sub placement problems

[Tomato]

I am having issues with my sub placement. I understand that I might be out of luck and will have to make do with what I have but wanted to run this by and see if anyone had any suggestions.
The only space I have available is a corner of 22" by 22", problem is that due to the shape of my living room I dont have much option on where my couch goes and I believe I am in a null. Everywhere else in the room, or house for that matter, you can hear the bass rather well. I wish I could move the sub but WAF and toddler is prohibiting. I tried raising the sub off the ground to see if it would change anything using scrap wood. That seemed to help just a little but not enough. Eventually I would love to do a Sonotube Sub but I fear that it would be in the same predicament.
Any suggestions?

[5th element]

Corners tend to be the best place to put subs so you're on the right path with that. When you say you're sitting in a null, what you really mean is that you're probably sitting in a null for one specific band of frequencies. The best way to solve this kind of thing is to get another sub and to position it elsewhere to fill in the null. If you move the sub to give you better bass in one position you are obviously going to make it worse in another. If you can measure and find out where in frequency the null occurs, then you will be better primed for fixing the issue.

I say the last thing above because the second sub, by no means, has to be a large thing. If you're problem is occurring at around 40Hz, then you don't need any more extension than is required to fill in the gap. A simple, small sub built around one of tang bands 8" sub drivers might be all that's necessary. Certainly having one main sub, that gives you really deep bass, in the front corner + a couple of small, well placed, subs with much less extension to fill in the gaps, is the way to go if you can accommodate them.

[Tomato]

Thank you for your reply 5th
I understand completly what you mean about the frequency null, after I finish my surrounds I should save up for measuring devices. Should be better to have in the long run.

(The Nano Neos are for a different room)

[Tomato]

So thinking about what I could do about another sub placement, just playing around. I know most people put subs low towards the ground mostly because of the size of the subs themselfs but if I do use a 8" in a smaller enclosure would sticking up ontop of a shelf cause any issues accoustically? An 8" sealed enclosure should be fairly small just need more power I suppose.

[5th element]

There's no issue with doing that at all Unless it makes the thing it's placed on rattle!

[JonMarsh]

The unfortunate thing is, you have placed the sub in a quite optimum position, so if you're getting issues with your couch and listening position, it's most likely that which needs to be changed! In the old days I'd fire up a PC program RPG acoustics developed which allows one to analyze and optimize both the speaker and listening position characteristic for a given set of room dimensions and some boundaries for placement. If you could get a cheap measurement microphone and some freeware software like ARTA, it might be illustrative to do limited range sweep measurements of your sub (say, 20 or 30 Hz to 100 or 200 Hz) in a variety of positions in the room near your acceptable listening position. Might be very educational...

[Tomato]

Thank you for the ideas they are most helpful. I have been going design crazy trying to figure out what can I do with the most bang for buck. I know I should really get a mic but this has been a lot of fun for me.
Going the 8" route does seem mighty enticing but I did not like the look of the sealed specs, not saying they are bad just was not for me. This is a design around the Infinity ref 860 which seems to get fairly good reviews and not costing an arm and a leg. Took me many hours to learn it but I think I got it down.

Going that route I would have to buy the driver and the wood. Just playing around I decided to design a box around a car audio driver I already have. Even though its not as efficient and huge! it actually gives me a little more flexibility on room placement because it is down firing. It also has the added advantage of being a box specifically designed around the driver and not just thrown in as a replacement because the original driver needs a replacement surround ops:

I am still learning a lot every day and I appreciate the feedback that I have received, thank you!

[Tomato]

Cool news I found a mic, not the best but I can afford it ... well maybe, it has ballanced outputs so need to do a little more research.

[kevinm]

Have you looked into the Dayton Audio USB mic on Parts Express? It's fairly affordable!

[Tomato]

Thank you I am very interested in that one after looking at it. I will have a talk with the Boss to see if its do able, maybe need to sweeten up the deal a little bit.

[kevinm]

I usually go with googly eyes and an "I love you."

If that doesn't work....the fallback: food.

