Sound Quality Vs. Measurements

[a.wayne]

Originally Posted by ThorstenL

Hi,



You are confusing many different issues.

Err, No , dont think so ...

Originally Posted by ThorstenL

Hi,

High Efficiency does not necessarily means "Horns".

Never said it meant only horns ...

Originally Posted by ThorstenL

Hi,
Past that, you are suggesting the HE Speakers are always loud, that is, that they play low level sounds louder than lower efficiency ones. Now with respect, there is simply no physical mechanism in the kind of electromechanical system represented by a loudspeaker.

What i said was HE Horn speakers , not HE speakers per se ....

Originally Posted by ThorstenL

Hi,
What exists however is a mechanism that produces attenuation at very low signal levels, namely hysteresis in the suspension. For high efficiency speakers lossy and high hysteresis surrounds and spiders are a no-no, you loose too much efficiency in the process, so one has to either live with the resulting un-damped cone resonances or find different ways to solve them.

In contrast, in current low efficiency "HiFi" Speakers Spider and Surround are often deliberately made lossy, to damp out resonances. In the process they also often acquire hysteresis.

Hysteresis just as thermal compression is quite easy to measure if you have a anechoic chamber with sufficiently low noise level. Simply use sweeps starting from a level just below your measurement limit (often microphone imposed), like 20dB SPL and run each sweep with precisely 10dB increase in SPL. Normalising the 10dB steps out is easy. Then you can very easily see compression and hysteresis losses at low and high SPL's.

One thing that is often true is that high efficiency systems have a better linearity with SPL/power changes than low efficiency ones, though it is not an absolute truth, more a 70/30 kind of gig.

Another issue is the way resonances are treated. If you resort to heavy handed damping them out (pretty much staple for HiFi Drivers) you reduce not only amplitude but also Q of the resonances, so they are lower in level but much easier excited.

In the end driver design is an extremely complex discipline (and few designers are consciously aware of all the different angles). Funnily enough, most of the issues with Speakers are comparably easily to measure (passing nod to Mr. Klippel) and to correlate to listening experience.

Yet most of those who constantly strain at minor issues in electronics performance routinely swallow the whole camel of speaker performance and deny that it's a camel or that they swallowed it too...

Oh well. As Charles Lutwidge Dodgson once wrote: "Such is Human Perversity".

Ciao T

Best to define what is Low /mid/HE then we can move on to apple vs apple discourse ..

[a.wayne]

Originally Posted by ThorstenL

When designing a speaker I always listen to candidate drivers naked lying on the floor, no XO, no EQ, nothing. Anything that has obvious objectionable sonic flaws I exclude (which is most), simply because I know I will have to fight the driver, fight it's problems to get descent sound, instead of being able to work with the Drivers to maximse what they do well.

Yes voicing is very important ....

Originally Posted by ThorstenL

In those tests the Audax HDA Cones failed miserably, while the Audax doped paper cones and (to a little lesser degree) woven carbon fibre cones passed very well.
Ciao T

Reality , paper sounds best IMO, of course I have had good Poly,FG and CF speakers that worked , but paper is still my favorite ..

[vacuphile]

Originally Posted by ThorstenL

Hi,



Hold it.

1) Qms is a measure of loss of the RESONANT system at the fundamental resonance. How this loss occurs is a totally different story.

2) True, but if we (just use one example) use a flow resistance integrated into the basket, our stiction is at the level of a single Nitrogen Atom...

3) Nope, it ain't actually, work out the proof yourself.

4) High Qms is only a good indicator of this if specific (poor) design techniques are employed. I am not suggesting that such options are a good idea to obtail low Qms.

5) However that does not invalidate my point that the mechanical resonant system should be in a linear fashion and and by mechanical means be critically damped, in favour of attempting to damp it electrically through the Amplifier.

Ciao T

Because Thorsten took out some selected sentences, taking out the original logic into which they where placed, I feel forced to repeat myself all over again in duplication for a second time:

(post to which Thorsten reacted)
Qms is just a measure for the amount of friction that dampens cone movement. Low Qms=much friction. Now, there is no such thing as linear mechanical friction without stick, so the less mechanical friction, the better it is. Leaves open one other source of friction: voice coil induced. Why do you think there are stil VC's around with organic formers? The reason is to prevent the occurance of eddy currents, which not only cause friction, but also introduce non-linearities. Thereby, high Qms is a good indicator for the relative absence of distortion causing mechanisms.

(my reaction to Thorsten's reaction, as numbered by me for convenience)



Ad 1.) Yes, that's how you measure Qms as a proxy for friction in the system.

Ad 2.) You mean like in a pierced pole filled with some dampening material, with the dust cap working as a piston? Has been tried, does not work. After all, high Qms is no problem anyways, since driver can (and should) be controlled by enclosure and electronics only.

Ad 3.) Don't remember where this refers to, but it is never a substantial argument.

Ad 4.) All forms of friction lead to non-linearities, and though some forms might be more benign than others, they all lead to distortion.

