Engineering anything (whether a speaker or a car) is a series of complex compromises and choices and the answers chosen will vary with the intended use.
For example, which is faster for a 200 mile trip - a Greyhound bus or a Porsche? You can't really answer that question until you know more about the trip. If 40 people need to make it, the Greyhound bus is going to be a lot faster no matter how fast the top speed of the Porsche.
Take just a single factor in voice coil design. The impedance will vary with the length of the wire (among other factors.) A longer wire raises the impedance and gives a more concentrated magnetic field, but also increases the mass of the coil. So we have a balance that needs to be struck - you can't have both any more than you can put 40 seats into a Porsche.
For most consumers, it is best not to worry about the engineering issues the speaker designer faced. You're better off listening to lots of different speakers and you'll eventually find one where the design goals (with the inherent compromises) closely align with the strengths you find important in a speaker. Keep in mind the others will have those priorities in a different order. That helps explain why there are probably 1000 different makes and models of speakers on the market today.
Thank you for your explanation. Does this mean that in fact a low impedance design gives a more fast and dynamic response (with the restriction that one should use a kilowatt amplifier)?
Other than your needing an amplifier that will behave itself at very low impedance loads, it is not possible to give a simple answer.
The impedance versus wire mass (length) is just one of =many= factors that affects impedance. Crossover design affects impedance. Cabinet design affects it. The other parameters of driver design (magnet strength, gap distance, other voice coil materials, suspension, cone material/mass... etc., etc., etc. also affect it. It is a juggling act for a designer to gain the attributes they want without losing too much ground elsewhere.
And with that, we haven't even gotten to the more exotic driver designs such as planar, electrostatic and so on.
I think it is a mistake for an end user to get wrapped up with technical issues that can be difficult even for professionals. To declare a speaker will be "fast and dynamic" based on a single spec is a simplistic mistake.
I'll be up front and state that I have no idea why Kinoshita speakers exhibit a low impedance. As noted, the voice coil wire length was simply an example of one of many factors. Their impedance spec may well be due to something else. I've not heard them and would find it impossible categorize their sound based on the fact they are low impedance.
I'll restate it this way. Technical issues are very important considerations in helping the designer reach his goal. But without knowing the design goal, specs by themselves can be quite misleading.
I believe it's mainly because they want the box a certain shape (narrow). If the speaker box can be made whatever size the deisgner wants (wide but not aesthetically pleasing) then a lot of trade-offs can be eliminated.
My guess is that, in the case of the big Konishita speakers, the designers perceive a worthwhile advantage in wiring many voice coils in parallel instead of using some other configuration. For one thing, the amplifiers will deliver a lot of wattage into this configuration - or die trying!
When confronted with having to choose between wiring for a 4-ohm load vs a 16-ohm load, I chose the 16-ohm configuration. My priority was compatibility with specialty tube amps, and I think that even solid state amps sound better into a high impedance load as long as the result isn't premature clipping. Apparently I'm very much in the minority here.
Seldom is the impedance curve one of the primary driving factors in a loudspeaker design; usually other things are higher priority and the impedance falls where it falls. In unusual cases (Apogee, Konishita, InnerSound/Sanders Sound panels), the speaker's impedance curve falls outside the comfort zone of most amplifiers, but in that case there are usually still specialty amplifiers that will work well, though the number of choices will of course be more limited.
Rating amplifiers by their 2.83 volt sensitivity rather than their 1-watt efficiency gives an advantage to lower-impedance speakers, at least on paper. Wired for 16 ohms my speakers are 89 dB/2.83 volts, but wired for 4 ohms they'd be 95 dB/2.83 volts. In either case, they're 92 dB/1 watt.
Believe it or not, not every designer builds a speaker so that their potential customer's favorite tube amp will be able to drive it.
Also, there are now quite a few audiophile quality amplifiers on the market that can drive loads less than one ohm without breaking a sweat. Most well-designed digital amplifiers will do that with ease.
I recall that back in the day, the Strathearn ribbon drivers were very popular and they presented a load of around 1 ohm unless they were padded with performance-robbing resistors. Some amp designers actually designed amplifiers that would drive that harsh load to take advantage of the ribbon's sweetness and transparency. So this is really nothing new. One of my friends used to modify tube amplifiers to drive such low-impedance loads.
Plato, funny you should mention the Strathearns. I used them in several different homebrew systems. The impedance of a single Strathern sans transformer was .55 (that's point five five) ohms! I used to drive one (or two in series) directly with an Electron Kinetics Eagle 2 amplifier. In fact, that little monster had so much power supply capacitance that you could unplug it and it would still play for 45 seconds.
Duke, that sounds like a neat setup you had with the Eagle 2 and the Strathearns. Yes, if a single ribbon was 0.55-ohm it's no wonder I always saw them being used in a line source in conjunction with one or two other ribbons.
At that time, some of my friends were using the Strathearns with dynamic woofer systems and others were using the Acoustats with highly modified Acoustat servo-charge amps. I, myself had a set of 2+2's and a set of Monitor III's with the modified servo-charge amps. You just couldn't blow those things up (the speakers). Those were the days!
