16 ohm speakers: any amp sounds better with more resolution. speaker cables less critical.

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:

https://www.stereophile.com/content/sound-lab-1-electrostatic-loudspeaker-measurements


R.

For those who don't know, Sound Lab drive their full range ESLs using two audio step-up transformers wired in parallel, one for bass and one for treble.  Audio frequencies are divided by a first order crossover network (inductor in series with the bass transformer, RC network before the treble transformer) before being fed to the bass and treble transformers, respectively.  I have done impedance vs frequency curves for my 845PXs, measuring Z at 50, 100, 200, 500, 1K, 2K, 5K, and 10K Hz, with the original bass and treble transformers in place, with only the OEM SL bass transformer in place, with only the original treble transformer in place, and with the aftermarket full-range 1:90 ESL transformer alone and in combo with the OEM SL bass transformer.  I have the data in a notebook.  So I think I have a pretty good understanding of the impedance of an 845PX.   I use the speaker with the OEM bass transformer preceded by a small inductance, in parallel with my aftermarket audio step up transformer preceded by no filter at all.  Efficiency is hugely improved; I would wager it could easily be driven by less than a 50W amplifier.  My Atma-sphere amplifiers probably make 100W into a 16-ohm load, and they are coasting at high SPLs while driving the 845PXs, which appear in my system as about a 20-ohm load, using the generalization that Raul dislikes, but I can guarantee that Z never goes below 20 ohms below 5kHz. All ESLs are in effect giant capacitors, so it is inevitable that Z goes down as frequency goes up above 5kHz. As Ralph said, the big problem was the resistor in the RC network that was there to create a high pass filter for the (old) treble transformer.  That resistor, depending upon the vintage of the speaker, could be as low as 5 ohms, or in later speakers as high as 8 or 10 ohms.  The resistor creates an absolute upper limit of impedance at frequencies around the crossover point, because it is in parallel with the output of the amplifier.  Thus, if you were unlucky enough to have one of the older speakers with a 5 ohm resistor, you were dealing with 5 ohms or less impedance at around 500Hz to 2kHz.  That's also why you benefited from a very high wattage resistor in that RC network.  Raul has a point about the very high impedance in the bass region using the OEM bass transformer; it's way up around 100 ohms and maybe higher below 100Hz.  Yet, my OTLs drive it fine, as does Raul's friend's SS amplifier.

Elliot, For Sound Lab owners, the first thing I recommend is to bypass the "Brilliance" control, which is an L-pad in series with the treble transformer, much like the controls on your speaker.  Alternatively, if you feel you need some treble taming, you could use a discrete resistor of an effective value in place of the L-pad.  L-pad bad.  No L-pad good.

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.

Whenever anyone asks if a speaker will work with our amps I take a look at the impedance curve if one is available. But if the speaker is rated 8 ohms or more I pay attention, and if the speaker is rated higher, like 16 ohms, I’ve yet to run into one that didn’t work. I’ve seen some speakers, like B&Ws, that are rated ’nominally 8 ohms’ but feature dual woofers, which are wired in parallel, although the midrange and tweeter array is certainly what I would call ’8 ohms’. The woofer array, even though it may have peaks at 8 ohms or higher, is something I would regard as more of a 4 ohm load. So you do have to be careful about this issue; but in the case of higher impedances it usually no worried at all.


The Sound Lab is not a speaker rated at 16 ohms or 30 ohms despite both impedances being present at some frequency. While it is difficult for most solid state amps to make power on this speaker owing to the 30 ohm impedance in the bass (which is why a tube amp of 150 watts can easily keep up with a solid state amp of 600 watts on this speaker), all this means is that you might see about 1/4 the power the amp is rated for into 8 ohms. However, and this is important, as the frequency goes up above about 5-7KHz, the impedance is dropping, to a low of about 1.5-3 ohms (depending on the setting of the Brilliance control) at 20KHz. Like almost any full range ESL, the impedance varies by about 10 or 9:1 from the bass to the highs. The issue here is that a good quality solid state amp will double power as impedance is halved. With a box speaker, this is fine because a peak in the impedance curve usually represents a resonance so this property is welcomed. But this isn’t the case with the Sound Lab. It needs about the same power in the bass region as it does in the high treble region to make the same sound pressure at that frequency. This means that an amp that can double power (and the Sound Lab does not challenge most solid state amps in that regard) will be excessively bright due to this property.

To get around that issue, the Sound Lab is equipped with a number of settings to modify the speaker’s response. The Brilliance control is there to deal with excessive brightness, the bass settings allow you to boost or cut the bass, depending on if you have a solid state amp (boost) or tube amp (cut). IIRC there are midrange settings too.


One nice thing about this speaker if using solid state is that the bass impedance (where the power is) is high, resulting in low distortion for nearly any amplifier. Low distortion means less harmonics from the bass notes, so an amusical harmonic like the 7th, 9th, 11th or 13th to which the ear is keenly sensitive, will be greatly attenuated. IME this is beneficial to all amps.


The mod that @lewm did seems a wonderful upgrade for the speaker!

I’m gonna

1. remove the L pads
 
another advantage: the L pads in the back panel won’t be wired to the crossover/drivers inside, the back will come fully off.

2. annual tightness check (nothing ever loose, but, to sleep better ..)

a. confirm the drivers are tight to the front panel, and
b. the front panel tight to the case 
c. 15" Woofer off the front panel, I can check the paper cone’s condition, it’s been several years.
d. I might drill more mounting holes on the metal ring of the 15" woofer, 4 just doesn’t seem enough for that 37 lb monster (although it is never loose when I check)

3. make a new set of speaker cables using this:

https://www.ebay.com/itm/75FT-CAT7-S-FTP-Network-Outdoor-High-Speed-10Gbps-Shielding-Ethernet-Cable-...

OFC, S/FTP, 24 awg solid strands (8 conductors equivalent to 14 awg)
(might be 26 awg, equivalent to 17 awg, waiting for seller's answer)
12 feet long each, (2+, 2- : 50 foot roll will just do it) 16 ohm nominal.
McIntosh chart says 18 awg, 16 ohms, max 60 feet long.

Unless someone talks me out of it!!!

If you want to add a single resistor to replace the L pad and adjust brilliance (like Lew suggested) Mills are great, those are the ones I use on my speaker and are very transparent, 12W BTW 28 ohms in my case.
Edit: in your case of course you might want to measure the lpad setting for resistance and replace with same value, my 28 ohms is very specific to my room and driver