Tweeter instrument tests

[Al Klappenberger]

JBL 2404H

[Al Klappenberger]

Selenium D220TI

This tweeter increased distortion as level was increased, then went down and back up! I did a test a 1.5V RMS (280 mW) into to see how it would act. I don't understand this!

[Al Klappenberger]

B&C DE10

This tweeter shows the same tendency to have a level of lowest distortion, like the Selenium, but not as much so.

I did a 1.5V RMS test to this one too.

Maybe this is normal?

[Al Klappenberger]

It's hard to beleive, but it looks like the old T-35 . K77M is the lowest distortion tweeter. This might be because it's the highest efficiency. I can hear PWK's ghost saying "I told you so!"!

The highest distortion are the two tweeters with the 1/2 inch aperture to improve dispersion. that's the Beyma CP25 and the JBL 2404. As usual, it's always a balance of compromises!

Considering that I found .5V RMS to the maximum level into my tweeter, all of the tweeters have acceptable levels of harmonic distortion. You just can't use the Beyma or the JBL at extreme levels.

This makes me feel a bit more at ease considering I have be recommending the CP25 for years and am using them in my own speakers. I ordered B&C DE10s to replace them, but I may not bother doing it now.

BTW: If, after comparing these plots, anybody sees someting that makes no sense let me know. I am prone to getting things mixed up. You might see a plot that is identical to one of the others that's grafted into the wrong paste-up.

Al K.

[Al Klappenberger]

After a lot of experimenting, I noticed that I get more consistent distortion reading if I position the mike right in front of the tweeter mouth, on center and 2 Inches away. Moving slightly off center causes the dispersion pattern to reduce the high frequency harmonics making the distortion read lower than it really is.

Mike was B&K 4133

AMP: McIntosh MC50

Analyzer and singal source: HP 3563A

AL K.

This is the tabulated results:

[peshewah]

I don't understand all the charts. But want to build some cornscala's one day. While my family is home I keep the volume down. But when they leave I would crank it up. Is there a tweeter that works good at high and low levels? And still hear the crash of a symbol? Thanks for your time.

[Al Klappenberger]

Larry,

Distortion goes down as loudness goes down. The question is HOW loud is loud! I think mosty any of the tweeter I have tested can be considered low distortion at normal home levels. If you are going to use your speakers in a large auditorium, I would avoid the Beyma and JBL. For the home stereo, any of them will do nicely.

[peshewah]

Thank you Al for all your test, hard work and your time.

Like I said before , I want to build but man its so confusing at times. I just want to do it right when I do it. Please excuse my ignorance.

[DrWho]

BTW: If, after comparing these plots, anybody sees someting that makes no sense let me know. I am prone to getting things mixed up. You might see a plot that is identical to one of the others that's grafted into the wrong paste-up.

Did the the Selenium D220TI at 0.5V accidently get the plot from the JBL2404 at 0.5V?

Or does the Selenium really jump to 1% THD between 0.1V and 1V?

[Al Klappenberger]

Who,

I tested the Selenium several times to verify that. It's not a mixed up plot. Its distortion goes up, then down and then back up with level. Note that the B&C does the same thing, but only just slightly.

Al K.

[Hardhead]

Does anyone else find it ironic that the tweeter which consistently generates the least distortion is the one that most--if not everyone--would agree sounds the worst? The K-77 is the tweeter that everyone wants to get rid of and replace with a different tweeter that has more distortion yet sounds better. That says a lot about choosing a horn/driver solely because it tests well. Of course, I understand that listening tests alone aren't the answer, either.

[ka7niq]

After a lot of experimenting, I noticed that I get more consistent distortion reading if I position the mike right in front of the tweeter mouth, on center and 2 Inches away. Moving slightly off center causes the dispersion pattern to reduce the high frequency harmonics making the distortion read lower than it really is.

Mike was B&K 4133

AMP: McIntosh MC50

Analyzer and singal source: HP 3563A

AL K.

