Skol303

Well done Pete, a great improvement! Frequency response is looking good. Very good for an untreated room. There’s still the weird ‘scoop’ starting at 9kHz which has me puzzled… but not overly concerned (some thoughts on that in my email). Reverb time looks fine. Notice the sudden jump in the reverb time around 70Hz in comparison to your previous measurements. That’s almost certainly due to the new measurements being taken at a higher SPL level, which always shows up details you don’t see with quieter measurements. Again, no cause for concern here. Acoustic treatment will help. Decay times are actually fine - it’s just that your waterfall graphs are showing more of the ‘Y’ axis than they need to! Bear in mind that the background noise in the room is probably around 30dB, so much of what you’re seeing in your graphs that looks horrendous is actually just inaudible guff. Here’s a more realistic interpretation… note that the ringing at 50Hz is perfectly normal; lower frequencies naturally have longer decay times and what we're seeing here isn't problematic. I’ve also checked the impulse response and it’s very similar to the original position - i.e. showing lots of early reflections that acoustic treatment will improve on. Again, nothing that leaps out as being troubling. Off to a great start! Keep us posted only your next steps… 👍

^ You're welcome. I'm very much an amateur when it comes to acoustics, but I do get an odd sense of enjoyment out of it. Sort of my equivalent of doing a good crossword 😉

Update: I’ve now received a sketch of the room showing its dimensions and the sloping areas of the roof space. Very useful! It’s slightly larger than I’d guessed, which is a good thing. Room Modes Here’s the pattern of room modes (standing waves) in Pete’s room, based on its dimensions (length/width/height). Tall, red lines indicate particularly strong room modes; and we can see there are strong modal frequencies at 36Hz and 55Hz, which coincide with the slower decay times seen on waterfall graphs above. So at least we know where the biggest low end problems can be found. Both of these low frequency room modes are treatable, but the one at 36Hz is going to be difficult to reduce without installing truckloads of acoustic fibre or pressure-based bass traps (expensive to buy and tricky to DIY). Although from what I’m seeing, I don’t think we need to worry about it. Curiously, the room dimensions fall within the ‘Bolt Area’ (see screenshot bottom-right), which means that the room modes should be quite evenly distributed in this space. That’s a good thing; but bear in mind that all of these estimates assume the room has vertical walls… so the angles in the ceiling might be sending some of these predications skew-whiff. Moving the Listening Position As mentioned above, I think the priority here should be fixing the lack of symmetry between the left and right speaker responses (as the rest of the room seems generally ok as a starting point). And to achieve that, I think we need to find better symmetry in where the listening position is located in the room (i.e. the desk and chair). I’m fairly sure that having it in the corner is what’s causing the big dip in the left speaker around 100Hz (i.e. a cancellation null due to the proximity of the nearby wall). Theory tells us that it’s usually best for speakers to fire down the longest dimension of the room, which would mean moving the listening position to one of the shorter walls (the one with the "wife's desk", or the one with the bookcase). But theory isn’t always right ...and I’m wondering whether the acoustics might actually fair better with the listening position located where the sofa is currently - especially if the door is left open. These decisions are ultimately Pete’s to make and boil down to his own priorities for the room. All things considered, my recommendation remains unchanged from above: i.e. try moving the listing position to the opposite wall (where the sofa currently is) and measure here twice using REW: once with the door closed and again with it open to allow comparison. My guess is that will help to fix the symmetry issues between the two speaker responses… and with the door open I'd expect to see an improvement in that 30Hz mode (e.g. faster decay time). But moving the listening position here may also cause a whole new set of problems! Acoustics tends to be full of frustrating compromises 🙂 So yeah. Try that new listening position, take some new measurements and we’ll then revaluate before looking at options for acoustic treatment.

Recommendations Here’s what I’d suggest as first steps: Make sure that all future acoustic measurements are taken at a higher dB level. The current batch are around 56-57dB which is way too low… bearing in mind that the typical noise floor of a quiet room is around 30-35dB. So we’re probably losing some of the detail in these measurements. Shoot for around 70-80dB from now on. Wear earplugs if necessary (or better still, vacate the room!). Before we start planning any acoustic treatment, we need to find the optimum listening position for this room. That is: the best possible location for the speakers, desk and chair. Acoustics favour symmetry and so the current set up (with the listening position in a corner) is not ideal. My suggestion would be to swap the position of the desk with that of the sofa: i.e. move the speakers/desk to the rear wall (where sofa currently is) and move the sofa into corner where your listening position currently is. The line to take with your partner is that the sofa will be nearer the window which is better for fresh air and feng shui Position the desk at the centre point of the rear wall, push your speakers as close as possible to the wall (within a few millimetres) and take another set of REW measurements. Also take a set of measurements with the door open - my guess is that may help tackle the modal ringing around 30Hz (free bass trapping!). Keep repositioning the speakers and re-measuring in REW until you find what seems to be the ‘sweet spot’. Given that your reverberation and decay times are already very workable, what you need to focus on here is finding symmetry between the frequency response of your left and right speakers. Keep moving and measuring until the two graphs appear the same (broadly speaking). Finding the right listening position is half the battle with acoustics… if not most of the battle. Once you’ve got your listening position sorted, post the new REW results here (and email me with a copy of the .mdat file). We can then look into what acoustic treatment is going to be most appropriate and practical, mindful that it’s a shared space.

