an image to enlarge.
...After suffering various documented panel
failures to my MartinLogan Scenario ESL speakers, it is only natural
to keep a suspicious finger pointed directly at these very sensitive
speakers. Instead of enjoying my record collection, I have spent
many months swapping various components, interconnects, mains
cables and even going all the way back to the electricity consumer
unit to test the dedicated hi-fi circuit breaker, desperately
trying to isolate the cause of sound degradation.
I can now confirm that issues such as distortion,
smearing, loss of dynamics have been caused by multiple failures
in the component chain. To make matters worse in respect of identifying
and isolating the issues, these multiple component failures were
slow to reveal themselves due to their intermittent nature. The
above issues have been caused by speaker panel failures at various
points (but now resolved with panel replacements) as well as a
slow and intermittent amplifier issues.
My Musical Fidelity M8 500s amplifier
was shipped to Henley Audio (Musical Fidelity UK Distributor)
via Audio Venue dealership Ealing in June 2020 for a final fault
diagnosis and fix…
Henley Audio Test Process
We tested the M8 500s on a test bench and also extensively on
soak test with different speakers. In both environments it performed
within specification and delivered the expected sound quality.
We also carried out an internal check and found all componentry
to still be operational and generally surmised that the overall
condition and performance of the amplifier was very good. Considering
the major drawback of our testing was that we have no access to
electrostatic loudspeakers, we then theorised over your experience
and established the following feedback...
Presumed Issue with ESLs
Generally speaking, Musical Fidelity power amplifiers over 350W
will typically be bridged, which effectively means each speaker
has two amplifiers in its drive-path. Although the output impedance
of our amplifiers is very low (< 0.02?), this configuration
will effectively double the output impedance of the power amplifier
as a whole. This could affect higher current outputs under very
It's appropriate to say at this time that Musical Fidelity have
not had any problems with this configuration when using even the
most "difficult" dynamic speaker systems, according
to their own experience and the feedback they receive from many
of their global distributors and retailers. But, equally, they
have also not received any reports from customers with the same
type of system configuration as you (i.e. Martin Logan and high-power
It's the opinion of Musical Fidelity that any very reactive speaker
needs good current drive capability to drive it, rather than the
brute force of volts. In theory this is basically true for both
electrostatic and dynamic speakers, but it's appropriate to highlight
that ESLs will also have a larger than normal inductance on the
driver transformer in the speaker and a relatively huge reflected
capacitance in the panel itself. That makes this logic certainly
more relevant for ESLs.
So, Musical Fidelity would summarise that their high power bridged
amplifiers are not the optimal choice for ESLs, or any other lower-impedance
(or "dippy impedance") speakers (typically < 2?),
as they would typically "waste" the power they're generating
on excess heat rather than the current you need. The company would
instead recommend a lower powered amplifier with higher current
capability, such as the M6s PRX. That explains why Michael Valentine
Studio found no performance issues when they tested the M6 PRX.
Amplifiers like this model will give the lowest possible output
impedance, and therefore the best panel control with an ESL.
We at Henley understand the frustration of your journey to this
point and regret you were not able to get this feedback in the
past, but we strongly hope this gives some clarity to your situation.
The amplifier is boxed and can be sent back to you with no service
Michael Valentine Studio
…You have done all you can do, however,
this still leaves me with an amplifier that does not work with
my system. The only strange entity is the time it has taken to
reveal such flaws (or weaknesses) for want of a better term. The
system sounded great for quite a while and was seen by many as
‘the level of transparency to aim for’. We
will need to have discussions with Audio Venue at some point to
see how we move forward. I cannot think of anything else right
Response from Henley Audio
… I understand your comments about why
the issue seemed to develop, rather than appear from new. I don't
know if length of time or exposure has “stressed”
either the amplifier or the speakers at all. We have seen that
with valve amplifiers, where they sound lovely through a set of
speakers, but actually those speakers are too heavy a load and
eventually the amplifier just can’t stand it anymore. But
I cannot say if such a thing has happened here.
All I can say is this amplifier seems ok in every way, and
we have a technical reason for the issue you're experiencing.
the very best with what comes next, and if you ever need anything
else from me don't hesitate to ask.
The discussion continues
The discussion regarding how we are going to move forward continues,
however, at this point it is important to acknowledge the cooperation
of Henley audio’s Operations Director Simon Powell for his
assistance to date. We have come a long way in the last month,
especially when we consider the painful journey over the last
Update 13 August 2020
After much discussion and further investigation We began the
process of testing The Musical Fidelity Nuvista 800 integrated
amplifier & Musical Fidelity M8s 700m Monobloc (x2) in our
© Michael Valentine Studio
July - August 2020
Use the links below to read the Musical Fidelity M8s 700m monobloc
power amplifier Experience Review 1,
or the Musical Fidleity Nu-Vista 800, 2020 Experience Review,
or the Musical Fidelity M6 PRX power amplifer Experience Review,
or MartinLogan Scenario Owner Experience 2,
or MartinLogan Scenario Owner Experience 1,
or The System Upgrade 2015...