How much power do I need?

[edwinr]

Okay...

My Belles have a sensitivity of around 103dB @ 1watt/1meter. I am driving them with a CEC Classic Tube 53 amplifier rated at 20 watts per channel. Bench tests have indicated this little amplifier punches out about 14 'clean' watts per channel. I'm trying to work out what maximum spls I can expect in my room with this miserly 14 clean watts.

I have searched the web, but this area is a little confusing for the uninitiated. I've kinda worked out that loudspeakers generally require a doubling of amplifier power for a small 3dB increase in spl. And this small increase is only just able to be detected by most people. So, I guess buying a huge and expensive high power amplifier to get more spl's is a waste of time and money for most people.

Do I need more than 20 watts for spl's of say - 115dB in my room? Not that I'd ever listen that loud, but it's nice to have some headroom. []

[Coytee]

I'd say yes to more power....but then... I'm sitting with a biamped Jubilee under a Crown K2 (one for each speaker).

Another way to look at it is, if your amp has 14 clean watts.... is the 14th watt actually as clean as the first? (might be for all I know)

If however, you have say, a 100 watt amp then you might get up to 50 watts before you start wondering if the 50th watt is as clean as the first and if you can get up to that level, then you might have more than 14 net clean watts available to your Belle's.

Perhaps a bad anlogy but (gas expense set aside), I'd rather have a more powerful engine in my car. It's always less net stress on the engine than a lessor powered engine especially if it's pulling any kind of load.

[WMcD]

See attached.

Note that you're almost at your goal with 10 dB headroom. And you're at the edge of too dang loud.

IMHO, you'll be okay with the present amp.

Wm McD

Amplifier Power and Klipsch Speaker DfH.pdf

Amplifier Power and Klipsch Speaker DfH.pdf

[HarryO]

See attached.

Note that you're almost at your goal with 10 dB headroom. And you're at the edge of too dang loud.

IMHO, you'll be okay with the present amp.

Wm McD

Yea, like he said. 5 watts is sweet and 14 will rock.

[seti]

One of the sweetest systems I've had was a pair of Belles fresh A crossovers George Wright Preamp and Canary Audio CA-300 8wpc SET. I could be very happy with that system again.

[CapZark]

I have a 270 watt Pioneer SS reciever that sounds like tubes (sorry tube lovers), and I've had tube amps (McIntosh). There's enough headroom to blow your speakers into the next state and all of it is clean. Yes, it's ridiculous, but I only crank it up a third of the way when a newbie comes over to hear my Klipsch speakers and I want to blow their ears off. Most of the time I'm running around a watt which is usually loud enough for me. After few beers I might go past 15 watts, so 14 clean wouldn't do me much good. Personally, if I went back to tubes I would look for at least 60 watts.

[edwinr]

Thanks for the comments. Thanks Gil for that interesting article on power requirements.

It looks as though the power rating of my amplifier is sufficient for what I want. I can understand those that listen at lower spl's or may have smaller room may require less power. But I like listening LOUD. Those with larger rooms will require more power for the extra headroom. Frankly Craig's VRDs would be ideal. But I got the CEC at a really good price.

I have to say, initial listening impressions are very good, although the first few hours sounded very ordinary. After a couple of days, the amplifier opened right up, with crystal clear highs and a surprisngly robust bottom end. The soundstage is excellent as well. I had a Audio Note Soro SE before. The Soro was okay, but I couldn't see the tubes (!) and the bass was a little soft on the Belles.

Here's a pic:

[djk]

14W is 11.46dBW.

Assuming the amplifier will drive the Belle on the 8R tap, then 103dB + 11.46dBW = 114.46dB (peak at 1M).

At a distance of 10' the loss from inverse square law will be about 9.67dB, so you're down to about 104.8dB (peak), and you can add another 3dB for the other speaker (assuming a stereo pair).

This is about what an orchestra does in a mid-sized hall.

[Colin]

I have upgraded Bottlehead 2A3 Paramour mono amps driving my

big ole horns. The Paramours use a single 12AT7 tube to drive 5” high Valve Art

2A3 bottles. The 2A3 tubes (one per mono block) operate in a parallel feed

output mode. Seemingly under-powered, the rated output for these light, Kleenex-box

size amplifiers is 3.5 watts at THD level of 5% into 1kHz. Peak power is six

watts.

The volume dial on my Dynaco Pas pre-amp correlates to power

output of the amps. Half way is about half power. At 12:00 on the dial I

recorded fast, c-weighted mid 90 Sound Pressure Levels on my analogue Radio

Shack meter.

So Gil is right. You have as much power as you need for the

mid and high end frequency range.

The best bass I’ve heard on big ole Klipsch horns was

NOSvalves’ VRD tube amps.

But what more power does is give you is control over the

bass. See:

http://www.enjoythemusic.com/magazine/equipment/0202/passx250.htm

That’s why I have a passive dual amp arrangement now with a

massive, low power Pioneer Class A amp.

Belles and LaScala models do not have any deep bass. Bass requires

enormous amounts of energy. Large woofers also require enormous impedance

control. Solid state amps control woofer impedance better than tube ones do. That

is also why I have a deep bass ACI Titan sub-woofer with a solid-state amp.

[edwinr]

The bass from the Belles is surprisngly robust. At least it is now that I've repositioned them in the room.

I had a pair of REL Strata 5 subwoofers before, and I had to sell them due to some medical bills. I also had to sell my Audio Note amplifier. Fortunately I was able to keep the Belles. To compensate for the loss of the subs, I began experimenting with the room positioning. I read somewhere on the Klipsch Site that the Belles sounded 'better' when pushed into corners. So that's what I did. I rammed them hard into the corners (like my old Klipschorns) and I was rewarded with substantially more lower end punch! (Wow!) But the downside was there was a little boom in the bass - possibly due to room nodes etc.

So I gradually pulled the Belles out from the corners until I found a sweet spot where the Belles have decent low end punch without the boom. They sound pretty decent now and I can listen to most MOR CDs like Dire Straits and stuff like that without wishing I had a sub. Classical music sound great and I would probably never desire a sub if that's all I listened to. But a sub is high on my list of things to buy this year. I was thinkiing about a low cost Sub-12 or maybe a RW-12d for a little more money. I've heard good things about the SVS PC-12 NSD as well.

Now before I got the CEC tube amplifier, I was driving the Belles with a s/s Pioneer thing. It's about 102 years old and it hisses like a cobra on heat. So I went begging to my old hi-fi store and after I fell in a blubbering heap at the store owners feet, he gave me this CEC amplifer at an outstanding price. In case you're wondering, I haven't paid him yet!

OMG! I feel a bit like thebes!!! (Sorry Marty...)

So getting back to the CEC Tube 53/Belle issue, I wnated to make sure that this was an okay match, because if I really stuffed up with the amplfier choice, I could take it back, maybe. But based on what you guys said, and the way the CEC has opened right out vis a vis sound quality and music reproduction, I am reluctantly developing a little respect for this little mother. It's not a bad amplifer at all. It has NO hiss at all, Even with my ears right up against the horns. That's pretty impressive.

I think, more importantly, the Tube 53 seems to like the Belles. I know there's a lot more to amplifer/loudspeaker matching than mere specifications...

Sorry about the ramblings guys. It's just that when I think I know everything about hi-fi... I seem to hit a wall and have to start my knowledge base all over again. [*-)]

P.S. Colin, reading that enjoythemusic.com link about the Pass Labs X250 makes me smile when I think of the CEC Tube 53's thumping 7 watts per channel output @ 30Hz!