[5th element]

I like the designs

[Tomato]

Thank you it seriously took me a long time to wrap my head around some concepts but I do belive I have it now. Doing alot of research on mic's and eq software and I cannot wait until I get one. Dont know what I will do once I get it thought, it will help me level my speakers for sure but I think I am very limited on what I can do to fully take advantage of it. I am looking forward to the learning aspect, I love learning new things

[Tomato]

Cool news, cleaning out my garage last night and found another sub, infact the exact sub I modeled for . Back in my youngin years I had 3 of them in my car, I know better now lol. Still have one in my car but I for sure go for more clarity than flat out loud super spl bass. I had thought I sold this one so yay! I get to play with two of them (no idea on how im going to power it but hey, I'll worry about that later). I hope that this will help with my bass problem, but I guess that will bring up another problem when my wife see's two of these things in our living room :P

[PMazz]

Just for fun I would try to raise the corner sub 1/3rd of ceiling height up off the floor. You may lose some overall output but may even out some freqs.

Do you at least have a SPL meter? If so, d/l a LF slow sweep and have a listen at you seating position with the meter.

[madmac]

I believe putting a sub in the corner of a room is a mistake. All rooms will have a bass 'spike' at a certain frequency range and a corner placement will only exaggerate that spike. My Infinity's use a RABOS system (Room adaptive bass optimization system) whereby with a test disc and an SPL meter, you can plot a low frequency graph of your room from your listening position, find the spike, and then EQ that spike down so you get a nice, relatively flat low frequency response. All I can tell you is that the results are striking to say the least. Does your sub offer any EQ'ing controls on the back?.

[Juhazi]

A speaker placement simulator here www.hunecke.de You can move speakers and mic in 3D

[Tomato]

Wow thanks for the help everyone. The biggest problem for me is WAF. Lets just say its a rather high standard, so I only have one place for my sub without issue and thats the corner. Me building the second sub is a huge gamble but we will see what happens :roll:
I do plan on getting a SPL meter but do not have one yet, in a few weeks I should have a mic and a meter. I have a friend who owes me a favor so Im getting some plywood out of him to make the subs. This will be a very slow project but it will get done.
I am interested in raising the sub 1/3 up the wall lol, I can do that when she goes out for an hour or two. I am rather curious on the results on just ear listening.

[madmac]

Hey Tomato!!! You can get a great SPL meter right on your cell phone. On my Android, it's call "Sound meter" and it works really well and is VERY accurate. Not sure if Apple has a similar app.

[Tomato]

Ha! well what do you know, now I have a SPL meter :P. Thanks for the tip! Seems people have tested it against real ones and its within 1-2 db which should be fine by me. I will see if I can run simple sweeps and see if I can target frequency range to see what is missing. What I might do is test my sub in my driveway to see if its my actual sub causing the issue because it very well may be the issue. I will start testing to see what I can do and expirement!

[PMazz]

I use FrequenSee for quick and dirty. Works better on my tablet than phone but will give you some insight as to what freqs are giving you trouble.

[Tomato]

So I made a cd of 10hz to 100hz and to be honest I should have done this in the first place. Playing each hz at a time I stood by the sub and from 30-90 no problem. I did the same sweep sitting on my couch and pretty much the entire 40's are gone . Its quite interesting to me, I can pretty much draw a circle on the ground of where the null is so its rather easy to sit outside that area. The problem is that the null is right in prime sitting position (of course it would be). I guess I do need to subs :W

[cjd]

Can you put a low profile sub under the couch?

Depending on the couch frame, there may be a surprising amount of space available. I have a 12x12x30 (with amp in-box) tuned to about 22Hz using a 10" Dayton RSS265HO (not quite as fine quality as the HF variant at higher frequencies, but I'm not using it high...) Would be a pretty easy volume to adapt to a box that barely has height enough to clear the magnet, but if that's too tall there are some decent very low profile drivers out there - and if the 40's is the problem, that's standard woofer territory with comfort...

Move things around to see what solutions can solve your issue - then approach how to solve it AND maintain WAF.

For whatever reason I had completely forgotten I need to do some sweeps at my new place, so I appreciate the timely reminder. I'm lucky on the WAF side of things, though the sub will almost surely be invisible to all but the most seasoned hobbiest (unless that placement is horrible...)

C

[madmac]

Yep......the 40hz range is where most sub problems reside. Glad you found the problem!

[jim1961]

So I made a cd of 10hz to 100hz and to be honest I should have done this in the first place. Playing each hz at a time I stood by the sub and from 30-90 no problem. I did the same sweep sitting on my couch and pretty much the entire 40's are gone . Its quite interesting to me, I can pretty much draw a circle on the ground of where the null is so its rather easy to sit outside that area. The problem is that the null is right in prime sitting position (of course it would be). I guess I do need to subs :W

(1/24th octave smoothing applied)

My mains (black) are quite capable of good response below 45hz, but the room null starts there and down to about 30hz. Sub1 (blue) primarily I use to fill the gap so speak. Sub2 (purple) for just a tad more smoothing resulting in the composite or overall graph (green).

