Blastin...
Just my two cents here...
I looked up the KEF in question & the NAD 2200 and I think you really are asking a bit too much out of these speakers as they would seem to be not quite suited to your style of music..
First you'll note the KEF has just 92 db of sensitivity, panned out to 128 watts worth your only getting 112 db of sound level pressure.
The NAD is only rated at 100W RMS...sure they make a big deal of their "power pushing " circuitry....but the very bottom line is still just 100W!
The generally accepted level of "concert level" db is 115 db....the KEF is rated at 113 db MAXIMUM......a db level beyond that is searching for a weak link in the system....& it would appear the tweeter is that weak link.
Apart from tinkering with your KEFs' I would suggest you find a speaker with a truely high sensitivity...Cerwin Vega has their E-715 boxy type speaker that is rated at an unbelievable 102 db per watt...drawn out that comes out to 123 db at 128 watts.
Prepare to get complaints from not only the neighbors but the whole neighborhood.
Perhaps the KEFS' could be relocated to another room where they can take a breather & reproduce some kindler gentler type sound.
___________________________________Rick.......
Just my two cents here...
I looked up the KEF in question & the NAD 2200 and I think you really are asking a bit too much out of these speakers as they would seem to be not quite suited to your style of music..
First you'll note the KEF has just 92 db of sensitivity, panned out to 128 watts worth your only getting 112 db of sound level pressure.
The NAD is only rated at 100W RMS...sure they make a big deal of their "power pushing " circuitry....but the very bottom line is still just 100W!
The generally accepted level of "concert level" db is 115 db....the KEF is rated at 113 db MAXIMUM......a db level beyond that is searching for a weak link in the system....& it would appear the tweeter is that weak link.
Apart from tinkering with your KEFs' I would suggest you find a speaker with a truely high sensitivity...Cerwin Vega has their E-715 boxy type speaker that is rated at an unbelievable 102 db per watt...drawn out that comes out to 123 db at 128 watts.
Prepare to get complaints from not only the neighbors but the whole neighborhood.
Perhaps the KEFS' could be relocated to another room where they can take a breather & reproduce some kindler gentler type sound.
___________________________________Rick.......
Re: Re: Nad 2200 falling into protection, burning my tweeters.
Don't install more tweeters. Doing so will totally throw off the balance of sound of the loudspeakers as well as the HF polar response... You also have to maintain the overall tweeter impedance to that of a single unit if you want your crossover network to work correctly. Too much trouble, IMHO.
As AndrewT has posted, do away with the bridged-mode drive; perhaps bypass the equalizer for the moment and give it a good listen (of course after putting in new tweeters... 🙂 )
Cheers!
Hemiguy said:
Don't install more tweeters. Doing so will totally throw off the balance of sound of the loudspeakers as well as the HF polar response... You also have to maintain the overall tweeter impedance to that of a single unit if you want your crossover network to work correctly. Too much trouble, IMHO.
As AndrewT has posted, do away with the bridged-mode drive; perhaps bypass the equalizer for the moment and give it a good listen (of course after putting in new tweeters... 🙂 )
Cheers!
The 100 watt rating of the 2200 is the FTC power rating at 8 ohms. 400 watts (20 Hz to 20 kHz) at 8 ohms bridged.
According to the brochure:
"Reproducing musical signals, the NAD 2200 routinely delivers over 500 watts per channel into typical loudspeaker impedances.
In actual measurement with speakers of complex impedance and lower-than-average sensitivity, the 2200 produces peak sound pressure levels exceeding 115 dB SPL(Sound Pressure Level) in a medium to large room, with no audible or measurable distortion."
It would be interesting to take the equalizer out; maybe that's adding some (too much) gain, or you've got it set inappropriately.
I wonder if adding a couple of subwoofers wouldn't beef up the bottom end and provide a more satisfactory feeling of loudness.
(and if anyone has a copy of the 2200 service manual or schematic to share, please PM me)
(and if there are any rules-of-thumb for lightbulb types to use on larger compression drivers?)
According to the brochure:
"Reproducing musical signals, the NAD 2200 routinely delivers over 500 watts per channel into typical loudspeaker impedances.
