The Xaudia Blog

21-08-2012

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

A typical day at the office

RCA 77DX under test at the Xaudia microphone workshop.
I think I always wanted my bench to look like the inside of the Tardis. Signal generators, oscilloscope, LCM meter, frequency counters, distortion meter, microohm meter, home built impedance bridge, and lots of other gadgets. And an RCA 77DX, of course! 
20-08-2012

Straightening a dented mic grill

Here’s a rather deformed grill from a Beyer ribbon mic…

And here’s how we straighten it using a doming block….

Simply pick the nearest radius curve from the block, and push out the dents with a suitable doming ball….

Voila! The end result…

🙂

11-08-2012

Rogue Cadenzas

I have come across a couple of Cadenza ribbon microphones recently that are not what they seem.

The microphones came from different sources, but both had been modified in the same way. The mods were performed long enough ago that the foam had started to disintegrate.

In both cases the ribbon element has been replaced by a dynamic element. and the mic stuffed with pink foam. Both mics are painted black with a silver top, and in both cases the stand adapter is fixed to the microphone rather than being removable.

Rogue Cadenza with dynamic element

There are clearly a few of these floating around. The stand modification looks well done, and I suppose it is just about possible that this was done at the factory, perhaps as a budget alternative to the ribbon mics, although I have not seen any documents to support that.

So, look out when buying old microphones – what you see is not always what you get.
Caveat Emptor!

31-07-2012

MOTM Mystery 74B clone

It is said that imitation is the sincerest form of flattery. If that’s true then the RCA 74b junior ribbon was one of the most flattered microphones ever made!

In the middle is a ‘real’ RCA 74b and on the right is a 74b made under license in Italy by Magneti Marelli. But what’s that on the left? It’s our microphone of the month, and I don’t know what it is.*
When I first saw this I thought it must be another rebadged or licensed 74b. The outer dimensions are almost identical to the real thing, and it even has a red ‘meatball’ badge, although this time with some unidentified Eastern-looking symbols – perhaps from somewhere in South East Asia.** It even has a good copy of the swivel stand mount.
Inside the 74b clone
But inside the mic there are some differences. The ribbon has similar dimensions, but the magnet assembly is quite different, with two large, strong horseshoe magnets providing the field through a pair of U-shaped pole pieces.

Rear view with horseshoe magnets
In a ‘real’ RCA 74b, the magnets are at the front and bevelled, with a rectangular frame at the rear.
‘real’ RCA 74b microphones inside
In the photos above the transformer is a replacement. The original transformer, below, was faulty, probably due to insulation breakdown. Again, the marking on the transformer looks very Eastern in style, and appeared to have been written with a brush, in eastern style.
Perhaps the oddest thing about this microphone is that it has been shot! There is a pellet embedded in the side of the mic. Perhaps it was used as target practice. Or just maybe it was in use at a radio station in the last days of Saigon….
*Thanks to John Gooding!
** I have tried to identify these but no luck yet!


—————-

Update, 13 August 2012


A couple of readers have sent in messages about the provenance of this microphone….


“My friends here in Thailand says the symbol is almost definately Chinese. It is certainly not Thai, Vietnamese or Cambodian. By most stuff here has been made in China since China started making things, so your Saigon theory is still the best.” James Browne, Hungry Ghosts


“Hi Stewart. Sent picture to my factory in H.K, the marking is definitely Chinese,” Andy Hearn, ECM


—————
Update, 15 June 2022 (ten years later…)

Thanks to Adam Pan from Taiwan for providing this additional information and photographs.
“The first photo left one ribbon mic is make by Shanghai Microphone Factory in 1940’s. 
After a long time looking for some China made microphone. when I move to live in Shanghai China from 2001, I found two ribbon microphones in China, one is the same as yours, the logo is the word “Ding”(鼎) in chinese, that is “tripod” the meaning is “one word is as heavy as nine tripods”. Reminder to “keep your word”. And the other one’s logo is “He-Ping”(和平)，That meaning is “Peace”. 
A few years ago, I helped Superlux develop some products, and I met an older engineer who is retired, He was involved in the manufacture of Type 74 microphones at the Shanghai Microphone Factory.”

15-07-2012

Hexapup hexaphonic pickups now available.

One of the great things about being a micro-business is that you can act quickly! There is no management structure, no liaising with a marketing or accounts departments – we don’t have them! And best of all, no office politics! This means that if we have a good idea, or even a stupid one, we can do it straight away.
Hexapup in a Gretsch-style ‘toaster’ cover

Last month we made a stereo guitar pickup prototype, and it was fairly clear from our customers and comments on forums that a few people might want one. So now, six weeks later, we have a ‘production’ version in a humbucker sized* can – the Hexapup!

Hexapup – hexaphonic guitar pickup

Hexapup guitar pickup

The hexapup is actually made of six small pickups, and can be wired for mono, stereo or hexaphonic output

Mono
When wired as a conventional mono pickup, the hexapup has a bright single coil tone. But it also has hum rejection (humbucking) properties because the coils on one side are reverse wound, with reverse magnet polarity.

