Attic Shaped Studio

#301

Congratulations Jennifer!

I can't wait to see your monitors flush mounted.

#302

Great work! Glad the new rear traps have had such an obvious impact. On to the next!!

Gareth

#303

Thank you chaps. I'm currently taking a bit of a break after the epic work of the last few months, after which it will be time to catch up with some music work :jammin:

Then soffits and cloud. Surely those will be simpler than what has just been done. I even have one of those Sakertool gadgets to cut the soffit baffle for round the Genelecs. Can't wait :yahoo:

Cheers!
Jennifer

#304

I tried out the new improvements for the first time today by doing a couple of mixes after redoing the monitor chain EQ to the B&K house curve. It's great, everything works! The fan sound is unobtrusive when mixing at my normal level, and the clarity, balance and separation of instruments is so much better than before. With a bit of bass extension from the speakers being in the corners the low end is getting very close to my headphones.

Mixing is so much more fun like this!

Cheers,
Jennifer

#305

I remember the same joy when, in my previous studio, we finished installing the rear wall bass trap.

Startlight wrote:The rear wall in now a 70cm (27") deep bass trap, following the principle of a Non-environment control room (see Recording Studio Design, 3rd ed., figure 16.1, page 457). I am staggered at the effect this trap has made: I can now hear individual instruments so clearly in my recordings and bought CDs.

Source of my quote.

Long may you have so much more fun mixing!

#306

Startlight wrote:The rear wall in now a 70cm (27") deep bass trap, following the principle of a Non-environment control room (see Recording Studio Design, 3rd ed., figure 16.1, page 457). I am staggered at the effect this trap has made: I can now hear individual instruments so clearly in my recordings and bought CDs.

Exactly this! Once the main balance was done I was amazed by how often I heard a bar or two of an instrument I wanted to push up by 0.5 dB or so just because it sounded cool in that moment. I've not felt consistently inspired to this amount of precision before.

#307

Fantastic news! I’ve been using my room for real too and it’s such a nice feeling. Will report more ASAP.

Get those soffits built, it’s truly a game changer.

Gareth

#308

garethmetcalf wrote:Source of the postGet those soffits built, it’s truly a game changer.

It will be done, make no mistake

#309

Get those soffits built, it’s truly a game changer.

Gareth

- Stuart -

#310

on the soffits ideas - you've probably already considered this - if you put the soffits purely into the corners with the edges aligned to the window opening, your triangle will likely become too wide, you probably noted the effects from contracting and expanding the width of the speakers on stands - at a particular point, your phantom center is correct in proportion to the sides. typically for most listening positions this is about 6' for smaller speakers and rooms. spacing should be about 70% of the room width or less than 8' whichever is less is likely right - a starting position, not a rule. my guess is about 6' would be closest to what you have now.
the problem then becomes, if you have your baffle plates properly apportioned for your speakers (say 24" wide x 36" high) and form your triangle on your listening position about 6' from the front window, you now have part of the window cut off on either side, and you have a deep cavity formed by the soffits (this latter part is true regardless of soffit approach).
if you consider that your field of view while in the listening position is constrained to about the same 60°, then the inset of the soffits doesn't significantly limit the view. and given much of the window is already block by the video monitor and existing stands and speakers etc. this could be an option - increasing the size of the soffits to extend into the window space slightly to achieve a better angle (my example below uses 34° for the angles, going to 30° would encroach further).
so view vs acoustics.
then you have the deep cavity. as we know deep cavities have resonant properties. this will be no different. so, consider that an additional layer of windows which marry up the sides of the soffits and perhaps even change the angled portion above (effectively slightly flattening that space) align with the acoustic ceiling soffits (containing your ducts) could eliminate the resonances there. and thinner (or thicker) glass can alter the isolation and insulation aspects well. in my example the lower part has a frame section - useful for extending the electrical and audio lines to panels there, and would be the depth of an absorber in the bottom to trap the cavity resonances.
this approach extends the baffle then between the sides which will improves the overall response and preserves the center image (which will be impacted by the resonant cavity if not changed).
who knew creating baffle mounted speakers could be so much fun!

#311

Thank you Glenn, that is a brilliantly creative way of solving many problems. That it could offer increased isolation of the window bay is magnificent.

Unfortunately I won't be able to do this, partly because of budget limitations, but also because of building code. The house has three floors and in the UK this means it is subject to some fairly stringent requirements. One that has worked hugely in my favour is the requirement of all bedroom doors to be fire doors. The extra mass over standard doors is of course beneficial to sound isolation.

Another is that all rooms on the third floor - the studio floor - must have fire escape windows. The bottom pane of the rightmost window set is actually a glass door and the top pane opens up "Delorean" style to allow walking access to the balcony. This must remain totally accessible to avoid violating code.

The balcony is also a great feature to have. On a full band recording session last week, six of us in total, it was fabulous to have a break out there

No worries though! I have formulated a design that allows a monitor angle of 37°. Not ideal but close enough. I actually like having the speakers quite widely placed so the corner placement is ok. Perhaps due to my liking for LCR style mixing? Who knows.

It gives a bit of a bass boost too, useful for the Genelec 8030 speakers without a sub woofer.

Thank you again!

Jennifer

#312

endorka wrote:Source of the post I have formulated a design

OK, now you have me intrigued, Jennifer! I'm dying to see that! Got anything you can post?

- Stuart -

#313

Aha, it's been six months since my last post on this thread. There's been lots of music made in this studio since then, and the rear wall absorption and ventilation improvements have been worth their weight in gold. The rear wall bass trap has tightened up the acoustics for use both as control room and a live room. For a couple of sessions there were six musicians in there (including drum kit) so the ventilation and additional space freed up by getting loads of traps away from the floor/wall perimeter was well appreciated.

