Wednesday, June 24, 2015

NHT Classic Four Floorstanding Speaker System Review


is a small but highly respected loudspeaker company located in Benicia, CA. Originally

founded in 1987 by speaker industry engineering superstar Ken Kantor (who did

the groundbreaking AR Magic Speaker in 1985), NHT has earned a well-deserved

reputation for speakers that sound superb, feature innovative, straightforward

engineering, and utilize the highest quality materials for great cosmetics and

fit-'n-finish. NHT operates on a direct-from-the-factory business model, which,

according to them, saves the intermediary costs of sales reps, distributors and

retail markup, allowing NHT to offer a better value directly to the end user.


in California and manufactured in China, the Classic Four is a mid-sized floor stander

in their Classic family, which also includes the Classic Three 3-way bookshelf

speaker and the Classic Two C and Three C center channel 3-way speakers. All

these models use the same 2-inch anodized aluminum dome midrange and ¾-inch

anodized aluminum dome tweeter array.  At

$1,349 each, the Classic Four certainly can't be considered inexpensive, but

just based on the quality of the materials and workmanship, they appear to more

than justify their asking price. The head engineer on the Classic Four project

was Jay Doherty and

the engineer most responsible for the dome mid-tweeter assembly was Jack Hidley.

The care and attention to detail in this design was most impressive, as you'll see

as you read the review. But these two gentlemen deserve a conspicuous mention

right up front. 


around 41" tall and only 7.5" wide with gently smoothed-off edges, these speakers

do not attract a lot of visual attention in the room. They're attractive but

self-effacing and I doubt their visual presence would trigger a dreaded negative

WAF to any significant degree.

Design Overview


Classic Fours were double-boxed in two medium-duty corrugated cartons and had

high-quality EPS foam caps and an EPS "waistband" holding the speaker around

their midsection, top and bottom.  There

was a specific Left and Right speaker, even though they differ only in the

direction the woofer faces and the woofer is non-directional at and below its

crossover frequency. Mostly to make the customer feel good, I suppose. That's

ok. And while bass in this

frequency region is omni-directional, some placement situations force a

consumer to put one side of the speakers next to a wall unit or in a corner. Also, small changes in room position can have large effects on the bass output.  Changing the speaker position so that the

woofers face in instead of out might make a difference in output depending on

the room shape and listening position.

 double boxed.jpg

Double-Boxed Packing


packaging was fully up to the task of protecting the speakers, as they arrived

in perfect condition after a cross-country (CA to MA) Fed Ex Ground journey.

One minor suggestion: I'd recommend that NHT cut small oval hand-holds (about 4

x 1.5") into the carton, so one person can carry them more easily. As long as

it's not too unwieldy, most adult men can handle a carton between 50-80 lbs

without too much difficulty. But you have to have something to grab onto.


packing material is interesting: Regardless of the so-called "burst rating"

printed on the corrugated carton or what kind of internal foam packing material

they claim it is, in order to get the "good stuff," a manufacturer has to pay a

Chinese vendor top dollar. Generally, Chinese cartons rated below 200 lbs.

burst are made out of what manufacturers derisively call "cheese paper,"

flimsy, lightweight material that seems ready to disintegrate under the

slightest stress. These cartons had no visible burst test rating certification

but were clearly made from very good quality material. 

spkr in carton, bag.jpg 


Four in Double-Boxed Packing


the internal foam packaging falls into two broad categories: 1) the cheap kind (polystyrene), that breaks into

pieces and crumbles into tiny foam sawdust balls that float annoyingly all

around the room, rendering impossible any thought of repacking with the foam

inserts, and 2) the good foam (polyethylene),

which stays together and makes repacking easy and repeatable.


uses very high quality packaging. Having been involved in the design, sourcing

and manufacturing of consumer electronics products for decades, I know the cost

difference between good and bad materials, and what that says about what a

given manufacturer thinks of their products and the image and impression they

wish to convey to their customers.


was a good first step.


