Bass issues in my new writing room...

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Bass issues in my new writing room...

Post by noisyneil »

THE ISSUE

I've got a pair of Neumann KH 120 A speakers, which are meant to be pretty flat down to 50Hz, but, predictably, there are issues with the bottom end. The oddest of these is that, when they're on the desk shelf (sitting on IsoAcoustics stands), the bass drops off in a straight line from 100Hz. Pushing the desk right up to the window improves things slightly, and putting the speakers on stands is better still.

I'm using IK Multimedia ARC to try to mitigate some of the dips and peaks, and the result is workable for the time-being, but to get any kind of solid centre image and bass response, I've had to pull my listening position quite far from the speakers, which leaves me feeling a bit disconnected.

THE ROOM

Here's a 3D model of the room to scale.

Here's a photo of the room.
Here's one from behind the speakers, looking the other way.

Room Dimensions:

Width: 330cm
Height: Main: 250cm, Kitchen: 213cm
Length: Window to kitchen units: 645cm, unit recess: 55cm

Facing the window, the left and rear walls are plasterboard, the right wall is brick and the floor and ceiling are both concrete. The five panels are 11cm thick Melatech.

REW MEASUREMENTS:

Here's a photo to give you an idea of the speaker and measurement mic configuration for the tests below.

Download Measurement Files


SOLUTIONS?

The room's usability is most important to me, so my ideal scenario would be to get the speaker stands just behind the desk. This would give me back about 50cm of floorspace and mean I'm not listening quite so far away.

Perhaps your discerning eye has spotted something in those REW graphs I could remedy with some kind of additional treatment. However, I'm aware that this can sometimes be a game of "hit and hope", trying various treatment strategies until the problem is corrected. That could get expensive.

GIK has recommended Tri-Traps in the corners behind the speakers and free-standing traps behind the speakers themselves. Will this make much of a difference? From what I've read, you need serious volume of absorption to make impact issues in the low end.

I described all this to a friend of mine who'd been in a similar position and said I should get a sub, so I've been hovering my finger over a KH 750 buy button for the past few days. This particular sub has the added advantage of DSP phase and frequency response correction (of the entire setup), so it seems like it might help fill in the low-end gaps as well as improve the performance of the existing two-way speakers.

If you've read this far, I'm already very grateful for your time, and if you have any suggestions or comments on any of the above, I'd be even more so.
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Re: Bass issues in my new writing room...

Post by RichardT »

I don’t know melatech but it looks to be a lightweight foam. It won’t be doing anything to tame the lower frequency behaviour in your room. It might be helping with first reflection points to some extent.

The GIK recommendation seems quite sensible. You can always get more trapping later. It’s very good value for money in improving your room’s sound quality.

I don’t think you’ll find mineral wool trapping to be hit and miss - in my experience, getting more gets you a better sound. Obviously there is a limit to how far you can take this, but the GIK recommendation is nowhere near it!

If you implemented the GIK suggestions and replaced your melatech with similarly-scaled mineral wool absorbers then you would probably be heading towards a quite well-controlled room.

Personally I wouldn’t buy a sub while you have such serious room issues. Get the room in better shape first.

When you have trapping in place, you will be able to experiment with different speaker / desk positions. At the moment you will be getting a lot of reflections off the desk if I read the angles right
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Re: Bass issues in my new writing room...

Post by noisyneil »

Thanks for the reply. You're right, Melatech doesn't do much
for the sub-200Hz area. I suppose I was wondering whether GIK's solution of two corner traps and two boundary traps will actually make a meaningful difference.

The existing foam panels on the walls and ceiling could be refilled with mineral wool. Perhaps that should be my first order of business? If so, can you recommend a product and density? Rockwool, presumably?

Thanks again!
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Re: Bass issues in my new writing room...

Post by Hugh Robjohns »

noisyneil wrote: Wed Aug 17, 2022 4:48 pmGIK has recommended Tri-Traps in the corners behind the speakers and free-standing traps behind the speakers themselves. Will this make much of a difference?

Acoustic problems respond best to acoustic solutions, so Gik are right... installing decent bass trapping will make a substantial improvement. But you are also right that you'll need a fair amount of trapping, ideally in the corners. Specially tuned traps may take up less space than broadband bass traps, but need to be designed for the specific room.

I described all this to a friend of mine who'd been in a similar position and said I should get a sub, so I've been hovering my finger over a KH 750 buy button for the past few days.

It's a common suggestion, but when the room is inherently lumpy at the bottom end, putting in more LF energy usually makes things worse rather than better. The subwoofer dsp will only replicate what you're already doing with your Arc system.

...it seems like it might help fill in the low-end gaps...

Another common misunderstanding. The 'gaps' (and peaks) are caused by the LF sound waves from the speakers reflecting within the room and combining with the direct sound. Where the direct and reflected sounds are phase shifted around 180 degrees you get a big dip. And the amount of phase shift depends on the room dimensions and signal frequency.

Putting in even more LF energy still creates the same dips and peaks in the room, while people outside the room wonder whats making the building shake.

The solution is bass trapping which stops (or reduces) the reflections inside the room. No (or reduced) reflections mean no (or reduced) peaks and dips.

In your situation I'd find a project studio acoustician to design an appropriate room treatment design for your specific room -- the different wall constructions and windows all affect the required solutions. For example, DACS offer this service although there are many others. A good designer costs, but its far more cost-effective than buying exotic subwoofer and buying random generic acoustic panels.
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Re: Bass issues in my new writing room...

Post by RichardT »

noisyneil wrote: Wed Aug 17, 2022 5:34 pm Thanks for the reply. You're right, Melatech doesn't do much
for the sub-200Hz area. I suppose I was wondering whether GIK's solution of two corner traps and two boundary traps will actually make a meaningful difference.

