Digital Room Correction vs Room Treatments

@lemonhaze Thanks.  It sounds good to me, filling in the lower parts of vocals quite noticeably so it goes from thinner/slightly nasal to more substantial and better balanced.

But here’s the thing: I’m having to set the SVS LPF all the way up to 200Hz.  Because I’m trying to address the original 100-200Hz null from the mains:

If I cut off where you would normally cut off with a sub, that null stays there.

Is it a total disaster that I have to overlap the sub and mains by that much to fill out the null, even if the final curves look pretty good?

@captouch, that last frequency plot you posted is a huge improvement on the one before it where you have a 20dB null. That's a lot of music that you were missing in the important 50-70Hz range.

Yes, of course the 35Hx peak is 'a room thing' so are all the other peaks and nulls/partial nulls. You don't mention what change you hear in the sound now with the one sub in place.

You wonder if a second sub is needed? Will it help more? Sure it will help more but only you can decide if you need it. Personally I wouldn't hesitate

@bugredmachine, I had computer problems and have only just resolved the issue. You have a lot of nice kit there and I had a look at your complaint about the 100Hz problem stubbornly remaining. I also noticed your REL subs.

REL unfortunately only provides 0-180 phase flip so you are limited in your ability to dial them in. It appears obvious to me that a different phase setting is required and that is only achievable with a sub that has variable phase adjustment.

My advice, and I'm sure you're not going to like it, is to get an additional sub that has variable phase. There are many on the market and if you do go for this then it should be a sealed box, not ported or with a passive radiator. You've seen me mention the little SVS SB1000 Pro. This is fun to use because you can dial it in from your listening position. It will allow you to flatten the 100Hz peak and provide a smoother response. Be prepared to move one of the REL subs if necessary. I do not get kickbacks from SVS

You have a lot of energy higher up that could be tamed with a ceiling cloud. The beauty of the cloud is it does not get in the way and it deals with the worst reflections, those from above. As I'm sure you know, the further the absorption is away from the wall (ceiling) behind it the lower in frequency it absorbs so you can by adjusting that distance fine tune it while watching the results on the frequency graph. I assume you are making measurements using REW, if so call up the Waterfall plot (cumulative spectral decay) for info on Rt60 which would be about 300ms. A smooth decay is more important than absolutes.

@goose I just bought two packs of 4 and will try them out tomorrow!

@captouch In keeping along the spring concept like Townshend, amazon has the nobsound or other spring puck like products for around $20 for four pucks.  It's an inexpensive purchase to experiment.  The Isoacoustics products are reported to be good and they have recently updated their isolation products.  I prefer the Townshend products for speakers but they are more expensive.  There are also other companies that provide de-coupling or isolation products but I don't have any experience with them.

@goose Do the Isoacoustics solutions (ISO-155 or Aperta) fit within the realm of decoupling that you suggested, or are those not really what you meant?

@goose That’s very interesting, thanks for bringing it up.

So many possible tweaks to try!

@captouch the reason for asking is that have my audio room is on a second story suspended wood floor and was experiencing a bump in the 80 to 100 hz range that was a problem.  The room has modest accoustic treatments (bass traps, first reflection and diffusion).  I tried all kinds speaker changes including spiking, no spikes, limestone platforms with and without spikes and gliders.  The key was to de-couple the speakers from the floor rather than coupling.  It improved everything in the system via Townshend podiums.  you might want to try some of the cheaper "spring" options out there to see if this may help your issues as a test. 

@goose The floor is a suspended wood subfloor finished with engineered wood planks.

The speakers are on Monoprice Monolith 24” metal stands with the four columns filled with sand.  There are spikes on the bottom of the stands sitting on protective discs to protect the wood floor from the spikes.

There are currently very thin pads on the top of the stands, but I’m about to put some thicker (but not objectively thick) silicone pads on top mostly to provide some light resistance to sliding if the speakers are bumped.

I think blu tack could mar the bottom finish, which is what I wasn’t planning on going that route and will likely do the silicone pads instead.

@captouch just curious are your speakers isolated or coupled to the floor and is it concrete or a suspended wood floor?

@captouch I don’t really feel that it is bright. I am a very analytical listener as well and like the air I get. Maybe that psyches me into a satisfaction level. My hearing is pretty decent to 14khz for an old man per the test 3 years ago.

