Digital Room Correction vs Room Treatments

Guys, really? Sorry to tell you OP that graph posted has a terrible response, about 20dB difference between the major peak and null. The null at about 58Hz is 12dB below the average. That’s a lot of musical information being lost in the most important range. The huge peak at 35Hz taking much longer to decay than the rest is going to make the bass slow and boomy.

I don’t agree with DSP. How can it reduce the long decay times and it can not et rid of that null. No matter how much power you pump into it, it will just cancel with the same power.

You can push the furniture and speakers around all day and you will still have peaks and nulls only at different amounts and frequencies. All rooms. I say again, all rooms will have these issues.

To achieve a smooth response some absorption is needed to avoid long decay and address bass problems with at the very least a pair of subs. They do not need to be the same brand nor size but avoid ported subs and they must, must have variable phase otherwise you’ll be endlessly pushing them around the room. Any ports that resonate at only one chosen frequency complicate matters further. You are adding a frequency invariant bass source with no way of tuning it.

OP I commend you for having the ability to measure as it’s the only way to remove guesswork.

@captouch, yes I'm talking about bass traps which because of the long wavelengths involved need to be large. Mine run floor to ceiling and are 3ft. across the width. It's a standard 600mm x 1200mm x 50mm rockwool or glassfibre board cut in half = 2 off 600mm x600mm squares then cut across the diagonal. If you are handy these things are simple to build inexpensively especially if you have demolishers nearby. I have picked up a truckload for 20% normal price and even some for free. Google DIY superchunk bass traps. These are to be placed in corners, any corners where walls meet including the floor/wall and ceiling/wall corners but is usefull just about anywhere. I helped a friend with a difficult room that had a deep recess that was used as an office and tunk receptacle which housed the vacuum cleaner, some suitcases and kids toys including bikes. I suggested filling with rockwool and made a framed rattan panel which looked very smart. A ceiling cloud acts as broad-band absorption and is useful down to mid bass frequencies.

You have a SVS ported sub with variable phase, great. I have the sealed box version. Two subs work well and will provide a much smoother response than just one. I suggest you position it where it is not an inconvenience, anywhere really and using REW dial it in to give the smoothest response, then plug the port and notice the change, now tweak the settings somemore. With the 2nd sub, again place it where it is the least intrusive perhaps even using it as a side table. Tweak again for smoothest response which will mean returning to the first sub for a little adjustment. By now you should have a plot that is vastly better to look at and to listen to. You will begin to understand why I avoid ported subs. Of course plugging the port on the SVS may produce a smoother result but that then is sheer luck.

Bass traps are hated by most who don't understand what is at play feeling they want all the bass they can get which is antithetical to trapping bass. Well looking at your frequency response you are missing a fair amount of bass. The bass traps absorb some of the low frequencies that build up particularly in corners but not exclusively. They help reduce the severity of room modes and standing waves.

There is a paradox here in so far as bass is being absorbed but more bass is heard. Prior to obtaining a smooth response the nulls apparent in your plots is revealing the frequency and the amount of bass absent from the performance.

Using Bass Traps and multi-subs together is a revelation. You have now effectively removed the room's acoustics from the performance, like listening to headphones, and are hearing the musical event. No new component nor DSP can achieve this.

Please report back and tell us what you saw and heard by plugging the port. 

Did you try plugging the port on your sub? Just push some foam or a sock into it. Yes of course playing with the phase (timing) will change the curve, that’s the whole idea. Get a second sub.

Does your SVS sub not have the ability to adjust remotely from your phone? There is more than phase to adjust. You need to also vary the output SPL, Raise or lower the crossover frequency, Change the slope of crossover from 6dB/octave to 24dB/octave, vary the Q and room gain. If you change any of these settings then go back and adjust phase again, and so forth.

Bass Traps?  from my post above:  The bass traps absorb some of the low frequencies that build up particularly in corners but not exclusively. They help reduce the severity of room modes and standing waves.

It appears you did not comprehend my long post trying to explain all this so the best advice now is to learn from the masters. Look at articles from Earl Geddes, Floyd Toole and Todd Welti on multi-subs. Fussing around with DSP will not get you there.

OP, let me apologise for assuming your SVS sub could do what I mentioned. Looks like you’ve got one of those  early models. I’m using an SVS SB 1000 PRO which sells for about $600 and has a very useful feature. Download the App and you can adjust all the parameters I mentioned from your phone but forgot there is also a few bands of PEQ. Check out their site. This is the sort of sub you need. There are other good subs available but the SVS is great value and I prefer it to my REL which has 0 or 180 degree choice so means I have to keep trying different places to get it dialed in.

I am using OmniMic to measure and I am not familiar with REW which  essentially does the same thing. I play a CD with sweep tones and have the mic. at my listening position sampling the combined sound of the speakers and sub/subs and while changing settings on your phone you can watch the frequency response change. The second sub will smooth the response even more. REW will also display  RT60 as a waterfall plot (CSD), the time it takes for the sound to decay by 60dB. The average room will be about 300ms.

I have 2 large floor to ceiling bass traps, broad-band absorbers, extra heavy curtains plus 2 subs and the bass is dynamic, very detailed, informative, clean and powerful.

You have a very attractive room, small but certainly capable of being tamed with a pair of subs and a large bass trap. A small room needs lots of absorption, a large room needs lots of diffusion and a mid sized room needs some of both.

As I mentioned in an earlier post you could use the sub as a coffee table but the photos reveal 2 obvious places that will not only not get in your way but are generally from the many installations I've done the preferred positions.

First Sub: On the left wall below the window and tucked up close to the record rack.

Second Sub: Behind the couch slap in the middle of the back wall.

The obvious place for a bass trap is horizontally on the back wall where you can accommodate a full size superchunk design. See photos below, only you would build it horizontally.

I also suggest you take 2 or 3 of those slim grey panels and fix them to the door and replace them with 4" thick broad-band absorbers. To help further, consider adding heavy drapes/curtains across the window. They can be drawn aside of course but closed when needed.

Your main speakers' bass output will naturally contribute to the chaotic bass propagating around the room and by moving them only small amounts can fine tune the resultant response. Just a couple of inches.

The lone speaker at the back can be left right where it is but you should short out its speaker terminals with some wire. This will damp cone motion from pressure waves causing the speaker to act as a microphone and driving power into the crossover then releasing that power out of phase and time with music

Having the main speakers overpowering the room is a fallacy. With the room acoustics sorted this is not an issue.

Regarding your post above, changing speakers are not going to sort out the issues you are experiencing. Prove this to yourself by plugging the ports on yor main speakers which will effectively render them as sealed boxes and have the bass response roll off earlier at 12dB/octave. This will immediately show up on REW and it costs nothing but a little of your time, it's also informative. There is no need to settle for a ragged response. In one of the photos you can see a DIY absorber that is usually 4" deep but I made these 5" deep for them to work lower in frequency. My wife said she does not want me to go 6" deep.

You can also build a ceiling cloud to suspend from the ceiling which is very effective. Use REW to check your decay times as I mentioned in a previous post. This is a scientific approach to sorting out a room's acoustic problems which each and every room suffers from regardless of shape or volume. Fact.

Start of bass trap left front corner.

Bass trap waiting for cover to be attached with velcro.

Bass Trap right front corner finished with cover on and heavy drapes visible

Yes build the traps as shown across the entire back wall. The colourful panels in the photos are DIY broad-band absorbers. Google has dozens of how to DIY examples. You need a few. And consider heavy drapes across that window.

See dimensions for bass trap construction from a previous post of mine, it's all there so no need for me to repeat. Once again google for DIY superchunk bass traps but do not go smaller than the sizes I provided. You will measure and hear the benefit and it's not small.

First off, if you want to be able to place the subs where you won’t fall over them then forget REL or any other sub that does not provide adjustable phase. REL subs only provide 0 or 180 degrees.

Let’s now look at that huge 35Hz peak caused by bass waves combining ’in phase’. Think of waves traveling towards the beach and remember how when secondary or tertiary waves catch up with those in front you get a larger wave form. That illustrates waves combining in phase, OK?  So the exact same thing is happening in your room and it’s happening at 35Hz.

What if you could magically provide an antiphase 35Hz signal? problem solved, right? Well you can do exactly that by adjusting phase, SPL, crossover frequency, crossover slope, room gain and PEQ.  You can tame the peaks and fill in the nulls. Sub number 2 will smooth things more.

Your speakers have ports so as an experiment plug them and see what happens to the response on REW and report back. There will be noticeable change,visually and audibly.

Before you spend on Dirac Live get yourself 2 x SVS SB 1000 PRO subs for about $600 each. Buy, beg or borrow. Adding subs does a lot more than just smooth the response, there is a performance gain across the spectrum.

As mentioned it’s not only SVS that can do this, many others available but the ones I suggest are IMO best value. Small compact units that also provide the remote App to allow adjustment from you armchair.

I have a 5m x 7m room opening to the kitchen and my small REL @#$$% and SVS fill my room with effortless detailed bass. The only reason I don’t have a 3rd sub is because we are going to sell the house.

I mentioned reading papers from Geddes, Toole and Welti. I strongly encourage you to google them up and read and learn from them.

Here is a plot of my room:

As you can see it looks a little bit better than yours. No 35Hz peak. The aberration between 100Hz and 250Hz is because I am not able to vary phase on the REL. The point being you will be able to get an even better in room response than mine by following my advice.

The above complies with the industry standard of +/_3dB up to the Schroeder frequency, the modal region.

Contrary to the advice above PEQ in Roon can not solve the overlong in-room decay, you need absorbers for that and PEQ does not absorb. How can it possibly know what frequencies need absorption and by how much. REW is the tool to help with that.