Are these the correct things to buy for SPL measurements?

[ThomasW]

All programs are this way. It can only work this way.

OK here's my spin.....

If one has a calibrated $500 meter then go for it. The idea that a $50 RS meter can be trusted to establish some 'absolute' SPL standard makes no sense to me.

Now I'm a curmudgeon who thinks the entire concept of 'calibrated' speaker output levels is itself bunk. But that's a topic for another thread.....

[soho54]

ThomasW, I'm not trying to spin anything. The bit about "other software programs they just use the mic and tell you the SPL it's measuring..." was just a bit off.

You are right; you cannot get an "absolute" SPL reading from a RS meter. The thing is, I have never had any software measurement program get with in +/- 10db of the correct SPL, on a fresh install.

I was just trying to help out. Several people here seem a little lost, and unfortunately still do.

[chasw98]

OK here's my spin.....

If one has a calibrated $500 meter then go for it. The idea that a $50 RS meter can be trusted to establish some 'absolute' SPL standard makes no sense to me.

Now I'm a curmudgeon who thinks the entire concept of 'calibrated' speaker output levels is itself bunk. But that's a topic for another thread.....

I think we are talking about apples and oranges here. On the one hand, we talk about a $50 RS SLM and a piece of free software for "calibrating" our home theater systems and on the other we get into true ANSI calibrated instruments that are used to measure "sound systems" for proof of performance for a client. When large stadium or theme park systems are built an error of 3 db by a designer will cost the contractor double the money for amplifiers because it does not meet the specifications in the contract. You can bet your a$$ I want a 4133 with a 1/2" capsule hooked up to a preamp with standards traceable. When we talk about using REW or AVIA at home it is relative because of the accuracy of low cost consumer toys.
When I had my ECM8000 "calibrated" by Kim, I wondered why I did it afterwards because the mic was so close in response it didn't seem worth it. OTOH, I then knew what I was dealing with and removed an unknown from the chain. We need to keep all this "measurement" in perspective and realize it is what we can do reasonably at home with whats available for not much money. Thomas and I have remarked about equipment we had in our early days that cost a fortune but it was accurate. Today you can get the same thing for a fraction of the price, but it is relative and unless you put the money into traceable standards and laboratory calibration, you are just blowing smoke. But it does provide a reference point in time that you can see changes from. Accuracy to the nth degree, ain't happening, but relative changes can be seen and action can be taken from watching those changes and using them with a grain of salt.

Enough from me, I have to go look up curmudgeon and see if it has something to do with age. :B

Chuck


EDIT: I looked it up:
Definitions of curmudgeon on the Web:

a crusty irascible cantankerous old person full of stubborn ideas

[Dennis H]

I'm with Chuck. The RS meter will be within a dB at 1kHz so that's a pretty easy way to get close to an absolute SPL measurement. Good enough for guvmint work anyway. Of course, you can take the long way around and maybe come a little closer. Behringer publishes a mV/Pascal spec with the mic and you can poke around with your DVM and figure out the voltage gains/sensitivities of your soundcard and your mic preamp (with the gain knob at some setting) and maybe get all that translated into your software --- but it's a major PITA.

It's a lot easier using the DEQ2496 -- just plug the mic's mV/Pa into the setup menu and you're done.

Edit: 1 Pascal of pressure is 94dB SPL. Add or subtract 6dB if you double or halve the pressure (and the mic voltage which is proportional to air pressure).

[PMazz]

This is a graph of my RS analog meter compared to a calibrated mic. Note tho my meter was modded for low freq measurements. Green trace is the RS meter.

Image not available

Pete

[Wilk]

Moderators if this post is going to cause an issue just delete it, I understand.

I work for a calibration lab. We have a full Bruel & Kjaer sound stand with all the goodies needed for calibrating mics, and sound level meters. If you guys just need charted response graphs I could run them on the weekend no questions asked. Now if you really want NIST traceable certificates on them I would have to charge you.

