overwhelming bass

by Lamkochai on Sat Mar 20, 2010 12:51 pm

i have recently upgrade my amp to a more powerful 40w from my previous 14w unison research preludio. speakers used is Harbeth SHL5. while the bass is tauter and the overall sound is fuller, the bass remain a prob on certain cd i listen to.

I cant describe properly how it sounds like but sometime the bass is jsut too much and not well defined. Lower piano note and double bass, cello all sound ok. but when it comes to more complex electronic music or pop music, the bass is too overwhelming and uncomfortable. A few of my audiophile friends who visit me say its bass boom.

my listening area is around 15x20 feet. left side is mostly glass window covered with curtain, right side is open to dinning hall and kitchen. my 10ft height ceiling is not treated i.e mainly hard cement. the picture of my listening area can be seen in general discussion section of this forum under the title 'members system‘.

i need advice on what should i do next. is it my listening area problem? will changing my speakers to smaller standmount help? is it useful if i put more bass traps but where to put them? (lower corner, upper corner,along the upper edge of the wall?). For those who own Harbeth shl5, what is the dimension of your listening area and any bass boom prob?

by uncle_vic on Sat Mar 20, 2010 1:38 pm

I've friends with hl5 and hl5super. Maybe u like to make friends with them to share notes, or lament over the same problems?!

by Lamkochai on Sat Mar 20, 2010 2:23 pm

ookok. receive your pm before. will call you when i go to kl next month.

by kkthen on Sat Mar 20, 2010 3:49 pm

I got one friends play super HL5 + 60w solid state amp in 7 X 14 ft Room at Penang, he very enjoy his system. I never hear his system before, if you are interest to contact him, I can PM his phone number to you.

by tycham on Sat Mar 20, 2010 4:05 pm

uncle_vic wrote: ..or lament over the same problems?!

My friend got this same problem. His is driven by the LFD Zero MKIII.

by Lamkochai on Sat Mar 20, 2010 5:12 pm

the set up i listen in the dealer showroom doesnt have that prob. but during the av show in jw marriot, there is some degree of bass boom but its worse with my set up. i have actually consulted Sam (tropical audio) and he gave me 2 foam to plug into the bass port but it isnt helping much. i guess the listening environment is very important.

i should visit uncle vic's friend to listen to other ppl setup.

TYcham, how does your friend settle the prob? i thought LFD should be matching well with harbeth.

by tycham on Sat Mar 20, 2010 6:00 pm

@Lam

I think my friend rooms is similar to yours with one side opening to somewhere. I gave him 3 pcs of rockwool but didn't ask him about the problem, nor does he mention anything about it since then.

Maybe should pay him a visit to have a listen.

by tlkoo on Sat Mar 20, 2010 7:04 pm

Lamkochai wrote:i have recently upgrade my amp to a more powerful 40w from my previous 14w unison research preludio. speakers used is Harbeth SHL5. while the bass is tauter and the overall sound is fuller, the bass remain a prob on certain cd i listen to.

I cant describe properly how it sounds like but sometime the bass is jsut too much and not well defined. Lower piano note and double bass, cello all sound ok. but when it comes to more complex electronic music or pop music, the bass is too overwhelming and uncomfortable. A few of my audiophile friends who visit me say its bass boom.

my listening area is around 15x20 feet. left side is mostly glass window covered with curtain, right side is open to dinning hall and kitchen. my 10ft height ceiling is not treated i.e mainly hard cement. the picture of my listening area can be seen in general discussion section of this forum under the title 'members system‘.

i need advice on what should i do next. is it my listening area problem? will changing my speakers to smaller standmount help? is it useful if i put more bass traps but where to put them? (lower corner, upper corner,along the upper edge of the wall?). For those who own Harbeth shl5, what is the dimension of your listening area and any bass boom prob?

by **drife** on Sat Mar 20, 2010 8:18 pm

http://www.odysseyaudiohk.com/cgi-bin/yabb/YaBB.pl?num=1112024649tried strawed ports aka proac tablette II style? There's a pic in the FS section. my spkrs came with them so i don't have the boom problem. use the stiff one not the coffee shop kopi peng one. lucky me i didn't have to visit McD or KFC and keep pressing on their straw dispensers. coz then floor manager might just stare kock at me. but i've yet to experiment with box drink straws aka drinho, yeos straws. SHL5 tamed by drinho straws, powah!

by Lamkochai on Sat Mar 20, 2010 9:49 pm

thank you drife. tonight i will try the kopitiam one. will tell you the result later. going out to buy coffee now

by **drife** on Sat Mar 20, 2010 10:55 pm

wei, kopi peng one here pls. haha, miss the good ol penang food. sorry subangites, the food here don't come close to PG food. my daily makan here is just "grab and go" food that only fills the stomach. no effort, no deninition, no grunt, no soul...try holding the straws together with sticky tape and also experiment with different lengths, different material/stiffness of the straws.

by car o scope on Sat Mar 20, 2010 11:07 pm

Perhaps, it is a standing wave issue.
The room tarak ngam in certain frequencies.

