Transound TSB2555 as omni?
« on: January 17, 2020, 06:31:14 AM »
Can the TSB2555 be made omni by closing the backplate holes? Has anybody here tried this before, if so how did it affect the sound of the capsule?


xeawr

Re: Transound TSB2555 as omni?
« Reply #1 on: January 17, 2020, 10:37:32 AM »
Hi, I'm just trying to help a little, but I must say I have very limited experience in microphone building.

theoretically any unidirectional capsule can be transformed into an omni if the corresponding holes, usually in the back, are being closed. As far as I know, from the occasional chat with some well known microphone manufacturers, this is a rather futile enterprise, because as the capsule/microphone changes to omni, its sound usually doesn't change for the better (there are more factors to alter when designing an omni capsule - so I've been told). The only microphone that I know, that will work and sound good this way is the Shure KSM141.

I've considered this "closing the holes idea" with some (mid priced) externally polarized SDC mics. I know this all doesn't really help, as you wanted to know what it sounds like. All I can say is: probably not very useful. Maybe you can "emulate" the sound of it by grabbing a CM3 (not saying the CM3 use this capsule  ;)) or the like and wrap some masking tape around the vents?

Good luck!

EmRR

Re: Transound TSB2555 as omni?
« Reply #2 on: January 17, 2020, 11:07:49 AM »
There's a switchable Shoeps omni/cardioid as well.  Definitely would seem a balancing act. 
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

Re: Transound TSB2555 as omni?
« Reply #3 on: January 17, 2020, 02:01:07 PM »
Hi, I'm just trying to help a little, but I must say I have very limited experience in microphone building.

theoretically any unidirectional capsule can be transformed into an omni if the corresponding holes, usually in the back, are being closed. As far as I know, from the occasional chat with some well known microphone manufacturers, this is a rather futile enterprise, because as the capsule/microphone changes to omni, its sound usually doesn't change for the better (there are more factors to alter when designing an omni capsule - so I've been told). The only microphone that I know, that will work and sound good this way is the Shure KSM141.

I've considered this "closing the holes idea" with some (mid priced) externally polarized SDC mics. I know this all doesn't really help, as you wanted to know what it sounds like. All I can say is: probably not very useful. Maybe you can "emulate" the sound of it by grabbing a CM3 (not saying the CM3 use this capsule  ;)) or the like and wrap some masking tape around the vents?

Good luck!
I've got a couple iSK Pearls which use TSB2555s, I just haven't tried it yet, since I lack the equipment to do measurements. I suppose I could just tape the vents up and record a source with one taped and one regular and use a spectral analyzer plug in to see the difference.

It's just really easy to get a hold of this capsule, the iSK Pearls are only $30 a piece, so if it sounds bad no harm done.
« Last Edit: January 17, 2020, 06:57:50 PM by Icantthinkofaname »

xeawr

Re: Transound TSB2555 as omni?
« Reply #4 on: January 17, 2020, 07:57:00 PM »
Sounds like a plan, additionally you could also record a sine sweep with each mic to give you sort of a frequency response (difference). Anyway let me know how it goes (and sounds).

By the way, you could also just try to stick one of the many omni capsules in there. Would probably be less hassle than modifying the capsule  :)
« Last Edit: January 18, 2020, 02:03:37 PM by xeawr »

Re: Transound TSB2555 as omni?
« Reply #5 on: January 18, 2020, 03:57:34 AM »
Sounds like a plan, additionally you could also record a sine sweep with each mic to give you sort of a frequency response (difference). Anyway let me know how it goes (and sounds).

By the way, you could also just try to stick one of the many omni capsules in there. Would probably be less hassle modifying the capsule  :)
I'm not sure where to source decent omni capsules other than Mic-Parts (which is pretty expensive), electret or otherwise.

Gus

Re: Transound TSB2555 as omni?
« Reply #6 on: January 18, 2020, 08:33:19 AM »



There is the Sony capsule

Re: Transound TSB2555 as omni?
« Reply #7 on: January 24, 2020, 07:00:02 AM »
I actually did a tiny bit of BEM to look into this. Couldn't get the model lined up though and I didn't have a clear approach to actually model the cardioid behavior.

Anyway I did notice some stuff which might be useful to this discussion: The shading of the capsule enclosure produces something like a "3 dB point" towards a hyper-cardioid  as high as around 9 kHz.

I guess this means you'd get a pretty decent omni response below that frequency at least.

Cheers!


Re: Transound TSB2555 as omni?
« Reply #8 on: March 10, 2020, 08:44:27 PM »
I have a measurement mic coming, I'll try taping the vents on when and measuring it.

Re: Transound TSB2555 as omni?
« Reply #9 on: March 13, 2020, 03:50:43 PM »
I look forward to hearing about your measurements. I have tried doing this with a TSB 165 and to my ears it did not sound good, but I never tried measuring it. Btw micbooster sell the primo em23 which is an excellent FETless capsule... I'm a prolific mic building hobbyist but no guru. However Scott Wurcer is a mic guru and he loves it (see his articles on the linear audio website).  By the way what sony capsule is that?


Re: Transound TSB2555 as omni?
« Reply #10 on: March 13, 2020, 03:58:33 PM »
Also see JLI-120 AO-T on JLI electronics website. You can unscrew the FET and use your own or just use theirs. In practice I found soldering directly to the back cspsule terminal difficult, it is much easier to use their FET. The capsule has an internal 2k2 source resistor, so it's like a panasonic wm61a with a built in linkwitz mod.

Marik

Re: Transound TSB2555 as omni?
« Reply #11 on: April 03, 2020, 12:59:43 AM »
Can the TSB2555 be made omni by closing the backplate holes? Has anybody here tried this before, if so how did it affect the sound of the capsule?

While you can easily do it most likely that won't sound right. That is, for correct operation and extended HF response of the true pressure operation (which a single diaphragm omni essentially is) it will need rely rather on stiffness controlled operation, as opposed to resistance controlled cardioid pressure difference operation. In other words, the diaphragm will need to be tensioned quite a bit higher than that for cardioid operation to get desired stiffness and HF extension. The huge problem with such large diaphragm as 2555 is it won't hold the tension and the diaphragm will be quite unstable. That's the main reason you probably won't find a true pressure high quality recording LD omni capsules. All measurement 1" diaphragm mics from Gefell, B&K, and such have upper frequency limit of some 8kHz. Those usually used for noise measurements in very limited frequency range.

Sure, we have LD Sony capsule, but the stiffness in omni mode is achieved by a huge amount of acoustical resistance. Of course, at the price of very low sensitivity (=high noise) and high polarization voltage.

Another issue is its polar pattern. Since the directivity is a function of physical size the 1" omni capsule will turn cardioid on very low frequencies--at some 3-4kHz. About the same physics behind it as speakers with 1" tweeters will have very narrow sweet spot.

IOW, while it will work, because of physics laws the performance will be by far compromised. Here we really need a smaller diaphragm capsule, with optimized membrane tuning, or having enough resistance controlled portion for its linear HF response.

Best, M
Samar Audio & Microphone Design

www.samaraudiodesign.com

The Art of Ribbon Microphones


 

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