Tag Archives: impedance

2013_10_03 (R) The Sound of Music

Today was a bakery day for Linda, so I was left to my own devices.  I let the Garmin Express update run all night last night.  When I checked this morning it indicated there had been an error, so I downloaded the 2014.20 map update, again.  It took another 3+ hours, again.  It said it downloaded it so I installed it.  It said it was “done”, but that the “update failed.”  At this point I have no idea if my maps are up-to-date or not.  We have had the Garmin nuvi 465T GPS unit for quite some time now, and I really like it.  I also liked the desktop docking software that came with it, which always worked fine.  The replacement desktop docking software, Garmin Express, is simpler to use but doesn’t seem to work very well.  A quick Google Search yesterday indicated that lots of other folks have apparently had issues with it as well.

In terms of getting ready for the open house / warming on Sunday, I am down to what builders call a “punch list.”  I don’t know the origin of that term, and yet it seems somehow appropriate.  (I always supposed that it came from the idea that the workers were going to “punch these things out,” but that doesn’t make any more sense than the original phrase.  The other day Linda made some final selections for artwork for the small bedroom, so today I hung those up.  That was one of the items on my punch list.

One of the things that came with the new house was built in speakers, two in the main floor hallway ceiling and two in the Florida room (library) ceiling.  The speaker wires for these all run to a basement wall opening where the previous owners had their audio entertainment equipment.  We have enough else to do without completely re-wiring the house, so we put some of our audio equipment in the same spot.  Linda had asked that I try to wire up the audio system so we could have music on Sunday; another item on my punch list.  With the house mostly ready, I decided to see if I could get the built-in speakers wired up, along with a pair of our freestanding ones.  I used my volt-ohm meter (VOM) to check for continuity and resistance to figure out which wires did what.  As part of the harness wiring harness, there were also two pairs of wires with both ends free that I could use to wire up the local freestanding speakers.

Measuring DC resistance through a speaker does not tell you what its rated impedance is as impedance is a characteristic of a device when AC (alternating current, from an applied alternating voltage) flows back and forth through it.  It does, however, give you some idea of what’s at the other end of the wire pair.  The amplifier in our receiver is designed to drive two sets of speakers (A and B) and prefers not to see less than 8 ohms impedance at the connection terminals.  There is a switch on the back, however, that allows you to select 4 ohm or 8 ohm speakers.

Connecting impedances in parallel results in lower total impedance and connecting them in series adds the impedances.  The pair of speakers in the hall has a volume control, and the pair in the library also has one, and it appeared that turning them from one extreme position to the other increased the DC resistance slightly, but not that much.  So, just to be safe, I decided to wire one speaker from the hall in series with and one from the library (think “left speakers”) and then repeated that for the other pair (think “right speakers”).  I connected the CD changer to the receiver, started a CD, and voila, the sound of music…everywhere!

The main (basement) speakers were too loud relative to the ones upstairs, so I connected the built-ins in parallel, which resulted in more power going to them relative to the main speakers.  It also allowed the volume control in the hall to control both of the hall speakers, and only those.  Ditto for the volume control in the library.  I also switched the amplifier to work with 4 ohm speakers instead of 8 ohm.  The name of the game is impedance matching, and if you can’t match impedances choosing a higher impedance load rather than a lower impedance one is generally better for the amplifier (up to a point).

Tom and Tom from TOMTEK HVAC showed up as scheduled around 3 PM to finish the work on the hydronic heating system.  This time they had all of the parts they needed: new burner cone, igniter, expansion tank, expansion / quick fill value, shutoff value, fittings, and copper pipe to re-plumb the pressure relief discharge pipe from the domestic hot water tank.  I tried to check in on the progress of the work periodically without getting in their way and slowing them down.  I always do this when anyone works on anything in our house as I want to know as much as possible about the system.  They finished up around 6 PM.  While we did not anticipate the furnace / hot water system needing this much work, or this soon, it was fortunate that we had TOMTEK come out for a “routine maintenance” visit and discover/fix all of the other problems as a result.

When Linda got home we were both too tired to even go out, so we had the left over “sloppy Joes” from yesterday’s dinner along with fresh fruit.  This particular recipe used textured vegetable protein, known as TVP, instead of the soy crumbles she normally uses.  The two products are very similar in taste (nothing strong or characteristic) and texture (kind of like ground beef) and work well in “mock” dishes like chili, sloppy Joes, or anything else that would normally call for ground beef as an ingredient.  These products do not work well, however, to make mock “hamburger” patties; there are other products made to directly satisfy that market.