by **drife** on Sat Mar 20, 2010 11:44 pm

im having problems with the opposite in the room. sometimes i feel the low notes are missing. cross-cancellation thanks to the resonating wardrobe. or maybe too much absorption due to the big elcheapo durasuede sofa. when i've "saved up" enough i'm gonna chuck this old sofa outta the window.on the contrary, my bro's got synthetic leather sofas and the bass was overwhelming in the low ceiling small hall, on 8ohm 90db bookshelves with 8" cones, powered by a 30wpc, 20-25amps ss integrated.this sofa thing's driving me nuts. i can't afford full leather at the mo, so i might just try normal fabric or synthetic leather elcheapos in the near future. enough of durasuedes!

by BrAvO on Tue Mar 23, 2010 11:51 pm

I experienced with this bass boom problems before. It is also because it is going through the running in process. Give it a good number of hours to run in the transformer/output trans. Sure it will be better.

by mugenfoo on Wed Mar 24, 2010 12:56 am

your dimensions are 10x15x20 ??? Koyak lor ..... the 10ft will have the same standing waves as the 20ft length.. and the 15ft (transverse mode) will also hit the room's longitudinal and vertical modes too.

quite a bad distribution of eigentones in this room with lots of accentuations from the overlapping standing waves from the 10ft and 20ft lengths. Summore the ceiling is concrete, means that all the 10ft height's 0-0-1,0-0-2,0-0-3,...,0-0-n modes are reflected back as strongly as the 20ft length's 1-0-0,2-0-0,3-0-0,...,n-0-0 modes. And the 0-0-1 mode will clash with the 2-0-0 mode.

I'd bet you'll have a real nasty boom at around 115Hz , thats where the room's 0-0-2, 4-0-0 and 0-3-0 modes all pile up at the exact same frequency.

Seems most likely (almost 98% sure) to be a room problem. Don't blame the Harbeths.

Lamkochai wrote:i have recently upgrade my amp to a more powerful 40w from my previous 14w unison research preludio. speakers used is Harbeth SHL5. while the bass is tauter and the overall sound is fuller, the bass remain a prob on certain cd i listen to.

I cant describe properly how it sounds like but sometime the bass is jsut too much and not well defined. Lower piano note and double bass, cello all sound ok. but when it comes to more complex electronic music or pop music, the bass is too overwhelming and uncomfortable. A few of my audiophile friends who visit me say its bass boom.

my listening area is around 15x20 feet. left side is mostly glass window covered with curtain, right side is open to dinning hall and kitchen. my 10ft height ceiling is not treated i.e mainly hard cement. the picture of my listening area can be seen in general discussion section of this forum under the title 'members system‘.

i need advice on what should i do next. is it my listening area problem? will changing my speakers to smaller standmount help? is it useful if i put more bass traps but where to put them? (lower corner, upper corner,along the upper edge of the wall?). For those who own Harbeth shl5, what is the dimension of your listening area and any bass boom prob?

by chamts1 on Wed Mar 24, 2010 8:55 am

Hi Lamkochai,
Read this write up & see if you agree with the writer... http://hifi-unlimited.blogspot.com/2010/02/whats-your-level.html ... anyway my takeaway from him is that room contributes about 1/2 & the other 1/2 came from equipment... I like the sound of Sam's set up, CD-66, 34, 606, Quad Cables, SHL5, but the very same system in another room is quite a let down... so my guess is that you need to work on your room ... or more interesting... cart your whole set to a friend or shop room which sounds nice to you... I have been thro that & glad I did it...happy testing...
Kind regards
Cham TS

by **WongKN** on Wed Mar 24, 2010 11:33 am

Kopi peng ? Penang food ? I thought it should be Air Itam Laksa, Swatow lane curry me, lorong selamat ais kacang, and so forth ?

Lamkochai,

I agree with mugenfoo that your room seems most likely to be the main problem. Multiples (i.e. length = exactly 1.5 times the width and 2 times the height) is a surefire recipe to disaster.

With room, we often need to resort to room treatment and those are either expensive or very iffy. This is because bass frequency cannot easily be tamed by simple foam, etc. Your best bet is a Helmholtz resonator but those are big and expensive things. Don't be naive and expect some small items or simple foams to be able to control the bass. It is not that easy.

One pretty straightforward way you can -try- is to lug your living hall sofa, the biggest possible, into your listening room and then see if that helps. Only something as large as a sofa will have a chance to interfere with those standing waves mugenfoo was referring to. A soft sofa is also a pretty good bass absorber. It may help. If it works well, then you have a choice but let's talk about that ONLY AFTER you have tested it and it works. Or if it don't work, then the alternatives.

Try it ASAP and let us know the result.

by uncle_vic on Wed Mar 24, 2010 1:03 pm

Hi Lam, do a measurement see if u can decipher anything from the data. There are more than 1 way round the problem. Most if not all are technologically based on whatever know how that is available to us today.

