16 ohm speakers: any amp sounds better with more resolution. speaker cables less critical.
First,
Thanks to anyone who responds with whatever answers/opinions/advice comes from this. I'm retired, covid bound, Donna is taking care of everything holiday related, too much time, always curious. ..................................
I happened across this in an old thread started by Ralph (atmasphere)
"Sixteen ohms, BTW is a very simple means for getting more resolution out of your system, as nearly every amplifier made sounds better on 16 ohms than it will on 4 or 8 ohms. Speaker cables become far less critical too."
My speakers are 16 ohms (Electrovoice horn tweeter, horn mid, 15" woofer, crossover, rheostats, from 1958). Extremely efficient, I have more than enough power. Amp, now and in the past all had 16 ohm taps. Of course I can hook them up to my Cayin's 8 ohm taps now and listen, but facts, opinions, advice, to learn is good. ...........................
Lots of Questions?
1. why/how do 16 ohm speakers make amps sound better, with more resolution?
2. why speaker cables less critical? perhaps this is why I/we don't hear cable differences in my system? I'm using my homemade twisted pair of cat 5 now (8 individually insulated
small diameter solid core).
3.
to get exterior bias control: use 8 ohm tap for my 16 ohm speakers? (get alternate amp 4/8 no 16 tap,)
lose advantage(s)? 'sounds better'; 'more resolution'; 'speaker cables less critical'?
I can fine tune my speakers via their two rheostats: 'presence' and 'brilliance', so not really an issue for me.
4. Importance of Bias Control
how important is Bias? (I don't care about heat, power output, or tube life, just as bias affects sound). Frankly, using vintage tube receiver Fisher 500C, 800C and Fisher Mono Blocks 80Z, I have never checked or adjusted bias. I just put the control in the center position when cleaning insides/controls.
I have always used 16 ohm taps of various vintage tube and SS amps and newer current tube Cayin A88T. (original version, the only one with 16 ohm taps). It's bias control is internal, versions with safer external bias do not have 16 ohm taps.
5. replace their two rheostats? ('presence' and 'brilliance': copper wire-wound on ceramic body, mid/neutral position).
I have them in neutral position now, l/r frequency response equal.
do I need to keep rheostats 16 ohms? use 8 ohm rheostat with 16 ohm drivers?
sales sheet says 16 ohm, but data sheet shows range 1.0 to 5k ohms.
does that mean, the drivers will draw whatever they draw (varies thru frequency range anyway), doesn't matter as long as rheostat range starts 1.0 ohm, extends past say 100.0 ohms?
1. why/how do 16 ohm speakers make amps sound better, with more resolution?
They don't. It does change the sound and in making it more lean and etchy it can seem to be more detailed. Its not.
Because of the way they are wired its very easy for Eric Alexander to make his Tekton Moabs in either 8 ohm or 4 ohm. Everyone following the advice you mentioned told me to order 8 ohms. It will be so much better. Especially since I have a tube amp. They made all the same technical arguments you have undoubtedly heard. I talked with Eric and went with 4 ohms. Hard to imagine how these speakers could be any better.
2. why speaker cables less critical? perhaps this is why I/we don't hear cable differences in my system?
We have no idea why you don't hear differences in your system. Could be the wires you are comparing are so similar the differences are so small its too hard to hear. The differences are there, guaranteed. My first experiment was with ordinary 14 gauge lamp cord, two runs shotgun vs one. Not much difference but it was there. Everything from that point on has been orders of magnitude greater and easier to hear. So its there, just waiting on you to find it.
I'm using my homemade twisted pair of cat 5 now (8 individually insulated
small diameter solid core).
The good news is this is so far down the scale you have nowhere to go but up. Forget impedance. Forget construction. Focus on sound quality.
Hi Elliot, The "rheostat" has nothing to do with the impedance of the speaker. It is just a potentiometer that varies the amount of power going to either the tweeter or midrange horns. 16 Ohm speakers are more efficient. Not much current is required to drive them so heavy gauge speaker wire is not necessary. But, the wire you are using probably has high inductance. You should use 18 gauge wire that is a jacketed twisted pair like this, https://www.parts-express.com/belden-6300ue-18-awg-2c-cable-plenum-rated-in-wall-speaker-wire-100-ft... Always use the 16 ohm tap. If you do not have one the 8 ohm tap will do.
