Enhancing the Martin Logan ReQuest
Electrostatic Loudspeakers
Martin Logan is
renowned for it’s curve linear loudspeakers which are designed for exceptional
sound reproduction. The production is fine and no costs are spared to optimize
the construction and finish. The trademark of Martin Logan is the curved
electrostatic panel which aims at dispersion of the radiated sound, which by
physics will be focused and thereby will limit the listening position. But all
efforts will go to a point, after which additional efforts will not be
economically valid. This is where the individual user can try and push the
envelope even further, with additional costs and material which can hardly be
part of the original package.
The Quest is
one of the bigger speakers in the nineties making the name and fame of Martin
Logan. This speaker was and still is well favored by many music lovers all over
the world. The ReQuest is a newer enhanced version extending the lifespan of
the speaker well into the new millennium. Basically the Quest and the ReQuest
share the same construction. These speakers are (as often at Martin Logan) set
up as a hybrid with one large bass unit in an enclosure that also contains the
crossover filter. This filter is one of the places to find possible
improvements. The choice of filter component makes can be wide and is subject
to personal taste.
A second place
to look for possible enhancements is the enclosure. The bass cabinet and
reasonably sturdy frame for the ELS are integrated into one speaker so possibly
the mechanical energy from the bass sounds can interfere with the sounds
radiated from the electrostatic panel. As an electrostatic requires relatively
low excursions to radiate sounds (compared with cone speakers and tweeters)
these interferences are of a greater influence than in conventional box
speakers. At least, this is my assertion and I’ve found tremendous improvements
possible when ironing out mechanical vibrations in ELS frames so I stand by
this assertion.
The crossover filter
In the very nice Martin
Logan website http://www.martinloganowners.com one owner has written an article on the
change made in the crossover. His idea was that the simplest and most cost
effective upgrade is a ‘straight forward’ capacitor upgrade on the high-pass
(stat) circuit. I’ve carefully read his article and decided to replicate his
idea. But I did choose a different brand of audiophile grade capacitors.
Opposed to his Auricaps I’ve chosen LeClanche for a well informed personal
friend advised these to me. The original caps in my ReQuests were Elpac’s as
opposed to the Solen versions mentioned by the original writer. The three
capacitors values to replace are; 5uF , 10uF and 15uF, all 100 volt types. As
the 5 uF version proved unavailable in the LeClanche ranges, a combination of
two caps was used to get the required value. The procedure to change the old
caps with the new ones is simple. Keep in mind that all electrostatic speakers
use a high bias voltage supply to the stators, so you have very high voltages
going on inside there; so be very careful. I unplugged the speakers for
a holiday and afterwards made the mod. After 10 days of rest all voltages were
gone. As this procedure is very aptly described in the Martin Logan website I
will restrict my story to the photo’s. As much as possible I avoided the
original supplemental connecting strips and connected the components directly
to one another.
The speaker enclosure
As said earlier I am a firm believer of
a vibration free base for the middle and upper frequency regions. This is why I
still own and love the rare Roksan Darius conventional loudspeakers in which’s
two-way lay-out the tweeter is decoupled from the enclosure by springs. And
remarkably is the result. I’ve enjoyed larger than life electrostatic panels
(Audiostatic’s of 220 * 70 cm) which were deadened by 80 lbs of lead to
stabilize the panels. These experiences have inflated my believe in dead and
stable speakers.
It was no
surprise to me to read an other report in the infamous Martin Logan website
claiming significant improvements when putting heavy steel sheets on top of the
bass enclosure. When reading his story I immediately related this to my own
putting of 16 lbs of steel on top of the base cabinet. I’ve done so to put in re-use
the flux dumpers of my previous large Audiostatics. These flux dumpers were
tailor made for these Audiostatics and were placed directly on top of the large
audio transformers of these humongous panels. But when the Martin Logan’s were
reeled into my music system the flux dumpers were put at the back and on top of
the bass enclosure as this is the closest position to the audio transformer as
I could get.
Magnetic flux dumping
When reading
the comments in the Martin Logan website article I realized I could have heard
an improvement because of the stabilizing mass in stead of or in addition to
the original idea of transformer flux dumping. Also the previous experienced
benefits of stone mass put on top of almost all box type speakers sprung into
my mind. Most likely there is a profit to be gained from fixating the
loudspeakers construction. Building a electrostatic panel into a stone wall
seems to prove this point in an extreme example. The same effects can be gained
from weights to try and fixate the electrostatic panels into the room as well.
This idea was put into my mind by the Martin Logan website article. On top of
the bass cabinet a large steel sheet can be placed without any problem so I
tailored some additional steel weights for the Martin Logan’s.
Additional weight
As this only stabilizes the bottom part of the
ELS panels I additionally came up with the idea of putting the original weights
on top of the speaker frames. The weight on top reduces the movements on the
top end of the enclosure and might be of even more importance. Listening tests
resulted in very positive impressions for me and my listening friends, so a few
curved steel sheets were prepared to put additional weight on top of the panels
as well, possibly giving the best improvements overall.
When I was at
the topic of minimizing resonant behavior of
the enclosure I also paid attention to the back panels of the Martin
Logan’s as these seem to be most coloring of the enclosures. Adding an inch
thick additional panel forces most resonances out of the way of music, and is
shown in the pictures as well.