Room acoustic is one of the biggest headache encountered by audiophiles as the room contribute a major part of the sonics. One suggestion from me is to go visit systems in treated room and decide for yourself what acoustic treatments are best used in your listen room. Some treatments are expensive, some are not so expensive but requires lots of hard work from you. Are u prepare for the knowledge and the hard work ahead of u before u hear good sound?

There is a price in everything we do for the sake of hifi pursuit.

by tycham on Wed Mar 24, 2010 1:06 pm

WongKN wrote:

Don't be naive and expect some small items or simple foams to be able to control the bass. It is not that easy.

One pretty straightforward way you can -try- is to lug your living hall sofa, the biggest possible, into your listening room and then see if that helps.

That's right! You need MASS to tame the low frequencies.

by cheekee on Wed Mar 24, 2010 2:40 pm

You may want to correct fundamental set-up issues before exploring complicated solutions involving room treatment. I used to have bad bass boom even though it was a bookshelf speaker in a large room. Eventually, it was down to positioning of speakers: I had to ensure that the distance from the each speaker to the side wall is about the same.

Another area that contributes to 'too much bass' is improper supports for your equipment.

If you want the best from your system, choose the best room available (avoid reinforcing ratios - check out cardas' golden ratio rule for rooms) and give highest priority to system layout orientation and take care of reflective surfaces like the floor (carpets), walls (curtains etc). Ceilings are tricky - I found that if the floor absorbs well, you can usually forget about treating the ceiling. Put the rest of the house furniture in last.

by VS126 on Wed Mar 24, 2010 5:44 pm

Not everyone will agree with me but thru experience, you can put a well designed speaker in any reasonably sized room and it will not boom. Clean controlled bass in rooms in small HDB flats in Singapore using state of art big high end floorstanders and massive power amps.
Why doesn't the speaker boom???
Majority of Harbeth speaker booms. Even the one in the local agent's main room using HL5 booms. The KLIAV Harbeth room booms like crazy. Maybe to some...it is good sound.
Once you have listened to well designed speakers, you wld not be able to tolerate the boom. I am not only saying Harbeth but it is just coincidence that the few friends I have with so called 'room problems' are happy after they change to other speakers without touching their room.
Even Cardas cannot help.

YMMV.

by **WongKN** on Wed Mar 24, 2010 6:49 pm

True to an extent. But at what cost ? A speaker that betters the Harbeth may not come cheap. I have heard an Apogee Diva played in a room of size 10' X 12' X 10' and not only does it not boom, it's sound was heavenly, driven by Audio Reseach D-250 Mark-2. But the Diva cost a lot more than the Harbeth, even used.

We need to give Lamkochai some respect as an audiophile, meaning as always, I am assuming that he knows about system set-up, together with speaker placement, and thus have already tried his best to cure the boom with speaker placement, etc (putting them at the 1/3 positions- 6.5' from rear wall, 3' from side wall, etc). Personally I myself would not ask for help from a forum if I have not tried everything I can.

When this scenario is correct, then I am afraid using some massive household object to break up the sound waves or the absorb the low-end frequencies is the simplest and probably cheapest way. Thus the suggestion to try the sofa. I much prefer such domestic approaches rather than buy acoustic foam and similar stuff from the hifi shops. Those really hurts the wallet.

Something I am VERY SURE works is to build a large Helmholtz resonator box. This is guaranteed to work because it is based on physical law - the Helmholtz resonator absorbs bass at a fixed frequency depending on the dimension and design of the box. My friends and I have cured an extremely bad booming room - Sonus Faber Extrema driven by Krell KAS-2 monoblocs, using Helmholtz resonators - several of them.

But before going this drastic way, a no-cost way, again assuming set-up like speaker positioning has already been tried, is to just lug furniture into the listening room and listen for their effects. If it works, then it gives us a direction on how to fix the problem. The approach can then be discussed. So in the first place, we NEED to confirm that the cause of the bass boom is room resonance. Then only we can be confident that the next steps are the correct ones.

by VS126 on Wed Mar 24, 2010 7:36 pm

Not hugh costs, like mega bucks flooestanders.

A simple drop in bookshelf using same speaker stand (same position) from Harbeth to ProAc/Sonus etc. immediately cured the problem. If LKC do not believe, he can ask Penang CMY to do a home demo using ProAC or other similar quality / size bookshelf speaker.

I am not a Harbeth hater or ProAc lover and not associated with anyone. but I am talking from experience. Maybe the Harbeth is designed tis way, that the cabinet acts as an instrument and not supposed to be well braced. This cld be the problem.

I hope I do not offend anyone esp. Harbeth lover and if I do....my apologies.

You know the problem with yr speakers. Not easy to tame.

As always, YMMV.

by uncle_vic on Thu Mar 25, 2010 1:07 pm

One question(related to boom of course). Will taming the boom or reducing the boom or removing the boom result in less bass?

by tycham on Thu Mar 25, 2010 2:02 pm

uncle_vic wrote:One question(related to boom of course). Will taming the boom or reducing the boom or removing the boom result in less bass?

