I need some help in OB positioning

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Bumpy

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I need some help in OB positioning
« on: 6 Jun 2020, 08:45 am »
I have moved to a dedicated listening room in my house, but the downside is its a very difficult shape to work with - quite narrow for most of it and a vaulted ceiling

I have yet to find a position where my open baffles (4ft tall by 18" wide) sing like they used to.

In the attached diagram you can see the many positions I have tried. At each stage I angled the speakers and sat various distances away, but I'm missing the OB magic/communication.




Here is a picture of the OBs in their previous room




Any suggestions very gratefully received.

Thanks


FullRangeMan

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Re: I need some help in OB positioning
« Reply #1 on: 6 Jun 2020, 08:49 am »
I would prefer position B with no or little toe-in.
Also in front of the window is a position to try.
due the wide 5.6m wall.

Bumpy

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Re: I need some help in OB positioning
« Reply #2 on: 6 Jun 2020, 09:10 am »
Thanks FRM

I've not tried in front of the window. Maybe a bit stuck for seating distance with the OBs 1m from the wall, but I do like to listen near field:)

Position B was one of the many I had tried without success.

matevana

Re: I need some help in OB positioning
« Reply #3 on: 6 Jun 2020, 03:40 pm »
Also consider the position of the listening chair in the previous room.  Was there a wall directly behind the chair or was it out in the middle of the room? Can you approximate its position in the new room?

Bumpy

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Re: I need some help in OB positioning
« Reply #4 on: 6 Jun 2020, 04:07 pm »
Also consider the position of the listening chair in the previous room.  Was there a wall directly behind the chair or was it out in the middle of the room? Can you approximate its position in the new room?

In the old room I normally ran with the speakers about 1.5 metres apart and the listening seat 1.5 metres from each speaker. This was chosen to receive direct sound before rear or side reflections. My seat was against the wall, but I was hoping to get away from that.

In the new room the speakers were still 1.5 metres apart in all configurations I tried but the side walls were now much closer. I tried my seat in all positions.

The recommendation by FRM to place under the window is showing great promise. This almost replicates the previous room, but my head is now once again next to the wall. At low volumes it’s fine, but at moderate volumes it a little bit claustrophobic. I think some sound treatment on that wall may be very beneficial, but do I use absorbers or diffusers?


diyman

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Re: I need some help in OB positioning
« Reply #5 on: 6 Jun 2020, 10:43 pm »
Also you might try a heavily upholstered chair with a very high back that comes up well above your head.  That could provide as much, or even more, sound deadening as a panel on the wall behind you.

Bumpy

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Re: I need some help in OB positioning
« Reply #6 on: 7 Jun 2020, 07:15 am »
Also you might try a heavily upholstered chair with a very high back that comes up well above your head.  That could provide as much, or even more, sound deadening as a panel on the wall behind you.

So are you saying an adsorber rather than diffuser is needed behind the head?

Rocket_Ronny

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Re: I need some help in OB positioning
« Reply #7 on: 7 Jun 2020, 02:59 pm »
Keep trying. I don’t know what ob sound you are missing. I would try position D but moved more towards C. If you chair is backed up to a wall try a pillow behind your head to stop reflections. Do your speakers disappear, they should in those positions. I would also try going as wide as possible. Something like this.

https://www.youtube.com/watch?v=BqzB6JkDBA8

Rocket Ronny

Bumpy

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Re: I need some help in OB positioning
« Reply #8 on: 7 Jun 2020, 10:23 pm »
Keep trying. I don’t know what ob sound you are missing. I would try position D but moved more towards C. If you chair is backed up to a wall try a pillow behind your head to stop reflections. Do your speakers disappear, they should in those positions. I would also try going as wide as possible. Something like this.

https://www.youtube.com/watch?v=BqzB6JkDBA8

Rocket Ronny

I don't think I am missing anything now with the speakers positioned in front of the window as suggested by FRM. The remaining problem is that at mid to high volumes there is too much 'signal energy' entering my head. There are no close sidewalls now, so it is partly coming from wall reflections behind the speakers (a fact of life with OBs) and partly from wall reflections just 12" behind my head. This is a simple plasterboard on timber frame wall and quite resonant if tapped. I think therefore most of the problem is likely to be the latter. This surplus of energy entering my head is not enough to cause a headache but is enough to somewhat spoil my enjoyment.

The pillow trick behind my head (absorber) helps but would it be better with diffusers which I don't have here to try?


Thanks for helping.