These are all measurements at the listening position.

Just my story and antidote to something similar as you describe.

[5th element]

I would say that in most standard sized rooms that 40Hz is probably where the last main room mode is. Excite it in the wrong way and you get booming bass, get a null there and get nothing ;/

[Tomato]

Many moons have passed and I finally got a sheet of plywood.... for free! Well I worked for a friend and he paid me in plywood. I decided to go with the second plan above due to cost. This will have to be a super cheap build due to school and work and school cutting into my work hours but hey! It will be good.
Drew up super complex plans!

cut some wood

started to put it together


Threw kid in

So its considerably bigger than that cube I have currently. I had to make a small adjustment on the port though, apparently 6" pvc pipe in my area is only available in 10ft sections at $45 and when I only need 20" of it I opted to go a smaller diameter. Adjusted the port in Winisd and using a 4" id port I just need 7 5/8" and I was able to get a 2ft section for $8. Much better on wallet. More to come!

[kevinm]

Looking pretty good! Do you have any plans for bracing?

[fbov]

Sorry for chiming in late, but I haven't seen these questions...

The room is 22x22x~8 with flat ceilings?

Any large openings, like doorways without doors, large windows, etc.?

What the construction, i.e. cinderblocks like a basement or stick construction (2x4/2x6 and sheetrock) like most above ground construction?

I see a fireplace; anything else change the room shape (fireplaces usually intrude a foot or two, which can be good or bad.

The odd thing is that you report a null around 45Hz, which is expected in the middle of a 12.5" length. The 22' room dimension would cause a null at 25Hz... my room is 22' long but has no null due to some of the things I asked about.

Background
- Speed of sound is 1130 ft/sec, and is equal to frequency x wavelength.
- Standing waves occur at half integer multiples of wavelengths that are equal to room dimensions.
- Room size determines resonance wavelenght, speed of sound determines its frequncy.
At 22', 1130/22 = 51.4Hz, so fundamental is 25.7Hz. For 40Hz null, 1130/40= 25' wavelength, so half wave is 12.5' wall separate.

You seem like you're good with self study; this is just the start. Tell us more about your room, and its acoustic features, and perhaps there are some obvious options that haven't been considered as yet. While corner placement is very efficient for SPL, it excites all room modes. That has downsides, as others have noted, but the solution is not always adding subs! There are other options I can't suggest due to ignorance of your situation, and every situation is unique!

HAve fun,
Frank

[Tomato]

In reply to Kevinm - Yes there will be bracing but im not going overkill, just some simple wall to wall bracing that I fabed up. There maybe only 100w going to this thing and not going for super duper quality but it should be better than what I am currently using.

In reply to Fbov - I think the best way to tell you about my living room is to take pictures, there are so many crazy things about it, it would be a book to explain. I can say that its a vaulted ceiling open to a hallway, dinning room, kitchen with a 4 foot wall dividing the living from the dinning and kitchen. I will take measurements of the room dimensions and take pictures tonight. Should help understand the crazy 70's layout. :P I really really appreciate your input. I am limited not only on money but WAF lol so that brings in a very unique challenge as well.

[Tomato]

Forgot I had these, was looking for pictures of my living room

home made circle jig, because cheap!

test fit, it looks a little loose in the picture but I made the circle 1mm smaller and its a perfect fit, I had to hammer it home when it was done.

my router with the home made circle jig was just shy of going all the way throught the 3/4" ply so I just decided to drill a bunch of holes and chisle/hammer it out. Hindsight I should have just pulled the bit out just a wee bit to go through but sanding took care of the tear out, and oh boy was there tear out ops:


here is the car audio sub just layed in for a fit. It just needs a bit more sanding and it will be perfect. For this sub I am not going to double baffle or anything, again I just dont think its worth it in this situation. Also you can see some bracing in place, there is more but I ran out of wood glue.
So a quick tally for cost for this build:
7.99 for 2ft section of 4" pvc
8.99 for router bit
19.99 for clamps
$? for wood glue
that should be it. This is only the cost of items that I had to directly buy for this build, I had everything else so thats cool

[kevinm]

Can't argue with those prices! I'd add some lining to the walls - at least in my experience it helped. To my ears, it sound something along the lines of "cleaner, less boomy."

