Instrument tests on 5 tweeters

[Al Klappenberger]

I just finished doing some testing on 5 different tweeters. I did the testing to determine which tweeter to recommend to my customers and to decide which I might want to sell. I mention this right away because I am sure to get a lot of grief from the usual group of self-appointed forum police about having an axe to grind or how I am using the forum as a sales tool. If you feel this way, take it to the management! To the rest of us who genuinely want to know what is the best tweeter to get, stay tuned. The plots were all done the exact same way for comparison.

The comparison was between 5 different tweeters:

* ElectroVoice T35 version of the Klipsch K77M

* Crites B&K Sound CT125 (available from Bob Crites)

* B&C DE10 + ME10 horn (available from me)

* Beyma CP25 (Available from US Speaker)

* Selenium D220TI + MH17-25 horn (available from Bob Crites)

The tests were:

* Frequency response and sensitivity for 1W at 1 Meter on-axis using the T35 as reference.

* Frequency response and sensitivity for 1W at 1 Meter at 45 Degrees off-axis.

* IM distortion using tones of 5000 and 12,500 Hz at 100 dB SPL at 2 feet.

Equipment used:

analyzer: HP 3563A

Signal generators: source in HP 3563A and HP3325A

Amp: McIntosh MC50

Mike: Old Colony Mitey-Mike II for frequency response. B&K 4133 for IM distortion.

Below is a giant paste-up of 4 tweeters each against the T35 (black traces). The on-axis plots are to the left and the 45 degree off axis plots are to the right.

[Al Klappenberger]

Here is another paste-up of the 5 tweeters for IM distortion. Harmonics of the 5 KHz tone can clearly be seen too.

Al K.

[Al Klappenberger]

Conclusions:

The cear winners are the B&C DE10 and the Selenium D220TI. Both of these are very inexpensive and nearly the same price.

I am VERY disappointed in the distortion from the Beyma CP25. I will no longer be recommending them and will probably replace them in my own speakers in the future. I suspect the problem may be the small round aperture in the center of its horn. This might be to improve dispersion. I think that's a secondary consideration compared to modulation distortion!

Al K.

[Rudy81]

Al, thanks for looking into the tweeters. That Selenium has a very nice, relatively flat response.

[jwc]

Nice Al.

I don't understand though, the selenium is a 60 x 40 horn. You are 45 degrees off axis and it has the least "falloff" on the high end. I would have expected the ME10 to look like that.

jc

[Al Klappenberger]

JC,

Bob and I had a discussion about the 60 X 40 question. He suspected I may have had it oriented wrong. I did plots of the Selenium 45 degrees off axis with the horn sitting upright and on its side. The two plots were virtually identical. I don't know for sure which plot is which, but I think green is normal and red is on its side. Black is on-axis.

AL K.

[jwc]

Al.

I find that very interesting and puzzling. I mean the other curves look 'reasonable" like you would expect.

At any rate....

Al, you know what would be cool is if you mount that selenium on a baffle side by side with your new trachorn 420 and give an on-axis and off-axis plot (while utilizing your ESN5800). You may want to move the mic further away and pic your reference point somewhere between the horns and between the drivers. Just a thought. It could give you an insight on changing an XO point bases on polars. Obviously, the "sound" play a bigger role here.

jc

[Al Klappenberger]

JC,

I suppose I could do something like that at some point, but It would have to be when somebody orders that combination. I'm a small time operation and I don't always have all the parts on hand at one time. That also brings up the subject of polar plots. That's a set of tests I am not up to doing. I am just hoping that a standard set off-axis angle plots will do. I am not impressed with the numbers these manufacturers give for dispersion anyhow. The two plots taken with the Selenium sitting on its top and side is a case in point. I also had the B&C ME20 horn here that will fit the DE10 driver for a couple days. It was sent to me by mistake, so I had to return it. It has an angle "break" in one of the flares compared to nearly identical top/bottom and side flares of the ME10. I did a listening test by swinging the horn from straight on to an angle as I listened to white noise. I could not perceive hardly any difference between the two horns off vertically or horizontally. The change in "pitch" of the noise was very similar. The two horns are both rated the same coverage angles to, so why are they flared differently? Another point is the average person's listening position. I don't think many of us listen to speakers positioned square against the wall. I have mine toed-in so the angle to the speaker isn't very great. The Khorn is stuck pointing 45 deg out of the corner. Testing with a 45 degree angle seems like it would be a worst case situation.