In actual measurement with speakers of complex impedance and lower-than-average sensitivity, the 2200 produces peak sound pressure levels exceeding 115 dB SPL(Sound Pressure Level) in a medium to large room, with no audible or measurable distortion."
It would be interesting to take the equalizer out; maybe that's adding some (too much) gain, or you've got it set inappropriately.
I wonder if adding a couple of subwoofers wouldn't beef up the bottom end and provide a more satisfactory feeling of loudness.
(and if anyone has a copy of the 2200 service manual or schematic to share, please PM me)
(and if there are any rules-of-thumb for lightbulb types to use on larger compression drivers?)
The light bulb is sized to match the wattage rating of the tweeter driver. Very simple procedure that requires the use of a signal generator, amplifier, bulb in question and a good meter. Some large format high frequency drivers are 60 watt. You pick a bulb that will allow 60 watts and will be turned on at 60 watts. Thus it serves to clamp the voltage and allows no more. The end result is a very efficient limiter and no more burned out tweeters. For some of us in the field that have to repair the broken tweeter this is a godsend because we don't have to waste a day setting up scaffolding to get a an array to repair the broken/burned drivers.
For those that question the effect of this on the high frequency program....I have plotted the before and after responce of this and there is a very slight dip in the responce of about 1db at the upper region. Very small price to keep things together and running.
I guess I missed the part where the amplifiers were in bridge mode and an EQ was being used.
One must remember the EQ is used in order to make the frequency responce flat. Test equipment must be used in order to properly EQ a system. In other words "Pink Noise" and a good analyzer. Not to be set with ones calibrated set of ears.
One must remember the EQ is used in order to make the frequency responce flat. Test equipment must be used in order to properly EQ a system. In other words "Pink Noise" and a good analyzer. Not to be set with ones calibrated set of ears.
Hi,
I don't believe this,
A bridged amp pushes twice the power into twice the impedance. (for impedance read resistance).
the 400W into 8r means they are claiming 200W into 4r.
If this were true then they are also claiming that their ClassAB ampilfier has a perfect delivery of constant voltage into loads ranging from 8r down to 4r. That is impossible with conventional circuitry.
Taking the 400W into 4r claim and extrapolating it to a non approved 2r load would imply 800W and into 1r 1600W. This is completely impossible from that model of NAD.
I think this again confirms that bridging is to blame for all these problems.
It appears to be an installation and operator fault, not the equipment. When sense prevails come back with some updated observations.
I don't believe this,
some marketing guy/woman is telling lies.
A bridged amp pushes twice the power into twice the impedance. (for impedance read resistance).
the 400W into 8r means they are claiming 200W into 4r.
If this were true then they are also claiming that their ClassAB ampilfier has a perfect delivery of constant voltage into loads ranging from 8r down to 4r. That is impossible with conventional circuitry.
Taking the 400W into 4r claim and extrapolating it to a non approved 2r load would imply 800W and into 1r 1600W. This is completely impossible from that model of NAD.
I think this again confirms that bridging is to blame for all these problems.
It appears to be an installation and operator fault, not the equipment. When sense prevails come back with some updated observations.
Hi,
I had this amp about ten years ago, a fairly good amp. Never blew speaker except if they could not handle the power. Amp Operating in some Class H topology or in NAD language PE, Power Envelope. I have service manual somewhere.......
Although I found this:
http://207.228.230.231/info/NAD_2200.pdf
Edit:
I would not load it lower than 4Ohm stereo, 8 Ohm bridged to be safe.
I had this amp about ten years ago, a fairly good amp. Never blew speaker except if they could not handle the power. Amp Operating in some Class H topology or in NAD language PE, Power Envelope. I have service manual somewhere.......
Although I found this:
http://207.228.230.231/info/NAD_2200.pdf
Edit:
I would not load it lower than 4Ohm stereo, 8 Ohm bridged to be safe.
Hi,
i remember reading that NAD literature when I was nearly a youngster, but just past the impressionable stage.
I have now learned how amplifiers work.
I have re-read the specification on p5 of that PDF.
It tells me the amp is garbage, Some will disagree, vehemently.
