Jump to content
The Klipsch Audio Community
Emile

Low power amps on speakers

Recommended Posts

Hi All,

 

Just wondering if "low power" amps hurt speakers.  Had been discussing this with CrutchField, etc ... and they said low power will damage your speakers. (In my case, have a set of KPT-904's ... recommended minimum is 800W/ch ... used to drive them with a Marantz 2252B at 52W/ch, but now trying a Crown K1 at 350W/ch ... not sure if it sounds any better ... though think it's a "yes.")

 

Know many of you (myself included) have driven Klipsch speakers with 1-5 Watt tube amps (and also low Watts SS amps). I never had a problem :)  

 

So; any truth to this or are "they" just trying to upgrade us to bigger amps?

 

 

Share this post


Link to post
Share on other sites

Add-on ... 

Have "no clue" why a 1 Watt amp at full power would be different from a 1000 Watt amp set to 1 Watt power would be different to speakers :D 

Share this post


Link to post
Share on other sites

As long as you aren't clipping SS amps, it isn't a problem. 

  • Like 3

Share this post


Link to post
Share on other sites

As long as the power is Linear, can it hurt ?

  • Like 1

Share this post


Link to post
Share on other sites

If you've got a voice coil capable of dissipating 10 watts and you only put 1 watt in it won't care if its a sinewave or a squarewave. You may not like how it sounds but a watt is a watt.

  • Like 1

Share this post


Link to post
Share on other sites

Typically this is true, you do have a more likely chance of damaging "speakers" under powering them with a lower powered amp that

gets driven into clipping while trying to achieve greater output.

 

But with something like your 904s with a 105db sensitivity I would doubt much more than 10 or 20 wpc would be needed to generate

an output that would satisfy most without worrying about clipping the amp.

Klipsch does say 904s minimum power requirements are 800wpc but lets put that in the context of what these speakers are designed for...

200 seat auditorium with a 2800 sq ft room, that would be a room approx. 60ft x 46ft.

"Headroom" is always nice to have, but with our speakers we do not need a ton of that for any sane listening levels.

 

1 watt will make 105db output, 2 watts will make 108db, 4 watts will make 111 db, 8 watts will make 114db... etc.

105db is pretty loud, at least to my ears.

 

  • Like 2
  • Thanks 1

Share this post


Link to post
Share on other sites

You have a better chance of hurting your speakers with a low power amp trying to do too much, than a high power amp having to do too little. I have clipped and fried two pair of 200 watt speakers with a 35 watt receiver. I have never damaged any speakers using 200-600 wpc amps

  • Like 3
  • Haha 1

Share this post


Link to post
Share on other sites

Yeah; never heard any clipping with my 52W/ch Marantz on these 904, 800W speakers :D  But; the 350W/ch Crown K1 seems (???) to give a "tighter" response. :) 

Share this post


Link to post
Share on other sites

Emile, seeing you spend good money on speakers....spend equally good money on an amp. Pro amps may work for the 904 since they are designated pro speakers but i have no idea who wants to hear a pro amp in a home setting outside of for powering a sub

  • Like 1

Share this post


Link to post
Share on other sites

I use 3.5 watt amps for my LaScalas and Heresy IIs.

 

Haven't killed anything yet... 🙄

  • Like 5

Share this post


Link to post
Share on other sites

I’m using my 0.75 watt Darling Amp (6sl7/1626 with gz32 rectifier for my horn speaker - no problem and i love it





Sent from my iPhone using Tapatalk
  • Like 2

Share this post


Link to post
Share on other sites
1 hour ago, teaman said:

Emile, seeing you spend good money on speakers....spend equally good money on an amp. Pro amps may work for the 904 since they are designated pro speakers but i have no idea who wants to hear a pro amp in a home setting outside of for powering a sub

Not all pro amps are the same, your right some are terrible (noisy) for home use with really sensitive speakers and some are as good, I used the Crown D-75 for years until old age got to one of them. With horns that were way over 110db@ 1 watt and dead quiet and a nice sound.