They don't. It does change the sound and in making it more lean and etchy it can seem to be more detailed. Its not.
This isn't how it works.
What's going on is how the amp interfaces with the speaker, how the amp behaves when its driving a higher impedance.
And how the amp behaves is that it will make less distortion, and this will be heard as 'more relaxed more detail'; IOW neither 'lean' or 'etchy'; quite the opposite.
A tube amp will make less distortion (assuming that it has a 16 ohm tap if using an output transformer) and so will have less of the lower ordered harmonics. In this way it will simply sound more neutral. Because there is less distortion, there will be less to mask detail.
A solid state amp tends to not have much of the lower ordered harmonics- their distortion signature tends to be more of the higher ordered variety. But again, they will make less of it, so they will sound sound smoother (since these harmonics are interpreted by the ear has brightness and harshness) and more detailed; the latter simply because there will be less distortion to mask detail.
So we see that in both cases we have the same benefit. Now if its between 4 ohms and 8 ohms, the 8 ohm solution will have lower distortion than the 4 ohm. Again, less distortion (though not as low as with 16 ohms). This BTW is easily seen in the specs of any amplifier. Being that we really are talking about high end audio, where the goal should be to get the music to sound as real as possible, lowering the distortion should be part of that solution :)
As far as the speaker cables go, its a simple fact that at 4 ohms, the DC resistance of the cable can play a role in the damping available to the speaker. The same speaker cable on a 16 ohm speaker is simply going to have a negligible effect on damping.
Now this depends largely on the assumption that the higher impedance speaker is simply higher impedance, and otherwise has the same breakups and other anomalies that it would have if 4 ohms or 8.
If your speaker has level controls or level adjustments, they are there for one reason only- the voltage response of the amplifier is unknown, and the control is there to allow the speaker to be adjusted to that voltage response. This is indicative of the speaker being built for amps that behave as power sources rather than voltage sources (for example, any tube amp that runs zero feedback). For more on this topic see: http://www.atma-sphere.com/en/resources-paradigms-in-amplifier-design.html
And yet, the guy who designs some of the most fantastically successful speakers made anywhere in the world today says nevermind 16 ohms, even 8 ohms is obsolete. https://www.youtube.com/watch?v=tMAO9LPsups
In the video he didn't mention sound QUALITY at all. Nor any comment on AMP performance/distortion differences.
His comments are about the SPEAKER, not the amp. He emphasizes, it's his choice for his high performance, high efficiency SPEAKERS . His demo is about loudness, saying 4 ohm will produce 3db more VOLUME than 8 ohm. IOW, it helps him with efficiency.
Did MC miss the part where the OP has 16 ohm speakers driven by a Cayin tube amp? Of course the sound quality is likely to be best when you are matching the impedance of the speaker to the value of the output transformer tap. The higher ohm tap results in less distortion, increased bandwidth and better efficiency. Apparently MC loves distortion and small bandwidth trying to drive 16 ohm speakers from a 4 ohm tap. Oh and there will likely no bass left at all in the speaker output let alone impact and texture. This actually explains a lot of his advice.
And yes, looking at Eric's video and the premium he places on volume I understand why he leans towards 4 ohm designs.
Lower impedance designs are simply an approach to get more power out of solid state designs....not getting lower distortion. sheesh....
And yet, the guy who designs some of the most fantastically successful speakers made anywhere in the world today says nevermind 16 ohms, even 8 ohms is obsolete.
Nearly all legendary TANNOY speakers are 8 Ohm
Zu Audio speakers are 16 Ohm and they are very popular TODAY
Those 8-16 Ohm speakers are HIGH EFFICIENT SPEAKERS
one time at bandcamp our speaker designer became an amplifier expert...not !
my $ is on Ralph
of course, it’s an unfair advantage when the amplifier is designed for the load and the load is designed to be relatively easy....by the same mindful designer.... Vandersteen M7 or M5, there are of course other designers doing both, MBL, ATC, etc...
i believe there is an exception, keeping the amp in class A by light loading..ala Roger Modjeski
Holy crap! Coulda sworn you were on the list but not yet. Oh well, give it time. Anyways, not being on the list yet allows me to say: That's an insult not an argument. Which is more response than it deserves.
