Position of Subwoofers on Baffle Wall - Advise Needed.

LittleNipper

Well-known Member
I'm about to build my baffle wall. And to be honest, I don't know the best position for these subs.

As you guys know more about subwoofers than I do. I thought I would ask for a "gut" feel on this, because i can't position, measure and then re-position as required.

They were purchase via this thread (500 w x 780 l x 170d sealed) :-

The spec for the speakers are :-

The LCR are JBL 3677's with L & R slightly toed inwards. The baffle wall will prob. be constructed :-
2:35 AT Screen 3.2m x 1.4m
Room 3.6m x 4.9m ( will be treated ).

Baffle Wall Construction :-

Ply ( 9mm min )
2.5mm Techsound
12.5mm Plasterboard ( Blue stuff )
20-30mm diffusion / absorption to resolve issues with sound bouncing back of AT screen.

So, my questions are (answer as few as you like):-

1. Position A or B or C.
2. At they are 1 Ohm speakers, run them all together ( so 4 Ohm ) or as two sets of 2 Ohm. ( A Trinnov 16 will be controlling them ).
3. How much power (amp) do I need ?

I do have some other subs ( to be placed at rear of the room ) that will go down to 22hz. I don't want any lower ( ATM ).
 

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LittleNipper

Well-known Member
NOTE: The drawing is to scale. None of the speakers or subs are light. Prob. 260kg of speakers on the baffle wall.
 

LittleNipper

Well-known Member
Did find this, which would indicate I should be rolling off this sub at about 37hz. Which doesn't sound too low. Which makes me think of trying to go with option 1. but stacked vertical, which would mean removing and replacing be a lot less disturbance to the room as I could do a separate panel to sit infront of them. Equally the cones would not be behind the AT screen.

 

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Conrad

Moderator
If L/R sit about 1/4 across the front wall then I'd go with option C.
1/4 points often provide a good response across a reasonably wide range, especially if you sit about 2/3 depth in a relatively symmetrical room. There's a lot of assumptions there.

C will also deal with some height modes, not that they're usually an issue.

Have you tried room sim?
 

LittleNipper

Well-known Member
If L/R sit about 1/4 across the front wall then I'd go with option C.
1/4 points often provide a good response across a reasonably wide range, especially if you sit about 2/3 depth in a relatively symmetrical room. There's a lot of assumptions there.

C will also deal with some height modes, not that they're usually an issue.

Have you tried room sim?
I've not tried a room sim, perhaps because I might not understand what options I am entering whilst using it. I think I recall REW might have something. What would you suggest I look at for the room sim ?

Option C. Does mean I can put vertical 4 by 2's up and create this set up quite easily. It would also mean I could get hold of all of the cables ( for all speakers ) quite easily.
 

simonb3665

Active Member
Agree with Conrad, C is the option if you don't have the opportunity to experiment. Keep the drivers close to the boundaries.
It will maximise room modes and give you a good chance of a smooth response.
Amplifier wise a Behringer nx3000 or crown xls1502 would be the cost-effective way to go. The crown is less fuss (no fan mode required/choice of cable)
Wire in pairs to 2 ohms getting a health 300rms each. This would give you the opportunity to eq/time-align the pair.
Drivers have 15mm xmax so pretty reasonable for a 12 and a bit of eq will give you plenty of 20hz output.
 

Conrad

Moderator
Room sim is a function within REW.
Just add in the dimensions, your seating location and the driver locations for the subs and it'll give you a predicted response. It'll help you see if there's much of a difference between the options you have.

A would likely work well, it's a nice wide array.
I don't like B, it's all a bit central, you're basically colocating which defeats one of the main reasons for using multiple.
C has a nice broad spread and should have a real sense of scale.
 

LittleNipper

Well-known Member
Thanks both @Conrad and @simonb3665 for your comments. I will give REW a go tomorrow.

Oddly enough I have a spare Crown XLS 1502 & Behringer nx3000. I was going to sell the nx3000 as I need to use windows to do the cross overs, however, with the Trinnov I should be able to do that from that unit. For some odd reason I seem to have a JBL MPX600, so no shortage of amps to test with. At the end I will just sell on what amps I don't use.

The other good thing then about C. is that I can ensure the drive units are outside the range of where the AT screen is. And I can get the edge to about 48mm off the boundary's.

To balance these out. I've a couple ( don't laugh ) of JBL 4645C's I can put on the rear wall of the room. I can move them around a fair bit as I won't have anything in the back of the room, so can have a good play.
 

LittleNipper

Well-known Member
@Conrad and @simonb3665 well, that's a very useful tool. I have mad a donation to the developer.

