Cone material is really sort of a non-issue. The different materials do sound different, but ultimately it is the implementation of them as a speaker that makes the difference. I am not a fan of metal drivers, but a friend brought over one of his project speakers and it uses an aluminum tweeter and an aluminum midbass and it sounds as clear as anything I've heard with vocals. I wouldn't get hung up on the material so much as whether or not you like how the speaker sounds.
+1
First of all, speaker
driver unit manufacturers easily get more models by simply putting different cones on the same motor/basket/soft-parts combination. Then (laughably) people get obsessed over the sound and appearance of the
cone, when in fact the common
motor is what dominates the sound quality. Yes, the cones sound a little different, and implementation of the crossover will (should) also differ.
Important fact: All cones have high-frequency breakup modes in the treble band. These modes sound harsh/distorted. The modes can be subdued with greater or lesser success with the crossover topology.
PAPER
The problem I have with paper cones is that they vary from batch to batch. Weight, thickness, stiffness, etc. variations lead to a skewing of the bass alignment, sensitivity (= mismatch to the tweeter's loudness), and breakup modes (= a detuned crossover). Go out to listen to any local Friday night pub band, and you can quickly identify the scratchy sound of paper cone breakup from the PA style speakers.
POLYPROPYLENE
Polypropylene cones have been criticized for sounding a bit
too smooth - i.e., dull, lifeless, boring, veiled, etc. However, if this cone is designed to have additional stiffness (e.g. on a large voice coil such as Morel, Dynaudio, Skaaning brands), then you regain detail,
and retain its positive smooth qualities. IOW, this cone is a great choice if you listen to recordings that are not so stellar sound quality (e.g. harsh). (Note that what may sound boring initially can also be an indication of a low-distortion speaker!)
METAL
Metal cones are known for their transparency and detail. Criticism of a hard/harsh treble is warranted, but only when the crossover is not well designed (such as when outsourced to an inexperienced person/company). Otherwise, metal cones are very
linear. IOW, they measure and sound very flat in the mass-loaded region (= midrange). So you get both transparency and flat/neutral response. (Note that too many listeners misinterpret distortion as detail, because harmonic distortion manifests at ever higher frequencies. So they misinterpret the metal cone woofer ringing as detail coming from the tweeter.)
OTHER
There are other materials that attempt to find a nice balance among the best qualities of the basic three. Kevlar, fiberglass, natural fibers, etc. Note that these will not be found in budget speakers.
All the above assumes also that the baffle step (naturally rising output with increasing frequency) has been properly tilted flat. Again, because the metal cone tends to rise "straightest" it has the potential to sound the most neutral. (I emphasize again that woofer breakup modes in the treble must be properly dealt with by an experienced designer.)
FREE ADVICE
My
general advice is that your prudent choice for budget speakers is the polypropylene cone woofer. There is not sufficient profit margin for the manufacturer to add the necessary extra parts required by the metal cone woofer, nor will they be concerned about batch-to-batch variation of the paper cone woofer.
Another favorite tip of mine is to gently suggest listeners stop focusing on the tweeter and treble band, and instead pay more attention to the midrange for qualities like clarity, dynamics, focus, and neutrality. IMO it is much easier to get respectable treble performance from the tweeter than it is from the midbass woofer. Also, if it is
too easy to listen to a speaker's treble and midrange bands, then the crossover has not been designed in such a way to get them to blend perfectly.
