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General HIFI => Room Treatments & Tweaks => Topic started by: tuyen on August 22, 2012, 12:35:58 PM

Title: bass traps for corners
Post by: tuyen on August 22, 2012, 12:35:58 PM
Hi all,

I'm looking corner bass traps of some sort to fit around the 4 corners of my room.   What do you guys recommend or use?

Cheers,
Tuyen
Title: Re: bass traps for corners
Post by: vitavoxdude on August 22, 2012, 12:58:47 PM
G'day Mr. T  ;D

Chez Willow uses some rockwool cut into triangles and stacked floor to ceiling in each corner and this definately helps with the boom boom.

Lot's of data out there on hermoltz resonator panels and some interesting stuff from the BBC London research department.

Carefull you don't kill off the room altogether by over treating it as it robs the music of vitality IMV.
Title: Re: bass traps for corners
Post by: tuyen on August 22, 2012, 01:09:29 PM
Hi V,

Cheers for the reply.  I need to try me some of that!  I'm getting room boom on heavy tracks when listening at high spls.   I'm pretty sure it is room boom, but maybe it is insufficient power to the woofers adding to the effect?    Will wait to see how Dave's 50watter bakoons go on the system?

Title: Re: bass traps for corners
Post by: Davey Willo on August 22, 2012, 02:45:04 PM
Hi Tuyen

Hopefully see you Saturday with the amps, I could probably bring a half a dozen or more 1200x600x50 slabs of rockwool (untreated so will leave a bit of fluff to be vacuumed up later) to temporarily stand in your corners if you want, very temporary, very ugly and a bit messy but hey a cheap and cheerful way of seeing if they have any effect on your room issues.

I'm still hoping to bring V along too if he's up for it.. Steve??
Title: Re: bass traps for corners
Post by: treblid on August 22, 2012, 02:57:11 PM
The bass traps I'm using were  from Flemo and they are quite effective.. Check with him what he uses.. I think he used Ultratels or Bradford or something but been years and I can't remember.

Title: Re: bass traps for corners
Post by: vitavoxdude on August 22, 2012, 06:57:10 PM
Saturday's a go mission control. What time?????
Yes your corner shagpile (?) :P would certainly assist in the boom boom stakes. 8)
V  ;)
Title: Re: bass traps for corners
Post by: kajak12 on August 22, 2012, 07:39:51 PM
Hi V,

Cheers for the reply.  I need to try me some of that!  I'm getting room boom on heavy tracks when listening at high spls.   I'm pretty sure it is room boom, but maybe it is insufficient power to the woofers adding to the effect?    Will wait to see how Dave's 50watter bakoons go on the system?


Yeh what time might pop in for a listen 8) 8) 8)
Title: Re: bass traps for corners
Post by: tuyen on August 23, 2012, 01:14:56 AM
After 12 is ok guys. I have Martin (mr azurahorn) coming over too. The room is not actually that big, so may be quite squishy.
Title: Re: bass traps for corners
Post by: tuyen on August 23, 2012, 01:17:39 PM
Hi Tuyen

Hopefully see you Saturday with the amps, I could probably bring a half a dozen or more 1200x600x50 slabs of rockwool (untreated so will leave a bit of fluff to be vacuumed up later) to temporarily stand in your corners if you want, very temporary, very ugly and a bit messy but hey a cheap and cheerful way of seeing if they have any effect on your room issues.

I'm still hoping to bring V along too if he's up for it.. Steve??

Hey Davey,

Don't worry about lugging along the rockwool.  Room will have enough bass boom absorbing men in there already, so will be fine :)

Cheers for offering though!
Title: Re: bass traps for corners
Post by: Paul Spencer on August 23, 2012, 01:31:45 PM
Tuyen if you can get 4 traps in all corners then you are a lucky man! Many people have doors, windows, furniture that count them all out.

Now having seen a recent pic of your room, it looks like heavy construction, so your comment on room boom is expected. In most rooms, plasterboard on a stud frame, or even a timber floor, acts as one big bass trap, although the lack of insulation makes it a poor bass trap.

There are two basic types - broadband and tuned. Broadband traps are basically just giant absorbers made bigger to work into the bass. The distance from the outside to the wall determines how low they will work. You can face them with pegboard to avoid making the room dead.

