How are my bass traps looking and what shall I fill them with?

[James Perrett]

The thing about acoustics is that the right materials don't have to be that expensive but they aren't available from DIY stores. You need to go to proper insulation suppliers. If you can't find RW3 then Rocksil RS60 is almost identical.

[Drew Stephenson]

Knauf Earthwool is the same stuff too and also comes in a 60kg variant.

[jellyjim]

My vote is yes on all three.

It’s mostly all your fault, Hugh. Putting these cotton-picking highfalutin ideas of audio excellence in our pretty little heads. We were all happily going about our business stumbling around making terrible recordings until SOS showed up!

[jellyjim]

The thing about acoustics is that the right materials don't have to be that expensive but they aren't available from DIY stores. You need to go to proper insulation suppliers. If you can't find RW3 then Rocksil RS60 is almost identical.

Ooh, that seems easier to find in smaller quantities. Though the delivery cost is high. Presumably because it’s trade or they expect high volumes. One place I found allows free collection at various locations and one is only 20 miles from me.

[Sam Spoons]

RW3 is a pain to get hold of these days. You usually have to order in bulk and the delivery cost is high. I got RWA45 from Amazon and it does the job, although it is less rigid.

Agreed, though I did find RW3 on bit the occasions I needed to buy it* so it's well worth persevering.

* The first time a mile up the road, the second involved a 50 mile round trip to collect but I'm retired and the fuel cost a lot less than the carriage would have done for a couple of packs.

[Drew Stephenson]

Have you tried Jewson? They happily ordered half a pallet in for me.

[jellyjim]

Righto you wizards, I really do appreciate your time and advice.

Here's my initial plan. It's just a start, to see what I can do with the basics and experiment with my room layout. I've got a measurement mic and I've familiarised myself with REW. Not mentioned in this thread but my monitors are Genelec 8330a with SAM room correction so there's that to play with too. It may well be a combination of my DIY efforts and some commercial products by the time all is said and done.

Fill the existing not-bass traps with RW3 (using this generically here, RW3 meaning a mineral wool with 60kg/m3 density) and use those behind my monitors.

2 x broadband absorbers for first reflection points. 1200mm x 600mm. 100mm RW3. 50mm air gap.

4 x triangular corner bass traps. Height 600mm. The legs of the triangular profile being 400mm which I think makes the hypotenuse about 585mm. Fronted with RW3 slabs and back-filled with the remaining bog standard Rockwool my neighbour gave me.

The thinking of making 4 at 600mm height rather than 2 x 1200mm height is it allows me to experiment. In all likelihood all I can treat for now is two corners so I may well end up stacking a pair in each front corner.

I'm using Camira's Cara acoustic fabric and either open wooden frames or MDF walls with 50% material removed, if I feel I need it for structural integrity. I haven't played with any RW3 yet so I'm not familiar with its rigidity. 100mm slabs are quite hard to find in small quantities so I might need to layer 50mm slabs.

Woddayareckon for a starter for ten?

[Hugh Robjohns]

All sounds good to me.

RW3 is much like Weetabix (but not brittle and much less crumbly). It is dense and firm and fully self supporting. You can cut it with a serrated bread knife very easily.

It doesn't shed much, but I'd do any cutting outside if you can, and wear a disposable coverall, gloves and dust mask because the fibres are irritants. A light spray with diluted PVA glue will minimise fibre shed while handling without affecting the acoustic properties.

[jellyjim]

All sounds good to me.

Great, thanks Hugh

RW3 is much like Weetabix (but not brittle and much less crumbly).

I'll get some milk!

the fibres are irritants.

Yup got that memo

[Sam Spoons]

Yup, agree, but keep the construction simple, the RW3 is rigid enough not to need any extra support* so why make work for yourself.

* You may need to give it a little help in the corner traps to stop the back fill from pushing it out, mine were stacked triangles of RW3 so I don't know for sure.

[jellyjim]

Yup, agree, but keep the construction simple, the RW3 is rigid enough not to need any extra support* so why make work for yourself.

