2025-08-14 21:00:00
Cross-posted from the BIDA Blog
As we go into winter, we're thinking about infection reduction. Our primary approaches are requiring high-filtration masks at half our dances (which we'll run another survey on in early Fall) and bringing in large amounts of outside air, but we're interested in exploring a variety of options. Two promising candidates are far UVC and glycol vapors, and we'll trial both at our September 7th dance.
This is primarily a logistical test: we won't be able to tell whether these are working for pathogen control (that's what the studies linked below are for). Instead, we're trying to get a sense for how well these fit our particular space, and how practical they would be for regular use.
Far UVC
Ultraviolet light is a spectrum, shorter wavelengths just beyond visual range. The effect of light on viruses, bacteria, and the human body depends very strongly on wavelength, and some kinds of UV are dangerous for humans. The specific range of UV light we'll use, however, is the much safer "far UVC" (~222nm). The risk here is low: with such a short wavelength this light is absorbed by the outer layers of dead skin and the tear film of the eyes, without penetrating deeper the way longer wavelengths do. See Gorlitz et al. (2023) which reviews the risks and benefits of far UVC for pathogen control and concludes that "current evidence supports using far-UVC systems within existing guidelines."
We'll be setting up one Aerolamp, which is built around a Ushio Care222 Filtered Far UVC Module (test report). This is a filtered krypton-chloride lamp, which produces 100mW of UV, of which >99% is far UVC. It will be on stage, aimed horizontally outwards to clean the air above people's heads. If we decide to go further with this method we plan to use four lamps one in each corner of the hall, putting out a total of 400mW (still well within safe exposure limits). When we run our Spark in the Dark dances each of our blacklight fixtures puts out more than ten times this much UVA (~10W each).
One downside of this kind of lamp when used in small well-sealed rooms is that they produce low levels of ozone. In our case, however, the room is large enough that the effect would be negligible. Additionally, since we're bringing in >10k CFM of external air with our two 42" barrel fans, even this negligible amount will quickly be exhausted.
Glycol Vapors
In the 1940s researchers learned that glycol vapors are surprisingly effective at inactivating airborne pathogens. For example, Harris and Stokes (1943) ran an early controlled experiment and found a large reduction in respiratory infections in a children's skilled nursing facility. Unfortunately this early work was essentially forgotten as public health shifted focus, and it wasn't until COVID that people began to take glycol vapors seriously for pathogen control: Gomez et al. (2022), Styles et al. (2023), Ratliff et al. (2023), Sultan et al. (2024), and Desai et al. (2025) all found high levels of pathogen inactivation with glycol vapors.
In the meantime fog machines have become widespread in entertainment, putting out much higher vapor concentrations than required for pathogen inactivation, and the risks have become better-studied. In 2003, the EPA looked into the research and concluded "that there is a reasonable certainty no harm will result to the general population or any subgroup from the use of triethylene glycol."
We'll be setting up a small fog machine, ultrasonic humidifier, or aromatherapy nebulizer by the inward-pointing barrel fan, and we'll use triethylene glycol for fluid. We'll have it on a low setting and aim to put out a little under 60mL over the course of the event and keep the air at around 1mg/m3. While this is a very low level, well below where it would produce visible fog or where most people could smell it, it's high enough for pathogen inactivation.
2025-08-12 21:00:00
In 2014 I wrote up a reference contra dance sound system, with gear recommendations and rough costs. I've been thinking a bit more about gear lately as BIDA has replaced some equipment, and I wanted to write a quick update.
Many aspects have not changed: mics, stands, and cables are essentially the same gear they were ten years ago. The two places where my recommendations would change, though, are the mixer and speakers.
Last time I recommended an analog 10-xlr Mackie. This was a bit of an unusual choice then, since analog mixers were clearly on the way out. But at the time my argument was that the world hadn't yet sorted out what made a good digital mixer, and a simple analog board was a better fit for one that would be used by a range of people of varying skill levels. I'll be more retrogrouch and say that this still wouldn't be a crazy choice today: something like this 11-xlr Mackie ($570) does everything a regular dance needs, is still easier for a range of people to work on, and is simple and reliable.
But I'll bite the bullet and say that for most dances the 16-xlr Behringer XR18 ($510) is a better choice. It's very widely used so people can transfer their skills between dances, you can mix from anywhere in the hall (including behind the musicians as you ask what they want in their monitors, hearing what they're hearing), and you have many more (perhaps too many for people with insufficient restraint) options to modify the sound (compression, more flexible EQ). You also get many more outputs, for special events where it's worth running more monitors. This is what BIDA got in early 2020 (bad timing) after comparing several options.
Note that you do need a tablet or computer to control the mixer. You can either have sound people bring their own, or buy one as part of the sound system. You should probably also use your own router, since the built-in WiFi is notoriously flaky.
On speakers, last time I recommended two full-range powered speakers (QSC K10s) for mains and three small powered hotspots (srm150s) for monitors. I think this was really the wrong call at the time, and I should have recommended four full-range speakers. While the hotspots are cheaper, and their tighter focus lets you keep stage volumes down, they're really unsatisfying for bands with low-pitched instruments.
