***July 18, 2021 - July 24, 2021 Weekly Show, Tell, and Critique***

Started 3 months ago | Discussions thread
Dak on cam
Dak on cam Senior Member • Posts: 6,380

Birddogman wrote:

Dak on cam wrote:

We've seen embarrassingly little of it. the bass speaker is

Whew! I'm very glad to hear that. I know the news always makes things look worse then they really are, but you had me worried.

The scary things to me about your floods is that (unlike here, where the endless new development is often encroaching on natural places and people like to build houses right by creeks, etc) most those towns and structures have been in place for centuries and are only now getting destroyed by flood waters. That can only mean that the climate really has changed for the far worse in recent times.

4Ohms rather than the 8Ohms the crossover I used had been designed for. Dug out some bipolar capacitors I had from previous experiments, entered simulations into Spice, unwound some inductance until it fit,

Huh?? Lost me there, buddy....

Oh, it wasn't photography jargon.  Putting it back into comprehensible language: loudspeaker cabinets tend to contain more than one speaker, separated for doing different jobs (bass notes need to move a lot of air and thus need large cones for moving them, and those are unsuitably heavy for moving at the speed of treble notes and would also cause the treble notes to be mainly audible in only a small sideways region because of the large cone: it's actually a wave phenomenon like out-of-focus bokeh).

So you need to split the workload requested from the amplifier into jobs for the different speakers.  That's the job of frequency crossovers.  Those are mostly built from capacitors and inductances which at the lowest level work by temporarily storing energy in electric and magnetic fields.

Since they are working with the output from the amplifier (which in this case can be 100Watts) and need to be able to store energy for a bit of time in order to do something different depending on what kind of frequency (high note or low note) they are dealing with, those things are pretty large by themselves.

An inductor consists of a whole lot of coils of thick copper wire that are insulated from one another by a layer of hard lacquer.  As I am a cheapscape and needed to create a crossover working with different speaker characteristics than I had planned for, I made my own different-sized inductor by breaking apart an existing one and reducing its windings to probably 40% of what was there before.

In short, I indulged in a huge mess of stuff I was nominally qualified for messing with (even though I certainly don't have a lot of practice with it), deriving the grim satisfaction of a tinkerer (a lot of people experience similar satisfaction working with older motorised transports: those are affectionally called "Schrauber" in German, "screwers").

Finally getting what I consider more or less acceptable sound, I now have found some buzzing with low notes.  Locating the culprit (a mechanical rather than electrical problem) is a nuisance.  I've just applied a bit of glue to the rim of the bass speaker dome (the spherical thing in the middle of typical big speakers) in the hope that it's from there.

So the only thing that may have taken damage in the past week with awful weather is my ego (stuff never works out quite as planned).  Right now it's actually sunny outside.

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