Right up front I'll tell you I'm a 2 channel stereo guy who doesn't do 5.1. The KEF LS50's are a great little speaker that are fairly inefficient. What that means is they will sound better with better amplification. I listened to them at the AXPONA show in Chicago this past April. They sounded great, but they were being driven by a $2,000 tupe integrated amp. I heard them about a month ago at a local Cincinnati A/V dealer. They were being driven by a Japanese A/V receiver and they sounded good, but not great. If your committed to doing 5.1 then I would advise getting a more efficient speaker, maybe something like one of the Wharfdales or Focal.

You NEED to stick with Kef for the center channel and most likely the rears if your. I would get either an R200C at $999 and the R800d dipole at $1799 as those will mesh best with the LS50s short of stepping up to the reference series which is way over your budget.

You are going to need a sealed sub with a lot of power if you want to be able to switch between Music and Movies flawlessly. I would suggest one of two brands, NHT or Sunfire. The NHT B-10d is $599 though and it does to 28hz with 300w of power. The B-12D is a better choice at $799 as it 500w and goes to 27hz.

If you want full frequency response down to 20hz, you need to spend a bit more. The Sunfire HRS line has an 8", 10" and 12" option. All are 1000w and deliver 22hz, 20hz and 16hz respectively but are $850, $950 or $1050 respectively.

I have an HRS 12 in my home theatre and it is super refined and gives you the detail you hope for when listening to Jazz or Classical yet it can deliver big in a home theatre environment and makes my mirage seem like a little noise maker.

If I were you I would get the NHT b-12d or the Sunfire HRS 10. I know that puts you over your budget by $500 to $800, but it is what it will take to pair up nicely with those Kef LS50s.

On a side note, I am not a fan at all of Pioneer receivers. They sound very bright and through those Kefs, which are very revealing, you might hate it. Given that this system is music centric, I might return that Pioneer and get an NAD or a Marantz.

The NAD T758 is the same price, $99, but is a much better audio centric receiver than the Pioneer. The only issue with NADs is they tend to use dated versions of Audyssey. Marantz has better video processing and a newer version of Audyssey with very, very good sound and is $899.

Good luck

The best-sounding subwoofer I have found for under $1000 is the NHT B12D; it is excellent, and is only $800.

The Pioneer receiver and the KEF speakers is like using an old Nissan mini-truck to pull a 30-foot fifth-wheel trailer. It ain't gonna cut it. The power specs on that receiver smell like a 5-day-old fish. Totally ridiculous. The power supply is so small it can't begin to drive speakers that really take large peak drive currents like the KEF.

My first bit of advice would be to dump the receiver and get a NAD T777 receiver. It will drive ANY speakers and maintain low distortion. Even the $1000 NAD T758 will be a MUCH better receiver than the Pioneer junk for driving those speakers.

commsysman wrote:

The Pioneer receiver and the KEF speakers is like using an old Nissan mini-truck to pull a 30-foot fifth-wheel trailer. It ain't gonna cut it. The power specs on that receiver smell like a 5-day-old fish. Totally ridiculous. The power supply is so small it can't begin to drive speakers that really take large peak drive currents like the KEF.

My first bit of advice would be to dump the receiver and get a NAD T777 receiver. It will drive ANY speakers and maintain low distortion. Even the $1000 NAD T758 will be a MUCH better receiver than the Pioneer junk for driving those speakers.

Wow, that is some outrageous claims. Sure, blame it on on the receiver for a speakers lack of efficiency and performance... : )

So, this is the speaker the OP is wanting to pair with SC-81?
KEF LS50
Model LS50
Amplifier requirements 25 - 100 W
Sensitivity (2.83V/1m) 85dB
Maximum output 106dB

And you said with strong determination and without a doubt the SC-81 can't power it?

Let's see now, given the LS50 inneficiency, the OP will need a 2048W amplifier to drive the LS50 at 106db. And, the OP
stated that the LS50 will be used for HT and I presume he will use it for main so, to get the 118db for live music or HT levels,
the LS50 is already lacking and maxed out at 106db.

But can the SC-81 drive the LS50 100W speaker? Well, given that Pioneer SC-81 is relatively new and is equipped with a
Class D3 amplifier, same amp used in the $7000 models, and is 120w per channel, I think it has more than enough power to
put your LS50 smoking at 106db continously in a few second(bit of sarcasm).

I ordered a Pioneer SC-81 and it should arrive tomorrow. The SC-81 is replacing my Pioneer Elite 91TXH and it will
be configured with the same set of Klipsch Reference speakers in 7.2 configuration with two La Scala as main. I could go
with other brands but I'm a long-time Pioneer Elite owner-follower and the brand has always performed above my expectations
without any issues or problems so no reason to change - to each is own... : )

Here's a speaker efficiency comparison and how one might consider it as one reason to choose a receiver's power to attain
the desired db level:

KEF LS50:
Sensitivity (2.83V/1m) 85dB

Klipsch La Scala(main):
Sensitivity: 104dB @ 1watt/1meter

To drive my Scala at 118db, for live performance or HT, the Pioneer SC-81 will deliver only 64W of power versus 2048W needed
for the LS50 at 106db.

Personally, I would rather buy the most efficient speaker first before deciding on an amplifier. I happened to like the Klipsch Heritage
line and Klipsch Reference myself because they are made in the USA, in Hope AR, and very efficient speakers and they're called Reference
speakers for many good reasons.

If you love your KEF, good for you, but be nice in your critism specially when you're giving advice... : )

PS: from KEF website
"THE REFERENCE: the standard by which others are judged, and to which they aspire." that made me laugh...

trueHD wrote:

Let's see now, given the LS50 inneficiency, the OP will need a 2048W amplifier to drive the LS50 at 106db.