I would say yes if you replace a full range to a bookshelf. Not only less bass but also less sane. lol!

by **WongKN** on Thu Mar 25, 2010 2:41 pm

Well, we had a discussion before: us and Lamkochai. Back then he had a weak amp which cannot drive the Harbeth and he was asking for more bass. Now he has a more powerful amp and it gives him too much bass. Back then as well, he was given two main suggestions : change amp or change speakers. He opted to change the amp. This means that he has already considered the option of changing speakers and have decided, for whatever reasons, that he will keep the Harbeth. So would it be appropriate to tell him to change the speakers now ? If he had wanted to change to a bookshelf, I would think he would have considered keeping the original amp and changed speakers then.

So now we need to work with his situation in our suggestions. I.e. the speakers will stay. Given that, I feel there are two main possibilities,

1. The room obviously is not ideally dimensioned. So there could be lots of bass resonance. Such rooms are actually very difficult to control, if at all possible. The only way which doesn't cost a lot of money is to start putting stuff inside to break up the resonance or the absorb the bass.

2. Actually the current amp is not exactly that powerful, so one of the problems could well be that the amp is not able to completely control the Harbeth. When such a condition happens, the speaker will have uncontrolled and boomy bass. Perhaps this is also happening to an extent, which is being worsened by the room itself.

This is the gist of problem solving. First we HAVE to identify and confirm the cause of the problem. It's no point shooting in the dark at all the possibilities. To identify the cause, we need to understand the situation and think about possible causes. Then we need to test each option to try our best to confirm which is the correct cause. ONLY THEN can we start talking about solutions.

In this instance, to identify and yet avoid spending lots of money is to first test each possible option. If its room, then putting common household things in to break up sound reflections or absorb bass is to me, the most straightforward and free way. If it works, we can confirm with a large degree of confidence that the room resonance is indeed the problem. Then we can move on to the solution. THEN only we should start talking about audiophile solutions and about spending even more money.

If it does not, then we need to look at the other possibilities.

1. Amp still cannot drive Harbeth properly.
and also other less likely possibilities
2. The speaker's inherent characteristic is boomy bass.
3. Something else is causing the boom.

We need to work down the list. But we need to start somewhere and the most efficient way is to order the list according to highest probablility and in this instance, the room resonance is indeed the biggest possible culprit.

Note there can be secondary causes as well but in order not to go insane, its best to work 1 at a time.

by ryder on Thu Mar 25, 2010 3:28 pm

I reckon the bass boom experienced by Lamkochai is 99% due to room issues and not speakers. With a proper room with reasonably good acoustics Harbeth speakers will not boom. Nonetheless, I have heard several Harbeth setups including some of my friends which do exhibit some bass problems. Of course Lamkochai can try another speaker in the same space but I suspect the bass boom will still be there. If he tries a small bookshelf with limited bass output then his problem would be solved. Room acoustics can be a tricky thing especially when the setup is not in a dedicated room.

by ryder on Thu Mar 25, 2010 8:40 pm

Lamkochai, I presume you have seen the system below on Audiogon.

http://forum.audiogon.com/cgi-bin/fr.pl?vevol&1176687829

His room dimensions are almost similar to yours at 16'x21' and he is using the 40.1's. His room is treated with 8 pieces of GIK Acoustics bass traps. Carpet floor throughout. Just thought you might be interested to contact him on the effects the traps brought to his system. His response might give you an idea that can possibly relate to your dilemma. Not promoting any product here as GIK Acoustics products as with most room treatment products cannot be found here.

Alternatively, you can place your system in another location or in your bedroom. That will give you a rough idea how the SHL5's will sound in different rooms. By the way, I feel that the SHL5's in Sam's showroom exhibit some bass boom as well although you feel there isn't any.

Cheers.

by car o scope on Thu Mar 25, 2010 9:07 pm

Lamkochai maybe very busy with his room experiments now.. hahahahaha.. Razz

I have to agree that controlling bass is very tough.
Nevertheless, keep doing experiments with those things that are available at home and dont have to spend money 1st.

by Bite on Thu Mar 25, 2010 9:49 pm

Approach mapped out by WongKN is logical and methodical.

I have 2 Harbeths, a bookshelf and a floorstander. Let me say, I find no purposeful need to protect Harbeth nor my past decisions to buy 2 well built violin cases.

The bookshelf doesnt give me any problem with bass while the floorstander does. I suspect, in mid bass though not as accute as the other floorstanders I have had in my hall in the past. I am not sure whether the SF Amati, Ellipsa, Cremona, Sophia 2 qualify as well designed speakers and if they do, then they did give me the same problem as the Harbeth floorstander and then again, some.

Some rolls of roofing rockwool has helped mop up some of the problem but not totally. Yes, you need mass.