You’ll notice that this region also attenuated 3 to 4 db just by taming the bass. At the time, new room, new speakers to me, and lots of first reflection treatments have helped the response. I’m not into tooting my own horn, but it sounds pretty awesome these days. 

Cables can have a great impact, of course, but I have no listening fatigue after spending 3 years evaluating cables and "choosing wisely" for synergy.

Happy listening.

@bugredmachine Your system seems to have a little extra energy from 1-6kHz - does it seem a bit bright to you?

I'm a firm believer that bass trapping can solve a lot of issues for little money and effort. Taming that low end helps a bunch as Eric pointed out.

My room response before and after bass traps and treatments:

https://www.audiogon.com/systems/10635#&gid=1&pid=10

That resulted in a +- 4.5 db range for my sweeps. I was told years ago that +-5 is a reasonable target for room response. If true, then I've told my pea brain to just hold tight and enjoy.

My substantial bass traps were built as large as I could fit in the front corner spaces. As many have pointed out, corner traps like @lemonhaze are using are also employed in the rear. 

All of this is in my TN systems page photos. I failed at pasting in the graph photo here.

No matter what I do or how I measure I have not eliminated the 100 hz bump. I've considered a cheap equalizer to knock it down but really don't want another device in the chain. The room is like Mother Nature. It always prevails.

Got a single SVS SB 1000 Pro and played with some of the settings.  In conjunction with the variable loudness and 5 band EQ on my McIntosh C35 (I only tweaked one band), here’s my latest frequency response curve:

It’s zoomed in a fair amount so looks pretty lumpy, but the orange lines show the +/-3dB range and red lines the +/-5dB lines, so I’m mostly within 3dB except for the 100Hz and 575Hz peaks, ignoring the 28Hz peak as I think I can deal with that with the room compensation feature on the SVS and there’s likely little source material with musical info that low anyway (with my musical library).

So not bad at all.  I’m not sure a second sub is really required, but am open to picking a second SVS up if I can find one for a good price.

@kofibaffour So if the corner wedges are 12" x 12" x 17" (hypotenuse) and as long as needed to stretch from cabinet top to ceiling or on top of a cabinet between the ceiling and back wall - this size will still be beneficial?

FYI, it's actually further back into the room that reduces the major null.  This 50-80Hz null is pretty much there with every speaker, but various in magnitude based on listening position.  So it must be a room thing, as with the 35Hz peak.

@captouch I guess physics does hold. Good that you've found out for yourself that as close to the front wall as possible is a better null reducer.

Also yes if you can DIY some corner wedges that are from corner floor to ceiling or even midpoint with this Rockwool - https://lumberbarn.com/products/rockwool-comfortbatt%C2%AE-stone-wool-insulation as the filling material.

But he's the two subwoofers are very important and you need to do the subwoofer crawl with mains when you get them

Update to the thread.  Here are 3 FR curves for my new-to-me Fritz LS7 Illuminator bookshelf speakers:

The difference in the curves are 3 different listening positions:

Red: 60" from back wall

Purple: 48" from back wall

Blue: 36" from back wall

The 35Hz peak isn't nearly as high as with the previous speakers (Monitor Audio Gold Reference 20) perhaps because the LS7's put out less quantities of bass vs the floor standing Monitors, but that 40-80Hz null is very much there and even in the "best" case at 36", it's down about 10dB from reference level.  There's another dip around 100-250Hz or so.

As mentioned earlier, I'm very open to getting two audio-focused subs like the SVS SB-1000 Pro to fill in the nulls in the bass region if that will even out the bass response.

About the super chunk bass traps for the back wall - I measured and actually only have 12" between the top of the cabinets and the ceiling - not sure if a scaled down version of that makes sense there or is necessary with the new FR curves.  I have about the same amount of room where the back wall meet the side walls, again constrained by the back cabinets.

Right now, I'm using big 26" high speakers as speaker stands, but will be getting 24" high real speaker stands tomorrow.  I haven't tried to play with speaker location, they're still located 38" from the front wall and 28" from the side walls (at the 1/5 room width and depth location).  Played with toe-in just a bit, but not a huge impact from what I could tell.

The ETC impulse peaks smoothed to 0.2ms show just one peak between 3-4ms around -14db or so, but all other peaks below -17dB.

Any thoughts are welcome as always.

As far as subjective listening impressions: They sound more forward in the upper mids/highs than the Monitors. At high volume, I want to tame them some.  This is with grills off.  With grills on, it seems to incrementally calm those forward frequencies some, but visually, I like the look without the grills much more, so will try to make adjustments as possible with grills off.

OP

Something that I would look at is your room’s reverb time and if it’s excessive, fix that first.  I have had good luck with GIK’s Polyfusor’s which defuse and reduce reverb time with a little bit of absorption.  They also look better than the rectangular absorption products IMHO.

My experience with bass traps is they are better at fixing peaks in the 60-100 Hz range.  They have to be quite substantial or use acoustic wizardly (Tube Traps) to get down to your room’s 35 Hz main resonance peak.  I would address that peak with EQ.  To avoid a digital conversion, you might consider an analog parametric EQ.  You will notice the most improvement in movie playback by reducing this peak - bass will have impact instead of going "whump."

My current configuration includes bookshelf speakers (KEF R3 Meta, Dynaudio Contour 20) and Rhythmic SE12 subwoofers.  The SE12’s include a band of analog parametric EQ.  They are servo subwoofers so they work great with music.  I am all digital these days, so I am rocking a MiniDSP SHD Studio.  Applying DIRAC correction really focuses the image in my room.  I would consider that icing on the cake after fixing reverb and bass.

Those SVS subs are pretty cool - compact, sealed, and not too expensive.

I can take some measurements with ports plugged on my current speakers, but I really want to see how the curves look with my incoming bookshelf speakers before deciding how big my issues are on a baseline level as well as how much they it can be improved by tweaking LP and speaker location.

Meanwhile, I’ll do some homework to figure out how to build those superchunk traps.

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.

BTW - if you are a ROON or JRiver user then Mitch's Convolution Filters are easy to use.

Honestly too hard and too much.  Simple parametric EQs  in Roon will solve the OP's problems.

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.

@lemonhaze Great suggestions, thanks so much!  
 

I’m assuming modest sized sealed subs would do for a room like mine.  I see REL subs favored by a lot of audio people.  Is this what you’d recommend?

Whay type of fill do you use for your triangular traps?  And you’re saying build it horizontally and put it above my wall cabinets across the entire back wall at the interface between wall and ceiling?   And you’d go as thick as I could go, up to and including 6” if I can swing it?

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

I have implemented DiracLive three times, on both sides of my basement, and in my living room.  The sound improved in all cases.  But, I think optimizing the speaker placement and/or LP (and possibly room treatment?) before using DiracLive will get the best results.  

One element that should be considered is bias towards your current (non-corrected) sound.  I would live and test the room corrected EQ for a little while before making any conclusions.  

The cost of MiniDSP + DiracLive is not large relative to your total system cost or cost of room treatments.  IMHO, best bang for buck I could ever spend.  True, tactile improvements in sound that could not be achieved with upgrades to components, cables, or recording type.  One could argue that DSP also corrects defects in speaker response (frequency and phase).  Sorry for sounding like a salesman, but this stuff has really changed my perception of what good sound is and how to achieve it.

Just curious, what elements of sound reproduction can DSP not correct?  We often hear that room modes cannot be corrected since they are a function of how the sound interacts with the room after leaving the speakers.  I would not be so fast in making that assertion.  By modulating the phase of the individual channels separately, should it not be possible to also correct, at least to some degree, constructive and destructive interference?  I believe this is what DiracLive is capable of, but to be honest I am not sure since they are a little vague in describing how it works exactly.  I would love to hear from someone with more technical knowledge on how DiracLive works.

@mswale I think if I wanted to move my sub around to cancel the nulls, which I think is a good idea and ideal, I’d want to get a smaller sub.  The SVS was from my old HT system in a bigger space, and while no problem to reuse for HT in my new smaller space since the AVR will use Audessey to adjust level, it’s not an ideal sub for music.  

I don’t notice the dip or that anything is lacking, but it’s probably one of those things where you don’t know until you hear the alternative.

But as mentioned above, I’m going to try bookshelf speakers first before getting a new sub or committing to room treatments or digital room correction.  The Monitor Audios that I’m using now are spec’d down to 30Hz.  The new bookshelf speakers are spec’d down to 38Hz.  So they’re bound to create less of a 35Hz peak if they’re already down 5db or more at that frequency.  At least I think.

When I measured my friend’s Electa Amator II’s, which are spec’d at 35Hz or so, there was still a peak, but much lower in magnitude.  I’m sure I’ll still have the 60Hz dip and 180Hz dip tradeoff to some extent, but the overall balance of the FR curve may give me more speaker placement and LP options to help me find a better balance.

@atp001 I’m curious about trying something like Dirac Live - the price for entry just comes at a hefty price tag and the input I’ve received from this and other forums is that it could help in some aspects, but can’t help in others.  I think I’ll wait until measure and listen to my new bookshelves and see where I am after that.

It was suggested I try the trial period of Dirac Live, I just need to figure out which EQ software also has a trial period that will allow me to use it with their software and target curves.  I haven’t had the time to do that yet.

In my experience, room correction with DSP (MiniDSP+DiracLive) made a huge difference.  In terms of sound, it went from fatiguing to blissful.  The bass became more coherent, the mids and highs less muddy, more clear.  Instruments and voices became separated, imaging dramatically improved.  DSP is not simply about correcting issues with frequency response.  As previously mentioned, time domain problems can also be corrected, which I assume is why the imaging has improved so much.  

Below is my frequency response, measured with REW.  Yellow is with DiracLive turned on.

And here are the impulse responses as measured with REW, before and after correction with DIracLive.

My perception is that the magic comes with both the frequency and phase corrections that come with DiracLive implementation.

Before MiniDSP, my room was treated with some absorption panels, mostly to reduce some of the reflective wall surfaces to improve reverb.  The room includes a 77" TV, couch, furniture, large and dense wool carpet, and sits in the basement where two of my walls are concrete covered in sheetrock and insulation.  Speakers ('bookshelf') are 5 feet from the front wall, about 3 feet from the side wall (right, concrete, a little more open on the left side).

@captouch that looks like a great music room. Think I understand better at what is going on. Everything looks a bit compressed, and yes, the room is filled. 

You might have a lot of speaker/power for that room, but that's ok. Had a thought, if you can get a wireless connection to your sub, find the room nulls, put the sub in the nulls, it might cancel out the room null. 

On the other hand, with your gear and that room, do you even notice the dip? Is it deep bass heavy? Do you feel the room is dead or alive? As most of us have realized, measurements don't always mean much to our ears. If it sounds good to you, then it's good. 

This is part of the reason why I don't want to measure my room. It's all analog (sans streamer), Done all the old school things, and it sounds good to me, so it is good. 

So it's worth using the AM Acoustics simulator to see where your room modes are, but one possible solution would be to run soffit traps actually in the soffits.  If the modes are vertically in the corners though you'll want to put them to the side of the TV. 

Ok, I need to add one more important thing.  In the past couple of days, I’ve decided to at least try bookshelf speakers in place of the Monitor Audio Gold 20’s.

Part of this is because I am wondering if the Monitors are still too big for the room and the bass output qty is still too much.  And part of this is just me being curious about whether bookshelf speakers can satisfy me as main speakers - I’ve been resistant to this in the past because I’ve always seen bookshelf speakers as “too small”.

But the reality is my room and free volume in this room is also small, so a bookshelf may be the most appropriate sized speaker for my situation.

While it’s by no means a given I’ll like the bookshelves and that they’ll become my main speakers over the Monitors, it’s very possible.  I anticipate the FR curve and overall interaction between a different speaker and my room will be different as well so wanted to give the thread a heads up so I’m not exercising people to help me find a solution for a problem that may possibly change.

Sorry for the possible distortion in the pics.  They’re 1.33:1 aspect ratio and I’ve tried to plug in the numbers to preserve the right proportions, but it posts them distorted once I actually post and view in portrait mode on my phone.  When I turn my phone into landscape mode, the pics look like right and undistorted.

I’ve posted pics of my room in other threads w.r.t. other questions/topics, but it might be helpful to show what I’m dealing with here.