Bumpy

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Re: I need some help in OB positioning
« Reply #9 on: 7 Jun 2020, 10:33 pm »

https://www.youtube.com/watch?v=BqzB6JkDBA8

Rocket Ronny

I had a look at this RR and it seems to work for him, but he has a BIG room allowing speakers 8ft in front of the facing wall, 9 ft apart and a fare distance from the listener. I don't have that luxury of room size.
Also he seems to use EQ to reduce what are probably room effects. It may just be me, but I dont like that method at all.
Cheers Chris

Bumpy

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Re: I need some help in OB positioning
« Reply #10 on: 10 Jun 2020, 08:48 am »
I'm getting somewhere now. First let me say I enjoy listening near field and am very grateful for your help.

The plan sets out my best speaker position and position of baffles. The reflections from the wall behind my head are killed with absorber panels.

I have now bought a pair of QRD diffuser panels, but never having worked with these things I would like a bit of guidance where to start positioning them with OBs. They are sturdy enough that, if I make some feet, they can be free standing like screens if this helps.







Rocket_Ronny

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Re: I need some help in OB positioning
« Reply #11 on: 10 Jun 2020, 12:46 pm »
Quote
he seems to use EQ to reduce what are probably room effects.

The e.q. is not for room effects, but to flatten the speaker output. I don’t use eq to fox room effects.,

Rocket Ronny

Bumpy

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Re: I need some help in OB positioning
« Reply #12 on: 10 Jun 2020, 02:03 pm »
Sorry RR I didn't realise that was your video. Had I known I would have clarified things before posing.  :duh:

Bumpy

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Re: I need some help in OB positioning
« Reply #13 on: 10 Jun 2020, 03:04 pm »
Sorry RR I didn't realise that was your video. Had I known I would have clarified things before posting.  :duh:

Bumpy

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Re: I need some help in OB positioning
« Reply #14 on: 14 Jun 2020, 11:57 am »
The diffusers in position C have the biggest benefit. I guess this could have been predicted as its where the rear dipole hits the wall.

Bumpy

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Re: I need some help in OB positioning
« Reply #15 on: 28 Jul 2020, 01:48 pm »
Finally making some sense of speaker placement in this new room. It turns out that position B is optimum



Attached, hopefully, is a picture of the latest set up.  It has been challenging but I have learnt a lot about room treatment for open baffles in a relatively small and very awkward room. 1. Absorbers up high to kill the clap echo of a high ceiling. 2. Diffusers not absorbers behind the speakers to preserve the life of the rear sound wave. 3. Modest absorption on the side walls at primary reflection points, although this is not a strong need with an OBs. 4. Speakers toed in the face the listener. This set up preserves sound stage, imaging and above all SQ. Any remaining minor tweaking can take place over time.






bladesmith

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Re: I need some help in OB positioning
« Reply #16 on: 30 Jul 2020, 02:16 am »
What happens when you crack a window open..?
😆😆😆

Mine always sound better,  with a window cracked..
(Just saying..)

mijostyn

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Re: I need some help in OB positioning
« Reply #17 on: 30 Jul 2020, 11:42 am »
Hi Bumpy,
Either B or A will do. I will assume your drivers are all open to the back except the woofer. This makes them dipoles with conical dispersion in a figure 8 pattern. This means that there is essentially very little output directly to the sides, up or down in the plane of the speaker.
The major difference between A and B is going to be in the bass and where you put your absorption panels. As you move the woofers closer to the wall the first major node will be at a higher frequency. At 5 feet away from the wall the first major node will be at 100 Hz at the position of the speaker. What you actually hear will depend on where you put your listening position. Put your listening position where the bass sounds best to you. Putting sound absorption materials in the plane of the speaker is a waste as not much is happening in this plane.
Find your first reflection points on the ceiling, front and side walls using the mirror method. While you are sitting in the listening position have a friend move a mirror across and against the front and side walls. When you see the reflection of the speaker in the mirror mark the wall there. These points are where you place sound absorption devices at the level of your ears seated at the listening position. Parts Express has very inexpensive acoustic tiles which you can use to play around. You do the same on the ceiling but with more difficulty so be careful. Using sound absorption correctly should solidify your image in space and it can make a major improvement in this area. If a first reflection point just happens to be in the plane of the speaker you do not need to put anything there as there is little acoustic output directly from the speaker, just reflected sound.
Now about bass. Woofers always work and sound better against walls or in corners. If you separate the woofer from the rest of the speaker you create phase and time anomalies. The sound from the woofer reaches your ears at a different time and phase than the rest of the speaker which IMHO sounds worse than just keeping the woofer with the rest of the speaker and dealing with the bass by moving the listening position (which will shift all your acoustic treatment!) The ideal solution is to use separate subwoofers with digital bass management that allows you to align your speakers and subwoofers in phase and time. The Anthem STR and Trinnov Amethyst are two units that will allow you to do this. Less expensive units will be available in time.
Good luck and have fun.