You have two good mics and a good pre-amp. Before spending more money, solve the problem. There should be skilled people near Roswell that can solve your problem. It's not a mismatch problem and it's not a calibration problem.

 

You have two good mics and a good pre-amp.

But no mic calibration files.

 

(c)Any ideas why my existing mics used with my mic preamp gave weird results?

You haven't told us the model numbers of the mics or preamps, and what the problems are?

brucek

 

I believe Earthworks maintains calibration files for all their measurement mics, so you should be able to call them with your serial number and order up the file. They do charge for them. As far as matching with the correct mic preamp, yes you need to watch load impedance. My Earthworks M50 has a minimum required output impedance load of 600 ohms. Most mic preamps have an input impedance rating of at least 5Kohms, so there should not be any issues using it with them. Which Rane product do you own?

 

I have an Earthworks M30 and I did call them about getting a calibration file. Mine is old enough that they do not have one so I would need to send it to them or someone else to get calibrated. The paper version is no good since all of the data would need to be hand-entered.

The other mic is a Josephson model number C550H

The mic preamp is the Rane model number MS1.

I did not save any of the results I got since they were so far off track. If it is important to do that, I can do it tonight and post the results.

One other thing that could be causing the problem is the Rane only has XLR input and outputs and the sound card only has RCA. It's not a problem on the mic side since I am using XLR mic cable. I'm using a converter on the output side to the mic preamp to the sound card and maybe that plays a role in this.

Sound card is Soundblaster USB.

 

The Rane product should have plenty of input impedance for your mic. Yes, it could be an adapter issue, it could be the quality of your mic cable and how it's passing phantom power to the mic, it could be an input issue with the sound card or a defective sound card or a driver issue, it could be any number of other things.

What exactly is the nature of your "weird" results?

 

One other thing that could be causing the problem is the Rane only has XLR input and outputs and the sound card only has RCA. It's not a problem on the mic side since I am using XLR mic cable. I'm using a converter on the output side to the mic preamp to the sound card and maybe that plays a role in this.

You don't require a converter. Simply use a 1/4" TS connector at the RANE end and an RCA on the other end of the cable. This will result in an unbalanced signal to be sent to the soundcard.

brucek

 

And a "TS" connector is what?

 

The sound card is brand new and works perfectly well with the RS meter. The driver is also the most recent.

The mic cable has been used 30 bazillion times with the Earthworks mic and and works perfectly fine in another application (not utilizing this sound card. I do not believe it is the mic cable. I have two other mic cables and they work perfectly fine as well.

As noted previously, I did not save the results of the measurements with the other mics but since everyone keeps asking, it appears I need to do that tonight to get assistance.

The real variables in all of this is the preamp and the adapter.

 

And a "TS" connector is what?

Tip Sleeve (TS) as opposed to a Tip Ring Sleeve (TRS). The TS connector provides a ground to the negative balanced output and renders the balanced connection unbalanced. If you use a TRS plug, then that would be why your results were 'weird'. You require a 1/4" TS to RCA cable.

brucek

 

Would Radio Shack carry such an item (TS) or will I need to go elsewhere?

 

Would Radio Shack carry such an item (TS) or will I need to go elsewhere?

Yes, you can get a simple adapter at Radio Shack that changes 1/4" TS male to RCA female here. Then you just need an RCA cable to go to your receiver.

Some people like to simply buy a complete cable with a 1/4" TS at one end and an RCA at the other end.

brucek

 

I must have not explained carefully enough. I do not have any 1/4 connections. I have the 3 pin male XLR/balanced connector on the mic preamp output. I have a female 3 pin xlr to female RCA connector that I would use to connect to my soundcard ... but don't understand about TS vs TRS. I will try it as soon as I can. If that does not work, Im not sure what plan B is?

 

The difference is one letter: phonE - phonO

RCA phonO - small MONO connector with 1/8 inch pin
RCA phonE - TS - large MONO connector with 1/4 inch pin -Tip, Sleeve
RCA phonE - TRS - large STEREO connector with 1/4 inch pin -Tip, Ring, Sleeve

 

I must have not explained carefully enough. I do not have any 1/4 connections.

Ahh OK, I incorrectly assumed the output was 1/4" - most are - my mistake. But you still require the XLR to RCA to unbalance the connection, which I assume the XLR to RCA cable you have takes care of. Sorry for the confusion.

brucek

 

I just ran three measurements: One with the Josephson mic (no cal file), one with the Earthworks mic (no cal file) and one with the RS meter (with cal file).