They are making their name by emphasing dynamic headroom to the exclusion of all else. I believe dynamic headroom is the opposite of good sound.
+5db dynamic headroom is attrocious.
+1db of extra power going from 8r to 4r is attrocious.
The thread starter has been impressed by the big numbers and has been misled into thinking that bigger is better (it's that dynamic headroom again). So he thought let's help it along and bridge it, the figures show it is better. Well it doesn't work that way.
If only it could source that 50Apk figure quoted into 1r.
It might just have tried to pass as an amplifier suitable for driving paralleled 104/2s but that peak is very short and even if it could that would amount to 2500W, where would that come from, telepathy?
i remember reading that NAD literature when I was nearly a youngster, but just past the impressionable stage.
I have now learned how amplifiers work.
I have re-read the specification on p5 of that PDF.
It tells me the amp is garbage, Some will disagree, vehemently.
They are making their name by emphasing dynamic headroom to the exclusion of all else. I believe dynamic headroom is the opposite of good sound.
+5db dynamic headroom is attrocious.
+1db of extra power going from 8r to 4r is attrocious.
The thread starter has been impressed by the big numbers and has been misled into thinking that bigger is better (it's that dynamic headroom again). So he thought let's help it along and bridge it, the figures show it is better. Well it doesn't work that way.
If only it could source that 50Apk figure quoted into 1r.
It might just have tried to pass as an amplifier suitable for driving paralleled 104/2s but that peak is very short and even if it could that would amount to 2500W, where would that come from, telepathy?
Hi, AndrewT
I do not diasagree.....
I do beleave that a real good amp has the same power, dynamic and static.
I do not diasagree.....
I do beleave that a real good amp has the same power, dynamic and static.
Gee Andrew,
I have a little amp with +3 dB headroom with 8R loads rating. It is a very good amp. Marantz 300DC. The voltage amps sections have regulated supplies.
You can't count on specs either way.
-Chris
I have a little amp with +3 dB headroom with 8R loads rating. It is a very good amp. Marantz 300DC. The voltage amps sections have regulated supplies.
You can't count on specs either way.
-Chris
Hi,
Treat it as a 2 x 100W amp, ignore the dynamic commercial and it's a fair amp.
It will also handle bridged 8 Ohm with ease, if great interest I can get hold of one 2200 amp and measure its power bridged (static).
Treat it as a 2 x 100W amp, ignore the dynamic commercial and it's a fair amp.
It will also handle bridged 8 Ohm with ease, if great interest I can get hold of one 2200 amp and measure its power bridged (static).
Unlike most of you, I was an authorized service center.
"It tells me the amp is garbage, Some will disagree, vehemently."
I suggested he dump the amp in the first reply that anyone made. They are kind of a POS.
"The 100 watt rating of the 2200 is the FTC power rating at 8 ohms."
It will honest to god drive 360W at 8 ohms on a sine wave at 400hz for about one second (until the polyswitch open up and shuts down the 95V rails). On an IHF tone burst it will do well in excess of 800W at 4 ohms (160V P-P).
The KEF 104.2 is rated at 200W into its 4 ohm nominal impedance.
The KUBE 200 has a treble boost if you choose to use it. Most of the boost is to extend the bass.
As a dealer of many high end brands at the time, I must point out that there were more efficient speakers that measured flatter, sounded better, and were half the price. KEF was a very hard sell.
"It tells me the amp is garbage, Some will disagree, vehemently."
I suggested he dump the amp in the first reply that anyone made. They are kind of a POS.
"The 100 watt rating of the 2200 is the FTC power rating at 8 ohms."
It will honest to god drive 360W at 8 ohms on a sine wave at 400hz for about one second (until the polyswitch open up and shuts down the 95V rails). On an IHF tone burst it will do well in excess of 800W at 4 ohms (160V P-P).
The KEF 104.2 is rated at 200W into its 4 ohm nominal impedance.
The KUBE 200 has a treble boost if you choose to use it. Most of the boost is to extend the bass.
As a dealer of many high end brands at the time, I must point out that there were more efficient speakers that measured flatter, sounded better, and were half the price. KEF was a very hard sell.
