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InDIYana 2022; "Missing Link" theme announcement....

InDIYana 2022 theme challenge:

“Missing Link”
Chuck and I (Ben) decided to go a different direction this year. I suggested picking some interesting less than perfect drivers, designing the cabinet along with the bass tuning, taking a full set of measurements of the chosen drivers in said box, and unleashing the competitive attendees on a xover challenge alone. Basically, we provide the front-end, amplifier, and the speakers. The entrant brings the xover. (Entering the challenge is still not required.)

Since the unfortunate passing of Rick Craig and Jeff Bagby; This is the first time this kind of challenge has been done since Jeff won (tied, along with Dennis Murphy) at the event Rick hosted all the way back around 2000 (At least to my knowledge). I felt it was time we gave this a try again being that it has been that long. We also have not tried this challenge at InDIYana before. Software and tools available are vastly different than they were 21 years ago, especially since Jeff dropped his software suite in about 2005.

I vetted the idea with several people that typically attend, and the idea was universally accepted. It gives a lot of options with an open xover platform. The lesser experienced or thrifty builder would have an easy go of things with all of the info supplied. While purchase of drivers or building cabinets is not required, builders are allowed to do so.
Cabinet dimensions will be provided should someone want to give that a go for audible personal voicing. Drivers total runs about $250/pair. This is not an immense outlay of money, even well under past allowed theme costs, and the drivers are not bottom of the scale in performance. Cabinets are relatively simple, and of modest size. You are welcome to bring the cabs you build to the event to show them off, but for the competition the cabinets that I have built will be utilized.

Drivers are to be the Dynavox LW6004HR-N kevlar honeycomb woofer and the SB Acoustics SB29RDC (SB29RDAC is identical save for an aluminum faceplate).

The provided woofer alignment is about the best I can do. The driver has a somewhat weird set of specs. I used woofer #2 for the larger Vas, as the other will likely break-in a little towards it.
It's high enough Qts to run sealed, but it didn't get low enough extension for me.
Therefore, a vented-stuffed box comes out better, but I had to cut back on the box volume to keep the Xmax in check. I think a 15 ltrs 7" 2-way with extension to about 40Hz is reasonable. I also added 0.4 ohms for xover DCR into the box sim.

14.5” x 10” x 11.5” HWD external. I used a 1" thick stair-tread for the brace (solid, no holes) about 2/3 the inside depth, positioned at 7.5" on center inside height, about 3/8" below the port. Since the port and brace are about the same length, I added a hardboard brace across the end of the port to tie in the top, port, and brace. Port exit has a 1" roundover, and is a 2.5" D (grey elec conduit) x 7" long. Lower cavity is well stuffed.

I took the loaded cabs down to Coop’s place (thanks, Coop!) for a full set of measurements in his lab/barn. We even went through a second set of taking measurements because Coop felt something was off. Gating measurements allows good Impulse Response with valid data down to ~300Hz in his setup. Coop used ARTA/LIMP for the data retrieval. There is a read-me file for understanding the files’ nomenclature included in the .zip file that Coop has provided. I have included all of my data as well in the file, as well as the applied box model from Unibox.

I know normally the theme is announced in July before MWAF and Tent Sale, and while I would have liked to do that, the drivers Chuck and I wanted to use were on back order awaiting arrival. They finally arrived on my doorstep the first weekend of August, and I knocked out the cabinets the following week as I had vacation time. I was able to get them down to Coop’s on August 28th for the first go around and then again on Sept 11th for the further task of bettering them. So as you see, there has not been much time left in getting the information presented and announced to the masses.

The cabs have 4 binding posts present to the rear to facilitate connections. Due to time frame and how fast we go through the theme challenge, we highly mandate that banana plugs be utilized for these points of contact, and that the xover boards brought by the entrant be fitted with banana jacks for the inputs from the speaker cables. The components must be mounted to a board of some sort, and connections must be solid via solder, barrier strips, wire nuts, euro-blocks, spring terminals, or lever nuts, etc. There is to be no flaky alligator spaghetti type of connection, or cardboard as mounting structure. This is to prevent accidental misconnection, shorting of contacts, or loose or other connectivity issues and make sure the entrants have the fairest chance in the competition.
As a safety measure, there will be a 100uF polypropylene capacitor in series with the tweeters to prevent accidental overdrive should something occur or be miswired by the entrant. Schematics of the entrants’ xovers will be required for perusal, and the entrant is to plug in their own xovers during the challenge.

On a personal note, I'll be making my xovers fit an 8.5" x 7" board, and that should be a good enough size for the challenge. Yes, I will also be entering, and I feel me purchasing the drivers and building the boxes to be measured gives me the right, with no particular advantage over anyone else as I will be using the same set of data.

There is no dollar amount limit on the xovers for this challenge. Use what you like, or as many parts as you like! While the drivers have been chosen, and the measurements taken, I want it to be clear that this is not Iron-Driver. We will not be taking measurements of the finished system except for matching the output levels between entrants via an RTA on a running Omnimic or other program/software and gear. Judging will be conducted via a show of hands as is the norm. In the event of a tie of votes, the xover's visual presentation will decide the winner if a recount of the 2 options still results in a tie. Should there be similarities in xover networks entered, Chuck and I may lump entrants into sectors for a bracketed system of judging as done prior.

As usual, we are targeting the month of April, 2022. More details will be presented as the time gets closer as to where and what days.

Let’s hope that Covid is taking a backseat by then, and we can all have a very splendid time at InDIYana 2022!
I hope to see you there/here.
Wolf

PS- I will still plan to have the .zip file uploaded to the event website for download in the next week or two at the latest, maybe this evening depending. It is an 18.5MB file size as compressed. Fortunately, MAC allows that file size, and I can also upload it here as I have done.

