John Sayers' Recording Studio Design Forum

Haha. At least my homemade Genelec mounts look a bit stronger than theirs

On the question of my ...un-infinite baffle, I was thinking of another option - to just have cloth panels at the front, with plenty of absorption behind, and let the Genelecs do their thing...

Still, I'll try to tilt part of the front panels in Sketchup and post a picture of that. Many thanks for the suggestions and feedback so far!
Geoff

Hey Geoff.

But if you did that, then it would be a "zero baffle", not an "infinite baffle"!

In other words, it would not be a baffle at all. The idea behind an infinite baffle is to force the speaker to radiate into half-space, by preventing low frequency waves from "wrapping around" behind the speaker where they muddy up your bass response. By "low frequency" I mean any frequency whose wavelength is larger than the dimensions of the speaker's own baffle (front panel). In the case of the Genelecs, they aren't very large to start with, so a substantial part of your lows and mids can potentially wrap around behind and mess up your acoustics, and screw with your stereo imaging. Sure, Genelecs are specifically designed to minimize those effects (part of the concept of the rounded shape, IIRC), but it is still there. Since the company itself makes and promotes its flush mount kits, obviously they think that correct flush mounting is important to get the best performance out of their monitors. And "correct flush mounting" implies a large, flat, stiff, massive surface surrounding the speaker as an extension of the speaker's own baffle. Not a soft fluffy surface!

Surrounding the speaker with cloth and soft fluffy stuff is the exact opposite of what a baffle is intended to do. That will absorb some small fraction of the waves that wrap around behind, but selectively at the wrong frequencies. Absorption works best at high frequencies, where waves don't "wrap" very well anyway (since they are more directional). In order for it to work at low frequencies, it needs to be very thick. Even then, it is still the opposite of an infinite baffle, and does not work like one at all. The baffle forces all of the "wrap around" sound back into the room (which tightens up your low end and improves imaging), whereas absorption does not do that: it merely absorbs different frequencies by different amounts.

Don't get me wrong: just putting your speakers on massive decoupled stands with absorption on the walls behind them certainly is an option, and many people do that. But that's not the same as infinite baffle mounting. You'd be trying to combine the two totally different concepts into one by doing what you described above. I have no idea how it would work, acoustically, but I do know that it wouldn't be a soffit mount, and it wouldn't be an infinite baffle.

My suggestion (and take that for whatever you think it is worth! ) would be to stick with the concept of the flush mount infinite baffle, since you already have it mostly done, and just try to angle those panels as much as you can to get them more perpendicular to the acoustic axis. As someone else mentioned, you'd probably need to slide the speakers forwards a bit (towards the room), in order to maintain the correct depth of the speaker sticking out of the baffle, but that shouldn't be too hard to do (famous last words!).

Just my $ 0.02.

- Stuart -

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I want this studio to amaze people. "That'll do" doesn't amaze people.

Yes Stuart, that last idea was to simply abandon the infinite baffle concept and just have them as if they were sitting on stands at the front of the room with absorption behind; with cloth panel surrounds to keep that "look".

But you're right, I'm most of the way there, and getting kinda used to cutting plywood in all sorts of whacky shapes so I'll give that a go (though, in Sketchup first ).
Geoff

So I'm thinking something like this...
Not ideal, but more "flush" now.
Doesn't obstruct the door to the left of the monitors, or the window to the right.
Leaves the "ports" above the front finish as they are.

(The cross on the front of the monitors represents the acoustic axis as specified by Genelec.)

Let me know your thoughts, guys! Many thanks,
Geoff

that might work, or atleast works better than previous plan.
What's behind your speaker units?

Mostly the inside of the inside out walls. Some of the earlier pics will give a better idea. There's a "boxed out" pillar and beam, and some flexiduct, at the right; and I've attempted to match that surface area behind the left monitor. I plan to add more absorption behind the monitors, too.

For now, trying to get something meaningful out of Room EQ Wizard on my Mac laptop...

So, still on the baffle issue...
I've done some A/B tests, firstly using my ears (the best test equipment I have!), and a few selected tracks from my favourite CD's; with and without the timber surround panels, except for the centre one, which I left in place. There is added rockwool behind the monitors for both.

"With" timber surrounds as in the photo below.
"Without" timber surrounds as in the drawing below...

I also sent a mate some A/B recordings taken from the mix position, from a single Rode NT5, Sound Devices Pre, and Powerbook G4 line in. He wasn't told which was "with" or "without".

Note - this refers to my own particular (peculiar?) monitor set up only! And slats are not yet added to side walls.

With the timber surrounds, the recordings were louder overall; all good;
Without, low end was attenuated, but highs seemed to sit better in the mix - were more "crisp", my mate says. I felt there was more "air" in cymbals and reverbs; and I suspect the stereo image was wider, though a little weaker at the centre... not sure.
My mate says the lows were "punchier". I felt they were slightly more "boomy" but that seemed to add to the mix...

