Running a subwoofer

[harlond57]

I've searched here and at the Brennan website and couldn't see the answer to my question. Which is, would it work if I ran an RCA cable from the Brennan to a powered subwoofer?  This is for my brother, who just got a B2 and is running Klipsch speakers, so he doesn't need an external amp, but might still like a subwoofer.

[PMB]

Hi Harland 57,

We would need to know more about the setup to advise, i.e. are the Klipsch speakers self powered. How are they connected to the B2, etc? Will the sub be self powered, etc?

Paul

Brennan Support.

[Davywhizz]

As Paul says, the question raises others, but let's assume the Klipsch speakers are passive (the few active ones I've seen have their own subwoofer output) so your brother is not currently using the B2 line out/spdif socket?

Hopefully someone who's actually done it will reply, but I can offer a few thoughts which may help the discussion.

Some hifi amplifiers use combined, full frequency line out/sub out connectors rather than a dedicated subwoofer out. So in theory the B2 line out socket could be used, provided the sub has a crossover control to filter out the higher frequencies.  However, the B2 line out is variable not fixed. The output depends on the B2 volume setting.  This is why Brennan recommends setting the B2 volume high, at maximum or close to it, when using an external amplifier,  then using that to set the audible levels.  So there's a question about whether your brother's B2 will provide enough signal for a subwoofer to work with efficiently. It may be OK if he's always using it at not too far from maximum volume. 

As an alternative to using the variable B2 line out, the Brennan website describes (under "audio connections") the use of a tiny and very inexpensive external DAC which creates a fixed line out analogue signal.  You could run it optically from the B2 and take an RCA feed from that to a subwoofer. 

If you want to experiment with using the B2 line out direct, you'd need an adaptor to convert the B2's 3.5mm line output to RCA. You can't just plug in a RCA cable. Whilst you can use a RCA cable for a sub, there are cables branded for subwoofer use which use RCA plugs but tend to be thicker and with more shielding.

However you connect, you'd need to use the "Jack Sense" option in the B2 menu, so the speaker outputs remain active when something is plugged into the line out. Normally they cut out, as you'd probably expect if using headphones or an external amp.

One minor problem with all this is that even if you add a sub, the B2 will still deliver a full frequency signal to the main speakers. Ideally, it would be better to have the option to stop some of the lowest frequencies going to the main speakers. It's one of those nice to haves, maybe not essential. It gives your main speakers more room to work in and can help with speaker placement, by cutting out some bass reflections if your room requires placing the speakers closer to a wall or corner than you might like.

You asked about a powered sub, but the other option would be to use a passive sub which can take speaker level signals from the B2 then send on the higher frequencies to the main speakers. That gets round any problems with using the B2 line out. Others here will know more than I do, but my instinct says it may be asking too much of the B2 to drive both a sub and the main speakers. And, clearly, you need to know exactly what you are doing if playing around with speaker level signals.

[Daniel Taylor]

That's some excellent advice from Davywhizz.  But after trying to absorb all that, I've come to the conclusion that most anything you try will end up being a compromise and not provide the best sound.  If you want to use the B2 in a high fidelity system, you need an external DAC and external amp.  Those two can be easily combined in an AVR or integrated amp.  That can also provide a better option for connecting a subwoofer.

[harlond57]

The Klipsch RPM-600 speakers are passive speakers connected to the B2's banana plug inserts.  The subwoofer my brother is looking at is, I believe, the Klipsch R100-SW, which is self-powered and has a low pass filter.  The line out/SDIF is not currently in use.  Thanks everyone for your input.

[Davywhizz]

Those speakers would definitely benefit from a meatier amp/DAC. 

D