DanP
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Comments

  • Side-note; I have build photos of the cabinets, but I have not pulled them from the camera yet. The 8.5" x 7" boards will fit inside the boxes with a removable baffle as I have done. However, for the contest, all xovers must be external for connections.

  • Oh- I did not relieve the back side of the baffle for the woofer as it seemed open enough to not cause any interference.

    I really like these CMC/Connex locking nanner-jacks too. No more cracking/splitting of the locking-style plugs!

  • sorry I will not be attending this one- very cool contest idea !

  • So there's a 100 UF cap on the tweeter regardless? Were the measurements taken with or without the cap? Did I miss the driver locations on the baffle and the round over?

     John H, thanks to JP I did get that email
  • Cool idea Ben

  • I would cut a 2.5" diameter hole in the middle of that internal brace to prevent a possible dual chamber effect. Nice contest idea.

  • Neat concept. I have questions on the measurement data, but I'll keep to myself and let the entrants work out whats going on.

    I think it would be cool to see this competition completed in a "black box" method, so that there are no preconceived bias derived from the visual appeal of the crossover, topology or component selection. You could always just run a quick impedance sweep before plugging in to make sure the crossover won't short out the equipment.

    6thplanet
    I'm not deaf, I'm just not listening.
  • Measurements taken without the 100uF. It will be present in the competition. Baffle placement is in one of the folders in the image with the cabinet drawing, as well as posted above. The cap should be far enough below the xover to not wreak havoc.

    The 3" wide area is plenty to breathe between sections, but you are welcome to cut holes if you want to. I was trying to make it simple.

    There is not time for the impedance sweep in addition to everything else. Ben (Coop) measures FR for a living, so if he's confident in the data, so should you be. This was taken with an Earthworks mic, and the amp was a Crown D75 with a Focusrite Preamp/Interface.

  • That's a cool looking polar turntable. Is there a construction thread or dimensional drawing available on this? I'd like to build one of these.

  • It's still a work in progress, AFAIK. Coop hopes to fully automate it.

    4thtry
  • I think dcibel has a great idea regarding the black box method.

  • Yup, all xovers should be in a shoe box. Then we can discuss how much better Sketchers sound compared to Adidas.

    dcibel4thtry
  • I also love the idea of having no idea if the crossover is a bunch of electrolytics or gold oil virgin unicorn caps.

    jr@macrjj454thtry
  • edited September 14

    @6thplanet said:
    Yup, all xovers should be in a shoe box. Then we can discuss how much better Sketchers sound compared to Adidas.

    Nike's sound the best I hear ;)

    Silver1omo4thtry6thplanet
    I'm not deaf, I'm just not listening.
  • edited September 14

    Sadly I won’t be able to enter due to geographical restrictions, but I’ll still be working up a crossover.

    How big is the room?
    How are the speakers going to be setup? Eg. Listening distance, toe-in or not, distance to walls.

    Also, it will be fascinating how the winning entry will measure on the full CTA-2034 method…

    Best regards

  • Dezzar over on PETT has talked of trying to host a DIY event down under. Not that it's going to happen, but it would be cool if you Aussies played along too!

    I don't even know the particulars of the room as nothing is set in stone. Toe in is up to the designer, but mine will be towed in. Why listen to a ring-dome off axis when it's generally not as good? Wall distance will be greater than 3' all around.

    I guess I don't know what CTA-2034 is?

  • edited September 14

    @Wolf said:
    I guess I don't know what CTA-2034 is?

    Modern measurement standard. "Spinorama", VituixCAD, this thread:
    https://diy.midwestaudio.club/discussion/1509/ansi-cta-2034-a/p1

    I'm not deaf, I'm just not listening.
  • Well, the reason we took the polars was so this could be modeled. Spinorama, I am familiar with.

  • You really need full 180 degrees for proper representation of sound power, but won’t affect the shape of the curve much for crossover design purpose…or will it ? ;)

    I'm not deaf, I'm just not listening.
  • edited September 15

    I think shipping an x-o in could work. I probably have enough parts to build a pair for myself and someone else.

    What's the rule on charged coupled caps?

     John H, thanks to JP I did get that email
  • If you wanna charge-couple, you have my blessing. Just make sure the battery is on-board.

  • First x-o done but dam can't listen to it...

    rjj45Wolf
     John H, thanks to JP I did get that email
  • Brown noser. =)

    Wolf
  • Thanks Ben, that’s clears it up.
    I’ve downloaded the data files to my phone but not yet had a chance to load the curves into my computer modelling software.

    I’ll have a go at designing for 4pi radiation ( full baffle step compensation )

  • Shoot John, you may be faster than Madisound's LEAP service! Maybe you should start a side gig.

    rjj45PWRRYD
  • Haha, I may need something as I gave notice last week. But on topic it's interesting to think about how do I change the x-o after listening to it.

    In this case I also have to think about how do I change Ben's design, certainly more real wood :)

    6thplanet
     John H, thanks to JP I did get that email
  • So, John, do you plan to order the drivers and build a pair for listening? Or do you already have these drivers in stock?

  • I'm not planning to order and build, I've got enough 2-way box speaker designs.

    I would like to spend some time listening to Ben's speakers with my x-o. Maybe Friday night? The rising response after 10K is something I want to hear. It's still prevalent at 20 degrees then flat at 30 degrees in my x-o. I could add an a-b switch to the shoe box.

     John H, thanks to JP I did get that email
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