By way of spicing up her live act, Shirley Gray went gigging with Sennheiser's affordable BF1051 VHP wireless microphone.

It's a great way to spice up your live show — leaping off the stage and accosting selected members of the audience. They love it, too — the looks on their faces when you single them out says it all. Add to this the extra freedom to move around on stage, unhampered by trailing leads, and the idea of a radio mic seems more like a necessity than an up-market luxury.

Like many self-contained acts, I haven't used radio mics much before, because decent sounding ones have always been prohibitively expensive and eat batteries at four quid a throw. I am, however, seriously considering it now the price has come within reach. I had the deep joy of using the Sennheiser BF1O51, and I must admit, I haven't had so much fun for ages!

A German company, with an enviable reputation for quality, Sennheiser don't make 'cheap' products. Although the BF1O51 is at the lower priced end of their range, it does cost more than a typical budget radio mic. The real question is, do you get what you pay for?

OVERVIEW

The system uses a VHF frequency radio link, and in common with other radio mic systems, comprises two distinct units: a microphone with an in-built transmitter, and a separate receiver unit. As the mic operates within an unregulated VHF band, you can operate it without a licence. Power is supplied by a 9V battery in the mic and a mains powered transformer for the receiver, with a battery lasting a minimum of six hours.

Two switchable transmission frequencies are available, which means that if you are having trouble with one frequency, you can switch to the other. By 'trouble', I mean discovering that the taxi rank outside the venue is using the same frequency as you. Additionally, having a choice of two frequencies gives you the option of using two Sennheiser systems simultaneously, one operating on each frequency. Although there are several frequencies within the unregulated VHF band that can be used for radio mics, interaction between channels usually limits the number of VHF mics that can be used simultaneously to a maximum of three.

TRANSMISSION

The microphone, or hand-held transmitter (as Sennheiser like to call it), is of rugged polyamide construction, compact, and hides the antenna within itself. It has the typical Sennheiser good looks and styling, and at a mere 250g (including battery), it is wonderfully lightweight. The battery compartment is easily accessible via a hinged flap — no coins, screwdrivers, or long fingernails required — and battery replacement takes a few seconds. Alkaline batteries are recommended.

The frequency response is 40 to 18000Hz, which is as much as you'd need live, unless you're David Attenborough trying to record a live bat show for the benefit of dogs, of course. The signal-to-noise ratio is quoted as an impressive 120dBA, no doubt due to the use of compander technology, which is the usual way of maximising the dynamic range of radio mic systems. All this makes for a very interesting proposition, but the outstanding feature for me was the supercardioid pick-up pattern, which in the case of this particular mic, has to be experienced to be believed (I'll rave about this later). The idea is that the microphone has a very narrow acceptance angle and rejects sound from everywhere else (for a more detailed explanation, see 'Causes & Cures of Feedback' in the November 1996 issue). This means less likelihood of feedback — an important feature if you're going to be clambering up lighting rigs, wandering about in front of PA systems, or interacting with members of the audience.

There are only a few controls on the microphone itself, and these have been neatly housed in a little recess, so that you are unlikely to flip them in error. These are a switch for selecting either channel 1 or 2, a switch to reduce the sensitivity (which is effectively an attenuator for loud signals), and an on/off switch to save your batteries. You will need to have fingernails to operate the centre one of these!

RECEPTION

The receiver is built into a compact, half-width 1U housing, which can be rackmounted if desired. It operates on the true diversity principle, which in this case means it has two antennae, each with a separate detection circuit. Another circuit decides which of the two has the better signal-to-noise ratio at any one moment and uses that. The main reason for having diversity operation at all is that RF reflections from walls can sometimes produce dead spots, and if you wander into one of these, the transmission quality may well become unacceptable. With a diversity system where the antennae are spaced apart, there's more chance that at least one of them will be able to pick up a viable signal.

On the front of the unit is the power button, the squelch control, the channel selector switch, and the metering. The squelch control has seven preset threshold levels to choose from, ranging from 4 to 300 microvolts. Squelch controls are a bit like noise gates in that they turn off the signal when the RF signal level falls to an unacceptable level. In other words, if you wander out of range, the signal will die gracefully rather than dissolving into a cacophony of static. It is a little fiddly to use, but you should only need to set it once.

