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3 dB Dynamic Pwr v Klipsch 10dB above without clipping--Who knows?RoyD/Trey/Who/Al/Duke/Dean, all?


garyrc

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Who among you knowledgeable folk can clear up my confusion about "Dynamic Power" Vs the kinds of peaks referred to in the Klipsch chart.

In the Dope from Hope article and Chart -- "Amplifier Power to drive Klipsch Speakers" -- that has been reprinted in several threads several times (notably in "SETs Vs old SS Listening experiments"), both Keele (1977), and whoever revised the chart a few years later (PWK?? 1980 -- I think Keele had left by then) refer to the "Amplifier power rating (continuous average at 8 ohms)," and state that this allows "peaks 10 dB above average to pass without clipping."

Can someone answer the following questions?

1) Is there agreement on this in the electronics world?

2) Are they referring to Tubes or Solid State? Solid State pretty much had hegemony over the audio world in 1977 & 1980, so they would probably have thought that readers would assume Solid State (?).

3) Is "continuous average" the highest amplitude, long-term, unclipped sine wave in a test, or is it RMS, which I believe is .707 of that? I seem to have heard "continuous" used both ways.

4) How brief would these peaks be? How do they compare with whatever duration IHF, or other groups, use in defining and measuring peaks?

5) Since we are lucky to get specs of 3 dB dynamic power listed in manufacturers' spec sheets, is this really a discrepancy, or are the 10 dB peaks passed without clipping that are mentioned in Dope from Hope just a lot briefer?

6) Does anyone have duration measurements of the leading edges of cymbal crashes, rim shots, and other presumably sharp transients?

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  • Klipsch Employees

I have never looked into that question.

To keep from answering that question I say this...

Using the power rating of an amp, I use a factor of 5 to pick a amp.

If I know that 100 watts is all I will want at the speaker, I look for a amp that can give me 500 watts.

In the case of my LSII, I only need 20 watts or so to reach the levels that I want. Thus, I use a receiver that has about 100 Watts to each speaker.

I almost never raise the volume level above 1/2.

That gives me a lot of head room in the amp. Therefore, the amp works in it's most clean power range.

For speakers, the power rating we use is RMS.

We use pink noise that is limited to peeks of +/- 6db. Then we set the bandwidth to match that of the speaker. To set the output voltage, using the speaker as a load, we set the voltage to the spec while testing with a analog volt meter.

Then comes the fun part, we let them run WFO for 8 hr.

For the product we send to some of Asia, we test at WFO for 100 hr.

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2) Are they referring to Tubes or Solid State?

Tubes don't have Any advantage here ...

'cept clipping in't as objectionable

6) Does anyone have duration measurements of the leading edges of cymbal crashes, rim shots, and other presumably sharp transients?

most of what I listen to...is live recorded music

it is not unusual to see a rim shot / good snare hit as + 20 - +30 - +40 dB

Rodney Holmes of the Jim Wieder band ... is usually good for ++30 dB .....minimum .....[:)]

Duration ....

well, depend's on where ya draw the line on decay ...1.5 second's ....??

itsa ......Thwaaaak ..Factor ......[:D] [:D] [:D] [:D]

interestingly enuff ...

amp's with Switching power supply's ... don't look soooo hot , on transient's .....[:(]
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interestingly enuff ...

amp's with Switching power supply's ... don't look soooo hot , on transient's .....[:(]

huh? got to be kiddin right?

Dont be dissin on QSC. [:P]

They are one ss amp you can actually stand to stay in the room with with big ole horns[;)]
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Can someone answer the following questions?




1) Is there agreement on this in the electronics world?

I'd say not, especially now that CDs are
popular. 10dB would be for LPs and compressed
rock/alternative. I use 20 dB over average RMS power.






2) Are they referring to Tubes or Solid
State?

Irrelevant. There is NO SUCH THING as "tube
watts". Whan a tube amp clips, the result is not bad sounding
until the clipping is severe. SS amps clip and you hear it,
soon.






3) Is "continuous average"

It is average RMS and peak RMS. Always
think in RMS power. The peak ratings of the past were produced by
tests rigged to give big numbers. RMS power is real power.
It is a math thing related to the area under a sine wave.