midrange/tweeter grilles were shipped already attached to the speakers but the

speakers themselves did not have any kind of protective clear plastic shield

placed over the baffle board to protect these delicate upper range drivers

during shipping and removal from the carton/initial setup. I have seen many a

tweeter dome ruined by wandering fingers as the speaker was grabbed and

carelessly pulled out of its box and NHT didn't take any special efforts to

avoid this. No demerits to them for this--this is normal packaging procedure--but

they would've receive a special shout-out if they had done it.


speaker's 2-part (left side/right side) base and the carpet spikes/rubber feet

for hardwood floors were packaged in a separate internal cardboard box. The

base, made of bulk molding compound or BMC - (also used on truck and

airplane parts, and other parts where rugged durability is required) runs

almost the full depth of the speaker (about 13 inches) was finished on its

upper side to match the gloss black of the cabinet. It was nicely done, solid

and beefy. It attached to the underside of the cabinet with three machine

screws and an Allen wrench provided in the accessory bag. The threaded inserts

themselves were mercifully free of paint contamination or other obstructions and

everything snugged down nice and tight, just the way it was supposed to.

spikes etc.jpg       plastic feet.jpg


Four Accessories and Feet


was another accessory that was unexpected: A small "double-smile" self-adhesive

foam strip (NHT calls it the "moustache")

that went between the dome midrange and the dome tweeter, ostensibly to reduce

the effect of any audibly destructive baffle reflections or driver interference

that might reduce overall system clarity. While I have no doubt as to the

theoretical and measured legitimacy of this device, in terms of its audibility

under practical real-world conditions, I'd be willing to wager Gene's life

savings that there would be absolutely zero statistically-significant

correlation between its presence or absence during listening sessions of actual

program material. But NHT has such a good engineering reputation and I

understood exactly why they provided the strips, so I used them. Maybe that was

the point after all. The placebo effect among audiophiles can be very strong. 

Wide dispersion was a stated design goal for the Classic Four and NHT went about it the right way.


Classic Four is a true 4-way design. The side-firing woofer handles only the

very low, non-directional bass (below 125 Hz) and then hands off, so to speak,

to a forward-firing 3-way speaker. Assuming high-quality drive units and good

crossover design with steep filters, a good 4-way can achieve excellent deep

bass, clear upper bass/lower mids, and then have very small, wide-dispersion

units handling the upper frequency ranges. If the designer's goal is strong

deep bass that doesn't have to handle the vocal range, and then have small,

quick, wide-dispersion drivers for the upper middle/treble range, a

well-designed 4-way is about the only way to go. Most designers these days do

not put much of a premium on ultra-wide midrange and treble dispersion, so for

them, larger cone midranges and 1-inch tweeters are just fine. That's probably

the main reason we don't see small dome midranges used very often these days. A

generation ago, dome midranges were commonplace. Nowadays, they've fallen out

of favor. NHT's Classic Series is one of the very few modern speaker designs

that use a dome midrange.


dispersion is primarily a function of driver size relative to wavelength. If

the driver's diameter is smaller than the wavelength of the frequency it's

reproducing, the dispersion is very wide. If the driver is larger than the

wavelength being reproduced, the driver will "beam" its output forward like a


Wide dispersion was a stated design goal for

the Classic Four and they went about it the correct way. Each of its four

drivers exhibits extremely wide dispersion in their respective assigned

frequency range, so the sound is expansive, wide open, very "large." The

downside of super-wide dispersion is a commensurate reduction in so-called

pinpoint "imaging," so the listener has to make the decision as to which design

approach they like the best. To overgeneralize, wide-dispersion designs are

better suited to two-channel music listening and more focused dispersion may be

a bit more suited to multi-channel theater applications, where extremely

precise localization and coordination of visual and audible signals are

desired. In my room, listening to them strictly in a two-channel music configuration,

they sounded truly superb.


Classic Four might be compact at 41" tall x 7.5" wide, but it's very heavy for

its size and conveys a very solid impression to the user. There are two sets of

binding posts, connected by a brass "jumper" strap, just above the rectangular

rear vent. The ends of the posts do not

have the usually-required plastic CE (European) safety plugs, as I'm used to

seeing. Apparently, NHT does not do business in CE countries, so there is no

need for those annoying plastic caps. If you want to use banana plugs instead

of bare wire to connect the speaker wire to the posts, you're free to do so.