[Tomato]

Like more wood or poly fill'ish stuff?

[Tomato]

Here are some pictures of my living area ( sorry for the poor quality ) and I totally forogot to get measurements.
This is a picture from the hallway, you can see the half wall and there are skylights above the couches


This is just a more detailed looke at the living area, it is a drop down ( wahoo :cry living room with terrible fake hard flooring
also that black bookshelf in the back was the original idea to put a small sub up top



And here is my tiny dining and amazingly small kitchen everything hard laminat flooring. But not bad for a first home and surley not bad for one under 100k



so for sure there are alot of reflections and I dont know how much I can do about them but any suggestions would be appreciated.

[kevinm]

Just fiberglass or open celled foam on the walls. I wouldn't recommend stuffing, but just something absorptive on the walls.

[Tomato]

So close I can almost hear it.
I didnt know what to do for legs so I played around and came up with this solution. looking back at it I should have made it bigger but this will support it no problem. I cut a few strips of ply



Then I attached like so ( this is where I would have made it bigger, the shorter pieces should be wider so I could screw from the other side, not much lateral movement so it shouldnt be that big of a deal)



all four made up



and then glued and nailed



Just need to finish sealing and stuff ( should have stuffed while one end was opened ) and then wired up! I cant wait!

[Tomato]

Just saw you post about fiberglass, I like that idea alot more than pillows, I think it will be easier to put in place!

[kevinm]

Definitely. In my tests (subjective, using my ears), the pillows didn't do anything positive. I could hear the difference, but it was marginal and I felt like I was losing spl because there was top much added vlume.

Fiberglass sounded more controlled, deep without spl reduction.

[fbov]

As expected, you have a complex room with a mix of highly reflective and highly absorptive elements.

Screen axis (assuming a flat wall behind you) is "stepped" by the back wall in the dining area, so you should expect room modes supported by both dimensions. It's a small step, so these modes will blend together

Cross axis is worse than stepped, it's divided; the half wall will reflect off both the side wall and the dining area wall, as well as the full-width reflection above the half wall, and an even longer path through the kitchen, that could add some room resonance itself. Expect modes based on each segment, low living, low dining, combined and kitchen. There's also a strong asymmetry in the side wall; the fireplace reflects sound very well, while the glass doors are a true bass trap, allowing bass through but reflecting higher frequencies. Vertical blinds help damp the higher frequency reflections.

Vertical axis has no single distance due to the tilted ceiling. As for the step, the effect is to broaden resonance peaks.

Walls, floor and ceiling are basically bare, save for the seating area around the fireplace. I would expect this room is too bright for comfortable conversation... have you done a "clap" test? Clap your hands once, very loudly, standing in the middle of the room and listen to the decay. The clap should die so fast it's hard to sense, but I expect you'll hear it continue for a second or so.

Your area rug and couches (fabric upholstery I assume?) are the main room treatments above bass, with the glass door and couches helping damp the bass range.

If that's an accurate description...

Try generating a little WAF by starting with the "clap" test and conversational needs. Higher frequencies are easily treated with panels, and panel appearance has a lot of artistic options that may appeal to her tastes, as well as making the room easier to live in. If she's willing, the obvious locations are the front and rear walls, above child level, and the dining area. You'll be amazed how much easier it is to talk in a properly treated room! Hang them like art - center of the wall with lots of space around them, perhaps offsetting opposing walls. Don't crowd them unless there's opposition to spreading them out.

As to your issue with the 40's, 40Hz is 14' and 50Hz is 11' half wavelengths. That looks about right for the ceiling, but... there are a lot of walls that are close to this distance or an integer multiple. I can only suggest repeating your test that identified this frequency range as a null, but varying things like doors, open/closed, especially the glass door. See if you can find the resonance that's driving the null. Then we can talk about sub locations that would minimize that resonance. It could be as simple as moving the sub under the display, but I hesitate to recommend anything in the absence of more information. I see lots of opportunity, waiting on a need.

Hope this helps,
Frank

[Tomato]

Oh wow thank you so much for your input, I wish I read this last night so I could have tried the clap test! This is incredibly detailed and I really appreciate the time you put into it. I bet I could talk my wife into at least trying wall treatments that look nice, artsy is the poper term to use for her :P. If she doesnt like them I could just store them away until its time for a good proper movie watching or music listen. I initially was trying to design a sub that fit under our entertainment system but it was proving to be a bigger challenge for me having only 6" tall and about 13" and probly 6-7' of length. maybe I should try that in the future. Better yet when I finish my cabinetry classes I could just designe an entertainment center with a sub included underneath. That would be the best senario.

