?*

Hi rick,

It sounds like you are doing it right in general. So, when you are done, where are the individual trim levels set? Using the tones from the receiver is correct, and you're right that surround mode won't matter much when doing the set up. 

Now that you have all speakers set up to read 72 dB, you can turn your receiver up by 3 dB, and all will read 75, right? That is, turn the main volume knob up until they read 75 dB. Note that volume setting on your receiver, and that will be your "reference level."


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## enrique (May 24, 2007)

*Re: can someone explain this about amp wattge?*

I'm not home right now so i'll ty by memory.My lft main is at 8,center 5 o 6?,rt main 7 i believe,surrounds are at max.


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## Otto (May 18, 2006)

*Re: can someone explain this about amp wattge?*

OK. Return everything to 0 offsets. Then, while measuring one of the mains, start turning up the main volume knob until that speaker reads 75 dB. Then start going around the room, adjusting each channel until it reads 75 dB. With those settings, you should easily be able to get everything to the same level.


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## brucek (Apr 11, 2006)

*Re: can someone explain this about amp wattge?*



> Using the tones from the receiver is correct


I thought all processors/receivers had test tone routines that were used exclusively for speaker level balancing, and not for attaining any specific SPL level. I didn't think this test tone level was controllable from the master volume?

brucek


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## Otto (May 18, 2006)

*Re: can someone explain this about amp wattge?*



brucek said:


> I thought all processors/receivers had test tone routines that were used exclusively for speaker level balancing, and not for attaining any specific SPL level.


If you're talking about the auto-setup stuff, then perhaps. My Outlaw offers an auto-setup, but it never seems to get things right, so I just ignore it. Instead, I just go into the main channel level menu and choose the "manual" option to go through the tones (as you know, it's probably actually a pink noise). In the "manual" mode, the noise follows the channel for which I'm adjusting the level (there are also a couple other mode, but I always use manual).

I set all my levels this way, using the noises from the preamp. I've also gone back and tested with the AVIA disc, and levels were fine with that as well.



> I didn't think this test tone level was controllable from the master volume?


They are in my Outlaw and, IIRC, in my older Denon receiver as well (1705 maybe?)


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## Ryan-T (Apr 8, 2007)

*Re: can someone explain this about amp wattge?*

In my Sony 1000ES they adjust with the master volume. In my dad's older Denon they don't adjust with the master, I had to read the manual to find that the Denon's test tones automatically set the master to 00 and 75db.


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## enrique (May 24, 2007)

*Re: can someone explain this about amp wattge?*

well i did as suggested. put spkr trim to 0db.Raised the volume till it read 75db.Vol ended up at about 84 instead of 75 originally.Regardless setup endes as this.Mains &center +3,surrounds +8.


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## Otto (May 18, 2006)

*Re: can someone explain this about amp wattge?*

That's OK. I believe that while the indicator on your volume control may increment in steps of 1 dB, it's only relative, as they cannot guarantee that a setting of 75 on the volume display of the Rotel will correspond to a speaker measurement of 75 dB (in fact, it's very unlikely based on all possible parameters). 

So, you are able to get all speakers to read 75 dB on your meter with main offsets of 0, center offset of +3 and surround offset of +8. Sounds good, I think you are done. If you feel that you are too near the maximum of the surrounds, you can kick down the mains to, say, -4. That should cause your center to end up about -1 and your surrounds about +4. That way you are more about the center of each channels trim offset range. Either way, I doubt it will make much difference sonically.

So I think you are all set. How does it sound for movies and music? If you're still want to buy an amp, see if you can test drive one first...

Good luck!


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## enrique (May 24, 2007)

*Re: can someone explain this about amp wattge?*

Actually i was mistaken what i ended up with mains at +3,center at 0,surrounds at +7,and sub at -1.I may change the sub a little hotter.


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## Otto (May 18, 2006)

*Re: can someone explain this about amp wattge?*

I think you are OK with that setup. Nothing wrong with that.


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## enrique (May 24, 2007)

*Re: can someone explain this about amp wattge?*

forgot to say thanks for the help.


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## Otto (May 18, 2006)

*Re: can someone explain this about amp wattge?*

No problem, man. Hope it works for you and let us know if there anything else.


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## enrique (May 24, 2007)

*Re: can someone explain this about amp wattge?*

actually there is.I actually posted in a different section in regards to the denon 2900 or the 3910.I'm mving my denon 2200 to another room and am looking to upgade to a better sacd/dvda player for the main room.I was inquiring between the 2900 or 3910 with priority to the sacd/dvda playback.someone had also sugested the 2930ci but after reading some i understand ther are problems with the 2930ci as well as 3930ci in playback of dvda/sacd especially with hybrids.I'm looking or a player in the price range of the 2900 or 3910.I realized they are used but am willing to get used if they are the better players.3930ci is out of price range,2930ci have used units available within same price range.I'm gussing it will come down between the 2900 or 3910,but which one.


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## Otto (May 18, 2006)

Not sure I can help you with that one. I don't have any SACD/DVD-A discs...


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## jackfish (Dec 27, 2006)

*Re: can someone explain this about amp wattge?*

Oppo DV-981HD. You could spend 3 times as much and probably not see and hear much difference.


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## Woochifer (Oct 19, 2006)

Most home theater receivers that can handle 4 ohm speakers do not recommend connecting more than a pair of them at a time. As others have said, Rotel is a reputable manufacturer, but there are merits to connecting an external amp if you use low impedance speakers all the way around. And if you have huge differences in the levels that you need to set for your speakers, I would guess that you are using mismatched speakers in the center and/or surround channels. If this is the case, you might want to consider matching the speakers all the way around first before trying to tackle any issues with the amp.

I would not rely on any rules of thumb regarding the wattage levels that would justify adding an external amp. Just because your Rotel is rated for 75 watts/channel does not mean that you have to double the wattage on the external amp. The wattage rating has practically nothing to do with the ability to level match your speakers all the way around. That's more of an issue around the sensitivity of your speakers, and the level setting range that's available through your receiver. 

An external amp might help in the sense that the levels can be set independent of what your receiver can adjust for. But, that would apply no matter if you attach a 200 watt/channel amp or a 50 watt/channel amp.


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## enrique (May 24, 2007)

thanks,just for reference the mains are the only ones that are 4-6 ohms.I've been checking quite a bit for the heat of the reciever and i dont think i gets any warmer than normal.It's also on practically all day long.I was just trying to avoid any possible future issues.I really dont think that i will.Everything is pretty much perfect now.


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