Help wiring a sub-woofer into my system please. Best option, if I can?

[Akagi]

Help wiring a sub-woofer into my system please. Best option, if I can?

Hi guys, so I currently have a pair of Wharfedale Diamond 9.2's which I want to add a Wharfedale Diamond SW150 to for a little more bass punch.

I have two amps to choose from, a Marantz PM5003 and an Arcam A75, I don't mind which one I use.

The outputs on the back of the amps look like this:

A75:

Spoiler

PM5003

Spoiler

And the inputs on the sub:

Spoiler

TIA

With the Arcam could I use the pre-out to go to the line level input on the sub, then wire the speakers to the sub? And potentially the same with the Marantz with the recorder outs?

 

[lucid]

Using the pre-outs from the ARCAM is a simpler route.

For the Marantz, you would wire the sub in parallel with the main speakers. That means your existing speaker wires stay as they are. You add a new pair of speaker cables, and they go from the speaker terminals to the sub's high level input.

None of these options sees you wiring the speakers to the sub in preference to either of the amps. The sub doesn't contain an amplifier capable of powering your main speakers; that's the job of the Hi-Fi amp. Nor does the sub include the sort of frequency filtering that slices off part of the bottom end going to the main speakers.

 

[Akagi]

I was with you, then you lost me.

So I'd plug the sub into the pre out, and leave the speakers wired into the amp?

How would I control frequency crossover?

I thought I'd have to plug the speakers into the sub to be able to control that.

 

[lucid]

So I'd plug the sub into the pre out, and leave the speakers wired into the amp?

Yes, this, exactly.

How would I control frequency crossover?

The main speakers have their own natural roll off. That means if you played a 20,000Hz to 20Hz sweep tone which started high and dropped in frequency, then the 9.2s would produce sound down to a point where the volume would fall away rapidly. This would be at some frequency well above the floor limit of 20Hz. Lets say 50Hz is the point. The test tone and amp would still be making sound at lower frequencies, but the speakers would be unable to reproduce them. You would have just experienced listening past the roll off point.

Okay, so the 9.2s have a natural tailing-off of the frequencies below a certain point. Your job then with the sub is to blend the subs output (volume and frequency) so that it marries up with the 9.2s roll off. You blend the frequency with the crossover control, and then use the volume control on the sub so that the additional bass that the sub is producing sounds the balanced with the higher frequencies that the 9.2s are producing.

This is the same procedure whther you connect via the ARCAM pre-outs, or if you use the speaker wires to make a high-level connection.

 

[Akagi]

Awesome thank you. so, another daft question, if I use the marantz could I use the poles for the second set of speakers (there's an option to turn each set on and off individually) and effectively have an on off switch for the sub?

 

[lucid]

Yes, you could. It's actually a quite smart bit of thinking. You could have the 9.2s on SPKR A and the sub on SPKR B which, as you suggest, gives you a sort of On/Off switch for the sub.

Incidentally, the speaker sockets on the sub draw virtually no power from the amp. The impedance of the sub is way way higher than the speakers. It'll be somewhere between 40,000 and 100,000 Ohms. This means that the sub is drawing almost no current compared to the 2-3 amps that your 6-8 Ohm speakers might draw at full volume. I'm telling you this because some worry about the loading on the amp by wiring in parallel; but with a very high Ohms load, the amp doesn't see the sub as a load to be driven.

 

[Akagi]

Awesome, I'll grab some more speaker wire and give it a stab with wiring them paralell. Thanks for all your help. It seems a simple thing now, but having not done it before, I just couldn't wrap my head around how to do it!

 

[Akagi]

Actually forget that, I'm going to use the A75. I've been using the PM5003 and the A75 has just been sitting there (I bought them both at the same time, and honestly only use the Marantz because it looks nicer on the shelf...) but having just looked into it a bit more, the Marantz was released at £220 in 2008 and got generally mediocre reviews, whereas the Arcam was released at £1000 in 2001 and got generally very good reviews. It also has a higher power output.

Since audio tech in amps and speakers tends to progress very slowly, I'm going to go out on a limb and say the Arcam is still a hugely more capable amp and I'm a muppet for leaving it sitting there...