Now my opinion on calibrating this stuff for home use is this. Radio shack anything is not calibratable. I have tested them, and they are about +/- 1dB from 60Hz, to 14KHz usually. The get very bad, very quick above or below that in frequency. Most of your speacker designs here are proably flatter than them. Mics are usually spot on, or destroyed. They are usually +/- 0.25 dB from 30Hz to 25KHz. They are also usually within 1 to 2 dB of reference without any of the correction formulas, If you bought a good one that has a posted sensitivity then it is most likely right on. The only thing that I have seen that is strange here is that there are a few pics on the forum of nearfeild testing on subs with mics. With a standard mic, the volume of air that is being pushed at the mic will most likely desrtoy a standard mic. There are mics designed to handle this, but they are usually very expensive.

[ThomasW]

I think we are talking about apples and oranges here. On the one hand, we talk about a $50 RS SLM and a piece of free software for "calibrating" our home theater systems and on the other we get into true ANSI calibrated instruments

Correct

Behringer publishes a mV/Pascal spec with the mic and you can poke around .......It's a lot easier using the DEQ2496 -- just plug the mic's mV/Pa into the setup menu and you're done.

With programs like the Clio suite (Clio, ClioLite, ClioWin), Praxis, and others, one enters the Mic cal file including the (mV/Pa) and you're good to go. This knowledge was the basis for my statement

other software programs they just use the mic and tell you the SPL it's measuring

This is a graph of my RS analog meter compared to a calibrated mic.

That mic plot has the cal file loaded?

The only thing that I have seen that is strange here is that there are a few pics on the forum of nearfeild testing on subs with mics. With a standard mic, the volume of air that is being pushed at the mic will most likely desrtoy a standard mic. There are mics designed to handle this, but they are usually very expensive.

Hopefully people understand what you're saying and are performing this particular measurement at a VERY low level.

[chasw98]

"ThomasW: curmudgeon in training "

Then who is going to mentor me?

[chasw98]

Moderators if this post is going to cause an issue just delete it, I understand.

I work for a calibration lab. We have a full Bruel & Kjaer sound stand with all the goodies needed for calibrating mics, and sound level meters. If you guys just need charted response graphs I could run them on the weekend no questions asked. Now if you really want NIST traceable certificates on them I would have to charge you.

Now my opinion on calibrating this stuff for home use is this. Radio shack anything is not calibratable. I have tested them, and they are about +/- 1dB from 60Hz, to 14KHz usually. The get very bad, very quick above or below that in frequency. Most of your speacker designs here are proably flatter than them. Mics are usually spot on, or destroyed. They are usually +/- 0.25 dB from 30Hz to 25KHz. They are also usually within 1 to 2 dB of reference without any of the correction formulas, If you bought a good one that has a posted sensitivity then it is most likely right on. The only thing that I have seen that is strange here is that there are a few pics on the forum of nearfeild testing on subs with mics. With a standard mic, the volume of air that is being pushed at the mic will most likely desrtoy a standard mic. There are mics designed to handle this, but they are usually very expensive.

:agree:

[Jack Gilvey]

Radio shack anything is not calibratable. I have tested them, and they are about +/- 1dB from 60Hz, to 14KHz usually. The get very bad, very quick above or below that in frequency.

That should be fairly useful for getting a calibration level for a program, or for using pink noise to balance speakers.
I use a generic cal file for my ECM8000.

[ThomasW]

"ThomasW: curmudgeon in training "

Then who is going to mentor me?

It will be a cooperative effort.... :B

[Dennis H]

With programs like the Clio suite (Clio, ClioLite, ClioWin), Praxis, and others, one enters the Mic cal file including the (mV/Pa) and you're good to go.

Clio and Praxis provide the (nonadjustable) mic preamp. If you're using a 3rd party preamp, the program doesn't have any way to know what its gain is.

[Mark K]

Clio and Praxis provide the (nonadjustable) mic preamp. If you're using a 3rd party preamp, the program doesn't have any way to know what its gain is.

Well, actually, you can send the preamp to KimG and he might run a cal file on both the mic and preamp, as he did for me. I think this is sort of case by case basis.

As for this whole cal thing. It's possible to get absolute levels in "diy" standards. Sure, it won't be up to gov/university/mil spec, but more than adequate for home/ht. And the RS meter at 1k is OK, as I recall from playing with it.

