Theatre finally built, now acoustic treatment time.

[carlos]

Thanks,
Yes, I do find creating things with my own hands very satisfying. DIY is not necessarily cheaper as it is more of a personal goal, experience, and hobby. I still have the Clouds to build, and the back wall to address.

 

[ddude003]

Hi @carlos, It is probably not a good idea to use a 25 ft USB extension for your test microphone... May I suggest you create test tones with the Generator function, with a timing ref, saved to a file... Transfer the test tone to your music player app... Then you can play the sweep tone through your entire signal chain player and move the laptop closer to the microphone without that 25 ft USB extension... Now you are using the laptop, running REW, only to take the measurements...

 

[carlos]

Hi ddude003,
Thanks for the suggestion. I will try this and post the results.

 

[ddude003]

Hi again @carlos... I was just rereading this thread and realized you were asking about an iMM-6 microphone... I just sas the MM-6 and thought of the EMM-6 mic... Could you please clarify what microphone you are using and is it USB connected to a laptop? Thanks...

I am looking forward to seeing some new sweeps from 20Hz to 22kHzish... Still wondering what that 7kHz to 10kHz rolloff is all about... And I still need to take a look at your speaker specs... BTY kudos for your DIY style...

 

[carlos]

Thanks, my mic is not a USB. It is the TRRS type little mic, IMM-6. I am leaning towards purchasing a UMM-6 USB mic.

 

[ddude003]

After a few moments looking at your speakers build, specs and some of your charts... I might think that the tweeter cab may not be functioning as expected... This could mean a few things to double check... Have you done any measurements of each of the four drivers at one meter? Are you bi-amping the tweeter cab and the mid-bass cab? As it seems that the mid-bass rolls off at around that ~7kHz down to 10kHz... So if the tweeter cab is not at the same level for some reason, that may be an issue... So Tweeter attenuation may be off? It should be pretty flat all the way out to 20kHz... Like this graphic from the source...

http://www.troelsgravesen.dk/DISC4-files/v3-imp-final-Tatt-2R2-2R7-3R3-1000.png

Just a guess at this point...

A miniDSP Umik-1 or a Dayton EMM-6 should be fine... And a mic stand would help...

 

[carlos]

Thank you,
I have contacted the designer of the speakers, and waiting to see if I made a wiring error.

 

[carlos]

Well, the designer was not helpful at all. I am not impressed with him. For the cost of the kit, very disappointing. Lesson learned.
I have done a new test, mind you, I have my room treatment partially in.
I think the dip is from my sound card. The chances of both tweeters not functioning properly is a possibility, but they sound fantastic to the ear.
I have also included my cal file.
Edit: Since my mic is a trrs connection, I have the cable going to my headphone/mic input on the computer. I will need a usb mic with the sound card built in like the UMIK-1.

 

[ddude003]

You might be interested in this paper from B & K that suggests what a small room response might look like...

https://www.bksv.com/media/doc/17-197.pdf

I can not say where your issues lie, only that your measured test suggest there is an issue above approximately 5kHz to 7kHz on up to 20kHz...

I think you should get a USB mic and mic stand and test each of the four drivers at one meter... Because there should not be such a drastic rolloff between the mid and high frequencies...

 

[carlos]

You are right. Looking at the designer's chart, I realize that the mid-bass is performing correctly. The tweeters are not working, as you suggested earlier.

 

[ddude003]

I wouldn't suggest the tweeters are not working at all.... Maybe just not working correctly... Somehow not at the same level as the rest of the design...

I would think these speakers would sound amazing when the bugs are worked out...

 

[carlos]

Well, I swapped out tweeters, re soldered my crossovers. Then swapped out for a different speaker. No difference in my measurements. So this is a software or hardware problem. Not my speakers, thankfully.
Edit: Seems the microphone has a limit a 7kHz. I will order a dsp-umik-1.

 

[Todd Anderson]

Hi @carlos, It is probably not a good idea to use a 25 ft USB extension for your test microphone... May I suggest you create test tones with the Generator function, with a timing ref, saved to a file... Transfer the test tone to your music player app... Then you can play the sweep tone through your entire signal chain player and move the laptop closer to the microphone without that 25 ft USB extension... Now you are using the laptop, running REW, only to take the measurements...

Curious - why is the extension not a good idea?

 

[ddude003]

Curious - why is the extension not a good idea?

Because specs matter... USB cable length is limited by the USB standard. Typically, USB 2.0 cables are limited to 5 meters (16 feet), while USB 3.0/3.1/3.2 cables are often limited to 2-3 meters (6-9 feet). Exceeding these limits can lead to signal loss and reduced performance... USB 3.2 Gen 2x2 is typically limited to 1 meter (3.3 feet) for optimal performance... And USB 4 is limited to a maximum of 0.8 meters (2.6 feet) to maintain optimal data transfer speeds...

