Townsend Labs Sphere Guts and basic analysis

[kingkorg]

I finally got one to play with in order to get to the bottom of the case. Some interesting stuff, but no rocket science. Very doable for a DIY project, as the software is available for download, and is the heart of the system, great results can be achieved relatively easily and inexpensively.

The mic uses 797 audio CY002 capsule. Once again 797 audio proved to be insanely high quality, reliable, and consistent capsule manufacturer. Just look at the graph, front compared to back frequency responses.

The capsule:

Front to back FR and sensitivity comparison.

As you can see, the frequency response of the mic is not flat. It is corrected in the software, first to flatten it out, then to apply various curves both to front and back to emulate responses of various mics it emulates.

Now, can you just stick this capsule in a random dual out mic and use it as Sphere? No, there is HF attenuation built in the mic which serves as a kind of hardware key. It looks like this, measured by injecting signal into the mic.

This is Sphere's filter compared to typical ''Microphone Parts EQ'' mod for schoeps based circuits. This is SP C1 with two 10k resistors and 1nf cap. Difference bellow 50hz is due to coupling caps in C1.

I have created a CSV file which can be loaded into CurveEQ from Voxengo, just before Sphere plugin so that one can use a microphone with mentioned 797 audio capsule in a flat circuit.
https://app.box.com/s/nq2a3rsi961z8dimr6rra0t5fpm88by8
Here's how the response of the capsule looks like when built in filter is taken out, compared to stock mic.

The headbasket shape plays a role of course. If one decides to go DIY and make their own version, this should be taken into the equation. So u47 shape is the way to go. Here is the response of the mic with and without headbasket.

Wow! Headbasket does play a role! Yup, but how audible it is might be debated. It is clearly measurable.

How about the electronics? Interesting, but i didn't bother to trace the circuit. Filtering curve can be achieved in Schoeps and other type circuits, so why complicate things? The way i see it, it's capsule straight to TLC070 which is used as the first stage. And yes, the mic is dead quiet and has crazy low THD. So this opamp might be something to think about.

Polarisation voltage is about 60v, supplied to the backplate, i believe the topology used for the voltage multiplier is similar to Rode NT1.

The other side:

The signal goes further to the two 33178 which split and balance the signal. Probably similar to Jules' arrangement, but that is just a guess on my side.
https://www.instructables.com/OPA-Based-Alice-Microphones-a-Cardioid-and-a-Figur/

The mic is extremely useful even without modeling capabilities. I've used several versions i had built myself, and for room stereo, M/S miking, is a must for me. The comparison measurements and audio shootout at Audio Test Kitchen show Sphere's Sony C800 model and the original are virtually indistinguishable, seem as matched pairs in measurement graphs. I enjoy using this emulation. This makes sense, as both mics are based around same type of capsule and share similar headbasket shape.

Sony's capsule. Darn, those look similar, and according to some measurements and calculations i've taken they measure remarkably close. But i'm not claiming anything!

2023 Sphere LX Universal Audio Update:
I downloaded and tested the new version of the app and did some measurements of the plugin.

Since the plugin is now protected and no longer available from Townsend they don't need to use EQ within the mic itself as a kind of hardware protection for the new LX variant of the mic. The circuit of the LX mic is now flat.

The corrective curve is now joined with the emulation curves, and for the LX you can just stick the capsule into any flat circuit and use as LX alternative, presuming you have the now protected plugin. The body for the new LX should be now smaller, something like Sound Projects C1 should do fine. If i had to guess, a stock SP C1 would work just fine. That is for single sided version, and if software warnings don't annoy you because just one side is connected.

 

[Tim Campbell]

I'm not sure if you mean they are the same capsule. Sony has no reason to buy capsules from another manufacturer. They are very proud of their  Sony Taiyo division which manufactures their mics.

 

[kingkorg]

Never said they are the same. I wonder if 797 got hold of the blueprints, or just based their on Sony's.

 

[emrr]

Nice work

 

[Gus]

Nice posts.
The most interesting thing for me was the TLC070

 

[kingkorg]

True, and it's performing remarkably well.

 

[kingkorg]

Here's my own version in a MC03 body. Performing and measuring just as the original. Circular PCBs made at JLCpcb. Designed them using easyEDA online.

There is one caveat. Taking working hour prices into consideration in Norway where i live, and time i spent on research, making and designing it, it's price quickly came to more than double of what original costs. So there's that

 

[green-fuzz]

Hello @kingkorg,

I'm a newbie in diy mic making, have just basic knowledge in electronics acquired while building a few comps and preamps. This is the first time i'm diving into something that is not a kit... I really could use a few advices on this particular project.
Thank you for this post that helps a lot. It allowed me to get curious about the schoeps style circuit, for instance (for those like me who know nothing, it is explained here : Schoeps circuit for BM700/800 PCB )

That being said, I have a few questions and i'll ask for your forgiveness as I understand you may surely have more important things to do than holding a newbie's hand. But if you have the time to answer this, it will really make my day.