I think you need to check your maths. +21dB is 128W for an 85dB 2.83V/1m sensitivity into an 8 ohm load which lines up with the KEF specification. Where I would agree is that the KEF LS50 has insufficient output to perform well as a main speaker. It is really a desk speaker or "near field" monitor.

andy_ wrote:

trueHD wrote:

Let's see now, given the LS50 inneficiency, the OP will need a 2048W amplifier to drive the LS50 at 106db.

I think you need to check your maths. +21dB is 128W for an 85dB 2.83V/1m sensitivity into an 8 ohm load which lines up with the KEF specification. Where I would agree is that the KEF LS50 has insufficient output to perform well as a main speaker. It is really a desk speaker or "near field" monitor.

Fair enough but the math is accurate based on 2.83v is 1W and if you believe or follow amp power is doubled for every 3db regardless of speaker sensitivity.

shameless plug:
I just had my Pioneer SC-81 installed the other day, fully calibrated with all 7+1 Klipsch Reference speakers pushing air at 118db, testing with Ice Age - Dawn of Dinosaurs(7.1), and I'm just blown away by the dialogue clarity and speaker dynamics at that volume level with RC-64(99db sensitivity) and La Scala(104db sensitivity), had to tone it down to 114db(prevent hear loss), which requires about 32W amp power for each speaker. Would not want to use Pioneer SC-81 to power anything else, let alone, a poorly designed speaker.

trueHD wrote:

Fair enough but the math is accurate based on 2.83v is 1W and if you believe or follow amp power is doubled for every 3db regardless of speaker sensitivity.

Don't you think there just might be a chance that KEF are not 2000% out with their specification? Particularly after someone has checked the calculation 2^((106-85)/3) and got an answer that broadly agrees with the KEF specification and not your huge number.

Like we all do from time to time you have made a simple mistake when performing a calculation but there seems to be something about the internet...

andy_ wrote:

trueHD wrote:

Fair enough but the math is accurate based on 2.83v is 1W and if you believe or follow amp power is doubled for every 3db regardless of speaker sensitivity.

Don't you think there just might be a chance that KEF are not 2000% out with their specification? Particularly after someone has checked the calculation 2^((106-85)/3) and got an answer that broadly agrees with the KEF specification and not your huge number.

Like we all do from time to time you have made a simple mistake when performing a calculation but there seems to be something about the internet...

You must be a KEF owner to be so passionate about the numbers. I didn't come here to talk bad about KEF speakers...I dind't know anything about them until days back. I was drawn in because someone talked highly about LS50 and his beloved NAD and trashing Pioneer because it's not his cup-of-tea. Thanks to him, I learned more about KEF speakers and have no interest whatsoever to own one - because they're just not efficient speakers, period. Why would anyone buy an expensive amp, generating unnecessary heat, just to drive a junk speaker to get at certain db level don't make sense.

About those numbers, don't worry about it. It was a simple comparison based on known SPL standards I got from the net and if you find it inaccurate, well, you're smarter. Stick with your specs and let your receiver/amplifier do the smoking.

andy_ wrote:

trueHD wrote:

Fair enough but the math is accurate based on 2.83v is 1W and if you believe or follow amp power is doubled for every 3db regardless of speaker sensitivity.

Don't you think there just might be a chance that KEF are not 2000% out with their specification? Particularly after someone has checked the calculation 2^((106-85)/3) and got an answer that broadly agrees with the KEF specification and not your huge number.

Like we all do from time to time you have made a simple mistake when performing a calculation but there seems to be something about the internet...

Let me leave you a final but hopefully a positive note.

The LS50 specs is correct; I never disputed their accuracy. How would I know if they are correct but trust what KEF listed. When you read my comment about the LS50 needing 2048W for 106db is arguably ridiculous, and looks to be incorrect and highly exaggerated, but only if you stop reading there. I never thought anyone would be paying attention.

The LS50 will push air at 106db at 128w but if you were to push it to 118db, aprox. a live performance or HT level, which the OP intended to use for, then because the speakers low sensitivity, it will need ~2048W to drive it at 118db probably for a short while, again, based on math; 2^((118-85)/3) = 2048.

Compare that with a Klipsch speaker, say a La Scala which has 104db sensitivity, it would only need 64w for 118db.

My point was to show how a speaker's sensitivity level can influence a decision what amp to buy; eg, a powerful and expensive amp to drive a low-sensitive speaker or something less powerful amp to drive a more efficient speaker but not the other way around where it's all about the receiver as some posters here tend to believe.

But I think we both agree the LS50 is not all that great as main speaker for HT. If the OP want to stick with KEF, he should look at KEF Reference series, if his budget allows. But if he already have the Pioneer SC-81, it will push the LS50 at 106db without a problem.

trueHD wrote:

The LS50 will push air at 106db at 128w but if you were to push it to 118db, aprox. a live performance or HT level, which the OP intended to use for, then because the speakers low sensitivity, it will need ~2048W to drive it at 118db probably for a short while, again, based on math; 2^((118-85)/3) = 2048.

Where does the figure of 118dB come from?

The normal reference level for films is an average level of around 85dB with a 20dB headroom for peaks. When the KEF LS50 is used as a desk speaker with the listener at a distance of 1m the peaks in the music should be cleanly handled. There are some qualifications but the general picture is about right.

However, if the LS50 is used as main speakers then the level of the peaks in the direct sound is going to fall by 6dB with each doubling of the distance. So if the listener is at 2m it is down 6dB and at 4m it is down 12dB.

At 3m say, the LS50 can still comfortably reproduce the average level and so it will sound loud enough but the peaks will be compressed. Listening at a 10dB quieter level will avoid distorting the peaks but the perceived music will now have slightly reduced levels of high and low frequencies.