Just nice neat corners and edges, I suppose. Where the fabric wraps around the mineral wall. For the actual 'panels' at least. Yes I can imagine the bass traps needing more support. Yes planning to use stacked triangles.

[Sam Spoons]

The bass traps will work fine without anything in front but the Cara fabric, just put a dividing panel, a horizontal triangle of MDF or ply halfway up if you go for 1200mm high traps, to support the weight of the RW3. A stack of triangles* of RW3 up to a metre high is pretty stable. Mine used all 50mm slabs so your 100mm slabs should be plenty rigid enough.

* I cut the 1200 x 600 batts in half then the resulting 600 x 600 pieces diagonally both ways (think sesame toast ) leaving me with a long dimension of 600mm and the short sides 424mm.

[jellyjim]

Plot twist!

A friend is going traveling for a few months and has offered to loan me their Genelec 8331a's. I was reading the SOS review of the 8331/8341 and was curious and surprised to find the following:

the ultra-nearfield can be hugely advantageous when the listening room’s acoustics are sub-optimal. Nearfield listening inherently reduces the significance of room reflections, and the closer you can get to the monitors, the less the room’s acoustics matter!

The benefit of Genelec’s point-source designs makes it possible to have a full frequency range and an almost total exclusion of the room sound, with headphone-like clarity and resolution but much better stereo imaging.

In a good room, the GLM equalisation feature adds a welcome uniformity to the on-axis frequency response, while in a bad room, the ability to work very close allows most of the room effects to be beneficially negated.

https://www.soundonsound.com/reviews/genelec-ones

My monitors are 100cm apart and I typically sit 1m away, less if I slouch or am peering at the screen. Does this constitute ultranearfield? How many of my room problems will be negated? What can I expect? I have moved the clutter and another recent REW test (with my 8330a) showed more symmetry but still the problematic 100hz null, significantly reduced mind you.

[Hugh Robjohns]

I'd say within a metre counts as comfortably nearfield. Ultra-nearfield is probably within 50cm...

But the main problem with ultra-nearfield listening (and nearfield, to a degree) with conventional monitors is that there is an appreciable angle between tweeter and woofer, and so the sound isn't fully integrated across the spectrum by the time it reaches the ears. Clearly, the smaller the speaker the less of a problem this is, which is one reason why speakers with 5-inch bass drivers or smaller are recommended in this role. A smaller bass driver means the tweeter is closer to the centre of the bass driver, and thus gives better integration in the nearfield.

True concentric speakers like the 8331s overcomes the problem very well as all frequencies appear to come from the same point in space.... but there aren't many true concentric designs and most are relatively expensive. The Genelec Ones are impressive!

Obviously, the closer you are to the speaker, the greater the ratio of direct to reflected sound and so the less significant the room acoustics become...

...but that doesn't mean the physics has gone away. There will still be desk reflections and room modes to deal with. You just suffer less significant reflections from the walls, so the mirror point treatment becomes less critical. A strong room mode will still make the bass cancel out at some points in the room, no matter how close the listener and speaker!

Also, when working in the very nearfield, small physical movements left-right will greatly distort the stereo image balance compared to the same movements with a greater listening distance, which might become irritating if not problematic.

For reference, my own KH310s are about 1.5metres apart and I listen critically at the same distance, but a little closer when I'm fiddling with the computer by design because I generally find the exaggerated width helpful. The tweeter and midrange units are very close — about the same spacing as the KH80 in fact — so, although relatively large speakers, the driver layout means that they work very well in the nearfield.

[jellyjim]

I'd say within a metre counts as comfortably nearfield. Ultra-nearfield is probably within 50cm...

Interesting. I found your review fascinating, Hugh, and very well written. Potentially then, a design like The Ones could mitigate the need for some treatment - other than bass absorption where the physics is truly unavoidable.

[Hugh Robjohns]

Potentially then, a design like The Ones could mitigate the need for some treatment ....

