Soundman2020 - Studio Design Forum

Hello Folks

As you can see the progress is quite good on my studio. Building will be complete in only a couple of weeks and then they will frame the internal walls. I am planning to set up my control room for 5.1 mixing (even though it is a bit small, only 18m2). I am wondering if the subwoofer should be in the front wall with the L, R and Center speakers? I have seen some studios have it under the control desk.

Any experience?? I guess some of you have a sub in your control rooms?
Thanks for the advice,
scott

The sub should go where it does the job right! In a CR, the sub has two jobs; 1) Provide the low end for the mix, and 2) Deal with some of the problematic acoustic issues, such as modes and SBIR. For #1 the sub should go somewhere close to the front wall, not centered, exact location found by testing. For #2, it should go wherever it needs to go, and finding that spot can be painstakingly slow and boring... but VERY rewarding! A sub in the right spot can do magic for acoustics. That's part of the final room tuning, so it is probably too early to make the decision on where.

Also, room setup and treatment is different for 5.1, because you have speakers at the rear, facing forward, where they can potentially cause reflections that get back to the mix position. It is important to deal with that in the speaker placement design, and initial treatment design.

Have you decided which 5.1 speaker layout you want to use? There are several. That will influence the room shape, and the sub placement too.

- Stuart -

if you're not soffit mounting the rest of the speakers, the sub can just float - as Stuart noted - positioning is key. generally somewhere slightly off center and between your listening spot and the front speakers. one trick is to pub the sub in your chair in the listening spot, and using your REW tone generator to create short sweeps from 20Hz-120Hz, move the microphone around near the floor to determine where the best overall response is occurring across as much of the sweep as possible.

put your sub there to start. then balance the levels. i use a full rang7e weighted pink noise to start with a c weighted sound level meter at the listening position. full volume on the monitor controller is set to achieve 85db across all speaker sets. this requires some tweaking of the sub crossover frequency and levels as well as timing delays. this can take several hours to get all the speakers and sub to behave consistently as i usually monitor at 75db or lower (about mid volume on my controller). i recheck about monthly or before any big projects, this usually only take about 15 min.

i use my sub via a 3-way electronic crossover so i can easily switch it out or in. i use it with a single mono speaker. several pairs of stereo speakers, and my 5.1 surround, the .1 is controlled via the x-over and not the amplifier unit. decoding encoding is done in the PC.

This is all something that I will discuss with Joules. He is making plans at the moment, I think. For sure we will try to move the sub around and find the best location. When I last spoke to Joules, we will flush mount all of the 5 speakers, including the rear. I would love to see


I think we will go for this design though. Not sure when Joules is starting here yet but we will have time to work all of this out.
thanks for the feedback.
scott

Hello Folks.. hope you are all doing well. Joules will start soon and we recently discussed the subwoofer and he wants to mount it in the wall at the front center of the room. Stuart and Glenn both mention the front part of the room near the middle but moving it around to find the best spot. If you think it can not be put in the front wall with the center and left/right speakers, then I need to make this clear to Joules soon as he will be here in a week or so.. Any comments??? It seems if you are going to put it in the wall you need to have a lot of mass. He has talked about filling the wall with sand as well as all the massive amounts of wood he has planned.
scott

I would not ever flush-mount a sub. It limits your options way too much, even assuming that the optimal location happens to be at that spot in the front wall (as opposed to a few inches further out/in/up/to the side). I would also not ever position a sub on the room center-line, as that creates more problems that it solves. (For a start, it places the sub in a null for itself, for certain frequencies related to the room dimensions (especially width) and a peak for other frequencies...). There's also the issue of the sub itself: Some subs have downward-firing drivers or ports, or other physical design constraints, that make them unsuitable for flush mounting, or indeed for any type of "in-wall" mounting (flush or otherwise). A fixed mounting location for the sub also assumes that nothing in the room will ever change. If you decide to put in/take out racks of gear, move the client couch to a different spot, or take it out completely, or put one in when you didn't have any before, or replace it with a considerably larger/smaller one... any change to the room that modifies the location/mass/size of large objects in it, could potentially require moving the sub to compensate. This is a real issue: In the first of the two studios I'll mention below, we really did have to move the subs around aster the owner changed his main speakers for a different brand/model, and also after he move the client couch to a new location. It's not just theory: it is necessary in real life too.