In my view, room or equipment mismatch is more likely the problem rather than speaker design.

by Lamkochai on Thu Mar 25, 2010 11:15 pm

2 days without internet suddenly so many responses to read. Thank you all for the suggestions. they are all informative and fun to read. And yes i have tried the straw thing but unfortunately it doesnt help.

it seems now my room is the main culprit for this bass boom. i have tried various positioning but really cant help much regarding this bass thing. I believe the current placement of my harbeth is the best i could get in term of bass, resolution, sound staging and depth after almost 1 year trial..

I have tried connecting to my other pair of speakers i.e proac studio 125 and my cheaper monitor audio bronze but the prob persist. I think my current amp should be powerful enough to control the harbeth because i have seen it paired with the more difficult sonus faber cremona floorstander without problem (and quite a taut bass too).

I plug in some foam into my harbeth bass port to change the bass frequency roll off. it helps a bit but the overall sound is so dull that music become lifeless.

My auralex LERNDS bass traps does not help much either but may be the placement is not correct. I currently put the bass trap at the corner behind my speaker and corner behind my listening position. Anyone here can give me advise the best place to put these bass traps?

What about those resonator sold by CMY? will it help in term of bass? I cant really put more ugly looking bass trap

at my main hall.

I will put up more photo of my listening area when i am free so that you all can provide me with more useful opinion.

by Lamkochai on Thu Mar 25, 2010 11:24 pm

BTW, I have no regret changing my amp. It really sound 100% better than my previous one despite the bass prob. It also prove that my previous amp is too small power for the harbeth and at least now i more or less confirm the bass prob is due to my room.

by **WongKN** on Thu Mar 25, 2010 11:39 pm

Lamkochai, my experience with 'bass traps' are that often they are designed to FINE-TUNE bass response and at most to tame very mild bass boom, not the serious ones.

One thing you can try on the internet. Google around for sites which deal with design and building of recording studio. Now, controlling the acoustics of a recording studio is crucial and the bass resonance especially critical. Visit a few. Those that I visit, many of them give architectural plan for the studio and almost all of them will give you a design for a Helmholtz resonator in the studio. Now take a look at the dimensions. Often the resonator is the size of an ENTIRE WALL, with depths of a foot or more. This is the kind of size and mass we are talking about to really really control and tame bass. So all those tubes and boxes and stuff we get from hifi dealers, like ASC tube traps, Roomtune bass tune, etc, they are all for FINE-tuning the bass response. They absolutely DO NOT work for a bad room boom.

I have ample experience with this with a close friend's system. We (the group of us) took months to tame the boom. I build a prototype Helmholtz resonator which we could hear effect but very mild. Then we got a carpenter to build SEVERAL of those. It helps but the bass response was still uneven. Finally one of the guys in the group was free to drop by the room. He is an acoustic sound engineer. He went with another engineer and together they worked out some formulas and finally thrpugh their advice we had to resort to professional concert hall panels to even out the bass response. We had to use several panels, each panel 7feet by 3feet H X W and around 4 inch thick. There were 4 in the corners and two more at resonance points on the side wall. This is the extent to which a bad bass boom can be properly tamed. However, my friend has a dedicated listening room. You are using your hall. So I am afraid you don't have the same luxury, even if you can afford those professional concert hall acoustic panels.

So, based on that experience, I am afraid you may have no choice but to start putting more stuff into the living hall. You may not have a choice.

However, before you despair, try this experiment. Play a CD and especially the track with a long boomy music. Put on repeat if you have to. Now move to various positions within your listening room/living hall and note the bass response in those positions. You might well find that some places sounds extremely bad and some places may even not have much bass. Remember to try as many positions as you can - various positions in the middle of the room and various positions at the side walls as well as the corners. What you are trying to do is to locate the various nodes in the room - resonance or reinforcement nodes, and cancellation nodes. Try to note down on paper and a diagram of your room, the various positions as accurately as possible. You might even want to use sticky tape and temporary mark those positions which are reinforcement points and cancellation points. Then you show us the diagram and perhaps we can progress from there (what things to put where and perhaps where to sit, etc).

by mugenfoo on Fri Mar 26, 2010 12:18 am

there was a website somewhere that exposed the ineffectiveness of Auralex foam LERND basstraps... can't remember where but remember seeing the test results of it before.

Basically to trap bass, simple foam surfaces are usually not suitable for it. Without going into the geeky technicalities, one needs to look at cavity resonators (i.e. HelmHotz resonators) that can effectively transform bass sound waves into mechanical movement (change the sound energy into kinetic and heat energy).

Furthermore, Helmhotz resonators, when placed correctly AND tuned correctly, will only absorb the specific BOOM freq without overdamping the other bass freqs (high Q-factor).

Otherwise, the other altenative would be to physically "change" the room dimensions via the use of thick bulky and dense panels. Something akin to those 7x3 feet + 4inch of whatever damping material as filler mentioned above.

Or putting more "stuff" in the listening area will also help to distort the 10x15x20 dimensions... Like Ikea Billy/Bonde bookshelves braced against the walls, a big thick padded & comfy leather couch, and even some big bean bags for the corner locations will all help to even out the bass booms. Basically big physical stuff that will break up the standing waves.