Tuned absorbers can be made smaller in terms of floor space - actually quite thin, but problem is they are tuned for a small range. So to use them well, you actually need to know what modes you are targeting. If you want to take a guess, go this formula:

172 / distance between room boundaries in metres - so in a rectangular room do it for floor - ceiling, and each pair of walls. You will often see a big peak in those regions, although you are better off to measure it so you really know. In my room, one of those three is dominant and I actually ride the wave of that mode so to speak. My sub runs up to it (44 Hz), my woofers run above it. It's a giant 15 db peak and even with giant bass traps, 2m wide it doesn't go away. You don't actually have to totall kill the modes, if you can do just enough then EQ and traps together can work wonders. The difference can be so big that you can hear it from outside the room.

In a room like yours, consider doing as much as you possibly can because it seems you are starting with a problem room at a guess. Very much like the Whatmough showroom here in Melbourne. They used four bass traps, each about a metre wide or so, floor to ceiling. Their room has split face heavy concrete masonry, concrete floor and ceiling. If you can make four traps like that, around 100 - 200mm thick with rigid fibreglass then you will notice a marked improvement. There is no magic to those, it's just a flat panel that straddles the corner on the diagonal, at least the width of a door. You might build a frame, you will want to wrap it in fabric, work out some way to avoid it falling over. Tricky in a rental, if you're a home owner then you might use brackets.

Now you can also consider bulkhead traps to get a bit more trapping without giving up any real estate. I'm my room I'm going to put one over the listening chair, where you don't generally see it. My room isn't big enough to put it all the way around the ceiling.

I wrote a primer here on traps:
http://www.hifizine.com/2011/09/bass-integration-guide-part-2/

Just one thing. If you do traps, don't go too small. A lot of people try to do that. Those little 1 ft foam traps do virtually nothing. Don't believe me? Check this out:

http://redspade-audio.blogspot.com.au/2011/04/do-small-foam-traps-actually-work.html

All you will hear with those is a change in the treble and perhaps midrange.
Title: Re: bass traps for corners
Post by: tuyen on August 23, 2012, 01:52:26 PM
Woah, excellent article there Paul. Thank you for that.

Alright, will look into proper corner traps in the near future.   Things will need reassessing if I end up getting the tuba horn from Andrew.  Even with my 360L onken bass cabinets, I'm pretty sure I'm missing the last octave in response.   

(http://www.ispra.net/audio/images/onken/hiraga/32a.jpg)

Title: Re: bass traps for corners
Post by: Paul Spencer on August 23, 2012, 01:59:19 PM
Tuyen,

It's entirely possible even with a speaker like that with about the same extension as some stand mounts, that you could get all the way down to 20 Hz in a room like yours (rough guess). It's also possible you wouldn't know it. Add together some room gain and your speaker roll off and it could get you down there, yet it might not sound like it. Why? Because the bass in the bottom octave needs to "sit up" a bit for you to notice it. Distortion levels also seem to have an impact, as well as modal ringing, both of which can tend to give the impression of more bass.
Title: Re: bass traps for corners
Post by: tuyen on August 23, 2012, 02:06:40 PM
I see I see...

Would you think that tuba horn would suit a system like mine at a guess?  I'm really only wanting to use it from <40hz  (24db cutoff the bash plate amp has set).

The design by Bill is meant to have low distortion and what not.. ?

Cheers!
Title: Re: bass traps for corners
Post by: Paul Spencer on August 23, 2012, 02:42:46 PM
I'm not familiar enough with the design to say too much. I will say this much. A bass horn needs to be big and anything below about 100 Hz is usually going to be compromised. When you shrink a bass horn, you can expect a peaky response and ringing. In a sub horn that is a given, so you have to cut down the bandwidth and make sure you aren't using it where it is ringing. That's why mine only goes up to about 40 Hz or so. You don't have to compromise as much with a 40 Hz horn, but one question is how how do you want to run it? Bill's designs are generally real world pro boxes, all of them seem to be compromised out of necessity.

In a very solid room like you have now, the room itself is the weak link in the chain, it will tend to swamp things like this. But if you get it really well sorted, and get bass decay completely under control, then issues like this are more likely to stand out. TD18 in a sealed box with a bit of power behind it, EQ and bass traps - that has the potential to completely redefine fast bass, and it's about as good as it gets. The driver has 28mm excursion from peak to peak, in a room like yours full of gain that is a lot.

