Give Me a Crash Course in Acoustic Measurements!

[slipperybidness]

Could a few of you that are experienced with in-room measurements provide some info here for a quick crash course in measurements?

I'm more or less at diminishing returns on my electronics and speakers, and there almost has to be low hanging fruit in my measurement and room treatment options.

What I am most interested in:

1) What hardware and software do I NEED to get started to get some good results and improvements? Seems like the UMIK and REW are the most popular?

2) I am most interested in getting measurements for my existing setups to help me determine how to improve them, then get the measurements to prove that I have actually made an audible improvement.

3) I am building a set of the Phil BMRs, so when these are done I would like to take measurements to confirm that I am indeed getting the FR that the designer intended.

4) What have I missed?

Those items look like a good start to me!

@Pogre
@shadyJ
@Alex2507
@Swerd

 

[Pogre]

REW and the UMIK are great for seeing areas of opportunity for sure. I've made huge improvements based on measurements and my ears.

As far as building a speaker goes, especially one of that pedigree I don't know if REW would be enough for the level of detail I'm guessing would be required for such a project. That's just a guess, I've never put a speaker together from scratch, but the charts I see from TLS, Ascend and Salk look like they're using something different.

 

[shadyJ]

Yes, all you will need is REW and a UMIK mic. However, testing loudspeakers is a bit involved. You need to point the mic at the speaker at about a one-meter distance, and you need the microphone and speaker to be as isolated as possible. It helps if you can mount the mic on a boom pole. As for using these systems to improve room acoustics, its mainly good for helping the bass response. Once you know your speaker is right, the mids and highs should be fine so long as the speaker placement is good.

 

[slipperybidness]

Yes, all you will need is REW and a UMIK mic. However, testing loudspeakers is a bit involved. You need to point the mic at the speaker at about a one-meter distance, and you need the microphone and speaker to be as isolated as possible. It helps if you can mount the mic on a boom pole. As for using these systems to improve room acoustics, its mainly good for helping the bass response. Once you know your speaker is right, the mids and highs should be fine so long as the speaker placement is good.

To be clear....this is what we are talking about on the mic?

miniDSP UMIK-1 Omni-directional USB Measurement Calibrated Microphone

miniDSP UMIK-1 Omni-directional USB Measurement Calibrated MicrophoneThe UMIK-1 is an Omni-directional USB measurement microphone providing plug-and-play acoustic measurement. From speaker and room acoustic measurement to recording, this microphone provides low noise and accurate results you can...

www.parts-express.com

Or, is there a newer/better model I should be looking at? At that price, looks like a no-brainer.

Does this come with REW? Or that is a free download somewhere else?

 

[shadyJ]

Yes, that UMIK mic is the one you want. REW is a free download. However, I would encourage you to make a small donation to the creator if you end up finding it useful.

 

[slipperybidness]

Yes, that UMIK mic is the one you want. REW is a free download. However, I would encourage you to make a small donation to the creator if you end up finding it useful.

Thanks for the info!

I will also keep that donation suggestion in mind. I am a big proponent of the maker movement, the "tip the designer" and the "pay what you think it is worth" model.

 

[Verdinut]

I strongly recommend the Dayton OmniMic V2 Acoustics Measurement System to test speaker frequency responses. I have been using it when building speakers and obtained very good results with it. Here it comes with the DATS speaker testing software. If you intend to start building speakers, I suggest that you order both softwares.
However, you can also order only the OmniMic system:

Home

OmniMic V2 and DATS V3 Dayton Audio Speaker Measurement BundleAccurate measurements and specs are essential when designing and building speaker systems and Dayton Audio's OmniMic V2 and DATS V3 can help you with each step in the process. Whether you are verifying the T/S parameters of a woofer...

www.parts-express.com

Here is a snapshot of the frequency response of a 3-way speaker which I built 5 years ago measured with the OmnMic:

 

[ryanosaur]

REW and the Umik-1 is less expensive, steeper learning curve. Omni Mic is more expensive, shallower earning cuve (so they say).

(I sent my Omni Mic to Cross Spectrum just before the Covid Shutdown...)

I still haven't gotten it back, even though CSL has been back for a month!

*sighs

What AVR/RoomCorrection do you have? Even Audyssey XT32 with the App can be helpful!

 

[ryanosaur]

Oh... and a Boom-Mic stand like Amazon Basics! Very helpful!!!

 

[Alex2507]

4) What have I missed?

Swerd's getting @ss surgery today and you must have me confused with somebody who knows what they're doing.

 

[Kvn_Walker]

Definitely buying a UMIK after our move is completed. I want to get my monsters sounding their very best.

 

[TLS Guy]

UMIK is excellent, but I would get a pro mic stand, that is floor mounted and adjustable. The only problem with UMIK is that it rolls off above 15 KHz, but this is not a big problem.

You have to remember these quasi anechoic measurements are pretty reliable above 400 Hz, but have to be regarded as a good guide below that point.

Point the mic at the tweeter axis. The correct distance is 1 to 2 meters. If there are a lot of drivers, you may have to go to 2 meters to get a good blend.

You need to get off axis measurements also.

Good luck with the build.

Just remember those BMRs have a reversed phase midrange, to avoid a null at crossover.

The problem will come is that if you use it for HT and your center is a two way, or three way with in phase mid, then your mids of the BMR will be out of phase with the center. I can assure you this is a bad problem. I ran into this with my in wall system. So I had to accept the crossover null. This was by far the lesser of evils. Fortunately the null was pretty much confined to the axis, and so the in room response was acceptable.