The channel selector switch needs to be set to the same as that on the microphone and determines which of the two frequencies you will be operating at. Incidentally, the two operating frequencies are displayed on a sticker inside the battery compartment in the microphone.

Now to the metering. The first meter is the RF signal level, which allows you to find the optimum position for the receiver so that the maximum number of LEDs are lit when you are transmitting from the microphone (ie. when it is turned on — you don't need to be making a noise into the mic). Too few LEDs means too much hiss. Next, the two Diversity LEDs show you which antenna is being used. On the right of the unit, the second meter indicates the audio input level and shows you when the sound signal is too high and overloading the device. You can then attenuate it, if required, using the Lo/Hi switch on the microphone.

On the rear panel are the two detachable antennae. The output to your mixer or stage box is derived from either a balanced XLR socket or an unbalanced jack socket, and there is an associated output level control. Optional extras include a 1U rackmount kit, which fits two units side by side; a remote antenna; a choice of five or 10 metre antenna cable; and various voltage power supplies, so you can take your Sennheiser on your next World Tour. Different countries have different radio frequency regulations, but that's another story entirely!

ROAD TEST

The 1051 comes in a black attache-type case with carrying handle, and assembly only takes a minute or so. Setting up the squelch is done by moving to the point where you're starting to go out of range and the signal starts to get noisy. At this point, you adjust the squelch threshold until the noise is gated out. Then re-check that your voice isn't being gated when you move back into working range. If there is a lot of interference, you may need to set a higher squelch level, and you'll have to limit the distance you wander away from the receiver.

One of my gigs was in a medium-sized city centre hall. With the receiver situated on the stage, I was still transmitting a clear, low noise signal from the back of the hall. This may vary, of course, depending on circumstances, and I was probably quite lucky as there was no taxi rank outside. I used the BF1051 at five gigs and suffered neither interference problems nor signal loss, no doubt due in part to the effectiveness of the true diversity feature. However, on a more rigorous test, I took the mic up a hill by some solid iron fence posts and encountered heavy interference above 50 metres.

I was pleased to note that operating the power switch on the microphone did not cause any click or thump, but on the downside, I thought the mic was subject to more 'popping' and handling noise than some other mics I've used. Applying good microphone technique can minimise this problem.

By far the most impressive aspect of the Sennheiser BF1O51 is the sound quality. I surprised myself with this full, rich vocal sound emanating from the PA, complete with crisp, airy top and smooth, creamy mid. I regularly use a Beyer M88N wired mic, but I have to say I preferred the sound of the Sennheiser for live use with my voice. The top frequencies cut through without being piercing or harsh, which is important when trying to maintain clarity. The supercardioid pick-up pattern did seem to improve feedback immunity, but the other side of the coin is that you have to adapt your mic technique to working with a hypercardioid. The narrowness of the pick-up pattern took some getting used to, and even a slight movement to one side, when looking at the neck of my guitar, resulted in an appreciable loss of volume. However, it was well worth it for the benefit of having so little in the way of feedback problems, and I soon learned to move my eyes instead of my head.

FINALE

Having become familiar with the Sennheiser BF1051, I am reluctant to give it back! But, sadly, I must — at least until I can justify the expense. I've never considered buying a radio mic before, simply because for the sort of price I could afford, the sound quality was always poor, and I was unwilling to compromise the sound for the sake of the show and the convenience of no wires. Now, however, I am seriously considering it.

The BF1051 is very simple to set up and use, and although it's not cheap, I do think that you do get value for money. The usable range is around 50 metres, which is largely determined by current legislation on power output, but this is still more than enough for most typical gig situations. I like the design department's attention to detail when it comes to the styling and the ergonomic positioning of the knobs and switches, with the exception of the Squelch control, which is rather fiddly. Most importantly, perhaps, Sennheiser have proved to me that you no longer have to spend thousands to get a decent sound quality. I just hope I can hang on to the BF1051 long enough to use it on my next gig!

BF1051 £599 inc VAT.

Sennheiser UK Limited, (Contact Details)