Potentially, yes... but that would restrict your 'quality listening' space to just the area right in front of the speakers -- you couldn't get up and walk around the room and expect to hear much the same thing, for example, which you could if you had installed reasonable acoustic treatment.

[jellyjim]

which you could if you had installed reasonable acoustic treatment.

Exchanging emails with GIK Acoustics as I type!

[Hugh Robjohns]

[ajay_m]

Regarding the idea that nearfield/ultra-nearfield monitoring might overcome room issues.

I am but a layman and I have a completely untreated attic room as the listening environment but I did experiment with my Tannoy Gold 5s in a nearfield configuration (about 1m clear of the front wall and about 75cm away from my ears, with the distance to the rear wall being I guess another 2.5m from the front of the speakers and therefore just under 2m behind my listening position).

Being coaxial you would think they ought to be fairly ideal in this configuration.

However I found noticeable midrange tubbiness (around 160Hz) in the sound despite the rear wall being quite cluttered with bookcases full of stuff, and also a clothes rail with all my shirts hung on it).

So *maybe* you can negate room acoustics with nearfields but it didn't work for me. They sound much, much better on shelves against the front wall, making them about 2m from my listening position (with a total room depth approx 3.5m). I can quite clearly hear that if I then position myself against the rear wall there is a noticeable bass boost in that position relative to my actual normal listening position (this is just standard drywall in an attic conversion so nothing really solid behind most of the wall).

My low-tech approach to managing bass is to have a listen in both my normal listening position and at the rear wall. I then figure that if my mix sounds reasonable balanced and not too bass-heavy at the rear wall I'm probably close enough - heck, I'm just an amateur doing this for fun, I'm never gonna have a hit single!.

Anyway, just my ten cents worth - nearfield didn't really work for me at least with those monitors in my environment. Your mileage may vary.

[jellyjim]

Well now I'm really confused.

I got the results of my consultation from GIK and ... no corner traps whatsoever. Scratches head emoji.

Ceiling absorber. Bass traps behind monitors for SBIR. Bass traps and broadband absorbers at first reflection points. Mobile stack of absorbers on rear wall including a bass trap.

But no corner treatment. Budget of £1,600.

[Wonks]

Have you got back to them to ask why no corner traps?

And if you go the GIK route, is there any guarantee on results if you install what's suggested, where suggested?

[Hugh Robjohns]

Corner traps aren't a legal requirement!

There are many different solutions to most acoustic problems, including bass trapping.

What matters is that low frequency reflections, especially passing through the listening area, are prevented.

If you have the space (room width/depth) to do that efficiently just using traps mounted on the walls, then great. It's what most commercial studios do, in fact.

For most home studios, though, it's usually more practical to use the (normally wasted) corner spaces...

[jellyjim]

Have you got back to them to ask why no corner traps?

And if you go the GIK route, is there any guarantee on results if you install what's suggested, where suggested?

I'm going to get back to them yes. Just thought I'd check in here first.

No, no guarantees. I think I'm better off doing the DIY I've suggested so I can install, measure, tweak, iterate. And then possibly go back to GIK for specific problems that aren't easily solved with DIY such as tuned membrane resonators. Or at least it's my understanding they're tougher to DIY.

Just waiting on some fabric and I will have finished my first reflection point absorbers. 1200mm x 600mm. 100m RW3. 50mm air gap. I've got a method now and have begged, borrowed all the tools I need. I reckon I can knock out new panels in an afternoon and an evening.

Having fun with the free version of Fusion 360 and a Udemy course visualising/designing some corner bass traps, hopefully with an internal hanging membrane. They're next!

[jellyjim]

Corner traps aren't a legal requirement!

There are many different solutions to most acoustic problems, including bass trapping.

What matters is that low frequency reflections, especially passing through the listening area, are prevented.

If you have the space (room width/depth) to do that efficiently just using traps mounted on the walls, then great. It's what most commercial studios do, in fact.

For most home studios, though, it's usually more practical to use the (normally wasted) corner spaces...

Great. I've no reason to doubt GIK's analysis just wanted a second opinion!