-CGL- said:
Check page 9-10 in the thread "The problem with high fidelity".
http://www.diyaudio.com/forums/showthread.php?s=&threadid=120101
I have not done measurements on compression drivers, only on dome tweeters. My findings indicates strongly that what gedlee was claiming is false.
/Peter
I doubt that he has only tested two, but rather he probably limits the selection to specific price range. This would be very different for companies that have their own driver development criteria.Pan said:
Having auditioned the Dynaudio Evidence Master and the Saphire, I would expect better performance possible from the development efforts put forth. I like the overall tone balance of the Evidence Master much better, which is similar to what I am used to hearing from my own designs, but I would like better resolution of low level sounds. Sometimes I do wonder whether it is possible for such a large system. I also wonder how critical room size would be for optimum performance of speakers this size, because I have never thought of the Evidence Master as being very dynamic from the two audition sessions that I had. There is even a pair in a coffee shop in Taipei.
gedlee said:
Hi Earl,
How about this before you leave (although it may take several hours to appear as the censorship takes place - posted at 9:19am).
In the Klippel distortion test exactly what is it that I'm auralizing?
cheers,
AJ
"Appearantly he hasn't and that's why it's scientifically criminal to write the things he have.
You can not just test two drivers of different types and draw general conclusion from that. It's so obvious I shouldn't even need to mention it."
Hello Peter
I think your are missing the point. He seems to looking at from his application stand point and high spls. You can drive a compression driver at 120db @ 1 meter for hours at a time. You can't do that with a dome. Even if they had the same power handling the differences in efficiency would prevent a dome from being able to match them in high spl situations. At the top end the dome max spl range lets say 120db 1 watt 1 meter the driver will be experiencing some influence from power compression. It has too simply becasue of all the power it take to get to those levels. A compression driver is coasting at those levels. 20db difference in effciency when mounted to a waveguide is 100/1 power advantage over the dome. There is no way around this.
In your livingroom is a different story.
Rob
You can not just test two drivers of different types and draw general conclusion from that. It's so obvious I shouldn't even need to mention it."
Hello Peter
I think your are missing the point. He seems to looking at from his application stand point and high spls. You can drive a compression driver at 120db @ 1 meter for hours at a time. You can't do that with a dome. Even if they had the same power handling the differences in efficiency would prevent a dome from being able to match them in high spl situations. At the top end the dome max spl range lets say 120db 1 watt 1 meter the driver will be experiencing some influence from power compression. It has too simply becasue of all the power it take to get to those levels. A compression driver is coasting at those levels. 20db difference in effciency when mounted to a waveguide is 100/1 power advantage over the dome. There is no way around this.
In your livingroom is a different story.
Rob
But Rob..
if it is like you say and gedlee say.. then why does his Summa show a compression at 105dB 1 meter that is similar to what I measured from a dome tweeter?
The thing is that the Summa has a crossover to the tweeter (I assume here.. shoot me if I'm wrong ) which improves the thermal compression. The dome tweeters I measured had no crossover. That means to some degree the measured performance from the domes would improve with a crossover.
Now as I mentioned in the other thread I realize that it's "risky" to compare different measurements but still my findings strongly indicate that what gedlee was claiming was far from the truth.
SY (and gedlee)
of course I did not mean to insult in anyway.. criminal was just a "fun" way for me to write that it was strictly non-scientificall to claim what was being claimed.
For the record I can mention that there's a big difference between for example a non ferrofluid soft dome tweeter and a ferrofluid loaded alu dome (as anyone with basic knowledge about physics understand without studying the subject). That's why I asked what kind of domes gedlee used in his tests and comparisons.
There is a difference between a $10 kina tweeter and a Esotar or C23.
/Peter
if it is like you say and gedlee say.. then why does his Summa show a compression at 105dB 1 meter that is similar to what I measured from a dome tweeter?
The thing is that the Summa has a crossover to the tweeter (I assume here.. shoot me if I'm wrong
) which improves the thermal compression. The dome tweeters I measured had no crossover. That means to some degree the measured performance from the domes would improve with a crossover.Now as I mentioned in the other thread I realize that it's "risky" to compare different measurements but still my findings strongly indicate that what gedlee was claiming was far from the truth.
SY (and gedlee)
of course I did not mean to insult in anyway.. criminal was just a "fun" way for me to write that it was strictly non-scientificall to claim what was being claimed.
For the record I can mention that there's a big difference between for example a non ferrofluid soft dome tweeter and a ferrofluid loaded alu dome (as anyone with basic knowledge about physics understand without studying the subject). That's why I asked what kind of domes gedlee used in his tests and comparisons.
There is a difference between a $10 kina tweeter and a Esotar or C23.
/Peter
Peter you really must show your own testing results. You are having plenty of fun with the info Geddes has posted but-unless I missed it somewhere- we've yet to see one actual measurement from you to back up your claims. At this point it's just your opinion so I don't think Geddes is the one being unscientific at this point.
BTW why don't stadiums, clubs and theaters use Esotars and Revelators if they are so superior at high SPLs and have such low compression?
BTW why don't stadiums, clubs and theaters use Esotars and Revelators if they are so superior at high SPLs and have such low compression?
I've been waiting for the data as well. I'm skeptical about some of the power handling claims that have been made. If you're talking about RMS output, I don't see how you can get around the thermal limits, and if you're talking about peak output, I don't see how you can get around mechanics limits.
On a couple occasions I have worked in the transducer engineering department of an audio company- one that has a half-space anechoic chamber with an elaborate measurement system that (of many things) measures power compression and distortion. One of the most useful measurements it does is distortion/compression at a fixed SPL (adjusts voltage to be what it needs to be). I've looked at many of these measurements for domes and a handful for compression drivers on horns- the results are hardly even comparable. At levels where the dome can operate without dying, the compression driver is practically laughing. Unfortunately I currently do not have access to the data (or the program to view it) anymore, so I can't post it.