Member
Joined 2002
I am saying I wouldn't own one for a couple of different reasons:
1)I've seen too many 2200s that I had to fix
2)I think they sound bright with no real high end
They play quite loud, but they just tore up a lot of woofers in many different speaker brands and models that we sold.
The 7220PE was the real problem one in the same time frame. The failure rate on thoses was almost 100%. Don't even get me started about that one.
If you own one, like it, and it still works, more power to you.
1)I've seen too many 2200s that I had to fix
2)I think they sound bright with no real high end
They play quite loud, but they just tore up a lot of woofers in many different speaker brands and models that we sold.
The 7220PE was the real problem one in the same time frame. The failure rate on thoses was almost 100%. Don't even get me started about that one.
If you own one, like it, and it still works, more power to you.
Member
Joined 2002
djk said:
Ill repeat 🙂
I had one used it to drive some subwoofers with a active x-over on it. Was a grunt amplifier and worked very well ran it also with a pair of 15 watt speakers never had problems. Then after that ran a 15" sub-woofer off it in bridged mode. Then sold it to dad for the Phase-Linear Amp that i miss alot.
djk,
And after that second, how much power then running on lower rail?
Btw, contacted current owner of my old amp and the 2200 still runs fine. I now really must borrow the amp and measure.
And after that second, how much power then running on lower rail?
Btw, contacted current owner of my old amp and the 2200 still runs fine. I now really must borrow the amp and measure.
That seems like the protection operating that I referred to earlier.djk said:
What kind of output ends up in the speaker when the rails shut down? Is it spikey, or rail to ground pulses or rail to rail ringing or some other transient rubbish that could blow tweeters? Certainly if the gain was set to produce all that output voltage initially then the clipping of the signal after that polyswitch was activated would increase the distortion enormously. That clipping distortion would be sent to the tweeter by the passive crossover and will virtually guarantee to blow a HiFi tweeter (whether a PA tweeter could survive this is impossible for my limited experience to judge).
Why anybody who is familiar with live music would continue to drive speakers with this kind of distortion on the output is completely beyond my comprehension. Even someone only familiar with clean music signals would recognise something was not right.
Pity the dealers/manufacturers did not emphasise the importance and relevance of doubling the impedance when bridging. When bridged a 200W into 4r two channel amplifier becomes a 400W into 8r mono amplifier.djk said:
But as rightly pointed out by another poster earlier, those 200W + 200W into 4r are exactly the same as the 400W when used in two 4ohm speakers, whether they are driven separately or in series.
The problem still appears to be the bridging and load paralleling giving a result that had no hope of being successful.
The Dealer should hang his head in shame.
The enquirer should have researched his problem twenty years ago, BEFORE he bought the second set of 104/2s since he was getting inadequate support from his supplier.
Hemiguy, you too should hang your head in shame at your lack of proactive response.
Hemiguy, you have gone quiet, are you re-wiring your set-up to find the correct way of doing it?
The idea of the 6dB headroom NAD amps is that under most dynamic music conditions the polyfuse should not trip and therefore it should not be an issue. However, I've used similar Proton equipment, and there are situations where the amp runs out of steam, long heavy bass lines for example. It does work well most of the time, not for an ultimate system though IMO.
I wonder, hemiguy if you've got the speakers phased properly as you tried different series parallel arrangements, this is important.
Let me draw an analogy here, think of clipping as red line on a motor. You really want to stay out of clipping, especially if you have a tweeter that's known to be fragile. When you see the clip lights flicker, don't go any higher no matter what number your on on the volume control.
I used to be into Alfa Romeos for some time. Most of the motors redlined at a bit over 6000 RPM and I believe that they were designed with a 1000 RPM safety margin. Many sport drivers found it fun to pin the tach at 8000 RPM, and you didn't often hear of blown motors since they were double overhead cam. I didn't do this by the way since the horsepower rolls off above read line, doesn't really make sense. Try this on a stock motor with pushrods and hydraulic lifters. You'd probably end up with bent valves and perhaps holes in your pistons. KEFs are known for quality but less so for robustness.
KEFs are designed for acuracy and less so power handling, they're gentleman's speaker, if you told a high up at KEF about your problem they'd probably say don't play them so loud. I've blown out KEF drivers myself.