Hexapup – serial number 002 with 43AWG wire



Stereo
There are two obvious ways for stereo wiring. Either bottom-and-top, or alternating strings. Put another way, the lowest three strings can be sent to one output, and the highest to the other, so power chords could have one sound, and solos another. Or, the E, D and B strings sent to the left, and A, G & e to the right. This makes for nice stereo width, and is great for multi-tracking chords, and chorus type effects. I have my guitar wired this way!

Hexapup being mounted to a customer’s guitar



Hexaphonic
Each coil can be given its own output, volume and tone control which, with series / parallel and phase options gives a staggering number of combinations. Each string can be sent to a different distortion or delay to  get strange new sounds, and could even be auto-tuned or pitch shifted separately – that might be weird. With six outputs, imagination is the only limit!

We currently have some big introductory discounts on the first production run, so please get in touch if you want one.

I’ll be writing a bit more about the technical specs in a couple of days, so stay tuned.

* Actually a little deeper than a normal humbucker, but most guitars have plenty of space.

28-06-2012

MOTM: Oktava ML52 (Spot the Difference)

I have a soft spot for Oktava microphones. They look cool, come from Russia, are fairly priced, and everyone has fun modifying them. That’s enough to make the ML52 microphone of the month for June.

Oktava have a long tradition of ribbon microphones dating back (at least) to the ML11 in the 1950s. The ML52 is one of the most recent models, with a slightly odd double-ribbon motor assembly. I had some in to service recently, and noticed something odd….

Here are two ML52s – can you see any differences?

The answer is “Yes”. The bottom mic has a logo and serial number, and an XLR that is machined into the bottom bell. It also has slotted screws rather than pozidrive. The grill spacing is also slightly different, but that is harder to see on the photos.

Under the grill, both have twin ribbons, but the motor assemblies are totally different. The one on the left is the same as the one found in Avantone microphones, the right hand one looks typically Russian, with silver contacts and big baffles to protect the ribbons.

The transformers are also very different. The right hand one is the mic with the logo, and it uses a toroidal transformer. The left hand transformer can looks typical of the China mics, and is connected to a (pointless) circuit board.

Sound-wise, the mics actually sound quite similar, which goes to show just how much the body and grill influence the sound of these mics. The Chinese one has a longer ribbon and stronger (neodynium) magnets, and has slightly stronger output.

Response plot for Russian (Red) and Chinese (Blue) ML52 mics

I don’t want to say the word “fake”, but  if forced to jump, the obvious conclusion would be that one mic is from the Oktava factory in Tula, Russia, and the other is made in China – either under license, or perhaps not.  🙁
27-06-2012

Beyer ribbon microphone transformer

This transformer came out of a faulty Beyerdynamic M260.

Beyerdynamic M260 transformer

The mic was giving no output, but the ribbon was OK. The problem turned out to be a short in the primary winding, which gave an excuse to take a peek inside.

I was surprised how roughly the primary coil is wound – it really looks like it has been done by hand. Perhaps it is to minimise parasitic capacitance, although that is not usually such a big problem with low impedance windings as they only have a few turns.

In this case the short was located and the original transformer was repaired, but that is not always possible, and sometimes a rewind or replacement is required.

Some of the Beyerdynamic  ribbon mics, such as the M500 and some models of M260 have a ‘built in’ high pass filter. This is done by manipulating the transformer inductance, allowing some of the bass frequencies to pass to ground. Some people like this, but others (including myself) prefer a full frequency response.

Xaudia B-series (top) and Beyer transformer (below)

Xaudia now produce replacement full-range transformers for repair or upgrade of Beyer and B&O mics. The B-series transformers use a larger core than the originals, but still fit neatly inside the mic. They can be supplied in any desired ratio, and have lower DCR specs than the originals, which gives better noise performance too.
21-06-2012

The Beeb Reslo

Xaudia have a limited number of Reslo RB microphones for sale, with upgrades and modifications inspired by the BBC. We call these “The Beeb.”

‘The Beeb’.  Modified Reslo microphones by Xaudia

Back in the 1950s and 60s, the BBC published a number of R&D reports on ribbon microphones. Here’s what they had to say about the humble Reslo RB…
It seemed possible, that a few simple modifications might result in an appreciable improvement in response…”

They recommended a number of modifications, which included….

  • Swapping the transformer to one with higher primary inductance,
  • Conversion from 50 ohm to 300 ohm output,
  • Fitting a more open interior mesh,
  • Removing the cloth around the ribbon motor,
  • And reversing the motor assembly so that the ribbon element is at the front.

Xaudia have recreated these mods and added a few more of our own. “The Beeb” has an XLR output, and new 1.8 micrometer ribbon. We also ultrasonically clean these before re-assembly to remove 50 years of gunk. And we put a (removable) sticker on them, so you know that they are 300 ohm mics.

Reslos with XLR upgrade

We have a very limited number of these mics for sale. Alternatively we can upgrade your own mic to these specifications. Please get in touch for details.