You mentioned amp power. The thing I've noticed with driving bass is that underpowering it doesn't make things boomy as a rule, you just lose dynamics and authority. This became clear to me one day when comparing a 250w plate amp such as we find in many subs, to a meaty amp - a Crown K1 which is a fairly expensive pro amp. We ran them at what sounded like about the same level, but the difference was jaw dropping. We could not believe it. The extra grip, control and authority was staggering. We played a track with Eric Clapton live in Hyde Park - layla where the bass guitar was thick and punchy. The little plate amp should have had enough grunt to play at a level that wasn't crazy, but the Crown totally nailed it. My suggestion - put a good pro amp behind bass drivers. You'll save money and they do bass better.

The question you have to ask about the bass horn, is what do you want to achieve? Do you just want to have fun building the thing? In that case, go for it! I have a feeling you want to do it "just because" ... for the love of horns.

Do you want it because you love the idea of valves driving the bass? IMO that's the wrong reason to do it. To do bass well you need things that valves aren't well suited for. IMO, the real advantages of valves live everywhere else.

I'd want to see a real measurement of the horn in question, an unsmoothed warts and all one. Last time I saw BFM measurements they looked a bit prettified, a bit too santised.

One more comment. With bass horns, the way you load it into the room makes a huge impact on the size and degree of compomise. The best way to do it is with the mouth firing into the corner so that the corner becomes an expansion of the horn. Have you seen Avantgarde bass horns? Silly question! Ok, they put them in the centre of the room because that is where they fit. But they could effectively double up, by splitting them in two and putting them in corners. Each horn is a module, which is like a quarter slice of pie. Now stack those modules in the corners and the quarter of a circle horn in one corner now equals the half of a circle version that was sitting in the middle of the room. I did some modelling of those horns when I was tempted to make something similar. They work out to be a good design for 40 Hz and you could actually DIY one of those with some sheet metal for the curves. IIRC the radius of the full circle is about 1m, with the height of each module about 700mm or so. Stack about 3 in each corner and you have a pretty serious bass horn. The AG version has so many bass drivers that you can then EQ the bottom octave in, and easily get to 20 Hz. It's quite a clever idea. I would have done it, but I realised that it was going to be a bit big. My bass horn is under the floor.

When I modelled the AG bass horn, I quickly realised that their design when placed into a corner, it's not a cut down compromised design. You could build it with sheet metal that is thin enough to easily bend, fitted into a slot in the top and bottom, laminated together with a stack of contact adhesive, or construction adhesive. It has some challenges, but it could be a fun project.

So what happens if you take those horns and move them away from the corners in the middle of the front wall? You have to make the horns now TWICE AS BIG! Bring them out into the room, so that the wall behind is no longer reinforcing, so the mouth is out into the room. Now you have to double the entire thing again! This is due to loading. So if you have your heart set on doing a bass horn to get down to 40 Hz, and you want to do it right, the smart thing is to load it into the corner so the corner acts as an expansion of the horn. Ideally do it with modules so that now you've created a mouth that runs floor to ceiling.

Only problem is, now they are fighting for bass trap real estate. Dilemmas, dilemmas ...
Title: Re: bass traps for corners
Post by: terry j on August 23, 2012, 03:45:28 PM
sheesh paul, there is a lot in those last two posts!

Curious question, regarding using the walls as an extension of the horn, does that include (somehow) the floor and ceiling? Say in my room, let's mount them equidistant from both, that effectively (?) leaves just the walls. How do you slot the floor and ceiling in if needed?
Title: Re: bass traps for corners
Post by: Paul Spencer on August 23, 2012, 04:15:54 PM
Corner loading includes floor and two walls, but if the mouth of the horn extends to the ceiling, then you are firing into an even more constrained space, I believe it's a step beyond corner loading. I'm not sure I can visualise what you are thinking ... top and bottom corners?
Title: Re: bass traps for corners
Post by: tuyen on August 23, 2012, 04:40:45 PM
Buggeroony, I think the tuba horn sub may be sold to another sna'er who lives next suburb to Andrew..  he will let me know if he decides to buy it tonight after audition.  ah well..

But anyway, I'll answer some of your points, Paul. :)  I never thought to power something like the tuba sub with my currrent power amp.  I would of just split the line singal that goes into the poweramp, into the o-audio 300watt bash plate amp  and run power the woofer with that.    The rythmik direct servo 300watt or 600watt plate amp units are meant to be top notch units with bit more tweakability too.  They are highly recommended by an audio engineer guy I know. He personally runs 2x rythmik 15" stereo subs  in his 5-way horn system and rates it pretty much up there.     Is the crown amps noisey because of the fans?   My previous experience with PA amps (cousin does sound for WA Vietnamese Community events) is the fans are noisey as..  but the gear he uses is pretty old.

