Axiom Home Page Forums General Discussion Advice from Axiom Owners Where to place additional subs?

Hey everyone,

Lately, I've been pondering the addition of more sub(s) to help flatten out the lower frequency across all listening positions. I'm looking for recommendations on placement. In studying the Harmon papers that JohnK frequently references, it appears 2 subs centered on opposite walls front/back is very good, as is 4 subs centered on all walls (more $$$).

I currently have an EP600 which does a great job, and I'm also using the Velodyne SMS-1 digital eq. From my primary seat I've created a very nice flat response (see middle graph). This graph was run with my SMS-1 mic from the primary seat in the front row. It was also taken before I made any adjustments to the eq, the end result was even better. However, running the sweep from other seats in the theater results in very different readings. This is why I'm considering the addition of another sub(s).

As most of you know I also treated my room with corner Bass Traps and first reflection Acoustic Panels prior to adding the SMS-1 to the equation. The addition of these treatments provided great results to flatten out my frequency across the seating areas (see bottom before/after graph). The improvements came after adding my front corner Superchunk Bass Traps. At this point I was using an EP500 and had not yet completed my wall/ceiling panels, or rear columns.

So, the question is where to place the sub(s), and which subs to get. As you can see from the below drawing, my right side is open into the rest of the room, which opens into a large hallway that leads you back to the bedrooms, bathroom, storage, etc. I only have that 6ft wall, so not sure placing a sub there would really be considered center.

The picture shows my EP600 below my center speaker and screen. In reality, it is currently along the left wall, below the first reflection panel, near the front left corner. This placement provided me the best graph using my SMS-1 from the primary seated position.

So what I'm thinking is to move it back below the center speaker as it looks cool there. Then, get a second sub to place along the back wall, to the left of the walkout doors. I would put it below that back window, however, really don't have a way to get a coax cable around the door.

The way it is now, I will have to run one around the room along the left wall floor. I plan to daisy chain it off of the line-out jacks on my front ep600. At some point in the future I suppose I could get two more subs and place one as far out as possible on the 6ft wall to the right, then place another one centered on the left wall.

If you look at my seating arrangment, in relation to the overall roomsize, this is what is difficult in deciding placement.

Budget is a concern, and I'm thinking about getting one of the new EP350v3's for that back wall. The specs are pretty impressive. I could get two of them from the FO, for the price of one EP500. Or maybe just one 500 would be adequate and I would never need any further subs, it is just the price is pretty steep.

So, what do you all think? Sorry for being so long on this post.

ps: trying to save up for a 1400-8, so keep that in mind.

One of the benefits of the SMS is that you can place one sub up front where you like it and another in your seat for testing. Walking around the walls while looking at the display will reveal your best placement options.

In that huge space I'd go for 2 350v2s rather than one 500. That would work better with your main objective of smoother FR across most seats. I'm currently running with a quad of subs in a 3500cf space, one on each midwall, and FR is about the same now in all seats.

So your saying one 350v3 on the rear wall and one centered on the left wall somewhere?

Hi Randy. You will want to experiment a bit but seeing how you are starting with such a nice graph I would leave the 600 where you have it currently, maybe move it more into the corner for the extra output then walk the mic around to see what gives you the smoothest response at the sweet spot. Might even be worth trying both up front in the corners, in light of your large irregular room. I'm sure you will find the right spot by walking that mic around. A 350v3 should mesh well with the 600. Also if possible, I'd try to find a spot the distance of the 600 less 3 feet to get the time delay aligned. You are still going to have to compromise a bit to balance FR across the seats but it should be smoother for everyone.

Well, this should be fun to watch.

Thanks John and Tom

I'm curious on feedback from others using 2 or more subs. Also, any ep350v3 owners out there. It seems the product description may be from the previous version? If I recall, the older 350 was recommended in rooms from 2,000-6,000 cf, I would think this new version might be able to handle more volume.

I know this has been discussed somewhere, but how did you create the db/frequency plot of your room?