The posts themselves have a nice-sized hole to accept bare wire and that's how

I connected them with 14-ga wire. Nice, easy, and secure. I did not use the

bi-amp feature, but it's nice to know the option exists.



Four Binding Posts


cabinet itself was made of high-quality MDF, more than 1-inch thick on the

front panel. (Again, not all Chinese MDF is created equal--there is "good,"

solid Chinese MDF and there is flaky, cheap Chinese MDF. This was the "good"

kind. Note: NHT says their MDF and corrugated carton material is

imported from New Zealand, not China. The driver areas on the baffle

were routed out, so those sections are a little thinner than the rest of the

cabinet walls, unfortunately.  And

interestingly (and surprisingly), the cabinet's sidewall--where the 10-inch

woofer is mounted--is just the standard ¾-inch thickness. I'd have thought that

the woofer

panel, not the midrange/tweeter panel, would be the thickest since it is

most subject to vibration from low frequencies. 

Manufacturer's Comment: The woofer is inset into its own 21mm MDF

piece, so the total thickness around the edges is 37mm. In addition, there is a

1mm aluminum sheet glued to the inside wall opposite the woofer (to give a 30%

increase in stiffness).


the inside of the cabinet has extensive windowpane bracing, which contributes

to the cabinet's overall solidity. The upper surface of the rectangular vent

also doubles as an internal cabinet brace, just below the woofer. Right above

the woofer is a "windowpane" brace. So even if the woofer panel is only 19mm

thick (even thinner where it's routed out for the driver mount), there appears

to be sufficient solidity around the woofer. 

No harm, no foul.


6 ½-inch midrange driver is in it's own isolated chamber within the cabinet.

Both the midrange enclosure and the main cabinet interior are stuffed pretty

densely with a fiberglass-ish (probably

a flame-resistant polyester) material throughout, no doubt with the

intent of reducing internal cabinet resonances and standing waves to a minimum.

One gets the overall impression that this is a very inert cabinet that does not

negatively intrude on the speaker's sound.

upper x-o, brace.jpg 


Four Internal View of Upper X-O, Cabinet Bracing, 1-inch Front Baffle


tweeter is a ¾-inch anodized aluminum dome. In keeping with NHT's avowed wide-dispersion

design goal, the Classic Four is one of the few speakers on the market that

uses a ¾-inch tweeter instead of the ubiquitous 1-inch dome.  The midrange from 800 Hz to 4,000 Hz is

handled by their truly excellent 2-inch dome midrange.


is a very business-like speaker with the grilles off. The dome tweeter and dome

midrange are mounted on a common faceplate adorned with a small NHT logo at the

top. The faceplate itself has the feel of metal, but it's actually a very dense

bulk molding compound (BMC). Very strong, very dense, not "ringy" at all. An

excellent choice of material.



Four w/ Grille Off


dome drivers have what appear to be clear plastic phase plugs/dispersion lenses

in front of them, although NHT never states what they are or what purpose they

serve. They could just be protection devices to ward off prying fingers, but

usually these elements have an acoustic function as well. It's interesting to

see a ¾-inch dome tweeter again after all these years. Acoustic Research (the

pre-eminent U.S. speaker company in the 1950s-1970s--they invented the dome

tweeter in 1958) used various versions of their ¾-inch dome tweeter for decades

in their top models, since the widest possible high-frequency dispersion was

always a corporate design philosophy. But as I stated earlier, the 1-inch dome

tweeter--with its vastly greater power handling and ability to cross over low

enough to make a very effective 2-way system--has all but replaced the ¾-inch dome

tweeter as the tweeter of choice. The Four's tweeter used a neodymium magnet

and a finned aluminum heatsink attached to the backside for added power handling.

mid-tweet w foam.jpg        mid-tweet no foam.jpg

Classic Four Midrange-Tweeter Assembly With and Without

Anti-Diffraction Foam


the 2-inch dome midrange used in the Classic Four. It has what I would estimate

is a rather substantial 6 mm (1/4-inch) cloth-roll surround, giving this driver

surprisingly good excursion capability--which it needs, since it is crossed over

at a relatively low 800 Hz. Compared to the usual 5 ¼-inch or 6 ½-inch midrange

driver and 1-inch tweeter which would handle the 800-2,000 Hz range in a

typical 3-way speaker, the NHT Classic Four will have incomparably broader

dispersion. In fact, the Four is essentially omni-directional in the forward

hemisphere, which gives the speaker a notably "unboxy" sound character and lends

itself to great listener and speaker placement flexibility.