Ad 5.) Since Qes is always lower than Qms in even the worst speaker I ever measured, speakers are always mainly controlled by electronics and the box. What's wrong with that? It is rather the opposite. The more your electronics are able to control cone movement, the better it is. Apart from the distortion caused by friction, that is another reason you want to avoid it. It stands in the way of the original signal controlling the exact movement of the cone. In other words, for this reason alone, high Qms is a goal in itself.

vac

[Wavebourn]

Have you seen this one?

[a.wayne]

Sealed or vented .... ?

[Wavebourn]

Originally Posted by a.wayne

Sealed or vented .... ?

Short horn. Very short.

[ThorstenL]

Hi,

Originally Posted by vacuphile

Because Thorsten took out some selected sentences, taking out the original logic into which they where placed, I feel forced to repeat myself all over again in duplication for a second time:

Let me put it this way.

First, your logic is based on a false premise, namely that the current Amplifier-Speaker interface (Voltage) is defined correctly and is beneficial and should be used in preference to alternatives.

With that fundamental flaw and the use of dynamic speakers "contra naturam" the rest is pointless. You are debating details of putting the horse behind the cart with someone who is looking what it takes to put the horse where it belongs.

Second, your logic lacks any demonstration of the leaps and bounts it takes. In other words, you do not demonstrate logically that A follows from B and C follows from B, you claim so and incorrectly.

Third, my comments are not based in this context you use, but in one where Speakers are driven correctly, in accordance with the nature of the device. Moreover, I have experience with such systems as well as with speakers where the fundamental resonance is damped by mechanical means, so at least I know what I am talking about.

Now to some specific points:

Originally Posted by vacuphile

Ad 1.) Yes, that's how you measure Qms as a proxy for friction in the system.

Just because you measure damping does not mean it is based on friction in the suspension. There is no such direct link. All you can do is to measure Qm and state that the system contains X mechanical damping with Y Linearity. You cannot in fact determine from the measurement how this damping is applied.

Originally Posted by vacuphile

Ad 2.) You mean like in a pierced pole filled with some dampening material, with the dust cap working as a piston?

No. I mean the way in which it has been applied in german Studio monitor Drivers since the mid 1930's up to 1992, when the final inheritor of the Eckmiller legacy in Berlin closed doors.

Originally Posted by vacuphile

Ad 4.) All forms of friction lead to non-linearities, and though some forms might be more benign than others, they all lead to distortion

So, what is the level of non-linearity introduced by a flow resistance. Hint, in east Germany we used flow resistances also for making cardioid Speaker columns that where cardioids down to around 150Hz, so I know how non-linear they are...

Originally Posted by vacuphile

Ad 5.) Since Qes is always lower than Qms in even the worst speaker I ever measured, speakers are always mainly controlled by electronics and the box.

Qes is a very poor way to not "control" the speaker. Plus, if you think Qms is nonlinear, try measuring Qes nonlinearity.

What Qe attempts and miserably fails is to correct a mechanical problem by simple electrical means. In the process it actually causes by far more gross distortion all across the bandwidth of the speaker, while still failing to critically and consistently damp the cone at all signal levels and frequencies.

Originally Posted by vacuphile

What's wrong with that? It is rather the opposite. The more your electronics are able to control cone movement, the better it is.

The only problem is that your electronics cannot control cone movement through Qe and low source impedance.

Cone acceleration (and thus audio output) outside the frequency range around resonance is proportional strictly and only to voice coil current and magnet field/suspension linearity.

So Qe is not in the picture, only Re. And Re can be taken out of the picture (together with Qe) by current drive.

Now, lets look at the fundamental resonance frequency region (which is quite narrow in range). Does Qe control cone movement directly and in a linear fashion? Nope, it is in fact heavily signal envelope dependent and modulated by excursion (where usually larger excursions decrease damping).

Contrast this with damping by a flow resistance integrated into the basket, it has neither appreciable stiction nor non-linearity with level and driving the speaker with current.

In one fell swoop we have eliminated:

1) Thermal Compression (which is hotly debated but real neverless)

2) Eddy Current (in the pole piece) induced distortion (which is odd order and cubic law and leads to often observed preponderance of H3 over H3 in the midrange for many drivers)

3) Low Frequency non-linearity, which is caused by suspensions and electrical systems that are highly non-linear.

If we combine this with a magnet system that has a constant field strength for the range of cone travel of interest we will have made a Speaker system that has a dramatically improved performance in almost all relevant domains.

Of course, this system would be incompatible with common amplifiers, however, unlike the situation three or more decades ago when amplifiers and speakers where separate, active speakers are becoming more common.

However this debate about how to optimise the Amplifier/Speaker system using unconventional, if superior means is already present in several threads on that topic here. including this more recent one:

The Secret of Tube Amplifiers Revealed - and much more!

So no need to drag it in here, where generally conventional systems are debated, or to then take my comments on Driver Parameters in threads discussing current drive out of context to make it seem as if there is a contradiction and to them complain when I address not your flawed logic, but deal with the individual contentions you have raised.

BTW, my noted to the hysteresis effects in low efficiency systems in this thread here referred mainly to the system behaviour outside resonance region and to the results of attempting to damp cone resonance with the rubber surround...