Was that all done at a fixed location?

There are many ways to accomplish this:

1. Download the RealTraps tones and plot a graph or import into Excel. You will need an spl meter to accomplish, takes about an hour.

2. Use RoomEQWizzard free software from Home Theater Shack forums. You will need a HTPC and SPL meter and decent soundcard.

3. Use the Velodyne SMS-1 subwoofer EQ system which will create a graph with included mic.

4. Plus many other products available.

In most cases you are taking the readings from the listening position.

3.

What do you set your volume to on your receiver? Did you set it so that the test tone from your receiver was 75 db or what?


Thanks

Depends on the product used, they each have their own instructions. It is an addicting habit, worse than buying audio equipment and speakers. Just sit back and enjoy.

Randy, one on the back wall and one on the side wall wouldn't generally be the idea. Middle of both side walls or front and back walls work to minimize the effect of room modes by being located at points where some modes are at a minimum(middle of the wall)and tending to cancel other modes by being opposite each other where those modes are in opposite phase.

Thanks JohnK,

Yes, I am planning on putting my 600 below my center screen on the front wall, and then get another sub for the rear wall next to the walk out door. What do you think would happen if I added a 3rd sub for the left wall? I would think 3 might be a little better than 2. Or I could put a 350 near each corner of the back wall.

Well Ian had said 4 subs is nearly ideal so 3 would be 3/4 to ideal. I would think the other 2 2/3 of the way down the side walls would work. You could also try one 1/2 way down and the the other all the way to the back just see which works better in your situation. After all it is about building up the low points so positioning is the key.

I think you are going to need to do some work once you get them. It is all just speculation until they are installed.

Although a third sub at that location would increase the overall sound level, it wouldn't have the mode minimizing effect that two at the middle of opposite walls have. I'd stay with two of the best possible(if you don't go to four....etc.).

While its true that the greatest change in flattening nodes occurs when adding the first sub, adding subsequent subs also contributes to smoothing nodes, as well as increasing headroom and lowering distortion. I found that going to 3 from 2 subs further improved FR but required tweaking placement and phase again in all the subs.

The Harman study does provide idealized locations but the exact location in Randy's room will be influenced by the location of his furniture and its slightly irregular shape. That's why the SMS-1 mic technique makes finding the ideal placement a snap.

It also seems to me that if there ever was a case to be made for colocating a pair of subs, its Randy's huge room. One alternative is to colocate a pair of 350v3s for an extra 6db output from coupling. A pair setup that way would provide max SPL of 113 anechoic, 124 db in room according to the Axiom stats. Along with the 600 that should give give you enough woofage for that 9000cf space and still give you some benefit of smoothing FR.

Can somebody refresh my memory, what is the difference between the EP350 and the new EP350v3?

I may be oversimplifying but if the main benefit of two subs on opposing walls is wave cancellation of the room modes caused by reflections resonating after the first direct sound was heard.... would this improvement be mostly negated by large items of furnature between two opposing subs. A couch for instance?

I think the answer is Yes as evidenced by the fact in these example rooms and graphs, the furniture was always shifted in the example pics to allow the subs to have line of sight to each other, when used in opposing configuration.

Hearing things is hard work....

Example rooms and graphs.

The new 350 now uses the EP500 cabinet and is 300 watts, up from 200(?). It also has a "nifty" circuit for extra bass output.

Thanks Mark, the reason for the question is that I had a ponder to drag the old 350 out and connect it up with the 600 ... don't know if that would work or not. Seems like somebody (Brent?) told me it would not be a good combination some time back.

I believe it was framer2180 who has both versions. Try PMing him as to the actual acoustical differences.

It wouldn't hurt to try. Drag that baby out of the closet and give it a try. Nothing ventured nothing gained.

Yeah, I'd give it a shot.

I've been thinking about it, may just do that.

We should have done that when I was there.

Yea I was just thinking that same thing Rick, don't know why we didn't.

Wait...