I have

to admit to being somewhat surprised that the 2-inch dome midrange did not have

any external heatsinking attached to its backplate. Considering that this

driver is tasked with handling frequencies down to 800 Hz and will therefore be

exposed to a fair amount of drive current, I expected some extra heatsinking

would be called for. 

back tw-mid plate.jpg      

Back of

Tweeter-Midrange Assembly


this is just another of many instances where Monday-morning quarterbacking by

people (in this case, me!) not involved with the actual design process make

totally speculative comments that probably have very little to do with the

reality of the situation. I am willing to accept on faith that NHT, a very

solid engineering company, performed all the requisite power-handling and life

tests on that midrange driver in situ and concluded that additional heatsinking,

which is an added expense, was unnecessary.

Manufacurer's Comment: The

motor is quite substantial, so there is plenty of thermal mass.  Also, the response is down 6dB at 800Hz and

doesn't reach full output until 1400Hz where it is out of the range where music

has the most power concentrated.  No one

has ever blown one up by playing the speaker too loudly.


was not able to remove the 6 ½-inch lower mid/upper woofer to get a look at its

backside. It was just too snugly nested in the cabinet and prying it out would

have resulted in damage to the Four's beautiful gloss black front panel. I just

didn't have the heart. The frame seemed to be made of the same bulk molding

compound (BMC) as the midrange-tweeter faceplate and the overall visual

impression of the driver was in keeping with the high standards of the other



side-mounted "subwoofer" in the Classic Four is one beefy driver. It may only

be a woofer, not a subwoofer, but it's well-executed. It's a stamped-steel

frame, but the frame is reinforced and vented in many areas to facilitate

effective heat dissipation. I was quite surprised to see a magnetic shielding

"can" over the magnet assembly. This was common in drivers 20 years ago to

prevent the driver's stray magnetic field from interfering with the picture

when used near CRT televisions in home theater systems. Magnetic shielding

hasn't been needed for that reason since the advent of flat-panel TVs many

years ago. One wonders why NHT still does this. It could be a way to increase

the BL (a Thiele/Small parameter) of the speaker's magnetic motor and optimize

its sensitivity, since a shielded driver is often a dB or so more sensitive than

its non-shielded counterpart. I'm just speculating here. It has what appears to

be a 2-inch voice coil, a nice beefy-sized coil for a 10-inch driver, and that

no doubt contributes to this driver's sense of articulation and control.

woof basket vents.jpg 

Classic Four 10-inch Bass Driver Basket Vents

woof, term cup.jpg  


Four Side-Mounted Bass Driver

Crossover, Grilles,

Cabinet Finish


crossover is a pretty conventional design, using standard parts. It's split

into two sections: The high-frequency section is mounted behind the

tweeter/midrange assembly at the top of the cabinet, while the lower-frequency

section is mounted behind the terminal cup in the lower part of the cabinet,

near the 10-inch driver.

lower x-o.jpg 

Lower Crossover Section (PCB in back of rear terminal



rear-facing rectangular vent for the 10-inch woofer is part of the cabinet

construction, rather than a conventional plastic port tube, as in typical

bass-reflex designs. It's actually a clever design from many angles: The

cross-section of the vent opening is large enough that "chuffing" is not an

issue; NHT doesn't have to buy or tool any molded plastic port tubes or flares

as they would had they used a port tube; the vent's construction serves

double-duty as internal cabinet bracing around the woofer. These are the little

hidden things that strong engineering companies like NHT do and the customer

has no idea how intelligent the design is just by looking at the outside of the



Four Woofer Cabinet Rout and Internal Vent Brace


grilles were nothing special--just the standard plastic frames covered with

stretched black cloth, and plastic "trees" that inserted into rubber grommet

receptacles on the front baffle. Many speaker companies these days are using a

slicker design of neodymium magnets hidden just beneath the surface of the

front baffle, which then "grab" and precisely locate the grille frame (which

would have reciprocal metal "coins" imbedded in the plastic frame to attract

the neo magnets). More costly in both materials and manufacturing time, and not

in keeping with NHT's no-nonsense direct-to-the-customer business model.