1/ You mention a ''Microphone Parts EQ'' mod for schoeps. I've been looking on their site but they don't go into details, so I tried to understand by myself. In the following schematic I highlighted a zone i believe could be the LPF. Are R4 and C2 the place where you put the two 10k resistor and 1nF cap in the SP C1 ?



2/You also mention that TLC070 is used as the first stage. For the life of me and despite research (i promise i did, there are so much different answers), i can't be sure of what the first stage is. Is it polarization ? If it is, then i wasn't able to find the original rodes nt1 schematics but the following picture is a nt1a schematics. Did you mean the TLC070 could be used in the same kind of way as U1 (CD40106BC ) for polarization ?



I feel it isn't right as you say "it's capsule straight to TLC070" by which it sounds like you mean "capsule signal straight to TLC070". But then what is the TLC070 for? If i go back to the first schematic of schoeps style circuit, the first thing after the capsule is Q1 which (if I understood well) is a phase splitter. But in the Townsend you seem to think the two 33178 are there to split and balance the signal (I guess one of the for the front membrane, the other one for the back membrane). So i guess I'm completely lost.

3/ Other question about the cpasule polarization. I looked for 60v polarisation schematics and found a MXL 603S schematic. Somebody said this circuit has a 60v polarization... is it the part i higlhighted in blue in the following picture ? If it is, i'll work to understand it, but i don't want to try to understand the wrong thing.



Those are my interrogations... but maybe i'm beating the bush, here : when you made your own version in a MC03 body, did you make it with those components Townsend used ? Or did you make your original Quick Dual Output Mic with two schoeps circuits loaded with LPFs ? If that's the case, which schoeps style circuit would you recommend (there are quite a few variations) and what resistor/capacitor values should I use ? (2x10k resistor and 1nF cap?) And what polarization circuit in order to achieve 60v to the backplate ?

Sorry again for this lengthy post, i know i ask a lot of things and i would completely understand if you didn't have time for that. Anyway, thank you again for this thread. Happy holidays and happy new year if you read this in january... or later !

Denis

 

[Mworthin]

Great analysis, Kingkorg! I missed this the first time around.

 

[kingkorg]

Thank you for your kind words @green-fuzz and happy holidays to you all!

1/ You mention a ''Microphone Parts EQ'' mod for schoeps. I've been looking on their site but they don't go into details, so I tried to understand by myself. In the following schematic I highlighted a zone i believe could be the LPF. Are R4 and C2 the place where you put the two 10k resistor and 1nF cap in the SP C1 ?

MP EQ consists of adding two 10K resistors in series with C5 and C6 in your schematic, and then bypassing them with 1nF capacitor to roll off the highs. You can add a trim pot to adjust the amount of attenuation. Described here:

https://audioimprov.com/AudioImprov/Mics/Entries/2014/2/8_EQ_Pt.3_-_Transformerless_Mics.html
R4 and C2 in your schematic just filter the DC supply to the fet, they don't affect the sound, just get rid of the noise.

2/You also mention that TLC070 is used as the first stage. For the life of me and despite research (i promise i did, there are so much different answers), i can't be sure of what the first stage is. Is it polarization ? If it is, then i wasn't able to find the original rodes nt1 schematics but the following picture is a nt1a schematics. Did you mean the TLC070 could be used in the same kind of way as U1 (CD40106BC ) for polarization ?

Sorry for not being clear. I haven't traced the Sphere's circuit, but it's nothing like Schoeps or Røde. The signal from the capsule goes straight to the TLC070, so the TLC070 is in a sense used as Q1 in your Schoeps schematic. Then the signal goes forther to 33178 which are used as Q2 and Q3. In between there's two 10k and 1nF just like in MP EQ mod.

You can take a look at these two projects to understand how you can use opamps instead of transistors.

https://www.instructables.com/True-Condenser-OPA-Mics/

https://www.instructables.com/OPA-Based-Alice-Microphones-a-Cardioid-and-a-Figur/

3/ Other question about the cpasule polarization. I looked for 60v polarisation schematics and found a MXL 603S schematic. Somebody said this circuit has a 60v polarization... is it the part i higlhighted in blue in the following picture ? If it is, i'll work to understand it, but i don't want to try to understand the wrong thing.