I do know why. We should have sent the womenfolk on a day long shopping trip and then we could have messed with all kinds of combinations. Write that down for next time.

No kiddin, that could be an expensive test though

... I'll start saving up.

Whoa, that thing is scary Rick.

Speaking of mismatched subs, I use two small sealed 10" subs with my Hsu VTF3 mkII. Although, not ideal--the smaller subs strain during some movies--the benefit of smoothing out the bass in my room is noticeable. I had the subs tucked away in the closet unused, but I figured if I got 'em I might as well use 'em.

In sending Amie a PM, who touched base with Ian, they said the new 350(s) would blend nicely with a 600. The best setup is identical subs, but the more woof the better, no matter what brand.

Also, RickF, he said you can hook a 350 up to the line-out on a 600. Not sure why Brent would say differently.

Another reason I'm considering 2 350v3's is because of the freq range up to 150hz, where the 500 has the brickwall at 100hz. Might help fill in the dip I was getting above 100hz in my graphs?

I have 2 10-inch sealed subs on order from AV123. I plan on first trying them with the EP500 before moving them to 2 channel duty with my M3 systems.

Because of the new size of the enclosure the tuning frequency (Fb) of the 350v3 sub should be reasonably close to that of the 500/600 so it should mesh reasonably well with the larger EP subs. Generally speaking, the more Fb differ the tougher it is to get them blended with each other.

Randy, he didn't say they could not be connected together ... he said they would probably be way mismatched. I believe he also stated that he, at one point had an older version EP350 connected with his 600 in a 2500cf(?) room and the 600 so overpowered the 350 that the addition of the old 350 wasn't worth the effort. Maybe the new 350v3 will be a better match. I believe this was Brent telling me this, again ... I *could* be wrong with the name.

I forgot that you jumped on that special. That should be a great two-channel set up. Where do you plan on placing the subs?

When I ran two subs in my previous two channel system I preferred the subs right next to the main speakers. Didn't like them so much space out around the room. That's just me, though.

Andrew, since the sound at these very low frequencies is essentially omni-directional, the large furniture items that you mention shouldn't have a significant effect on the cancellation factor.

This is kind of a crazy question, but has anyone mounted a sub up on a wall, near the ceiling? Of course you would have to have a sturdy shelf or chain/rope suspending it to the 2x6's.

The reason I ask is because if I get a second sub and place it on the rear wall directly opposite my front sub according to the Harmon White Paper, it would be where the walkout door is, however, I have plenty of room above the door since we have 9ft ceilings. It might be interesting how well it works.

I could see it working, but more likely on a shelf of some sort. Wouldn't the driver movement cause it to rattle chains?

I suppose your right about the chains. I'm pretty sure it could be done as I would be going right into the 2x6's of our exterior wall. I'd probably try using two ladders to test it before I tried figuring out how to mount it.

I wouldn't worry too much about adhereing closely to the midwall points since its unlikely those will be the optimal spots given your unique room configuration. Also hanging subs is not something worth attempting given all the energy going through those enclosures. Guys that have tried it invariably put them back on the floor owing to the additional noise from the shelves and the danger of vibrations causing the sub to fall.

That's good to know - Ian's always eyeing up the back wall for mounting another subwoofer 'out of the way'. I leave the house in fear every time . . .

Too funny. LOL

I'm really intrigued by the notion of putting the sub "in mid air" somewhere.

to me I would think there would be little difference between floor/wall and ceiling wall, not sure.

Didnt we have a poster here at one time who had his 80s hanging from the ceiling and one of those built in subs ... what are they called?

I remember that picture....hmmmm

I distinctly remember him talking about how the 80s hung... hanging from the ceiling like that really bringing out SRV's tone, that's what really caught my attention.

Well, personally, I sit much closer to the floor than to the ceiling, so I'm willing to entertain the notion that there could be a difference or advantage

There was somebody else who was talking about putting a sub up on a plant shelf in the sunroom.