However, the more I look at designs, even very good ones, the more I see that it is more common for there to be at least a few design issues. One common one is for crossover inductors to be poorly placed which causes coupling between them. This often goes unseen by the designers since you have to look 30 dB or more down in the stop band to see it. This is just a possibility where bass or midrange energy may be leaking into the tweeter's stop band causing excessive excursion and burn out.
A crossover schematic and photo would help if you'd like us to take a look.
Also, you mention that these speakers are over 20 years old and they're due for new capacitors if any are electrolytic. Electro's really shouldn't be trusted after about 10 years. You wouldn't want a bad cap to take out an expensive hard to find driver.
Pete B.
I wonder, hemiguy if you've got the speakers phased properly as you tried different series parallel arrangements, this is important.
Let me draw an analogy here, think of clipping as red line on a motor. You really want to stay out of clipping, especially if you have a tweeter that's known to be fragile. When you see the clip lights flicker, don't go any higher no matter what number your on on the volume control.
I used to be into Alfa Romeos for some time. Most of the motors redlined at a bit over 6000 RPM and I believe that they were designed with a 1000 RPM safety margin. Many sport drivers found it fun to pin the tach at 8000 RPM, and you didn't often hear of blown motors since they were double overhead cam. I didn't do this by the way since the horsepower rolls off above read line, doesn't really make sense. Try this on a stock motor with pushrods and hydraulic lifters. You'd probably end up with bent valves and perhaps holes in your pistons. KEFs are known for quality but less so for robustness.
KEFs are designed for acuracy and less so power handling, they're gentleman's speaker, if you told a high up at KEF about your problem they'd probably say don't play them so loud. I've blown out KEF drivers myself.
However, the more I look at designs, even very good ones, the more I see that it is more common for there to be at least a few design issues. One common one is for crossover inductors to be poorly placed which causes coupling between them. This often goes unseen by the designers since you have to look 30 dB or more down in the stop band to see it. This is just a possibility where bass or midrange energy may be leaking into the tweeter's stop band causing excessive excursion and burn out.
A crossover schematic and photo would help if you'd like us to take a look.
Also, you mention that these speakers are over 20 years old and they're due for new capacitors if any are electrolytic. Electro's really shouldn't be trusted after about 10 years. You wouldn't want a bad cap to take out an expensive hard to find driver.
Pete B.
Nad/Kef
Thanks PB2 and all the others.
PB2, I really like the way you wrote about the problem of my situation, (unmatching components). This is the way I explain to my hot rod customers who aren't experts in mechanic. I will never tell them that they are idiots if they can't repair an engine like me.
I see a lot I will do, like probably listen to music at lower levels and I will probably sell my system and purchase a more heavy duty.
Thanks so much.
Thanks PB2 and all the others.
PB2, I really like the way you wrote about the problem of my situation, (unmatching components). This is the way I explain to my hot rod customers who aren't experts in mechanic. I will never tell them that they are idiots if they can't repair an engine like me.
I see a lot I will do, like probably listen to music at lower levels and I will probably sell my system and purchase a more heavy duty.
Thanks so much.
"And after that second, how much power then running on lower rail?"
About 150W/8R midband. About ±65V on the lower rails.
"The idea of the 6dB headroom NAD amps is that under most dynamic music conditions the polyfuse should not trip and therefore it should not be an issue. However, I've used similar Proton equipment, and there are situations where the amp runs out of steam, long heavy bass lines for example. It does work well most of the time, not for an ultimate system though IMO."
That's pretty much how it is. With normal music the only real problem with this amp was the speaker relays got intermittent. With 4R speakers and the heavy bass demands of dance type music it was a different story.
The amp could do some real damage to 100W speakers because it had so much headroom. It really should be viewed as a 400W amplifier from the speakers' view point.
"Is it spikey, or rail to ground pulses or rail to rail ringing or some other transient rubbish that could blow tweeters? "
I didn't see HF stuff. The amp did have a Baker clamp between the second voltage amp and the current gain stages. The front end ran off the higher voltage, and the shut down was only on the output stage.
