Does Tweeter Diaphragm Matters?

[sreten]

Hi,

Nobody asked about ribbons, and they don't have the issues of domes.

Berrylium (oxide) is highly toxic, consequently very expensive to work
with. AFAIK in some "Be" domes its only present as a trace in the alloy.

As your only interested in stiffness/weight, not strength, atomic number
elements 4, 5, and 6 are interesting, berrylium, boron and carbon. The
ultimate material would likely be based on carbon tube molecules, but
the current vacuum deposited diamond lattice is not too bad, expensive.

Typical hard domes are magnesium / aluminium alloy with atomic numbers
12 and 13, titanium with atomic number 22 isn't that useful except as
part of an alloy, and copper atomic weight 29 as used in early domes
not that promising either, or Zinc that much at atomic number 30.

rgds, sreten,

Atomic weights are the real issue, but I've stuck to atomic numbers ....

[tvrgeek]

Valid basic comments but I think you are looking too close at just the basic material weight and not what you do with it. Very valid buyer beware, I have seen $12 "Be dome" that was nothing but vapor deposit poly-carbonate and I would bet it was aluminum anyway. ( China of course) Useless. The Focal is a $2000 tweeter and has had very good reviews.

Mass and stiffness are only two issues. Resonance and the resulting break-up modes and their Q is probably more important. All just a set of engineering problems. A wonder material does not just solve them. As an example, A stiff dome may be more likely to teeter-totter than a soft dome as some frequencies. ( Notice recent trend for "ring" radiators.) Wave propagation within the material is different. As the consumer/system integrator we should really just be looking at results and let the fine folks building the drivers do their job and not be forced to jump on a catch phrase even if they know it is wrong. "Cloud Computing is cheaper". Tilt. I said I don't like Al domes. I am building a pair with Seas 27T's in them right now. For the intended use, it was the correct solution.

Be is OK to deal with as long as you don't breath or eat it. Fondling your domes would be OK if you washed your hands. ( I used to deal with tape drives that had Be capstan wheels, so I am quite familiar with the issues). Disposal may be another matter.

Yea, ribbons don't have the issues of domes, they have plenty of their own! The inherent problem is not the ribbon, it is the cost. My observation is a ribbon is about ten times the cost of a comparable dome. $3000 vs $300 and I bet the dome wins at that price. Please, prove me wrong, at your expense of course.

I would like to see what could be done with Boron fiber cloth. It is industrially available as it is used in fishing rods. Pure carbon cloth has not been shown viable as a carbon-protein (silk) has been quite successful. Another carbon based material still has shown to be a fantastic engineering material. It is a hollow cell structure based composite, paper. Another material that might be interesting is aerogel. A silicon based structure that is over 99% air. Yo do lose some of that advantage when you bond it to a suspension. Cloth does not have that issue. It is an exciting time in materials technology. On the diamond and ceramic oxide domes, the ones I heard rang like a freeking bell. It would take considerable work to tame them. I don't intend to try but others may be successful.

[vacuphile]

I have heard and measured both good metal domes and good soft domes, really no principle issue. Which baffles me to this day. The thing I don't get is how you can move a dome shaped piece of cloth around at 15Khz, and get pretty much the same result as with a super-rigid Be dome. The latter behaves as a perfect piston all the way up to a (very high in the case of Be) break up mode. The dome shaped piece of impregnated hankerchief most certainly will not behave like a perfect piston at any frequency. How can the results be so similar?

To answer the original question: there are good hard domes and good soft domes, it all depends on make and model, but why this should be the case confounds me. Utterly.

[DBMandrake]

Originally Posted by tvrgeek

Valid basic comments but I think you are looking too close at just the basic material weight and not what you do with it.

I have to agree with that. Often a lot of emphasis is placed on exotic materials (especially in advertising) but generally its design topology and implementation that matters more than inclusion of some specific exotic material.

Exotic dome/cone materials on their own don't guarantee good results, nor does absence of "exotic" materials imply the results can't be good.

For example there are a lot of high tech materials used for midrange driver cones these days and yet one of the oldest and "lowest tech" cone materials around is paper, (first used for speakers in the 1920's) and by all accounts a well treated and designed paper cone can still perform right up there with the best of modern materials. (Some might even say better, since paper generally has better internal damping than many other materials like metals and kevlar...)

Likewise ribbon tweeters don't use any exotic materials, (unless you count the neodymium in the magnet) with the diaphragm material simply being soft extremely thin aluminium. What is different is how the diaphragm is driven, with the entire foil diaphragm surface suspended in the magnetic gap.

Yea, ribbons don't have the issues of domes, they have plenty of their own! The inherent problem is not the ribbon, it is the cost. My observation is a ribbon is about ten times the cost of a comparable dome. $3000 vs $300 and I bet the dome wins at that price. Please, prove me wrong, at your expense of course.

$3000 ? Where on earth are you looking

Aurum Cantus G2: (96dB/w/m)

Aurum Cantus G2 Ribbon Tweeter 276-402

$218 each, before last years neodymium price hike they were $150 ea. I've had a pair since 2004 (although they were around $300 in 2004) and I'd consider them an excellent performing small ribbon with a modest price for their performance. Big enough for a large 3 way system but small enough to have decent vertical off axis performance. (50 mm long ribbon)

Aurum Cantus G2si - the smaller model refered to by wolf_teeth earlier in the thread:

Aurum Cantus G2Si Ribbon Tweeter 276-400

$139 each. A bit lower in sensitivity, power handling and SPL, not big enough for a large system, but more than adequate for a small 2 way bookshelf design.

