ed on the XdA amplifier’s front panel. Turning off the amplifier and turning it on again fixed the prob- lem.)

Repeating this torture test with the 150Hz crossover filters didn’t result in any shutdowns with the Clarke solo, and the chord that begins “In the Flesh,” from Pink Floyd’s Is There Anybody Out There? (The Wall Live) (CD, Columbia C2K 62058), sounded positively cata- clysmic. The low-frequency crash of the wall being demolished on this album gave the XdW subwoofers one heck of a workout. However, the drum-and-unvoiced-guitar intro of Eric Johnson’s “East Wes,” from his live Austin City Limits CD, still managed to shut down the left XdS woofer amplifier if I wasn’t careful with the volume control. (Setting the NHT PVC’s control to –6dB, equivalent to an in-room SPL of around 108dB, could trigger an amplifier shutdown with this track.)

I listened again to the half- step–spaced tonebursts on Editor’s Choice. Despite the revised filters, I could still hear the slight modulation noise accompanying the tonebursts. Probably not too much should be made of this phenome- non; I mention it only because I had never heard it before with conventional loudspeakers.

What about the high frequen- cies? The veiling that had bothered me was much reduced, the top octaves having more air apparent. Perhaps more significant was the minimizing of a slight mid-treble “shoutiness” that had limited maximum volume with the original fil- ters. The presentation was first-rate in its lack of coloration, superbly stable and detailed imaging, excellent retrieval of subtle reverberation tails, and overall top-to-bottom integration. Wow!

Measurements: Fig.1 shows the response of the Xd satellite (black trace) and the XdW subwoofer (green), as well as the individual responses of the Xd tweeter (red) and woofer (blue), with the XdA crossover running the original digital filters. The crossover points lie at 110Hz and 2.3kHz, and the Linkwitz-Riley filter slopes are a very steep 48dB/octave. A touch of excess energy can be seen in the mid-treble, and the top octave is a

F O L L O W- U P

 

 

 

 

 

 

little shelved off both on axis (red)

treble. There is also now slightly

and in the 30° averaged response

more energy

apparent

between

(black). It also looks as if the tweet-

7kHz and 15kHz, and the tweeter’s

er’s ultrasonic dome resonance has

ultrasonic resonance is unfettered by

been notched out.

a notch. The response on-axis (red

 

By contrast, fig.2 shows a similar

trace) now extends flat to the tweet-

set of response curves taken with the

er’s resonance at 27kHz, though the

revised filters (NHT’s “150Hzcross-

HF unit’s limited dispersion above

over.flt” file). (Because of continued

15kHz results in less energy in this

wind and torrential rain during

region in the 30°-averaged curve

October, the responses above 300Hz

(black).

 

 

 

 

were taken indoors at 40" instead of

But it is the response in the room

outdoors at 50"; this affects the accu-

that matters most. To investigate

racy of the measurements in the

how the Xd system behaved in my

midrange but is otherwise inconse-

listening room, I ran my usual test of

quential.) The filter slopes are still

averaging 120 1⁄3-octave power spec-

48dB/octave, and the crossover

tra taken individually for the left and

between the XdW subwoofer and

right speakers in a window centered

the XdS satellite can be seen to have

on the position of my ears. The blue

been shifted up to 150Hz, as speci-

trace in fig.3 shows the in-room

fied. While the upper crossover

response of the Xd system with dual

point looks very similar to that in

subwoofers and the XdA’s original

fig.1, the XdS drivers look better

digital filters. The lack of energy in

integrated overall, with a flatter mid-

the 50Hz and 63Hz bands is endem-

 

 

 

 

ic to my room and

 

 

 

 

seating

position.

 

 

 

 

But note the exten-

 

 

 

 

sion to 20Hz and

 

 

 

 

the very flat mid-

 

 

 

 

range,

 

meeting

 

 

 

 

±1dB

limits

from

 

 

 

 

250Hz to 16kHz—

 

 

 

 

superb

perfor-

 

 

 

 

mance for an in-

 

 

 

 

room,

 

listening-

 

 

 

 

position

measure-

 

 

 

 

ment. There

is a

 

 

 

 

slight

 

lack

of

 

 

 

 

upper-bass energy,

 

 

 

 

though not nearly

Fig.1

NHT Xd system, original XdA crossover filters, anechoic response on

as much

as I was

 

axis at 50", averaged across 30° horizontal window and corrected for

expecting from my

 

microphone response (black), with the nearfield XdS woofer (black)

 

auditioning.

 

 

and XdW subwoofer (green) responses plotted below 300Hz, and the

 

 

individual XdS woofer (blue) and tweeter (red) responses.

The red trace in

 

 

 

 

fig.3 is the in-room

 

 

 

 

response

taken in

 

 

 

 

an identical

man-

 

 

 

 

ner with the 150Hz

 

 

 

 

c r o s s o v e r / E Q .

 

 

 

 

Overall

it

looks

 

 

 

 

very

similar,

but

 

 

 

 

there are detail dif-

 

 

 

 

ferences that corre-

 

 

 

 

late with the listen-

 

 

 

 

ing

impressions.

 

 

 

 

There

is

more

 

 

 

 

energy

in

the

 

 

 

 

80Hz, 100Hz, and

 

 

 

 

125Hz bands, indi-

Fig.2

NHT Xd system, revised XdA crossover filters, anechoic response on

cating

better

inte-

 

axis at 50", averaged across 30° horizontal window and corrected for

gration

between

 

microphone response (black), with the nearfield XdS woofer (black)

 

the subwoofers and

 

and XdW subwoofer (green) responses plotted below 300Hz, and the

 

individual XdS woofer (blue) and tweeter (red) responses.

satellites.

 

That

 

 

 

 

 

 

 

 

www.Stereophile.com, January 2006