Planar Speaker Asylum

Welcome! Need support, you got it. Or share your ideas and experiences.

Return to Planar Speaker Asylum

Planar Speaker Asylum

RE: Diffusison

84.132.52.212

In Reply to: RE: Diffusison posted by josh358 on September 28, 2016 at 16:43:37

Fellow Inmates

Proper room treatment should be on every audiophiles agenda. Big time.
The right balance between diffusion and damping of sound waves is especially important for our beloved dipole / planar technology, and I must admit, I have previously not given it so much attention that it deserves.

I have learned some good advice from different sources and people, but would put following link to your hearts & imagination :

http://www.hedbackdesignedacoustics.com/files/QuickSiteImages/AMS_for_Stereo_List._Rms.pdf

The cheap & easy bending of the translucent fibre glass diffusors, has enabled me to adjust angles and distances to the reflecting back wall and (sorry to say) adding another level of complexity in acoustical setup.
As the reflectors don�t suck up any excess lower frequencies, but rather disperse higher frequencies and break-up flatter echoes in midrange, there are further treatments to be made.

Tubed bass traps and a row of polystyrene bars across the ceiling, have made incredible progress in managing decay across different frequencies.

Not particular WAF friendly, but at least price sensitive.

regards Leif

cMP2 Computer // Prism Sound Lyra // Spectron Musician III // Analysis Audio Omega

Follow Ups:

RE: Diffusison - josh358 07:09:22 10/02/16 (10)
What do the polystyrene bars do?

I'm also thinking at this point of making a cylindrical diffuser to solve the window problem -- I have to put a diffuser right here:

Bending the acrylic would be a bit of a pain, though -- I'd need a form, felt, a heat gun, and a lot of luck! If I made the form with masonite I could make a catenary shape, which is supposedly better than a hemisphere in this application.

Some possible negatives: lobing between the two symmetrical diffusers, and the fact that hemispherical diffusers don't randomize phase (although their diffusion pattern is apparently much cleaner than that of a QRD or PRD).

What I really need is a wrecking ball so I can build a bigger room. :-)
- RE: Diffusison - play-mate 10:02:25 10/02/16 (9)
  Josh
  
  Let�s face it - big planars in small rooms need HUGE efforts with damping & diffusion to reveal their sound potential. It is really better to size the planar to the room than opposite way around, but since we both have the circumstances, I will urge you to take 2 important steps :
  
  First you need to get some massive absorbers that can catch the lower frequencies, cause they mock up big time. The simplest ( cheapest) way is to buy four packets of rock wool panels (at least 15 cubic feet) and cover them up in some cloth. This is much more effective dealing with low frequencies, than plastering lots of wall panels all over, because that will just kill the mid-high frequencies and leaving you an acoustical dead space.
  Surely you should also get some curtains and a rug; - some plants and a book shelf would not hurt either.
  
  Secondly some diffusion. Small spaces are easily problematic with flatter echoes & standing waves , which diffusors get rid of. A diffusor behind your listening position is also advisable.
  
  While these measures are well known, I can only testify that it make a huge difference on planars.
  
  The polystyrene bars are scattering sound waves near ceiling. Like diffusors they make the room seem acoustically larger and more spacious than it is.
  
  I think it is better to trial/error some inexpensive efforts, than spending a fortune on the wrong things.
  
  Planars do need reflections, so don�t kill the room with too much damping.
  
  Kind regards
  
  cMP2 Computer // Prism Sound Lyra // Spectron Musician III // Analysis Audio Omega
  - RE: Diffusison - josh358 19:14:55 10/02/16 (8)
    Hey Play-Mate,
    I'm still experimenting with speaker location so for now the room is basically bare. I expect I'll have a rug and whatever else I need to bring the reverb time down. Dust/allergies are an issue for me so I have to find stuff that's washable.
    There's certainly room for some tube traps behind the woofers. Bass changes so radically with speaker position that I'm not sure what I'll need or where. Fortunately, the bass is surprisingly smooth given that the room is nearly square and it was awful when I had the speakers on the wall facing the fireplace. I think this is because the wall I'm against opens into a hall which breaks up the z-axis modes:
    
