ToTo Man
the band not the dog
I'm interested in what folks think is going on (or, more aptly going wrong) with the following tweeter responses.
I'm not going to name the make or model of the speaker, all I'll say is that it's a two-way sealed bookshelf/standmount design from the late 70s / early 80s with a 6.5-inch mid/bass cone crossing to a 1-inch silk dome tweeter at 3kHz. Its anechoic frequency response was published with generous +/- 5dB margins.
I've owned four pairs over the years (if I see them at a bargain price I can't resist buying them!). I thought they were pretty decent for their time with a lovely warm but openly detailed balance with impressive solidity and depth, and I had no complaints apart from the high treble frequencies. Not having had the ability to measure their frequency response in the past, I couldn't quite pin-point what it was I was finding odd about the treble, my best analogy at the time was likening it to a "citric zest".
Now that I've measured them it is clear what the issue was, they have a +9dB spike at 13kHz! This spike is present (to varying degrees) on two of the three pairs I recently measured, and I'm pretty sure a similar spike would have been present on my very first pair that I owned about 15 years ago.
Interestingly, the third pair I measured (Pair C above) don't have a sharp spike at 13kHz, but a more gentle +4dB plateau that's consistent with the quoted "+/- 5dB" anechoic response. This makes me suspect the +9dB spike wasn't part of the original tuning but has instead developed over time, either due to natural age-related deterioration of the tweeter and/or crossover components, or an abuse of signal input level. I'd be interested to hear your thoughts on what might cause such an odd looking HF response? I'd normally look at the distortion graph for clues, but this only goes up to 10kHz so isn't of much help.
I should note that all measurements were taken on-axis with the tweeter and at a distance of 1 metre. Pair A and Pair B are no longer in my possession, I've only kept hold of Pair C as the frequency response was more agreeable to my ears.
I'm not going to name the make or model of the speaker, all I'll say is that it's a two-way sealed bookshelf/standmount design from the late 70s / early 80s with a 6.5-inch mid/bass cone crossing to a 1-inch silk dome tweeter at 3kHz. Its anechoic frequency response was published with generous +/- 5dB margins.
I've owned four pairs over the years (if I see them at a bargain price I can't resist buying them!). I thought they were pretty decent for their time with a lovely warm but openly detailed balance with impressive solidity and depth, and I had no complaints apart from the high treble frequencies. Not having had the ability to measure their frequency response in the past, I couldn't quite pin-point what it was I was finding odd about the treble, my best analogy at the time was likening it to a "citric zest".
Now that I've measured them it is clear what the issue was, they have a +9dB spike at 13kHz! This spike is present (to varying degrees) on two of the three pairs I recently measured, and I'm pretty sure a similar spike would have been present on my very first pair that I owned about 15 years ago.
Interestingly, the third pair I measured (Pair C above) don't have a sharp spike at 13kHz, but a more gentle +4dB plateau that's consistent with the quoted "+/- 5dB" anechoic response. This makes me suspect the +9dB spike wasn't part of the original tuning but has instead developed over time, either due to natural age-related deterioration of the tweeter and/or crossover components, or an abuse of signal input level. I'd be interested to hear your thoughts on what might cause such an odd looking HF response? I'd normally look at the distortion graph for clues, but this only goes up to 10kHz so isn't of much help.
I should note that all measurements were taken on-axis with the tweeter and at a distance of 1 metre. Pair A and Pair B are no longer in my possession, I've only kept hold of Pair C as the frequency response was more agreeable to my ears.