BM800 lottery...

[rogs]

Many of us have played the 'BM800 lottery' when it comes to buying cheap mics to act as donor bodies.
Sometimes you'll get a FETless electret capsule (TSB165A style) with a 2SK596 and fully balanced output electronics..
Sometimes it's only a cheap 9mm electret 'dressed up' to look like a 165A style capsule. And the electronics are simple and unbalanced....

My latest acquisition has hit a new low ...THIS VERSION not only has a cheap noisy 9mm omni capsule, but is constructed completely of PLASTIC (except for the head basket grill! ). That despite advertising 'blurb' that says it's cardioid - and is made of metal!

Might be OK to use with a better quality electret with a built in FET - but for anything Hi-Z at all ? -- forget it!

Just a heads up.... The 'BM800 lottery' seems to be getting even more unpredictable!

 

[Khron]

Wow, that is indeed a new low...

A couple weeks ago i grabbed a used Neewer NW700 for ~$20 or so (with metal shockmount), just for s**ts and giggles, for a hacked/together "U87" (with a slightly modded BM800 board). Headbasket only had the outside coarse mesh, but an internal foam "pop filter" as well, surrounding a little 9.5mm(?) electret capsule, glued inside a foam suspension inside the capsule mount.

At least the construction's all metal though, albeit it seems to joyfully pick up 50Hz (on this side of the pond) when placed right next to a light fixture. I discovered that when using it as a (high-ish) drum overhead when recording my girlfriend's band's rehearsal a couple weeks ago, but oh well... Nothing a narrow EQ notch couldn't quickly fix (just the 50Hz hum, no other harmonics / buzz noticed). I had taken the liberty to sand down the ends of the body tube, to try to ensure good ground contact.

Moral? Maybe buy used?

 

[rogs]

At least the construction's all metal though, albeit it seems to joyfully pick up 50Hz (on this side of the pond) when placed right next to a light fixture. I discovered that when using it as a (high-ish) drum overhead when recording my girlfriend's band's rehearsal a couple weeks ago, but oh well... Nothing a narrow EQ notch couldn't quickly fix (just the 50Hz hum, no other harmonics / buzz noticed). I had taken the liberty to sand down the ends of the body tube, to try to ensure good ground contact.

I've had that '50Hz only' hum when using an NW700 head basket - which came fitted with single layer mesh.
I added a second layer of mesh using some 'Isopon' car repair aluminium mesh. Killed the hum stone dead.

I wondered if it would work, being aluminium, but once I realised that I was dealing with an electric field - rather than a magnetic one - that explained why the aluminium was fine. The electric field also explained why the hum was almost 'pure' 50Hz ...
Sorry Mr. Faraday, my physics is a bit rusty !

 

[k brown]

I do a comprimise that works fine - All the '700s I've bought had double mesh, and I removed the inner mesh on the front only, leaving the extra shielding on the back where it counts most. Quiet.

 

[MicMaven]

Mssrs. Brown and Rogs - I enjoyed reading your comments on headbaskets and adding more mesh. Interesting observation concerning electrical versus magnetic noise ... this is a huge aspect of antenna design, so it makes sense in this application, as well.

Would a bit of brass wire mesh would be effective and easy enough to mold and add inside the headbasket? If so, can you suggest an appropriate size mesh for the job? I am thinking 40 or 60 size mesh might be appropriate.

THANKS for any guidance you can provide. James -K8JHR

 

[rogs]

Mssrs. Brown and Rogs - I enjoyed reading your comments on headbaskets and adding more mesh. Interesting observation concerning electrical versus magnetic noise ... this is a huge aspect of antenna design, so it makes sense in this application, as well.

Would a bit of brass wire mesh would be effective and easy enough to mold and add inside the headbasket? If so, can you suggest an appropriate size mesh for the job? I am thinking 40 or 60 size mesh might be appropriate.

THANKS for any guidance you can provide. James -K8JHR

I'm sure brass mesh would be fine...
As it's an electric field even aluminium works OK.... I simply took a piece of THIS type of mesh I had lying around just to see how well it would work, and it cured the problem... so I looked no further!
I'm not sure what the mesh size is though? You might get an idea from the relative size of the primary head basket mesh in the attached photos.
It doesn't seem to have affected the overall sound very much, as far as I can tell...
I haven't tried K. Brown's single sided option yet......

 

[Tubetec]

Brass might react with the other metals and tarnish over time ,
A standard household metal sieve is as handy source for stainless mesh ,only costs a few euros .

There seems to be a load of these becoming available second hand after lockdown , about 20 bucks , sometimes they come with a 48v psu ,
I think its the Neewer ,
It seems the BM-800 with the large PCB is the one to lookout for , any chance of a close up pic of the pcb ?
Is it possible to derive bias for standard LDC capsules off the phantom power ?

 

[rogs]

Is it possible to derive bias for standard LDC capsules off the phantom power ?

I tried out THIS CIRCUITRY - which includes phantom powered polarisation for the LDC - and have been very pleased with the results.
It's very quiet - and the amp is very linear - and with low distortion.
The only shortcoming is that the DC allocation is not symmetrical, so it's not really suitable for use with mic preamps that use transformer inputs...

 

[MicMaven]

Brass might react with the other metals and tarnish over time ,
A standard household metal sieve is as handy source for stainless mesh ,only costs a few euros .

Ah ... yes. The old problem of mixing metals. I suppose I COULD spray the brass with a clear coat of Verathane or something ... but that would be obsessing - surely the aluminum or stainless mesh you guys mention is far more practical. I think I will visit a couple of local Dollar Stores looking for some stainless mesh strainers.

I appreciate the photos - the one showing both layers of mesh is particularly well done. (photography is another of my hobbies, so I appreciate a good shot of ANYthing!) THANKS James -K8JHR