loudspeaker impendance

[VJ]

Greebe: yes, but I lack the time, place, tools, and to a lesser extent the skills to make it myself...

About the kevlar: examining the Scandyna's I have, it seems kevlar is used only near the tip of the cone (unless they can make it so that it has many different textures). Basically, if you see the photos, the coloured part of the cone is I think the only bit that is kevlar.

[Greebe]

I don't see why Kevlar would be worse than Nomex (unless you play with fire)? Kevlar is stronger and AFAIK, ideally, a driver has absolute stiffness and no weight.

If strength were the issue, why do paper cone speakers sound so good? The answer has to do with strength to weight ratio and the dampening of those materials. Why is it so hard for one manufacture to copy the speaker driver of another.

Also, the quoted impedance of a speaker system, 1.which is a rather simplification of the resistance properties of such system, 2. should be about 1.15 x the minimum impedance so that even a 4 Ohm system should not ever reach 3, let alone 1 Ohm. Of course, the phase characteristics are important as well.

1. Resistance is the over simplification of impedance, not the other way around. Even then the standard norm is to only sweep the frequency range while recording the reactive capacitance and reactive inductance. Music is neither of these things, with the dynamic range and complex resonances occuring in real time.

2. Would care to state where you got said #'s for you anaylsis? The #'s you present are ambigious, and false. If we were to stick to the science of speaker design based in the 1980's or earlier the we'd still have speaker that sound rather inexact, muddied, colored without a means to scientifically define why speaker A. sounds awesome and speaker B. sounds like crap. It wasn't until the late 1970's when Thiel and Small developed the mathmatics and testing required to even make a hypothesis at the most basic level. Most manufactures didn't take notice of their work until the late 80's. I'm not saying there wasn't speakers that were exceptionally good back in the day, just that they didn't have the math then to define it. Even today they struggle with that. What looks good in testing, many times sounds brash, harsh, thin, tinny, boomy and/or muddy.

[Greebe]

Greebe: yes, but I lack the time, place, tools, and to a lesser extent the skills to make it myself...

I can respect that, but then again you've never been one to take the easy way out. Believe the BS retoric, the psychobable tech talk of manufactures marketing dept and what is this "skills to make it myself" you're a MURCer G*d damn it! Whom even has his pilots license now, not an easy task at all. BTW congrats

Find cheap cabinettes from another inexpensive speaker of decient construction, some old high end speakers can be got for cheap, eBay is littered with them. Thousands of DIY'er do this yearly. I would never believe you can't solder, and the rest is laid out. There are alot of DIY people in your neck of the woods that will help you, if for no other reason than because you show an interest in reproducing the best quality sound for the $. Ok space can be an issue, I know this when building my old 5 way towers in the livingroom/balcony in an apt no less.

About the kevlar: examining the Scandyna's I have, it seems kevlar is used only near the tip of the cone (unless they can make it so that it has many different textures). Basically, if you see the photos, the coloured part of the cone is I think the only bit that is kevlar.

Kevlar has inferior dampening characteristics compared to several other materials commonly used. The other HUGE issue with using any woven material is the strength at different vectors. Speaker cone deform at different freq's resulting in null and hot spots in the cone. The bias of the "fabric" augments this effect. Carbon fabrics or carbon/kevlar combination fabrics all are inferior materials. Most manufactures use a paper backing behind the fabric to give it additional strength and to help reduce those pesky resonances. BTW the entire yellow surface of those drivers are 100% kevlar. Tho I would agree they do look nice and is vastly better than painting them

[VJ]

Well, paper is strong: just take a sheet of paper, take both ends of the sheet and pull them: you'll have a hard time breaking it.

Thanks for the kind words about not taking the easy way out.
Well, I'm indeed not one to fall for techno babble, and frankly, I don't care what material the cones are made of, I just want them to sound good. I bought the small set of Scandyna at a shop that sells high end gear, assuming they would "not be bad". And they surprised me: nice dynamics, nice tonal reproduction, just a bit weak on the bass tones (but that is to be expected with such small drivers).
And I can compare to some things of equipment my family has (ranging from Monitor Audio, Quadral, Bowers and Wilkins to Floating Systems). Important to me is that they sound very good at low volume settings (I don't like to have things turned up too loud).

[Umfriend]

If strength were the issue, why do paper cone speakers sound so good? The answer has to do with strength to weight ratio and the dampening of those materials. Why is it so hard for one manufacture to copy the speaker driver of another.

I was (and am) under the impression that Kevlar-including cones were superior in strenght/weight ratio compared to pure paper based cones. Also, although there is a trade-off between stiffness and weight, it is not a question of a simple ratio (nothing is simple in speaker unit and speaker system design). A weightless but easily, uhm, transformable (? I mean a surface that changes shape easily) will be fast but distorting nonetheless, no?

1. Resistance is the over simplification of impedance, not the other way around. Even then the standard norm is to only sweep the frequency range while recording the reactive capacitance and reactive inductance. Music is neither of these things, with the dynamic range and complex resonances occuring in real time.

Agreed re Resistance vs Impedance. I meant to say that the single impedance figure is a simplifaction of the electronical behaviour of a speaker which changes by frequency and it also does not capture anything with respect to phase shifts in current vs voltage.