    QRD diffusers behind the speakers definitely improved imaging when I tried them. I can't put a diffuser behind my head though since as you can see above I'm basically sitting within a foot or so of the wall. (Maybe a shallow cylindrical, which could also serve as a bass trap with some fiberglass behind it). I've seen absorption recommended for this situation and may give it a try.
    The room features are apparently irregular enough to avoid obvious slap and flutter echo, even with only minimal furniture in it. The speakers snap into focus when I put the null at the first reflection points on the sidewalls, but to do that, I'll need to use the MiniDSP which I can't hook up until I lay in some more amps.
    I'm fairly constrained in where I can put diffusers, sitting against the wall like that and with the hearth on the right and two windows and a column on my left. So still not sure how I'm going to work that out.
    What amazes me though is how *good* things sound now without any treatment. A one note midbass resonance probably caused by the cavity to the left of the fireplace mantle goes away when the woofers are pulled forward as they are now, with the speakers equidistant as an experiment and a 6" gap between the mid-tweet and woofer panels (gap not shown in this shot -- also distances and angles are distorted by the panorama):
    
    This arrangement is an experiment to get a sonic baseline, as a matter of practicality I'll go back to some variant of the split config. But the speakers are sounding great like this -- plenty of depth (they're at 5' off the front wall, would be even better at 6') and lateral spread -- the jaw-dropping "magic carpet" planar line source imaging that I love. Also, the IVA's are nicely balanced despite the lack of absorbent material -- a bit tipped up in the highs but not harsh -- whereas the MMG's sounded unpleasantly hot in this room when it was bare.
    The big challenge for me right now is to get them sounding as good in split configuration as they do in line. Here, they're at the standard stereo spread but it's hard to do that with split config, so the image seems constrained laterally. And a radiator is in the way on the left, and the mantle on the right:
    
    Anyway, as you can see, I have a lot of experimenting to do before I know where they'll be sitting -- I've only had them against this wall for a week or so. Once I know where they'll be living I'll start measuring and work on acoustic treatment. It may be that he only way to get them to image well will be to separate the midbass and low bass panels and move the low bass panels elsewhere, e.g., out in the hall. Which is why I'm intrigued by BDP's dipole woofer comparison experiment, in a room like thi sit really would be more practical to use just the M-T and midbass panels and use dipole woofers for the deep bass. But the bass on these speakers is so stunningly realistic that it's quite a challenge to equal it!
    I've still never heard midbass to equal the Tympanis, that combination of planar bass clarity and near-dynamic slam. It's one of the things I love about them.
    
    Edits: 10/02/16
    - RE: Re framing - Satie 09:54:01 10/03/16 (5)
      There is nearly a foot's worth of MDF you can remove from each speaker by going to a hardwood frame. Also benefit from putting the mid and ribbon closer. Perhaps that is the way to fit the speakers into the room in the equidistant setup. Despite many trials on other setups that is pretty much the go-to for all performance criteria even when the crossover is not quite friendly to it. As Vandersteen and Theil point out there is something fundamentally right about physically time aligned designs that does not quite happen without it.
      - RE: Re framing - pictureguy 11:26:40 10/06/16 (3)
        
        In Reply to: RE: Re framing posted by Satie on October 03, 2016 at 09:54:01
        
        Isn't frame width related to front/back cancelation frequency?
        Too much is never enough
        
        RE: Re framing - Satie 14:26:37 10/06/16 (2)
        
        In Reply to: RE: Re framing posted by pictureguy on October 06, 2016 at 11:26:40
        
        Yes, but less important when you are using wall loading as Josh is doing as dipole cancellation is restricted on one side. .
        
