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A semi DIY curiosity: Seas Excel Nextel 8 inch with Seas DXT

Doenerkunde

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Around 8 years ago a friend of mine bought a pair of speakers that supposedly came from the experimental laboratory of Joachim Gerhard. The speakers he bought were based on the cabinet of the big 2 way speaker Sonics Arkadia. The Sonics Arkadia originally used Seas CA22RNX eight inch woofers and Seas 27TDFC tweeters.

There was a long thread on a german forum in which a user pimped the cabinet and developed new crossovers for his Arkadia that contains many photos for the ones interested: http://www.hifi-forum.de/viewthread-205-485.html

The experimental version my friend bought contained a Seas Excel Nextel woofer and a Seas DXT tweeter. Very interesting! Unfortunately „out of the box“ they wouldn´t play right (basically the crossover parts were glued to the back of the cabinet and it was clear that it was an experimental setup). The friend did me a favor and I wanted to thank him by helping him to get the speakers to play right. After some research I found out that the well known german DIY speaker designer Udo Wohlgemuth offered a kit that used the same drivers in a similar cabinet format called Excel 22 DXT. I bought the plans and crossover parts for my friend and he built and installed the crossovers but somehow lost interest. Fast forward to today I did the friend a favor and he gifted me the speakers.

I started this thread to motivate myself to get them done. I have no background or experience in DIY, so this will likely be a slow process. I have an Umik-1 mic and plan on doing some rudimentary measurements „as they are“. I will try to get the plans from the friend in the next week or so. The total price paid for the pair of speakers, the building plans for the Excel 22 DXT kit and the crossover parts were around 500€. Today one of the woofers costs around 330€.

Any kind or motivational words are appreciated! Please be patient, since this project will most likely be moving at a slow pace.

This is the pair I got compared to the Elac DBR62. Pretty big speakers!

IMG_20241207_124551705_HDR.jpg
 
They seems nicely made! Excellent drivers. I’m wondering how well they integrate though. Tweeter should be crosses as low as it would permit.

So given that you have a box, the drivers and crossovers, what is needed to get them “done”?
 
They seems nicely made! Excellent drivers. I’m wondering how well they integrate though. Tweeter should be crosses as low as it would permit.

So given that you have a box, the drivers and crossovers, what is needed to get them “done”?

As far as I remember they wouldn´t "play right" with the crossover from the Excel 22 DXT kit either. Might be due to error in building the crossover, faulty drivers, leakage of the cabinet (screws went diretlly into the MDF, some were somewhat loose) or that the substitute crossover I picked is not as suited as I would have thought. Also the tweeters are not completely flush, but stand out like 1mm.
 
Hey guys, today I performed some rudimentary measurements, that were nontheless very enlightening.

First I compared a nearfield in room measurement of the Elac DBR62 and the left modified Sonics Arkadia:
Elac vs Sonics FR.png


Looks pretty good! Treble is a little bit hotter than with the Elacs, but this should be no big problem.

Next I looked at distortion for both speakers.

Elac DBR62s distortion:
Elac distortion.jpg


Modified Sonics distortion:
Sonics distortion.jpg


Also looks good. Distortion in the midrange is decidedly lower than with the Elacs.

Next I did some ultra nearfield measurements of the drivers of the modified Sonics:
Sonics crossover.jpg

The crossover point matches the specs, so no problem here either.

Than I measured the right modified Sonics Arkadia against the left speaker and the problem became appearant:
Sonics right vs left.jpg


Tweeter and woofer of the right speaker are wired out of phase! Should be easy to fix.

In the meantime I also got the crossover plans from my friend: The crossover in the speakers was developed by Udo Wohlgemuth and the kits name was "Excel22DXT".

I´m very confident, that I will be able to fix them. This is a real experience of success for me. Eight years ago, when my friend bought the speakers there was no way for us to determine what went wrong. But now, thanks to ASR I bought a UMIK mic and was able to see what is wrong within 20 minutes. I will keep you guys updated.
 
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Nice work! If you intend to continue development, I would suggest looking at off-axis behavior next. Directivity is likely to be more consistent with a lower crossover. This example used circa 1800 Hz:
 
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