Ciao T

[dvv]

Originally Posted by a.wayne

Yes voicing is very important ....

Reality , paper sounds best IMO, of course I have had good Poly,FG and CF speakers that worked , but paper is still my favorite ..

Funny, you are one of many who think so, including me. It's odd that so many people should agree on a point, yet the industry remains deaf and dumb, probably wondering why is it going down.

I would imagine that in real life, all these space technologies in fact cost less than traditional paper cone, although we are made to think exactly the opposite. Wouldn't be the first time.

I still remember only too well my ancient AR5 speakers - their bass quality, with their 10" woofers, was honestly second to none in those days. In all honesty, I can claim that my present, aerogel based 10" woofer is a bit better, but that bit is way too small for the 40 years of development in between.

In most cases, I still prefer a doped paper cone to all these fancy materials.

[ThorstenL]

Hi,

Originally Posted by dvv

Funny, you are one of many who think so, including me. It's odd that so many people should agree on a point, yet the industry remains deaf and dumb, probably wondering why is it going down.

In fact, another datapoint. Many of the really ultra-cheap simple paper cones, with fairly thin uncoated paper and significant measurable breakup nevertheless sound surprisingly natural (including my "open air" test), while a similar plastic cone drivers, despite having much superior response flatness and all sounds like a duck quacking and very obviously and unnaturally coloured!?

Incidentally the (justly) much maligned Yamaha NS-10 also used a paper cone, probably (together with fairly low distortion and good impulse response) the only saving graces...

Then again, the Speakers I listen to now have drivers that I had some small design input into (except treble which is OTS) and are surprisingly high tech/space age for such an old reprobate as myself. The actual design was done by someone rather justly famous for his work with metal cone speakers, but possibly a bit too grounded in the traditional approaches.

The woofers have a low loss "bicycle tire" surround, a rather stiff spider a partial sandwich cone with a single piece ceramic oxide coated alu inverted dome covered in the centre 2/3rd of the cone diameter with carbon fibre reinforced paper cone layered and the pure alu/oxide for the outer parts. it's pretty much flat to 1KHz before it rolls off smoothly. They are more Sub's than woofers but do woofer duties quite well.

My main contribution was to ask for a vented overhanging pole piece, extra venting around the voice coil (as much as possible), a big voice coil diameter (I normally prefer 3 -4" for woofers, but can accept 2", barely) and a low Mms/BL ratio (<5), plus extended higher frequencies...

The midrange are actually 50Hz-15KHz 5"Diameter fullrange drivers with a very lathe voicecoil, neodymium magnet and alu/oxide cone with seperate alu/oxide dome.

The driver designer had never before designed full range drivers and early samples sounded promising in terms of dynamic range and bass output (for a small driver) but had a rather nasty and edgy tone to them making them u nsellable as "Full Range".

By shifting the unavoidable breakup resonances around (this was for example a case in Audio where I just pointed and said "change this and that in this way" and it was much better afterwards) the driver ended up sounding very natural, if a touch polite (I dislike stuff that jumps up to bile my ears off). Waterfall still looks quite hashy at higher frequencies (> ~5Khz) but does not sound the way it looks.

These drivers where quite expensive, more expensive than paper cones and are either sold out and will not be manufactured again or will not be restocked once sold out...

Given the use in a speaker that uses first order electrical crossovers (series, no conjugates or EQ used) the characteristics of the drivers to all be able to run "crossoverless" without sounding bad make a major contribution to the end result. Most more common "HiFi" drivers would have made quite bad sound using such a design... ;-)

I just wish for 6dB or so more efficiency, over the 89dB/1W/1m I alread have.

Originally Posted by dvv

I would imagine that in real life, all these space technologies in fact cost less than traditional paper cone, although we are made to think exactly the opposite. Wouldn't be the first time.

The issue is mostly one of consistency. If you make cheap stamped frame < 1 USD per pc in 1KU 4" Drivers for cheap speakers you can accept quite a high level of tolerance (wide tolerance).

But if you are making 50 USD per pc in 1KU "high end" 6.5" Driver you need quite tight tolerances, so you end up rejecting more cones than can be put into speakers and still have 30%+ rejection rate on the final drivers. If you instead use some "High Tech" material with great claimed cost and benefits (all of which are BS of course, sorry, marketing I meant to say) you probably get a 100% acceptance rate of the cones you buy in and > 90% on final drivers.

So in the end the single paper cone as such may be cheaper than the space age cone, HOWEVER, the final accumulated cost per Driver is often much higher than for artificial materials.

Originally Posted by dvv

In most cases, I still prefer a doped paper cone to all these fancy materials.

Amen.

And often even an uncoated paper cones and non-lossy surround (corrugated cloth) at that...

Ciao T

[vacuphile]

Originally Posted by a.wayne

Yes voicing is very important ....




Reality , paper sounds best IMO, of course I have had good Poly,FG and CF speakers that worked , but paper is still my favorite ..

Vifa has a relatively recent line of drivers out that uses paper cones in a very advanced magnet motor design, with excellent specs. They sound well too. Have unfortunately not had time to build with them, but for those who like paper cones, it would be a serious option to consider for a new building project.

vac