EV RE50N/D-B mic + Olympus LS-10 recorder = hollow, tinny sound

July 26, 2009 7:03 PM

Recordings made using an ElectroVoice RE50N/D-B microphone with my Olympus LS-10 Linear PCM Recorder sound quiet, tinny and hollow. Why could this be?

I have an Olympus LS-10 Linear PCM Recorder and a ElectroVoice RE50N/D-B microphone which I use to record interviews for a show I do that airs on a college radio station. When I transfer the audio from the recorder to my MacBook, the audio sounds hollow, tinny and very quiet. However, the strange thing is, if I shift the balance on the internal speakers to the left or right (not centered), it sounds much much better. Recordings made with the Olympus LS-10's internal microphone (without the EV mic) sound just fine. This same problem existed with another EV mic that I used, so I don't think it's the particular mic I'm using now.

For a while I thought this could be a problem with my MacBook, but then I played one of the interviews on the air and it sounded the same. The audio sounds fine on some computers though. So, basically, I'm at a total loss. Anyone have anything like this happen before or have any thoughts as to why it could be happening? Thanks!!

posted by BugsPotter to technology (9 comments total)

Transom published a review of this recorder last year. It's generally positive, but it says of your mic:

"Low-output mics, like the RE50, may not quite give as much level as is ideal, but the input gain is just high enough, and the noise floor is just low enough that credible recordings can be made with most microphones. Better quality is achieved with higher-output mics, such as self-powered condensers, but it's a real advantage that the input gain is sufficient to get decent results with a variety of mics."

So, try a higher output mic. Many of the smaller solid state recorders have this problem, it's incredibly frustrating. You might need to borrow and test few different mics before you find one that's a good fit.
posted by embrangled at 7:19 PM on July 26

Hmm, but what I find really strange is the issue of shifting the balance on the audio away from center to left or right and having it sound pretty much fine. I can't figure out why that would make things work. Similarly, the sound is just fine on some computers. Makes me suspect that it's not necessarily the mic + recorder problem, but something else. But I'm willing to be convinced otherwise since I really don't know.
posted by BugsPotter at 7:37 PM on July 26

Sounds to me like something is out of phase.
posted by intermod at 8:06 PM on July 26

I am thinking that it might be the adapter that you are using to connect the mic to the recorder. It is an XLR to 1/8" adapter, correct?

If the adapter is wired "straight through" the recorder would be getting a pair of signals 180 degrees out of phase - this could explain why it sounds tinny when you are listening to both signals, but fine on either side (the out of phase signals cancel each other out when played back in "stereo")

If, for example, you took a standard XLR-1/4" TRS cable and used a 1/4 to 1/8 adapter to connect it to your recorder, you would end up with the above scenario.

You need to make sure that you have a cable like this - it is sending the same signal to the left and right sides of the 1/8" adapter.
posted by davey_darling at 8:10 PM on July 26

This is the exact cable that I have. Does it look right? Wow, I hope that's not it because I'll feel mighty dumb. But it'll be a relief if it is!
posted by BugsPotter at 9:31 PM on July 26

I think davey_darling is exactly right. Your mic is putting out a balanced signal, which you're converting to 1/8" TRS, but your recorder is expecting unbalanced stereo on that connector (as evidenced by the existence of a L/R balance control, which wouldn't exist if the input were mono).

The easy solution would be to either push the balance all the way L (I've always been taught that when you record mono on a stereo device, put it on the L channel), or you could modify the adapter you have so that the connection going to the R side of the 1/8" TRS is floating. It's probably easiest to do this at the XLR end of the cable.

The better/proper solution would be to get an adapter or field mixer that has a balun in it, so that you convert the balanced low-Z mic connection to the unbalanced high-Z that your recorder seems to expect. I have a Rolls MX124 that I use for this purpose and really like, but you may find it clunky. (I do most of my recording into a laptop so it just travels in the computer bag.)
posted by Kadin2048 at 10:22 PM on July 26

Well that's a kick in the teeth!
I should clarify that the L/R balance control I was talking about was when playing back using the internal speakers on my MacBook. The recorder itself doesn't have a L/R balance, and I just looked it up and reviews indicate that the LS-10 can't record in mono, only stereo. Is there any other solution I can employ? Elegant or not elegant doesn't matter that much, as long as it works.
Thanks everyone for the help so far! This is all way beyond my capabilities.
posted by BugsPotter at 10:49 PM on July 26

the LS-10 can't record in mono, only stereo

Assuming you're recording in MP3 mode, this shouldn't be as bad as it would be in PCM; silence compresses fairly well, so it shouldn't (I wouldn't think, I haven't tested this) double your data rate like it would seem to on first glance.

Recording from a single mic using a stereo recorder is not an uncommon situation. The easiest thing to do is just record on to the L channel and leave the R silent, and then in post drop the empty channel and re-save it as a mono file. That's probably what I'd do in your position.

Alternately, and this is what I'd do only if you're recording in PCM and thus are wasting bits recording an empty channel, you could do what I used to do when recording for video: get a field mixer and run the same mic input out both the L and R outputs, but keep the R channel a few dB lower than the L. Some people do 3, others do 6, it depends on the environment. That way, you'll have a "cool" channel with some additional headroom, in case your subject gets really excited and starts SHOUTING RIGHT INTO THE MICROPHONE during the interview.

How exactly you'd set that up would depend on the field mixer you're using; on my Rolls, you do it just by adjusting the L/R balance control on the mic's input over to the L, and then adjusting the gain until the L channel is where you want it, leaving the R cool. (If you wanted to DIY or are on a budget, you could probably rig up a cable to do this with some resistors, but if you can afford a field mixer I think it's a great investment. I've never regretted buying mine even though I only use it occasionally.)

But, again, I'd only fuss around with doing that if you're recording in uncompressed PCM mode.
posted by Kadin2048 at 11:08 PM on July 26

Also, if you want the quickest/dirtiest/cheapest solution, here's a guide to wiring audio cables that details how to interconnect balanced and unbalanced equipment.

Basically, you can open up the shell of the XLR connector on the cable you already have, and disconnect (by desoldering the wire) pin 3. Just leave it floating, and make sure it's not going to short out to anything (use electrical tape around it to test before you cut the wire).

What you should end up with, provided the cable was wired in the normal way (pin 3 to ring, pin 2 to tip, IIRC — check this with a multimeter before you start to be sure!), is a cable that gives you an unbalanced signal on the L channel of your recorder's stereo input.

This is far from optimal, but I think it ought to work. I've done similar stuff in a pinch. You may get hum issues, although it might be manageable if you keep your mic cable short.
posted by Kadin2048 at 11:37 PM on July 26