Monthly Archives: September 2016

All Your Anechoic Chambers Belong to Me

]Went out for a very brief first ride today. Only 9 miles!

So…anyone know of an anechoic chamber in the tristate area that I would be allowed to use–even if I have to do an all-night session? I have several calls in, including one to my alma mater, but no dice so far.

The reason? I need to take some exceedingly accurate measurements in order to design my crossover. Now, I could do them by correcting for reflection from the floor and ceiling, but that wouldn’t be as much fun, would it?

measuring_a_diffuser_in_an_anechoic_chamber

Personal: Finding the Right Cap

As you can see from the below my hobby while not able to ride has become audiophilia. Rational audiophila, but audiophilia nonetheless.

I’ve decided to try my hand at developing an active triamped system using DEQX as a room correction system/electronic crossover (actually, the speaker is biamped and I’ll be running dual powered subs, so in essence it is a triamped system). I’ll write more about what this means, why I’m interested, and how I chose DEQX in a later post–in fact, I plan to document the entire process so that it can be replicated by someone equally naive. It should be interesting, as the hardware comes with a 178-page manual, and I also have to learn about DACs and a lot more details about amplifiers and speakers than my current “that sounds nice.”

I reserve the right to go back and edit these posts, as I’m likely to convey a lot of misinformation as I go along. In fact, I definitely will be coming back to these and cleaning them up so that it becomes an effective guide.

IMPORTANT NOTE: Before I scare you off DEQX forever, you should be aware that a) basic setup, which provides truly astonishing sound, is simple even for the technically disinclined; b) a dealer can set it up for you; and c) you can get a free 3-hour setup session via Skype if you prefer to take a middle route. I am just going the absolute hardest route–setting it up myself and using all of the most advanced features–because I find it entertaining.

I also plan to give some plugs to the various techs and businesses that are helping me figure this out and suffering through my dumb questions.

For now, though, I need a capacitor. Why? Regular passive speakers have a crossover that divides the signal from the amplifier so that the high frequencies go to the tweeter and the low frequencies go to woofer. The crossover acts as a natural protection against the amp frying the tweeter (the woofers are, apparently, more tolerant). Because active amplification means that I’m connecting the tweeter and the woofer directly to the amp, the tweeter needs some form of protection. And that protection takes the form of a capacitor.

So, capacitors (which store electric charge) come in all different values, measured in microFarads. I needed to figure out what size to get. According to the DEQX manual, I needed one that falls 2 octaves below my crossover point (the point where the frequencies are divided into high and low for the tweeter and the woofer), which in this case is 2800 Hz. Octaves are not linear, instead there is a 2:1 relationship. So 2 octaves below 2800 Hz is 700 Hz (divide 2800 by 4). (One octave below would be 2800/2 = 1400 Hz, and three octaves below would be 2800/8, or 350 Hz).

Then I had to get my tweeter data sheet to identify the resistance in Ohms at 2800 Hz–which turns out to be very close to 8 Ohms.

Now, plugging that into this handy formula:

C=1/(2*pi*f*R)

C=1/(2*3.14*700*8)= 2.84 x 10^(-5) = 28 uF

So I need a 28 uF capacitor. That value isn’t common, so I chose a 33 uF capacitor, which I purchased from the nice Canadians at PartsConnexion. Voila!

(Obviously this is a 6.8 uF capacitor, not 33 uF).

Alternatively, you can use this website to calculate the required capacitance:

http://www.claredot.net/en/sec-Sound/high-pass-cross-over-6dB.php

Good times were had by all. Now I have to learn to solder.

Executive Summary:

  • In an active biamped or triamped situation, a protective capacitor between the tweeter and binding post is desirable
  • The correct capacitance is determined in X steps: 1) Get your tweeter data sheet and find the resistance in Ohms at the crossover point you choose; 2) find the frequency that is 2 octaves below your crossover point by dividing the crossover frequency by 4
  • Plug it into the website above
  • Buy two from PartsConnexion (because they are lovely Canadians)

To be continued.

John

Personal: Connecting Cello Stereo Components — The Elusive Fischer 104 Connector

Remember when I said don’t read my personal posts? There are going to be a lot over the next few months as I recover. Just general stuff I’m thinking about.

I have the pleasure and privilege of owning some Cello gear. Cello was a company started by Mark Levinson that sold very high-end audio equipment in the 90s. Many of the components were used in professional audio studios.

For example, here’s the Audio Suite and Palette, perhaps the finest equalizer ever made (I’m a strong believer in the value of tone controls, none of that audiophile short-path pure signal bullshit).

audio-palette

The major problem with Cello gear is that instead of using standard balanced XLR connectors, they used some crazy Fischer connectors because they “sound better” (audiophile bullshit). It’s virtually impossible to find the proper information on these cables, much less get them made.

After extensive research, and some help from my friends at Blue Jeans Cable, I found the correct part numbers. I’m putting them here as a public service announcement so that nobody needs to go through what I did to find these little assholes.

S104A040-80 male with E3104.3/8.7+B strain relief (fits cables up to 8.7mm D).

S104Z040-80 female with E3104.3/8.7+B strain relief (fits cables up to 8.7mm D).

fischer-s104-3-pin

In case you want to make your own cables, you can buy them from Michael Percy at Percy Audio. I recommend Blue Jeans cable though–well made, inexpensive, and no weird superstitious crap about cables and connectors sounding different etc.

Bored yet? I’m making a long list of rides and hikes to do as soon as I recover fully…hoping to get back on the bike by October!