        RE: Re framing - pictureguy 15:47:20 10/06/16 (1)
        
        In Reply to: RE: Re framing posted by Satie on October 06, 2016 at 14:26:37
        
        I'm just establishing the principle. And Yes, with the panel using wall loading, that side is pretty much 'out of play'.
        The reason I ask is that I've seen Panels with 'truncated' frames (Apogee?) which I suspect varies the cancelation frequency. Advantage? Disadvantage?
        I would design such frames for my 1.6s, if I ever work up the energy to start!
        Too much is never enough
        
        RE: Re framing - Satie 18:54:53 10/06/16 (0)
        
        In Reply to: RE: Re framing posted by pictureguy on October 06, 2016 at 15:47:20
        
        The trapezoid shaped frame on the Apogee is supposed to spread the baffle loading over a broader range of frequencies rather than have the one freq below which it just falls off.. Other issues are at play but I don't remember what they were. That should complement the room's bass loading and provide a more uniform bass FR - it is sort of a substitute for Magnepan's resonance freq tuning with the buttons. but operates at a different freq range to provide a lower bass emphasis vs more even response on through the midbass on maggies.
        
        I don't expect it would contribute to a maggie reframing project. .
      - RE: Re framing - josh358 10:02:43 10/03/16 (0)
        
        In Reply to: RE: Re framing posted by Satie on October 03, 2016 at 09:54:01
        
        The equidistant setup certainly works sonically but it destroys the room, almost bisects it and blocks a window. I'm going to try it further back -- I'd tried it at 3' which as you might expect was terrible (easy to do because that's where the woofers were at the time) but not at 4' or 6', only at 5', and not with diffusion. I'm thinking that 3' or 4' might work with diffusion and that becomes practical.
        
        New wood NT panels would be nice and it would be great to put the mids and tweeters closer together. (BTW, anyone know what the trim strip between the mid and tweeter in the 3.x and 20.x does? Is it there for structural reasons?) However, another big project I don't have time for, busy today installing the fireplace and I haven't even fixed the delam on the woofers.
        
        Whatever I do, it will ultimately be time aligned with the MiniDSP, I don't see any way of getting this room to work without that.
    - RE: Diffusison - play-mate 00:15:45 10/03/16 (1)
      Dear josh358
      
      I guess, this is a dedicated listening room and not your family living space. That should give you a little freedom to setup less conventional.
      As the room is small, I think it would be wise to consider as much symmetry as you can and therefore using the fireplace as the back wall of the setup. That will, of course, interrupt the access to the room, but hey - it�s not easy to enter a Ferrari either.
      As bass nodes are difficult to localise, traps are not critical to position. Maybe you could build a discrete triangular, wall mounted bass trap in the hallway.
      An even sonic decay of a room, is the key to clarity in all frequencies.
      
      Just my 5 cents.
      
      L.
      
      cMP2 Computer // Prism Sound Lyra // Spectron Musician III // Analysis Audio Omega
      - RE: Diffusison - josh358 04:31:53 10/03/16 (0)
        
        In Reply to: RE: Diffusison posted by play-mate on October 03, 2016 at 00:15:45
        
        My original plan was to have the speakers on either side of the fireplace. It actually works out very nicely from a room organization perspective -- as you say, it's a dedicated room so I can do with it what I want but I still have to hang out there and want to do some work there so I can listen to the big speakers so I do want to make it functional.
        
        Unfortunately, when I tried this arrangement with the MMG's it sounded horrible. They just wouldn't image properly with the mantle behind them, no matter what I did. Everything sounded like it was coming from the fireplace. In the end, I figured out that the only thing I could do would be to put bookshelves with doors on either side of the mantle to flush out the wall, and that would mean moving the closet door to the hall -- major demolition in a house with lead paint, of which I've had my fill. Also, as I said, the bass doesn't sound good when the speakers are orientated that way in the room. Very lump in he midbass and no deep bass at all. And it's harder to accommodate the video projector as well.
        
        As you say, I want to aim for an even decay across all frequencies. But I don't yet know what high frequency Rt time I'll have when the furnishings are in place or what I'll aim for so I think I'll wait for the measurements -- my feeling was go for the higher frequency treatment first and then add bass trapping to match. (Bass trapping may also not just be a matter of broadband absorption depending on where the woofers end up living, the right hand woofer develops a one-note midbass boom if it's located in the cavity formed by the mantle and the front wall.)
        
        But right now I'm working on imaging. I'm really very constrained by that! Given the limitations of the room (radiator, mantle, etc.) I don't have much leeway in placement and I can tune EQ, Rt, and diffusion more easily than I can tune the imaging.

Post a Followup:

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.

This post is made possible by the generous support of people like you and our sponsors: