Electrovoice PL10

The Electrovoice PL10 is a cardioid dynamic microphone which looks very much like a cut down version of the popular RE20.  It has no transformer or filter circuit but it still sounds excellent. These omissions presumably kept the price down.

Just like the RE20, the foam that holds the capsule in place can cause trouble. Over time this can degrade into a sticky pulp and then the capsule becomes loose and rattles around and may eventually destroy itself. This microphone needs new foam and a good clean right away!

The microphone body is in three parts – grill, body and base – which are screwed together and some kind of glue applied. I had to heat the threads and apply more force that I would like to break the glue and get the microphone apart. That was the hard part of the job, and once opened it is easy to remove the foam with a bit of isopropyl alcohol. As always, care must be taken around the diaphragm to avoid damage. The metal parts went into the ultrasonic bath and cleaned up nicely. 

Once back together, the PL10 is an excellent sounding dynamic microphone. The PL10 should be a cheap alternative to an RE20, but in fact they are scarce, and prices on eBay and Reverb may be higher than an RE20, which is a bit daft. 

Here are some comparison frequency sweeps of the two mics conducted at around 25cm from the source (as usual take with a pinch of salt.)

Frequency sweeps for RE20 (red) & PL10 (blue)

Electrovoice V2 revisited

These old Elctrovoice ribbon mics look great but sadly the sound rarely lives up to expectations.

I have worked on a few of these over the years and there are several things that let these microphones down – happily they can all be sorted out with a bit of thought.

EV V2 clamp with through-ribbon bolt!

Firstly, and perhaps most annoying are the ribbon clamps. EV used thin plastic clamps to insulate the ribbon from the body of the mic, and the ribbon is secured by a central screw that goes straight through the ribbon. The old EV ribbons are quite thick and were supplied with (even thicker) copper end terminals,  so that they could just be screwed in place. One problem is that tightening the screw twists the ribbon, pulling it into the side walls of the motor. It also does not make very good electrical contact, especially with a new thin aluminium ribbon. And the clamps are flexible too so the ribbon is not held securely.

New ribbon silver clamp

A better solution is to make new stiff metal clamps. These could be made from plated brass but I tend to use solid sterling silver to avoid the need for a plating process. One clamp must still be insulated from the body of the microphone to avoid shorting out the ribbon.

Rusty old magnet.

The next problem is the weak magnetic field. Replacing the old magnet with a new neodynium one can boost the field around five-fold, which gives a corresponding increase in output. With stronger magnets the steel screws can jump into the ribbon gap and wreck a new ribbon, so it is best to swap the screws out to some brass or stainless ones.

EV V2 transformer.

The old transformers are not great and lack bass but that’s an easy thing to sort out! And finally the old plugs are getting hard to find so we can put an XLR on the rear.

XLR fitted to EV ribbon mic

Voila! With new clamps, ribbon and magnet we have a healthy signal with plenty of bottom end!

Electro-Voice Microphone Catalogue

Here is a scan of an old Electro-Voice catalogue, probably from the 1950s or early 60s, featuring a wide range of microphones. It includes the multi-pattern Cardak, which appears to have been the flagship model, and the V-series ribbon mics. There is no date on the document, but at this point in time the V1 would set you back US$27.50, and the multi-impedance V3 was $50. The Cardak II would set you back a whopping $75!

In the velocity microphone description I was amused to read that “the woven housing allows the sound to pass through without reflection”. This neglects to mention the whopping magnet located at the rear of the ribbon! All of the dynamic ribbon mics were available in 50, 200, 500 ohm and high impedance models, which reflects the plethora of input types around at that time.

The second page deals with carbon and crystal microphones and accessories. The bottom of the page was uppermost in the box, and consequently is somewhat grubby.

