BFD & Paradigm X-30 (1 Viewer)

[PaulT]

Finally going to take the plunge and purchase a BFD to EQ my Servo-15.

Am currently running the Paradigm X-30 pre-amp/crossover between the Receiver LFE Out and Input on the Servo.

I believe since the X-30 is controlling the crossover frequency, gain and phase of the sub (basically it is a remote box with the sub controls on it) that I should place it 'after' the BFD

ie. Receiver > BFD > X-30 > Sub.

Does this make the most sense?

 

[ThomasW]

Since you have LFE outs on the receiver, you don't need a X-30 at all. Having unnecesary equipment in the signal path is not only a waste of money, it degrades the quality of the signal.

 

[Allen Ross]

the only benefit i see is the phase adjustment

 

[PaulT]

ThomasW - While I appreciate your opinion, the Servo-15 has no phase or crossover adjustments on it, so I chose to use the X-30.

Being able to adjust the Sub from my equipment rack without crawling over a couch and getting in behind a TV should more than make up for 'degradation' of the signal should there be any.

It came free with the Sub there has been no waste of money.

 

[ThomasW]

Cascading crossovers really isn't a good idea the bass will likely be muddy.

If you can turn off the LFE channel and run main pre-outs to the X-30 using it as the primary crossver, then you have a good signal quality

 

[Rob Formica]

Paul, I don't think it'll make much of a *technical* difference whether you place it before or after the the BFD. Practically speaking, having the X30 after the BFD may better if you need to add gain to the sub as it'll prevent from overloading the BFD's input. The X30 and BFD are both a form of processor, the their filtering is additive.

I understand Thomas's point as well... as he is trying to say that the X30 is duplicating two functions (cross-over and level adjustment) which are probably already part of your preamp/processor. The X30's only additional feature is the variable phase adjustment Allen mentioned.

Good luck…
Rob

 

[Chris Popovich]

Since changing your crossover point will change the frequency response of your sub, I put my x-30 (with the crossover point I use to match with my main speakers) before the BFD.

Make sure you won't ever get the BFD into clipping if you turn your volume on the X-30 up.

On second thought, I'm not sure it'll make that big of a difference. Try both ways and tell us if one of them sounds better.


Chris

 

[David Gadd]

I absolutely disagree that it is always (or even typically) better to use the crossover in the pre/pro. alone.

People always seem to assume that all preamps/processors do a competent job at crossing over between sub and mains. Mine certainly doesn't (e.g., 100 hz 12 db/octave low and high pass!?? and no high pass at all on any analog input). In my case, using the processor alone is a massive compromise (unless you like too high & too shallow roll off for the sub plus double bassing mains depending on which input you choose; I don't).

Also, stereo subs and/or mains that are competent down lower (e.g. 50hz) are often partially or totally compromised by typical Dolby spec. processors with their typical 80hz 4th order low and 2nd order high passes. My speakers are transmission lines with a rolloff that starts substantially below 80hz. So, even if I did have a "good," "normal," Dolby spec. pre/pro., I'd STILL have double base issues from my mains since there is no way to force my mains to roll off at 12 dB/octave under 80hz which is ASSUMED to be the case under the Dolby standard.

To summarize: I absolutely disagree that it is always better to use the crossover in the pre/pro. In fact, unless you have main speakers that roll off at 12 dB/octave under 80hz, you WILL HAVE midbass bloat and/or cancellation issues that can make your sub/main integration difficult at best. Again, Dolby assumes mains that most people DON'T own.

PaulT: I use a BFD but I have no idea which order will work better for you with the X-30; sorry.

 

[ThomasW]

Where was that posted in this thread?

The reality is that no one suggested or inferred that the pre/pro LFE output was the 'best' choice.

The concept here is actually quite simple, use the XO in the pre/pro or use the X-30, but don't use both...

 

[PaulT]

I'd love to be able to do that, but unfortunately my receiver will not allow it (and still have some kind of Bass Management with all speakers set to small). sigh, maybe one day an AVM20.

Figuring if I max out the XO on the X-30 to 150Hz, and assume the Onkyo 696 uses 80Hz, then there should not be too much filter overlap from the receivers XO.

I was more worried about clipping the BFD as per Rob and Chris' posts if I put the X-30 ahead of the BFD.

What I will do is try it both ways (and with and without the X-30 as well) and see how the graphs look.

 

[ThomasW]

Does it have pre amp outputs for the main L>R speakers? If it does then put the sub setting to 'no' or 'off'. And set the speakers to 'large', that will turn off all bass mgt and send the bass info to the main pre-amp outputs. Send the pre-amp output signal to the X-30, loop the high pass back into the receiver. Send the low pass to the Behringer.

 

[PaulT]

therein lies the rub. Pre-outs, yes , Main-ins, no .

I actually got the X-30 with the high/low pass options (rather than the X-20 which does speaker level outputs) for the future when I do pre-pro/amp(s), so for the time being I may just leave the X-30 in the box and stop tweaking stuff once my levels are set.

 

[ThomasW]

Bummer............

This is the perfect excuse to buy a new power amp........

 

[PaulT]

have my eye on a new Rotel or used Bryston...my wife just came in and asked why I was laughing, and when I told her, she got this weird look and started to twitch...

 

[PaulT]

As a follow up to this after the BFD arrived:

Tried the setup with and without the X-30, and as per ThomasW's posts, I found that the overlap of the cutoffs in both the X30 and my Receiver had a detrimental effect (double rolloff above 80Hz) which I could actually hear.

What I wound up doing is removing the X30 (until I get an external amp) and running with the fixed crossover of the Receiver.

Here is run 2 through the test tones. I started with the PEQ spreadsheet with 1/12th Octave tones to get a better idea of the filtering, then did the final measurements with the subtestmodel spreadsheet and 1/6th Octave tones. Much thanks to the work of Tony Gomez and Sonnie Parker. Still needs a bit of work, but the 'House Curve' is starting to look (and sound) pretty good:

 

[ThomasW]

Looking pretty good. A wee bit of cut at 34Hz, leave the peak at 22Hz alone. That should give a nice overall house curve.

BTW go for the used Bryston .........