Waterfall Graph (decay) LEFT SPEAKER: RIGHT SPEAKER: This shows how different frequencies decay over time; and it’s just as important as the frequency response. At this stage we’re really just concerned with the low end below 200Hz… and what we’re looking for is ‘modal ringing’ - those elongated spurs that stick out from the main body of the graph, showing frequencies that take longer to decay than others. These are caused by room modes - aka standing waves - which are determined by the size and shape of the room. Modal ringing is inevitable in every room, but too much of it can cause big problems when mixing (e.g. a ‘boomy’ low end that makes it difficult to discern between different bass notes). Generally speaking, you want the decay times to be as even as possible across the frequency range, mindful that some irregularities in the low end are inevitable. In Pete’s graphs, we can see clear evidence of modal ringing around 30Hz and 60Hz (seen in the measurements from both speakers), as well as other frequencies. The 30Hz ringing is especially gnarly, given that the speakers don’t seem to be producing much output at the very low end. So we definitely have a strong room mode acting at that frequency… and I'm guessing it's due to the room dimensions being of equal lengths (square rooms suffer from the worst modal problems). If so, this is going to be difficult to remedy without installing truckloads of acoustic treatment. But... 30Hz is a frequency that’s more ‘felt’ than heard, so it’s nowhere near as problematic as modal ringing at low end frequencies above this range. Other than that, both graphs look good in terms of decay times. No cause for concern, based on what I’m seeing here. The ‘Grand Canyon’ in the frequency response of the left speaker is very evident however. Definitely need to fix that, speaking of which…

Reverberation Time The classic ‘RT’ measurements (RT60/30/20) are designed for concert halls and don’t apply with any accuracy to small rooms. However, REW has its own clever interpretation (called Topt) which is designed to give a better representation of reverberation in small spaces. Industry standards (such as EBU Tech 3276) suggest a reverb measurement of 0.2s rising to 0.4s in the lower frequencies, so Pete’s room is already performing well in terms of reverb time. Happy days. As mentioned above, this is almost certainly helped by using smaller speakers.

Impulse Response Impulse response is easy to overlook when you’re starting out learning acoustics, but it’s a very useful measurement. The peaks in the response represent reflections and can be used to work out the location of boundaries that need acoustic treatment. For example, in the screenshot here, the first big spike is caused by a reflection off a surface that is located [4.38 ft + the distance from the speaker] away from the microphone. Hours of fun to be had with that! (which I’ll explain another time…). In a ‘good’ response, you’d want to see no or very few peaks above 20dB (that is confusingly, between 0 and -20dB on the graph) within the first 20ms. On Pete’s measurement, we see a lot of reflections in this region… which is perfectly normal for an untreated room. And even in a well treated room, it’s common to find spikes caused by furniture and other surfaces. For the time being, there’s no point getting into the detail here until we’ve found the optimum listening position. So I’ll park it and move on.

Frequency Response Left speaker red; right speaker green. Very typical of a small, untreated room… but not too bad at all. I’ve seen a helluva lot worse! So that’s a good start. There’s an obvious difference between the left and right speakers around 90-100Hz, notably a big null (dip) in the left speaker and a peak in the right speaker. This is almost certainly caused by the left speaker being close to the adjoining side wall. Our ears - or more correctly our brains - tend to ‘sum’ low frequencies to mono below around 80Hz (which is why many subwoofers crossover at this frequency). Above 80Hz we’re able to more accurately pinpoint the source of low frequency sounds, so I’m guessing that the inconsistency in Pete’s room around 90-100Hz is audible, albeit perhaps subtly so. Either way, we definitely need to fix it. In the low end below 200Hz, the frequency response varies by around +/-14 dB in the left speaker (i.e. the difference between the loudest peak and lowest dip is 28 dB) and +/-11 dB in the right speaker. A variance of +/-10 dB in the low end at 1/24 smoothing is generally considered ‘acceptable’ for a home studio, so we’re already close to a workable result. Like I said a good start, especially if we can get the left speaker response looking more like the right speaker. Having small speakers is a real advantage in a room like this. The frequency response here drops off around 50Hz, which isn’t ideal when it comes mixing the low end, but it does greatly reduce some of the common low frequency problems in small rooms. Using headphones as a second reference is a way of helping to compensate for the lack of ‘oomph’. There’s a weird dip in the high end commencing around 8-9kHz. Never seen that before, but my guess is that it has to be a Boundary Interference Reflection (BIR) - i.e. sound waves bouncing off a hard surface and cancelling out where peaks and dips of the same magnitude and frequency meet each other. You can see evidence of these boundary reflections, also known as comb filtering, throughout the frequency measurements - the jagged little peaks and troughs in the mid and high frequencies (usually more pronounced in the highs, because high frequencies are more susceptible to reflecting off hard surfaces). The fact that this weird null appears very similar for both speakers means that it’s not just the adjacent wall that’s causing the problem. So it may be something to do with the irregular shape of the roof space.