Hello Elliot, I don’t believe that you’ve missed anything. The Eric Alexander video wasn’t particularly compelling but was more about volume differences. Ralph’s explanation to you regarding the advantages of high impedance speaker load was more thorough, reasonable/logical and I feel better supported by listening experiences. Less distortion as well as diminished demands on the driving amplifier (Power/current) seem like unquestionable positive factors.
Ralph concludes that the sound quality becomes more relaxed and with increased detail rather than etched or lean, he is right. Charles
very cool product @tvad I was unaware of it and it would fun to experiment with. I will say, it's nice that my amplifier has 4, 8, and 16 ohm taps and I have spent a lot of time testing various taps along with differing NFB settings.
But why would anyone need this when Einstein above tells us that 4 ohm speakers are always best in every application? The YouTube video of some guy (possibly a wizard?) proving that a louder a noise can be made by presenting a 4 ohm load to an amp compared to an 8 ohm load was like magic. That guy is a genius - he figured out that halving the load impedance will double the power output of an amplifier and make louder noises.
I usually wire mids and highs at 8-16 ohms. I use small planars, or ribbons, both like the higher impedance on valve amps especially.
SS a little different, Pass design puts a smile on my face at just about any impedance.. Not often I wire with a single driver, bass, mids or highs.. Subs, I still wire at 8 -12 ohms. Just less distortion..
The Zero (Speltz) Autoformers are not a free lunch. As with any transformer, they trade off current and voltage. So if you mate an amplifier with a high-ish output Z to a speaker with a low input Z, via the Zero, you lose voltage in direct proportion to the gain in impedance seen by the amplifier. This affects apparent amplifier power. It does work, but it’s not a perfect world. I happily used the Zeros for many years as an interface between my Atma-sphere amplifiers (OTL amplifiers with a high output Z) and my Sound Lab M1 speakers, which had a midrange impedance dip down to 2 ohms and was under 5 ohms impedance across a considerable portion of the midrange. The Zeros made it possible to drive them. Then I traded my M1s for a pair of Sound Lab 845PX speakers. The match was just barely acceptable, because the 845s + Zeros were sucking more amplifier power than the M1s, but with the intellectual input of a guy in Australia and by changing one of the two audio step-up transformers in the SLs and ripping out the crossover components, I was able to completely eliminate the impedance dip typical of SL ESLs. (Ralph knows this story very well.) In fact, my 845PXs now present an impedance that is never lower than 20 ohms from around 200Hz to 5kHz, and they are also much more efficient, for technical reasons too arcane to go into here. The load presented by the Sound Labs is just heaven for my Atma OTLs, and I don’t need autoformers. So, use ’em if you need ’em, but it’s still best to select either a speaker suitable for your amp or vice-versa, in terms of impedance. To the OP. I advise you to set those controls the way you like them, then measure R across each rheostat, then substitute discrete resistors of that value, one for each rheostat (if I am correct that each speaker has 2). This will get you a big upgrade in clarity. When you do that, select very high quality resistors of very high wattage rating; that also pays off.
quite interesting. The Tekton video about using 4 ohm in lieu 8 ohms, 'getting more volume from 4 ohm' plays directly into your distinction between sensitivity and efficiency, which I never understood clearly before, thanks for that. That video also ignores feedback, distortion, current requirements. easy to be misinterpreted. ................................
EV instructions say start at 0 and cut from there. Zero as start, and positive numbers indicating more or even more attenuation (not boost)
My level controls were evidently custom via Fisher: innards: exposed copper wound ceramic; exterior bronze finish recessed cup/handle for flush mount. A centered position, then boost or cut from that.
The level controls are after the electro-voice 16 ohm crossover X336. Electro-voice crossovers were contained in a can filled with tar (smaller x36 shown), mine are 62 years old.
All my speaker's components came from my uncle's Fisher 'President II Console I inherited, using electro-voice drivers and crossover. I have all the components, burned the wood in my fireplace.
Monster magnet, they weigh 37 lbs each. I've re-coned the woofers twice, I just checked, paper/cloth cone/coil kits still available. I have a spare 15W downstairs also.
