[jimbones]

Hi.
First off, I'd NOT use mineral fibre ceiling tiles like Armstrong. Instead, I have installed for 30 years now with great success, standard 2'x4' fibreglass ceiling tiles (cheapie stuff from any hardware stores) on T grid suspenders for my basement audio den. With only 7 feet ceiling-floor clearance!!!!! Fibreglass panel absorbs sound much much better than mineral wood & are easily removable & replaceable.

GIK diffuser panels are designed for diffusing 350Hz up to 7KHz, which should do nothing for yr bass performance.

I suspect the shape of yr basement audio room & layout of yr loudspeakers screw up the bass.
Why don't you show us the floor plan & the audio layout.

Considering my audio den low low 7 feet ceiling height, with synthetic fibre wall-to-wall carpet on rubber underlay, no nothing bass corner traps nor diffuser panels the likes acoustic control added. Yet the
pipe organ bass notes (down to 20Hz) pumped out from my 100W 10" sub clean, fast & powerful, with signal fed from my stereo tube phono-preamps playing digitally mastered vinyls.

FYI, my sub is placed just off the right corner of the front wall, about 5 ft behind my right channal KEF bookshelvers. Repeat - no conrer bass traps needed at all.

c-J

I tried to upload my layout but it is in word format generally the room is 12 x 16 w 6'10" ceiling (the room is bigger but that is the listening area. I wish i knew how to convert it to a gif, jpg to show you.

[Alex Reynolds]

The diffusors of course do not absorb low frequencies, and the ceiling tiles will not work that low either. The thicker insulation above the tiles should help though, I like the idea of doubling up the perimeter.

just curious, if I find a deal on corner traps I may buy them but I need to know one thing, are the foam traps as good as the fiberglass traps? Auralex makes corner traps (a 8 pack for a bit over 3 bills) If NG I'll stick with fiberglass.

Foam corner traps do not affect the lower bass ranges much at all. You can check the test we did comparing broadband traps to foam here: http://gikacoustics.com/comparing-foam-to-gik-244-bass-traps/

[Roc]

See my reply to the post by "Jackman" in mid may, on basically the same subject.

Attached is a picture of my custom honeycomb ceiling.


Dave.

[Hipper]

Auralex LENRDs go down to 125Hz. They also make Mega LENRDS that they claim go down below 50Hz. I had ordinary LENRDs for nine years and they did start to deteriorate a bit in that time - not disastrously so but the edges become fragile.

GIK Soffit traps definitely absorb as low as 40Hz.

If you've got measuring gear - even just test tones and a radio shack meter (you can download some test tones here: http://www.realtraps.com/test-cd.htm) you can get a good idea of what is going on in the bass region. Then you can work out what to do about it.

If you don't do that you will get some idea of possible problems based on your room dimensions. Here's a calculator: http://www.marktaw.com/recording/Acoustics/RoomModeStandingWaveCalcu.html

[JLM]

jimbones,

Going from two subs to one will definitely add to standing bass waves.  Search AC for "swarm" (3 or 4 subs).  This solution is supported by work done by Floyd E. Toole at the Canadian National Research Council (recommend reading his book 'Sound Reproduction').  Think of moving your hand length wise in a shallow bathtub.  The waves travel the length of the tub, bouncing off the ends and returning to interfere with each other, in come cases even doubling or canceling.  This is a perfect analogy to the sonic tube that all residential rooms behave as.  Now, keep in mind the size of bass waves (1130 ft/frequency, so 30 Hz is 38 ft long, etc.).  So diffusion is a dream and as mentioned above absorption is not practical.  EQ only works at a single location in the room (and so should only be considered a possible finishing touch).  That leaves two factors:  room size/shape (bigger the better, fewer multiple ratios of width, length, height the better); and multiple bass sources.

[jimbones]

OK I purchased 2 tri corner bass traps. Thay are in the corner behind the speakers. Before I installed them I played a 50hz tone and walked around the room and it was really loud in the corners behind the speakers. Is that a good start? I will probably need more and i will have to do some room testing before my next step.

[bpape]

Yes - adding some bass control in the corners of the room is a good start toward taming the decay time down low. 

Bryan

[Hipper]

Those tri-traps should have reduced some of the problem low frequencies.

The best place to measure is where your ears will be.

