So I selected a particularly nasty track with lots of distortion and high end cymbal crashing (Messhuggah) and played it back through my tweeters via a portable CD players headphone output. I setup my behringer ECM8000 measurement microphone plugged in via cakewalk sonar and tested various types of tweeters with this same track, taking the average output of the introduction and first verse of the track. The placement of the microphone did not change and the tweeters were positioned at the same distance from the microphone, on axis with the microphone diaphragm.
My goal here is not to find out which is louder, but to find out how the shape and wiring of the tweeters affects the response. Recently there have been a lot of discussions about how the different shape and styling affects the “sound” that the tweeters give, and since the tone of something is very important to me I wanted to do this test and I wanted to do it with real music rather than white/pink noise.
First of all, here is the plot of the background noise of the computer in the room I recorded in. I used an EQ plug in before the analyser to get rid of all signals below 600Hz. I probably could have gone up to 1.5kHz in fact but I decided that this was an acceptable background figure. Just be aware of it when viewing the upcoming photos
So first up is a single CTS Powerline Tweeter – note that its response is strong right down to 2kHz and there is a smallish dip at about 6kHz but not a lot to be concerned about. Also notice the average volume level.
Next up is a single 1177 WLE dual element tweeter – note how there is a weakness at 3kHz and 10kHz compared to the CTS and also note how the 1177 is as strong at 5kHz but gets obliterated by the CTS above that. On the plus side it appears to roll off slightly slower at the very high end (20kHz)
Now we move to 2 1177s parallel wired, physics says that the response should start to flatten and there should be 6dB more output. In a blind listening test the CTS tweeter is still slightly louder on its own than these 4 elements but only just! They are much stronger in the 5kHz area and now have the sensitivity at the low end of their range as well. They are still losing out to the CTS at 10kHz and above.
Now lets compare the 4 1177s parallel wired with the 1005s also parallel wired. Apples with apples here so this is a direct head to head! The plots at first appear similar and the 1005s seem to have a flatter response in the 3kHz area, and indeed they do, but once you look across to the output side of things, the 1005 array is over 3dB quieter on average than the 1177 array, now lets not forget these are the same tweeter elements manufactured by the same company but the response is different, so that can almost certainly be horn related. The 1005 array also has some of the defects in response that the single 1177 exhibited, such as the weakness at 10kHz and above.
So what does this all mean? Well judging from the sound alone, the 1177s sounded more balanced to my ears, the sound compliments the music perhaps a bit better than the 1005s, the CTS beats them all on sensitivity but its frequency response means it’s a little harder sounding, this characteristic should go away with them all stacked but when they were available CTS Powerline tweeters cost over ten times as much as the WLE piezos I purchased. With hindsight and Dave Perrys testing, we now know that the CPC piezos are better quality than these WLEs, but for those who might have been sitting on the fence as to which model of piezo to purchase, perhaps this helps matters a little. I will be buying other piezos in the future from CPC including the much-used 1016 to test as I think its important to get the right tool for the job.
In addition to this I tested out the tweeters with some other tracks both live and electronic based. The best overall tonal quality came from the 1177, with the CTS sounding harder in the 2kHz range with all the test tracks. The 1005s sounded good for electronic music but not good at all for more organic sounds.
Anyway until next time...
Stu