I don't like building stuff like cabinets, so I wouldn't have fun doing it.   I had just thought the idea of the tuba horn sub with the description of it having 'effortless' sense of bass and low distortion, would fit my system well.   Maybe an AE TD18 in a sealed cab would have the same or maybe better performance, that I'm not sure..    

The look of the long tuba horn sub is cool and would of fit at the back of the room corner just filling in the 20-40hz range to give that extra sense of scale and engagement with the music. Also, if experience in tuning some serious car stereos in my past life goes by anything, when a system does fill that bottom octave properly, it also (subjectively?) affects the midrange and treble too, adding a bit more fluidity/liquidity. Engagement factor increases for sure..
 
Title: Re: bass traps for corners
Post by: ozmillsy on August 23, 2012, 06:48:23 PM
Which Andrew,  me?    Pm me and let me know who.   I'd be interested to go hear it, if they buy it.
Title: Re: bass traps for corners
Post by: Paul Spencer on August 23, 2012, 08:51:36 PM
Rythmik servo subs - I'm a fan. They are very clean and dry in the bass.

TD18H sealed is likely to be more accurate than a bass horn. Bass horns are effortless yes, but they can also add a certain tactile bone crunching oomph to them that is fun and funky, but they can also have a bit more personality.

I built this one with Antripodean on SNA for the fun of it:

(http://4.bp.blogspot.com/-MHD40rK3GKA/Tyo7tZvqZOI/AAAAAAAABU0/XwSfjKrAjpo/s1600/f20-t20.gif)

F20 on the left, T20 on the right (mine)

Now this is what a compromised horn measures like:

(http://2.bp.blogspot.com/-UwR9Dvsn_Cs/Tyo5CIvQduI/AAAAAAAABUk/nMC01rLOcXg/s1600/RythmikT20-F20-SPL.gif)

It's a sim but you get the idea. You can't use them where they are super peaky.

F20 with a Rythmik 12" driver on top:

(http://3.bp.blogspot.com/-wmaXX0Te2MM/TzNM2V_N75I/AAAAAAAABZE/XuC78bAdiV0/s1600/IMG_2374.jpg)

This is a very quick and dirty build with cheap Chinese ply. It was made just for fun without intention of using it for any amount of time. Mine is also quick and dirty since it was made to live under the floor. It is rough and ready in looks, but in the areas that matter for performance, like sealing, strength and bracing, it's well made. Due to the push pull driver mounting, the box has so little vibration it's hard to tell when it's running, except for the sound.

The F20 is a lot of fun for pop rock where you might enjoy a bit of exaggerated punchy bass. I didn't spend enough time with it to integrated it seriously and see how it performs with acoustic double bass, but I have doubts it could match say a Rythmik servo sub or a TD18 in a sealed box.

Crown K1 has no fan - it's dead silent, and that's part of why it was expensive.

Quote
Also, if experience in tuning some serious car stereos in my past life goes by anything, when a system does fill that bottom octave properly, it also (subjectively?) affects the midrange and treble too, adding a bit more fluidity/liquidity. Engagement factor increases for sure..

Very true in my experience. Bass is not just about bass. It affects everything else.

I remember trying to do one comparison on a Unity horn with nothing below 300 Hz. That is less than 3 out of 10 octaves missing, and it's enough to totally kill the music. It's like eating a meal of lettuce leaves.
Title: Re: bass traps for corners
Post by: tuyen on August 23, 2012, 09:56:40 PM
ozmillsy:  Sorry, I meant 'atilsey' on sna whos name is Andrew as well.   I gave priority to a local buyer 'henry218' who has confirmed the purchase of the unit after listening to it tonight.   

Back to the drawing board :)

Paul, the sim fr of the bass horn seems fine for my application I'm after.  If I had to choose between wanting to try out a bass loaded horn sub or sealed, I'd probably want to try out the horn type first. I love that 'effortless' style of sound, over super tight/dry character.

what's your opinion on importance of stereo sub bass or is mono fine, taking in consideration I only am looking for a <40hz solution.