 

D-75

Frequency Response +/- 0.1 dB from 20 Hz to 20 kHz at 1 watt
Phase Response +10 to -15 degrees from 20 Hz to 20 kHz at 1 watt
Signal to Noise 106 dB from 20 Hz to 20 kHz at full bandwidth FTC power
THD Less than 0.001% at full bandwidth FTC power from 20 Hz to 400 Hz increasing linearly to 0.05% at 20 kHz
Intermodulation Distortion (60 Hz and 7 kHz 4:1) Less than 0.01% from 0.25 watts to full bandwidth FTC power, and less than 0.05% from 0.01 to 0.25 watts
Crosstalk Greater than 100 dB below full bandwidth FTC power from 100 Hz to 1 kHz decreasing linearly to 80 dB at 20 kHz
Damping Factor Greater than 400 from DC to 400 Hz
Controlled Slew Rate 6 volts per ms. (Slew rates are limited to useful levels for ultrasonic/RF protection)
Voltage Gain At maximum level setting, 8-ohm load, 0.775V input sensitivity
Load Impedance Safe with all types of loads. Rated for 4 to 16 ohms in dual mode, and 8 to 16 ohms in bridge-mono mode
  • Like 3

Share this post


Link to post
Share on other sites

The only thing I ever blew up was a pair of 300 watt subwoofers by sending them 400 watts each.  Cost me 4 new drivers. 

 

But the common tale is a clipped small amp can overheat and kill a voicecoil faster than an unclipped amp many times larger. 

  • Like 2

Share this post


Link to post
Share on other sites

Okay, just to be clear, I am not talking about tube amps. I have never heard of a tube amp clipping. I am talking about low power solid state receivers or amps. There have been plenty of times I have seen under-powered receivers trying to push speakers to loud listening levels where distortion is audibly discernible. If not immediately turned down you risk clipping your amp and usually the result is fried tweeters.

  • Like 1

Share this post


Link to post
Share on other sites
4 hours ago, JohnA said:

 ... But the common tale is a clipped small amp can overheat and kill a voicecoil faster than an unclipped amp many times larger. 

 

This is what most people say, and I'm guessing it is correct.  There is one individual on this forum (I forget who) who says it can be demonstrated that it is not true. 

 

 @Emile, how big is your room?

 

In my 4,000 + cu. ft. room at 13 feet it takes only about 8 watts to produce 107 dB continuous with one Klipschorn, which is rated at the same 105 dB/2.83v/1m as your speakers, BUT the Khorn needs to be in a room corner (1/8 space) to produce that, and yours gets rated at 105 dB with just 1/2 space, so it doesn't need as much power.   With that Crown you have a huge amount of headroom.

 

Just don't let irresponsible people near your volume control (lock it behind Lexan at parties, with plenty of ventilation), don't insert or pull out a RCA plug with the power on, and don't rewind or fast forward tape with the power on, especially on a vintage reel to reel, etc., etc.

Share this post


Link to post
Share on other sites

Before I went to an all active setup I used a Korneff 45 amp on my khorns for years never hurt anything, and that amp only puts out 2 wpc max on it's best day!!!

  • Like 2

Share this post


Link to post
Share on other sites

Clipping is when the gain at the peak or trough of a waveform reaches the supply voltage.  Happens all the same tubes or sand.  There's more to it but in a nutshell the two "handle" it differently in that a transformer won't pass DC thru to the load but sand will.

  • Like 1

Share this post


Link to post
Share on other sites

Here is some info from two folks on the forum I respect.Unfortunately, Dennis has passed away.

 

From DJK:

It's not the clipping per se that damages the speaker, but the clipping frequently causes amplifier stability issues in the feedback loop that can cause damage (excessive cone motion from infrasonics). Tweeters burn up from excessive long term average power, not clipping.

*************************************************************************************************************************************************
 

"If your getting distortion or clipping, yes that is very bad for your speakers."

An urban myth.

Two things ruin speakers, too much long-term average power, and mechanical damage from over-excursion.

Unless the distortion or clipping cause either of the above two, your speakers will not be harmed.

Anyone that wants to argue will have their head handed to them when I am done with them, search for my

previous explanations as to why this is a myth.

**************************************************************************************************************************

Amplifier clipping causes no damage what so ever, unless you exceed the long term average power limit of the driver, or it causes mechanical damage.

 

Clipping below 40mS in duration is generally inaudible to the average person.

 

The APT Model 1 had an indicator labled 'distortion alert', it would flash if the duration of the clipping was in excess of 40mS. A Peavey with DDT (distortion detecting) will go into limiting when the duration of the clipping exceeds 100mS. The Dynaco Dynaguard had a delay that was dependent on the overdrive applied, but would allow clipping for tens of mS before pulling back the average power leve (user programable).


From JohnA:

 I believe clipping gets blamed because clipping is so often involved, but the real problem is the average power levels are too high.  A clipped amp will be putting out a lot of average power, something like a compressed track.  Add the HF required to create (created by) that square topped clipped off wave and the tweeter gets a double shot of energy.

 

Van Halen's "Runnin' With The Devil" has a square wave generator applied to the guitar.  This was my first clue that a clipped amp sounded worse than it was damaging.  Square waves are found often enough in music that a speaker should be able to tolerate them.


