[McMadface]

Hi @McMadface - It's awesome that you're trying this, because there are limitations to the dynamic mics that come with most of these 711 couplers.

These couplers are designed with very specific volumes (to act as Helmholtz resonators) and resistive gaps to those volumes. Anything else you add in there that changes the volume or impedance, i.e., gaps around or possibly even within the mic capsule, could screw with the frequency response. I suspect that by not taking the cap off the mic, you've created an extra little volume in there, which could well be shifting the energy from those particular frequencies.

@castleofargh was brave enough to drill out his coupler so his mic would fit. I presume that is what you've done too? I think that should work as long as you're careful to seal the gaps around the little fins on the mic cap. (One possible concern is that you don't know how well the mic capsule itself is sealed inside the mic cap - you might have a gap or cavity there you'd never know about.) My plan B was to remove the mic cap, then very carefully remove the mic capsule from the cap using heavy-duty tin snips, and then seal the mic capsule tight against the coupler opening (use a very thin, flat washer in front of this if you have a 4 mm mic capsule). Two-part epoxy works well for this, and if you put PTFE tape or wax spray in the threads first, you can unscrew the whole thing later and you won't have permanently glued your coupler. You just want to get a good seal with the mic flush against the coupler opening with no air gaps.

The UMIK-1, Sonarworks XREF20, Behringer ECM8000 and Dayton EMM-6 all look identical on the outside. They also all look identical on the inside. Some of these brands come with compensation curves and some don't. I suspect branding and compensation curves are the only difference. I have found the Sonarworks XREF20 and the Earthworks M23 mics have lower THD than the other mics I've tried, but that (XREF20, at least) could still be down to unit variation. I suspect your mic is most likely good and you just need to seal it properly in the coupler, making sure to create no new cavities, gaps or openings.

P.S. I see that while I was typing @castleofargh just said basically the same thing I did in way fewer words

Hey, thanks for the response. The UMIK-1 is 12 mm in diameter as is the inside of the coupler, so it slides right in nearly perfectly once you get the tip of the mic past the silicone seal ring. I think I'll try out a washer first. Hot glue next. And then take off the cap if my measurements still seem to not be lining up.

 

[csglinux]

Hey, thanks for the response. The UMIK-1 is 12 mm in diameter as is the inside of the coupler, so it slides right in nearly perfectly once you get the tip of the mic past the silicone seal ring. I think I'll try out a washer first. Hot glue next. And then take off the cap if my measurements still seem to not be lining up.

Sounds like a good plan. Even mounting putty might be a good place to start (I don't know how reversable a hot melt-glue might be, and condenser mics can be damaged by heat, so be careful).

What I meant about the mic size was the actual mic capsule inside the mic cap. These types of mic all use 4 mm capsules, so if you go down the route of destroying the cap (you might try just pushing out the mic capsule instead, but there's a risk of damaging it) then you'll need some kind of washer in the coupler opening.

 

[McMadface]

Sounds like a good plan. Even mounting putty might be a good place to start (I don't know how reversable a hot melt-glue might be, and condenser mics can be damaged by heat, so be careful).

What I meant about the mic size was the actual mic capsule inside the mic cap. These types of mic all use 4 mm capsules, so if you go down the route of destroying the cap (you might try just pushing out the mic capsule instead, but there's a risk of damaging it) then you'll need some kind of washer in the coupler opening.

Thanks for the heads up about the heat. I'll try to find something else that can fill the gaps but then be removed fairly easily. Maybe crazy glue? Play-Doh? Hmm. I'll have to think about it.

 

[McMadface]

The opening for the mic on the UMIK-1 is 5 mm. I found a 5 mm ID x 12 mm OD x 0.5 mm washer that should work perfectly for this application, if it works at all. It comes in a 100 pack. If you or @castleofargh want some, let me know and I'll mail them out.

 

[csglinux]

The opening for the mic on the UMIK-1 is 5 mm. I found a 5 mm ID x 12 mm OD x 0.5 mm washer that should work perfectly for this application, if it works at all. It comes in a 100 pack. If you or @castleofargh want some, let me know and I'll mail them out.

Thanks buddy! They could come in useful for others. Right now I'm on a mission to destroy as many mics as I can with my pipe cutter

 

[McMadface]

So, while waiting for the flat washers to arrive, I decided to try out some other materials to see if I was on the right track. I used 3 layers of a commercially available self-adhesive plastic film (Scotch tape) to cut a disc that covered up the cutouts on the UMIK-1. The results are far more in line with other measurements out there. Red is with the tape disc and blue is without. There's still some more work to be done but I think I'm on the right track. I'm thinking that the Scotch tape just doesn't have the rigidity needed to fully stop the energy bleed. Hopefully the steel washers don't bork the measurements by being too thick. Thanks for your help, guys.