The F20 and T20 designs seem pretty cool and could be a possibility?  Do they have similar sonic traits?

cheers mate

Title: Re: bass traps for corners
Post by: Paul Spencer on August 23, 2012, 10:14:51 PM
T20 vs F20 ... F20 is a front loaded horn design with more chunky proportions, more volume and more efficient in material use, but its form factor makes it harder to hide. When made into that kind of size, it tends to be bandwidth limited like a tapped horn. Tapped horns are always bandwidth limited, but with a FLH you have a chance to get them to run over a wide bandwidth. Not that you need it here.

Now for a given size and extension, a tapped horn will tend to protect the driver from excursion to a lower point, but with no sealed cavity, you ideally need a rumble filter. T20 controls excursion to 20 Hz nicely. With F20, at 25 Hz the excursion jumps right up, but then reaches a point where the sealed rear air volume stops it going further. Still, excursion limits come in much sooner. So in terms of getting max SPL, the tapped horn wins. Both seem to occupy similar territory in terms of their sound. They are brutal, funky, tactile, forceful.

When I had them both in the same room, I didn't really compare them doing the same job. One was in the corner, the other plonked in the middle of the front wall. They are gigantic in any room, you can't really shift them easily. Although, I'm proud to say I managed to get my T20 from the workshop into the HT room on my own when I finished it at 11pm one night. Not bad when you consider it can't make it through the workshop door way without going on a very difficult angle, it's 2.35m tall!

The horns definitely have a different sound. If I could put it this way. Horns for rock, pop, bass heavy music and home theatre. Sealed for acoustic double bass and where you want accurate bass. But everyone should experience a bass horn with some time to spend with them, at least once. I will soon be using both, kind of a cake and eat it too setup.
Title: Re: bass traps for corners
Post by: tuyen on August 24, 2012, 12:50:58 PM
Hi Paul,

Any designs which uses just 1 bass driver?   Not really looking for crazy spls, as I listen to music at relatively low to medium volumes..

Also thoughts on stereo subs vs mono for my application (ie. <40hz)?

Title: Re: bass traps for corners
Post by: Paul Spencer on August 24, 2012, 01:08:45 PM
F20 is originally meant for just one driver, I modified it for a pair of 10" woofers. Don't overlook the advantage of using two drivers dual opposed - they cancel vibration and you can pay less attention to the box if you are feeling lazy. If you don't want very high output then a pair of Peerless XLS drivers would probably do well in my T20, or even a pair of woofers.

Below 40 Hz - if you have two subs well it's not too difficult to make them stereo, but I wouldn't go out of my way to get it. It's not something I've tested carefully, but mostly I've had stereo bass all the way down, not due to any great conviction but just because it was no effort to get it. Now I'm moving towards mono below 40 Hz. The hearing mechanisms involved in stereo perception tend to break down at low frequencies. In the midrange and top end we easily pick image location due to the different time and intensity of the sound in each ear, as well as a few processing tricks in the system. When the wavelenths are longer than the dimensions of the room itself, the distance between each ear become pretty minor! Also the difference in intensity is less, becuase the wavelenths are so long the bass just wraps around your head with no acoustic shadowing. We count on things like harmonic distortion to locate the bass. Short answer - stereo sub bass won't hurt, go for it if convenient.

Title: Re: bass traps for corners
Post by: tuyen on August 24, 2012, 01:45:25 PM
Thanks heaps for the info Paul. 

Andrew (atilsey) said he is happy to build another tuba horn if I was interested..  will see what price he comes back with.. might just be easiest in my situation to go with something like that.     I'm not really into building/testing out different woofer cabinets..  not even sure how I would be able to bring the pieces of wood home from the shops, if I was keen to try!
Title: Re: bass traps for corners
Post by: terry j on August 24, 2012, 02:30:10 PM
Corner loading includes floor and two walls, but if the mouth of the horn extends to the ceiling, then you are firing into an even more constrained space, I believe it's a step beyond corner loading. I'm not sure I can visualise what you are thinking ... top and bottom corners?

I prob misunderstood you. See if the following shows where I went off the rails.

A horn is completely bounded, either a real horn (circular) shape or simply four walls.

To go low means you gotta go big. You mentioned however the 'free' gain if rather than making the actual horn huge, instead we mount it in the room corner, and in effect the walls either side become the horn walls/boundaries. For those two sides we have not actually built the horn walls, rather we have the room walls serve that purpose.

Did I follow you correctly to this point?

Hence my question, I started from the idea that a horn has four boundaries, well at least fully bounded. Two walls either side are only two boundaries, what about the top and bottom? Hence my question about floor and ceiling, thinking that they are analogous to the two 'missing' boundaries.