The black gloss finish looked great on these speakers.


Classic Fours came in a gloss black paint finish. If a manufacturer is only

going to offer one finish, it's usually black, since black will go fairly well

in almost any décor or room color scheme. Gloss black is hard to do well, since

it's very unforgiving of ripples, "orange peel" imperfections, tone and sheen

variations, etc. A semi-gloss Satin Black is generally a better choice for a

single-finish offering, since it's easier to get it right, it doesn't show

smudges and fingerprints nearly as badly, and if done well, a Satin finish will

still have an aura of luxury and high cost. Still, a Gloss finish, done

correctly, looks great, no question. These were done correctly. They looked

great. However....consider me a traditionalist. I'd love to see these speakers in

a beautiful real-wood veneer finish, perhaps a nice Cherry or medium-toned

Maple. But from a manufacturer's standpoint, I certainly understand the appeal

of offering and inventorying only one finish option. Any color you long

as it's black.

Manufacturer's Comment: NHT doesn't

do real wood veneer, since it's not eco-friendly. We use an eco-friendly paint.



set up and listened to the Classic Fours in a 2-channel music system. The room

was a small-to-medium sized 17 x 14 x 8 ft. These are very good-sounding

dimensions, since the length (17) is a prime number, and the height (8 ft) is

not a whole number multiple of either the length or width. Therefore, these

dimensions do not lend themselves to troublesome, additive bass/room

resonances. The room has six 2 x 3 ft acoustic wall treatments staggered around

the four walls (one centered on the front wall, two each at different heights

on the side walls, and once centered on the rear wall between the two windows).

There is a large sectional couch for seating and the floor is carpeted.

Overall, the room is just slightly on the dead side of neutral, and it sounds

excellent: solid, uniform bass, good imaging and detail, very little "ringing,"

but live enough to let the speakers blossom out and fill the space with organic

sound. Excellent recordings, especially of small-scale ensembles like jazz trio

or solo piano, can sound almost live in this room. I have tremendous confidence

that this room allows equipment to sound as good, or bad, as it can.


Classic Fours were set up about 1 ½ feet from the wall behind them and about 2

½-3 feet from the sidewalls. I experimented with placement by moving them

closer to the wall behind them, but found that the balance got a little 'tubby'

when the speakers were within about 6 inches to a foot of the wall. The

speakers have extremely good horizontal dispersion and toe-in was

minimal--perhaps 5º or so. Set up this way, the speakers threw a very solid,

well-defined image with a good phantom center and, just as importantly, almost

total immunity from stand-up/sit-down pickiness. That is attributable to the

very close spacing of the two dome drivers (well within a half-wavelength at

the crossover frequency of 4,000Hz), which enables them to act as a virtual

"point source."

Associated Equipment


rest of the system is simple but straightforward, and very high quality. The

pre-amplifier/power amp combo was Parasound's New Classic 2100 pre-amp and 2250

power amp, rated at 200/385 watts per channel 20-20k, into 8/4 ? loads,

respectively. (Since the Fours are rated at 6 ?, we'll assume around 300 WPC.)

The CD player was the NAD 545 with Burr-Brown DACs. Considering the modest size

of the listening room, this is more than enough clean, distortion-free power to

ensure that the electronics never intruded upon the listening sessions in a

negative way. Speaker wire was simple 14 ga. twisted-end, inserted into the holes

in the binding posts. Basic Monster interconnects between the pre/power and the

CD/pre. Nothing lunatic-fringe about the connectors and speaker wire, and more

importantly, nothing that could even remotely be considered a defining or

distracting influence on the sound.

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