You know, I have a pretty big plant shelf in my living room. Hmmm. But hoisting a sub up there could be quite an engineering feat.

Pictures would be a requirement--not of the finished product, but the journey there.

Randy, there're a couple reasons for not being so concerned about precise placement that you'd consider suspending one of your subs: first, an examination of the both the null and cancellation diagrams in the article shows that they don't suddenly go from one extreme to the other, but instead follow gradual curves. So, if placement was a little bit away from the point of max null or max cancellation there would still be benefit. Second, your room isn't completely rectangular and the modes in an irregular room have a somewhat different distribution and are a lot more difficult to calculate, as some online sources show. It could be reasoned that placing your back sub farther to the right, more nearly in the middle of the back wall rather than directly opposite the front sub, would more closely coincide with a null in the rear area.

Thanks everyone for the help, it is much appreciated. Since my HT area is in the top/left corner of the overall room, I've been trying to imagine how that compares to a rectangular or square room.

Also, between the bar and the wall is a large entryway/hallway (8ft wide) that leads to the otherside of the basement which includes the stairway, bedroom, bathroom, and storage rooms. Overall Sq Ft is 2100sq ft.

The 6 ft bump out wall which makes up my AV closet was actually built by me to help set back the projection screen from the rest of the room. In reality, the room was like 31ft x 30ft before I added that bump out area. I'm sure I will have to experiment to find the best position.

I just need to figure out what I'm going to do....

I remember the M80s hanging from the ceiling.

I don't know what subwoofer you're talking about being built-in, but you made me think of the Thigpen Rotary Woofer, which "must be professionally installed in an attic or basement which becomes an infinite baffle." Does anyone on the board actually have experience with those?

And some from the ER visits as well....just in the interest of keeping the photo essay complete!

Good thinking, Mark!

Typical cost after installing one of these is between $20,000 and $25,000 !

Are you excited because that's pocket change or your retirement?

Thanks to my good friend Rick (Wid) for finding the pictures for me, here is the room with the hanging 80s and the *infinite baffle* sub I was referring to ... Rick also had to tell me the subs name because I forgot.

Here's the photos...

Hanging 80s, Infinite Baffle Sub ... Anybody remember his screen name?

'I get by with a little help from my friends'

I belive it was Mikey

Oh, what did I do ... forget to ask you *that* question?

You sure did

Just to let all of you know, I decided to go with 2 350v3's versus one 500. I think with my unusual sized room (non square/non rectangular) this setup will give me the most flexibility in finding a happy comprimise between FR and output.

only time will tell...

Sweet!

I assume you are getting them with the ebony finish?

yup

Very cool, Randy!

Yeah thanks Sean, now I have to figure out where to place them all.

This is where everyone says, "In my house."

Randy,
I'll be interested to hear your opinions on the new 350v3"s. I have recently purchased a larger home which to my delight has a games room that is 14' x 28'. I am planning on ordering a new speaker system and was thinking about the Epic 80 with the 500 sub. Finally, I will have a complete home theatre!

I'm anxious as well to see the improvements of this 350, based on Alan's post. When I first started with Axiom I had a 350v1 which did a decent job upstairs, and even in my huge rec room/ht area. Then I upgraded to a 500, which was unbelievable, then the 600 which was even more unbelievable.

I'm guessing with the step up to the 500 enclosure, bigger amp, goosed up special circuit, that it will be much improved sub. I'm hoping 2 of them will help me even out the FR across all seats.

Now when are they going to make a v4 of the 350 in a 600 cabinet?

Just picked up one of these from Radio Shack. Plan to run the 350v3's through the SMS-1, and just leave the 600 by itself since it is DSP controlled. Now I have to figure out placement of these 3 subs.

Randy, what you indicated in your first diagram should be fine: 600 front and center, 350s in left and right back corners.

I'm also thinking about trying 350's up front spread out a bit, and the 600 either on the back wall, or nearfield left wall behind the seating area the same distance (delay) as the 350's.