Title: Re: bass traps for corners
Post by: vitavoxdude on August 24, 2012, 02:49:25 PM
Hi Paul,

Any designs which uses just 1 bass driver?   Not really looking for crazy spls, as I listen to music at relatively low to medium volumes..

Also thoughts on stereo subs vs mono for my application (ie. <40hz)?


IMV 2 subs are always better than one as long as they do not upset the room too much.  2 subs = half the driver excursion = faster more realistic bass. ;D  Until you get down to beneath 18Hz you can still tell where the sound is coming from so unless a single is placed between the speakers then it will not sound quite right. :-X  If my deep bass drivers did not weigh so much I'd bring them round but 2 strong men do not cut it as they are >100Kg each with the built in amps. :'(
V
Title: Re: bass traps for corners
Post by: Paul Spencer on September 11, 2012, 12:21:42 AM
Corner loading includes floor and two walls, but if the mouth of the horn extends to the ceiling, then you are firing into an even more constrained space, I believe it's a step beyond corner loading. I'm not sure I can visualise what you are thinking ... top and bottom corners?

I prob misunderstood you. See if the following shows where I went off the rails.

A horn is completely bounded, either a real horn (circular) shape or simply four walls.

To go low means you gotta go big. You mentioned however the 'free' gain if rather than making the actual horn huge, instead we mount it in the room corner, and in effect the walls either side become the horn walls/boundaries. For those two sides we have not actually built the horn walls, rather we have the room walls serve that purpose.

Did I follow you correctly to this point?

Hence my question, I started from the idea that a horn has four boundaries, well at least fully bounded. Two walls either side are only two boundaries, what about the top and bottom? Hence my question about floor and ceiling, thinking that they are analogous to the two 'missing' boundaries.



In order to use the floor, ceiling and walls as boundaries, you need the horn mouth to equal the size of the front wall!

Let's take a step back. First, we have free space, a speaker radiating as it it would if suspended up in the air. Now we put it on the ground - half space. That is what we estimate with speaker modelling usually. Next step is quarter space, we add the rear wall. To get this with a horn, the mouth needs to be near the floor and rear wall. Often it is not even this constrained, with horns sticking out into the room so they see only half space loading. Such a horn has to be big!

The length of the horn is related to tuning, the size of the mouth is related to the loading (half space, etc). Each time you jump down to a more constrained "space" then you can halve the mouth size.

Next step is a corner, so we now add the side wall and we have 3 boundaries. We can realistically achieve this kind of loading by firing the mouth into the corner. The next step is to extend the mouth up to the ceiling, using modules most likely. We now have a more constrained loading, but I don't know what we would call it. One step further, and this is as far as we can go, is to make the entire front wall the mouth of the horn. In that case the entire room becomes a horn, and the listening position is now nearfield for the bass, as you are sitting in the mouth of the horn. You launch a plane wave into the room, and all room modes are gone with the exception of the depth mode, which would now be excited very strongly.

In your room Terry, what would be interesting is a double bass array, because you could actually make it work. Most rooms aren't big enough.
Title: Re: bass traps for corners
Post by: terry j on September 11, 2012, 03:18:19 PM


In your room Terry, what would be interesting is a double bass array, because you could actually make it work. Most rooms aren't big enough.

cept for the 'crazy' orientation in the room. And that, after more than a few experiments, is non negotiable!
Title: Re: bass traps for corners
Post by: kajak12 on September 11, 2012, 08:23:17 PM


In your room Terry, what would be interesting is a double bass array, because you could actually make it work. Most rooms aren't big enough.

cept for the 'crazy' orientation in the room. And that, after more than a few experiments, is non negotiable!
how are you going tj????????????
Title: Re: bass traps for corners
Post by: Paul Spencer on September 12, 2012, 01:51:12 AM


In your room Terry, what would be interesting is a double bass array, because you could actually make it work. Most rooms aren't big enough.

cept for the 'crazy' orientation in the room. And that, after more than a few experiments, is non negotiable!

Doesn't matter at all with a DBA, because you are creating a plane wave. Both plane wave arrays are time aligned, the rear one inverted in polarity to yield an anechoic response completely free from room interaction. You know the arrangement I'm talking about right?
Title: Re: bass traps for corners
Post by: terry j on September 12, 2012, 03:56:09 PM

how are you going tj????????????