It's also given ample time to assess potential sound transmission improvements. Significant sound reaching the living room is only really happening now from exceedingly loud electric lead guitars. Bizarrely enough, acoustic drums aren't so bad, these lead guitars are much louder.

The first thing to improve is the wall from room 1 to the landing, shown in yellow. This must be done before speaker soffits can be built. Stuart has given good advice on this earlier, and I thought it would be good to do some more looking before leaping. I've done sound transmission measurements through that boundary, but thought it might be worthwhile attempting to figure out the contribution each element of the boundary is making to the overall transmission loss to guide improvements to each. There is the wall, the door, and a small window made from glass bricks.

To recap, the wall is a standard stud wall with one layer of 12.5mm plasterboard on each side. I've sealed perimeters, any sockets have had putty pads applied.

The door is an FD30 fire door, estimated mass/area of 27kg/m2. As detailed earlier, I've already made the door frame to stud join acoustically proper by putting in extra screws, sealing the perimeter and so on. There are perimeter seals and a drop seal to the floor.

I have no information on the glass bricks, but from studying datasheets of entry level examples it appears they should give similar isolation to a double glazed window.

Let's focus on what good real world data is available for, first the wall. I found a similar partition in IR761 so used the transmission loss measurements from that. I used the measurements of single leaf panels with insulation on one face from pp. 109-111 in Rod Gervais "Home Recording Studio - Build It Like the Pros" book for the door. Here's a graph of those two together;

The wall is purple, the door light blue. As one might expect, the door is better than the wall at low frequencies, the wall is better at lower mids, then the door gets better again at upper mids. The insulation on one face of the door helps with the latter.

I already have some plans to improve this, but first a question: is it possible to combine these two plots to give a graph of the attenuation across the frequency spectrum to the entire combined parition? One possible way that has occurred to me, inspired by the observation that a relatively small hole in a partition causes for more harm to the sound isolation properties of a partition than its size would suggest. Could this be the worse case? This is to assume that the weakest link in the chain at any point determines the response for the entire partition. This would give the black line in the graph below;

Does this seem like a valid approach? In general it ties in quite well with a real measurement I made of the transmission loss of that partition.

Cheers!
Jennifer

#314

One possible way that has occurred to me, inspired by the observation that a relatively small hole in a partition causes for more harm to the sound isolation properties of a partition than its size would suggest. Could this be the worse case? This is to assume that the weakest link in the chain at any point determines the response for the entire partition. This would give the black line in the graph below;

Does this seem like a valid approach? In general it ties in quite well with a real measurement I made of the transmission loss of that partition.

That is, indeed, a good way of looking at, when considering the wall as a whole. When standing very close to the door, then the isolation from that door might have a slightly greater influence on what you hear, as opposed to when you have your ear very close to the window. But what you are probably more interested in, is the overall effect for people standing at an arbitrary location out in the room somewhere, or out in the hall somewhere, and your assumption is valid for that: the "weakest link" for any give frequency bnand is most likely what you would hear.

Regarding how to proceed here: What overall isolation results are you getting right now, from just a simple test with your meter and full-spectrum music? In other words, when you have a full band playing in there (or your speakers playing similar music), what does your meter show inside the room and then out in the hallway? Also, what goal are you shooting for here? From looking at your last graph, I'm guessing that you are getting around 35 dB overall isolation at present? How much do you want to improve that?

- Stuart -

#315

Thanks for that Stuart, very reassuring to know these notions have some basis in reality

The current setup is good for most things. In room 2 you can't hear the monitors at mix level in room 1 (about 82 dB), and you can barely (or not at all) hear vocals and most acoustic instruments between rooms. None of these are audible on the ground floor. The main thing would be to reduce the sound of electric guitars getting through, and loud brass. Perhaps a bit of low end when I boost the monitors to check the rhythm section, but that and anything else is a bonus really. I'd be quite happy with a reduction in the sound transmission of amplified electric guitars.

Earlier on you suggested two layers of plasterboard (or equivalent) with green glue between them, mounted on resilient clips. That would be amazing, but a bit out of budget and tricky to implement around those glass bricks. Based on studio use over the last six months, I don't think that level of improvement will be necessary.

I already have all the materials to improve the same sized wall in room 2. Plasterboard, green glue, oak trim to pad out the door frame, screws etc. The plan was to put an additional layer of 15mm high density plasterboard (British Gypsum Gyproc SoundBloc) on top of the existing 12.5mm layer, with green glue between them. That'll give about 24 kg/m2.

I reckon I'll get excellent results by doing both rooms that way and increasing the amount of insulation on the door. Using the method of prediction described in the previous post with test data from green glue, here are the potential results for one such partition;

- Black is current wall and current door
- Red is improved wall and current door
- Green is improved wall and double mass door (like Rod Gervais super door)

Electric guitars go down to about 80Hz, with thumps and other noises potentially lower, so from just improving the wall alone;

- Difficult to say below 50Hz as that wasn't measured in the black plot, but I strongly suspect this will be improved. Useful for boosting the monitors to check the bass.

- Eliminating the dip between 80-200Hz provides a significant benefit for guitars and many other things.

- From about 200-500Hz the benefit is not so great, this is where the door is the limiting factor. Unfortunately electric guitars make quite a lot of sound in this region.

- Above 500Hz it gets better again.

Doubling the mass of the door gives a good improvement over that 200-500Hz region, and quite a bit more besides, well into the lead guitar screechy regions. It certainly looks worth doing.

Any thoughts & sanity checks much appreciated.

Cheers!
Jennifer

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