I've got one row of seats and the frequency is quite consistent over them L to R. Oddly enough the position I've place the MLP for best response is pretty much ( give or take 15cm ) where I had expected it to be. Very little variation left, right above or below.

1. Peak at 70 Hz.

The only way I seem to be able to do anything about this is by absorption to the front and rear wall.

Front Wall

So, behind the front wall I've got approx 330mm depth. I can fill with rock wool and then add holes ( symmetrical of course ) to allow sound in. To the rear I can build limp mass loaded vinyl panels to increase this absorption.

Rear Wall

The MLV I will prob. use ( Panel Sound Absorber ) to build something specifically for that frequency as I have a sh*t load of TecSound left over !

2. Drop off after 80hz.

If I increase the crossover filter, this smooths out. As I have Procella P5 which don't go too low, I could raise the cross over to perhaps 110hz. Additional absorption / reflection ect on Left and Right wall seem to assist smoothing this somewhat.
 

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simonb3665

Active Member
I like the room sim as a guide and its pretty accurate for the big room modes. Put some time delay on one side and see what happens.
Great if you can add some absorption but I would be shocked if Trinov optimizer cant get a smooth response from 6 different driver locations. Depends how large the listening area is I guess.
 

Conrad

Moderator
Check the box: Time align speakers and subs, and then check the box: Time align subs individually. You might improve the predicted response.

You can turn the XO filter off unless you're looking at mains integration.

Treatment to deal with a 70Hz mode will need to be very thick. You might be better off adding a minidsp which will give you much more flexibility than your Denon.
 

LittleNipper

Well-known Member
Check the box: Time align speakers and subs, and then check the box: Time align subs individually. You might improve the predicted response.

You can turn the XO filter off unless you're looking at mains integration.

Treatment to deal with a 70Hz mode will need to be very thick. You might be better off adding a minidsp which will give you much more flexibility than your Denon.
@Conrad I've seen the minidsp has some great features for dealing with these issues... Well, not dealing but at least a tool to help restrain them ! I'll update my footer as I will be using a Trinnov 16 in this room. But even in that situation I understand the minidsp can assist.

This is my final layout and to build I will need ...

2 4 by 2 @ 3.6 ( top and bottom plate )
6 4 by 2 @ 2.4 ( verticals )
3 4 by 2 @ 2.4 ( spanning between verticals to support LCR and framing of ply / plasterboard

3 sheets of ply

The screen ( shown on the right ) means the mid of the LCR is ⅓ of the way up the screen and the bottom of the (visible) screen is 400mm off the floor. Ear height being 800mm. This also means the brackets for the screen fall nicely just below the top subs and with it being clad with ply behind the additional build up, it will be a good fixing.
 

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Conrad

Moderator
I use a minidsp with my Trinnov to EQ fur subs. It saves channels and gives me a great result. Depending on when you get your Trinnov they might have their new bass management software in place. If that gives me better results than MSO then I'll use it, otherwise I'll stick with the minidsp.

If you're planning on buying a minidsp I'd wait until you can get a flex. Slightly more expensive but they're quieter devices by all accounts, something the 2x4HD isn't very good at. I'll be upgrading when they're in stock again.
 

LittleNipper

Well-known Member
I've been so careful with the purchasing of all of my equipment so far I have some funds in reserve for ancillary items ! So, thanks for the heads up on the product. I presume it's this :-

 

Conrad

Moderator
That's the one. Either balanced or unbalanced, although if you're using it with a Trinnov I'd recommend using the digital outputs from the Trinnov into it which avoids and AD conversion and keeps the noise even lower. I'm using it now into a 2x4HD with a 20m run and it's better than when I was using analog.
 

LittleNipper

Well-known Member
I've built the final walls in my room now. So, hopefully tomorrow I can do the baffle wall. With wiring and 6 pretty large speakers going in, it will be an interesting build as I also need to account for accessing cable positions for the subs.

Now, traditionally people stuff rockwool into the void behind. I do have quite a bit of TecSound left. I could put 3 1.2m drops in, handing 'free'. I understand this is a good way of damping bass sounds as well.

I have the option of either doing this, or sandwiching the TecSound inbetween the plywood and the facelayer of SoundBoard ( Blue plasterboard ) before some product ( unknown ) to handle the reflection coming back from the AT screen.

What are your opinions on this ?

My feeling is, I can only do this now and if it doesn't work, I can quite easily stuff it with rock wall later, but not the other way round.

As this is a baffle wall thread, I will update with pictures of the construction of the baffle wall as others might find it useful.
 

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LittleNipper

Well-known Member
Oops... This is how the subs and LCR are being done... At ¼ room width.
 

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stevie0

Active Member
Very happy to see this thread @LittleNipper
I bought the remaining 12 (1 without driver) and also have LCR of JBL 3677's.

