Easy Does It

[Mighty Favog]

I have a set of KLF-20's that are about three weeks old. So far I've replaced one tweeter diaphragm and just ordered another one today for the same problem (blown). I realized just after blowing the first tweeter that I had the eq settings way too high so I ran the receiver flat and the eq about +1 to +2db. I also understand that the high frequencies are really bright when they're new and takes about 100 hours of playing to settle down. My question is, during that break-in period should they only be played at low volumes till the break-in is complete? The receiver is 150wpc and it never got above the 10 o'clock position. I found the second tweeter (same channel) was not producing like it was a few days earlier when I got home from work and my girlfriend was playing a Thirty-Eight Special cd where the signal from the disk seemed rather strong and constant. Please no flames about using an eq with set up. So, should the 20's be babied till they break in?

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Tom

KLF-20 Mahogany

Carver Receiver MXR-150

Yamaha PF-800 Turntable/ Sure V15 Type V Cartridge

Carver TL-3100 CD

Yamaha K-1020 Cassette

dbx 1231 EQ

dbx 3bx Series Two

H.H. Scott 830z Analyzer

Monster Interlink 300 mk II

Original Monster Cable

[pzannucci]

Usually the first things to go when you are clipping (especially likely with an eq) is the tweeters. Sounds like you are going beyond where the amplifier can push the tweeters. With no ACCURATE means of telling how much power is being put out in that frequency range (volume control doesn't cut it since every amp/pre has different gains), clipping would be my guess. I could run myself out of the room with my KLF-30s. Never a hint of distress (except for my ears ).

Peter Z.

[Mighty Favog]

I think I have found a few other settings that have been giving it hell, the 3bx is set for about 20% expansion so that could be adding some db's to the total (I may have to mothball it all together after this). The receiver just came back from the authorized Carver service center (Everett Audio Repair) and still seems to play (all settings being equal)slightly quieter on one channel so I increased the gain to that channel about 1db. Yea, I know, red warning lights and sirens should be going off because I'm now up to about +3 to +4db on that channel. I may just tweak the balance though I really don't feel I should have to. See if any of this sounds like a source of damage, when I turn off the receiver it produces a disturbing "pop" that sounds just like a static ground if you walk across carpet and touch system. I'm assuming it's a spark that's occurring between contacts inside the power switch. Thought of a couple ways to stop this. I could either turn off the speakers first THEN turn off the amp or this next possible solution which I think may be adding to troubles. I have an outlet strip plugged into the outlet on the receiver and all the other equipment is plugged into that strip. I may unplug all that from the receiver and plug the receiver into the strip and the strip to the wall. Later I would like to get a Monster Cable HTS-500 line conditioner. Sound viable?

[Guest BobG]

The turn-off pop, while inelegant is not going to hurt your speakers - unless you hve the volume so high that the pop is really HUGE.

You do not have to baby the speakers during break-in but what you've done is at the opposite extreme. For every 3 Db of eq boost, you are asking your amp for twice the power at that frequency. When you had the eq boosted several Db with the receiver at 10 o:clock, you were most surely clipping. That's what toasted the diaphragms. Must've been pretty loud.

Reasonable use with a gentle hand on the eq will eliminate future failures. Remember that the eq always damages phase response while it changes amplitude response.

[Mighty Favog]

Thanks Bob,

Now that's the most useful piece of info I've gotten on here yet. So would a larger amp with more headroom be the ticket? I do have another question though. I understand about the double of power drawn for every +3db of eq BUT....is it true across the whole frequency range or just one frequency? What I'm getting at is that if I run the high and middle flat or with a cut of -1db to -1.5db and +2db on the bass end (125hz and under) is that still going to damage the high end and maybe the mids? The distortion according to the manual of the receiver doesn't seem to be that bad. Please look at the attachment above.

After the break-in is done do the drivers (twetter and mid) become more durable or do they just get a little quieter.

BTW: I talked to tech support today. Not sure who it was but it wasn't Trey. He was telling me the that the whole break in period was "Voodoo" and that they're plenty broken in at the factory. I' not saying who's right and who's not but just that there's a discrepancy and my hands are still up in the air on that one.

