Subwoofer setup question

[slingshot]

I'm having a slight problem setting up my sub which as IPL sub kit (hopefully I built it properly).

I'm trying to use both low and high level input's the low level for cinema and the high for normal stereo. The high level is on a spare set of switched speaker outputs on my power amp (which just drives the main woofers).

The problem is that the phase seems different between the 2. When using it with the high level input the phase needs to be reversed, otherwise it sounds like I'm getting less bass when I turn the frequency range up (I'm guessing that with the wrong phase setting it's cancelling out some of the main speaker bass at the crossover point). Has anyone come across this before and is there a reason or a solution for it ?

Slingshot

Hi Slingshot,
That sounds fair. I've just built myself the SW2 and I'm over the moon with it.
From what you've said; turn the crossover to the lowest frequency, turn down the low and the high level volume to minimum and begin by having the high level vol. at say 1/3. Bring up the crossover to just below your mains or to a point that doesn't cause room boom. Experiment with the phase; as in some circumstances you may need to cancel a peak if your room response is bad.
Once set, try your Low-level volume. If this doesn't cut the mustard then the chances are your High-level amp feed is reversed. Reverse the Red and Yellow AND the phase switch and try again!
Using X-Men THX Reference for the Bass sweep, mine goes right down to the bottom. Very satisfying!
One or two minor dips and peaks from the room, but that comes later.
Rob.

[dUnKle]

You mention the X-MEN frequancy thing, can you describe this in more detail.

I have a REL Q100E and feel that it could sound so much better.

Could you give me more tips on using BOTH connections

Duncan,
The X-Men Movie DVD has an Audio and Video set-up in its Special features. Good for setting-up Home Cinema Equipment. Just follow the on-screen instructions!
It helps if you have an SPL Meter, but not absolutely necessary.
Rob.

Duncan,
If you have a REL have a look at their Manual: http://rel.net/m_qrange.shtml#_Toc474204698
Rob.

[dUnKle]

I have the test tone you mentioned on many discs and have used the subwoofer test numerous times but have yet to really find out what it is for.

When I play it there is never a moment when there is no noise ( well up until it finishes ) but as it get lower it does go in what I describe only as high/low waves.

I have my roll-off set to max as this makes sure that the AMP does all the bass work and that the volume is at 75DB is there anything else I should do

Duncan,
Not sure what you’re saying about the amp doing all the work! Are you only using Low-level? If so, just use the High-level and try the roll-off lower until there is a hole in the response. Then bring it back up until the hole in the response is just filled.
Rob.

[philmate]

Hi guys,
I too have just put together IPL sub and am extremely pleased with it. But, after reading the above am I right in thinking that the phase has to be correct for both high/low level and to do so the red/yellow wires have to go to correct r/l speaker outputs or can they go to either, I'm a bit confused with your advice./
Philmate

Sorry Philmate,
Perhaps I'm clouding the issue here.
When I replied to Slingshot, I was referring to a definite situation of incorrect amplifier phase output between speaker output and subwoofer (low-level) output.
In practice this should NEVER happen, but I have had this happen to myself in the past.
If the amp is wired incorrectly you will find that Bass will virtually disappear when the LFE channel kicks-in on DD5.1 or DTS. I don't expect this to happen!
I hope I made this clear to Slingshot?

Rob.

When I refer to amp I mean AV amp, not subwoofer amp.
Just thought I'd clear that one up.
Phew! The deeper you go the deeper you get. (No pun intended.)

[slingshot]

Thanks for the help I love the sub it's excellent, well up there with the Strata III I listened to.

I tried your advice, however I still have the problem where the HC low-level processor output seems out phase with the high-level output from the stereo amp. It's not a massive problem because I can always switch the phase when I swop from cinema to stereo, however it would be nice not to have to bother walking all the way over to the sub.

I tried swapping the red and yellow on the high level but this seem to have no effect, so I wondered wether I could rewire the low-level lead and swap one end round so that red and black are swapped, would this swap the phase around for the low-level input ?

Cheers

Slingshot

If you've already tried reversing the phase on the high-level and it didn’t work there’s no need to do anything else, just restore them to original, the phase isn’t the problem. Sounds like the set-up. Have a word with Ivan; I'm sure he can sort you out.
Just a thought, are your Main speakers in phase?
Rob.

[dUnKle]

I have my sub connected only by the phono connection. I have set the roll off to max as I was under the impression that my amp ( a denon a1d ) will do all the work of deciding what frequancies should be sent to the sub and so the roll off has to be on max else bass sounds will be lost.

I was under the impression that the roll off controlled how much bass the sub produced and if set too high with speaker connections the bass can be overblown, but with the phono I thought that the amp made sure that there was never too much bass

Duncan, there are many different viewpoints on this subject, this is just mine:

There’s nothing wrong in just using the low level -if you’re satisfied- with the crossover in the AV amp cutting out the bottom end of your main speakers performance. The general consensus for Hi-Fidelity is to allow the main speakers to naturally roll-off and use the subs low-pass (crossover) filter control to bring the bass frequencies up to meet them. This way you are not affecting the main speakers design performance. If you require the Low Frequency Effects channel for HC use, adjust the volume for the low-level separately. Some subs have a by-pass for the LFE input, some don’t, but don’t worry too much if yours doesn’t as the LFE track information on Dolby 5.1 cuts off dead at 120Hz, so a smooth roll-off of LFE from around 80Hz can give a nice blend into the main cannels.

Rob.

[dUnKle]

Ok, I think im staring to understand.

The problem with the REL Q100E is that the roll off is only marked MIN or MAX

I need the info in as simple as terms as possible so am I correct in thinking I should......

Connect the sub by the SPEAKER CONNECTIONS only to start with. Set the subs volume to the same as the front speakers ( 75db in my case ) and then play the sub test. Now I should increase the Roll Off until there are no gaps in this test. I should then leave the Roll Off in this position ( if it helps I have B&W 603s2 speakers ) I also assume that I should now set my front speakers to LARGE.

Now I should connect the sub back up with the phono cable as well and set the volume for this back to 75db as well.

Is this correct ????