Got a new toy. Calling all sub setup experts

[EdmundGTP]

Monday afternoon I took delivery of an eD A7-350. It's definitely not small... Again disregard my hideous linoleum..

So now I have a couple of questions. Theresa pretty crude diagram of my set-up below. Each of those KSP's has a built in 15 inch sub which are now being powered by an outboard amplifier and processor. I plan to roll off the signal to the KSP's at about 25-30 hz and let the eD pick up the slack below that while also augmenting the KSP's with everything from 80 hz down. In the diagram, I have a few prospective sub locations picked out. Im wondering if anyone can suggest which may work best simply based on looking at my room geometry. To help you get an idea of how the diagram is laid out, the photograph above shows the sub in the "open entryway" area, looking left into the living room. Obviously its a little more complicated than just that, but any input helps. I've listened to the sub in all of those spots except for the one between the leg of the couch and KSP-R but not very extensively. So far the location directly behind the couch seems to work best.

But I havent measured anything yet though, and that brings me to my 2nd question. The processors I have will give me the ability to EQ the KSP subs and the eD sub indepenently of one another. So in my case, would it be better to eq each of them by themselves, or do them both together? My first guess would be to eq them as flat as possible individually, then set the levels of each to match, but I'm no pro at this. Any opinions at all would be helpful. Thanks!

[Chris A]

So far the location directly behind the couch seems to work best.

You might try moving the sub as close as possible into the corner behind your couch, even try turning the business end of the sub toward the wall, leaving about 6-12 inches between it and the wall. If you have a measuring device, you might check to see the difference in lf extension by doing this.

If you are thinking about using foldable partitions or a wall-like barrier (you can temporarily stack bass traps or large boxes full of "stuff" so that the top of the barrier is about 4 1/2 feet high or higher, and about the same width), try putting it up behind the couch and moving the sub to the forward corner, thus moving the rest of the couch, TV, and other stuff slightly toward the dining area to allow the corner placement. I'll guarantee that this will improve your lf performance by 6-12 dB at 25 Hz or lower. Try moving the partitions back and forth a bit and check for the room modes that will change. This will save a lot of headaches using acoustic panels on the walls or ceiling, etc.

Chris

[CECAA850]

I've never liked a sub behind me, but if that location works best for you then so be it. I would think that the phase issues you'd encounter with the sub behind you would be remedied by having the sub in the same plane as the mains. Setting up multiple subs is tricky. Make sure you have an SPL meter and check output at the listening position every time you make a phase change in any of your subs. Be sure to play test tones around the same frequency as your crossover point to check for cancellation between your mains and your sub. It's also a good idea to have someone help you as you adjust your phase so you don't have to keep going back and forth from your sub to the listening position for a measurement. Start by calibrating one sub, then match phase and gain with the second one. Add the third one after you have the first two dialed in. Have some patience as it's going to take some time to get it right.

[EdmundGTP]

Thanks for the input so far. The rest of my evenings this week will most likely be spent pushing that thing around and taking measurements. Lots of good tedious fun. The one thing I'm definitely no expert on is the whole phase thing. The only phase adjustability I have for either of the subs (KSP subs, or the eD) is a direct 180 deg. switch. Not a variable dial. Though I've read that altering the "sub distance" paramater on my receiver can be useful in adjusting for phase issues. I guess what I'm most unclear on is, how do I even know if I have a phase problem to begin with, and once I start tweaking knobs, how exactly do I know its set up correctly? Is it really a case of just changing things until it sounds the best, or is there some quantifiable way to measure it, or even certain indicators to look (listen) for? The other thing I forgot to mention, is that I'll only have the ability to adjust/eq the KSP subs as a pair and not individually. The processors I have are all 2 channel, and my plan was to use one channel of them for the KSP subs and the other channel for the eD. Obviously not the MOST ideal, but it's what I have to work with for the time being.

[Chris A]

My first guess would be to eq them as flat as possible individually, then set the levels of each to match

Actually, a lot of folks try to EQ flat, but there is evidence that you should EQ to a rising response, something between flat EQ and "room gain" EQ (there are JAES papers on this subject). I would try the mains without a high-pass filter (without lf crossover) first, then try with high pass set at about 40-60 Hz.

...would it be better to eq each of them by themselves, or do them both together?...

I would make sure that phasing vis-a-vis your mains is good using one sub at a time. This will ensure proper electrical phasing, and get close on "acoustic phase" (or delay settings, if you are using your AV preamp). After you check and set each sub separately, then I would turn them both on for EQ.