And from a relative standpoint, an ECM is probably one of the best deals around. It's not useable directly with praxis, but I've been thinking of getting one with a sound card to play with. I just bought another KimG mic, and honestly, you get a very well calibrated diy mic out to past 40k (well, to 48k, but the dropoff is such that I think the accuracy starts dropping significantly after 40k. You can send the ECM to Kim, or, just use a generic cal file available on the web. They appear to have very good consistency, as Thomas mentioned.

If I didn't use praxis, I'd just use the ECM/m-audio/SE or lspCAD and be done with it.

[PMazz]

That mic plot has the cal file loaded?

The ETF mic cal file was loaded, not the modded RS meter.

Pete

[ThomasW]

The ETF mic cal file was loaded, not the modded RS meter.
Pete

Strange, the ECM8000's we compared against Jon's mic are much flatter than that....

[ThomasW]

I was searching around and found this reference to KimG's cal service....

Actually there are three the way Kim calibrates a microphone. In addition to sensitivity and Frequency magnitude he also measures frequency phase. Also unlike the standard calibrator, be it diaphragm or piston, he measures at hundreds if not thousands of frequency points.

So I think I'll get an extra ECM8000 and send it out for him to calibrate. Then we'll look at that in comparison to what we found a few years ago when Jon compared the 3 mics to his 4133. And since Jon has purchased Praxis and it's recommended mic which is calibrated by Kim, that should make for an interesting comparsion too.

If we want to get even weirder it could be sent to Wilk and he could to his thing. Then we'd have multiple references..... 8O

[Mark K]

Thomas (or Jon),

I thought Jon got an ACO as well when he got praxis. A 1/3 of the price of a BK but still awfully expensive...

I've been eyeing that mic for a while, but my wife, well, she just doesn't understand :nono:

Please buy one and send it to me...

[ThomasW]

Thomas (or Jon),

I thought Jon got an ACO as well when he got praxis. A 1/3 of the price of a BK but still awfully expensive...

Correct I thought that was the recommend mic for Praxis?

[Dennis H]

Strange, the ECM8000's we compared against Jon's mic are much flatter than that....

I think the graph is Pete's in-room speaker response. It's just showing the difference in how the RS meter measures compared to the calibrated mic. It's really not too bad in the mid frequencies.

[ThomasW]

I think the graph is Pete's in-room speaker response. It's just showing the difference in how the RS meter measures compared to the calibrated mic. It's really not too bad in the mid frequencies.

Now that makes sense, I thought that was a really rocky curve to simply be the plot for a calibrated mic.... :B

[Wilk]

I am up for it. I just pulled the spec sheet from Beringers web site, and it has a sample of their freq response curves, and phase plots. I should be able to duplicate that data real easy.

On a side note that is a really clean FR graph fore a $50.00 mic. We work mostly with metrology grade mics that cost 10X that, that are not a whole lot better.

[Wilk]

For those who are interested in a little more accuray/capablility on a sound level meter than the $50.00 radio shack units check this site out. www.used-line.com just do a serach for sound level meter. Any of the $200 dollar Extechs will do no very nicely. I see these things by the dozen at work, and they all are pretty decent.

Anything else test equipment wise you want is there to, Level sine wave generators, and whatnot.

I do however feel that anything more than a good sound level meter, and cheap mic setup is serious over kill for the DIY builder. My suggestion is to call your local third party calibration house. They are always looking for something new to test, and will usually jump at the chance to test a speaker out. Microphones, and meters get real boring real quick.

[ThomasW]

We work mostly with metrology grade mics that cost 10X that, that are not a whole lot better.

I'm not sure if that's a good thing or a bad thing.... :B

[Mark K]

Correct I thought that was the recommend mic for Praxis?

Well, I guess it is one of the recommended two choices. Mere mortals can buy a KimG mic based on everyone's favorite panasonic capsule, for a mere $140. That ACO is over ten times the price. Very nice though. I'm pretty sure that's the mic that Vance Dickasen uses. I didn't know Jon made over ten times as much as I do... :E

Overall, I agree with Wilk. Anything more than a $50 ECM is overkill. As much as I'd like an ACO Pacific, it's hard to justify. Hey, SL seems to do just fine with the panasonic diy mic capsules...