You talkin to me mario?? If so, thanks for the interest! We seem to have a funny relationship..'at each others throats' one minute, the next not so much :D

Cept for my bloody back when I blew it doing some jackhammering, pretty good thanks. Seein as how the bathurst bgtg is coming up soon, at least I can get my tweeter back into the system and ready. However, that also means man handling these speakers which weigh, dunno, 100+ kgs each? so with my back right now even that is iffy.

So just hobbling around the house atm.

You still up for that long promised visit when you're over this way? If not, things always get in the way, maybe we'll at least meet at the hi fi show depending on days etc.
Title: Re: bass traps for corners
Post by: terry j on September 12, 2012, 04:00:31 PM


Doesn't matter at all with a DBA, because you are creating a plane wave. Both plane wave arrays are time aligned, the rear one inverted in polarity to yield an anechoic response completely free from room interaction. You know the arrangement I'm talking about right?

Sure, I know the arrangement. That big thread on avs I think it was.

Guess you're right when I think about it, as long as the two planar waves meet at the LP, and depending on xover point, the result should be the same.

Still, given the crazy layout and what walls the drivers could be mounted on it still seems problematic to me. Heh, we can look at it theoretically when I see you and the layout is before the both of us.

Still, I must confess to not feeling I have any great need for better or improved bass. Still, these things are always comparative so who knows ultimately..
Title: Re: bass traps for corners
Post by: Paul Spencer on September 12, 2012, 04:18:23 PM
Terry, the real problem is pragmatic - mounting subs on the walls, especially with your 50m high ceiling. The real bummer about a DBA is that you use 8 subs but get the output of about 2. In other words, buy 6 more identical subs, and another power amp and you get an anechoic version of your current subs. The result could be "wow, the bass is even better" or it could be "ho hum, I wasted all that money and effort and it's no better." Someone is selling four on DTV, so you (almost) have the chance, someone on SNA is selling a single as well. But actually I know a driver you could get that is good value.
Title: Re: bass traps for corners
Post by: terry j on September 12, 2012, 05:52:15 PM
Terry, the real problem is pragmatic - mounting subs on the walls, especially with your 50m high ceiling. The real bummer about a DBA is that you use 8 subs but get the output of about 2. In other words, buy 6 more identical subs, and another power amp and you get an anechoic version of your current subs. The result could be "wow, the bass is even better" or it could be "ho hum, I wasted all that money and effort and it's no better." Someone is selling four on DTV, so you (almost) have the chance, someone on SNA is selling a single as well. But actually I know a driver you could get that is good value.

yeah, that 50 m high ceiling is a bitch!  ;D You can change the light bulb for me next time.

Your other point is more valid, it's funny cause basically I never have to worry about WAF, as you may have noticed, yet there is no damned way I would ever touch the fabric of the house given what it is (and the work being put into it) so the mounting issue you raised, not ever having thought about it rules it out straight away. Even with my bass traps, I have to be wary of how I mount them as well as not going all the way up. no point in covering the cornice in the room seein as it is an architectural feature.

I take it you mean maelstroms on dtv? See, all I'd ever do is two more sealed subs, forget the DBA. Do I need two more subs with the amps required and how to control it? Nah.

well maybe nah :D
Title: Re: bass traps for corners
Post by: kajak12 on September 12, 2012, 09:50:14 PM

how are you going tj????????????

You talkin to me mario?? If so, thanks for the interest! We seem to have a funny relationship..'at each others throats' one minute, the next not so much :D

Cept for my bloody back when I blew it doing some jackhammering, pretty good thanks. Seein as how the bathurst bgtg is coming up soon, at least I can get my tweeter back into the system and ready. However, that also means man handling these speakers which weigh, dunno, 100+ kgs each? so with my back right now even that is iffy.

So just hobbling around the house atm.

You still up for that long promised visit when you're over this way? If not, things always get in the way, maybe we'll at least meet at the hi fi show depending on days etc.
I will be at steves in october,if i can get to your house i will
Title: Re: bass traps for corners
Post by: terry j on September 13, 2012, 08:15:19 AM

I will be at steves in october,if i can get to your house i will

Well, as I have always said, you'd be welcome. It is about an hour or so away, maybe hour and a half or thereabouts. Still, TBH, you'd just be better off enjoying meeting your mates I'd guess. I'm still undecided if I'll bother going to the show, may as well I guess, so at least we can have a coffee if we go on the same day.

