General SUBwoofer Advice Thread

Good. First-order filters don't have frequency-dependent phase shift.

 

Thank you!

Thank you too!

 

Anyone have experience with raising subs? Seems to work very well here, i was aware of the concept but never tried it until recently. By chance really… i have some big and tall speaker stands and i thought i’d use one to put one of the subs at ear height in the listening position. Then do a subcrawl and measurements to find a better spot for the sub to fill in a 60hz dip. Did not find any suitable spot on the floor but when i stood up i could suddenly hear the test tone.

So walking around the room i found a spot that sounds good at the seat. Not great for a dip at 40hz ish but for that there is a good spot on the floor. So now one of the subs is at ear height behind me on the right and the other is in front next to the left speaker.

Chopped of some peaks with Dirac which i only let correct up to the midbass and i’ve never had it this good.

Not practical with all subs but these are two 10” subs that are not too big and the stands are quite solid.

 

When I lived in a condo I used a sub raised using a simple ikea lacks and auralex subdude mat. It was used in near field at the seating position of my home theater. It did seem to increase the SPL for my rather poor open concept room. I’m not sure about the room response as I just let audyssey xt32 just do it’s thing but I guess the higher spl meant improved response. Those lacks are very sturdy and happily held my 100lb sub for years.

 

Raising them could solve some null issues as you now have another dimension to play with. Specifically if you cant control phase exactly you could use height to compensate (somewhat ) for distance, i.e., you no longer have to place the sub 6 ft into the room for it to sound best in your listening position.

The issue now becomes vibration: All that internal bracing they built into the sub box (and probably even more) needs to be duplicated in the stand or the bass can get real messy. You cant try and 'lock' the heavily braced box to the floor with spikes anymore, you need to build something very stiff and very heavy that doesn't sway. That's why bigger studio monitors are usually bolted into the walls.

Given all that I'd play with the phase all you can before putting a box sub on a stand of any kind.

 

Or just stack multiple subs on top of each other, like the line arrays REL is pushing nowadays.

 

Well with these suspended wooden floors spikes are a big no. It’s all mass and sorbothane for this setup. Even the lower sub i have to keep 26cm from the floor or it becomes a giant speaker. It’s basically a trampoline where shit starts wobbling if i jump.
As for phase it never really was an issue everything is time aligned and in phase, just that dip was doing my head in…

This room is just annoying to deal with being asymmetrical opening up in the back to another area as well.

But i hear you on the stand, it is quite solid and filled with sand but it could always be better. Thinking of placing something heavy on the foot. It’s a custom piece made out of steel welded together.

 

I'm having an issue hooking up my Rhythmic L-12 to my Mackie powered monitors.

I have a Khozmo passive preamp that has 2 pairs of XLR outputs that output simultaneously for biamping. I'm using one of them for the sub, running long XLR cables to a cheap Roland XLR -> SE converter, than short SE cables to the L-12.

When I plug the L-12 in, both my speakers buzz pretty loud.

the strange thing is that I have dedicated lines on all the outlets in my room which was done a couple years ago because I have so many electronics in here. The left speaker is hooked up to the same outlet as the L-12, but the right speaker is hooked up to a separate socket that is a different dedicated line. So I don't understand how the buzz is getting from the L-12 to the right speaker.

I also have tried unplugging everything from the outlet I have the L-12 in and just plugging in the L-12 into a Zero Surge along with the monitors, and the buzz still happens.

And I have also tried swapping out the cheap Roland converter with a Jensen, and the buzz is still there.

the only thing I can think of is that there is a problem with the Khozmo passive preamp.

Any suggestions as to what could be going on? I've had this sub for months and I'd love to get it hooked up.

Thanks for any advice!

 

Any time you have multiple things connected electrically (I.e via interconnect cables) but plugged into separate outlets, you have a potential for a ground loop, dedicated line or not. And the fact that you have one speaker on a separate line probably makes that even worse (it would have a different ground reference than the other things it’s connected to). Likely the conversion from balanced to single ended is not helping either.

Are you able to plug everything into one wall outlet (I.e a power bar on that one outlet or set of outlets)?

 

Ooooh thank you! I had no idea. I can run an extension cord from the right speaker over to everything on the left side outlet. hopefully that works! I don't really need earth shattering bass, I'm just really looking forward to my speakers being relieved of bass duty and the improvements that will come.

 

Try it, but ground loops can be insidious beasts to wrestle with. Sometimes even the internal ground scheme of a component can conflict with another apparently, which is part of the design and cannot be changed. I’ve not experienced that myself though. Also whether all your plugs are 3-pronged or not can have an impact.

 

Could the Kohzmo Pre be the problem? I'm considering getting a used Freya+ just to see if the buzz is still there. By all accounts the buffer mode is transparent.

Thank you for the help, at least now I have some ideas.

 

Chasing ground loop gremlins can bring a grown man to tears. Sometimes you need all balanced interconnects. Sometimes you need to snip the shielding on one side. Sometimes you need to tie a chassis ground lug down somewhere. Sometimes you need a ground lift switch in the chassis. Sometimes you just need to move a cable or component because it's picking up humm somewhere.

Just to check, does the hum sound like a 60/120Hz ?

 

Yes I think so.

Why do I have so much damn noise in my rigs?

 

How many sources connected to your khozmo?

Sometimes you have to disconnect everything, then plug one thing in at a time until you find the source of buzz.

 

just one, a Gungnir A1.

 

I thought that L12 only has 2 pin power on the plate amp, so it must be an interconnect grounding issue somehow no? What about se directly from Gungnir, does it still hum?

 

You mean the power plug is only 2 prong so plugging in to different outlets could not be the issue? It will be difficult for me to wire them all into one outlet so I’d like to avoid if it won’t help.

 

I can't promise the outlets won't affect it still as N is tied to E at the switchbox but I think with a 2 pin, sometimes work better on its own outlet away from the 3 pin devices? Ground loops are a confusing pita . I still think it's worth checking if wiring the L12 directly to the se out of gungnir makes the speakers stop buzzing before you throw a freya+ in there, because if it doesn't I don't think inserting the freya will help.

 

+1 on the ground loop thing if you're using separate outlet. I spent some time chasing this down here, too. In my system, I also had some DC Offset going on which was causing some buzzing in the transformer of my amp (not in the speakers). I tried turning off all the circuits in my house except for the one connected to my system and still had the buzzing - it was crappy electricity in my neighbourhood. There's an Emotiva powerbar that filters out the DC and that solved the problem for me. I would check out the grounding stuff first, though.