I think I have a problem.

[Conrad.]

WIth further research it seems that there is a standard for the LFE channel and it's up to 120Hz.

I've also been having a look into my receivers settings and options and it seems that it is processing the signal from the multi channel inputs before passing them through to the pre-outs. It's certainly applying volume controls to each channel and it could be applying EQ as well (although that might be to the overall signal). If it's converting the analogue signal back to digital and then back to analogue again then I'm wasting my time converting it with a decent sound card.

Basically, I need to understand exactly what processing is going on with my signals before I can begin to EQ them. I really appreciate the help and advice I've received so far and, if it's ok, I'll take that away, work out exactly what's happening and then come back with a fresh set of graphs and a knowledge of what I can and can't control.

Two good things have come out of this already so far though: it seems that I have more control over my crossover than I though previously and I have a hugely extended bass response from moving my subs about.

Thanks again guys!

[brucek]

Any crossover that I would apply would come either from the receiver (if it's applying any crossover at all; something I still need to find out) or from within the software passing the digital streams to the soundcard.

I just can't see that there would be any other reasonable way to bass manage your speakers than have the receiver do it. Just because you're using an HTPC as a source should be irrelevant.

I think you're right though, I need to go from the soundcard to the sub directly.

I have to disagree. Feed the receiver and engage the standard 80hz crossover.

How would I EQ that? Would setting my maximum sweep frequency to be the same as the upper limit of an LFE channel work? Is there even a standard frequency range for LFE channels? I sense a trip to google coming up.

The LFE channel "spec" allows for frequencies up to 120H. But, even though the LFE does indeed extend out to 120Hz in the Dolby spec, my understanding is that the sound engineers roll that off themselves to integrate it more smoothly into the standard 80Hz LPF (low pass filter) crossover provided by all home processors.

The actual spec'd information when given to the sound engineer goes all the way to 120Hz and then is digitally cut off. This would be horrible to listen to if sent to a sub, so I guess it's their creativity to roll it off (and a smart move).

Since the 'small setting' redirected bass is normally rolled off from 80Hz (when that's the crossover you choose) at 24dB per octave, I suspect that the LFE channel is given similar roll off characteristics.

At 24dB per octave, the amount of signal left at 120Hz is quite weak. Myself, I wouldn't be concerned about any differences in setup because of the LFE channel.

brucek

[Conrad.]

Hello again,

I'm back and I think know what I'm talking about.

Bruce, you're right, there's not another way to manage my bass other than the use the settings on the receiver.

I was mistaken before. I believed that "multi channle in" and "pre-out" were some kind of pass-through and that the signal was remaining untouched; clearly this isn't the case. All it's doing it allowing you to decode a signal into it's constituent parts and then have the reciever do what it needs to do in terms of equalization, distance delay application, volume etc and then send it out to the power amp.

With this in mind I've re-set-up the reciever using it's auto EQ feature. This gave me a pretty good starting point. I then rebalanced the speakers using the SPL meter and the recievers test tones. Then I went on to re-EQ the subs. Doing one first, then the other I was able to get REW to recomend a couple of filters that got a pretty decent tracking of the target house curve. I've applied those filters using my BFD and the full frequencey response is attached.

It still has it's peaks and troughs but they're much more managed now.

What do you guys reckon?

We watched Cars on blu-ray last night (not the best test of a sub but decent sound none-the-less) and it sounded great. I've got U571, WOWT and Master and Commander all waiting for some time alone!

[Conrad.]

Incidentally, Bruce, you'll be pleased to seee gone back to a standard house curve. That's not to say I won't switch back but, unless I've actually run some caomparisons I'm in no position to compare them. In a couple of weeks, once I've gotten used to things and they've settled down, I'll adjust the curve and see if I notice any difference.

Thanks again for your advice and patience guys,

[brucek]

What do you guys reckon?

Yeah, that looks pretty good. Quite a few members have reported good results with the Auto EQ first and then BFD EQ second.

Incidentally, Bruce, you'll be pleased to seee gone back to a standard house curve. That's not to say I won't switch back

hehehe, yeah that's fine. I didn't actually mean to derail your thread with my rantings. I had a point to make and I gave my support arguments, and that's the end of it. You'll have to decide what works best for you.

brucek

[Conrad.]

That's great news, it's always nice to hear that someone else likes the look of your graphs!

It's put off my need to buy a new sub by at least 6 months. The prices of a velodyne DD18 helped too; £3,000!

Anyway, I have a further question for you. Currently my BFD is sitting between the HTPC and the multi-channel-in of my receiver, on the sub channel. This means that only the HTPC is being equalized. My cable box also goes into the receiver and is decoded to Dolby Pro-Logic II and then sent out to the power amp. I've got it set up this way for cabling reasons; it's a long and dull story but I can't connect the BFD output to the sub directly, yet.

My question is if I move the BFD from one side of the receiver (from before the signal goes in to after it comes out) do I need to re-sweep and re-equalize? The processing sequence is irrelevant, right? It's all about the position of the sub and the settings. Whether the BFD gets the pure signal or the signal that's been processed should make no difference, should it?

[brucek]

do I need to re-sweep and re-equalize?

The only difference I suppose is that the level from the HTPC would be a fixed line level and the output from the receiver would be at the mercy of the volume control. But that's no big deal other than being sure the trim from the receiver was set so that you never clipped the BFD.

brucek