Just don't go overboard, or the overall bass will suffer and the room/system will screech like a tweety chirp or a nasal squawk with no bass slam and dynamics.

by Lamkochai on Fri Mar 26, 2010 7:26 pm

for the past 1 year i have tried various positioning of speakers and listening positions. the bass is least boom when i sit just in front of the back wall with the speakers around 1/3 out in the room. but then the imaging is smeared due to (what i think) flutter echo of other frequencies and my room is very messy so i revert to my current position.

thank you both for the theory. I have forgetten most of my physics since my STPM days but your explanations are scientifically logic and true. I guess nothing much i can do now except changing my listening room.

Overview of my listening area taken from listening position

Left wall. Behind the curtain is mainly glass. note the dead space over there. i put Auralex LERNDS in front and at the back of speakers as advised by Sam (harbeth dealer).

concrete ceiling. planned to paste some bass trap there later but my hall will be very ugly.

another view of the ceiling. note the brass plate used as resonator. these plates work wonder in lifting the soundstage.

right side is opened to dining area, kitchen and staircase to 1st floor.

what i am doing now for some of the track to reduce bass boom. item used is xray film to prolong the port. I dont know how it work but i guess it changes the bass response curve of the speakers and thus reduce the resonance bass note. sound more natural compared to putting foam into the port.

by **WongKN** on Fri Mar 26, 2010 9:45 pm

Lamkochai,
Strictly speaking the standard box speaker enclosure is itself a sort of a Helmholtz resonator. The HR's working paramters are internal volume of box, diameter of port opening AND the length of the tube of the port. So your experiment with the X-ray film is actually varying ONE of the paramters of the Helmholtz resonator which is the enclosure of your Harbeth. If you find a more solid tube which fits exactly into the port, you can actually change the length of the tube to change the characteristic of the HR. Speaker manufacturers tune their enclosure partially by the port, which is why different speakers have different port sizes and also different length of the port tube (the tube extends inside the encolsure). So what you are doing is increasing the length of the port tube.

There is a very simplified formula which lists the frequency absorbed by a set of internal volume + port diamter + port tube length. But I lost that formula. I think you might be able to find it by googling (the internet is fantastic for finding info such as this).

Did you try going around to different places/positions in your room/hall and note where the reinforcement and cancellation points are ?

by **WongKN** on Fri Mar 26, 2010 9:47 pm

Also, did you try taking out the pair of speakers behind the Harbeth ? It may improve or worsen the boom but you don't know until you try.

by ryder on Fri Mar 26, 2010 10:28 pm

It is funny you experienced bass boom and described the bass as too overwhelming and uncomfortable. Judging from the pictures above, it appears that the speakers are placed out from wall boundaries and there isn't any wall on the right where the dining table is sitting at the far end. I would imagine the bass to be loose and lacking punch and impact with the free space on the right. You have experienced otherwise. If you are getting too much bass, I suspect the dead space on the left may be contributing to some of the bass boom. Have you tried moving your speakers further to the right, say 2-3 feet? I would also lose the CRT TV and add a rug on the floor. You can try placing the diffusors on the front wall behind the TV, only after the TV is moved somewhere else. I feel you have too much stuff behind the speakers, and similarly like WongKN think you should experiment by taking out the Proac speakers apart from the TV just to see if there is any difference to the sound after they are removed.

by **WongKN** on Fri Mar 26, 2010 10:51 pm

There seems to be a solid state power amp inconspiciously hiding behind the left speaker. What amp is that and how much power is it rated at ? Did you try powering the speakers with that amp to see if the same bass boom problem exists ?

by - br@d - on Sat Mar 27, 2010 1:12 am

WongKN,

I think that's a power regulator ..

Lam,
Looking at your pictures, I strongly suggest for you to invest on a shaggy carpet from Belgium around RM500 - RM800 to cover your reflective floors depending on size. Cover your coffee table in front of you with a thick fabric table runner or cloth

Replace your silver reflectors near the glass sliding door to Rockwool panels. You can actually DIY and its cheap too. Below are some DIY work I did for the Hifi Room. Now Boomy no more

by mugenfoo on Sat Mar 27, 2010 1:31 am

those aren't silver reflectors ... they're RPG skyline (actually the local copycat version) primitive square-root diffusers.

And they don't seem to be used properly as well.

They should be rigidly mounted against a wall surface or ceiling frame. And they should be "oriented" the same way throughout.

by - br@d - on Sat Mar 27, 2010 1:40 am

Ok my bad bro. Diffusers It is then

by mugenfoo on Sat Mar 27, 2010 1:43 am

lamkochai , go buy this book .... the holy grail to solve your bass boom lies somewhere within its pages.

But take note, this book is not cheap, and you might need to brush up alot of your STPM matematik and Fizik knowledge to fully appreciate it.

