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'Optimus' PZM/boundary any good ?

Sorry for this budget-question, but how useful is the boundary ('PZM') mic that Radio Shack has for US$39.99 ?
It's the Optimus #33-3022.

Since someone here will be visiting the US soon I was thinking about asking him to get me a pair.

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=&product%5Fid=33%2D3022

Applications will mostly be for loud sources, like room for drums or guitars.
(Will add the 'usual' PZM-mods)

Any good ? At least usable ? Or just a cheap mic with a bad capsule ?

Thanks,

Peter

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Comments

fromwithin Thu, 02/19/2004 - 13:02

I have an older realistic radio shack pzm a friend let me borrow but dismissed it as a 'cheapie' mic. lately i've been hearing a lot of really good things about them though (glance through the tape op book and you'll see them mentioned quite a bit). in the rob schnapf and tom rothrock interview they mention using it on beck's lead vocal for 'loser'. can't be half bad, im gonna try using mine on my next drum recording session as an overhead and see what i get.

clintrubber Thu, 02/19/2004 - 15:03

from Riversedge:

The Crown is a fabulous mic, but after Peter's inquiry (my RShack PZM is about 15 yrs old) I decided it was worth plugging in, now that I have decent gear. I'll be using the track in the mix with no EQ, not bad for $40. I'm willing to get a new one just to see what the diference is. You never can tell what result you're going to get until you try.

I see now - at first thought you had this present day model (the Optimus #33-3022 at US$39.99). If you happen to get this model as well
it'd be more than interesting to hear how you think it compares to your older RShack-model.
Nice to hear that simple cheaper gear can still have decent uses !

from Teleharmonic:

I understood that the difference between the Radio Shack mics and the Crown mics was not the actual acoustic principle but the quality of componentry,design and manufacture...

OK, could try swapping elements if the results sound like they could use some help.

Thanks everybody,

Peter

sleeper Mon, 02/23/2004 - 19:31

the jensen mod seems a bit out of line... I don't know what particular one they recommend, but the cheapest jensen transformers made are about 50 bucks, most of them with specs for mic output are more like 80 to 100.

I did the mods listed at this web site. In the course of 2 or 3 years I did all of them.
http://www.itrstudio.com/pzm.txt

started with the cable modifications, some improvement, and I still have one with that setup. it can work great with really loud source material, but it's a bit noisy.

later on I did the christopher hicks mod #1, that was seriously better, then I did hicks mod #2 on a third mic. that one rocks and I changed number 2 to the same mic. I'ts loud as s*** now, and it's super quiet as well. I use em all the time. If you can solder a bit it's well worth the time and energy. cost about 15 dollars per mic and that includes a new case for the electronics, a slightly bigger metal plate and an xlr jack for the mics.

One caveat though, if you do the FET circuit (mod#2) you should install a transistor socket for each of the transistors and buy about 2 dollars worth (10 to 20 of them)
substitute until you find the quiet ones. This is pretty much standard procudure for working with transistors. If you look in the tech talk forum you can find out more about this.

Later
Sleeper

clintrubber Tue, 02/24/2004 - 15:47

Tried them this evening and so far a few things poped up: they sound OK but I need to find better positioning (just put them on the floor and hadn't much time to check the sound there). Highs seemed a bit dull, but I'm suspecting the positioning first. The Crown & other info will be studied for better positions and I'll probably have to make me some plexiglass construction.
(I'm actually wondering how exactly people tape them to walls, the lid of a Steinway etc :eek: )

One other thing that I was wondering is about what is the limiting factor in these mics w.r.t. overload (as in their unmodded form, so prior to any Linkwith-mods etc).
Is it the very capsule itself, the FET or just the low battery voltage of 1.5 V ?

I did the mods listed at this web site. In the course of 2 or 3 years I did all of them.

This is great - I just started thinking about of
all those mods & possibilities which mods should I do and there's Sleepers post with info on which mods make a difference. Thanks !

One caveat though, if you do the FET circuit (mod#2) you should install a transistor socket for each of the transistors and buy about 2 dollars worth (10 to 20 of them)

It's a bipolar (PNP) I understood, right ? But OK, will make a selection. Couldn't find much on the BC479 but guess a BC560 will do fine.

Bye / thanks,

Peter

sleeper Tue, 02/24/2004 - 20:28

Peter,
now that I think about it, I think i used a 2n3904 or 2n3906, I remember it being the most common sub for whats on the schematic... but in keeping with the radio shack theme I got them there. at any rate, I still went through at least a half a dozen before I found one that wasn't noisy, (this one was also much louder). I'm a bit obsessed with jfet selection as I built a the hamptone JFET preamp and i'm about to make a couple of 1176 clones

I just changed servers and haven't figured out how to post images yet, but I have a PCB for this.
PM me if you want it and I'll send you the pdfs
Kelly

SME Tue, 03/02/2004 - 18:13

This _is_ the PZM-concept, not ?