You can play the various test tones and hear what they sound like in your listening position - some will be loud, some less. Note this down. Do this for the range 200Hz down to 31.5Hz. You can use gridded paper with the frequencies running on the top (31.5, 40, 50, 63, 80, 100, 125, 160, 200). You then make an estimate of the loudness of each tone. I suggest you start with 200 Hz and change the volume until that sounds at a comfortable level and call that '0'. The next tone is 160Hz and if that's a bit less loud then the 200Hz tone, call that '-1', and so on. Also for each set of measurements make a note of the position of your chair. If there's one frequency that is much louder then the rest, move your ears around until you find it at a more sensible level. Doubtless at that location the other frequencies will also have changed their levels. Measure again.

It's a tedious business but you should find a location where the least damage is done to the sound. Once you find that, listen to some music and hear if you think it sounds better.


Of course moving speakers around can also affect results and you could try that too!

[jimbones]

I have Omnimic and can make plot and bass decay if that is better

[Hipper]

Yes it is. If you have a stand that would be better still.

Place it so the end is where your ears would be - some say pointing upwards, which is what I do; other say pointing towards the front.

Have you got some software like REW then?

[jimbones]

I have a stand as well. I use it when designing and measuring loudspeakers. The Omnimic comes with software and a test cd that plays all kinds of sweeps, tones, noise etc. I guess I should do a before and after. so I'll have to remove the traps temporarily.

[jimbones]

Ok so I started with 2 corner bass traps. After a listening session it is obvious that it sucked up all the extra bass in the room. So much so that I needed to slightly raised the subwoofer volume a bit. I'll listen some more abd take measurements but I am not sure additional bass treatment is needed.......yet.

[jimbones]

Another question: Before I installed the bass traps i avoided putting the subwoofer in the corner because it sounded boomy, so i relocated the sub elsewhere in the room, never acheving great bass performance.  Now that I have the bass traps it has tamed the boominess. Would it be OK to put the sub in the corner again now that the traps are installed?

[bpape]

You can try it but you're still going to maximally excite room modes with the sub in the corner.  You can try it closer to the corner certainly - free to do (one of the few things in this hobby).  As always, theory is great, actual results trump theory.

Bryan

[Hipper]

Ok so I started with 2 corner bass traps. After a listening session it is obvious that it sucked up all the extra bass in the room. So much so that I needed to slightly raised the subwoofer volume a bit. I'll listen some more abd take measurements but I am not sure additional bass treatment is needed.......yet.

My experience with bass traps in my room (13' x 14' x 8') is that you hear more bass with them installed because they take out the boomy bass. This translates as hearing deeper and a fuller range of bass notes more like the actual bass from your music. In my room I have seven soffit bass traps and I reckon I could use more if I could accommodate them (and want to pay for them of course).

What you hear will depend where in the room you listen. The key is what it sounds like at the listening position. It doesn't matter anywhere else.

I've no experience of using sub woofers.

[bpape]

My experience with bass traps in my room (13' x 14' x 8') is that you hear more bass with them installed because they take out the boomy bass. This translates as hearing deeper and a fuller range of bass notes more like the actual bass from your music. In my room I have seven soffit bass traps and I reckon I could use more if I could accommodate them (and want to pay for them of course).

What you hear will depend where in the room you listen. The key is what it sounds like at the listening position. It doesn't matter anywhere else.

I've no experience of using sub woofers.

 

Wandering about the room can help from the standpoint of identifying WHERE a specific problem may be coming from but you're right in that in the long run, only the listening position matters.

What bass absorbers do is to reduce the decay time and excessive ringing of the bass. This would normally mask low level things like imaging cues, harmonic textures, microdynamics, etc. while also causing constructive (peak) and destructive(null) interactions between the direct and the reflected sound.  The quicker you can drop the level, the less damage it can do and the tighter/punchier it will sound.

Bryan

[jimbones]

I made up a diagram of my listening room. I added in the diffusers, bass traps and absorbtion panels. The 2 bass traps are against the front 2 corners. What changes would you make? Again these speakers have an open baffle midrange.

[bpape]

It would be nice to have some diffusion behind the speakers to help widen the soundstage and deal with the rear wave comb filtering from the OB mid if you can fit something in.

Bryan

[jimbones]

It would be nice to have some diffusion behind the speakers to help widen the soundstage and deal with the rear wave comb filtering from the OB mid if you can fit something in.

Bryan

Well, there are small panels on the wall, I have 3 panels (2x2?), one in each corner and one centered (see green) I agree it could use more. What type panels would you recommend?

[bpape]

Specifically looking for a diffuser rather than an absorber behind the speakers to help widen the soundstage yet still address the comb filtering from the rear wave.  Something like this - http://gikacoustics.com/product/gik-acoustics-q7d-diffusor/

Bryan