What does the inductor do?

Rex81

Could somebody please explain (in layman's terms) what the big inductor does in SDAs, both electrically and sonicly? Thanks!

pitdogg2

Spins down all the frequencies to a certain frequency to which the gauge of wire plays a part. Also plays a part in the ohm value of said speaker.

westmassguy

If you're referring to the large value spool Inductor on the 3rd-5th generation SDAs, it's purpose, is to allow the dimensional woofer(s) to operate in tandem with the stereo woofers, starting around 150 Hz. It is connected via the Sub-Bass Drive Circuit, and reaches its full effect, depending on the model, between 50 and 75 Hz.
Without this circuit and Inductor, the dimensional woofer(s) would be out of phase with the stereo woofer(s), and essentially cancel each other out. In the 1st and 2nd generation, they added sub-bass woofers to compensate. This is explained in more detail in the SDA Handbook.

Rex81

Thanks westmassguy, this helps. These are 1986 SRS 2 (blade/blade).

I'm not getting a lot of SDA effect out of my left speaker (plenty from the right) so I started poking around a little bit. It seems to me that the dimensional drivers in the left speaker aren't producing as much sound as the ones in the right. I pulled them out and listened to them and they're running (not just getting sympathetic sound from the cabinet).

I also seem to be getting more bass from the right speaker. I opened the left speaker up and looked for loose connections in the crossover. Sure enough, one of the inductor wires was a little loose. However, I didn't notice any difference in sound when making a good connection with it. I reflowed the solder anyway. I still seem to have the same issues.

However, now I'm wondering if it's just my room. I have a 16' wall that they're on, but the left speaker is at the edge of the wall, which then opens up into another room. So now I'm thinking things may be operating ok, but I just don't have the reinforcement of a full wall.

smglbrth

I would definitely experiment with some type of reinforcement to the side of that left speaker. I've noticed that with my right speaker (open stairwell behind "most" of it) and found one of those old type accordion folding doors to put beside/behind it. Eliminated most of what you are talking about. I put it up when listening and take it down when not. Of course, it's not the same type of structure for density and such but better than nothing. However, don't be surprised if it never sounds quite right in such a setup. Mine still sounds off a little...

mhardy6647

The OP wasn't looking for a generic answer -- but I thought I'd provide one any way

An inductor (or choke) is a coil of wire. The coil geometry (length/number of turns, etc.) determine the inductance of the inductor/choke/coil, and the DC resistance of the inductor is also a factor in its use as a circuit component. An inductor acts as a frequency dependent filter not unlike a capacitor (which, in essence, does the same thing, but with different frequency dependent behavior). An inductor in series with a load acts as a "low pass" filter (allowing lower frequencies to go through while attenuating higher frequencies). Capacitance in parallel to the load can also be used as a low pass filter.

http://www.allaboutcircuits.com/textbook/alternating-current/chpt-8/low-pass-filters/

lightman1

westmassguy

Rex81 wrote: »

However, now I'm wondering if it's just my room. I have a 16' wall that they're on, but the left speaker is at the edge of the wall, which then opens up into another room. So now I'm thinking things may be operating ok, but I just don't have the reinforcement of a full wall.

That sounds like your problem right there. You might be getting reflections off the side wall on the right, and nothing on the left. I have a similar setup, my left speaker is next to a doorway.

mhardy6647

lightman1 wrote: »

I'll take that as a compliment

mhardy6647

more free electronics tips...



Here's the link (I am guessing the hotlink ain't a-gonna work):
http://assets.amuniversal.com/405a58f097b7012f2fe400163e41dd5b

Rex81

Good stuff, guys, thanks. And I appreciate the electrical 101.

I might tear up my basement in order to find a wall long enough to run some experiments. I'll report back any findings.

Rex81

Well, to my wife's dismay, I moved my stereo rig to the longer wall last night and the problem is solved. Full SDA from both channels. Bass output is equal. It's amazing to me how much sound reinforcement the back wall is giving.

Now you're probably wondering why I didn't just set it up on this wall in the first place. The answer is: Because it looks terrible and now there's no place to put our couch.

So naturally, I'll be leaving it as is, and trying to convince my wife to get rid of the couch and replace it with another listening chair. Wish me luck.

littlewoodboats

Better let her pick the chairs.

mhardy6647

littlewoodboats wrote: »

Better let her pick the chairs.

Words of wisdom.

[Deleted User]

and I thought he was the guy that kept all those musical instruments playing together!
"What does the inductor do?"

smglbrth

mhardy6647 wrote: »

littlewoodboats wrote: »

Better let her pick the chairs.

Words of wisdom.

I'll triple these comments, I know from experience...

littlewoodboats

mhardy6647 wrote: »

littlewoodboats wrote: »

Better let her pick the chairs.

Words of wisdom.

I get lucky every once in a while.

I get lucky more often when I let her pick the chairs.

mhardy6647

littlewoodboats wrote: »

mhardy6647 wrote: »

littlewoodboats wrote: »

Better let her pick the chairs.

Words of wisdom.

I get lucky every once in a while.

Even a stopped clock is right twice a day

I get lucky more often when I let her pick the chairs.

Say no more!

https://youtu.be/AGrvQ1c5khU

pitdogg2

nudge nudge wink wink know what I mean