 

[slipperybidness]

Yes, all you will need is REW and a UMIK mic. However, testing loudspeakers is a bit involved. You need to point the mic at the speaker at about a one-meter distance, and you need the microphone and speaker to be as isolated as possible. It helps if you can mount the mic on a boom pole. As for using these systems to improve room acoustics, its mainly good for helping the bass response. Once you know your speaker is right, the mids and highs should be fine so long as the speaker placement is good.

Thanks. To be clear, I'm not looking to thoroughly measure and characterize a loudspeaker, nothing near what you do in reviews.

I am simply looking to get a few quick and dirty measurements to identify obvious design flaws or mistakes, and confirm that a DIY speaker "meets the designer's original specs".

 

[slipperybidness]

REW and the Umik-1 is less expensive, steeper learning curve. Omni Mic is more expensive, shallower earning cuve (so they say).

(I sent my Omni Mic to Cross Spectrum just before the Covid Shutdown...)

I still haven't gotten it back, even though CSL has been back for a month!

*sighs

What AVR/RoomCorrection do you have? Even Audyssey XT32 with the App can be helpful!

I have the Denon 4400 and 3500. I believe these are both XT32, but I have not even kicked on Audyssee nor taken the mic out of the packaging yet!

I am certain that I have some low hanging fruit with XT32 as well. It seems like I should get the Audyssee app?

This is why I gave a shout to @Pogre I think he went through quite a bit of fiddling with these lately?

Edit--I have used the Pio MCACC in my older elite unit. I never used it for music, just for movies.

 

[slipperybidness]

UMIK is excellent, but I would get a pro mic stand, that is floor mounted and adjustable. The only problem with UMIK is that it rolls off above 15 KHz, but this is not a big problem.

You have to remember these quasi anechoic measurements are pretty reliable above 400 Hz, but have to be regarded as a good guide below that point.

Point the mic at the tweeter axis. The correct distance is 1 to 2 meters. If there are a lot of drivers, you may have to go to 2 meters to get a good blend.

You need to get off axis measurements also.

Good luck with the build.

Just remember those BMRs have a reversed phase midrange, to avoid a null at crossover.

The problem will come is that if you use it for HT and your center is a two way, or three way with in phase mid, then your mids of the BMR will be out of phase with the center. I can assure you this is a bad problem. I ran into this with my in wall system. So I had to accept the crossover null. This was by far the lesser of evils. Fortunately the null was pretty much confined to the axis, and so the in room response was acceptable.

That is an excellent detail to remember! Thanks!

Note--Dennis says that the BMR on its side with a 90 degree rotated tweeter will make an excellent center channel (over on that other forum), and won't even need a XO mod to do it. He did make mention of some small artifact that is best to just accept it, I would have to go sift through that thread again to remind myself on it.

 

[slipperybidness]

Thanks to everyone that has replied to date!

Here is my brief summary at this point:

1) Let's see what Audyssee and the app does for my in-room performance.
2) Go ahead and purchase the UMIK and download REW (it is cheap, but a bit of a steep learning curve)
3) Consider the Omnimic (I'm gonna hold on that for now due to $$$)

 

[Pogre]

Thanks to everyone that has replied to date!

Here is my brief summary at this point:

1) Let's see what Audyssee and the app does for my in-room performance.
2) Go ahead and purchase the UMIK and download REW (it is cheap, but a bit of a steep learning curve)
3) Consider the Omnimic (I'm gonna hold on that for now due to $$$)

There you go man. Get to reading up on REW. There are 2 ways to go there. Asio or Java (you can choose under "preferences" I believe). I found using Java was a lot easier as far as getting started. My first time out I found instructions for using Asio and didn't even know about Java. With Asio you can measure every speaker in a multi channel setup individually and Java only let's you choose sub, L or R. Which is all I need and the learning curve for Java isn't as steep or complicated.

I don't wanna confuse anything with the above explanation, but I wish I'd found the instructions for Java first instead of Asio. It would have saved me some headaches. Once you get your arms around REW you can also use it to help find optimal placement for speakers and subs super easily. You move a speaker or sub, take a 10 second sweep, wash, rinse repeat until you find a spot that works and measures best, before doing any room correction or eq at all. The easier you make it on Audyssey the better it will do. Even a couple dB gain back from a null with a little repositioning beforehand can me a big difference in Audyssey's results.

 

[lovinthehd]

UMIK is excellent, but I would get a pro mic stand, that is floor mounted and adjustable. The only problem with UMIK is that it rolls off above 15 KHz, but this is not a big problem.

You have to remember these quasi anechoic measurements are pretty reliable above 400 Hz, but have to be regarded as a good guide below that point.

Point the mic at the tweeter axis. The correct distance is 1 to 2 meters. If there are a lot of drivers, you may have to go to 2 meters to get a good blend.

You need to get off axis measurements also.

Good luck with the build.

Just remember those BMRs have a reversed phase midrange, to avoid a null at crossover.

The problem will come is that if you use it for HT and your center is a two way, or three way with in phase mid, then your mids of the BMR will be out of phase with the center. I can assure you this is a bad problem. I ran into this with my in wall system. So I had to accept the crossover null. This was by far the lesser of evils. Fortunately the null was pretty much confined to the axis, and so the in room response was acceptable.

Isn't it rather the Omnimic that has the reputation of the problems at the upper end of the frequency range rather than Umik?

 

[Verdinut]

Isn't it rather the Omnimic that has the reputation of the problems at the upper end of the frequency range rather than Umik?

I own the OmniMic testing system and its mic has no frequency range problems.

 

[lovinthehd]

I own the OmniMic testing system and its mic has no frequency range problems.

I've not had particular issues with mine but thinking either TLS or Dennis M had mentioned that experience/issue about Omnimic before....and would think if certified by a third party like Cross Spectrum not an issue for either.