Best 4 manifold placement ?

[point123]

Hi

I have four manifolds consisting of 2x18s in each. Two manifolds at the front on either side of the room and two at the middle of the room.

I sit in the middlt of the room so two manifold are just a little in front of me on the ceiling I was thinking of moving these two at the rear on either side of the room. Would that be a better option ?

[ThomasW]

Hello

The only way to know for sure is to use something like Room EQ Wizard to measure the in room response.

Also it might be beneficial to use bass traps if the space permits

[point123]

Ok hope I’ve explained myself correctly sorry if I didn’t make sense first time round.

Is it ok to have two manifolds at the front of the room and two manifolds at the rear behind my mlp ?

I did read that having manifolds behind your mlp is not recommended.

I have a ceiling build.

[dan77]

there is no outright “no no” when placing subs. It really boils down to preference.
The one thing that is not subjective is room nulls. That is why Thomas recommends you use a modeling tool. You can only treat room nulls by moving the sub. DSP only bandaids it. And many times, that bandaid does not work well. Room nulls can lead to very poor bass profiles. A room null where you are sitting can be very detrimental to your listening enjoyment.

Before I go any further, here is the equipment spoken of below. My IB’s are 2 manifolds, 2 15 inch Fi each, located in the floor roughly below the acoustically transparent screen. The ‘subs’ are SVS SB-3000’s. Yes, I own 7 of those. 6 are for my HT. They go in and out of the HT based on whatever current config I am setting up. They are a very capable sub by the way! They are rated to 16hz and REW shows me that they really do go that low.

Here is my experience and only reflects my personal preferences.
On many forums there are 2 camps on the whole “sub behind me” conversation. I am lucky enough to be able to move my subs all around my HT. So, after reading about some people swearing up and down about how amazing it is, I set my room up with my subs in each corner.

I ran my HT for about 9 months that way (4 subs each corner 2 IB’s)

I then read that you need “mid level bass” (MLB) subs physically touching the back side of your seat. So I added 2 more subs to do that. I was up to 6 subs, plus my IB subs in the floor.

I ran my HT for about 4 months like that (6 subs 2 IB’s)

Then I moved all my subs to the front of the MLP keeping the MLB’s

Then I removed the MLB’s and just kept all the subs in front of the MLP

In each case I had the subs running managed bass (steerable bass) and then I would wire them up to run LFE. Yep, I like to tinker!

Here are my impressions of that whole situation:
Having subs all around you is like a Disney ride. Sounds are coming at you all around and at first is very welcome and fun. When I added the MLB’s a whole new level of “impact” was found and I liked that as well. Certainly nothing wrong with this type of setup. I think that first impressions by an average non-discerning listener are most wowed by this type of setup. It brings quite the cacophony of sounds to your ears. I mean, I did go 9 months with the arrangement, so it is not the most offensive situation for your ears.

Then, I went to a store that had a high end home theater demo during a sales event and noticed that even though I had more capable bass (by a large, large factor), My setup did not have the same impact that their system had. Basically this means “timing” (though standing wave issues factor in here as well). The more you move subs around your room, it becomes very difficult to time them properly. So you have a lot of bass, but “impact” and realism, lacks. I ran REW just under 40 times and got all my subs timed very well, but even then I did not feel like it emulated that high end HT at our local high end store called “Listen Up” here in Denver.

So I moved all my subs to the front and timed them again (after over a year of playing around with other placements). This time, the wave front hit me like a brick wall. Gunshots, door slams, engine growls, lightning, etc all have an attention getting reaction compared to the “Look at me! I have bass all over the room!” approach. With subs in the 4 corners you get the sound all around you and is fun, but with subs in front you get realism and a more primal attention getting reaction (due to the realism and accuracy of the wave front).

These are just my impressions. It must be noted, if not already obvious, I try for an immersive and realistic HT. I spent most of my young life with used/knock off/diy subs. And if I get a whiff of that cheap sub sound, I step away. Subs all around me begin to remind me of those early days when sound everywhere seemed awesome. But it is just not reference level quality.

Full disclosure, I am one of those people that can readily echo locate a single sub. I simply must have 2 subs in order to enjoy any listening environment. Even in my office I have 2 subs.
That was the big drawback to the demo room at Listen Up as well. Yes, their bass was well timed and had epic impact, but I could hear where the single sub was and that was distracting to me.