Accoustic Absorbers and Diffusers: Theory, design and application.
ISBN: 9780415471749

Then u can go about DIY'ing your own homemade whatnots or at least buy the proper treatment devices in your quest for sonic excellence.

by Lamkochai on Sat Mar 27, 2010 8:23 am

thanks for all d suggestion. since this is not a dedicated room, all my diffusers and foam is not fixed there. i will put there while listening and remove them afterwards. i am afraid i cant move away my proac speakers either. really no other more suitable place to put them. may be ryder is correct in some sense regarding loose bass due to free space at the right.

wow, the book u recommend cost usd 140 at amazon!! does anyone here got this book? pinjam for photostat lo

at least its not that painful in case i cant finish it due to time constrain or comprehension problem..... or we kongsi duit buy the e-book and kongsi password then everyone has the opportunity to read it...

by **WongKN** on Sat Mar 27, 2010 10:32 am

A couple of things to try:

1. Just move the ProAcs out and see if there's any change. As they say necessity is the mother of invention. If moving them out improves the boom, then you -will- find somewhere else to put them.

2. Did you try listening with the two corner treatment on the left wall and without the diffusors ? Those kind of room treatment actually affects the midrange more than the bass. And sometimes we unconciously reduce the midrange energy so much we have to turn up the volume and that could increase the bass. i.e. we unconciously create a midrange suck-out (think of the 'legendary' graphic equaliser where everyone eventually sets the two extremes to max and the middle to min).

I also second put something thick and soft to cover the center table. Just to try.

And finally, I would strongly urge you to go round the room and listen to the various places for bass reinforcement and cancellation. I believe that move will give us the next concrete step for control of your problem.

When we have a problem like bass boom here, it is important to try everything to see if it is the cause, or if it helps. Irregardless of how impractical it is. The critical thing is to try to locate something that causes it or the improves it. With that, then if it is not practical to implement it (e.g. like you say, move the Proacs out), then we can consider ALTERNATIVES, e.g. perhaps we can try covering the front of the proac with some solid plank or foam or whatever, or turn the Proacs the other way round, etc. But FIRST, we -must- remove the items totally to see if they are the cause.

But beyond all that, first you need to try to locate the bass reinforcement and cancellation points in the room. That I believe is the most critical first step you need to do now. You might need to do things like removing that table in the middle and sit there to hear the bass. Or put your head there for a while. It is important. If you don't do that, then I am afraid you will just be shooting around randomly in the dark.

by Lamkochai on Sat Mar 27, 2010 11:25 am

hi wong
i have tried the moving around trick. like i said earlier the boom is least when my speaker is 1 feet forward to its current position and my sofa have to shift till my back touching the back wall. but then the whole hall is too messy so cannot get 'home minister' approval.

and yes i have tried removing the bass trap and the boom is more. the only thing i havent tried is to remove the 2 proac speaker but the they are not there when i first bought my harbeth. the boom was there since the first day of the harbeth.

i do think that the coffee table does contribute to the boom but my wife doesnt allow me to shift it out........ thats why i place some books and files within it and put a cloth on top. thick foam on the coffee table is a no no to my wife too...

basically i have tried a lot tricks i obtained from internet. out of all the tricks the most notable changes are noted from adjusting the speakers and seating position like what you suggested.

initially
i thought of buying more bass trap and put at the corner of my ceiling but based on what you all say i think it wont help a lot so i wont waste more money in it.

thank you all anyway for all the suggestions.

by **WongKN** on Sat Mar 27, 2010 1:08 pm

Actually I was more thinking about a technique I learned from someone whom I visited a few years ago. He located the reinforcement points in the room for the bass and he placed things there to -interfere- with the reinforcement. This creates so much interference that the bass sound waves just cannot concentrate/focus properly and as a result, the bass boom is controlled. This is the other technique - a sort of 'prevention is better than cure' approach. We are all used to trying to ABSORB or CONTROL a bass boom AFTER it has been produced. But that owner taught me that occasionally we can interfere and PREVENT the bass boom from happening in the first place. It's like the concept of healthy living with proper eating to avoid falling sick, rather than not bother, fall sick, THEN only go to the doctor to get medicine to cure the illness.

My intention of harping on finding the resonance points is that I can see those diffusors and such in the room which originally I thought "how could his wife have allowed him to put it there ?". Then you said you put those things there when listening and take it out after. So what you can do is to put traps or thngs to interfere with the bass reinforcement nodes (as they are called technically) when you listen. So you might have some ugly things sitting around various parts of the hall. After you finish, you just take them away lar.

But it's like I said, the MOST IMPORTANT thing is to first find the way to tame the boom. After that, we can discuss about the approach/strategy to implement it but in a domestically acceptable way.

by mugenfoo on Sat Mar 27, 2010 7:32 pm

WongKN wrote:Actually I was more thinking about a technique I learned from someone whom I visited a few years ago. He located the reinforcement points in the room for the bass and he placed things there to -interfere- with the reinforcement. This creates so much interference that the bass sound waves just cannot concentrate/focus properly and as a result, the bass boom is controlled. This is the other technique - a sort of 'prevention is better than cure' approach. We are all used to trying to ABSORB or CONTROL a bass boom AFTER it has been produced. But that owner taught me that occasionally we can interfere and PREVENT the bass boom from happening in the first place. It's like the concept of healthy living with proper eating to avoid falling sick, rather than not bother, fall sick, THEN only go to the doctor to get medicine to cure the illness.