And a very long piece from 2014 by DJK... (I really miss this guy):

"I am interested from the academic point of view. Also i might require to make for 2" compression driver. This will also increase my knowledge about the subject. "

"I am also waiting 4 ur details/new thread about the klipsch protection circuit"

OK, let's keep on with it here for a while.

Drivers fail for two reasons:

Excess average power
Mechanical damage

Clipping will not hurt anything if it does not cause the above problems.

After larger amplifiers (above 50W) became common, problems with high frequency units self-destructing became a problem.

A tweeter like the EV T35/Klipsch K77 could handle 5W continuous, 50W for 10mS peaks, so normal program material wasn't the problem.

The tweeters were dieing from mechanical failure. The voice-coil was wound with aluminum wire that ran out to the terminals on the frame (self-termination). Shallow slopes in typical crossovers (6dB) combined with higher drive levels produced failures. Copper wire was tried instad of aluminum (aluminum work-hardens in a very short time).

Still, the failures continued.

Klipsch switched to the 18dB crossovers in the very early 70s. This helped with the excursion failures.

Now, 100W+ amplifiers became common.

Klipsch went to cathode-to-cathode connected zener diodes. These clipped off the peaks that were mechanically destroying the tweeters. Things went well for about ten years.

In the early 80s it was time to try and get rid of the expensive band-aid (the zener diodes). EV changed the lead-out wire from the self-terminated copper voice-coil wire to a flat BeCu wire like used on expensive JBL and Altec type compression drivers. A new network was designed with an elliptical filter with 50dB of attenuation only a half-octave away from the crossover point. A fast- acting instrumentation fuse was added.

Problem solved?

The new version of the tweeter used a UV cure adhesive vs the old thermo-set adhesive. After the fuses blew from modern program material (about the same time as the introduction of the CD), they got replaced with fast-blow types (which offered reduced protection). The special instrumentation types were very expensive, and very hard to find.

The new UV cure adhesive got soft, bubbled, and failed quite easily.

A PolySwitch was tried. Too slow.

The old thermo-set adhesive came back.

The combination of the super-steep crossover, the flat BeCu lead-out wire, and the PolySwitch seemed to work (with the old adhesive).

The zener diodes were retired for mainly two reasons: cost, and limited dynamic range. The AA networks used a pair of 5.1V 10W zeners. These only allowed about 2W RMS through before they started clipping off the peaks (a 4W peak square-wave) .

With the advent of digital program material, 2W of undistorted program material no longer seemed adequate (about 97dB at 10 foot). The zeners limited the maximum distorted output to about 100dB at 10 foot.

Removal of the zeners allowed exploitation of the 50W/10mS rating of the tweeter, about 14dB more output capability (referenced to the 2W RMS zener clamp).

What did EV do for products sold under their brand?

The STR tweeter protector was developed for this use. Later it was modified by adding a lightbulb in parallel with the relay contacts.

I hope this give a little insight into what is needed for tweeter protection, and how we got to where we are.

Vifa, Dynaudio, and others offer a choice between self-terminated tweeter lead-outs and a braided (or tinsel) type lead-out.
The difference in cost for the braided type is worth it in my book. Most manufacturers of lower-priced product do not spend the money for this, or better crossovers either (although I am seeing lighbulbs and/or PolySwitches in some inexpensive product).

Crossovers and tweeters must be designed to avoid mechanical damage in normal use (correct slope, frequency, and lead-out wire for the intended use).

Long-term thermal protection is worthwhile. Some sort of switch device (relay, PolySwitch, fuse) in conjuction with a lightbulb seems to be the most cost-effective. Due to the long time constant of lightbulbs, most use does not seem to demand the switch (which shorts out the lightbulb in normal use).

Suggested current levels:

For 1" coils (tweeters), about 1A. The 561 or 211-2 automotive lamp has worked well in this application.

For 1-3/4" coils (1" compression drivers), about 2A. The 1156 type automotive lamp has worked well in this application.

For 3" (kapton) to 4" (nomex) coils (2" throat 16 ohm compression drivers), about 2A. I have found a 1.5A AGC (or 3AG) type fast-blow fuse will pass 400W of program material in normal use, and blow almost instantly if bad feedback is encountered. A pair of 1156 automotive lamps wired in series with each other, and then wired in parallel with the fuse will allow the show to go on when the fuse blows, and still offer some protection. If the fuse blows in the course of normal use, you need additional HF drivers, horns, and amplifiers.
__________________
Candidates for the Darwin Award should not read this author.

"As for using a L pad attenuator the idea of this is to maintain the same Resistance - Impedance as the Driver ie 8R0 to allow the crossover components to correctly filter the frequency. So how does this increase the loading? "

Is this a trick question?