Some people swear by having a sub in each of the 4 corners, or 2 subs up front and 2 subs on each side of the MLP (see my profile pic for this particular setup). I have tried these combos trying to learn what would be best for me. And for me, having all the subs in front of the MLP provides the best immersion (sound profile) and impact (properly timed bass waves, but also the best standing room wave approach). The “Disney ride” type of bass is fun without a doubt and a crowd pleaser for sure, but for me, I don’t feel it is immersive or realistic. Bass from all sides (for me) is just a “tour de force” of “listen to what I can do with all my speakers!”. 

As a final comment, I think I will be placing the MLB’s behind my seats again in the “final” (wink, wink) configuration. Right now I have everything in front of me, but sometimes I do miss that MLB kick behind me. Seems to depend on the movie and how it was mixed.
So the tinkering seems to never end : )

[point123]

Wow thank you so much for your detailed informative reply. Really appreciate it.

May I ask what MLBs are you using never heard of “mid level bass” are they sb3000s sealed boxes and do you run a separate mini dsp and cut them off at a certain frequency ?

[dan77]

A MLB (Mid Level Bass) sub is just a/any sub that is well suited to frequencies between 50 and 200 hz. I like the SVS SB-3000 subs so just bought 2 more of those and placed them directly behind the MLP. The front grill just touches the cloth on the back of the seat.

This is important for me as my L/C/R speakers can only go down to about 90hz with authority. I don’t have honkin’ big front speaker cones. If you do have fronts with big honkin’ 10 inch woofer cones, you may have all the mid level bass you like.

Mid range/level bass is something like 70hz to about 150hz (not a rule in stone that I know of)

So I read on a few forums that MLB subs fill that gap. Especially in a case like mine where I am using IB’s along with front speakers that aren’t rated very low.

Some movies it really works, others it can be a bit overdone. So I find myself turning them up and down a bit per movie. All that is probably just because I run all my subs (MLB in this case) a little too hot. But I am a bass head at the end of the day, so of course I’m gonna crank’em up.

The trick for MLB’s is no different than actuators (Crowson), IB’s or any other speaker, they must be dialed in for SPL, EQ and Crossover.
The nice thing about the SVS line is that they are app driven, so I just sit in my seat and adjust away during the movie till I get it “right” and then just enjoy the rest of the movie. It can be really fun!

I have the mini DSP 2x4HD, but I use that for my IB’s and my 4 other SB-3000 subs. Super convenient. Just got the little add on that makes the 2x4 wireless so you can make the adjustments from your phone. Can’t wait to get that up and running. Currently I use a laptop with a really long cord to the mini DSP as my equipment room is in the basement.

On a side note, if you have not heard of Crowson, check them out. They are NOT shakers. Shakers are just a speaker without a cone, and are rated as such (meaning they are rated just like speakers, cause that is what they are). Crowson actuators are rated to 1hz flat. That is a spec that no speaker or shaker can begin to compete with. Crowsons are not a modified speaker.

Ok, I take it back, there is one ‘speaker’ that will go to 1hz, and only one in the world. It is called a Rotary woofer. But, you can’t install it yourself and it costs about 13k (not sure if that includes labor/material for the install)

Anyway, the Crowsons with the MLB are a formidable combination for car door closings, explosions, gunshots, earthquakes, etc.

Of course it goes without saying, that if you don’t have an IB setup for your basic LFE sounds (and most likely your managed bass as well), then you are not playing with the heavyweights of the HT world when it comes to bass. Just gotta throw out the obvious!

[point123]

Ok that sounds interesting.

Yea I do have my LCRs which are capable to play down to around 30hz I think but do have them crossed over at around 60hz.

Yea I’ve heard of crowsons but abit too expensive for me here in the uk. Heard some really good news about them. I do have some bass shakers in my chairs which have been dialed in ever so slightly as my IBs do give out alit of tactile effects I also have two diy 15” sealed boxes one at the front of the room and one at the rear.

I am happy with my bass response but like most of us enthusiasts we are always thinking “what if” so that’s why I brought up the question of rear IBs in the ceiling it was on this forum that I had read it’s not a good idea to have rear IBs but needed to get confirmation as to why.

dan77 you have great set up! Wish I had a dedicated theatre room.