The existing foam panels on the walls and ceiling could be refilled with mineral wool. Perhaps that should be my first order of business? If so, can you recommend a product and density? Rockwool, presumably?

Thanks again!

Yes, they will make a difference, but more would be better.

Most people here have used Rockwool RW3 which is 60Kg/m3.
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Re: Bass issues in my new writing room...

Post by Hugh Robjohns »

This article describes the acoustic treatment I needed to get a reasonably flat bass response in my own project studio. You'll see how much space I had to devote to bass trapping...
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Re: Bass issues in my new writing room...

Post by Nazard »

Last week, I contacted Acoustic GRG - RPG products, and Matthew was very helpful, even though my requirements are quite modest. I got the contact link from Hugh's articles on his own studio: my space in our new house is almost identical in size.

http://www.rpgeurope.com/products/produ ... ducts.html
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Re: Bass issues in my new writing room...

Post by noisyneil »

Thankyou all for your replies. 🙏🏼

Another common misunderstanding. The 'gaps' (and peaks) are caused by the LF sound waves from the speakers reflecting within the room and combining with the direct sound.

Thanks for the explanation. I do understand that, as it happens, but I didn't adequately communicate what I meant by "fill in the gaps". ARC is able to improve things, but the KH 120 A speakers don't have much oomph in the low end to begin with, so corrective EQ is likely to tax them at the expense of overall headroom. I figured a sub might be able to take on that responsibility more effectively. As this is a writing room and not a mixing room, there's some leniency when it comes to faithfulness of representation, but it would be nice to have a solid low end.

In your situation I'd find a project studio acoustician to design an appropriate room treatment design for your specific room

I contacted Level Acoustic Design, who recently completed work on RAK Studio 4 (RAK is my wife's family business), and they said it would be £1-2k for them to visit the room and make their recommendations, before we even get onto build costs. Does this seem to be par for the course?

Most people here have used Rockwool RW3 which is 60Kg/m3.


This article describes the acoustic treatment I needed to get a reasonably flat bass response in my own project studio. You'll see how much space I had to devote to bass trapping...

I suppose if I refilled my existing panels with Rockwool and added some corner/boundary traps, I'd end up with a fair amount of absorption, at least at one end of the room. Not much I can do at the kitchen end.

Last week, I contacted Acoustic GRG - RPG products, and Matthew was very helpful

Would it be appropriate for you to give me a ballpark all-in cost for a room of that size, based on your experience? You could PM me I suppose.
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Re: Bass issues in my new writing room...

Post by Hugh Robjohns »

noisyneil wrote: Thu Aug 18, 2022 11:19 amARC is able to improve things, but the KH 120 A speakers don't have much oomph in the low end to begin with, so corrective EQ is likely to tax them at the expense of overall headroom. I figured a sub might be able to take on that responsibility more effectively.

A sub would certainly have more headroom but, far more importantly, you can potentially site it more optimally in respect of the room modes...

But fundamentally you still have the same problem: LF reflections interfere with direct sound resulting in partial cancellations and big peaks and dips in the perceived frequency response at the low end.

Throwing more power at it doesn't stop the cancellations. The ONLY real solution is to prevent (or at least radically reduce) LF reflections.

While you may gain some improvement by installing a sub — mostly through the ability to place it optimally which might reduce some cancellations — the extra LF going into the room will also generate massively more LF leakage outside the room.... and that's often a bigger problem.

I contacted Level Acoustic Design, who recently completed work on RAK Studio 4 (RAK is my wife's family business), and they said it would be £1-2k for them to visit the room and make their recommendations, before we even get onto build costs. Does this seem to be par for the course?

That feels on the high side to me....but much depends on what they are quoting for. What quality of outcome are they guaranteeing? I'd look around and get more quotes. If you're prepared to do the install yourself I'd expect the consultation and recommendation to be much less than £1k.

Most acoustic product manufactures have a bureau design service too... but few actually make workable bass traps, sadly!
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Re: Bass issues in my new writing room...

Post by jaminem »

Hhhmmmm, ok to be honest I think you're buggered....
The places you'd want to concentrate you bass trapping are in the corners and in the Tri corners, and Id want a load on the back wall, but you've got floor to ceiling kitchen there so I suspect the low freq's are hitting the kitchen and bouncing back and as Hugh says mixing with the output from the monitors.

At the other end you've got patio doors, which are:
a: very reflective
b: letting in light so you wont want to cover them in bass traps to stop the sound bouncing back at you.

Id definitely follow GIK's advice and put Tri taps in the corners but that's only gonna do so much. It also looks like the Kitchen ceiling is lower than the where you desk is, could you treat that bit ? that may help a little too, and maybe a big thick ceiling cloud potentially angled may also help.
You may get some improvement by moving the desk into the room, but thats gonna eat space which you say you don't want and to be fair with that sofa n there probably isnt practical

Probably not what you want to hear but for you I reckon headphones are the best choice. I fear you could spend a load of cash on treatment, it not do that much and you're still disappointed...

I suppose the other choice is turn the desk 90 degrees so you can get some traps behind the desk and behind you, but that's gonna mash your stereo image unless its centrally placed, which will also eat space.
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Re: Bass issues in my new writing room...

Post by Wonks »

Bass traps don’t have to go in corners, but they are far more effective there. You’d probably need almost twice the amount to get the same effect if they went against a wall.
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Re: Bass issues in my new writing room...

Post by James Perrett »

One thought - could you hang a heavy curtain in front of the kitchen area which you can pull across when you need to do some critical listening? This would certainly help reduce higher frequency reflections.

The other place you could put bass traps is at the wall/ceiling corners along the side of the room. I would have thought that there is also scope for trapping in the corners next to the patio doors.
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