Front of room:

Right side of room with entry door in middle of wall:

Back of room:

Left side of room:

I can remove things like the single speaker in the back, the beverage fridge, as well as the “side table” to the left of the chair.  But all the record racks and wall cabinets for CDs are my media storage and have to remain in the room.  The front cabinets both hold gear (active and spare) and I really prefer not to replace them.

So it’s a crowded room filled with “stuff”.  The sub is currently within 6” of the back wall firing toward the left wall is the room with records in rack about 42” away.  The speaker front baffles are about 3ft from the front wall and near the cabinets, which prevents the inside doors from swinging open without moving the speakers.  Which is fine, I can deal with that.

But my options for placing a sub are limited to the remaining periphery of the room, which means to the right of the record rack on the left wall near the window, anywhere on the back wall, or I could use it as a side table in place of the 1x2 cubby I’m currently using as a side table.  I suppose also on the front of the room between the main speakers as well.

I’m already somewhat having to step around things in certain places to access the records.  I’d prefer not to place the sub somewhere in the middle of the room and have something else to step around.

So this is what I’m working with. No complaints as I’m trying to do a lot with this room and the agreement with my wife was to store all my media and audio gear in my room to avoid clutter in the rest of the house.

But there are somewhat limited options left for placing the existing sub or adding a second one.

Sorry for contributing only infrequently.

A point that I may not have properly addressed earlier is that the benefit of a sub in a situation like this is not it’s bass output but the ability to move it to an ideal location.  However if you are severely space constrained, then a sub is almost useless. 

TO place the sub you’d put the sub in your listening location, then move the mic around potential locations until you find the best measuring place.  That’s where you put your sub.

My earlier advice to clip the peaks and lift up the entire bass region still stands.

If you can’t do this and your sub is generally where your main speakers are there’s no point.

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.

The 35Hz spike is there regardless of speaker placement and LP - varies a tiny bit in magnitude, but not much.  Room is 11.5’ wide by 15.5’ long and 8’ high.  Probably a characteristic of the room.

The 60Hz dip can be filled in at the expense of creating a more shallow one around 180Hz.

The speakers are places 1/5 of the room length from the front wall and 1/5 of room width from the side walls.  It was recommended to place the LP about 1/3 room length from back wall (60”), but I found I preferred my LP 54” from the back wall.

No tone controls active.  I’m using Pure Direct mode on my AVR to bypass the Audessey room correction.  I’m only using the AVR for the sweeps because it can accept the HDMI from my MacBook.  Normally, I use a McIntosh C35 preamp that has a 5-band EQ, but I normally listen flat.  Sometimes with a small bit of loudness contour, but mostly flat.

You got a few issues going on. Think you have a couple nulls going on.

The bass energy spike 30-40 is huge, then that massive hole at 50-80. Some peaks in the middle, with treble dropping off.

This tells me you have a boomy setup, with bright mids, and low highs. DSP will not fix this, just adjust. Don't think you can room treatment out of this.

Your speakers are in the wrong spot, or your listening spot is totally off. Think you should move the speakers around. It looks like the walls are enhancing the low bass, nulling out the mid-bass, the room appears to "dark" already with the highs. Maybe remove a couple of panels, or move them around the room. 

Do you have any tones controls active? Turn them all off, if you are taking readings, then adjust them after the readings.

The issue is I have very limited adjustments on my sub.  See pic below:

So I can adjust phase and level, but nothing else.

I was also having some issues getting REW to output to mains and sub at the same time.  So when I played with phase using sub output only, it didn’t change anything because I think it’s the phase interaction with the mains that will cause different responses to the FR curve.  Just changing phase if the sub is the only thing playing the frequency does nothing to change the FR curve.

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.

Question for the group here.  I tried, just for learning purposes, to use my SVS sub to see if it would help fill in that 60Hz dip.  Here’s the FR curve.  While it did fill in the 60Hz dip, it blew up the 35Hz peak more.

The phase is set to 90 degrees on a variable dial that goes 0 to 180.  My question: would playing with phase at all help this curve?

And a more general question, what is causing this 60Hz dip? Cancellation of sound waves at 60Hz, right?  Theoretically, if I put big bass traps in the back corners of the room, does that solve this issue as well as potentially the 35Hz and 100Hz peaks?  Or is it not that simple?