I couldnt take it anylonger, so I decided to just do a test just see if anything I was doing was good, so what does any sensible person do? Hook it up to thier car! (this was by far the easiest to do, due to location and ease at getting to my amp)



to which my son thought it was a trashcan and tried to thow away some trash



which is good....I suppose :lol:

This wasnt finished being sealed and no stuffing at all, but I can say that it sounded rather well. I could for sure see in the future or if I ever did this again to use a double layer of walls. I think thats the best thing that I could do for it. Other than that I am very pleased and cannot wait until its finished!

[Tomato]

So I did a simple clap test and I found it interesting. The only decay that I could really notice came from the hallway, there was some that I could discern but probably all over but the hallway was the largest audible source. I guess that since its just a box with hard floors and parallel sides it makes sense. I am scared to even mention wall treatment to my wife ops: lol but I will see what kind of coaxing I can do, probably will be turned down but cant hurt to try

So stuffing, I could not find any friend or anyone with a little insulation that I could source, but I do have a body pillow and a regular pillow that I could use. So I went that route, only because free. Having messed with pink insulation alot over the years I tried to think about how dense it is and the quality of the fibers, with that in mind I tore chunks out of the pillows and just threw it in. I used up both the pilows and it filled 3/4 the way full which I think its perfect. I just gave it a small amount of packing. My theory of using chunks of pillow it wont fall out of the port. Getting pushed out is another story I will worry about later :P



so this is the orginal sub where I just threw in a random car sub. I took the sub and the plate amp off of it, the new box is specifically designed for the sub. I used the plate amp and I knew it would be sufficent for my needs.



and Bam! its new home.



To give a quick difference of sound: The small cube is like a sorbet, the big box like a custard. While they are both sweet the sorbet is sharp and leaves a tang in your mouth but the custard so silky smooth and leaves your mouth wanting more. Sure it can get loud but the whole point of this adventure was to build something for quality. Designed for a purpose of cleaning up the sound. Learned a few lessons for my next one (hey I still have 2 more subs) and will for sure build it better. Just now need to get a mic with proper software, wall treatment, proper amp for sub(s) and finish up my surrounds and I think I will be good for a while

[fbov]

Nice pics... and so lots of comments. And no issues with workmanship; nice looking sub!

1) you've misunderstood the interior treatment of ported boxes. .
- line the walls, leaving the resonant cavity open. You've shown how to stuff a sealed box...
- make sure there's nothing near the port mouth, for at least 1 port diameter in all directions. You can stuff around the port, just not near the mouth or the driver.

The idea is to absorb any frequencies above ~80-100Hz inside the box, as they're likely harmonic distortion, while allowing the box to resonate at the tuning frequency, say 30Hz. Think in terms of the box breathing, inhaling and exhaling, 30 times/second. The bigger the flow, the louder the port, so avoid anything that messes with air flow. That's one big reason for flaring port ends. Yours could use a roundover bit run around the inside of the port mouth, the bigger the better.

2) Subwoofers need to be well coupled to the room.
Yours isn't. Stuffing differences aside, did it sound different outside being driven by the car amp? Think in terms of pressure waves coming off the bottom of the box. Where does the air go? Three of four sides are walls, forcing it straight up, and effectively adding a randomly varying horn loading to the mouth of the sub. This should tend to favor lower frequencies, and may be a factor in smoothing the response, but the LF response is already muted due to port blockage. I'm not saying this is a bad thing, per se, but rather hope to make such things choices, rather than outcomes.

3) Clap test will vary with your location
The classic location for "flutter echos" is stairways, where you have wide expanse of bare, parallel walls. Hallways are similar. The key is that the main listening room has reasonable decay, which most furnished rooms will. That said, the difference between, say, 0.5 sec for a 40dB decay and 0.25 sec, is not gong to be evident in a clap test, but you'd notice if it were a second or more... it finds the really bad, not the marginal. You now know you're not really bad, but it'll take measurements to find what could be improved, if anything. I've done no room treatment, and spent years figuring out why not... and found I had treated the room by furnishing it, although base construction methods helped a lot (stick construction, not cinderblocks).

HAve fun,
Frank