Personal: Injuries and Other Tragedies

It has been quite some time, and there’s a reason for that.

For reasons I’ll get into in this post, I’m going to be using RTC as my personal blog for a bit–in other words, I’ll be posting what comes to mind, even if it isn’t bicycle related. I’ll mark the posts “personal”; feel free to ignore or unsubscribe.

Hopefully I’ll get back to cycling-related content before the end of the year. I see that the daily visitor count has fallen to 5% of the level it was at when I was posting regularly (and where are John S and Anton?).

The good news, I guess, is that I’ve gotten 17 views from Burkina Faso. I’ve heard that Burkinians have an abiding interest in the Catskills, but I didn’t believe it until just now.

First, I sustained a serious neck injury earlier this summer. I’ve had neck injuries before, but this was something truly special. The worst part was that it happened the DAY before a 2-week vacation. So I spent my vacation in serious pain, culminating in a trip to an interventionalist for a steroid injection between 2 of my cervical vertebrae. I appear to be recovering, albeit slowly, but it has been a long 10 weeks.

Now, don’t shoot me folks, but a key learning from this experience has been that physical therapy, at least how it is practiced for your average civilian, is an absolute joke. 15 minutes of e-stim and a nice backrub and some advice on exercises 3 times a week does little good.

I ended up hiring a yoga instructor. She comes to my house 3 times a week and does a world more good than that stinky physical therapist. Literally stinky.

Please note that I do not doubt the overall efficacy of physical therapy–if you’re a pro athlete or a post-stroke patient and get hours of therapy a day–but for the average person, not so helpful.

The worst thing about this experience has been the drugs. For the first time in my life, I’ve had the pleasure of meeting Mr. Percocet and Ms. Gabapentin. For the first 4 weeks, I was downing the Percocet at the maximum recommended dose–4 tabs a day–just to gain marginal control of the pain. And this despite the miserable gastrointestinal side effects that you can read about in your free time.

But the worst thing about the Percocet didn’t turn out to be the drug itself…it was the problem of getting enough to actually control my pain. I’ve never had chronic pain before so I didn’t realize what pain patients go through to even get treated appropriately. They’d give me a prescription that would last 10 days, and then I’d have to go back for more–and damn do they make you feel like a drug addict for asking for more. It got to be such a mortifying, difficult thing that I attempted to massively reduce my dose of narcotic pain medications and augment with massive doses of naproxen.

Those of you who know me know that I’m a scientist and I work in the pharma industry. So I’m not naive. I know what megadoses of naproxen do to your gastrointestinal tract. In fact, if you look up the stats, you’ll see that NSAID-induced GI bleeding kills more people than…well I don’t remember the actual statistic, but it kills a lot of people. Indeed, after some time on that regimen I was burping up blood. Just a little. Good times.

In the current climate of suspicion about narcotic drug use (which, I guess, is justified) and the heavy penalties levied by the government on physicians whom they deem to be inappropriately prescribing such therapy, physicians would almost rather have a patient either a) live in severe pain or b) suffer serious injury or death from taking over-the-counter medications–because at least it won’t be their fault. I mean, seriously, NSAIDs are dangerous–if the FDA were making the decision today, they’d never have made it onto the over-the-counter market.

I just wanted to get that on record so that if I croak from a GI bleed my relatives will know who to sue 🙂

In any case, I am recovering and I’m back to 8-hour workdays…no fun times yet (meaning hiking, biking, or camping).

Moving on…during this period–in fact during the initial 2 weeks of serious pain, my Rhodesian Ridgeback started acting weird. She stopped eating her food and looked a little bloated. So I had the pleasure of taking her to the emergency vet at 11:00 at night while in serious pain. Emergency vet tells me she has a giant mass in her abdomen, which I thought was weird because even 3 days prior she was running around chasing wild turkeys like a puppy. I had to wait a day to take her to the emergency surgical center–1.5 hours away in Albany, New York because I had to go in for the aforementioned steroid injection in my spine (which was a bigger deal than I thought it would be).

The day after my intervention, I took Pandora to the surgical center, where they basically had to gut her to get the mass out. There were 2 things it could have been: a hemangioma (which is benign) or a soft-tissue sarcoma (invariably fatal). The surgeon I spoke to, who was kind enough to talk to me as a fellow medical professional, told me that her impression of the mass was that it was a sarcoma.

Four or five days later, the pathology results came back, and, guess what? HEMANGIOMA! We’re now weeks out from the operation and Pandora is a new dog–even though she was out chasing turkeys only a few days before she started manifesting serious clinical signs, it is obvious in retrospect that it was affecting her for a long time. She’s also slender and sleek–having a 10-lb hemangioma removed is one way to quickly lose weight, I guess.

Finally, all of these issues have given me the opportunity to grow a truly wicked beard to complete my mountain man look. Now, I just need to figure out if I’m the JD Salinger of medical writing (because of my splendid countryside isolation and love of donuts) or the Hunter S Thompson of medical writing (because, you know, drugs and guns).

hunterthompsongun

So…that’s my news for now. Oh wait–some good professional news–I’m doing some seriously cool stuff on Zika virus! The kickoff was today.

In any case, I’ll be writing posts on general stuff that interests me for a few months. You can skip it or read it. Let me just say that during the vegetable phase of my illness I spent many hours reading about audio equipment, and you are going to see the fruits of my research right here on RTC. Bear with me and we’ll get back to bicycle and outdoors content…soon? Hopefully?

John F