Aurum Cantus G3:

Aurum Cantus G3 Ribbon Tweeter 276-412

$229 each. Similar to the G2 but twice the vertical ribbon length (100mm visible) much higher power handling, 100dB/W/M sensitivity, but somewhat directional vertically, perhaps a bit too directional for my liking, although I haven't actually heard a pair.

None of those I would consider particularly expensive compared to high end domes.

Raven's have a reputation for being very expensive, so I had a quick look at their prices too:

Raven R1.1 - $332 each:

http://www.theblueplanetstore.com/Pr...uctCode=R1%2E0

The R1.1 is comparable in size to the Aurum Cantus G2 but to be honest I think the G2 is a better performer for a better price. The R1.1 is 94dB/2.83v/M but it is 2.6 ohms, so the effective sensitivity is only about 88dB/W/M, while the AC G2 is actually 8 ohms so genuinely 96dB/W/M.

Raven R3.2MMX - $2,240. Ouch:

ORCA Design & Manufacturing

Ok so this is the only ribbon tweeter I can find anywhere near $3000, but we're talking about a very large device with a 170mm long ribbon, in fact it's larger than most mid range drivers Not really a tweeter then, as its huge and designed to be crossed below 1Khz. Personally I would never use a ribbon this big, and I don't even count it as a tweeter.

Good ribbons can be had in the $140-$250 range, with some cheaper ones as low as around $100, so I think its fair to say that $3000 or 10x the price is quite an exaggeration.

[DBMandrake]

Originally Posted by vacuphile

I have heard and measured both good metal domes and good soft domes, really no principle issue. Which baffles me to this day. The thing I don't get is how you can move a dome shaped piece of cloth around at 15Khz, and get pretty much the same result as with a super-rigid Be dome. The latter behaves as a perfect piston all the way up to a (very high in the case of Be) break up mode. The dome shaped piece of impregnated hankerchief most certainly will not behave like a perfect piston at any frequency. How can the results be so similar?

What results are you referring to ? Frequency response ? Try measuring the cumulative spectral decay of the two and you'll see very different results between a soft dome and a stiff metal dome....

All soft domes have significant resonances as low as 6Khz, in fact they are operating in cone breakup throughout the top 2 of the 3 octaves they cover typically. Not so for a stiff metal dome but then there will be a harsh breakup just above the audible range.

[Boden]

Different CSD results for soft vs hard domes?

No you don't anno 2012 except for the infamous metal dome breakup anywhere between 18 and 25 kHz or higher, depending on material and shape.

The German Magazine Hobby Hifi has published literally dozens of tests the last 6 or 7 years, comparing measurements of various dome tweeters.

It is almost scary how well a 25€ Vifa 25 mm dome of the latest design performs.

Regards,

Eelco

[rob g]

The 2 inch titanium inverted dome in the Pluto 2.1 sounds so sweet with it's ultra low resonant frequency.
I think too much is made of the distortion in the ultra high frequencies where most of the older male listeners (30yrs plus) hearing has long since fallen off a cliff, not to mention the lack of energy to reproduce in most music above 12khz, let alone 18khz and above.
I used to be firmly in the soft dome camp, I have heard enough speakers to know this is unfortunate prejudice. Of the Dome drivers metal diaphragms have typically proven smoother and cleaner than many soft domes. I have heard great examples of both.

Ultimately factors like the motor system, diaphragm size and dispersion are probably more important than the diaphragm material. I was blown away with the quality of the treble (smooth, sweet, lack of harshness or spitty breakup, and excellent detail) produced by the Pluto and its $20 fullrange inverted cone tweeter.

[oiphy]

The short answer for me at last. NO. its your ears that matters. I live in Norway and tried pretty mutch all of seas, vifa and scan-speak in the last 10 to 15 years and 2 of my favourites ( seas 27 tff and scan-speak 2905) is very different and not the most expensive nor do they have perfect charts.....still they work perfect for me.
sorry my bad english

[tvrgeek]

DB,
OK, I will try one of these again, but the G2 I heard sounded like a $12 poly-carb dome. It could be the more expensive units are gone as no one bought them.

Rob,
I am well past the half century mark, and I can hear 18K clearly. I know because I was testing some tweeters the other day and was actually surprised how clear it was. When I was 20, I was tested to over 20K. I have been careful to protect my hearing. I fear most of the 20-somthings have lost far more than I because of sealed ear buds. They have been shown recently to be very bad, even at what you think are very reasonable levels.

[tvrgeek]

oiphy,
No apologies needed. Most Americans with high school diplomas and many with college degrees can't speak English, let alone a second language. I was listening to a congressional representative the other day, and she could not.

ttf eh, I have been playing with the 27TBFC/G. Coming out OK, but I think I like the Vifa and HDS are better. I want to try a 2904. I see they just introduced a Be dome, D3004.

For your signature, it is "through".