Al K.

[PrestonTom]

Interesting results Al.

I will point out to those who are used to thinking about distortion in units of %, rather then dB, that Al has scaled the Y-axis in units of "power" (proportional to Voltage squared). This is a 10 log quantity when converted to dB.

Some of you may be used to seeing similar plots as a 20 log quantity (voltages or SPLs). Although the dB down-points are the same of course (either power or SPL), the %'s will be different.

-Tom

[Al Klappenberger]

The percent distortion thing can be confusing. To look at just one "spike" on the spectrum and define how may "percent" it represents isn't useful. You need to consider "total modulation". Each and every distortion product and harmonic needs to be summed up together according to its level and the total expressed in "percent".

Al K.

[Guest David H]

I am VERY disappointed in the distortion from the Beyma CP25. I will no longer be recommending them and will probably replace them in my own speakers in the future. I suspect the problem may be the small round aperture in the center of its horn. This might be to improve dispersion. I think that's a secondary consideration compared to modulation distortion!

I'm surprised by your findings as well, I repeatedly picked the CP25 in a blind listening test, only to be bettered by the Heil AMT. Then again the Selenium and B/C were not tested.

[Deang]

Well, something's certainly wrong -- the K-77 gives me a headache and the Beyma sounds gorgeous. This confirms that the cleaner it is the worse it sounds.

[Al Klappenberger]

Dean,

I guess some people just like distortion! BTW: Have you ever checked out the electronics department at Wall - Mart? [^o)]

Al K.

[sootshe]

All great info Al & thanks for giving us all a base line to judge these by. When are you going to give us your subjective impressions? I don't think many of us would buy any speaker without listening to it first, regardless of how it measures. I personally have only heard the Klipsch driver & the Crites CT125. My subjective impression is that I personally didn't like the Klipsch driver & found the CT125 marginally better.......until I fitted it with a different horn & then it bloomed & opened right up.

Thanks for your efforts []

[Al Klappenberger]

Sootshe,

"When are you going to give us your subjective impressions? "

Just like Dean, I have been listening to the Beyma CP25 tweeters now for years and liked them. That tells me I must have a tin ear! I think I should stick to instrument tests! All I can say is that I have never been happy with the sound of symbols. Maybe this is why.

Another good example of how your ears can fool you is the ionic tweeters that work by generating a spot of ionized air. You would think that a tweeter having no moving parts would be the ultimate thing. PWK did IM distortion test on one of them. The distortion products were off the chart. It measured 30% distortion! People who hear it say it has a "silky" quality.

Al K.

[jcmusic]

All great info Al & thanks for giving us all a base line to judge these by. When are you going to give us your subjective impressions? I don't think many of us would buy any speaker without listening to it first, regardless of how it measures. I personally have only heard the Klipsch driver & the Crites CT125. My subjective impression is that I personally didn't like the Klipsch driver & found the CT125 marginally better.......until I fitted it with a different horn & then it bloomed & opened right up. Thanks for your efforts

Sootshe I too did a similar thing, I used a ATP200 that's the same driver Crites uses and put on a 90X90 horn just love what it did to the sound!!!

Jay

[ZAKO]

And some times we test the wrong perameters.... I tested the ionic tweeter and got much lower results.

[Deang]

"Just like Dean, I have been listening to the Beyma CP25 tweeters now for years and liked them. That tells me I must have a tin ear! I think I should stick to instrument tests!"

Good grief Al -- this hobby is about listening and enjoying what we hear. In the end, we have to rely on what our ears are telling us, tin or not. Measurements prevent us from being deceived, but they don't invalidate ALL subjective impressions.

All I can say is that I have never been happy with the sound of symbols. Maybe this is why.

No, that's just what cymbals sound like when you cut them so steep that they ain't doing much of anything. []

[Deang]

Here are the manufacturer supplied distortion plots for the Beyma and the Selenium. So, what do we do with these?

[BEC]

Dean,

For one thing, much different horn in that Selenium manufacturer's test than the one Al tested.

Bob