Not quite sure what I am planning yet but I will watch with interest your build 👍🏻
 
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LittleNipper

Well-known Member
Very happy to see this thread @LittleNipper
I bought the remaining 12 (1 without driver) and also have LCR of JBL 3677's.

Not quite sure what I am planning yet but I will watch with interest your build 👍🏻
To be honest I have no idea what to expect from these subs, but I thought why the hell not !!! But 12 - Wowza. I used REW to see where I'd get the most even sound for them and then positioned relative to where my screen is going so no drivers are behind the screen. I was going to mount in the wall on the supplied brackets, but as they are so darn heavy, I'm sliding them in on top of some TecSound, which is pretty grippy stuff and should resist vibrations going through to the main carcass of the baffle wall. If it doesn't and I need too, well I can refit them and attach that way.

I'm certainly looking forward to listening to the 3677's in it. I've compared them to my MK Sound speakers and prefer the directness of the compression drivers. I can hear a BIG difference. And once I get to crank the sound up, the base driver on the 3677's should be interesting.

In all it might make the use of the BFO JBL Sub's redundant, which is a shame, I as I really want to get them involved.

I took a day out today to think about my cable runs for HDMI, Power, speakers and lighting. I think I've got it all squared away in my head so it works with the fabric and other stuff going on in the room.

What you planning on using the Subs for... Or just wiring them up and seeing what happens. If you're local your welcome to observe when they are up and running.
 
Do the bass drivers on your 3677's actually move much?

I was shocked when playing mine that they hardly move...they are working and go extremely loud and if left to it (subless) produce a bit of bass but the cones don't seem to move much. I'm only driving them off a NAD T778.

I'd be interested to see a short video of yours if they're different? I may look at adding a PA to mine if it does help. I also tried removing the foam bungs from mine whilst messing about but they seem to be stuck in so didn't want to pull any harder!
 

LittleNipper

Well-known Member
Sorry, meant the base drivers on those Subs. The base drivers on the 3677's don't seem to move at all - it's really quite odd. But they produce sound, so that's good. I'm sure if we pump enough power through them they will move.
 

stevie0

Active Member
To be honest I have no idea what to expect from these subs, but I thought why the hell not !!! But 12 - Wowza.
I seen them on eBay, and thought the same, worse case scenario for me is using the drivers in an infinite baffle, or putting them under the seats.
I used REW to see where I'd get the most even sound for them and then positioned relative to where my screen is going so no drivers are behind the screen.
I need to have a look at that too to see what I can expect in my planned room, nowhere near as good as your build but I’m hoping it will still sound decent.
I was going to mount in the wall on the supplied brackets, but as they are so darn heavy, I'm sliding them in on top of some TecSound, which is pretty grippy stuff and should resist vibrations going through to the main carcass of the baffle wall. If it doesn't and I need too, well I can refit them and attach that way.
I’m still undecided how to mount mine too, I’m quite far away from that point as it stands, I need to get rid of a snooker table before I can start, which is now annoying me 😂
I'm certainly looking forward to listening to the 3677's in it. I've compared them to my MK Sound speakers and prefer the directness of the compression drivers. I can hear a BIG difference. And once I get to crank the sound up, the base driver on the 3677's should be interesting.

In all it might make the use of the BFO JBL Sub's redundant, which is a shame, I as I really want to get them involved.

I took a day out today to think about my cable runs for HDMI, Power, speakers and lighting. I think I've got it all squared away in my head so it works with the fabric and other stuff going on in the room.
👍🏻
What you planning on using the Subs for... Or just wiring them up and seeing what happens. If you're local your welcome to observe when they are up and running.
In a word - I have no idea, I read about this double array positioning which interested me, so possibly 4 up fromt, 4 behind and 2 either side with phasing, I’m a real novice so have lots to read up on, and it seems now amps to purchase!

I’m in Sunderland so it’s a long way to come, thanks for the offer though 👍🏻
 
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stevie0

Active Member

bigbucks

Well-known Member
Personally i rate these subs but their not without any caveats. Amplification is something to think about with these as their 1 ohm drivers and bear in mind when you going down to low hz that impedence will drop too. Their foot print makes them very good for a very nearfield sub but be careful with them as they can quite easily worsen the response of your in room lfe though. Unfortunately their not just a plug and play bit of kit, its taken me probably about 4 mths to fully get to grips with their capabilities but for me they do what i d intended for them to do. My advice would be to install 2 of them then check your frequency response and phase alignment with rew software to learn how they affect everything else, once you ve learnt then i d install the next 2 and again measure the room, i found when i used 6 at the rear there was no advantage compared to using 5 of them and the response actually worsened so just bear that in mind.
 

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