Speaker sensitivity and wattage

[Rami]

Hi all,

 

Proud new owner of a brand new set of RP-150m bookshelf speakers paired to a Denon X520BT. Having “ascended” from a 10yo 50€ Hercules 2.1 “system”, I am ecstatic about the new system, it just sounds brilliant, also having had a great deal on both (300€ for

the speakers and 150€ for the AVR).

 

Being a complete novice in home audio systems, I’ve been silently rocking back and forth between here and AVSForums, and want to thank all of you for the amazing amount of information available.

 

The following questions remain unanswered though, and I would be very happy to have some feedback.

 

The RP-150m have a sensitivity of 93 dB at 1 meter (correct me if I’m wrong, but 93 dB is quite loud isn’t it?), which as I understand it means that they generate an SPL of 93 dB with just 1W of power. I usually sit close to the speakers (a foot away actually, they are correctly positioned as back channels but are connected as fronts now; I would also add that the system is calibrated for a listening position 10 feet away). As a result, I play them at a very low level, which I suspect is way below 93 dB, closer to say 50 dB. Does that mean that at that level, they are using much less than 1W of power, and if so how much power is being drawn from the AVR?

 

In a more general terms, how would one calculate the power drawn from the AVR? By measuring dB levels and using the sensitivity and logarithm function?

 

The context is also that I am planning on complementing them with a pair of RP-250F floor standers, a RP-250C center channel and a R-110SW (or R-112SW). The monitors will be the back speakers. Will the floor standers really improve music restitution in 2.0? What about music in 5.1, are the processing algorithms good (I am aware of this also being a subjective issue)? And more importantly, I think that this AVR is powerful enough for achieving moderate listening levels on the complete set, do you concur?

 

Expected usage scenarios are music 70% and movies 30%.

 

AVR specs:

Power Output (8 ohm, 20 Hz - 20 kHz, 0.08% 2ch Drive) 70 W

Power Output (6 ohm, 1 kHz, 0.7% 2ch Drive) 90 W

Power Output (6 ohm, 1 kHz, 1% 1ch Drive) 130 W

 

Cheers!

 

Rami

Edited February 12, 2018 by Rami

[Rami]

Ok thanks I’ll try this evening

[Rami]

Which would be a pleasing surprise to have, since it would mean that this entry level AVR really is well suited to run the entire system. I don’t listen too loud because my children sleep is the adjacent room. I am pleasantly surprised at how well music sounds at low listening levels.

[Rami]

Hi all

Just to let you know that I tried but my multi-meter cannot measure these voltage levels. I'll try some other time when and if I purchase a proper one.

Thanks

[garyrc]

How big is your room, in cubic feet?

 

When your system is complete, how far away will you be sitting from the front speakers?  Side speakers?  Back speakers?

 

If you have a medium room, you probably have plenty of power.  Try this calculator.  http://myhometheater.homestead.com/splcalculator.html

 

To reproduce movies at what is called Reference Level, you need each regular speaker to be capable of producing 105 dB peaks at the main listening position, and a powered subwoofer that can produce 115 dB peaks.  In your case, though, with sleeping children nearby, you will be playing them at a much lower SPL...

[garyrc]

Denon has Audyssey.  After living with your complete system for a few weeks, first read this: "Audyssey FAQ Linked Here" , then set up Audyssey.  It takes time and patience, but it improved my system like nothing else.  After finishing, almost everyone turns up the subwoofer by several dB.  There are many reasons for this, explained in the FAQ.  The 1/2 hour to 45 minute careful reading time of the Audyssey FAQ is time well spent.  Most manufacturer's manuals are ambiguous, potentially misleading, and poorly written.  The Audyssey FAQ linked here is a gem.

[Rami]

Hi garyrc,

 

Thanks a lot for the link.

 

Audyssey is indeed one of the reasons I would eventually upgrade AVRs, as I think mine only has a calibration mic; as you've pointed out, manufacturer information on this is rather sparse and I am not sure how much of the Audyssey algorithms are implemented in my unit. On the other hand, I am quite happy with the job it did on my current setup. From the current nominal listening position (couch facing north), it sounds great. I'll certainly give it a go with the new system that I am planning to get by summer.

 

When the system is complete, I will be sitting roughly 10 ft away from the fronts and 3 ft away from the back channel. I've attached a layout to scale of my living room. As it turns out, watching films with the fronts actually behind you is very frustrating (but in my defense I had music and simplicity in mind before starting)! The floorstanders will be on each side of the couch and the center channel above it (although I am not too happy about it being within reach of the children). The room itself is 13 by 13.5 ft and the ceiling is 12 ft high = 2100 cu ft. The foreseen nominal listening position will be opposite the couch facing south on some really comfy chairs, it is also the ideal position for watching films, making the RP-150M's (in orange) real back channels I guess (is this OK?). Due to the configuration of the room, surrounds wouldn't be symmetrically positioned, as the western surround would be a few feet further back with respect to the eastern surround. Will back channels be able to produce a good surround sound? The alternative, wall mounting the monitors (or surrounds) and having the western one play louder to compensate for distance, does not strike me as a particularly good solution.

 

I just fitted the Power to SPL table and derived the power consumption estimates for very low levels and can hardly believe the results:

SPL (dB) = 4,3281 * ln(x) + 93

where x is power in Watts. For 39 dB, I get less than 4 microwatts (yes, 3.8e-6 W). Even for 60 dB, I get less than 0.5 milliwatts. 80 dB sounds really like more than enough for my room size/conditions and it's still less than a watt. I'll try to do some actual measurement to see how well the 93 dB sensitivity rating holds up, but I am blown away by those numbers! Would I benefit at all from having separates instead of an AVR given that I am always using the linear amplification range of my current amp?

 

Cheers

Rami