Ok, time for some analysis of Pete’s results, posted earlier. Firstly, here’s a rough plan of Pete’s room, which I’m guessing is around 3m square: This is a classic ‘small room’ set up that’s very typical of most home studios; so it makes a great case study for anyone else starting out with acoustics. As such, I’ve tried to include some general advice along with the detail, because much of what’s being discussed is applicable to any small space… so thanks to Pete for providing the data and being our guinea pig. It’s a long read, but it’s a big subject and as the kids would say: “go hard or go home” Right, that’s enough preamble. Let’s get to work…

Cheers! It’s been a labour of love; very educational and strangely enjoyable. I’m still chasing some minor improvements... but the diminishing returns are now so steep that it’s becoming difficult to measure let alone hear the benefits. That’s what I like about acoustic treatment: there’s an end point in that you either run out of money or space! It’s a finite form of GAS Good points above about sound proofing vis-a-vis treatment. I haven’t attempted a soundproofing project myself so can’t comment from experience, but I know it’s an endeavour that doesn’t reward half measures. @charic don’t let that put you off though mate! If you’re a handy DIY-er then you can make a very decent job of it with sufficient elbow grease (and budget). If you’re interested I highly recommend this book: Home Recording Studio: Build It Like the Pros Quite technical in places, but nothing you can’t get your head around! Covers everything you need to know about building a home studio from scratch. The author, Rob Gervais, is also quite active on gearslutz.com and commonly responds to questions. I found it overkill for my purposes - mine wasn’t a build project as I wasn’t aiming for soundproofing, but it was a good read nonetheless. If I can find my copy you’re welcome to have it... I’ll have a root around the bookshelf and see if it turns up.

Small rooms by their very nature nearly always have terrible acoustics, that’s a fact. Gig venues are generally larger and thus less susceptible to some of the worst issues; but they can still sound crap. Acoustics are reliably unforgiving at the best of times. PS: The idea of a drummer going full tilt in a room the size of a domestic garage is plain crazy to me. Makes my tinnitus go wild just thinking about it. Some of you guys must have thoroughly trashed hearing. I SAID SOME OF YOU GUYS MUST HAVE... oh never mind 🙄

PS: photos or a rough sketch of the room with measurements would be useful.

REW results! Excellent. Now we can get to work... Email the REW .mdat file to me here and I’ll take a proper look at it for you: [email protected] You ideally need to measure left speaker on its own; right speaker on its own; and then both speakers together (but not a big problem if you haven’t done so). At first glance your frequency response looks very typical of a small room; no concerns there other than the big dip in the high end which is unusual. I’d need to adjust the view on your waterfall graph as it’s currently just showing a load of ‘noise floor’ (background hum in the room) which is masking a more clear interpretation of the results. I can also check the impulse response for any significant reflections (again hard to tell from the view you have above). Email over the file and I’ll post some thoughts here, along with some new graphs 👍

You're welcome! This is one of the best introductions to REW and acoustic measurements that I've found. Follow the advice there and you won't go far wrong

And I don't think you can mention soul without this modern-day classic...