Of course, with the above comments I'm assuming that you want a room that is accurate in the low end, and where mixes translate well. some people don't seem to care much about accuracy, or following the ITU BS.1116-3EBU / EBU Tech.3276 specifications for such rooms. It's a matter of personal preference, I guess. If acoustic accuracy and good mix translation are important to you, then it's a good idea to follow the best practices for achieving that. As Glenn mentioned, there are tried-and-tested methods for doing that, such as the one he outlined for sub placement. It just works, and there are solid, sound, technical reasons why that works. Here's the type of response you can get from a well designed and properly treated and tuned control room: S3P. That one used two subs, one a little away from the front wall, slightly offset to the right, and the second one next to the far left leg of the left wing of the desk. Here's some similar graphs from a room that we are currently tuning, also with two subs, located inside the speaker soffits, on the floor, next to the side walls, but in different positions that were located using a similar method to what Glenn outlined:

Frequency response and phase response (full spectrum, 12 Hz to 22 kHz):


Low-end spectrogram (20 Hz to 230 Hz - the most important part of the spectrum):


RT-60 decay times in one-third octave bands (Full 1/3 spectrum, 45 Hz to 12 kHz.) The horizontal cursor line marks the original design goal for the room, at 200 ms. :


The same one-third octave decay times graph, but with the BS.1116-3 overlayThe highlighted section shows what the BS.1116-3 specification requires for critical listening rooms. The spec calls for the times in adjacent 1/3 bands between 200 Hz and 4kHz to be within 100ms of each other (+/-50 ms) This room is far better, with less than 86 ms difference (+/- 43ms).


In fact, the room meets the +/-50 ms specification over a far wider frequency range that the spec calls for: from nearly an entire octave lower (120 Hz) to 2 1/2 octaves higher (20 kHz, all the way to the top of the spectrum):


Low-end waterfall plot (20 Hz to 230 Hz - smoothed to 1/6 octave):


And because some people might think that smoothing such a graph is an attempt to "hide" stuff, here's the waterfall plot, with no smoothing at all (1/48, the lowest setting you can get on REW):


As you can see, both of these rooms get exceptional acoustic response, even better than is required by the specs for control rooms: Because they were designed, treated, and tuned using industry best practices, such as those mentioned by Glenn and myself earlier and in other threads. That's what can be achieved in a properly designed, treated and tuned room.

I doubt that it would be possible to achieve such results with a sub locked into a fixed location in the front wall, and inadequate bass trapping / overall treatment.

Sand-filled walls? Well, color me skeptical on the cost/benefit for that, apart from the complexity, and not to mention the risks. Ditto regarding flush-mounting the rear-surround speakers. Here too, if those are in fixed locations, you cannot adjust them to meet the various different versions of 5.1 layout. You are locked into one single version, at that specific angle and elevation.

But having said all that, I go back to the point of how good you want your studio to be. This is is somewhat of a personal preference issue, depending on the purpose of the studio: If it is just for hobby mixing, making demos for your friends, or your own personal work, then accuracy need not be a big issue. If you want to do high-end pro work, and especially if you want to do mastering in there (either now, or in the future), then better precision and good translation would probably be important. On the other-other-OTHER hand: some "hobby" studio owners still want very high precision rooms, and some high-end pro studios seem to not care at all about such issues....


- Stuart -

Thanks Stuart. you wise words are always welcome. We will for sure not put the subwoofer in the wall now or the rear speakers. I think Joules and I had spoken about putting them on Stands attached to the walls as opposed to freestanding stands. As for what I want, I have not spent all this money to have anything less than a studio that amazes people and we an make world class professional mixes!! We will make all the appropriate sound measurements and treatments to make this slightly too small 18m2 control room as world class as we can. We have all the materials, the skills of Joules and his crew and your advice, so we should not end up with anything less than a world class place that amazes people... No room for fucking it up now as he is starting next week..