Then using a Radioshack analogue SPL meter at the mix position, and a test tone CD, I plotted a graph for each situation up to 300Hz (calibrated to 70dB using pink noise). This was very tedious, but RoomEQWizard wasn't working for me... btw have earplugs handy if you're trying this at home!!!

See the graph below. The blue line is with the timber baffle; green without.
If there's anyone here who's maybe strayed from the Acoustics forum, your thoughts are appreciated!

At the end of the day, I'm thinking to put cloth panels around the monitors...

Some questions about slat absorbers:
Will slats on the side walls boost my centre phantom image?
What frequencies should I aim to absorb?

Many thanks!
Geoff

I see that you decided to NOT angle the soffit panels to match the tilt of the speakers? Any reason for that? I still can't see that panel working well as an infinite baffle if it isn't in the same plane as the speaker. I'm wondering if that might have something to do with the deep dip at 68 Hz.

Those dips at 100 and 200 Hz are room modes, I guess? That would make sense, since adding the soffit moves them to a slightly higher frequency.

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Too much work for too little gain. What if I wasn't happy with the results of that?
Anyway, I've gone for cloth panels, based largely on what my ears tell me. Not real sure what those numbers mean, sorry!

Slats are up, too. Things are sounding even better! Much more focused towards the centre, I think. I'll run a pink noise test to see if I get a 3dB boost with both monitors on (I read somewhere)... though, there's plenty of building to do, too

More pics to come!

Geoff

Hello again,
Well, it's been a couple of months - must be time for another update!

So, lately...

*Architraves around doors and windows
*Filling, sanding, staining, painting - and still some more coats to go...
*Built, covered, installed most of the cloth frames (more cloth on order ).
*Built bench and shelves in the entry area - ready for a bar fridge and microwave.
(was careful not to make a hard connection to the wall of the main room...)
*Built a couple of 2 unit rack sleeves to sit on my desk, and other "odd jobs"

Here are some pics (from my phone, sorry!)
Getting closer! More pics to follow as I reach those milestones, like "finish painting" and "pick up tools and rubbish"
Geoff

Hi JSRSDF!
Haven't posted an update in awhile, though I still stop by regularly - the Construction Forum, at least, and the Wombat Hole.

The studio is pretty much done, gear is moved in, furniture etc.

Now the hard part - learning to use all this stuff properly! So glad to be finished #%$# building!

As I said before, the room sounds fantastic. I think it's more on the lively side (than dead), which I like - without having flutter or anything nasty.

Isolation-wise, a busy 4 lane city street just metres away is faintly audible when there is no music playing. Some LF is noticable, especially if a bus stops outside. The neighbouring office doesn't hear me, though I get considerable noise through the connected slab if/when they drop something heavy. Overall, I'm happy with the amount of isolation achieved - really feels like I can shut the world out - in a nice way.

But - I need air! Ducting and vents were installed during the build - just waiting on my fans, due this week... So I haven't been able to close all the doors for long periods before it gets very uncomfortable!

ok pictures: various views. I built the desk from layered plywood. The two cabinets below [one built to house a Mac Pro, which I now can't afford!], and small rack sleeves on top, are movable. I built-on the keyboard drawer last.

More updates to come - maybe some pics of the booth after I move my tools out of there!

Thanks for reading,
Geoff

Wow!
So you basicly went with hidden speakers stands rather than soffits?
It won't help the bass but it's up to your ears.
lil

_________________
inkspotproductions
www.bantamstudio.info

I was thinking the same thing! Although it's not as bad as having those straight soffits with tilted speakers, as per the earlier design, it could have been so much better with proper soffits. I'd be interested in seeing how that response curve has changed, now that the room is finished.

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I want this studio to amaze people. "That'll do" doesn't amaze people.

me too - I designed it with soffits.

Thanks for your comments guys and gals,

To go over what was mentioned previously in this thread, though it was some months ago:
Yes, they are cloth surrounds on thin plywood frames.

Due to various factors, starting with me trying to dig out the slab foundations with a jackhammer and spade, rather than a hiring a mini-backhoe for a day (That can go on my "what would you have done differently" list)... thusly having a higher slab than planned (and John recommended isolating the slab too, which I wish I'd done now)... I raised and tilted the monitors to avoid the midpoint between floor and ceiling.

To quote myself, from a previous post:

I then chose monitors that I think didn't go well with my flush mounts. Fantastic monitors btw! but I noticed they were actually sounding better when I had the front panels off! And... as written about in the older posts, did measurements "with and without" and did a "blind test" with muso mates, and decided on cloth surrounds. To my ears the bass sat better in the mix, improving "air-iness" - like it was "pushing" the whole mix more from behind - that's probably B.S. but it's what I "pictured"...

Anyway, again, I'm very happy with the way they (and the room) sound - to me they are transparent, uncoloured, like there are no monitors - just "the mix" in space .

I'll also be interested to do another response curve. I suspect it'll be close to the green line on the graph above. I want to get/post some readings on the amount of isolation, too.

Geoff