I replaced the original T35 horn with T350 which is +3db efficiency, useful as we age, nice to have the level control.
These Level Controls give a lot of flexibility, BUT, it takes a lot of work getting both sides properly matched, the various sound positioning options of the McIntosh Mode Switch is the key my success. As frequencies change, i.e. you don't want certain piano notes left, others centered, others right. Imagine a singer's voice wandering. it's a big sigh of relief when you finally get it.
That video also ignores feedback, distortion, current requirements. easy to be misinterpreted.
That was the whole point of the video was to be misinterpreted in order to bias the viewer into preferring a 4 ohm speaker design - always, because it will be louder (all things equal, which of course they are not). Eric does make the completely worthless disclaimer at the beginning of the video that his viewpoint is only through the perspective of a speaker builder and doesn't consider the amplifier whatsoever. Why is this worthless? Because there is always an amplifier and speakers respond to amplifiers differently depending on the amp design.
Can you even imagine a video where an Andrew Jones or Nelson Pass plays photon torpedo noises through 4 ohm and 8 ohm speakers while claiming the one producing the loudest noise is the best - always - categorically....and even to go as far as claim the 8 ohm is obsolete? It's laughable and goes to show the market Eric is largely targeting. This doesn't mean his speakers don't sound decent - it just means his marketing methods can be off-putting because he assumes people are stupid - at least in a video like this.
+1 @atmasphere and @lewm Impedance matters on the load presented to the Amp, as Lew said there is no free lunch, the autorformers yes work if you have the problem but it is best to avoid it.As @charles1dad explained and he is very fond of low power SETs you can benefit ALOT from the 16 ohm Impedance.
Chuck's post as much as I respect and sympathize with his opinions it could be misleading, it depends on which specific experience he might have, IIRC he has Pass amps? My own experience with several tube amps (especially SET) you would want if possible 16 ohms. Atmasphere amps are a special case have MA-1s myself and they can work with 8 / 6 ohms but 12 and 16 ohm are definitely better
For the OP, if you have some small stand mounts Elacs B6 or such, attach these in parallel with your mains and let us know what happens to resolution of the mains, I have done it with both tubes and SS and in both cases lowers resolution and increases distortion
I didn't remember you had Sound labs Lew, wow, that is something I would love to listen to, my speakers made by Duke are very good but he is / was a Sound labs dealer dealer some eons ago and he still praises the sound
1. why/how do 16 ohm speakers make amps sound better, with more resolution?
For an estimated 99+% of amps the higher the load impedance the greater is the amp’s current capacity and the more pleasant and agreeable is distortion spectra. A 16 ohm speaker draws half the current of a 8 ohm speaker.
For SS amps, power/voltage is halved for each doubling of impedance, a potential negative for amps with borderline power. For tubes including OTL it’s all upside (at least up to 16 ohm); in some cases like Ralph’s lovely S30 OTL, power increases 50% (45W, +1.5 dB) @ 16 ohm vs. 30W @ 8 ohm. Interestingly, compared to S30 > 8 ohm, 16 ohm has more powerful bass and IIRC even lower bass cutoff! IIRC, with Ralph’s larger amps the 16 ohm power advantage is less than with S30.
2. why speaker cables less critical?
The sum total amplifier load = speaker impedance + speaker wire series resistance. The higher is speaker impedance the less (as a ratio of 100%) does the speaker wire contribute to the load. You hear less cable and more speaker because the latter contributes a higher ratio of the total load.
Lower speaker cable resistance can have similar effect as increased speaker load impedance; the caveat is that cable inductance rises with conductor thickness, so as usual it’s not a free lunch upgrade,
thanks, we agree about the video and advantages of 16 ohm reduced distortion.
In the beginning, when 4 ohm speakers showed up, some sounded very good, however they were small enclosures, and it seemed to me they needed a heck of a lot of power, the complete opposite of my goals. I didn't know about amount of distortion involved.
I encourage trying tube amps, and the way to save money/size/heat/cost of tube rolling/replacing, is to start with efficient speakers, thus you can stay in the 35/30/25 wpc world of tubes, even less if you use horn speakers or other highly efficient speakers. My friends system uses 8 wpc tube amps.
I remodeled my office recently, my friend has an unused pair of KEF's, I remember them sounding great, I was going to use my Carver Cube 200wpc, enough power for them. However they are 15" deep (to get more box volume, avoiding port(s) I suppose), sadly too deep for bookshelf use.
Thanks for your reinforcement of Ralph and other's comments.
I knew the speakers were very high efficiency (horns), and needed little power (16 ohms is easier, I knew that), but I was unaware of the inherent advantages to the amp regarding lower distortion.
Roger Modjeski always recommended "light loading" his amps and gave numerous reasons why this was beneficial. Some were mentioned by @atmasphere in a previous post. On a pair of 8 ohm speakers I run my RM10 off the 4 ohm tap. The difference is very noticeable versus the 8 ohm tap. Roger often opined why 16 ohms speakers went out of style. Oddly enough in cleaning things up around Roger's shop I ran across a set of Chartwell speakers that are 15 ohms. Going to give them a try on my RM10.
I am not sure that generalization (16 ohms = lower amplifier distortion) would apply to every variety of solid state amplifier. Tube amplifiers as a class tend to have a much higher output impedance than do solid state amplifiers. This does give an advantage for 16 ohm speakers. What I abhor about "4-ohm" speakers is that they tend to be multi-driver arrays with very complex crossover networks. This is a set-up for low input impedance and for power-sucking crossovers. You can get a Pass or other high quality solid state amplifier to drive these beasts because they generally have an output impedance well below 0.5 ohms, and there will be some listeners who like the results. Speaking only for myself, I never have. But it is wise to think about the speaker first, and then to choose an amplifier well suited to driving it. Once that process is done, I have always tended to prefer at least modestly efficient speakers with high input impedance that can be driven by tube amplifiers (my preference has always been for OTLs) or low power Class A solid state amplifiers. Not everyone will agree, and that's fine.
Don't forget to get rid of those "rheostats", which are probably L Pads. L pads sound terrible and one is always better off without them. Replace them with discrete resistors or no resistance at all. See my earlier post.
Indicates: any given gauge: 8 ohm load allows double the length of a 4 ohm load. Presumably 16 ohm load would allow twice the 8 ohm allowable length (4 times allowable 4 ohm length).
I have to believe many if not most are using larger gauge than needed, however, some with 4 ohm speakers that dip to 2 .. some people might not be using a large enough gauge. And people are overly concerned about long speaker cables.
..............................
Text from my MC 2250’s manual:
"Selection of the proper gauge wire to connect the loudspeakers to the amplifier preserves the quality of sound reproduction for which the loudspeakers have been designed. If undersize wire is used, resistance is added to the amplifier/loudspeaker combination which adversely affects the performance. Added resistance causes depreciation of damping characteristics, modification of frequency response and reduction in power to the loudspeaker.
Use lamp cord or wire with similar insulation to connect the speakers to the amplifier. In all cases, the leads to and from the speaker should be twin parallel conductor or twisted pair.
When using 8 ohm speakers and for the normally short distances of under 30 feet between the amplifier and speaker, #18 wire or larger can be used.
For distances over 30 feet a larger diameter wire is required. Select the correct size from the chart below. The DC resistance of the speaker leads should be less than 5% of the speaker impedance. Resistance of the leads must be computed for the length of wire both to and from the speaker or speakers.
Wire lengths above represent the wire resistance equal to 5% of the speaker impedance. For multiple speaker operation, run separate leads from the amplifier to the speakers."
My amp has 4, 8, and 16 taps. If my speakers are 4, what strain, if any, on any of my amp tubes will that have?
If you put the speaker on the 4 ohm tap, none, but the output transformer will likely be losing some performance- they can often lose as much as an octave of bandwidth in the bass, and they will run warmer. That warmth is also causing the amp to make slightly less power, as the heat is coming from the power tube output.
And yet, the guy who designs some of the most fantastically successful
speakers made anywhere in the world today says nevermind 16 ohms, even 8
ohms is obsolete.
As far as solid state is concerned, this may well be true from a marketing perspective. But this is high end audio, where minimizing colorations is important, and distortion causes most of the colorations we hear- for example the brightness/harshness of solid state. The 3dB more power thing is a really weak argument- put another way, if you want to get the **best sound quality**, your amplifier investment dollar is best served by a higher impedance speaker. OTOH, if **sound pressure** is your goal, then you have a 3dB argument for 4 ohms (as opposed to 8) **if** you have a solid state amp that doubles power into 4 ohms. But you really pay a price doing 4 ohms- not only do you have more distortion, but most amps will run warmer (even class D) and the speaker cable becomes critical. On that basis it would be a stretch to claim state of the art performance when the amplifier is thus compromised.
His demo is about loudness, saying 4 ohm will produce 3db more VOLUME than 8 ohm. IOW, it helps him with efficiency.
To be completely correct, it helps with **sensitivity** which is not the same as efficiency. Efficiency is unaffected. What the higher sensitivity number is saying is that the amp is now being asked to make twice as much power! That's completely different from a speaker that is 3dB more efficient- the latter would mean that an amp with half the power would play just as loud!
Like everything electronic, math is involved. Efficiency is stated as a certain sound pressure with 1 watt. Sensitivity is stated as a certain sound pressure with 2.83 volts. Into an 8 ohm load 2.83 volts is 1 watt; into 4 ohms its 2 watts. This is a 3dB difference. Since tube amps don't double power as impedance is halved, efficiency is the more useful specification, but since the industry went solid state, the sensitivity spec has taken over. You can make any speaker seem more "efficient" by reducing its impedance though parallel drivers but what is happening is the sensitivity is being increased while the efficiency is unaffected. You do have to pay attention to this nuance when selecting a speaker to work with an amplifier!
1. how importance is bias to sound? (I don't care about heat or tube life).
I
don't really understand inductance. If speakers are high efficiency
(mine are), and I/you have more than enough power from the amp, speaker
3. equiv 15 awg, is inductance an issue?
Inductance (Back EMF) might increase amount of current needed, but
4. enough power: does it have any effect on the music's frequencies?
Bias can be pretty important. Usually it is used to place the output device (tube or transistor) in the most linear portion of its operating curve. So it can have a noticeable and measurable effect on the sound.
The inductance of the speaker cable plays a role, but so does capacitance and DC resistance. I would not place too much importance on any one characteristic. In theory, the cable has what is called 'Characteristic Impedance' which is the character where the cable is properly terminated by the impedance specified. Put another way, if the cable has a characteristic impedance of 8 ohms, if an 8 ohm load terminated the cable, there will be no reflections from the load back to the source. In this case from the speaker back to the amplifier. But in practice, no speaker is a perfect resistive load, and the back emf from the speaker dominates the minor reflections, so what becomes more important is that the speaker cable simply be kept as short as possible so that its errors are minimized. This FWIW is why I developed a balanced line preamp, so the amps could be placed as close to the speaker as practical. When doing this you hear an immediate improvement in bass impact and resolution. In a nutshell- keep your speaker cables short and used cable with plenty of conductor to do the job.
The amount of power you have might affect how much bandwidth the amplifier has. This is particularly true of SET amplifiers, where power past about 7-8 watts falls short of the definition of 'hifi' (the smaller the SET, generally the wider bandwidth it is; this is why the type 45 power tube, which is only good for 0.75 watt, is the 'best' sounding). With push-pull tube amps this limit is more like 60-120 watts, but in both of these examples its assumed that there is an output transformer on the tube amp (some tube amps don't have output transformers so are not bandwidth limited at any power level). Some solid state designs don't scale well as power is increased, but most of those I've encountered are older designs employing coupling capacitors at the output of the amp.
Dear friends: I respect all gentlemans opinions but this is what defines the amplifier need it. Not what said atmasphere or Dudley or Fremer or Teektonany one else because one is the manufacturer theoretical impedance ( been 4ohms or 16 ohms. ) at the end it does not matters till we know what these facts shows us:
I am not sure that generalization (16 ohms = lower amplifier distortion) would apply to every variety of solid state amplifier.
@lewm If you know of one that actually has lower distortion into 4 ohms as opposed to higher impedances I'd love to know about it. I've yet to find one, starting from primitive driver transformer designs of the 1960s to self oscillating class D amps of the 2020s. If there is one out there it is a very rare exception!
level controls are in the neutral position now, i.e. doing nothing.
I have been thinking of simply bypassing the level controls, on one speaker first, see how it compares with the other, any detectable changes. Then mess about with level controls other speaker, see if any 'improvement' can be found.
No problem or better without the controls, then bypass the other.
This didn’t start about sound, I am completely content with everything as is.
It was about bias controls, internal or external.
I was considering changing to a newer version of this Cayin A88T tube amp to get external bias adjustment, which my current version lacks. Those newer versions have dropped the 16 ohm taps.
Now that I have learned about the relationship of resistance to distortion, I’m sticking with this version, 16 ohm speakers to 16 ohm taps. Sticking with the internal bias controls.
Steve at VAS previously said he would adjust the bias while I waited.
Elliott, Lewm is correct in that you have to measure the resistance of the L pads when they are in neutral position. It may not be zero. I think it is best to do what Lewm suggested. Set them up so that they sound good to you. Then measured the resistance and substitute the appropriate resistors. Wires that run parallel to each other have the highest inductance. In other words one wire will induce a current in the next wire. Wires across each other at 90 degrees have the lowest induction. I believe the wire in cat 5 cables is parallel. Wires in a twisted pair are always approximating 90 degrees to each other and therefore have very low induction. IMHO the best wire made for loudspeakers is Kimber Kable. It uses smaller gauge wire woven in a pattern that keeps induction very low and because the wires are very close to each other parallel resistance is low. As Ralph relates you keep series resistance low by keeping the wires as short as possible. For 16 ohm speakers 18 gauge twisted pair is more than adequate. If you want to go ballistic buy a set of the higher gauge Kimber Kables. My amps are right under the speakers and I use 3 foot runs of Kimber Kable 12TC. Lewm, I finally ordered my Sound Labs!! They are a custom size, basically 845s the width of 645's, a little narrower. They will fit my situation better. Roger is supposed to be giving me an ETA today or tomorrow. You mentioned that you modified the interfaces. Did you just bypass the controls?
@elliotnewcombjr The level controls are there to allow you to adjust the speaker to your amplifier's voltage response. But to maintain the crossover point they should be the same value as the original.
@mijostyn If you're getting a new Sound Lab, Roger corrected for the issue to whicht @lewm was referring. So you shouldn't need to do any mods.
Dear @lewm : I can't understand why you and any one else speak of 16 ohm, 8 ohm or 4 ohm speakers when the speaker impedance is not flat , it changes over its frequency range.
The measurements made it by Stereophiles confirm it and it does not matters what the speaker manufacturer specs are.
We can't choose an amplifier ( tube or SS. ) founded by the manufacturer nominal impedance spec because this spec is away from reality and all those "" bla, bla, bla " in good shape opinions on lower or higher distortions and the like has no true value. Facts are the only reality.
Any kind of audio items measurements made it by Stereophile always are really enligthing and learning lessons for many of us, at least for me that I'm not an expert as other gentlemaNS HERE.
The OP ask something on 16 ohm speakers when does not exist in the way he was and is thinking.
If we look these measurements of 3 way different amplifiers along the speakers measurements posted we can understand the whole subject in a better way:
I can't understand why you and any one else speak of 16 ohm, 8 ohm or 4
ohm speakers when the speaker impedance is not flat , it changes over
its frequency range.
Simply put, a nominally 16 ohm rated speaker will be higher impedance than a nominally rated 4 ohm speaker.
It is true that no speaker has flat impedance, but the impedance variation is not so important as the overall. If the impedance is overall higher, the amp will be lower distortion. I suspect that this is one of the reasons the Sound Lab is so transparent, as in the bass region its 30 ohms. Any bass energy made by any amplifier will have less harmonic distortion simply because the amp will be lower distortion where the power is needed most. And for all that, the impedance of the speaker varies by about 9:1 from bass to 20KHz.
