Metal dome tweeter advice

[tiefbassuebertr]

Originally Posted by tvrgeek

Obviously, the Qms will differ. I see that as different, not good or bad.
You are suggesting they change their character over time. Is this an initial shift or a continual shift? What matters is the sonic character. Are there generalizations yo would suggest?

I have not conducted detailed studies of the behavior of ferrofluid over the time.
If you read the site about
Audio Ferrofluid Benefits
you will note, that the use of ferrofluid has only advantages.
My experiences are exactly the opposite (mainly cause hardened ferrofluid in the air gap of the tweeter after shortly use).
For this reason I haven't use tweeters with ferrofluid in the last 15 years.

In general, different Qms means neither good nor bad. In case of Ferrofluid low Qms is clearly bad.

Check out this links:
Ferrofluid tweeter misshap!
B&W P6 Tweeter replacement

Easy way to test if ferrofluid in ADS tweeters has hardened? - AudioKarma.org Home Audio Stereo Discussion Forums
Ferrofluid
Hardened "goop" (ferro-fluid) on midrange/tweeter speakers?

Because my English is not perfect, I can not explain all reasons, why ferrofluid has no advantages.
BTW - we are off-topic in the meantime. start a new thread "Pros and Cons of Ferrofluid by Tweeters".

[tvrgeek]

As relevant to advice in selecting a suitable replacement driver, the preference or potential problems from readers for or against ferofluid seems relevant. I find it curious several forum members have expressed a large dislike for ferofluid, but none have explained why. I respect their views, but would like to have them explained a little. It could be what is a disadvantage for you may be an advantage to me. That both Seas and ScanSpeak offer the same driver with and without suggests tangible differences.

I wonder if your bad experiences are the result of very heavy use? Heavy as in really pushing the average power above what was expected basically cooking the fluid?

Why do you suggest low Qms is a problem in a tweeter?

Not knowing the exact nature of the material in use, it seems to be a open question if it evaporates over time. I can easily imagine it changes viscosity somewhat with temperature, changing Qms as it does so. That said, I have had no issues in over 15 years with my Studio 20's and used ff tweeters in the harshest environment possible, a dashboard in a car in Colorado with repeated exposure over 140 degrees F.

Do not be shy about your English. It is not spoken well here either. The only German I learned when I was in Frankfurt as a small child I should never repeat in public. (circa 1961) so you have a leg up on me.

[sreten]

Hi,

H0831-06 - Seas 27TFF 1 inch tweeter - Europe Audio

I still think cost vs. performance, the above which doesn't have a rear
chamber but does have a cavity in the pole piece, is a good choice
given the application and should need minimal x/o changes, if any
at all, as the sensitivity matches typical JBL metal domes.

Fs is high, for a Seas dome, and one reason I'm suggesting it.
The same probably applies to the JBL dome and higher Fs
tweeters work with simpler x/o's better than lower Fs, due
to overall excursion considerations, cheaper can be better.

The "best" tweeter for an application isn't the "best" available.
The above is my best guesstimate based on value versus
performance for the intended application (guesstimated).

"Better" tweeters can have more problems in this application.

rgds, sreten.

No mention of the actual speaker model, or the x/o used,
is inviting pure conjecture, there are better approaches.

[tvrgeek]

Everyone should make note of sreten's third paragraph.

[5th element]

Originally Posted by tvrgeek

Question for all: In dealing with breakup issues, do you prefer a notch filter or a low pass filter?

For the high frequency break up in metal dome tweeters? The idea is that they don't need anything as we can't hear them. If however I did want to flatten it I would go with a notch filter. The ultrasonic resonance in dome tweeters tends to be very high Q and a low pass filter would do very little to actually attenuate it. The low pass would also probably roll off the upper octave of the tweeter too which would only add to the usual droop associated with metal cone drivers, that occurs just before the cone rings.

I suppose if you were using a DSP solution you could try it, with and without an ultrasonic notch filter in place, but the DSP would have to be capable of working at 96kHz as the peaks generally occur outside of CDs normal bandwidth. This of course begs the question, if CDs don't contain any data at the frequency where the dome rings, then it will surely never really be excited, so why bother with a notch at all?

If you're asking in general about how to deal with the peak associated with a metal cone mid/bass then that depends on the loudspeaker being designed. By design you should be crossing over low and steep enough so that the associated peak in the third harmonic, caused by the amplification of the distortion product by the ringing cone, is moved out of the picture. If done correctly the low pass will usually provide enough attenuation to the main peak, but if it doesn't, or if you want to use a 2nd order filter, then a notch may be needed also.

You will see that in Zaph's measurements that the amplification of the distortion products also occurs in the metal domed tweeters, it's just that the third harmonic in tweeters tends to be lower then in mid/bass drivers so that it isn't so much of an issue. That and we can't actually hear the third harmonic of a frequency that high either, but it could potentially be folded back into the audible range due to some inter modular effect of a suitable signal.