Or a beer!
Title: Re: bass traps for corners
Post by: stevenvalve on September 13, 2012, 02:33:18 PM

I will be at steves in october,if i can get to your house i will

Well, as I have always said, you'd be welcome. It is about an hour or so away, maybe hour and a half or thereabouts. Still, TBH, you'd just be better off enjoying meeting your mates I'd guess. I'm still undecided if I'll bother going to the show, may as well I guess, so at least we can have a coffee if we go on the same day.

Or a beer!
Terry. You will meet fellow mountain audio heads, you can listen to their good mountain systems, then the show, it is important to come, make the time. The show will disappear new friends will not. There is a lot for everyone to learn.
Title: Re: bass traps for corners
Post by: terry j on September 13, 2012, 02:54:37 PM
steven, again given our 'track' your response is more than gracious.

Ahh, the mountains, gotta love it. Went to school just up from you, lived a decade at lawson. Beautiful area, cept for the traffic nowadays I suspect!

Spose you're right about making the effort for the show, they'll prob disappear again..anyone know if last years was deemed a success? Seems a few missing this year, eg SGR. Earle I know is too busy and does not need more work, but woulda thought sgr would be there (unless I simply missed them on the list)

I presume lenehan will be there?? Another brand with a rep I'd like to have a listen to.

Another that intrigues me, those 80k two ways, name escapes me as I type, guru sells them, big wig name, as soon as I hit post I'll no doubt remember...anyways that much for a two way? Audio note is it?

Re the systems in the mountains, sounds like a good idea for a travelling circus! Must be a few there now worth a round trip visit. Bit like the open garden set up :D A smorgasboard if you will.

In any case, if I go I intend to do a bit of syd catch up with mates, so for me personally looking at sat with the mates on sun. Drive home yada yada. Not for a second did I think I'd put my hand up for your gtg, I doubt I fit that particular group profile audio wise, so no doubt would be an awkward guest in more ways than one.

BUT, a quick drop in to shake your hand for your magnanimousness and a quick meet and greet (if we don't cross at the show) does sound worthwhile.
Title: Re: bass traps for corners
Post by: tuyen on November 16, 2012, 09:48:25 AM
Been using a few wide band absorber panels for awhile now. Nice improvement overall. Just makes me want to turn the volume up.

The main ones that gave most benefit were the side panels to block first reflection points.

(http://i45.tinypic.com/29z32bb.jpg)

Page about the effects that I could understand:
http://www.facstaff.bucknell.edu/esantane/movies/Acoustic.html (http://www.facstaff.bucknell.edu/esantane/movies/Acoustic.html)
Title: Re: bass traps for corners
Post by: Paul Spencer on November 16, 2012, 10:30:23 AM
Treating first reflection points is slighly controversial. I hear generally that most people who try it like the result, however, there is some research indicating that it's not the thing to do, that as far as reflections are concerned, the ones off the side wall are the ones that add most to the sense of body. Floyd Toole is the champion of that viewpoint. So the question is, and it's one not easily answered for certain, 'why do you like it?' Is it because the first reflection points are doing harm? Or is it because those points are the places where your speakers are directing a more fullrange sound, hence panels there have the most effect in bringing down the reverb in general. If you put panels further off axis, then there isn't as much treble for example, so they will have less effect.

Here's my little theory. Unproven, just a bit of a hunch really. You want to have a certain amount of general absorption in a room to get the reverb time down to a certain range, so there is a nice balance of sound direct from the speakers mixed with sound from the room. If you can get your RT to measure flat across all frequencies, and somewhere around 0.3 - 0.4 seconds and then plenty of bass absorption, as indicated by the in-room decay plots, then you can have a pretty good canvas to paint with.
Title: Re: bass traps for corners
Post by: Tuyen on March 25, 2014, 10:18:58 AM
Borrowed some of a friend's bass traps (a pair of small corner ones and a pair longish wideband panels).   Placed them all at the front of the room.   

Helps with the sound so much (especially with bass. duh)  that I really am kicking myself for selling my previous bass traps and for so cheap (sold them thinking I was not going to use the room for music anymore, but things have changed!)

So plan to build some panels and corner traps.

Was thinking of following something like this for the corners.  http://www.radford.edu/~shelm/acoustics/bass-traps.html (http://www.radford.edu/~shelm/acoustics/bass-traps.html)

Will do a few flat panels too. 

Any advice from guys who have done this stuff already?