Author Topic: bass traps for corners  (Read 6721 times)

tuyen

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bass traps for corners
« 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

Offline vitavoxdude

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Re: bass traps for corners
« Reply #1 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.
We all like different things so lets all agree to disagree and if any common ground is found then worship it.  Mine is the KD hence being present on this forum.

tuyen

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Re: bass traps for corners
« Reply #2 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?


Offline Davey Willo

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Re: bass traps for corners
« Reply #3 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??

Offline treblid

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Re: bass traps for corners
« Reply #4 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.


Offline vitavoxdude

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Re: bass traps for corners
« Reply #5 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)
;)
We all like different things so lets all agree to disagree and if any common ground is found then worship it.  Mine is the KD hence being present on this forum.

Offline kajak12

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Re: bass traps for corners
« Reply #6 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)
still discovering the link between electronics and audio reproduction.so much to learn and so little time

tuyen

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Re: bass traps for corners
« Reply #7 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.

tuyen

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Re: bass traps for corners
« Reply #8 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!

Offline Paul Spencer

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Re: bass traps for corners
« Reply #9 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.

tuyen

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Re: bass traps for corners
« Reply #10 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.   




Offline Paul Spencer

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Re: bass traps for corners
« Reply #11 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.

tuyen

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Re: bass traps for corners
« Reply #12 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!

Offline Paul Spencer

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Re: bass traps for corners
« Reply #13 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 ...

Offline terry j

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Re: bass traps for corners
« Reply #14 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?

Offline Paul Spencer

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Re: bass traps for corners
« Reply #15 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?

tuyen

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Re: bass traps for corners
« Reply #16 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..
 
« Last Edit: August 23, 2012, 04:42:24 PM by tuyen »

Offline ozmillsy

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Re: bass traps for corners
« Reply #17 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.
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Offline Paul Spencer

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Re: bass traps for corners
« Reply #18 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:



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

Now this is what a compromised horn measures like:



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:



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.

tuyen

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Re: bass traps for corners
« Reply #19 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