Hi,

I compared my 1974 pair of ESL57s against a pair of newish TDL speakers
using a test CD with stepped tones and measured the output with a sound
level meter. The high-frequency roll-off of the ESL57s was very noticable.
The higher tones (10kHz up) were there but the volume dropped off rapidly. I
was using a late (mid-eighties) Quad 34/303 combination for the test.

What is the most likely cause of this? Is it most likely to be the treble
panels or could there be a loss of voltage to the panels. I believe they
were overhauled by Quad around 1995 but that was before I owned them so I
don't know what was done.

The panels certainly hold a charge well. I switch off the mains to them
while I swapped connections about and when I reconnected them 20-30 minutes
later they still worked for a short time even though I had forgotten to
switch the mains back on.

Regards,

John.

"John Smith"

I compared my 1974 pair of ESL57s against a pair of newish TDL speakers
using a test CD with stepped tones and measured the output with a sound
level meter.


** Stepped tones are quite unsuitable for "in room" speaker testing.

Get yourself a CD with pink noise tracks divided into 1/3 octave bands -
like the "Denon Audio Technical CD, 38C39 7147 " It is not an expensive
one.


The high-frequency roll-off of the ESL57s was very noticable.
The higher tones (10kHz up) were there but the volume dropped off rapidly.


** Did you have the mic pointed at and directly on the central axis of the
ESL57 ?

What SPL meter did you use - not the cheap Radio-Shack one I hope ?

Did you set the meter to C weighting ?


What is the most likely cause of this?


** Your test procedure and gear.


BTW

I have been doing just such tests, with pink noise, on a pair of ESL63s
this week.




........ Phil

[Phil Allison]

"Phil Allison"

" I have been doing just such tests, with pink noise, on a pair of ESL63s
this week."


** Further to the above - this is basically how I carry out response and
sensitivity ( dB /w/m) tests to Quad ESLs ( and others) in a domestic
environment.

Tools:

1. The "Denon Audio Technical CD, 38C39 7147 " with octave & 1/3 oct pink
noise bands.

2. A CD player, Sony CDP101 in my case.

3. A power amplifier with known flat response ( +0 ,-1 dB 10Hz to 50 kHz)
and low output impedance.

4. A "true rms" AC voltmeter with response flat from 5 Hz to 100 kHz +/-
1% of reading - this is an ESSENTIAL item.

5. A Rode SPL meter with 1/2 inch true condenser mic capsule & modified
electronics to give *flat* response rather than C weighted - which is
nearly 10 dB down at 20 kHz (http://en.wikipedia.org/wiki/A-weighting).

6. A camera tripod for the Rode meter.


Procedu

Position Quad ESL (or box speaker ) on a stand so the central (or tweeter)
axis is 1.5 metres above the floor - all speakers are kept well away from
adjacent walls.

Position SPL meter *exactly* on axis and 1.5 metres in front of the ESLs or
1 metre for box speakers.

Connect AC meter to speaker terminals to monitor the input level in volts
rms.

Play octave band noise centred on 500Hz and adjust signal level to get a
reference reading of around 80 dB SPL.

Play each octave band in turn and note readings on BOTH the AC meter and the
SPL meter - any drop in the AC meter reading is used to correct the SPL
meter reading.

Do same as above for 1/3 octaves and plot on a graph.

Sensitivity can be tested with full audio band pink noise or preferably by
averaging the SPL readings in the octaves from 100 Hz to 8 kHz - in each
case the level is adjusted to show 2.82 volts rms on the AC meter
corresponding to nominal 1 watt / 8 ohms.

For Quad ESLs, the SPL meter is moved to a position exactly 2 metre away,
6 dB is then added to the reading to give an SPL figure referenced to the
usual 1 metre distance.





........ Phil