2. Would care to state where you got said #'s for you anaylsis? The #'s you present are ambigious, and false. If we were to stick to the science of speaker design based in the 1980's or earlier the we'd still have speaker that sound rather inexact, muddied, colored without a means to scientifically define why speaker A. sounds awesome and speaker B. sounds like crap. It wasn't until the late 1970's when Thiel and Small developed the mathmatics and testing required to even make a hypothesis at the most basic level. Most manufactures didn't take notice of their work until the late 80's. I'm not saying there wasn't speakers that were exceptionally good back in the day, just that they didn't have the math then to define it. Even today they struggle with that. What looks good in testing, many times sounds brash, harsh, thin, tinny, boomy and/or muddy.

The 1.15 factor relates, I did not realise, to individual drivers, not to systems (including cross-over filters).

http://en.wikipedia.org/wiki/Electrical_characteristics_of_a_dynamic_loudspeaker

For systems and including the phase differentials, the effective impedance (.i.e. the current required to output a certain voltage) at some frequency may well become rather low. I'd like to check some documents on actual speakers.

[Greebe]

I remember when PolyPropylene was all the rage. Seemed at the time if you believed the psychobabble marketing it was a godsend to enthusiasts and audiophiles alike. Until one day enough people whom said NOT, gave reason and voted PP off the market by not purchasing them. Today the only speakers found made with PP are either dirt cheap or are relegated to Car audio and marine use only. One decent characteristic of PP is that it's impervious to UV light. Perfect for what's needed in those environments.

[Umfriend]

Paper may be hard to tear (depending on the direction you apply the force) but it is not stiff: it deformes easily.

[Umfriend]

Good to see you're back on MURC BTW, Greebe.

[Greebe]

But it's stiffness to weight ratio and dampening characteristics are exceedingly superior

Heya Um, never really left, I was around, just didn't post. Others on the forum.. LOL can't seem to get rid of me, guess who's cordless phone battery always goes dead several times a week... car battery on the hip hehe

I took a hiatus for a bit, took a step back, and resumed other interests. Was completely out of the loop as far as computers went, went 8 years between upgrades etc.

Now back in the loop (soso), with a new lappy, 17.3" HP i7 most every bell and whistle, Beats audio Quad. Plus during my hiatus went to planet Android, playing with things of that sort. Now have a SGSII/Epic 4g Touch, which I love since rooting, running Blazer Rom 4. Resumed my interests in Audio, speaker design after stepping away from that 19 years ago when my son got sick. He has my interests also, tho can't seem to understand that you cannot turn the volume control to MAX and expect any speaker to deal with it. Son, voice coils are not to be made into burnt Slinky's! Doesn't know how to operate a stereo, but does figure out that these buttons over here make the music change and these over here make it get louder, Yes much louder!

The housing explosion / implosion hit us hard, prices skyrocketed, now normalizing, but much higher than several years back. No pay raises or even cost of living increases until this last Jan. A whopping 3 freakn % in 5 years, with 2% befor then WooHoo LOL
I doubt the 2% would have come through if they'd realized the bubble had popped and the colaspe had already occured. At least we weren't unemployed like the millions of others still looking for work

[Greebe]

One thing I haven't mentioned, it's about speaker cones. Some manufactures want you to believe that (solid) pistonic motion is paramount to low distortion accurate reproduction. Simply not true. Another misgiving is that people do not understand is how sound is propagated from the cone. Most all believe incorrectly that sound comes only from the in and out motion. It in reality propogates through the cone like a wave, creating a ripple like in a puddle of water. One of the areas on interest in design is this, and howto properly control this. One really bad nasty is that once the wave front reaches the outer edge of the cone a massive change in mechanical impedance occurs, which are then reflected back toward the voice coil which causes a type of ringing, coloring or nulling out the wave you want to hear. This causes huge losses in converting the actual electrical energy into physical sound. Typical ineffeciencies are on the order of 99% loss.

Now paper may be floppy flat, but on edge is seriously strong, whereas any woven material (other than what has already been mentioned) has virtually no strength on edge. it's strength only comes from the glue/epoxy/adhesive used. Speaker cones are not exposed to tension forces like the body of a race car for example.

Two major cone types are used today for bass/ midrange drivers, one is the flat cone, typical of many alum cone woofers, and what is called Curvilinear which makes a log curve from the center outward. The later is most excepted design, whereas the flat design causes ringing and other unlikable tendencies, due to poor dampening of metals used. Normally relagated to designs which use very steep crosovers to negate this effect.

[Greebe]

Here's another whimsy that popped into my head, check out what is known as "split cone". Ages ago (1930-40's?) it was discovered that if the cone of a driver is cut radially into say 5 segments and reattached to reform the cone, the speaker sounds better, lower distortion. When mentioning above reawakened this cone cutting as to why it makes a difference. Well as it happens to be, those pesky nulls are knocked down due to the mechanical impedance change cross section of the cone. Typically finding an odd # of cuts, typically 5.

You can still find these speakers, they are high end point source full range drivers. Caution, they can be fantastically expensive.

[Greebe]

Read up on the Ohm Walsh speaker of the late '70's. Incredible sound from what appears on the surface to simply be a speaker placed upside down on top of a box. What I mention above is fully demonstrated by just how it works and how bloody difficult it is make. A design that is still being studied by science