@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. 

@captouch oh then I guess you gotta use the best fit that gives the least dip in the below 60Hz region. I thought it was just the front wall bare behind your speakers

@kofibaffour while the front baffles are 37” from the front wall, I have cabinets in the front that gear is set on/in.  So there’s very little space between cabinet front and speaker back as seen in pic.

This means I can only open one side of cabinet without moving the speaker, which I’m okay with as I don’t have frequently used items in there.

But it’s pretty much a non-starter to move these cabinets off the front wall as there’s no other place to put them in the room and I need the storage space.

@captouch have you tried as close to the front wall as possible to see how that looks? Close enough that your speaker cables may touch the wall but not be deformed

@lemonhaze Here's an alternate FR curve at 48" (bolded line) vs 60" (which was what was previously recommended to me as best of my alternatives).

48" reduces the 60Hz -11.5dB dip to -4.5dB, but the 180Hz dip is increased from -1dB to -3dB, a 300Hz +3dB peak is created, and 550Hz goes from +3dB to +5dB.

Overall, 48" seems a little more peaky, but the benefit is filling in that 60Hz trough pretty substantially.

Overall, if you did this ONLY with EQ, I'd flatten the 35Hz and 95 Hz first, and then raise the entire level bellow 150 Hz to taste. 

Bass traps are a good idea, but may be too expensive.   Adding a subwoofer in the right location, with the low pass filter set high could also help.  May take some experimentation, adds more hardware and of course, is expensive too.

OP:

Turnimg off smoothing and gating, of any, is pnly useful as a learning exercise.  I wanted you to see hpw much filtering was being done for you and why this measurement only answers part of ypur question.

The link I posted to GIK acoustics will send you on your journey

@erik_squires Thanks for spending the time to thoroughly explain those issues.  I can easily turn off smoothing, but at some point, the curves get so crazily jagged (with no smoothing), that I'm not sure what I'm supposed to take from it.

I haven't figured out how to turn off gating yet.  Trying to research that now.

@lemonhaze Thanks for your input.  When you say "some absorption", do you mean bass traps?  If so, are there more economical solutions than the $500/bass trap solutions from GIK?

Yes, with minimal treatment of the room, there's a definite tradeoff between dips at 58Hz and 180Hz.  If I move my LP so the 58Hz dip fills in a lot, it creates a smaller dip at 180Hz.  You can see that 5 posts above in the 60" LP vs 45" LP.  

I do see that 35Hz peak in the many of the plots posted by other people in different rooms, so that one seems common.  The other ones seem more variable and a matter of trade offs.

In a room my size and filled up with record, CD, and gear cabinets as much as it is, I think it's honestly unrealistic to entertain getting two new non-ported subs.  I understand there's a proper way to do things, but I think the question for me is what gets me close enough or good enough to live with while still keeping my room as usable as possible.  

Because if getting things closer to ideal requires my stepping around subs or having to contort to access my media because a sub is blocking clear access to a rack, then it's going to be a daily irritation.  Not sure I mentioned above, but this room is also a TV room with Atmos in-wall/in-ceiling speakers, so I'm admittedly trying to do a lot with the room and one of the consequences of that may be I'm not going to be able to do things as ideally as a pure 2-ch listening room.

I do have a single HT sub (SVS 10" ported sub) and I could dual purpose that if it would help.  It does have a phase dial.  Since I'm using older gear, I'm going to need to sum my stereo signal to mono and then route it to my sub (no speaker level inputs on my sub, just a single RCA).  I could play around with that and if I see the potential, maybe I start to think about how to move some things out of the room and consider a couple of ported subs.

But the room just isn't all that big to begin with unfortunately.

All that being said, I am open to room treatments, preferably beginning with ones that are highest bang-for-buck and seeing how much that improves things before going too far down the rabbit hole and diminishing returns.

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.

OP:

It occurs to me you are using gating and smoothing.  Turn those off and re-examine your measurements.  I think you can re-use what you've already captured. You'll see a much nastier image of your results.

Also, when comparing speakers, it's very much worth measuring off-axis to see how good of a sweet-spot they would provide.  Speakers that measure similarly on-axis may be crap off.