[tvrgeek]

5th,
Your last paragraph is what I am chasing. The reasoning behind this is in investigating what causes my wife to dislike most speakers and many amplifiers. Amplifiers with lower very high order harmonics seem to do better (Rotel vs my Parasound, Hafler etc.) I believe the amp is partially masking the tweeter problem. On the test bench, with my DCX I can make it better with a 48 db LP at 20K, but that does not eliminate the amp or crossover distortion. My measured output is better, not solved. Measurements are on hold as my e-mu is crashing my PC. ( plus the DCX is not exactly HI-FI).

[5th element]

Well technically speaking there isn't much you can do about these harmonics. Say you've got a peak in the third harmonic centred on 10kHz (ie the dome rings at 30kHz) and either side of the peak its -3dB points are at 29.5kHz and 30.5kHz. Now if you play a 9.83 and 10.17kHz tone through the tweeter you will get some inter-modular distortion as a product of those two tones, but the tweeter will also be outputting 29.5 and 30.5kHz from the third harmonic of those two test tones too and these will also create inter-modular distortion that will be at an audible frequency.

The trouble with this is that you cannot do anything about it, the tones that excite this problem are well within the audible range. It's the same issue as with metal cone mid/bass drivers and to get around that problem you need to cross over low. The only way to be completely free of this is to use a tweeter with a soft dome, use a stiff dome that rings at a much higher frequency or use a stiff dome with a well controller break-up.

Of course whether or not you can hear this is another thing and the metal domes I've used both sound excellent. The DXT of course has very low third and higher order distortion products anyway, so any IM product would most likely be off the audible radar and the DQ has a reasonably well controlled dome along with low HD, so again it's unlikely to be a problem.

[RockLeeEV]

Originally Posted by lduarte1973

@ RockleeEV the ral is out of budget , the neo cd3 could be , what do you think of the BG neo 3 PDR ?

It's a fine tweeter, and a better option than pretty much any dome for such a high crossover point. Compared to the fountek, you may lose some slight top end "air" - which in turn will have less top end air than the 70-10D. Air is overrated though.

I'm not sure the RAAL is out of budget though. Definitely do your research because the 70-10D is significantly cheaper than the 140-15d

Your last paragraph is what I am chasing. The reasoning behind this is in investigating what causes my wife to dislike most speakers and many amplifiers. Amplifiers with lower very high order harmonics seem to do better (Rotel vs my Parasound, Hafler etc.) I believe the amp is partially masking the tweeter problem. On the test bench, with my DCX I can make it better with a 48 db LP at 20K, but that does not eliminate the amp or crossover distortion. My measured output is better, not solved. Measurements are on hold as my e-mu is crashing my PC. ( plus the DCX is not exactly HI-FI).

As far as the amps are concerned, it's probably crossing distortion at low SPLs that your wife finds offensive - it maybe it's nothing at all and entirely a speaker problem.

But I'd expect the problem with the speakers boils down to plain and simple linear distortion - sound power, frequency response, and decay. You're overanalyzing the H.D.

Measure the 0, 15, 30, 45, 75 degree horizontal and 15, 30 degree vertical polar response of your speakers in high resolution and you'll probably find the real culprits.

[thanenelson]

i have a pair of jbl 035ti on ebay right now they are very good tweeters

[tvrgeek]

Originally Posted by RockLeeEV

It's a fine tweeter, and a better option than pretty much any dome for such a high crossover point. Compared to the fountek, you may lose some slight top end "air" - which in turn will have less top end air than the 70-10D. Air is overrated though.

I'm not sure the RAAL is out of budget though. Definitely do your research because the 70-10D is significantly cheaper than the 140-15d



As far as the amps are concerned, it's probably crossing distortion at low SPLs that your wife finds offensive - it maybe it's nothing at all and entirely a speaker problem.

But I'd expect the problem with the speakers boils down to plain and simple linear distortion - sound power, frequency response, and decay. You're overanalyzing the H.D.

Measure the 0, 15, 30, 45, 75 degree horizontal and 15, 30 degree vertical polar response of your speakers in high resolution and you'll probably find the real culprits.

Actually, this shows up only with high energy sections when the horns really get on it, occasionally with strings. I think I can hear it too, but not enough to make a solid judgement. Think the first track on Harry James, The King James Version. Live horns are no problem. It is not at all just linear distortion. Tried that a long time ago.

She can pass judgement on speakers instantly. no, no, no. Only the Vanderstein 2ce and ML Sequel II passed the sound test last time we looked. ( long time ago) Both were veto on size/looks. I have Paradigm studio 20's right now as they were marginal as long as I use old Rotel's. I have been working on my speaker building skills and think my next pair can resolve the issues. First is to see if I diagnosed it correctly by fixing several existing pairs. This led me to a lot of study understanding how amps work and understanding why some did not sound as bad as others. As you suggest, I have just about given up with metal drivers.