Subwoofer with Amp1B

[arjen]

Hi,

I just finished the woodwork for a small sub. It will be driven by a AMP-1B. The sub holds two speakers, each with two 8 ohm voice-coils. So I have a number of options.
Option 1: Parallel the coils and let each (now 4 ohm) speaker be driven by one channel of the AMP1.
Option two: parallel the coils, put the two speakers in series and let the (now 8 ohm) speaker be driven by a bridged AMP1.

Each option has its pro's and cons. The amp will not be inside the box to avoid long signal wires. So in case of option 1 I will need 4 terminals and two sets of speaker wire. But in case of option two I need to bridge the amp and I don't know if that is at all advisable. Also I do not know if there is any difference in performance and efficiency when comparing two separate channels vs one bridged.
But I have to make a decision before closing the box...

Any thoughts?

Arjen

[FFF]

Keep it simple = KIS:
- use option 1, so you don't have to mix anything (performance 1vs2 is/should-be the same)
- put the amp IN (or next to) the box please to avoid long speaker cables (long (-er) signal cable usually not a problem, LS-cables are)

[arjen]

I agree with KIS. And when I put terminals in the box for both speakers I can always do the 'bridge thing' later on.
But I don't agree with your second statement. I can assure you that in my house longer signal cables are a problem. They pick up all kinds of rubbish, from 50 Hz hum to higher frequency data garbage that I don't want to listen to... I suspect bad mains cables and TV/data cables running right under my house to the rest of the neighborhood. So I use very short very well shielded interlinks. The only way to bridge a longer distance is to use balanced in/out but that would be the end of KIS...
BTW, long is a relative term. I don't think the speaker cables need to be longer than 2 meters.

Thanks, I'll close the boxes tomorrow.

Arjen

[FFF]

In that case, I would check Earthing and maybe use shielded cable with a twisted pair.
Have you ever tried (cheap too) computer STP (shielded version of UTP) ??
Just connect one core to shield too OR Pgnd to shield (careful)

Long 50m+ Eguitar cables seem to be a twisted pair too, not even shielded. (UTP is real cheap)

[arjen]

Been there, done that. In fact that's what I mean by well shielded interlinks (I also tried UTP braided speaker cables but that did not do a lot for me).
But I think the loss of two meter 4m2 speakercable is nothing compared to 2 meter interlinks. I don't want to risk picking up any hum before the amp. Especially since this is a subwoofer...

Thanks

Arjen

[Scratchy]

Have you ever tried (cheap too) computer STP (shielded version of UTP) ??
Just connect one core to shield too OR Pgnd to shield (careful)
(UTP is real cheap)

That's what I'm using to run from my computer room to my AMP1B & 6 in the living room.
I ran it inside the wall up into the attic and back down again.
Probably 50ft long with no hum or signal issues...

You might have a grounding or wiring issue in your house.
Here is a good troubleshooting doc for this:
http://support.fluke.com/find-sales/...03_ENG_C_W.PDF

[arjen]

Tanks for the link, but... Don't get me started about the wiring in my house :-(. The 'technician' who installed it probably never heard the terms 'ground' or 'neutral' in his life and thinks 'hot' only refers to babes. In my living room none of the outlets are grounded. (So at least I don't have a grounding issue there :-).) Only some of the outlets in the kitchen are. Still it all complies to Dutch regulations so there is not a lot I can do about it (it's a rental, so I cannot replace the wires). I put in an extra group in the switchboard to feed my office (a former bedroom without grounded outlets) so my computers are fed with reasonable clean (grounded) power but that's about as far as I'm willing to go in this house. The owner is not very pleased with me altering the wiring.
I'll stick with keeping the amp close to the rest of the system. Besides, if I put the amp in or near the speaker a mains wire will have to run parallel to the signal cable. That's asking for trouble, even if it is only two meters...

[Saturnus]

If it's a huge problem you could always go pseudo-balanced with a line-trafo at each end, that'd solve the problem.

[FFF]

Guys, we/he can try whatever. It will not help. His system is bad.
- needs a good elecrician
- needs his supplier to send an inspector to check system, especially his Earth-pin
He seems NL; I've PM'ed him.

[arjen]

I'm Dutch indeed and have just replied to FFF's PM.
However, my question was not about my electrical system but about bridging or not. I've decided to go for option 1, I can always try bridging later.