And Murphy's Law, in its simplest form, states that "anything that can go wrong will go wrong"...

Although, I had wrongly assumed that the microphone the OP was using a USB connection...
I am not sure about the iMM-6 connectivity currently used by the OP...

 

[ddude003]

Well, I swapped out tweeters, re soldered my crossovers. Then swapped out for a different speaker. No difference in my measurements. So this is a software or hardware problem. Not my speakers, thankfully.
Edit: Seems the microphone has a limit a 7kHz. I will order a dsp-umik-1.

The Dayton website for the iMM-6 says "Frequency Response: 18-20,000Hz, ±0.5dB (calibrated)"...
I am pretty sure that reads 18 Hz to 20 kHz...

 

[carlos]

I am not sure about the iMM-6 connectivity currently used by the OP...

The iMM-6 uses a 3.5mm TRRS connector cable. I was using a 25-foot extension cable. I have returned the iMM-6. I have a Sonarworks SoundID XLR mic ordered.

 

[carlos]

Yes, perhaps I have a bad iMM-6. I even tried using a usb sound card. No difference. Still 7kHz drop.

 

[Todd Anderson]

Because specs matter... USB cable length is limited by the USB standard. Typically, USB 2.0 cables are limited to 5 meters (16 feet), while USB 3.0/3.1/3.2 cables are often limited to 2-3 meters (6-9 feet). Exceeding these limits can lead to signal loss and reduced performance... USB 3.2 Gen 2x2 is typically limited to 1 meter (3.3 feet) for optimal performance... And USB 4 is limited to a maximum of 0.8 meters (2.6 feet) to maintain optimal data transfer speeds...

And Murphy's Law, in its simplest form, states that "anything that can go wrong will go wrong"...

Although, I had wrongly assumed that the microphone the OP was using a USB connection...
I am not sure about the iMM-6 connectivity currently used by the OP...

Makes total sense

 

[ddude003]

@carlos, I guess you did not create a sweep file like I suggested above... So, I think you may need to use https://www.roomeqwizard.com/help/help_en-GB/html/makingmeasurements.html#acousticref if you are creating the sweeps from your laptop and measuring too... Guessing it is a windoz os... So use Java drivers...

 

[carlos]

Hi, yes, sorry I got confused on creating the file. I am re-reading the directions now. Do I disconnect my laptop from the HDMI going to my receiver? I would be using the laptop independently of the speakers, except for the recording of the tone sweep? Laptop + mic only. I tried using Alexa to my receiver, playing a 20Hz to 20kHz sweep set to 600s. But it showed no difference.

 

[ddude003]

You would create a sweep tone file using the Generator function... Copy the sweep tone file to a usb storage thumb drive... Stick the thumb drive in your receiver... Yes, you would not have the laptop plugged into the receiver... Use the laptop only to take the measurement... It should listen for the timing ref... Play the tone with the timing ref like you would any music file... Upon hearing the timing ref tone REW will begin its recording of the sweep...

I've explained this several times before in these forums... Here is an example...

Post in thread 'Transmit sweep Signal from REW'

Jun 29, 2024

Use the REW Generator function to create a .wav file... You would end up with a .wav file containing a sweep with a timing reference that can be transferred to a CD or USB jump drive that you play thru your signal chain (read audio head unit)... Or even transfer the .wav sweep file to your phone if you use that as your playback device for your signal chain... Use a separate laptop with a usb mic running REW to capture the measurement...

• ddude003

• 

And press the WAV button...

 

[carlos]

Thanks for that. It makes sense now. Here is the measurement. Same drop off at 7kHz. My speakers are working through the sweep. The high pitch eats at your brain, so to speak.

 

[ddude003]

I still go back and look at the measurements section of the speakers http://www.troelsgravesen.dk/DISC-4.htm#CROSSOVER...
It is remarkable to me that your measurement looks like the first graph showing the low bass speaker... Rolling off around 5kHz and on down to 10kHz... I can not account for the difference between the tweeter attenuation from your measurement and what is shown in the rest or the measurements on that website...

I would wait until you get another microphone and stand and measure each driver separately at 1 meter... Low Bass, Upper Bass, Midrange and Tweeter... My guess is there is a level mismatch with the tweeter...

 

[carlos]

I ended up getting a UMIK-1. Totally different results.

 

[ddude003]

I ended up getting a UMIK-1. Totally different results.

That looks a lot more like what one would expect... Good job!
Left and right speakers seem to track each other pretty well... Got some peaks and dips to work on... First some physical room correction with your bass, wide-band absorbers and diffusers ... It would still be nice to see what each driver looks like at 1 meter...