No not really. The patent for a "PZM" has the diaphragm parallel (pointing down)to the boundary causing the pressure zone to have uniform pressure versus frequency characteristic in the desired frequency range.
"Boundary" mics have the diaphragm perpendicular to the boundary in order to eliminate comb filtering.
No one can make a PZM exept Crown, the rest are stuck using the boundary method, though it works, its not as effective as a PZM.
Even Crown's PCC (which use the boundary method)mics arent as good as PZMs.

teleharmonic Wed, 03/03/2004 - 05:43

Originally posted by SME:
The patent for a "PZM" has the diaphragm parallel (pointing down)to the boundary causing the pressure zone to have uniform pressure versus frequency characteristic in the desired frequency range.
"Boundary" mics have the diaphragm perpendicular to the boundary in order to eliminate comb filtering.
No one can make a PZM exept Crown, the rest are stuck using the boundary method, though it works, its not as effective as a PZM.

The original Radio Shack mics were proper PZM mics. As I understand it, they licenced the PZM concept from Crown but then Crown pulled the licence and RS started using the boundry design that you are referring to.

I have one of the old RS mics which i have been meaning to mod so it is opened up... the capsule is mounted parrallel in the manner you are describing.

I wonder if the 'boundry ' mic design that you are describing has the capsule mounted 45 degrees to eliminate comb filtering or to eliminate patent infringement!? I don't know, just thinking aloud.

greg

teleharmonic Wed, 03/03/2004 - 05:49

Originally posted by Peter Vermeeren:
Yep, sorry, this was probably quite stupid - but still, not something I would dare to stick on an expensive surface like a piano (or a drummers chest...

I don't think it is a stupid question... People talk about using PZMs on piano a lot. Seriously... anything else that people use to adhere these things that won't leave a layer of goo on a nice piano?

greg

jonyoung Wed, 03/03/2004 - 08:00

Why not a small screw? That's what the keyhole in the top of the plate is for. I don't think a 1/2" #6 screw is going to permenantly ruin the tone or resale value. You can always fill in the hole and burn in new lacquer if you intend to sell it. Any solvent you might use to remove glue residue might do more harm to the finish anyway.

clintrubber Thu, 03/04/2004 - 02:38

Hi,

Interesting points w.r.t. PZM vs boundary etc.

I don't think it is a stupid question... People talk about using PZMs on piano a lot. Seriously... anything else that people use to adhere these things that won't leave a layer of goo on a nice piano?

Why not a small screw? That's what the keyhole in the top of the plate is for. I don't think a 1/2" #6 screw is going to permenantly ruin the tone or resale value. You can always fill in the hole and burn in new lacquer if you intend to sell it. Any solvent you might use to remove glue residue might do more harm to the finish anyway.

That's about the mic-side of things, but I guess
Teleharmonic was more worried about the instrument ?

But keyhole ? Hadn't noticed that - will look tonight, would be convenient.

Bye,

Peter

jonyoung Thu, 03/04/2004 - 06:23

Peter, I was referring to drilling a small hole in the piano lid. I also do cabinet and furniture building, so repairing wood is second nature. I think having residue on the piano from the glue on the tape is harder to fix! MY RS PZM has a keyhole at the top of the plate, maybe the new ones don't. Even so, why not drill a hole there too? :c:

clintrubber Thu, 03/04/2004 - 11:33

Peter, I was referring to drilling a small hole in the piano lid. I also do cabinet and furniture building, so repairing wood is second nature. I think having residue on the piano from the glue on the tape is harder to fix! MY RS PZM has a keyhole at the top of the plate, maybe the new ones don't. Even so, why not drill a hole there too?

Hi Riversedge, sorry for my misunderstanding - I should have realized that at 'resale value' etc (although here in Europe some people tend to ask 'special' prices for the older RadioShack/Tandy PZM's - but that's another story).

I checked my RS-mics (#33-3022) and didn't see any mounting hole - but that will likely change. ;)

Thanks,

Peter

bburch88 Wed, 03/17/2004 - 08:14

PZM/AMT M-40 Piano mic

Have you checked out Applied Mic Technology and their instrument mics? The M-40 is their Piano mic and according their reviews plenty of big name musicians use it on piano as well as many other instruments with a lot of success. I am going to record a 9' grand piano soon and am considering one myself, just want to hear one somewhere first.

BB

clintrubber Thu, 03/25/2004 - 14:50

Have you checked out Applied Mic Technology and their instrument mics?

Hi BB,

Must admit I've never heard of AMT. That model you mentioned a PZM-like mic as well ? My application isn't piano (using it for gtrs, drums etc), maybe others using it for piano ?

Bye,

Peter