On a couple occasions I have worked in the transducer engineering department of an audio company- one that has a half-space anechoic chamber with an elaborate measurement system that (of many things) measures power compression and distortion. One of the most useful measurements it does is distortion/compression at a fixed SPL (adjusts voltage to be what it needs to be). I've looked at many of these measurements for domes and a handful for compression drivers on horns- the results are hardly even comparable. At levels where the dome can operate without dying, the compression driver is practically laughing. Unfortunately I currently do not have access to the data (or the program to view it) anymore, so I can't post it.
augerpro said:
A screen shot from the scope at the beginning and end of a sinewave.. how interesting would that be to see? I took notes and didn't save any graphs. We are planning a bigger shoot out further down the road... I'll save some things to look at and maybe I can regain some kind of credibility after that..
Yes it is!
I never said a dome tweeter can handle those spl's needed for those situations.. don't know where you got that from. I'm talking medium high spl or actually high spl for a home system playing music.
The Revelator (9700) is not recommended in my book since it has about double the thermal compression and HD as compared to Seas tweeters and Accuton C23 that I measured. Linkwitz also found the Seas to be better than the Rev9700 if my memory serves me.
The Esotar is sitting in an old box in my moms home but I have not measured that one yet.. will do though. I mentioned that one becasue it is a classic with good performance. Also becasue Dynaudio test their drivers with 1000W 10ms transients which some people in that other thread said would damage a dome tweeter... which of course are not true. At those levels the Esotar is compressing 1-2dB in a part of the range. 110dB it manage without compresssion. There are better dome tweeters today that I think (with good reason) reach 120dB peaks without compression.
If you read that thread you see a lot of mistakes gedlee does in his reasoning. Also remember he is the one calling himself a pro and a scientist... he also has something he wants to sell..
/Peter
Pan said:
If that's sufficient for your goals then it might work ok for you. But if one is trying to replicate a live experience, that's not anywhere near sufficient. 110 dB at 1m means 100 dB at the listening position, and that's peak. That is quite (~10 dB)shy of the peaks that events have, and you run the risk of burning the tweeter if the level is sustained. Contrast that with a compression driver that can do 110 dB RMS at the listening position all day.
Pan said:
That I doubt. Let's look at the mechanical requirements for this. In that case the stress is on the lower end of the spectrum, say 2k. The tweeter is effectively omnidirectional at that frequency. In order to hit a peak of 110 dB at one meter in half space at 2k, one needs to displace 300 mm^3 of air. 25 mm domes have an effective surface area of about 700 mm, so this means a peak excursion of ~ .4 mm. This is outside of the linear excursion limits of many tweeters but it is doable on a peak. However, if you step it up to 120 dB you need to move 950 mm^3 of air, which means 1.35 mm peak excursion. I do not know of any tweeters that can do this.
kstrain said:
The Esotar was the dome tweeter champ te10-15 years ago and in the upper range it manages 120dB peaks without compression (1000W 10ms). I talked with a designer of drivers and loudspeakersystems about his drivers a couple of years ago. I was then impressed by the Esotar but his system was better subjectively better to my ears. He used stock Dynaudios in some models but own designs for the upper range. He wasn't satisfied with the dynamic compression of the Esotar as I understood and I think he managed to get close to 120dB without significant compression from his own improved tweeters.
/Peter
Rybaudio said:
How loud is a "live experience"? How loud is a spanish guitar playing a ballad? A flute at three meters? A jazz trio playing soft at five meters? A nyckelharpa at ten meters?
What is the typical max spl in a concert hall at a typical seat when the orchestra is playing forte fortissimo? Seldom over 110dB and mostly around 100dB which is pretty high level.
Yes there are music and instruments that needs 120-130dB in order to be reproduced with full fidelity in that regard.. but how common is that? As you mention it's an individual thing.. I for one do not like the kind of level that you have from a drumset at 1-2 meter.. it's horrible.. you know many drummers use hearing protection when playing right?
You say that a compression driver can play 110dB all day... but with what kind of compression and distortion?
Gedlees Summa showed about 0.5dB compression after 5sec with 105dB at 1 meter if memory serves me. That was about the same level as the Seas and Accuton C23 tweeters I measured and that was without crossovers which indicates a possibility that for example the C23 would be BETTER than the compression driver in the summa up to 105dB or thereabouts. The heating of the voice coil doesn't change for a given output with a crossover but the higher impedance drive linearizes both thermal compression and HD IMD.
I also want to mention that the compression that I measured in those tweeters that match the compression tweeter in the Summa was a "worst case" measurement. The frequency was choosen where the drivers have the impedance as resistive as possible around 4-5kHz. Move the signal up or down and the compression effect of the increasing voice coil temperature/resistance is decreased due to the motor reactance.
Food for thougt?
I would gladly take a look at a compression driver or a ribbon with dynamic behaviour that is better than the tweeters I have mesured and the Summa tweeter. Any pointer to a champ or two in that regard? Not just hearsay but real performers.
It was partly due to this kind of talk that led me to do some measurements and so far it seems like dome tweeters is way better than what the "pro-driver-high-spl-crowd" has told us.
Yes, for high spl systems with dome tweeters it's often necessary to go up to 3kHz or so which gives you an extra 6dB as compared to a 2kHz crossing. Then many tweeters has excursion to handle it. The C23 has +/-1.2mm. Now I didn't check your math but it seems like you forget that at the crossover point the tweeter may be 6dB down effectively double the output that you mention.
So in the end.. the excursion is no problem if a quality driver is choosen and the crossing is placed with some thought.
/Peter