[ThomasW]

That ACO is over ten times the price. Very nice though. I'm pretty sure that's the mic that Vance Dickasen uses. I didn't know Jon made over ten times as much as I do... :E

Jon earns just a bit less than Bill Gates..... :B , but I don't think he paid that much for his ACO. I'll ask next time we talk.

[chasw98]

I was searching around and found this reference to KimG's cal service....So I think I'll get an extra ECM8000 and send it out for him to calibrate. Then we'll look at that in comparison to what we found a few years ago when Jon compared the 3 mics to his 4133. And since Jon has purchased Praxis and it's recommended mic which is calibrated by Kim, that should make for an interesting comparsion too.

If we want to get even weirder it could be sent to Wilk and he could to his thing. Then we'd have multiple references..... 8O

If you want, PM me, and I will lend you my ECM8000 for testing. I just got it back from KimG a month ago. Let me know. Why should you spend $100 extra for testing?

[JonW]

Hey Folks,

In case any of you are looking to buy a Mobilepre USB, Amazon has a nice sale on that now. It's about $130 with free shipping, which is cheaper than most online places ($150). And then there is a $25 rebate. I just ordered mine. XLR cable is also on the way. The mic and stand are at home awaiting their playmates. Now I've got to get the computer end of things up to speed. I think this will be a fun toy.

-Jon

[ThomasW]

Thanks for the heads up Jon that's a very good deal..... :T

[Inu_Yasha]

Would this mic stand be ok?

http://www.musiciansfriend.com/product/OnStage-Stands-MS7510-Mic-Pro-Pak?sku=270619

It comes with a mic as well (I do a lot of singing and an extra mic would be nice).

[ThomasW]

Would this mic stand be ok?

http://www.musiciansfriend.com/product/OnStage-Stands-MS7510-Mic-Pro-Pak?sku=270619

It comes with a mic as well (I do a lot of singing and an extra mic would be nice).

Yes that's just fine... :T

[MuaDibb]

Hey guys, one more option. I was in the local Guitar Center and they have the Mobile Pre for $149, and its little brother with one input for $99. They also have the Behringer mic for $49. Maybe not the absolute cheapest, but if you don't like waiting on mail...........

[JonW]

Yup, those Guitar Center prices seem to be the going rates. Except for the Amazon thing on the Mobilepre.

I just lucked out when my gal mentioned she has a 5 year old PC laptop that she doesn't use anymore. I put Room EQ Wizard on there and the program booted up. Looks like it might work when my Mobilepre arrives. That would be cool. I'll have everything ready to take measurements. Well, everything but lots of free time to do it.

Say, do you point the microphone straight up in the air? I'd think that would be best for getting sound from each speaker around the room.

[ThomasW]

Bummer, I was hoping we could get you good and lost trying to setup and use Fuzzmeasure... :B

For nearfield measurement put the mic 90 degrees to the cone/dome. For in room/listening position just aim it at the speaker. Some recommend pointing it up when dialing in a sub.

[JonW]

Thanks, Thomas. Let's not rule out a future purchase of Fuzzmeasure. And the subsequent confusion.

[ThomasW]

Actually Jon I had ulterior motives even more insidious than you can imagine.... 8O

Jon's convinced me to move over to the 'dark-side' = Apple. The plan is to start buying in when one or two of my current crop of 5 PCs croak.

Jon has Fuzzmeasure up and running but of course it's no challenge for him. My 'master' plan was to have you start with Fuzzmeasure and I'd learn off your learning curve.

See us old guys can be crazy,...... like a fox..... :wink: :B

[chasw98]

Actually Jon I had ulterior motives even more insidious than you can imagine.... 8O

See us old guys can be crazy,...... like a fox..... :wink: :B

Curses, foiled again! :rofl:

[JonW]

I see how this game works. I'll monkey around with REW and the PC and see how things go. Maybe I'll still buy Fuzzmeasure. And then it'd be on my laptop so I could bring it by your place in the future, to let you play around with it. But I doubt I'll be using anything too complex with the software. This is my first experience with all this. So probably not tons to be able to teach anyone.