Most of the speaker damage was to woofers, that amp would tear the voice-coil right off the apex of the cone (on certain popular speakers). The ESP site talks about what looks like DC off-set when an amp is driven hard with a long asymetrical signal. The top rail shutting abruptly off seemed to make this worse. Watching the motion of the speaker cone would show motion at what looked like the time constant of the cap in the feedback loop and the lower arm resistor.
The 'soft clipping' on the PE models was quite complicated as it had to track the jump in the supply rails.
The sales people really pushed this model originally. Because of the high headroom it would play much louder than the other 100W amps. Easy to see why, it ran on ±95V on the top rails vs ±55V on an Adcom GFA 545.
Speaker problems showed up right away, and the NAD 2200PE popularity with the sales people waned. Later on we saw some amplifer problems, the most frequent being the intermittent relays (previously mentioned).
The non-PE model 50W amplifier was a workhorse. We put a lot of those in clubs that pushed it to the limit all night long driving two pair of speakers. No problem with either the amps or the speakers.
The 'soft clipping' feature on these is actually a hard clip on the input of the amp. Nothing soft about it (the large value caps are there to prevent DC level shifts from disturbing the input bias of the amp) . The idea is to prevent the amp from clipping by pre-clipping the input signal. Outputs 'sticking' to the rail when coming out of clipping, subsonic pulses (see the ESP reference) don't show up when the feedback loop of the amp does not clip.
Clipping pe se doesn't hurt the speaker. The increase in average power may destroy the tweeter, exactly the same way a very large amplifer that is not clipping will do. The woofer can be destroyed from either average power, or mechanical damage. Most of the time it is the mechanical damage.
About 150W/8R midband. About ±65V on the lower rails.
"The idea of the 6dB headroom NAD amps is that under most dynamic music conditions the polyfuse should not trip and therefore it should not be an issue. However, I've used similar Proton equipment, and there are situations where the amp runs out of steam, long heavy bass lines for example. It does work well most of the time, not for an ultimate system though IMO."
That's pretty much how it is. With normal music the only real problem with this amp was the speaker relays got intermittent. With 4R speakers and the heavy bass demands of dance type music it was a different story.
The amp could do some real damage to 100W speakers because it had so much headroom. It really should be viewed as a 400W amplifier from the speakers' view point.
"Is it spikey, or rail to ground pulses or rail to rail ringing or some other transient rubbish that could blow tweeters? "
I didn't see HF stuff. The amp did have a Baker clamp between the second voltage amp and the current gain stages. The front end ran off the higher voltage, and the shut down was only on the output stage.
Most of the speaker damage was to woofers, that amp would tear the voice-coil right off the apex of the cone (on certain popular speakers). The ESP site talks about what looks like DC off-set when an amp is driven hard with a long asymetrical signal. The top rail shutting abruptly off seemed to make this worse. Watching the motion of the speaker cone would show motion at what looked like the time constant of the cap in the feedback loop and the lower arm resistor.
The 'soft clipping' on the PE models was quite complicated as it had to track the jump in the supply rails.
The sales people really pushed this model originally. Because of the high headroom it would play much louder than the other 100W amps. Easy to see why, it ran on ±95V on the top rails vs ±55V on an Adcom GFA 545.
Speaker problems showed up right away, and the NAD 2200PE popularity with the sales people waned. Later on we saw some amplifer problems, the most frequent being the intermittent relays (previously mentioned).
The non-PE model 50W amplifier was a workhorse. We put a lot of those in clubs that pushed it to the limit all night long driving two pair of speakers. No problem with either the amps or the speakers.
The 'soft clipping' feature on these is actually a hard clip on the input of the amp. Nothing soft about it (the large value caps are there to prevent DC level shifts from disturbing the input bias of the amp) . The idea is to prevent the amp from clipping by pre-clipping the input signal. Outputs 'sticking' to the rail when coming out of clipping, subsonic pulses (see the ESP reference) don't show up when the feedback loop of the amp does not clip.
Clipping pe se doesn't hurt the speaker. The increase in average power may destroy the tweeter, exactly the same way a very large amplifer that is not clipping will do. The woofer can be destroyed from either average power, or mechanical damage. Most of the time it is the mechanical damage.
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