Peaks most likely yes; dips most likely no

Hi Pete, Firstly, it's "not too bad"! It looks like a typical untreated room and I've seen a lot worse. Sonarworks is a great tool for room EQ; but a poor one for actually measuring room acoustics. I assume you must have a measurement microphone? If so, download a copy of Room EQ Wizard (for free) and use that instead - it's a different league and you'll get a much clearer picture of how your room is behaving. That said, from the Sonarworks image you've posted I can suggest that: The low frequency dip around 80hz is very common, to the extent that literally every small room will show a similar dip (usually somewhere between 60-100Hz). It's caused by a standing wave (aka a 'room mode') and/or what's known as SBIR (surface boundary interference response). Likely a combination of both. Try pushing your speakers right up against the front wall - literally within a few millimeters, which should help to lessen it a bit. Beyond that you need install acoustic treatment, especially on the rear wall. 60cm depth of fluffy insulation (same as what's in your loft) is ideal. The peak at around 160Hz is likely caused my another room mode, this time resulting in a peak rather than a cancellation (here's a handy tool for working out the modes that are present in your room). Sonarworks should be able to get that under control to a large extent. What looks like another cancellation dip around 300Hz (i.e. caused by sound reflecting off walls/ceiling). Things then get a bit weird in the high end! The peak at 8Khz, followed by the dip around 12kHz, are also likely to be boundary reflection/cancellation problems (aka comb filtering), but it's unusual to see such a large dip in the higher frequencies. Possibly something to do with the shape of the room itself. Carpet will do very little to reduce reverb time (other than in the high frequencies). What you're not seeing here are the decay times, which are arguably just as - if not more - important than the frequency response, especially in the low end (where long decay times are notorious for causing 'frequency masking' - i.e. making it difficult to discern between different bass notes). Get REW hooked up, as you mention, and give it a shot with that instead. Unless you're able to clap at 50Hz...

The only time I ever visit a music shop is when I need something immediately that day and am too impatient to wait for an online delivery (a set of strings or a patch cable, for instance). I’d love to say I’m more supportive of music shops, but I just find it far more convenient to shop online. Although I appreciate that’s perhaps not a popular opinion I just can’t be doing with the faff of: Actually visiting them. Finding out they don’t stock what I need when I do visit (despite it being shown as available on their website). Discovering that I could have bought the same item cheaper online anyway. Human interaction generally. I can see the value if you want to try out an instrument before you buy it. And I'm all for shops offering a more independent alternative to faceless globalism, etc. But meh.

Aye it's an interesting part of the country and somewhere I'm familiar with. You have Clitheroe (or Clit Hero as I refer to it), which used to have (and perhaps still does) the "highest concentration of millionnaires-per-square-mile in the UK outside of London". And in stark contrast you towns like Nelson that suffer from severe levels of socio-economic deprivation.

Yep, I would certainly vouch for Sonarworks (having used it myself) and also Dirac Live (which I use now). The latter gets a better grip on the low end in my experience; at least that's what I observed from acoustic measurements taken in my own room. Room EQ software does nothing to fix boundary reflection nulls and slow decay time problems, as you mention. But it's great for reducing peaks and allowing you to control the overall shape or 'house curve' of your room's frequency response, in ways that are difficult to achieve with acoustic treatment alone. Some pro studios also use Trinnov, but you need around £4K to burn for that. I'd normally recommend EQ software as the 'icing on the cake' - something to use once your room acoustic treatment is otherwise finished. But if circumstances dictate that it's the only option available then sure, go for it! 👍

In case anyone finds this useful... slim chance, but you never know!... here's a link to a whole bunch of acoustic measurements from different rooms, which I compiled over on the Gearslutz forum: https://www.dropbox.com/s/bt7xvsok7w3r4u6/Gearslutz.mdat?dl=0 It allows you to view and compare what the acoustics of different people's rooms 'look like'. Each measurement contains notes on the size and volume of the room, plus a link to the relevant thread on gearslutz.com where you can read up on the methods of acoustic treatment used. You'll need a copy of Room EQ Wizard software to open the file, which is free to download from here: https://www.roomeqwizard.com Maybe useful to anyone who's planning to improve the acoustics of their room and wants to get an idea of what the end result might look (or more importantly sound!) like.

For me it’s: That tone, which cuts through the mix like a buzzsaw Great build quality Optimum string spacing and playability (personal preference of course) I love Fender too. But with the StingRay, Leo and company got it spot on.

It's not merely a clause; it's a Commandment 😉

If you're having to ask this question, then your first option - using a backing track - is going to be by far the simplest and less 'risky' solution. Setting up a live rig for triggering loops and samples is of course very achievable (some good advice in this thread here), but it obviously takes some know-how and practice to do so confidently. If you know (or hire) someone who can set this up on your behalf, then great. You're away. If not then the learning curve can be steep at first, depending on how familiar you are with music software. If you're new to digital music tech, then be prepared to dedicate at least a few months of regular learning/practice to become sufficiently adept at performing live. There's no shortcut here, unfortunately. It's the time-honoured requirement of hours invested = confidence gained; exactly the same as learning to play an instrument. Hence a backing track may be the quickest and easiest route in this instance.