Converting Infinity Infinitesimal 0.1 speakers to DSP crossover

[HAL]

Found a pair of Infinitesimal 0.1 speakers that someone had changed the 5in Watkins 8 Ohm dual voice coil speaker to a FOCAL 5in dual voice coil replacement.  Sadly one of the FOCAL drivers has one voice coil open and even FOCAL does not know how to repair them. So time for some fun!

Could not find any original 0.1 woofers, but found a pair of 0.3 Watkins 4 Ohm single voice coil drivers.  These do not work with the existing passive crossovers, so time to remove them and convert to direct drive for active speakers.

Made a simple replacement connector panel for two sets of 5-way binding posts.  Added a fuse holder inline with the EMIT planar tweeters for protection.

Ever since hearing a pair of Infinity IRS Reference III's in 1979, the EMIT and EMIM planars have always sounded great, but need a little help.  They extend to at least 30KHz and very short impulse response.  They are easy to EQ flat.

Using Audio Weaver for the DSP crossover and room EQ software to run the dspNexus 2/8.

First measurement was an impulse test for time alignment.  Had to add 13 time sample delay to the tweeter to match the woofer to give a coherent wavefront.  It is easily heard in image stability.

Will be doing more in seat room measurements to flatten out the response.  If it is to bright I have designed a variable Harman EQ process that lets the user adjust the response at their seat.

[Nick B]

Interesting project, Rich. I hadn't heard of that particular model. Did hear the IRS a few times, but that was years ago.

When you did the measurements for time alignment, did you use Audio Weaver? Did the software give you a starting point to make changes and did you finish the settings tuning by ear only or still use more measurements?

[HAL]

Nick,
I used an audio editor to create an impulse and then play it through the dspNexus 2/8 and record the measurement mic response.  Then use the audio editor to look at the results.

It is also possible to use Audio Weaver to create the impulse and play it with the crossover block diagram.  You would still need the audio editor to record and inspect the results.

REW does have a timing pulse output on a second channel to do the same thing.  Have not experimented with it as I have used the first method before.

Did not need to do listening after that as I could remeasure the impulse response and look for correct alignment.  I did listen and as expected the music coherence of the speaker is improved. 

[Nick B]

Thanks for the explanation, Rich. Very interesting to me. I have the Umik  mic, but still need to do measurements with REW. Am using HQ Player to upsample to DSD 256. Amazing technology nowadays...

Nick

[HAL]

Nick,
A program like Audacity that is a free recording program will work with an impulse file to make the measurement and analyze the recording for time offset.  You can play the impulse file and record the mic output.  It is free to download and use.

[Nick B]

Thanks, Rich. I will take a look at Audacity. I think I have REW on my laptop. Whatever software is easier is the one I'll use. Once the measurements are completed, I'll give the results to a friend who promised to help input the data into HQ Player. He helped me set up HQ Player which is complicated software.

I have only tried DSD 256 as he said it's the perfect sweet spot when upsampling. I don't think I have enough processing power to go above that anyway. I an using a MacBook M3 Pro laptop.