Thanks again,

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Tom

[Mighty Favog]

O.K. I've got some rough numbers. At about 10 o'clock volume position it's putting out about 102db (music playing at full frequency range) using I think between 2.6 and 3.1 watts. The wattage numbers are a little sketchy since the chart I referred to was intended for a speaker with 101db sensitivity and the KLF-20's are 100db. Is this making any sense?

[WMcD]

I am not a believer in this whole break in theory. It is nice to contemplate that a few cycles, or 10 or 100, or 1000, of movement will loosen up a suspension. But consider, a 10 kHz signal will put the suspension through 10,000 cycles every second. I can't believe that 10,000 cycles isn't plenty to loose up things properly. So one second of play should be plenty.

You should also realize that a tweeter just can't absorb much electrical power without burning out. PWK once wrote he hasn't found a tweeter worth its name that could take more than 5 watts continuous. Naturally, the Master is correct. The thin wires in the voice coil just can't take it.

The question should be, so how come speakers are rated at 100 watts or more.

The answer is that most music has most of the power distribution in the midrange. there is usually very little continuous power in the treble.

That may be changing. I've seen a real time analyzer running on pop music. At some times, the frequency distribution is full out across all ranges right up to the tweeter range, and for long periods. That is rare in orchestral music.

It is probably the case that you're hitting these speakers with too much power.

You have a good question along the lines of, why not cut down everything except the treble. My thought is that you just wind up running up the overall gain, and then you're pushing the tweeter again.

Like you said, take it easy. These are great speakers, but they can be driven to distruction.

Gil

[Mighty Favog]

Thanks Gil,

I've got an e-mail out to someone at Carver to see if they can tell me how much of the receiver's power is Class A if any. That may be a good starting point to tell if it's starting to clip or not.

[JohnA]

Your power figures won't be too far off IF you measured the SPL at 1 meter away. If you were 2 meters (10 feet) away, like my speakers are, the speaker is putting out 6 dB more SPL. 6 dB is 4 times the power required.

Clipping at any frequency adds huge quantities of harmonics (you have to add lots of highs to make a flat-topped, or clipped, wave). Many of those harmonics are in the tweeter's range, adding lots of power that shouldn't be there. So, a bass note at 125 Hz that's clipped can produce enough highs to kill a tweeter that can only absorb 2 watts continous. The tweeters in my La Scalas have been said to have several different power ratings, but 2 watts continuous comes up frequently.

I'll bet yours is the same. "No clipping Aloud"

John

[djk]

Go to an auto parts store and buy a pair of 561 dome light bulbs.Wire one in series with the hot lead of each tweeter.Don't bother with your class A question.It is meaningless.99% of solid state amps are class AB.The A part is usually 20mA or so of bias.Power is the square of current times impedance(.02*.02)*8=.0032W.If you were an engineer I would refer you to Douglas Self's site to read why class B amps have less distortion than class AB.

[Mighty Favog]

What am I supposed to look for with the bulbs attached? Am I to assume that the bulbs are just there to be an additional resistor to keep from blowing them?

More questions!!! I have the eq and the 3bx running through the same tape loop (respectively). Wish it had an external processor loop but..... Recently I had to clean the bypass switch on the dbx because it wouldn't play both channels when in bypass mode unless I played with it a few times. Could there be enough other dirt in there that would cause (for lack of a good connection) clipping at lower than expected levels. At this point I think they don't sound that great, that may change when the receiver gets fixed (bias gets re-centered) and the new tweeter gets put in (opposite side from week biased channel). Almost afraid to play'em. I'm at a crossroads where I can either put the eq in bypass so I can listen to them at the volume I want (not up to ten o'clock) OR I can engage the eq and get the tone I think is right (the extreme being +1.75 to +1.85db) but not turn the volume up hardly at all. I did a test yesterday and at .283 volts AC measured at the speaker terminal at 1 meter (all tone settings flat or disengaged and set on mono)the SPL measured 91db output. Could this mean that the room is absorbing 9db; the difference from the factory spec? The measurement was taken with th espeaker moved to the center of the room and no furniture around

[boa12]

dup

[boa12]

i remember bose for one doing that light bulb

thing on their 301 tweeters back in the 70s because they blew so easily. i would assume the 561 has the terminals for wiring or else you'd need the matching socket & terminals.