4) How brief would these peaks be? How do
they compare with whatever duration IHF, or other groups, use in
defining and measuring peaks?

No way of knowing. Most people think of transients in milliseconds.





5) Since we are lucky to get specs of 3 dB
dynamic power listed in manufacturers' spec sheets, is this really a
discrepancy, or are the 10 dB peaks passed without clipping that are
mentioned in Dope from Hope just a lot briefer?

Unrelated. You may use the +3 db of dynamic
power to achieve your 20 dB of head room. Say you want to average
104 db on your K-horns with your favorite concert CD. 104 + 20 db
requires 100 watts (+20 dBW). If the amp can go 3 more dB, then
you *could* down size the amp to 50 watts (+17 dBW) and use its extra 3
db to get to 20.






6) Does anyone have duration measurements
of the leading edges of cymbal crashes, rim shots, and other
presumably sharp transients?

Sounds like a little time on Google.


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"4) How brief would these peaks be? How do they compare with whatever duration IHF, or other groups, use in defining and measuring peaks? "

Some info, the manufacturer of the tweeter driver used in the heritage line (t-35), went as far as indicating the t-35 can handle 5 watts continuous and 25 watts peak (10ms) . Any headroom expectation should factor in the manufacture's stated coil burn out threashold and duration.

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interestingly enuff ...
amp's with Switching power supply's ... don't look soooo hot , on transient's .....[:(]
huh? got to be kiddin right?
Dont be dissin on QSC. [:P]
They are one ss amp you can actually stand to stay in the room with with big ole horns[;)]

the bigger PLX's are Switchers ..

not the 1202/ 1602

I'll post a graph of wht happens to the 2nd transient, with a switcher ..

it's not pretty ..

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Generally speaking "continuous" is a heat rating (as are all wattage-related things), or simply put, the ability to dissapate heat which is measured in watts.

Also, it should be pointed out that a frequency MUST be given in any power rating, and that is not always the case, either. Hence the "average", which doesn't really explain much, does it? It means that there COULD BE a great deal of unevenness involved, covered nicely by the "averaging"...

Decibels and Watts are also two different things, watts being electrical, and db's being a sound-pressure measurement. Alot happens in between the two, like how one goes from one to being the other, heat being the natural result.

Do not confuse "tubes" and "SS" topologies as having ANY special effect on either db's or watts! Like I said before, WATTS are heat, DECIBELS are sound-pressure measurements, and what do either of those have to do with tubes or SS?!

In short, the answer is NO, there is no concensus.

DM

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interestingly enuff ...

amp's with Switching power supply's ... don't look soooo hot , on transient's .....[:(]

huh? got to be kiddin right?

Dont be dissin on QSC. [:P]

They are one ss amp you can actually stand to stay in the room with with big ole horns[;)]

the bigger PLX's are Switchers ..

not the 1202/ 1602

I'll post a graph of wht happens to the 2nd transient, with a switcher ..

it's not pretty ..

All of the QSC PLX and SRA's have switching power supplies. That is the whole design concept of this particular line of amplifiers.

Maybe you are confusing Class AB output of the smaller QSC's with Class H output of the larger models.

I have a 2422 which is indeed class H and basically all it does is sound great and kick arse!

"With PowerWave technology, the PLX series take your

music to a whole new level. Not only does it deliver bigger bass and cleaner highs,

PowerWave also cuts wasted heat and boosts reliability. PowerWave is a switching

power supply that provides ample current to the audio power circuitry by

charging the supply rails 230,000 times a second through an ultra-low impedance

circuit. So unlike other amps with conventional supplies, the audio signal is never

starved prematurely and remains crisp and clean. It virtually eliminates hum and

greatly reduces noise, providing a vast dynamic range that can handle any music

without running out of headroom".

What I think has happened Duke is QSC has actually perfected or a least done a fine job

with the switching of their power supplies because they do make for great ss amplifiers.

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In my view there are three questions or issues. I have seven subjects below but they are inter related.

1) How much higher are transients in orchestral music above average. This goes to pickup, transmission, and storage (recording issues).

I seem to recall that 13 or 18 dB is the figure. Memory is not clear on this. Let's use 13 dB. It means that power is 20 times as much.