Many ways to design a loudspeaker focusing in on any one spec and proclaiming it to be the only way to design for best performance is just wrong thinking. 1 ohm doesnt offer any benifits its just a design choice and I feel a wrong one at that....But see Mlsstl responce hes got it right. Loudspeaker designers all make such choices. So many variables to loudspeaker design why it interests me so. To me loudspeaker and audio design is one of the few places a bit of arts left in electronic design.
Fellow audiophiles, let's ask another question: very low impedances are extremely demanding with regard to amplification. Do many speaker manufacturers choose for a "safer" (more benign) impedance behaviour even if they know a low impedance design would be better instead sonically? This choice is of course strongly influenced by marketing strategies, because otherwise their products would be very hard to sell (many amplifier and tweeter failures :-) ).
Chris, you seem to have an impedance obsession!
The only way to really answer your question is to poll every speaker manufacturer out there and ask if they made some type of compromise in their design regarding impedance. Some may have, many probably have not. Many won't tell you one way or the other as they regard their design efforts as proprietary work.
The error in your proposition is your statement:
...even if they know a low impedance design would be better instead sonically
Impedance is only one part of a complex set of issues. It may have nothing to do with a particular design's sonic goals. Or, it could even hinder achieving an important goal in a particular design. For example, low impedance draws lots of current. Current generates heat in a voice coil and that heat can damage or destroy a driver. So, in some designs, a low impedance could reduce the effective dynamic range. Many people regard improved dynamic range as sonically better than impaired dynamic range. In this "for example" the speaker may well perform better if the impedance is not low!
You need to get this one-note samba out of your head. Impedance is only one fact of many, many technical issues in a speaker design. You get a good speaker only when ALL of them are well coordinated toward the design goal.
Your question (Do many speaker manufacturers choose for a "safer" (more benign) impedance behaviour even if they know a low impedance design would be better instead sonically?) I feel stable 16 ohms is far better so the answer for me is no. If 1-2 ohms designs where better sonically I would design such,not hard at all to do so.
Ok, thank you all. I was just wondering why some speaker builders are designing speakers with ultra low impedances (probably they want to look which amplifier would be able to drive or to survive them..., just kidding). I think nowadays the speakers with true 1 ohm (or less than 1 ohm) impedance are very uncommon, do you agree? Probably this has to do partly with advances in driver technology, because the peak incidence of such ultra low impedance speakers was mainly situated during the eighties (Apogee, Thiel, Wilson, Kinoshita).
Chris this is not true, current Kinoshita speakers are still using under the 1 ohm loads,. even with the current technology they themself are still the worldwide reference for true monitoring.
The Apogee Scintilla did come in two flavors, a 1 ohm version, and a 1-4 ohm version (both options, on the latter). By all accounts the one ohm version sounds better.
The extra padding down, required on the ribbons, to bring their output in line with the bass panel, takes away some of the magic from the ribbons, in the 4 ohm configuration. Of course you could do an active biamp to get around this, but...$$$$
The 1 ohm Scintilla ribbon, does not need it's output padded down to blend ....in the 1 ohm version.
Note: This is what I read....I've never owned the Scintilla.
The ultra low 1 ohm loads has really nothing to do with outdated technology, it is simply what the designer intended to design and tninks what sounds best according to his opinion.
Chris you should not thinks to theoretically, it is the total design which makes a speaker sounds beautiful,and that is far more complex then the 1 ohm load only, so many other factors !!!
Let me put it this way (and this would be my last question before I shut up): Is it with today's technology necessary to implement an ultra low impedance into ones design to get excellent sound?
Impedance is still the same variable these days it always has been. So are all the other variables.
Switch gears to fighter aircraft for a moment. During WWII the Mitsubishi Zero was one of the most maneuverable fighters around. One of the reasons was the manufacturer left off most of the armor plating that protected the pilot. The reduced weight help make the plane more maneuverable. (That's an interesting choice if you happen to be the pilot.)
Fast forward and we now have materials that provide pilot protection but weigh less. But they still weigh something and still take up room. The plane's performance would improve if you left off those materials, whether the old armor or the modern version.
So, sure. Modern materials and techniques may lessen the burden of a design compromise compared to older techniques, but that doesn't get rid of the issue.
You're still on your one-note samba. Even today, impedance alone does not determine the quality of a speaker. It is just one of dozens upon dozens of factors a speaker designer gets to juggle.
(Written as I am enjoying a gorgeous rendering of the 4th movement of Beethoven's String Quartet in G on my very 8 ohmish Spendor SP1/2Es.)
After the elucidating words from Mlsstl, Johnk, Rademaker and others it is clear to me that the impedance issue is only important if you take other parameters of speaker design into account. But I want to put something right here: you have to agree that a 1 ohm or lower than 1 ohm design mandates the use of very rugged amplification. Only a small group of amplifiers are up to the task (Krell, some of the class-D amps, FM Acoustics, Rey Audio to mention a few). This means that those extreme low impedance designs are not for most audiophiles simply because they don't have super rugged amplifiers like the ones I mentioned. Of course this has nothing to do with sound quality.