[JohnA]

The correct voltage is 2.83. 0.283 is 10 dB lower than 2.83. It looks like your speakers are spot on. Both the EQ and the 3BX can cause clipping in narrow ranges at SPLs that normally wouldn't cause alarm on a meter measuring average outout. I fried 4 sub drivers (at the same time) about the same way and paid a $400+ stupid tax for it. I didn't hear clipping and MAY have overpowered the drivers with my amp. It turns out it was capable ot that.

The bulbs are a variable resistor with power, the more power the more resistance they have. They have wire loops on each end making them easy to solder leads on. DJK has found a really neat, unobtrusive sonically, way to save your tweeters.

John

[Mighty Favog]

Thanks DJK!! I just got done doing that and John was right, I can't tell that their in there. I put'em in soldering one female spade connector to the bulb on the tweeter side and connecting the other end of the bulb directly to the positive lead. I didn't like the idea of using another the spade connector but I wanted to be able to undo this if I had to. Does this mean that the harmonics that are going to the tweeters are mostly inaudible? I'm sure they're gonna sound even better when the replacement tweeter comes. When I talked to Trey a couple days I was glad to hear that the midranges in these things are pretty stout, had a worry about that too. The bias is still off (barely audible but still annoying) and a friend is gonna research it for the adjustment. As it stands now with the volume at XXX level and set to mono (everything else flat) the left channel is measuring .126v/ac on the left and the right is .160v/ac. Everett Audio said they checked it twice but if they did why does lowly me get different readings? Hope he can help.

Doing this does send off a light bulb of an idea (bad pun!). The last set of speakers I had had an overload indicator on the front that had a small bulb that would flash with the peaks of power. Next to that was a small circuit breaker that I've only had to reset in 16 years. I guess this served a dual purpose to save the Heil tweeter. Sorry the rest of the speaker sucked.

[djk]

It is almost impossible to burn up a Klipsch midrange driver.If you are worried about it there are a couple of things you could do. A) 1156 lightbulb RXE090 Raychem PolySwitch from DigiKey C) 2.7 ohm 5 watt resistor in series with 1156 lightbulb with a RXE090 in parallel with this combo.The light bulb by itself works pretty good.The PolySwitch is basically a circuit breaker and the sound stops when tripped.If you parallel the PolySwitch with the resistor in series with the lightbulb the lightbulb is essentially shorted out by the PolySwitch under normal circumstances.Under a trip the PolySwitch opens up and the lightbulb is now in the circuit.The resistor is needed to make sure all the power goes through the PolySwitch during normal operation.The .126V/.160V is a 2dB difference.It is probably the tracking of the volume control.To rule out a real problem you should measure the balance at 40hz and again at 1Khz.If the 2dB is constant with frequency then I would just set the balance control and forget it.Cheap pots just don't track much better than this.If there is a big difference at 40hz there is something wrong with the amp and I can tell you how to fix it.

[Mighty Favog]

O.K. Here goes...

40Hz / 1KHz

Right .173v / .060v

Left .057v / .045v

Houston we have a problem...

Please tell me this is easy to fix. I yanked the 3bx out of the loop.

Thanks,

Tom

[jeffgeorge]

tblasting,

I think you may have a multiple problem. I can't speak to your receiver problems, but I have had extensive use of the DBX-3BX. Don't get me wrong, it is a nice piece of equip., but it can be very dangerous to speakers-especially with an eq. in the mix.

I have seen several tweeters fried due to the use of the DBX at relativley moderate volume levels. Some of these tweeters were other brands, but I have seen Heresy tweeters fried due to the use of these DBX units. They are great for boosting dynamics, but sometimes they cause more harm than good.

I would try taking the DBX out of the loop and see how things go. I missed mine for about two weeks, but soon got over it.

[Mighty Favog]

Thanks Jeff, I took it out of the loop two days ago. Since I got the the KLF-20's I've done nothing but worry and reach for the bypass button every time I changed from easy listening to something more upbeat. Your right though, I probably won't miss it. Just thinking of the $500 I paid new for this thing in 1984. Just waitin' for DJK do get back to me.

[djk]

You need to repeat the 40hz/1Khz test with the tone controls set flat and any eq bypassed and loudness off.I think I know what it is and it is cheap to fix.