So when Bell Tel set up a line for transmission, the average level set at 0 dB on a calibrated VU meter. That was 1 milliwatt into a 600 ohm transmission line. You would set a continuous tone at that 0 dB level for tests. Then the indicated peaks were supposed to be limited to 0 dB.

Implied in this was that amplification along the line had to be non clipping up to 13 dB above that level.

The same I believe was true of tape recorders and the mixing boards and the VU meters used to measure them.

The VU meters had particular "ballistic" characteristics. The meter needles were too heavy to indicate peaks, but the sluggishness was standardized. They were known not to indicate actual peaks. Rather, showing peaks to 0 dB was an indication that we were having actual peaks 13 dB (or so) above.

2) The next, close question is, how close are our speaker's danger points above the average we might see on a meter (and what sort of meter). As John pointed out, a tweeter driver might be rated for 5 watts continuous. Can it handle 13 more dB on short peaks? I think the answer is "probably".

Some of the "probably" depends on the duty cycle. I.e. how long are the brief peaks in relation to the average, or the off cycle?

It is interesting to look at the review of the Forte where Julian Hersh (?) put in over a kilowatt in bursts. I don't have the article here. And I don't recall at what frequencies but I believe he used tweeter type frequencies at one point. Generally tests bursts are 20 percent or less in duration. Something to look up. The off time allows the little darlings to cool off and not melt things.

This also assumes that you've not reached the mechanical limit of travel. See below.

3) A related issue for speakers is the spectral distribution of power in music. There is a graph in the Symposium paper which is part of the Klipsch papers. It is almost a bell shaped curve.

Generally, the most power is in the midrange. That changes of course with organ music or modern pop with synths which is bass heavy. The power in the tweeter range is lower.

These sort of genealizations are necessary if we have a meter which just gives us one read out. In music it may go up to 0 dB or whatever in peaks. But is that going into the bass, mid or tweeter? We can assume it is the total but not how it distibuted over the frequencies?

A real time analyzer (RTA) will give us a much better idea of what is going on with the music, and therefore what is going into any of the bass, mid, or tweeter frequencies.

You can use Windows Media Player and a music CD to get an idea of spectal distribution by using its Bars and Waves display. A crude RTA of the signal off the music CD. It is not calibrated in frequency or dB. None the less you will find that the bars at the right (tweeter) are not very tall. It has a nice actual peak indicator which the bars push up. Yup, the very computer you are using to read this is a potential learning tool, and it is "free".

The bottom line is that power in music can't be descibed in a simple way. So it is also difficult to measure what is going into a speaker system.

4) This means that a K-Horn can take continuous power of 100 watts in the K-33, 30 watts in the K-55 (per Atlas spec), and 5 watts in the K-77 (per EV and PWK). (My recall.)

But you can see that duty cycle of peaks, and spectral distibution, will alter this when it comes to real music. E.g. you can have 100 watts of bass (average) in music, but 5 watts average in tweeter type overtones (which is spectral distribution), and things are okay. And you might push in 20 times (13 dB more) in transients, which the drivers will stand if this doesn't push them beyond physical limits.

5) From what I've read, most limits on drivers or causes of failure are thermal limits. Tweeters burn out. But I believe that many home woofers are killed by mechanical failure. We see stories of commecial incidents where the voice coil starts a fire.

In the home setting: some popular music is rich in bass (infra sonics) which is not easy to hear on most speakers. The bass drivers bottom out. This makes a ticking sound at first (sounds like tweeter) and eventually a clanging sound (sounds like midrange). People don't realize these are the sounds of the woofer bottoming out from infra sonics.

6) Sharper roll offs in the crossovers do help prevent out of band power from getting into the tweeter or mid. That is why PWK increased the order of the slope to a 3rd order 18 per dB roll off.

7) The above is a bit murky in that it shows how difficult it is to get a clear definition of how much power there is in "music" and how to measure it. Even an honest manufacturer is hard pressed to say how much music type signal a driver will absorb without malfunction. Further, hucksters have license to exploit the uncertainty.

Modern standards are based on the application of band limited noise to the driver. I don't know the specifics but they allow everyone to have a common standard which can be set up on lab instruments.

OTOH, it seems to me that this does not translate easily to what is going on with your speaker, amp, living room, music, etc.

