How much impact does driver material actually make?

[DVDdoug]

I’ve read some reviewer comments about how much they dislike aluminum tweeters.

Probably because they know it's aluminum... No blind listening tests? I don't know if any reviewer has the guts to do a blind review and write their impressions before they know what they're listening to.

There are lots of variables, trade-offs, and design decisions, and every speaker sounds different and we don't know how much of the difference can be attributed to the material choice. That's true for speakers, amplifiers, cars... everything...

And of course, the manufacturer will tout every design decision as a feature or advantage.

Here's a quote from Amir:

I don't know why people are so fascinated with how some speaker/headphone is made. What matters are the results.

 

[sq225917]

If done badly yes. You wouldn't make identical cones, geometry wise, from each of those materials if chasing an optimum design for each. You'd alter the design to optimise the cone for the characteristics of each material.

I've heard some cuppy sounding polypropylene cones of old, but that's the only characteristic I've ever been able to assign.

I've heard perfect and bad metal dome tweeters, it's not the material, it's the designers choices.

 

[Arindal]

My current speakers (MA Silver 100) use ceramic coated magnesium aluminum alloy material. I can’t tell the difference from coated paper material but apparently some people can.

If the driver in question is operating at smaller wavelengths compared to its diaphragm size, differences between stiff and flexible material are more likely to be audible. That is particularly true to tweeters and midrange drivers operating at higher frequencies.

Would say it is less likely to identify a characteristic sound of the specific material, but rather its influence on directivity, resonance and other driver properties. Ceramic magnesium aluminium alloy sounds like a rather rigid diaphragm, which will usually cause continuously narrowing directivity towards higher frequencies. A more flexible one like paper or polypropylene might be more gentle in terms of direcitivity, depending on the shape. In any case, geometry is key.

If the driver size is smaller compared to the wavelengths it is producing, it is less likely to have a significant effect. Inner damping can play a role here but it is not always audible.

There are some tweeters made of titanium which some consider superior to aluminum.

It is too general. Both metals show tendencies of resonation and breakup which can have an effect on the audible band. To which extent this is leading to characteristic sound, is very much depending on the dome geometry. Lighter or stiffer materials on one hand (Beryllium, solid ceramic) or flexible ones (silk) are less likely to cause such breakup within the audible band.

Would say from lots of experience that there are differences in midranges and tweeters, but you cannot prescribe it solely on the material. The affected frequency bands and geometry are of similar importance.

 

[DVDdoug]

P.S.
I could be wrong, but I think the Floyd Toole quote in my "signature" below is related to listeners saying that beryllium tweeters sounded "metallic".

 

[egellings]

I think that so long as the cone remains rigid so that it acts like a piston, then there should be no difference in S.Q. Different materials may show different breakup modes, giving them a signature sound.

 

[Purité Audio]

Drivers must be kept within their pass-band, just buy properly designed loudspeakers.
Keith

 

[2020]

I think driver material makes a big impact, but it's really a symptom of another variable at play.

The question should be "how much impact does BOM (bill of materials) make?".

If it's a low budget, well, you can't get everything. The design phase can only implement so much before they run out of money. So you will be exposed to aspects that fell by the wayside which will mean cheaper drivers or a double edged sword decision (such as metal tweeters that are harsh).

On the flip side, if the budget is really high, then they can address problems and speakers can start becoming homogenized. Take house sound into account as well though, there are different definitions of "perfection".

I don't think it's always a matter of "this one sounds worse than that one!", more like you can have a comfortable baseline but you can still do much better if you really want to. That's why simple soft dome tweeters never die for one. They are just too efficient and mature. They are good enough to start with. You could have better by moving to metal or more advanced designs, but it's not like you're going to be objectively suffering with soft domes.

 

[Arindal]

I think that so long as the cone remains rigid so that it acts like a piston, then there should be no difference in S.Q.

A lot of midrange cones and tweeters are actually not acting like a piston in the higher region of their usable freq band. Particularly those with a diaphragm which is not completely stiff. Even way below breakup frequency, they show directivity behavior indicating a non-pistonic movement.

listeners saying that beryllium tweeters sounded "metallic".

Beryllium offers excellent properties allowing the driver designer to push the breakup and resonance problems far beyond the audible band, so ´metallic´ in terms of resonance or distortion is pretty unlikely.

There is some sort of truth to this statement, though, as several Beryllium tweeters tend to show a very flat dome geometry, some with rather small diameter or voicecoil former diameter, which as a result is complicating the combination with a waveguide. All this contributes to a broader dispersion pattern in what is typically the lowest octave of a tweeter (3-6K) compared to higher bands. In some rooms this might lead to pronounced reflections being regularly described as harsh or metallic. Has absolutely nothing to do the the material, though.

 

[d3l]

Pretty much each and every time I find highs harsh and tiring on a speaker its an aluminium tweeter. Can't say why so but this has been the case so far.

 

[Heinrich]

Pretty much each and every time I find highs harsh and tiring on a speaker its an aluminium tweeter. Can't say why so but this has been the case so far.

Some people go as for to tell that aluminium domes sound like a frog clicker. True, but only once ;-)

KEF uses an 'elliptical dome enforcement' which is more effective than diamond material. And the 'tangerine waveguide' prevents from the frog clicker effect either. It's not the material, it's the engineering.

 

[Purité Audio]

Pretty much each and every time I find highs harsh and tiring on a speaker its an aluminium tweeter. Can't say why so but this has been the case so far.

Poor speaker design nothing to do with the material.
Keith

 

[d3l]

I've never heard the kef metas, would be interesting to see what they have achieved with the waveguide and other tricks.

 

[Heinrich]

I've never heard the kef metas, would be interesting to see what they have achieved with the waveguide and other tricks.

No tricks, you simply won't hear them:

First breakup seems to be at 39313Hertz, well beyond human hearing. One may compare to exotic materials, up to synthetic 'diamond'. If my recollection doesn't trick me, KEF works with aluminium and structural re-enforcement called 'elliptical ..."?

The mic used doesn't by far get the 40kHz right, but somehow records something reliably (bats in the backyard and so forth).