My intention of harping on finding the resonance points is that I can see those diffusors and such in the room which originally I thought "how could his wife have allowed him to put it there ?". Then you said you put those things there when listening and take it out after. So what you can do is to put traps or thngs to interfere with the bass reinforcement nodes (as they are called technically) when you listen. So you might have some ugly things sitting around various parts of the hall. After you finish, you just take them away lar.

But it's like I said, the MOST IMPORTANT thing is to first find the way to tame the boom. After that, we can discuss about the approach/strategy to implement it but in a domestically acceptable way.

The idea is there, but the wrong theory about prevention vs. cure is being put to use here.

How these Basstraps, HH resonators , Auralexes, etc work is that they stop the standing waves from forming and hence prevent the boom in the first place.

The notion of prevention is better than cure doesn't apply here because the very act of deploying acoustic treatment stuff (assuming they're effective) would already stop these bass booms from forming.

Quick lesson in wave physics:

Here's how all these acoustic stuff works. They don't work the other way around , i.e. absorb the boomy boomy boom boom bass after they're caused by the room excitations. Walking around the room to "listen" for "problem spots" merely identify what is called "nodes" and "anti-nodes" of the standing wave.

For example, let say lamkochai has a boom at 200Hz (for example), He can inject a 200Hz test tone to play via the system, then walk around the room with a SPL meter to measure the dB level. At the spots there the SPL reads the strongest, these are the anti-node points. At certain location, the test tone would measure the lowest (and sound the quietest); these are the node points.

it is pointless to deploy "bass traps" at anti-node locations just to "absorb" these supposedly problem spots. The proper way to fix this problem would actually be to identify which surfaces are responsible for the buildup of this "200Hz" standing wave, and treat accordingly. Either make the surface absorb the coincident wave coming from the loudspeakers itself, or deploy some diffusers to scatter the wave such that it doesn't mirror-reflect into a standing wave.

But bear in mind, the speaker placement would affect where these nodes and anti-nodes appear around the room. But the boom freq stays the same.

What most people perceive as boom means that their listening position is nicely parked right on the spot of a particular standing wave's ANTI-NODE point. Hence the nasty boom. If the reverse is true (you're sitting in a NODE point) you'd hear a "suck-out effect" of that particular frequency instead.

Somehow, by psycho-acoustics, the human ear is much more tolerant of suck-outs than booms. Booms come across as being really annoying whereas suck-outs could be misinterpreted as "that's just the way it sounds!" syndrome. Either way, it's colouration and a deviation from the original intended sonic presentation.

So for a real-world listening room/hall ... its always a compromise to position the loudspeakers AND sitting position to give the best combo of the following results:
- sharp focused stereo imaging
- generous and realistic soundstaging
- smoothest freq response

You might find a spot in which you don't hear almost any booms (ala Ris Low style), but it could be really bad for imaging and/or soundstaging.

Likewise, you could find that magical "first class ticket seat" position in your room/hall for most music being played... but certain musical pieces are totally unacceptable because that spot that gives u the best imaging and soundstaging also comes with annoying and irritating booms at certain freqs, is more often also a place where a few nasty anti-nodes decided to form there as well.

by **WongKN** on Sat Mar 27, 2010 7:59 pm

The principle of what you are talking about is exactly what is being practised in that procedure. Only thing is most people start and concentrate on the walls. But the person I learned the technique from also tackles the resonance points as well. Bass frequencies can be very powerful and it is often futile to try to prevent reflection of walls totally. Using commonly available things, even so-called audiophile room treatment, it is frequently a futile exercise to try to really prevent reflection by a very significant amount. Those acoustic panels my friend got, they are supposed to be professional materials, not available from places we audiophiles would frequent or know about. A big problem with 'professional materials' is that they are almost always bloody expensive (as in we pay until blood comes out !!

)

So the person whom I learnt the technique from, reinforces wall treatment by using artifacts to try to break up those resonance points that still forms after trying to prevent the waves from building the resonance points in the first place. This is why sometimes we see people who puts a stool somewhere in the room. Or sometimes we see someone with a pile of books at another place. And we ask why they are there and the person says somehow by putting those things there, the sound improves. He doesn't understand why and how but he is surely going to continue putting them there if he can do it.

So in the end, it is most important for Lamkochai to understand the basic principle and then he can evaluate if he wants to try it and if so, hopefully he will be able to tackle the problem. FWIW, I fully support the prevention is better than cure approach I learned from that person. Others of course will have different opinions and may get different mileage out of it.

by tlkoo on Sat Mar 27, 2010 10:12 pm

mr mgf

care to show the applications to benefit most of us

many thanks in advance/regards
tllkoo