Sub outputs in BP20/25

zeidoun · « **on:** 28 Feb 2004, 08:00 pm »

Hi Everyone,
Could you please explain to me how to connect my sub to Bryston BP20/25 preamp if I want to use a sub in addition to my 2 main speakers? Currently, I am using a HK 3475 and I am connecting my sub to the "sub output" of the receiver and I do not see any sub output on the BP20/25 preamps?
Thank you very much.

Mains: Paradigm Ref 60
Sub: Paradigm servo 15.

jethro · « **Reply #1 on:** 29 Feb 2004, 12:05 am »

In order to use your sub, you will have to see whether it has speaker level inputs (look for binding posts). If it does then you will run the speaker cables from your amp for left and right channels to the speaker level inputs on your sub, and then run speaker cables from the sub's speaker level outputs to your speakers. Your sub lowpasses the speaker level inputs, directs that signal to your sub's speaker, and then sends the remaining signal to your left and right speakers. This is how it usually works. Double check your sub manual and be careful. I blew my active sub's electronics when I tried to use a Bryston amp to drive my sub instead of the builtin sub's amp. I didn't connect things incorrectly, but I managed to send a pop to the sub which may or may not have blown it.

The other alternative to using speaker level inputs to your sub, is to buy a line-level crossover such as a Bryston 10B sub. This will allow you to use the line level input on your sub but is an expensive solution.

jethro · « **Reply #2 on:** 29 Feb 2004, 12:13 am »

I took a look at the Paradigm site and it looks like the servo-15 doesn't have speaker-level inputs (check anyways). Paradigm sells the X-30 which is a crossover that might suit your needs if you don't have speaker-level inputs on your sub.

zeke · « **Reply #3 on:** 29 Feb 2004, 01:56 am »

Assuming it is a powered sub, you use your second set of pre outs from the bryston to the sub ...........

jethro · « **Reply #4 on:** 29 Feb 2004, 02:15 am »

Quote from: zeke

Assuming it is a powered sub, you use your second set of pre outs from the bryston to the sub ...........

This will send the entire signal to the left and rights as well which may or may not be a problem.

zeidoun · « **Reply #5 on:** 29 Feb 2004, 06:19 am »

Thank you very much for your help. I will use the X30 to connect the sub to my pre-amp.
Zied

nicolasb · « **Reply #6 on:** 1 Mar 2004, 01:28 pm »

Mr Zeidoun seems to have solved his problem, but as there's some slightly confusing advice on this thread, I thought I'd try and pull it together a bit....

To drive a subwoofer, you have to have some kind of device which can act as a "cross-over" - i.e. that can separate a single set of input signals into two separate sets of outputs, one containing the low frequencies (which are sent to the subwoofer) and the other containing the higher frequencies (sent to the main speakers).

This can be done either at line-level (with the device in between the pre-amp and the power amp) or at speaker-level (device in between the power amp and the speakers).

Other things being equal, it's usually better to use a line-level device if you have an active subwoofer (although there are exceptions). "Active" in this context means a subwoofer with its own amplifier built in.

Some subwoofers have their own cross-over circuitry in the box, others don't. As Mr Zeidoun has already figured out, the Paradigm Servo 15 hasn't. If you are using something like a home cinema processor (or AV amp) then it is capable of acting as a line-level cross-over device. If you aren't, and you want to use a sub like the Servo 15, then you need a separate cross-over. The X.30 is Paradigm's own line-level cross-over.