It would seem obvious that the size of the lightbulb would need to be changed for every different attenuation value (if it's to be of any use).

"So a 500W amplifier will deliver over 700W power to the driver if clipped hard enough."

Really? Power goes with the square of the voltage, so it goes from 500W to 1KW, but that has little or nothing to do with why the drivers blow.

Clipping can damage speakers, but not for the 'urban legend' reasons.

"If you’re getting the idea I don’t believe in the clipping/
harmonic theory, you’re right. So let’s investigate the
phenomena further.
WHEN SINE WAVES CLIP
When sine waves clip severely they resemble square
waves in shape, introducing massive distortion. In the
extreme case, a perfect square wave has the highest level of
harmonic components (See Figure 1). A less clipped sine
wave has components at the same frequencies but at lower
levels.
Let’s look at the square wave example shown in Table 1
(at left). Fourier analysis shows the harmonic structure.
As you can see, the total amount of instananeous power
left to make it through an ideal 1kHz crossover (and on to the
tweeter) is less than two watts (0.83 + 0.589 = 1.419W).
Hardly a problem. And remember, this simulates severe
overdrive of a 100 watt amplifier with a sine wave to make an
ideal square wave. Driving it harder will not increase the
harmonics.
This analysis shows if a small tweeter that only handles 5
or 10 watts is used in a 100 watt speaker system it would not
blow out, even under square wave conditions. Yet it does.
It takes a lot more than this to cause major failure. "

Consider a worst case situation, an amplifier overdriven by 10dB or so.

The bass content of the program material causes the amp to clip, the excess HF content from clipping harmonics fed to the tweeter is trivial.

However, the average level fed to the speaker at mid and high frequencies is elevated as much as 10dB (due to the input overdrive) during non-clipped passages.

WOOFER MECHANICAL DAMAGE
(assume the design has sufficient x-max for in-band signals)

It's not the clipping per se, but the poor design of the amplifier causing this. The pole in the feedback loop is generally poorly chosen and lower in frequency than the input pole, and above the power supply/load pole, so the poorly designed amplifier pumps out rail-to-rail signals at the feedback pole every power supply time constant. Good design reduces or eliminates this problem (although it seems like 99% of amplifiers have this problem).

The easiest way to fix this is to change the poles so the feedback pole is at a higher frequency than the power supply pole, and the input pole is higher than the feedback pole. It also helps to put clamp diodes across the feedback cap.

Another way to fix this is to put an input clipper on the amplifier. NAD amplifiers have this kind of a circuit (they call it 'soft clipping') and it tracks the supply voltages so you get the maximum power the amplifier is capable of. Since the input clips before the feedback loop clips, it's always stable. I used to put 50W NAD amplifiers in clubs with four Klipsch Heresy on them, you wouldn't believe how loud this combo will play driven a few dB into clipping.

"2) Many crossovers barely handle the rated power of a speaker system, let alone the effect of a clipping amplifier. When inductors saturate, the tweeter gets not only the normal signal at high power, plus the distortion products from the clipping, but also back EMF from the saturating inductors and signals below the normal crossover frequency because the filter system in overload."

Only the cheapest of speakers use low quality parts these days. Back-in-the-day a network needed the tweeter cap replaced (if it was an electrolytic) or the tweeter inductor (if the tweeter cap was a film type) after the tweeter burned out and the operator continued to play the system. In 30 years I can pretty much count on one hand the woofer inductors that failed in hi-fi use, these all developed shorted turns (causing damaging infrasonic woofer excursions). In pro sound I saw quite a few woofer inductors fail from too high of a DC resistance (causing the insulation to burn off the wire and the inductor to short out).

The last KW is the most important, how it behaves at the limit.
A well behaved amplifier with no dynamic off-set when driven 6dB into clipping sounds much better than a wimp amp with a built in limiter, even if it is twice the rated power.

(This is tiresome as I have explained it many times before. The above was a compilation of many old postings of mine, I hope it is intelligible)
__________________
Candidates for the Darwin Award should not read this author.

 

 

 

  • Like 3

Share this post


Link to post
Share on other sites
8 minutes ago, Marvel said:

Tweeters burn up from excessive long term average power, not clipping.

That is false.  So he is saying if you have a 5 wpc and input that into say a pair of 88 dB sensitivity speakers that the tweeters won't blow because they didn't receive "excessive long term average power, not clipping."  BS

  • Like 1

Share this post


Link to post
Share on other sites

If you have a throw away pair or speakers, try it for yourself.   I have intentionally done this with a couple buddies when they made the same argument.   Those tweeters didn't last long.... But what do I know. 

  • Haha 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...