Speakers have also changed: there are a lot of good options for full-range powered speakers that are cheaper than the K10 (now K10.2, $900). My favorite is the RCF HD10a ($400): clearer sound than the K10, slightly lower maximum volume (but not a problem for contra), much cheaper, and also lighter. I'd get at least four, two for mains and two for monitors, though getting a third as an extra monitor would be nice for the musicians.
Here's how I see costs changing, in constant July 2025 dollars:
| 2014 system | 2025 system | |
|---|---|---|
| Mixer | $680 | $510 |
| Mains | $2,040 | $800 |
| Monitors | $1,020 | $800 |
| Mics | $544 | $436 |
| Mains Stands | $299 | $240 |
| Monitor Stands | $53 | n/a |
| Mic Stands | $180 | $198 |
| Mic Cables | $90 | $85 |
| Speaker Cables | $75 | $76 |
| Misc | $72 | $30 |
| Total | $5,052 | $3,175 |
Overall it's still a significant investment, at over $3k, but it's 37% cheaper (in real terms) than eleven years ago. This is primarily driven by the switch to the HD10A speakers: if we went with QSC K10.2s it would be back up to $5k.
2025-08-10 21:00:00
A major part of my sound is a pedalboard. The key parts are:
Four drum pedals, so I can play drums with my feet.
A few guitar pedals, to play with the sound of my electric mandolin.
A raspberry pi, which lets me combine aspects of my various electronic instruments to make new sounds.
I've been using some collection of equipment for years, and then about a year ago I made it into a more robust and permanent setup by attaching everything to a board. This was a big improvement, but did have downsides:
I used adhesive velcro to attach things to the board, but over time it started to fall off.
A piece of the board is hinged, and I'd used 1/4" MDF (hardboard) for the extra section. This was nowhere near sturdy enough, and had almost completely fallen off.
The board is a bit hard to pick up, because you can't easily get fingers under it. Angling/rounding the underside would help.
I fly to many of my gigs, but my full collection of equipment is 41.3lb, which combines with my suitcase to be over 50lb (so some things go in my backpack, and I've been thinking about lighter suitcases).
Relatedly, it would be great if I could use some of my 50lb limit for clothes, toothpaste, etc. Or just carry a lighter bag.
Here's the current setup:
I took the whole thing apart, weighed everything, and identified a few options for saving weight:
My four Yamaha KU100 drum pedals are 2.7lb each, of which 1lb is a big metal plate. This adds strength and stability, but since I'm already attaching to a wooden base that's not needed here. So I can save 3.8lb by removing these.
I include DI boxes in my setup, so I'm not asking each dance to provide me with five DI channels. I use Radial PRO D2 DIs: solidly built, but overkill here. The pair is 3.3lb (755g each); switching to four Whirlwind IMP2s (1.8lb; 208g each) saves 1.5lb.
One of my pedals is a BOSS OC-5, which lets me drop the mandolin down an octave, but I really don't use this enough to justify bringing it with me. Losing this saves 0.9lb.
Part of the padding I use in my suitcase is an old yoga mat, which turns out to be quite heavy for how much padding it provides. Switching to foam sheets saves 1.5lb.
The base can be cut a bit smaller around the pedals. I'm guessing this saves about 1lb.
The power setup is overbuilt, especially a heavy duty 0.8lb 4-way octopus splitter. Reworking this should save another pound or so.
I used four strategies for attaching things to the board:
In cases where something used a removable bottom plate with standard screws, I removed the bottom plate and used longer screws to attach through the wooden base. I used the bottom plate as a template, and started holes using a nail set as a punch:
I drilled holes through from the front, and then countersunk from the back.
In cases where screws weren't obvious sizes, keeping me from finding longer ones, I drilled new holes through the bottom plates to attach them to the wooden base.
To support inserting the screws I drilled holes through from the other side, large enough to fit the heads.
For three things I wanted to stack on top of other things (two pedals and a DI) I used higher-quality adhesive velcro (3M Dual Lock). I think there's a good chance this will fail and I'll need to sort out something else.
For small things I drilled holes through the base and used zip ties.
I also (as with last time) used a zillion zip ties to keep the cables from being a mess. Possibly I should have used cable sleeves for some of this.
It's also hard to see, but I used a router (thanks Rick!) to round the bottom corners. It's much easier to pick up now.
Here's what it looks like:
And attached to the keyboard:
It now weighs 32.0lb, and 44.2lb in the case (9.3lb in weight savings). While I haven't used this at a gig yet, I think this fixes all my issues!
2025-08-04 21:00:00
I'm on various mailing lists, and the archives are a trove of niche knowledge. A dance calling list I'm on is considering making archives subscriber-only, to keep AI bots from snarfing up this data. But I think this harvesting is overall a good thing.