Thanks Stuart..
scott

sand filled walls can be a nice thing but tend to be complex to build and load. however, building the soffit walls to be filled with sand is a definite option as the sand has mass and is a really good damping material. on a note about subs, mounting them in the soffit can be productive but requires careful design because of potential alignment issues - often adjusted via active cross overs to time align - plus additional significant source of vibrations in the soffit need to be addressed.

gullfo wrote:Source of the post sand filled walls can be a nice thing but tend to be complex to build and load. however, building the soffit walls to be filled with sand is a definite option as the sand has mass and is a really good damping material. on a note about subs, mounting them in the soffit can be productive but requires careful design because of potential alignment issues - often adjusted via active cross overs to time align - plus additional significant source of vibrations in the soffit need to be addressed.

Thanks Glenn.. We are going to have a huge amount of mass in the front and back of the room from what I have seen from the plans so far.. I can discuss these issues with Joules but I have a feeling it might be wise to have the sub in the room as Stuart points out if you ever change your monitors or make modifications to your room, you will probably appreciate the flexibility of being able to move the subwoofer.. For sure stuff to discuss as I want this to be perfect.. It has to be!!

Thanks Glenn..

Dr Space wrote:Source of the post I have not spent all this money to have anything less than a studio that amazes people and we an make world class professional mixes!!

That's what I figured! You have a pretty major investment in there, and I know all the heartbreaks, setbacks, problems, and delays that you've been through over the years it has taken you to get where you are today .... so I was rather certain you'd want to get is as good as it can possibly be.

We will for sure not put the subwoofer in the wall now or the rear speakers. I think Joules and I had spoken about putting them on Stands attached to the walls as opposed to freestanding stands.

OK, this is a little confusing: You are talking about "them" in referring to having more than one sub, and having it/them on stands? Or does "them" refer to just the rear surround speakers? I'm guessing the latter... A single sub upfront somewhere, and movable but not on a stand, with the rear surrounds on stands? That would make sense.

There are several "flavors" of 5.1, with different locations and angles for the rear surrounds, so I prefer to have them on stands just in case you have some strange situation where you need to re-arrange things. I've seen layout diagram "standards" that specify angles of anywhere from 90° to about 160°, with the most common being 110°, 135°, and 150°. So just pick the one that you like most, and mark spots on the floor for the other locations, so you can shift your stands around easily and accurately, if you need to.

I'm attaching just a few of the many papers that I have come across over the years, and that I find both useful and confusing about this issue: One studio designer I know of even refers to this as the "5.1 speaker placement war"!

Of course, the issue of the rear surround speaker placement also affects the design of the front of the room: You have to be careful with any large reflective surfaces up front that could cause strong specular reflections back to the mix position! It's sort of the same as having reflective surfaces behind you, with regard to the main speakers. The 20-20 rule applies here too. Ideally, you don't want any reflections that are louder than -20 dB within the first 20 ms of the direct sound. It's the same issue sometimes called the Haas effect, or precedence effect: early reflections like that mess with the ability of your brain and ears to correctly identify directionality and frequency response (the two are related, because of the way your pinna (ears) work). It's a subtle but very real effect, and needs careful design of the room acoustics to make sure that the "20-20" criteria can be met for all speakers, not just the ones in front of you.

Regarding what Glenn said about subs in soffits: " but requires careful design because of potential alignment issues - often adjusted via active cross overs to time align - ", Absolutely right! And here's an example of what he's talking about: This graph shows the frequency response curves for a room I'm working on right now, with a pair of subs, carefully located at different spots along the side walls, close to the front wall: the various color traces show the results from ONLY the timing differences. Each line is for a slightly different time delay between the two subs (fractions of a millisecond) and between the subs and the mains (milliseconds). As you can see, using subs to tune a room is a very powerful tool, when done right. The concept here is sometimes referred to as a "plane wave bass array". In this case, it's not really a full plane wave array (that needs at least 4 and preferably 8 subs to do it right), but the same underlying principle applies. And obviously, it works very well! You can see, very clearly, how small timing adjustments completely remove the 89 Hz dip, as well as the 140 Hz dip. In both cases, there's a massive 15 dB difference between the tuning extremes. It is possible to get a good range of adjustment just with timing, but you get even more control when you physically move the subs as well. Timing only adjusts the relationship between the speakers, while physically moving the subs also adjusts the relationship between the sub and the room boundaries, and that is an even more powerful method of tuning the low end of a room. (For the graph above, the optimal sub positions had already been found before we did these timing tests, so those differences are ONLY due to minor changes in timing between speakers).

