The Townshend Rock 7 (R7) is an open-style record player which incorporates all the engineering and functional features of the Rock V but at a considerably lower cost. The R7 in its basic form is supplied without the familiar front-end damping trough characteristic of all Townshend Rock turntables to date. However, the trough and outrigger/paddle are together offered as an optional extra, which will transform the turntable to performance levels approaching the Rock V and surpassing most conventional turntables, regardless of cost.
Further upgrades comprise a record clamp, more powerful motor and flat belt, which, in conjunction with the optional Merlin II Electronic Power Supply, will give a significant reduction in noise and more accurate drive stability with an associated improvement in sound.
The turntable is supplied without a pick up arm, but with the armbase of your choice. Armbases for Rega, Linn, SME, Jelco and Townshend Excalibur II arms are available “off the shelf”. Others are available to special order.
Subchassis
The R7 comprises a very substantial sub-chassis upon which is mounted the platter bearing, overall leveling counterweight and the optional trough, all of which are suspended symmetrically on three spring/bellows feet. The motor box, which houses the 24 pole 250 RPM synchronous motor with its associated two-speed drive pulley, IEC mains power input socket and on/off switch, is positioned independently of the main turntable assembly on the supporting table. This arrangement ensures exceptional isolation between the motor and the turntable. To change speed, the standard round-section drive belt is positioned on the appropriate section of the motor’s stepped wheel to provide 33 or 45 RPM.
The platter bearing is a unique one-piece precision-ground steel shaft with a hardened bottom-end resting on a steel ball, all lubricated with state-of-the-art synthetic oil as developed for Formula 1 race cars. This sits in the bottom of a brass bearing-journal which is fixed to the main chassis. The bearing shaft extends right through the sub-platter and the main platter, emerging at the top to form the spindle which centers the record. The top of the spindle has a threaded hole to take the standard Rock record clamp. This is optional but we recommend using it as it improves virtually all aspects of the sound. The platter is a substantial disk of polyethylene plastic, chosen to have virtually identical physical properties to the vinyl LP. This sits on a smaller diameter precision machined aluminum sub-platter. We have arrived at this arrangement over many years of turntable design and research and it is another step towards the goal of preserving the sonic integrity of the signal as it is extracted from the grooves.
The metal parts are all solid steel powder-coated with a very tough, texture black polyester paint. All the fixings are heavy duty industrial grade stainless steel to ensure maximum strength and extra long life in today’s rough and polluted environment.
Trough Open
The sound of the Rock 7 with the trough and a good moving coil cartridge is astounding. The sound has a natural balance over the whole frequency range, with powerful deep bass combined with fast transients; clear wide sound in the mid band with silky smooth highs. Clicks plops scratches and all the normal artifacts associated with vinyl are enormously reduced because the rigid coupling of the headshell to the trough prevents the ringing vibration that would otherwise occur.
The polyethylene platter ensures a virtually perfect mechanical impedance match between the record and the platter surface. This means that the sound wave which radiates from the stylus-tip whilst playing is transferred without reflection into the bulk of the material, where it is naturally absorbed in the slightly lossy bulk of the platter. This mechanical damping process is crucial for clear reproduction as early reflections at this point, due to (very common) mechanical impedance mismatches, cause strong early reflections of the musical information coming off the disc. This, of course, is a form of distortion and significantly blurs the sound.
The Townshend Trough assembly is fixed to the trough-plate which in turn bolts securely to the main chassis. The paddle attaches to the headshell by a double outrigger arrangement which is mounted above and below the headshell and above the cartridge. This ensures intimate coupling between the headshell, cartridge and paddle, essential for the most accurate sound reproduction.
Outrigger and Paddle in position whilst playing
The outrigger is an integral part of The Townshend Excalibur arm’s magnesium headshell, for the ultimate in accurate reproduction of the minute modulations of the record groove.
The comprehensively adjustable counterweight arrangement is provided to ensure that the turntable is perfectly dynamically balanced and level. The assembly consists of a slotted plate, which is attached to the chassis by a substantial bolt and a selection of steel discs which are chosen to balance the suspended assembly taking into account the weight of the pick-up arm and the trough. When played in its basic form without the trough, the turntable is a match for most conventional turntables, regardless of price.
Counterweight and Motor
This superb performance is achieved through a thoughtful approach to the problems usually inherent in the replay of vinyl records, in the selected platter material as previously outlined, and most importantly, the astonishing performance of the spring/bellows feet. The isolation ability of these springs is closely comparable to that of completely undamped low-loss springs and, in conjunction with the mass of the suspended assembly, results in a resonant frequency of about 3 Hz. This ensures that vibration from about 5 Hz and upwards is attenuated by 12 dB per octave. This situation exists for normal undisturbed playing; however, in the event of a large disturbance the bellows with their associated air damping ensure that the suspended structure comes to rest almost immediately.
However, the turntable in this form still suffers from the major weakness of the conventional record player: the undamped arm-cartridge resonance caused by the nature of the cartridge’s suspension and the mass of the arm and cartridge. This undamped mass/spring assembly causes an increase in output from the cartridge of 15 to 20 dB at 10 Hz, 5 dB at 20 Hz and 2 dB at 100 Hz. This excess low frequency output results in non-linearity in the cartridge’s performance, overload of the phono stage’s electronics, huge circulating currents at the power amp/speaker interface and huge cone excursions by the loudspeakers.
Further, when the stylus/cantilever moves back and forth, the cartridge/arm is forced to follow to a greater or lesser degree, depending on the size of the groove’s modulation. After all, it is common sense that, if the cartridge is moving with respect to the record’s grooves, a sound is generated. This sound is not the music, but an unwanted and avoidable extra noise superimposed on the music.
As the cartridge tends to chase the modulations in the groove, especially at low frequencies, the resulting sound has a softening in bass transients, especially kick-drum and a blurring of low frequencies generally, producing an overblown and unnatural bloom in the bass. Most gramophone users have lived with these distortions all their lives, as they are effectively intrinsic to the way that vinyl records are normally played. Many people even like them! How often have we heard of people enjoying “vinyl’s warmth”? Furthermore, many listeners experience a broadly benign artificial “echo effect” which often gives the music a feeling of added dimension or space. But, is this what we really want?
Now add the optional trough assembly and everything changes. Suddenly we have achieved a considerably greater correlation between what is in the record’s grooves and what is coming out of the speakers!
Left image: camera hand-held. Right image: camera mounted on tripod.
A convenient analogy is demonstrated in the above two images of the same scene. The first is a hand-held shot where the movement of the camera adds unwanted “jiggles” to the image, which are absent from the actual scene. This is equivalent to the conventional turntable with no trough, where the arm and cartridge can flap around, adding unwanted artifacts to the signal from the record. In the right hand shot, where the camera is mounted on a tripod, the image shows virtually no “jiggles”, and provides a far more accurate and detailed view of the scene. This is now equivalent to the arm and cartridge being locked steady by the paddle in the trough, while still tracking the groove as the record plays.
Graph 1 – low frequency response with and without damping
Graph 1, low frequency response, shows how the arm-cartridge resonance peak is calmed to insignificance by the damping action of the trough assembly.
Graph 2 – Rumble without damping (left) and with damping (right)
Graph 2 shows how rumble artifacts at around 8 Hz, caused by the arm/cartridge flapping around, are totally eliminated when the trough is introduced.
Once you have experienced music played on a Rock Turntable with the trough, the thought of returning to a conventional turntable……………………….