People have a range of motivations in posting to lists, but a big one is sharing information. For example, someone asked a dance with an 8-count swing followed by an 8-count chain. I replied to warn them at the form has changed and this no longer works well: this bit me back when I started calling, and I want to warn other new callers.
I have a few audiences in mind in writing:
AI systems add another way this information can spread. It's increasingly common for people to ask an LLM instead of a search engine, and when they do I'd rather they get good answers. Excluding the archives from model training would do the opposite of what I want.
There are definitely downsides to querying today's models, similar to asking a person who has read a lot but doesn't remember where they read anything, and sometimes invents something plausible instead of saying they don't know. I think this is likely temporary, however: combining the best of models and traditional search is a problem a lot of people are working hard on solving.
So, on balance, I think it's better to keep the archives open to all, including future LLM-intermediated readers.
(I also think AI is in general moving too quickly for society to respond well, and has a significant risk of getting us all killed. While I could see pushing against AI wherever it comes up, as part of moving a big societal "yay-AI; boo-AI" lever in the direction that slows it down and gives us more time to work out solutions, instead I've decided to take things case by case, thinking about effects each time.)
2025-07-31 21:00:00
One strategy we often find helpful with our kids is the "do over": something didn't go well, let's try again. Two examples:
Nora (4y) can't yet cross streets on her own, but we're starting to practice. Walking to a farther park, a walk where we often practice, she asked Julia "when we get to the little street can I cross it"? Julia said "we'll need to check in when we get there". But Nora did not check in, and 'practiced' on her own. Even though this was on a tiny street, this was still really unsafe and is something she very much needs to not do. I caught up, spoke to her firmly, she burst into tears, I walked her back, and we did it over together. As soon as she had the chance to demonstrate doing it correctly she cheered up dramatically, and then we had a good time at the park.
We're in a hurry to get out the door and I put Nora's coat on her. She bursts into tears: "I wanted to put my coat on myself!" I ask "should we do a do over?" She says yes, I take her coat off, she puts it on, she's happy.
These sound very different, but they're really two sides of the same learning process. In first case I wanted Nora to learn something. If I had just spoken sternly to her about not crossing streets solo I don't think it would have sunken in as well. Making it inconvenient, getting to the park later than if she'd done it the right way, having the time walking back to reflect on her error, and then doing it the right way, all contributed to taking it seriously and learning.
The second case is much more minor, but it's just the other way around: if I'd just apologized to Nora and said she could put her coat on next time I would have learned less, and she would rightly be less confident that I would actually follow through.
I think this is a neat symmetry, but to be fair it's not always why we do the second category of do overs: sometimes we're just trying to resolve a meltdown. For example, say there's a miscommunication where it turned out the kid had a very strong preference but we didn't ask and they didn't tell us. Sometimes a do over would be about practicing what good communication would have been:
Nora: I didn't want my cereal in this bowl, I wanted a large bowl!
Me: Would you like to do a do over?
Nora: Yeah
Me: If you want your cereal in a specific bowl you'll need to make sure I know that.
Nora: Ok
Me: Should I get you some cereal?
Nora: In a large bowl!
Other times, though, the kid is too fragile (perhaps very hungry), we don't have time, or I'm being a lazier parent. In these cases the do over is just a way to calm them down (and clear the way to not being so very hungry):
...
Me: Would you like to do a do over?
Nora: Yeah
Me: Should I get you some cereal in a large bowl?
Nora: Yes!
This version is still helpful; the kid ends up happy and fed. You don't have to take every opportunity to model ideal communication. It's not always clear in the moment what ideal communication would have been, especially as kids get older and interactions get more complex.
With all of these different applications of do overs, a key thing that I like is that it quickly breaks the bad pattern and replaces it with a better one. You're not digging into what should have happened, you just jump back and try it again.
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2025-07-29 21:00:00
I fly to a lot of gigs, and I check a bag with my pedalboard. Airlines generally limit checked bags to 50lb, and I'd like to be able to get as much stuff as possible into that 50lb; how light can a suitcase be?
I'm currently using an old Samsonite clamshell that I found on the side of the road. I like how sturdy it is, but it weighs 12.2lb. That's almost a quarter of my 50lb budget allocated to the case!
It looks like a cheap modern hardshell would be 9lb ($70), saving 3.2lb. That's pretty good, but can we do better?
I did some looking for light options, and as far as I can tell Samsonite is the company making the lightest options by a good margin. They're also very expensive, with current-generation options going for $600 at full price. Here are the options I see under 7lb that would fit my 23.5" x 17.5" pedalboard:
Samsonite Lite-Shock 75cm, 5.5lb ($403)
Samsonite Cosmolite 3.0 Large Spinner, 5.8lb ($330)
Samsonite C-Lite Large 28", 6.3lb ($355)
Samsonite Firelite 28" Spinner, 6.7lb (discontinued)
Samsonite Proxis Medium Spinner, 6.8lb ($439)
These are all pretty expensive, but I'm going to keep an eye out for used ones. Any other models I should be checking for? Should I be worrying that these suitcases are giving up durability for weight?