So: in summary: One fixed sub is ... "meh" useful only for extending the bass range, mainly. A fixed sub plus timing adjustment can do some things to improve some acoustic issues. A movable sub is better yet, as you can use it to deal with more room acosutic issues that a fixed sub cannot deal with. A pair of movable subs with individual timing adjustment per channel, is simply amazing, as it gives you excellent control, and you can implement the simplest form of a plane wave bass array. And four or eight subs set up properly with multi-channel timing adjustment is just out of this world! (But so is the cost, and the complexity of setting it up...)

Of course, you do have to be careful with the timing adjustments, as the result only really works for one specific position in the room, at the expense of some other positions. But that's true of all room tuning anyway, so as long as you do it right to optimize the mix position, you can get really, really good results.

- Stuart -

Wow Stuart.. Joules will be here Friday to start building the inside so these are things we can have a nice discussion about. He might not agree on all of them but he is very good and qualified to do this job so we will get it right in the end and have all the measurements to show just how good the room is!!

And Yes.. only one sub and rear speakers is what I was referring to. I will have to look into what are good economical stands. Any suggestions??

scott

https://www.youtube.com/watch?v=lRZrHF8rhhA

I will have to look into what are good economical stands. Any suggestions??

Probably not the answer you are looking for, but a really good, cheap speaker stand is a stack of sand-filled concrete blocks! ("cinder blocks", "breeze blocks", "Besser bricks", etc., depending on country). The fulfill all the necessary conditions: Very high mass, high rigidity, good damping, etc. You just stack them to a bit below the correct height, then make up the difference with plwood/MDF/solid wood platform, and sorbothane pads to decouple a bit, then wrap them with a nice finish fabric, and you are done! They work great, and don't cost much. The problem is portability! It's difficult to drag around a stack of bricks that weighs a hundred kg (or more). In your case, for the rear surrounds you do want them to be movable, so a "concrete stack" is probably not a good option.

I would suggest looking for the heaviest, toughest, most rigid stand you can find. Better yet, get your construction guys to build one for you: a large steel profile (eg, 100mm x 100mm, or 100mm diameter steel tube, min. 2mm thick) filled with dry sand, welded to a flat 4mm steel plate for a base, and with a height-adjustable top plate (eg. round steel plate welded to a length of threaded rod, which goes through a nut on top of the stand, with a lock-nut to keep it all firm once adjusted).

They key issues are: 1) It must be massive (very heavy). 2) It must be rigid if possible. 3) It must be damped internally if possible. 4) It should have some method for adjsuting the height of the top platform, if possible. 5) It must have some method for decoupling the speaker cabinet itself, from the stand.

The reasons for all of this are fairly simple: the speaker must not be able to transmit vibrations into the floor, or pick up vibrations from the floor, for obvious reasons. The mass, rigidity, and damping all help with that, as does the decoupling.

Overkill? Some people might think so, saying that the effect is small, blah-blah-blah, but I have a simple philosophy: If you can find ten very minor things to do to your studio, each of which improves it by just 1 dB in some aspect or other, then overall you have improved your studio by 10 dB! A 10 dB improvement in ANY aspect of your studio, is pretty major, and well worthwhile...

- Stuart -

I like the idea of sand filled concrete blocks, cheap, very dense but like you said, not very portable. Paint them black or cover in fabric in the end.

gullfo wrote:Source of the post sand filled walls can be a nice thing but tend to be complex to build and load. however, building the soffit walls to be filled with sand is a definite option as the sand has mass and is a really good damping material. on a note about subs, mounting them in the soffit can be productive but requires careful design because of potential alignment issues - often adjusted via active cross overs to time align - plus additional significant source of vibrations in the soffit need to be addressed.

So, we have decided to put the sub on the floor in the front of the room and not in the wall. Joules had planed to put it in the wall as that is what he said they do in most studios he makes these days and he has a lot of experience doing it but he understood the issue of flexibility and having it on the floor so we will do that. Joules is going to fill the front wall with dry sand at the front as well as use a lot of acoustic dead sheet.

They are back to work on Friday.