This is the tabulated results:

Well, since we hear a balance of direct vs reflected sound anyway, who cares ? Good Sound is what it is all about anyway, not pleasing a scope, right ? Why not do Impulse Response testing instead AL ? The Danish believe the the tweeters that pulse test the best, sound the best ?

[DrWho]

Does anyone else find it ironic that the tweeter which consistently generates the least distortion is the one that most--if not everyone--would agree sounds the worst? The K-77 is the tweeter that everyone wants to get rid of and replace with a different tweeter that has more distortion yet sounds better. That says a lot about choosing a horn/driver solely because it tests well. Of course, I understand that listening tests alone aren't the answer, either.

These plots are only comparing distortion at one frequency. I'm not quite sure I would jump to such drastic conclusions based on the limited data-set. Full bandwidth distortion plots tell a lot more, but they still only quantify one of the many audible metrics.

We can't get around the fact that less distortion IS more accurate to the source material (who wants frequencies that were never there originally?) If you feel there is no trend between the distortion plots and what you find to be subjectively better, then I would recommend looking for other metrics that describe the differences you're hearing.

I think it's fair to say that some people prefer the sound of extra distortion, but I would suggest that the masking it provides would be better done in the studio where it can be fine-tuned for each piece of music...

[Al Klappenberger]

Does anyone else find it ironic that the tweeter which consistently generates the least distortion is the one that most--if not everyone--would agree sounds the worst? The K-77 is the tweeter that everyone wants to get rid of and replace with a different tweeter that has more distortion yet sounds better. That says a lot about choosing a horn/driver solely because it tests well. Of course, I understand that listening tests alone aren't the answer, either.

I do find that an interesting point! I'm not sure people are replacing them just because they sound bad, but for other reasons, like the fact that they are inconsistent and blow up easily. The one I used in the test was NOT a "true" K77M. It had no markings on it. It was a known good ElectroVoice T-35. People also replace them because they don't go up very high. I don't think that makes a lot of sense though since most of us can't hear beyond 15 KHz anyhow! BTW: This is one of the reasons I picked 5 KHz to use as a test tone. the 2nd and 3rd harmonics are 10 and15 Khz. Chances are you might be able to hear that. I once compared a 10 Khz sine wave to a square wave. I couldn't hear any difference at all! There is also intermod distortion. When you add in the 12.5 Khz tone the lower products added are also in the audible range but seem to go right along with the harmonic distortion in the severity.

Basically, even the 3% worst case isn't that bad for a speaker.

Impulse resonse. Yes, there's another bag of worms! I might just do some testing on that once I get cought up on other stuff!

Al K.

[LARRY]

In a large room approximately 7000 cubic feet, what whould be the voltage needed for normal listening levels (65-80 db)?

Thanks, Larry

[Al Klappenberger]

Larry,

I can't answer that one! I know that in my room the peak voltage with it louder than I heardly ever run the system, the voltage was 0.4V RMS maximum.

Al K.

[LARRY]

ALK,

Thanks for the reply. At least I have a reference point.

Larry

[Hardhead]

DrWho--

I'm not sure what drastic conclusion I jumped to in my previous post. Can you help me find it? I believe I made the point that we shouldn't choose horn/driver combinations based solely on test measurements, and neither should we choose them based solely on listening tests. Perhaps that concept could be considered radical in certain audio circles, but it seems basic common sense to me.

[pocket.change]

Mr. Al,

Concerning the JBL 2404, did you note the black post is +

moving the voice coil forward?

After your measurements, have you balanced your results with

the published results of the various manufactures? If so, would

you be willing to contribute your opinion on the test examples?

p.c

[Al Klappenberger]

P.C.

There is really no wayt to see the diaphragm movement. JBL does have a reverse standard. I don't think it matters much with a tweeter though. The wavelength is so short at tweeter frequency that just an inch or so can be a bigger phase shift than inverting the polarity.

I did compare the results with some of the published curves. Most are close enough to conclude that nobody was lying!

I think the conclusion is that the lowest distortion is the B&C followed closely by the Selenium. The Selenium has the widest response. The Beyma and JBL have a bit higher distortion at high levels to get better dispersion. If I were to declare an overall winner, it's the JBL.

AL K.