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Room Acoustics/Bass Boom - Please Advise

Discussion in 'Room Acoustics, Audio & Video Calibration' started by craigd, Feb 21, 2007.

  1. craigd

    craigd Member

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    Dear All,

    I have recently moved in to a new house (please see the attachment). I have set my speakers up taking all the usual precautions to reduce bass boom:

    - Using spikes
    - Room is heavily furnished
    - Front Speakers have bungs in rear ports
    - Speakers have plenty of space around them

    However - I am still having problems with the bass, even without the sub. I need a WAF friendly solution to this that is cheap. I cannot alter the seating position or speaker postions by more than ~10-20 cm in any one direction. The main concern is getting the fronts sounding good as I listen to a lot of stereo music.

    From reading up on it I understand that the RS8's have a peak at 80Hz and my room has a resonance at that very frequency.

    Any advice would be appreciated.

    Attached Files:

  2. mattym

    mattym New Member

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    its a pity you cant turn it round so your speakers are firing down the room, that might make a big difference. Try moving the sub if you can, though im not sure that will make a huge difference.

    Treatments available....well its cheap foam that wont really work below 100/125hz(despite what you may read on ebay) or thicker, more specialised traps. DIY bass traps from fiberglass or rockwool would be one solution, but not really what you would call WAF, commercially available units would be the same, though there are a couple of metal products that are supposed to blend in a little more....
  3. spooney

    spooney Member

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    You should try to change the position of the sub.

    In every room there are certain frequencies were the sound waves built up.
    This is especially a problem with very low frequencies when they are reflected between the walls.

    This is a very complex topic but you can do some simple maths:
    344/lenght or width of room in meter will give you the frequencies you have to look after. Btw: 344 is the speed of sound.

    Edit:
    Just saw your picture: You room will resonate at 86 Hz and 43 Hz.
    Your sub is exactly in the corner and at these frequencies you will hear a good boom.
    Maybe your sub is equipped with frequency control and you can lower the level of this frequency?
    Or simply move it towards the center speaker?
    As mattym wrote a small move could make a difference.



    Disclaimer: Before somebody jumps at my neck to start a discussion around down fire subs and the 1st, 3rd and 4th mode. Yes, I know but let us keep things practical and simple for the sake to find a quick solution. WAF is at danger here and this has the highest priority ;)
  4. craigd

    craigd Member

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    Than ks for the response - I can sort out the sub later though - is their hothing I can do wrt the Front Speakers - position wise?
  5. mattym

    mattym New Member

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    Spooney's got the cheapest solution there, a quick way to find a good sub postition is to place sub at listening position and move around the area you want the sub to go(at sub height), you will find pockets where the bass sounds the best, thats the best place to put the sub.
  6. craigd

    craigd Member

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    I am NOT TALKING ABOUT THE SUB! I listen to my music in pure direct mode - i.e. the sub is off!
  7. spooney

    spooney Member

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    In this case you have the same resonance problem but more difficult to solve.
    If you can't move them the only way would be as mattym said quite big sound treatments or to lower the level at these specific frequencies electronically e.g. with an equalizer as a workaorund or a special circuit filtering these frequencies.
  8. craigd

    craigd Member

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    Is there a device I can put between the amp outputs and the speakers to do this? I was under the impression that usually you would put a GEQ between preamp and power amp, however I have an integrated amp. Is there anything you can recommend, at a reasonable price?
  9. spooney

    spooney Member

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    I read something a while ago but I can't remember where and when. Sorry.
    Maybe the guys in the sub woofer forum could give you a hint for something external?

    The potential problem with an EQ is you can not impact a specific frequency. Still this might be the solution.

    You will need something to lower the impacting frequencies by 3 or 6 db after recaclulating them for your front speakers.
    Basically you will need a coil and a condensator with a certain capacity.

    Best and most expensive of course would be a professional calibration which would put in a DSP to consider all your room specifics.

    I am currently transfering my old tapes to CDs with the aid of a sound cleaning and refurbishing software therefore I am currently a bit into this topic ;)
  10. Resonance

    Resonance Member

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    An SMS-1 or BFD would do this. Do a search in the subwoofer forum. There has been much discussion on this. These devices are basically parametric equalisers, i.e. you can entirely set the frequency, the gain (+ or -) and the bandwidth (i.e affect a broad range or frequencies or just a very narrow set).