[jacksonbart]

That linoleum ties the room together

[EdmundGTP]

That linoleum ties the room together

It really ties my gag reflex together too. I'm in the process of replacing it all with tile. It's just turning into a rather long process. I'm sure it must have been the pimpest of pimp flooring back in '71 when this house was built but nowadays not so much.

[CECAA850]

Check your phase with an SPL meter. Here's an easy way to see what phase does. Play a test tones through your mains (sub). Sit in the listening position with your trusty meter. Turn your eD on with the gain off and slowly bring it up roughly to the same level as your other subs. Have your lovely assistant slowly adjust the variable phase on your eD while you watch the meter. You'll notice the reading go up when the sub is in phase with your mains and go down as it cancells the bass from your mains as it goes out of phase. You can see that if your not careful with phase that you can actually add an additional subwoofer to your room and have less bass at the listening position than you did with one sub. On your setup, I'd leave the mains' sub at the 0 setting and adjust the eD from there.

A word of caution. It's fine to use sine waves to set your system up. They do NOT have to be loud to make your phase adjustments. They should be loud enough to register on your meter, but not house shaking. Prolonged sine wave signals to your subs at loud volumes can cook the voice coils.

[EdmundGTP]

Thanks. A few weeks back I managed to eq the subs in my mains to a fairly decent response curve. Flat to within +/- 3dB or so from 30hz to 80hz at my listening position, and that was with using identical eq filters for the left and right tower. I think my average volume when taking measurements was only 75-80db. I think I'll mess around with some of that phase setting business tonight after work.

[CECAA850]

Flat to within 3dB from the listening position is just about unheard of. You'd need virtually a perfect room. I'm not saying that it can't happen, but I've never actually seen or heard of it outside of using a bunch of bass traps and a PEQ. You're very fortunate.

[EdmundGTP]

Well.. That flat, is relative to what I was using to measure it, which who knows how accurate that is. I used a radio shack spl meter, and plugged the values into a spreadsheet from the hometheatershack BFD manual measurement thread, which has the meter calibration values entered in. Also, I said flat to within plus OR minus 3 db, which is really a 6 db total spread. I did use a PEQ though to smooth the response.

[EdmundGTP]

I spent a good portion of sunday pushing this thing around and taking measurements with my trusty (lame) radioshack meter and figured out the place with the smoothest response. Turns out that even the direction which the driver points made a significant difference in how smooth or "dippy" my response measured at. I ended up putting the sub pretty-much right where the CD towers are in that picture I posted above, directly below the right surround, and pointed the driver/port directly backwards at that corner where the lamp is. Prior to all that pushing around, I eq'd the KSP subs as best as I could and came up with the plot below.

The Low pass xover was set to 100 hz and I used a high pass xover at 25hz. I stopped recording data at 100 hz so the data above that is leftover from other measurements I did. Same with the following two graphs. So next I eq'd the ED sub and got the following. Apologies for not having a before and after. In haste I overwrote the original data for both of the following graphs. Yes the level on the ED sub was set way too high compared to the KSP's and is also reflected below. Again.. stopped recording data above 100 hz.

So after that I matched the levels of both a bit closer and measured them both at the same time.

The only thing that Im not really sure on, is why I actually got readings below 14hz on the combined graph but not with either alone (the meter only reads down to 50db). But as before, I stopped collecting data over 100hz, and after measuring I turned the xover back down to 80, because that peak at 90 was bothersome. The extra low end output of the ED sub is an awesome improvement. Even without the 25hz high pass on the KSP's their response dropped noticeably below 30 hz. I havent had a chance to put this set-up through its paces yet. I'll probably tweak the sub levels a little bit more as the week goes by and play through some good sub demo DVDs.

[CECAA850]

Your end graph looks great. Setting up multiple subs is really a chore when done correctly, as you have done, but the end result is worth it. Many people just throw another sub in the room and call it done. They never realize the second subs potential and sometimes end up with a worse sounding set up than before. The only other step I'd take is to play some music. Find something with a good bass line in it like blues or jazz. Concentrate on the bass guitar and kick drum ( I normally close my eyes for some reason ). Tweek your phase slightly untill you hear the sharp initial strike of the drum and the clearest, tightest bass guitar and your there. When your completely done, you should be able to listen to your set up and not be able to tell that there's a sub in the room. It should sound like all the music is coming from your mains.

Your observations about the subs response changing with the slightest movement of orientation or placement are spot on.

Great job.

Carl