McIntosh XR27 - Manual (Page 4)

4
McIntosh Acoustic Engineers have refined the Loud-
speaker System concept to provide superior sound quality
in a versatile enclosure with five different installation
methods.
The Low Frequency Section of the System consists of
four 8 inch Woofers. They have a large magnet assembly
and long cone excursions with very low levels of harmonic
distortion and frequency response down to 80Hz. Refer to
figure 1. The Woofer also incorporates McIntosh’s Pat-
ented LD/HP 1 Magnetic Circuit Design with shielding to
greatly reduce any external magnetic field. Extensive in-
vestigating and testing re-
sulted in a new design con-
cept which utilizes a pair of
aluminum shorting sleeves
in the magnetic circuit. Re-
fer to figure 2. The sleeves
virtually eliminate the nega-
tive influence of the fluctu-
ating voice coil field on the
permanent magnet field.
This results in lower distor-
tion due to more linear magnetic flux in the voice coil gap.
Refer to figure 3. Additional benefits are less volume com-
pression due to
improved heat
transfer through
the sleeves and a
cooler operating
voice coil. Both
measurements, as
well as critical
listening, reveal
ten times less dis-
tortion than previ-
ous designs.
Introduction
Figure 3
Figure 2
LD/HP
Conventional
1 LD/HP Pat. No. 5,151,943
Figure 5
Figure 1
Figure 4
The 6-1/2 inch Midrange Driver also incorporates
McIntosh’s Patented LD/HP 1 Magnetic Circuit Design with
shielding to greatly reduce any external magnetic field.
Refer to figures 1, 2 and 3. The low distortion of this
Midrange Driver results in the incredible smoothness and
clarity in the reproduction of the human voice. The five 1
inch soft dome Tweeters are inline and connected to pro-
duce a Bessel Function Array. Refer to figure 4. The indi-
vidual tweeter amplitudes and phase relationships are ad-
justed so the array acts as a high frequency point source.
One advantage of such an arrangement is a very smooth
and even acoustic polar response. This allows the listener
to move off axis without suffering a change in high fre-
quency output. The use of multiple tweeters, combined
with a heat sink, also provides greatly increased power
handling at high frequencies.
The Crossover Networks used in the XR27 Loud-
speaker System are designed to ensure an even frequency
response over the entire audible range. The Low Fre-
quency Crossover Network is a Third Order design utiliz-
ing Capacitors and Inductors with high current capacity.
Refer to figure 5. Low Loss (DCR) Inductors in the Low
Frequency Network, are chosen not to exhibit any core
saturation even at high power levels. This prevents the ad-