    If you have a tape monitor switch on your amp you can connect the EQ in the tape loop, or if you have pre-out and in, socket you can use these. Otherwise you can connect it between CD and amp.
  11. Dominic

    Dominic Member

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    i used a piece of free trial software, realtime spectrum analyzer on my laptop with external mic, then ran some freq sweeps with a test calibration DVD and noted the peeks/ troughs, then had to battle with the room shape the practicalities of sticking the sub on the coffee table :) and the wife... so you end up with a comprimise, sadly in the favour of the other half...:mad:
  12. craigd

    craigd Member

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    How did you calibrate the MIC - I understand frequency response is non linear especiaally at bass frequencies with cheap MICs.
  13. Dominic

    Dominic Member

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    i guess that didnt come into it, :oops: it wasnt a particularly expensive mic, it was ony 19.99 from maplins, just one i had to hand from my karaoke kit.
    It seemed to do the trick, the battle is down to what sounds good to the human ear, and what looks good on a spectrum analyzer, its not always easy to keep the wife happy too.
  14. spooney

    spooney Member

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    And this is exactly why I have given up the battle you never will win and built my home cinema room into the basement. No wife thinks this is cool and she invites her friends for some chick flicks to brag with the room and equipment :thumbsup:
  15. Rob Sinden

    Rob Sinden Active Member Assured Advertiser

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    The three accepted methods of sorting this out would be

    1. Use some equalisation. Something from Berhinger would probably cost you no more than £150 and would give far more accuracy than things like the SMS unit.

    2. Use satellite speakers as per THX, PMI and HAA recommendations. This would obviously be reliant on getting a sub performing well, but with the bass managemnet in your amp this is definitely worth persuing as you already have all the kit to do it.

    3. Use some far more sophisticated room correction like what Denon, Onkyo etc. have from Audyssey.
  16. pwood

    pwood Member

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    I think some of the blame is with the MA floorstanders. Dont get me wrong they are excellent speakers but I have experiance of RS6 ones in a friends room which has a problem as well but a pair of my Ruark Talismans floorstanders( which can be mass loaded) did not boom although they dont punt out as much bass as the MA's.

    One tip which is cheap is to put them on marble tiles which can make them sound more forward but can help boom a bit.

    I know you use pure direct mode but try setting your amps crossover to a higher freq which will shove more of the low end to the sub less to the front speakers and see what effect it has on the bass boom. It may point more to the speakers being the culprits.

    Certain speaker cables can reduce bass overhang but I would doubt it will make much odds unless you are using a particulary poor cable. Besides you would be masking the problem not curing it.

    BTW do you find there is more bass over in the part of the room where there is no Hifi ie right hand side I have a similar layout and this is the case in my room.
  17. Member 96948

    Member 96948 Active Member

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    Nobodies picked the obvious one. The speakers are quite simply too large for his purposes, given the orientation of and placement within, the listening room. RS6s maximum.

    If the OP insists on 'Pure Direct & no sub' only approach to music listening, then it's the only option left open. Better to get the right speakers in there, than trying to make the wrong ones work.

    Russell
  18. craigd

    craigd Member

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    Its pretty much sorted now thanks guys. I had a mate come over who is pretty expert in music production type stuff and has a very good ear. With some experimentation we found that ditching pure direct mode totally and setting the crossover to 40hz using pure direct mode. I was a bit stuck on using pure direct mode which, although may give a slightly better sound at higher frequencies, meant the bass sounded too boomy.

    I have moved the SUB to in between the two fronts. I have even removed the bungs and with the the sofa pulled forward another 3 inches out from the wall - it sounds great. Bass is much better defined now - even with the sub off and using the high-pass filter just to chop stuff below 40Hz has improved the sound greatly.

    I am already in the process of buying some granite slabs to go under the fronts and the sub so this should improve things a bit more - my initial quote was £120 though - I am now looking to do a cash deal on some offcuts!
    I have purchased some solphathane pads to go under the granite to stop the floor vibrating so much.

    Thanks for your advice guys.
  19. mattym

    mattym New Member

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    moving stuff around sometimes is the easiest thing to do
  20. pwood

    pwood Member

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    Try a couple of standard floor tiles first someone is bound to have a couple lying around.£120 is a tad excessive especially when you dont know if it will do the trick.

    I'm glad using the crossover worked for you. Its all a bit confusing I agree.
  21. craigd

    craigd Member

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    I thought it was worth following this up as I have now resolved my bass boom issues and thought it may be of interest to some of you.

    I must apologise for banging on about how the sub had nothing to do with it because I listen to music in pure direct mode. Unfortunately, I had fallen into the trap of obsessing about 'pure direct mode' which does, of course, improve the top end but has negligible effect on the bottom end.

    I borrowed an SMS-1 from my local dealer - improved things by a massive amount, but £575 is a bit steep! However by using the unit without the EQ i managed to flatten out 20Hz - 80Hz to +/-2dB! After changing my crossover from 80Hz to 60Hz (and using this for stereo playback too), changing the sub position and phase and moving around the fronts I managed to improve the bottom end dramatically. I have returned the SMS-1 that I had on loan, much to the disappointment of my dealer.

    Also, I have some very heavy slabs of graniteon order which should stabilise my speakers and (with the solphathane pads) stop the wooden floor vibrating. I ended up paying £90 for 3 slabs - not bad.

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