As you can see the two mic plots are very similar and fall off greatly below 50Hz such that they are down more than 10db at 10Hz.as compared to the RS measurements and some done with other mics (with cal files)

I have seen a number of mic cal files and except for the RS, did not know of one that the low end was off by that much.

Do you believe it is a cal file issue or something else??

 

Again, what issue do you think you are having? Because the three curves are different? That is completely normal: every microphone has a different response characteristic, thus the need for calibration. I see nothing in those curves that indicates to me that you have any sort of hardware issue...

 

David:

I would certainly not expect the curves to be exactly the same. What I previously carefully noted was the rather HUGE difference below 20Hz where the two mics are down 10db from the other measurements I have taken at 10Hz (one w/RS and two more with other mics and mic preamps).

The two available cal files on this site (ECM 8000 and EMM 6) show a correction of less than 1.5 db at 20Hz. As you will note on the previous chart, with the two mics I plotted, they are down about 6+ db from the "reference" at 20Hz. So while you may be convinced what I'm seeing is normal given the lack of cal files, I need to be convinced before I spend the money for shipping and calibration.

 

All I'm saying is what you're seeing may indeed be the response curve of the microphones or the mic preamp. It looks much more like that than like any hardware error. Plus the fact that the shapes of all three curves are identical indicates they are responding to the characteristics in your test setup.

 

The Radio Shack meter calibration file is generic. The meter you have may well be an outlier and could be many dB off from the generic file you're using. The only way to be certain about any meter or microphone is to have it calibrated.

brucek

 

WOW!

You own an Earthworks measurement mike (best on earth) and are using it with a consumer soundblaster usb!

Uhhh there's something wrong with that picture...

If I could afford that mike I'd at least use it with a decent device like an Echo Audiofire2 or something of that caliber.

I'm currently considering two setups. A Tascam US-144mkII with a Galaxy CM-140 or an Echo Audiofire4 with a Earthworks M23... I can't imagine owning a M30 buddy... and that mike is worth more than $700 even if it's an old serial #. You'd be nuts to not send it in to Earthworks to get a calibration file and a servicing etc. That mike is the second best test mike on earth and if I had a third option with unlimited budget I figure an M50 with an flagship echo, apogee or RME device would best a LinearX LEAP costing thousands for all intensive purposes...

with the right software...

Solid-State

 

Audioguy I'd seriously get a better soundcard as IMHO that Soundblaster USB is really poor. You have the second best test mike on earth bar none. A fantastic true differential mike pre-amp with a proper balanced cross-coupled with pin 1 chassis ground. All you need is a decent firewire or USB based sound-card and it doesn't need phantom or cheap preamps with that wicked Rane unit. IMHO considering the quality of the gear you have, I'd get an Echo Audiofire2 as it has no input gain pot that can hurt fidelity to some extent (soft mixer) and you use the gain pot on the Rane unit. As for cable I'd get some Mogami W2549 cable. Redco.com can make up some segments for you CHEAP. Audioguy your almost there to a test rig that all of us would be jealous of and even better than a lot of DIY guru speaker builders use. IMHO that mike, pre and firewire capture would be almost on par with a LinearX rig if using calibration files and the right software. Brother the Echo unit is about $200 bucks and Earthworks damage on a config file and a servicing should be no more than $150-200 bucks. You're almost there! Don't skimp at this point with a Soundblaster... Ugg it's a sin to plug such high quality mike/pre into that Creative Stuff A SIN!!! and I'd be surprised if it even worked considering it's consumer line level

Solid-State

 

I'd also like to add that the output on the Rane MS 1S is +4dBu double ended. I don't believe the soundblaster has an input of this type as it's consumer -10 dBV single ended line level. In your PM you mention you have an ESI unit. On their site there is no mention or publication of any of the input specs on the unit. It's relatively expensive unit when compared to what's out there if it only has single ended -10 dBV. I'd assume it's +4 dBV single ended. Please read this article at Rane regarding connecting unbalanced gear to balanced and -10 to +4 "nominal levels"

Sound System Interconnection - The RIGHT WAY to do it!

PS Hint! The MS 1S is also cross-coupled I believe! In chart your cabling should be entry 5 in the list of pinouts for the ESI... the Soundblaster is a no go!

 

Time and again I read about people who adjust their system to the resolution limits of their EQ equipment. Yet, if we used a different brand of mic and software (equally accurate) with the mic in a slightly different position the response curves differences would be great. Or if you use sustained tones for calibration then the transient response will be poor and vice-versa . In real world rooms, mic cal. is the least of your problems.