Impedance Query (Help)

[Nitefly]

Hello

Total nooblet here, just trying to understand something that I don't think is very clear at all... ffff

I have a Marantz PM6005 Amp, which has two sets of output terminals:



I'm currently running a set of cheap Wharfdale 220 speakers. I think it sounds pretty good!

But the idea of a sub has always appealed to me, so I've bought one: a BK XLSS400 (forward firing). Very exciting.

Now, the connection terminals on the Marantz are absolutely ****ing horrible if you are using bare wire. You sort of have to twist them shut and they don't stay tight very well. So the Wharfdales are currently connected via Banana Plugs on the A terminals. So far so good.

The BK electronics sub is a bit like a REL, it's supposed to connect to your high output speaker terminals. The obvious approach, as per RELs, would be to connect the bare wire from the sub to the very same connection terminals on the amp that are going to the 220s. But ugh, since I'm already using banana plugs I'd have to connect the sub using bare wire. This is worse than death.

Ah, I have an idea. Wouldn't it be lovely if I could just connect the sub via banana plugs to the B terminals... avoiding the bare wire nuisance? So I'd end up with the 220 speakers connected to A terminals, sub to B terminals - both via banana plugs. Let's have a look.

Marantz manual says this:



220s manual says this:



BK XLSS400 website says this (not dealt with in the manual):



Huh. Well that all seems fine then! I look forward to using both sets of terminals.

But wait, what's this from Marantz....

However for most amplifiers, if the device has an A / B switch for the front speakers and you use the Connection speaker pair A + B and want to run both pairs together, both speakers must have a minimum impedance of 8 ohms or higher.

i.e. if you wish to run both pairs together then

• speaker A must be no less than 8ohms
• speaker B must be no less than 8ohms

If you use speaker pair A or B, you can also use 4 ohm speakers - but not both together - or this can potentially cause damage to the amp.

Wut?! So I can't do it then? Why is it so goddamn vague in the Marantz manual (╯°□°)╯︵ ┻━┻

Am I stuck with having to use the god awful bare wire connections (to tie the sub to the same terminals as the speakers)? Help

Many thanks in advance!

 

[Nitefly]

The current draw from the high level is negligable. It's fine using speaker B for the subwoofer

The sub has it's own amplifier. The 4 ohm impedence is the internal characterstics of the driver, that isn't what is seen by your amp.
It'll literally use 500mw of power from your marantz for the signal to the sub in high level

Thanks champ. This makes complete sense... but I'm still a bit nervous. Does the BK Sub not give an impedance level because it's self-amplified? I suppose this is why the suggestion for Rels and BKs is to connect to the very same speaker terminals...

I think I could deal with blowing up the old amp... but not damaging the sub as that's more expensive.

 

[Nitefly]

Thanks such much @lucid - that was very generous of you to explain that so patiently! Also thanks to @Ormy1 for the bonus digging, I'm very grateful.

Sadly the current banana plugs are QED Airlocs that have been crimped shut... so attaching wires to those is out of the question. No bother, I'll just buy a set of screw locks for the sub connections and plug into the B terminals (like these).

Looks like I'm good to go then. My final musing... I have seen someone else attempting to use the B terminals as I've mentioned but he didn't get any luck. Obviously, we'll never know what caused it to fail for him, but I have a sneaking suspicion that he forgot to turn on the B terminals - there is a button to select A, B or both on the front of the amp

I'll report back with hopefully a working sub

Thanks again!