ElectroVoice EV RE20 vs RE320

Everyone who has worked with me will know that I am a big fan of the EV RE20 / PL20 microphones.  Although perhaps most famous as a radio presenter’s mic, they are used throughout studio-land for kick drum, horns and vocals – Thom Yorke from Radiohead is one famous user.  In our studio, they are the go-to dynamics for pretty much everything that makes a loud-ish sound –  kick drum, toms, bass, guitars, horns, vocals, percussion, organs, science experiments, and so on. We have three, and I could happily use more.

From top. EV RE20, PL20, RE320 and another RE20.

I don’t really like severe EQ’ing, particularly with digital EQ, and so the idea of having an RE20 that is voiced for kick is particularly seductive. So, I was very eager to get my hands on the new EV RE320, which is an RE20-shaped thing that is specifically designed for kick drum. But wait! It is also specifically designed for vocals and instruments. How does that work?

EV RE320 switch with kick drum (left) and ‘flat’ settings.

Whereas the original RE20 has a switch which operates a high pass filter circuit, the switch on the RE320 gives different voices for different applications, giving access to ‘flat’ and ‘notched’ settings.

So, what are the differences between an RE20 and an RE320? The most obvious thing is that the RE320 is very black…. supermassive-black-hole black. in fact. And it comes in a zipped reinforced thing that is a hybrid between a box and a bag. This is a big improvement on the crappy plastic boxes that the RE20 came with, which tend to snap at the first opportunity. The RE320 is also about £150 cheaper than the RE20, and is ‘assembled in China’, whereas the RE20 is ‘made in the USA’.

RE320 snug in its little box-bag

More importantly, what about the sound? Here is a frequency plot of a ‘normal’ RE20, recorded in the Xaudia test chamber at 20 cm from the source. The blue line is the flat setting, and the green is with the HPF switched in.

RE20 response (blue) and with the HPF (green)

I had hoped that the flat setting of the RE320 would be be the same as the RE20, but in fact the new model is brighter and louder. Here is the RE320 in ‘flat’ (red) and ‘kick’ (green) modes, along with the RE20 in blue as a reference….

RE20 (blue), RE320 in flat (red) and kick (green) modes.

The RE320 has a higher output in both positions, and also has a peak around 4 to 6 kHz, which may brighten up some vocals. And there is other stuff going on too! A more revealing way to look at the behaviour of the ‘kick’ position is as a difference plot…

RE320 – difference between the flat and kick drum settings.

This plot shows a complex filter network being applied, with a low shelf boost, a -4dB cut at around 350 Hz, and a +5dB boost at 3.5 kHz.

Despite the differences, the RE320 does sound like it belongs to the same family – in fact it sounds rather similar to an RE20 with a +5dB boost around 4-5 KHz. I guess that makes sense!

Only time will tell if I will love this as much as the RE20, but it is a decent dynamic mic and will certainly find uses. I will report back once I have used these on a real recording session.

Stewart, Xaudia

Fun with magnets and an Electrovoice V1 velocity ribbon mic

Here’s an early Electrovoice velocity ribbon mic, model V1. These are great looking microphones, but the early versions are rather crudely made and this one, like many others, suffered from low output due to weakened magnets.

Bob Crowley has a few things to say about these mics – not all of them nice!

The motor of this model is based on a single cylindrical permanent magnet, clamped to a pair of metal plates which make up the pole pieces of the assembly. Because of the positioning of the magnet, the magnetic field is uneven, with a significant difference in field between the top and bottom of the motor assembly. In our example we found that the field varied from around 700 gauss at the bottom to 1000 gauss at the strongest point. This is very low for a ribbon mic, and, along with the oxidised ribbon is responsible for a low, noisy output.

Fortunately, we have sourced some very powerful cylindrical N42 neodynium magnets of a suitable size and shape, which are a perfect replacement for the original weak magnet.

With the new magnet the field is increased by a factor of around four, to about 3000-3200 gauss, a much healthier figure which should lead to an increased output and much improved signal-to-noise performance.

Now it’s time to cut a new ribbon, reassemble the microphone, and do some listening tests. In the meantime, we made a rather attractive bracelet from some of the spare magnets.