Dear Raul, Of course you are correct that no speaker has a flat impedance. Yet it's common practice to refer to speaker impedance with a single value. I am guilty of that as is almost everyone else in the audio world. If it were of some importance to me personally in the course of evaluating a speaker for purchase, I would demand to see the full impedance curve over the entire frequency range. As you know, an impedance dip in the bass or midrange can be much more consequential than a falling impedance at very high frequencies, for the interaction of any speaker with any amplifier. I don't argue with any of the points you made about speaker impedance. Also, all remarks about speaker impedance are subject to the choice of amplifier to drive that speaker, unless the speaker is just crazily variable in impedance across the audio frequency range, which will be challenging for any amplifier.
Ralph, The older Sound Labs sounded anything but "transparent" in the midrange, using your OTLs to drive the unmodified version of my 845PX. I remember listening to Frank Sinatra during the first week or two after I bought the 845PXs and thinking to myself, "Is that Frank Sinatra?" Yes, Dr West did respond to our findings and our fix by revising his circuit and substituting the old treble audio step-up transformer for a new one that works down to lower frequencies, at least an octave lower. This allowed him to make changes in the crossover such that it sucks less power and provides for a higher impedance at midrange frequencies. I am told it's a big improvement. I continue to drive my own 845PXs using a treble transformer capable of full-range response that does not require any crossover components at all to differentiate the input to the bass vs treble transformers. Now, getting back to the amplifier factor, it is quite likely that the old version of the 845PX could have been driven more satisfactorily at midrange frequencies using a typical SS amplifier, because of the lower output impedance exhibited by most SS designs, but then I wouldn't have the OTL-ness to which I am addicted. I was told that SL use SS amplifiers at their factory, which is probably why the problem went unnoticed for a while.
Now, getting back to the amplifier factor, it is quite likely that the
old version of the 845PX could have been driven more satisfactorily at
midrange frequencies using a typical SS amplifier, because of the lower
output impedance exhibited by most SS designs, but then I wouldn't have
the OTL-ness to which I am addicted. I was told that SL use SS
amplifiers at their factory, which is probably why the problem went
unnoticed for a while.
@lewm I have customers with solid state amps and they report the same thing that our customers with tube amps do- that when the error in the backplate was corrected, the speakers instantly were easier to drive and sounding better at the same time.
Sound Lab was using a Boulder amplifier, which is why they may not have noticed a problem. But remember that resistor that got pulled out? It was a composite of eight resistors, totaling 200 watts! Obviously a lot of amplifier power was being used to heat those parts up. So its no wonder when that problem was corrected that the speaker got instantly better.
Dear @atmasphere@lewm and friends: In reality " things " are not so " simple " as both of you posted to me.
The whole speaker impedance subject is a lot more than only the deviations through the frequency response of the speakers because we have to take in count to phase and angle that could " helps " to the amplifiers to develops even higher distortions and if you look to the amplifiers measurements I linked you can see that how good or not an amplifier can drive an specific speaker model.
If can be true that some SS amplifier can have some " problem " with some specific speakers ( I never found out one SS amplifier that had problems about or at least I just coul not detect it and I'm extremely demanding listener, not an easy one. ) where exist a higher trouble is with tubes even that the system owners are satisfied with and likes what they listen with.
Problem is that speaker manufacturers never gives the whole impedance facts/measurements/charts. Tha's why generalizations to say 8 ohm speaker spec means almost nothing. I choosed at random ( between hundred of ST measurement. ) and you can read there that your words are not exactly rigth with some of those speakers, same for maplifiers.
I love Soundlab speakers and for me is the only today electrostatic that I really like it. My friend Guillermo ( a wealthy one gentleman. ) owned big Wilson that performed very good. Suddenly he took a fligth tp SLC in Utha and he bougth and brougth with him a pair of top of the line Soundlabs and the JC-1 amplifiers recomended by the designer him self. For me was a surprise because never told me he wanted to change the Wilson, so and before I listen his new system and when both been at my place testing one of the tonearm prototype he told me about and I asked why and he told me that were the only speakers with the kind of sound quality performance levels that the very old ones in my room/system. For me was a true unexpected nice comment by him but when I listened at his place I really fall in love with Soundlabs/JC1 combination and if not exactly it sounds similar, obviously I like it.
This Soundlab measurements are not the today ones but more or less gaves an idea about and confirm that in the bass range what you said of very high impedance that for a SS amplifier is not " welcomed " however I heared no single trouble in those Soundlabs driving by the truly good JC-1 monoblocks:
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