Yes, you are right. It is called "Hartley Oscillator". It is a bit tricky to wrap your head around, and sometimes just won't work for various reasons. Some people consider it to be unreliable as there is some "woodoo" going on. So Røde, Neumann, Sphere and many others decided to use CD40106BC based circuits like in your Røde schematic. More stable as it doesn't rely on inductors. It is the whole upper part of the schematic.

@rogs has some similar brilliant IC based projects, and very well explained.

https://www.opic.jp137.com/index-ldc.html

 

[green-fuzz]

Thank you so much for the reply, the explanations and the links !

I was waaaay off about the lpf location... and almost everything else ! But I guess that comes with learning new things.
With all that info, I now get a clearer picture of what i have to work on. One thing seems to be clear : whatever design i choose, there wil be a 2x10k resistors and 1nF somewhere !
At first glance, the less difficult seems to be the FET route, as it doesn't require me to dive into op-amps madness, but i will read (and try to understand) everything before i choose.

Thanks again, a lot, for taking the time to answer with so much details and links for me to follow. Researching that kind of information by myself is very diffcult because of my lack of knowledge.

 

[kingkorg]

Thank you so much for the reply, the explanations and the links !

I was waaaay off about the lpf location... and almost everything else ! But I guess that comes with learning new things.
With all that info, I now get a clearer picture of what i have to work on. One thing seems to be clear : whatever design i choose, there wil be a 2x10k resistors and 1nF somewhere !
At first glance, the less difficult seems to be the FET route, as it doesn't require me to dive into op-amps madness, but i will read (and try to understand) everything before i choose.

Thanks again, a lot, for taking the time to answer with so much details and links for me to follow. Researching that kind of information by myself is very diffcult because of my lack of knowledge.

Just in case you missed it, depending on how you plan to use the mic, you could use just about any flat response circuit and then apply the EQ curve i provided before the Sphere plug in. There is no real advantage in having the EQ built into the mic.

Acoustics around the capsule are way too important to ignore. I found the typical u47 bodies of chinese origin work best for this project. They pretty much match the original properties. The SM Pro mic body i used here is not ideal solution.

 

[green-fuzz]

Just in case you missed it, depending on how you plan to use the mic, you could use just about any flat response circuit and then apply the EQ curve i provided before the Sphere plug in. There is no real advantage in having the EQ built into the mic.

I did understand that, yes, i even downloaded the eq curve before having any idea of how i would build the microphone. But i think i want to try to have it built in, for it looks to me that it would be very cool to have built a l22 clone that can go directly into the plugin. A bit childish, to be honnest, but i embrace it. Besides, if i make a mistake, or if the eq mod doesn't work as intended and i can't tune it properly, i still can revert to get it out and use the eq curve...
But yourself, in your MC03 build, did you use schoeps style circuit with or without the eq mod ?

 

[green-fuzz]

PS : Those DJJules and OPIC LDC links are great.

 

[green-fuzz]

I don't how, but i didn't see the part of your message regarding the u47 body. Fortunately, i remebered what you said in your first post and how the body impacted the sound. So i imagined i could buy something like this. Yes, I already was going the cheap Aliexpress chinese route ^^ (even if 134 euros is not that cheap for an empty microphone, even with the suspension)

 

[kingkorg]

Yes i used the Schoeps circuit with eq built in. And the exact same body. I have several variants of this mic. That body works best, and it's in my "permanent" room mic setup. The other one is Slate ML1 "clone" but with a tube circuit. Convenient TF badges for cutomers who prefer looking instead of listening.

I just finished producing a song for a band, i can post some raw drum room tracks.

 

[green-fuzz]

Those mics are gorgeous, and not because of the TF branding... ^_^ If you had those good results with it, i think i'm going to try to reproduce them and take the schoeps route first.

I just finished producing a song for a band, i can post some raw drum room tracks.

That would be neat. I have the townsend plugin (tried it with a schoeps mk4, it already sounded great), i'm very curious to listen to the result.

 

[kingkorg]

Here it is. The drum is behind some gobos, so somewhat darker sound. I use these in various M/S configurations. Here i just used the sphere as a stereo mic, and blended in the ''Slate'' for center. Not normalized, used at these exact levels. You don't have to use the Slate plugin if you don't have it.

https://drive.google.com/drive/folders/1iUzAiVJygEMhocRNQRC5OaNC_RbJMcuI?usp=sharing

 

[green-fuzz]

Thanks a lot ! I'm listening to that right now.

 

[green-fuzz]

That's incredible. I've been toying wit the patterns vs stereo image and frequency response, it's crazy. It opens up a whole world. And the mic emulations are something too. Really. Wow. I really have to make myself a pair of those. I want them more now.