 

[castleofargh]

glad to see it was indeed "that simple".
washers have the benefit of not shaking of flexing much once well stuck between the mic and coupler, but getting a tight seal might be tricky with that alone. as for the thickness, it worries me as a principle, but I don't really know how much impact that can have beside the basic shift in resonance. but in that regard we have a hard time finding 3 people to agree on where to place the IEMs anyway ^_^.

 

[CoiL]

@McMadface , @castleofargh , can You post picture about that issue and spacer?

 

[McMadface]

@McMadface , @castleofargh , can You post picture about that issue and spacer?

The little cutouts around the cap of the mic were causing my measurements to have a steep -10 to -15 dB dip at around 8K-9K. You can see the Scotch tape I used to try and close up those gaps.

 

[McMadface]

The flat washer worked! Here's my latest measurement (in green) overlaid with Crin's 2 samples (red and blue). Does it makes sense that I'm losing a bit of energy in subbass because the rubber gasket that seals the end of the coupler may be a little worn?

 

[csglinux]

Nice job @McMadface My guess is that the little roll-off you have left at the extremes (both ends) are because of the mic. You could try throwing loads of putty or glue around the mic stem, but I doubt that will change anything. It's surprisingly difficult to find a mic that is truly flat from 10 Hz -> 22 khz. You may simply need to add a little compensation to account for your mic. @castleofargh explained how to do that here: https://www.head-fi.org/threads/general-iem-measurements-discussions.903455/page-11#post-14979787

BTW, if you'd like to do some validation of your new coupler/mic combo, I've got a suggestion for you. As part of @Otto Motor's new little thread on general measurements, I was hoping to get a common pair of headphones circulating around this group so we have a common measurement point. I've been in discussions with @hakuzen about this and was about to mail him a pair of Etymotic ER2SE, but maybe (if he doesn't mind?!?) I can mail them to you first. I think you live in the same state I do (California)? This way you'd have some other 711 measurements to compare against (I can make the raw data available to you also) and I could pass the next lot of (international) shipping costs on to you (Because @hakuzen lives in Europe.) Would you be interesting in joining our little ER2SE tour? It's not for the purpose reviewing an IEM, but purely for measurement comparisons. PM me your address if you're interested in collaborating in this.

 

[McMadface]

Nice job @McMadface My guess is that the little roll-off you have left at the extremes (both ends) are because of the mic. You could try throwing loads of putty or glue around the mic stem, but I doubt that will change anything. It's surprisingly difficult to find a mic that is truly flat from 10 Hz -> 22 khz. You may simply need to add a little compensation to account for your mic. @castleofargh explained how to do that here: https://www.head-fi.org/threads/general-iem-measurements-discussions.903455/page-11#post-14979787

BTW, if you'd like to do some validation of your new coupler/mic combo, I've got a suggestion for you. As part of @Otto Motor's new little thread on general measurements, I was hoping to get a common pair of headphones circulating around this group so we have a common measurement point. I've been in discussions with @hakuzen about this and was about to mail him a pair of Etymotic ER2SE, but maybe (if he doesn't mind?!?) I can mail them to you first. I think you live in the same state I do (California)? This way you'd have some other 711 measurements to compare against (I can make the raw data available to you also) and I could pass the next lot of (international) shipping costs on to you (Because @hakuzen lives in Europe.) Would you be interesting in joining our little ER2SE tour? It's not for the purpose reviewing an IEM, but purely for measurement comparisons. PM me your address if you're interested in collaborating in this.

I'll see if getting a better seal works first and then move onto compensation if it doesn't make a difference. I'm really beginning to appreciate how powerful REW is for being a free tool.

Yeah, I'd like to join that measurement tour. I can cover the cost of int'l shipping to @hakuzen, no problem. I'll PM you my address.

 

[hakuzen]

used silicone test drip tips to fit some non-threaded mics into 711 couplers (12mm), like these ones:
https://www.fasttech.com/products/8289301.

the walls (besides the washer) also help to isolate.

guess pressure field mics are more appropriated for iem measuring when using a coupler, than free field mics. and guess that blocking the sides of a free field mic also helps.

(the hole in the tips of above link are wider, more appropriated than the used in these pics)

 

[McMadface]

used silicone test drip tips to fit some non-threaded mics into 711 couplers (12mm), like these ones:
https://www.fasttech.com/products/8289301.

the walls (besides the washer) also help to isolate.

guess pressure field mics are more appropriated for iem measuring when using a coupler, than free field mics. and guess that blocking the sides of a free field mic also helps.

(the hole in the tips of above link are wider, more appropriated than the used in these pics)

Hey, what's the diameter of the hole in the tip? Might be worth checking out.

 

[hakuzen]

Hey, what's the diameter of the hole in the tip? Might be worth checking out.

dunno, because i've already ordered them. the ones i got time ago have narrower hole.
the tips of the link are 12mm inside, 13.4mm total diameter. doing an eye calculation, guess the hole could be around 7mm