Does anyone know of any standard tests that can be applied to determine whether tweeters are damaged ?
The tweeters I'm using (Morel MDT32-s) sound a bit unpleasant (possibly a resonant peak making them very lispy), but I don't know whether they are damaged, or if it is a design problem.
Any help would be greatly appreciated.
The tweeters I'm using (Morel MDT32-s) sound a bit unpleasant (possibly a resonant peak making them very lispy), but I don't know whether they are damaged, or if it is a design problem.
Any help would be greatly appreciated.
Around 3kHz, 2nd order, with a series attenuator.
The problem does not seem to particularly amplitude-dependent, so I don't believe it is due to using a Xover freq too low (also the resonant freq is 700Hz on these tweeters).
The problem is still there if I use a simpler 1st order crossover, which seems to rule out a peak due to an underdamped crossover.
When I disconnect the midbass unit, the problem is still there, which rules out driver interaction.
The drivers are not recessed, so I also wondered if the front-plate edge-effect could be introducing a resonance.
The problem does not seem to particularly amplitude-dependent, so I don't believe it is due to using a Xover freq too low (also the resonant freq is 700Hz on these tweeters).
The problem is still there if I use a simpler 1st order crossover, which seems to rule out a peak due to an underdamped crossover.
When I disconnect the midbass unit, the problem is still there, which rules out driver interaction.
The drivers are not recessed, so I also wondered if the front-plate edge-effect could be introducing a resonance.
The non-recessed edge of the tweeter front plate could cause diffraction anomalies in the frequency response. However I don't believe that those would be very easily detected by ear, particularly if not listening exactly on-axis.
http://www.zaphaudio.com/mtg-surface.html
http://www.zaphaudio.com/mtg-surface.html
Have you tried them on a different amp?? Might be worth a shot. I was testing my amp today and it sounded like I had a blown tweeter, but it was actually the amp distorting badly in the high frequencies.
Tony.
Tony.
The problem may be the attenuator. If its wire wound its inductance may be interacting with the cross over circuit and tweeter inductance. If the level of the tweeter is what you want, measure the pot and replace it with a resistor. Wintermule's suggestion is worth looking into also.
Thanks for the replies. I'll try changing the source, in case it is an amp problem, I'll also look at changing the louspeaker cables in case this is the problem.
Andy, the attenuator is actually just a resistor anyway, but that reminds me... time for another post on tweeter attenuators
Andy, the attenuator is actually just a resistor anyway, but that reminds me... time for another post on tweeter attenuators
Hi,
I noticed that small differences in the crossover / the frequency response over a certain frequency range can have a large influence on perceived "harshness" , while more gross aberrations go by unnoticed elsewhere.
In the 1-3kHz region, even 0.5 - 1 dB difference in level, or a small peak (1-2 dB) in frequency response, can turn the system from natural to unpleasant sounding. Given that frequency responses of real life speakers are flat at best within a 3 dB band, an unfortunate little peak might cause your problem. You might try to play with level (L-pad) or purposely tweak the crossover (read, slightly misalign it) to fix that.
If you have measurement capability, this will help identify possible targets. As for level, when I set the level in my tweeters MLS/FFT measurements were practically useless. Unless heavily averaged the differences were hardly visible on screen, and looked insignificant at any rate. But 1 dB less on the tweeter made the difference in my system.
I noticed that small differences in the crossover / the frequency response over a certain frequency range can have a large influence on perceived "harshness" , while more gross aberrations go by unnoticed elsewhere.
In the 1-3kHz region, even 0.5 - 1 dB difference in level, or a small peak (1-2 dB) in frequency response, can turn the system from natural to unpleasant sounding. Given that frequency responses of real life speakers are flat at best within a 3 dB band, an unfortunate little peak might cause your problem. You might try to play with level (L-pad) or purposely tweak the crossover (read, slightly misalign it) to fix that.
If you have measurement capability, this will help identify possible targets. As for level, when I set the level in my tweeters MLS/FFT measurements were practically useless. Unless heavily averaged the differences were hardly visible on screen, and looked insignificant at any rate. But 1 dB less on the tweeter made the difference in my system.
I agree, that`s true and very well said.
But as AntM said "very lispy" I assume the problem being rather elsewhere.
The Morel MDT32 is a textile dome tweeter (I`m otherwise not familiar with this brand/model) and I`m sure it is coated (as almost all textile domes are coated) in one way or another to damp it`s inherent resonancies in the upper frequency range.
I have seen textil/fabric dome-tweeters where this coat failed after a few years just because of expose to sunlight (UV-rays) and thereby producing a sharp 10db (!) peak resonance at 13kHz(backed up by own measurements).
Such a thing could well produce what "AntM" described as "very lispy".
As I mentioned, I don`t know the Morel MDT32, I don`t know if it`s new or used (if it has ben exposed to UV or not) , so take this just as a wild guess.
It's a new one, so I'd be surprised if that's the problem, but it's an interesting observation all the same.
On MBKs comments, I've certainly noticed that reducing the tweeter level by a slight amount (reducing a 3.9 ohm series resistor to 2 ohms, around 1.5dB change) makes a huge difference to subjective quality, so on this basis I can well imagine that a small peak could be responsible. I suppose the question is whether this can be compensated using a notch filter without compromising the response at surrounding frequencies (or messing up the phase response)
On MBKs comments, I've certainly noticed that reducing the tweeter level by a slight amount (reducing a 3.9 ohm series resistor to 2 ohms, around 1.5dB change) makes a huge difference to subjective quality, so on this basis I can well imagine that a small peak could be responsible. I suppose the question is whether this can be compensated using a notch filter without compromising the response at surrounding frequencies (or messing up the phase response)
AntM said:
Is that series resistor before or after the crossover?
Btw, you are not reducing the tweeter level, it's the opposite.
And if the resistor is after the crossover, when you reduce it's value you are also crossing at a higher frequency, which is probably what you should do with that tweeter.
Sorry, yes, the resistor was increased to reduce the level.
I've tried both configurations for the series resistor. My instinct is to put it before the HF Xover (in series with the capacitor) - see my other post on this - L-pad
the only real difference I noticed was an increase in treble output around the Xover frequency with the resistor in series with the tweeter - obvious when you consider that the Xover frequency is being reduced due to a higher load impedance. I can understand the reason for the L-pad, to keep the load seen by the filter constant, but actually this only works if the tweeter impedance is constant. Anyway, I'm starting to ramble...
I've tried both configurations for the series resistor. My instinct is to put it before the HF Xover (in series with the capacitor) - see my other post on this - L-pad
the only real difference I noticed was an increase in treble output around the Xover frequency with the resistor in series with the tweeter - obvious when you consider that the Xover frequency is being reduced due to a higher load impedance. I can understand the reason for the L-pad, to keep the load seen by the filter constant, but actually this only works if the tweeter impedance is constant. Anyway, I'm starting to ramble...
hmmmm I thought one of the big advantages of the morel tweeters was that they could be successfully crossed over as low as 1.8Khz 🙂 3Khz should be more than enough I'd have thought 🙂
Tony.
Tony.
I've just completed a MTM TL with a Vifa D25AG metal dome tweeter, crossing over at 1800Hz. I'm not happy with the tweeters performance; it's very harsh sounding. The tweeter's Fs is 850Hz, so I thought using the 2x rule that 1800 would be okay. I'm hoping that part of the problem is Solen cap breakin, but we'll see. I'm using a "professionally designed" 2nd order crossover and the graphs look good. Any suggestions?
Bob
Bob
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