Therefore, rules of thumb, come back to the fore.

Best,

Gil

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Stormin, I think I remember you from about a year ago. Weren't you driving with a Marantz back then? When did you get the QSC, and how does it equate?

Jeff,

Personally I am a big marantz fan especially the 2325. Mine has been gone completely through and up to factory spec. But when I added the QSC, which is really a monster amp for horns but sounds so damn sweet, the music went to a new level. The bass is solid compared to just punchy the mids are smooth without glare and the highs are sweet without grain. I just hear so much more of the music than what i was hearing with the marantz alone.

I like aragon too but mine is just sitting. But this QSC is just a smooth animal.

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Well Jeff,

The marantz makes for a pretty descent preamp with alot of options also a pretty kick asrse tuner.

As far as other preamps I would only switch out the marantz for a tube pre and the options are very limited due to the low impedance of the amp. Still eyeing the peach or maybe the kit merlin. Those would both fit my needs. But havent spent the money yet because like I said I am having fun with what I have at the moment.

My amp is the 2422 which happened to sell for 1,999 new.

http://www.qscaudio.com/products/amps/sra/sra.htm

They no longer sell this line but it is basically a PLX 2402 in a little fancier case and quieter fan and there are a few spec differeneces as well.

Also per QSC the damping factor @ 400hz and below where crown rates theres is 3000. But on their spec sheet it just says greater than 500 at 1khz and below.

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Looks like a real slugger. I've seen fairly consistent accolades here for QSC. I remember back when I bought my Crown 20 years ago, I saw the QSC's also on display. This was in a drum/guitar shop, so there was no test-driving. I asked about QSC, and they told me it was a new, less-expensive, up-comer to challenge Crown. I don't know that what I was told was true, but one thing I have noted is that while Crown continues to make some great stuff, they constantly seem to be discontinuing tried and true lines and moving into cheaper ones.

I hear more and more good talk about QSC. I bet the one you have does sound good. Looks good, too.

When did you say you got that QSC? Was it before or after we had that never-ending "headroom" thread about a year ago? I just wonder if maybe that thread prompted you to check out using a "pro" amp, or did you already have it?

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That thread got me thinking and all the talk about QSC with the horns and also that Klipsch was even using them in their lab just made it a no brainer for me. Figured I would give it a try and sure glad i did. So in a way I should say thanks Jeff.

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Also per QSC the damping factor @ 400hz and below where crown rates theres is 3000. But on their spec sheet it just says greater than 500 at 1khz and below.

I have no doubt there is plenty damping factor there. By comparison, I looked up a better quality AVR model by HK (I think 85 wpc), and it had a damping factor of something like 80. I was surprised that I actually found them giving the spec.

I have read a few differing statements along the lines that a person should look for a min. damping factor>200.

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That thread got me thinking and all the talk about QSC with the horns and also that Klipsch was even using them in their lab just made it a no brainer for me. Figured I would give it a try and sure glad i did. So in a way I should say thanks Jeff.

Cool! I know very little about this stuff, but I can say first-hand I definitely know the difference between a pro-amp and Marantz. I went from Marantz to Crown. The Marantz was certainly very good - and the one I had was one of their better models. But the Crown..... [;)] You know what I mean.

So, the thread got you moving. Tell me, what was your first impression when you plugged in your QSC? Was it kind of like a revelation?

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Yeah I was suprised and over joyed at the same time. The folks led me in the right direction around here. Got to love the Klipsch forum and the wealth of knowledge one can gain here.

Yeah, I thought so. I am very cynical in regards to alot of the talk about how you spend hoards of money to get that last 5%. You know the common phrases used around here.

When you stuck that pro amp on there (which was no huge money outlay), it was probably like 50%. That's why I am big on amps and speakers, but not on CD's and Pre-amps.

If you really want to hear that QSC sing, take it over to someone's who has LaScalas or KHorns. That will blow your mind.

My friend has Chorus. They are very good. But watch what happens when you feed that kind of power to the much larger mid-horns.

By the way, I'll bet you've already noticed that your QSC never gets hot, never breaks a sweat, and you have so much headroom in that thing that you sometimes are afraid you'll accidently bump the volume knob and kill your speakers.

They are such great workhorses.

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