Extending Low End on D87
« on: June 21, 2018, 03:14:52 PM »
Love my D87, but I'd really like to extend the low end response. Would changing C5 in Dany's circuit from .033uf to something larger do the trick? Or is there another cap here that handles LF attenuation? 

Tim Campbell

Re: Extending Low End on D87
« Reply #1 on: June 22, 2018, 05:52:20 AM »
What capsule are you using?
Do you mean low end response or proximity effect?
Try using your mic in fig 8 and see if this is more the sound you mean.

Re: Extending Low End on D87
« Reply #2 on: June 22, 2018, 11:30:18 AM »
Thanks Tim. Good question. I hate to seem cagey, but it's actually a prototype from a well-respected capsule maker that I can't say much about since it's not available quite yet. I have two, one dual sided and one single sided and they both sound the same. It could be the capsule and I'm emailing the designer about that now.

I thought it was the capsule at first, too, but when I saw the thread about the thin sounding U87ai (https://groupdiy.com/index.php?topic=65743.0) and the analysis Ruud made of how the LF changes with C104 in the ai (and C5 in the i), it made me think that maybe with the 33n cap at C5, I'm choking out the LF too soon. So, I was wondering if taking C5 to 100nf or even 220nf would help.

I'm getting proximity effect, but it doesn't really fill out the low end as much as I'd like.

Tim Campbell

Re: Extending Low End on D87 New
« Reply #3 on: June 22, 2018, 12:24:41 PM »
Almost always when people speak of bass response they mean when they are speaking or singing in close proximity to the microphone which in reality relates to proximity effect.

Real bass response is determined by the capsule and can only be affected by some form of equalization.  A cut or boosting circuit.
If there is no additional eq then the capsule is the limiting factor.

« Last Edit: June 22, 2018, 01:40:09 PM by Tim Campbell »


Re: Extending Low End on D87
« Reply #4 on: June 22, 2018, 12:53:30 PM »
The low frequency response of the U87 was intentionally limited.
By increasing the value of a capacitor in the feedback loop, you can extend the LF response.
(I did it with my U87's and it works perfectly.)
There is a solution for every problem!



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