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In Reply to: RE: What's Enough Watts? posted by thetubeguy1954 on May 25, 2007 at 05:35:44
A couple of threads below you talked about tube versus SS and that was one of our clinics at HE show in NY and now you are talking about watts, another one of our clinics at HE.
We set up a meter with momentary peak an average RMS watts to a speaker at the speaker terminals and played a number of pieces. The speakers were around 88db. At 2 watts RMS, it was very loud on the long term average. At 2 watts on the long term average, the momentary peaks were between 10-30 watts, depending on dynamics of the CD. We then demoed one CD where at 2 watts on the long term average meter, the momentary peaks were crossing 275 watts, and it was not that loud. Then we flipped the switch so people could compare the performance of the 30w tube amp to the 240w SS under these conditions.
You can read all about it in this month's AudioXpress.
Next time go to the show!
P
My speaker building site
Follow Ups:
Hi
It was /is not clear from your post if the idea was to expose the differences in the recordings, how two different technologies can sound different.
So far as amplifiers, nearly all SS amps have a hard Voltage swing limit which results in hard clipping.
Most tube amps were this way too although some could squeak out a dB more before one got to hard clip. Other tube amps had significant headroom and some only clipped on one side of the wave which is much less annoying, allowing a larger peak power.
Most folks are aware thanks to hifi lore that “Tube amps sound louder for a given size”, when it is true, it is because they have some headroom or reach clip more gracefully.
I see your with a magazine, have a web site and not averse to measuring.
Why not compare the difference between what goes into the speaker and what comes out.
No one talks much about how well speakers do there job and they are the weakest link..
Best,
Tom
The idea was to simply present variations and let people hear for themselves. We had one clinic which switched between amps, one that showed power needs, one the compared speakers, one about amp design and one on speaker measuring.
Wow, that is the first time someone said I am with a magazine. Cool! Although two articles in AudioXpress is not exactly a career. I have a day job and submit to them like everyone else. Not on staff.
I totally agree that speakers are the weakest link in audio. Sure some other link can mess things up, but the electro/mechanical conversions are the worst. Not sure what you are suggesting on measuring "what goes in versus what comes out". A lot of people do that, mostly better than me. If you are suggesting measurements to show speakers don't do a very good job, that is pretty well established, no news there. Did I miss something?
P
My speaker building site
Hi
You are hiding from the “bad news” if you only look at what comes out of the amp and speaker without looking at the signal that was recorded.
Loudspeakers are dynamically nonlinear and distort badly, from VC heating alone, dynamic compression and response changes happen starting at about 1/10 to 1/8 the speakers rated power.
Have you ever seen loudspeaker measurements taken over 1 Watt?
It is “normal” to hit speakers with peaks not only above that level but even to exceed the rated power.
No one shows speakers (that tries to sell them anyway) in ways that show all the flaws like this but they are present nonetheless.
Also, a meter doesn’t tell you if you have reached clipping, amplifiers generally have very little headroom, less than 2 dB, less than that on SS amps due to the limited supply voltage.
Short term clipping is not audible as clipping but can he heard when compared to “without”. For this, you need to look at the waveshape with an oscilloscope and look for flattening at the tips.
Best,
Tom Danley
Want a tough recording that will use up all your headroom and bandwidth?
Try the “fireworks” on good headphones first as a reference.
http://www.danleysoundlabs.com/knowledge%20baSE.htm
Maybe I have to reread the thread. I thought it was about watts and listening level. I don't think I am "hiding" from anything. I spent a ton of time and money to work for free to take a watts clinic to demo some of what you are talking about. People seemed to like it.
Sure speakers change at different demands, some worse than others. Is that OT from this thread?
You are right on clipping, no challenge there either. But when I take a 240W SS amp and play some cut that takes it to 270-300 every second or so with lots of other peaks over 200w, I would guess that switching to a 30w tube amp (or any 30w amp) without changing the volume will clip that lower power amp. But maybe I am wrong :) The clinic was about what we could hear in this comparison.
P
My speaker building site
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