Bad room acoustics.

The solution is easy,Russ Andrews is 101% wrong.Isolation won't do a thing,nor will cables.What you need is room treatment.Your room is live,reflective.....it needs taming.

You can do this by room treatments,the easiest way is more furniture,curtains,and a thicker carpet,or you can buy or make specialist treatments,for your problem you need to find what freq is causing the problem and treat it.

Remember you will need broadband absorbtion to trap as many freqs as possible,bass traps in all 4 corners of the room,absorbtion at all your first reflection points,you can use specialist fire proof foam,or make your own using rockwall,or fibreglass at about 10cm thick,60cm W X 120 length.

place them at first reflection points and behind your speakers,then hear the difference.

Yup, agree. Isolation may firm up the bass a little, but it ain't gonna remove the boom. And yes, it's acoustic treatment that you need. Just take note that the usual eggtray foam stuff is too thin to have any effect on the bass - they're useful to absorb echo though. The bass traps have to be much thicker and denser to work.

Check these out:
http://www.hsfacoustics.com/studiopacks.htm

If all else fails, take drastic measures and plug the bass ports with the foam bungs but personally, I feel that the sound is very constrained with the bungs in place.

 Thanks for the help, cheered me up no end. On the subject of room reflection,how do you work out where your weak points are?

Have a friend with a mirror stand to one side, when you see the tweeters in the mirror, that's the first reflection. Do the same for both speakers.

 In our previous house, the lounge where the hifi usually resided had a suspended floor over a cellar and the back dining room had a solid concrete floor.

If the missus was away for the day,i used  to move the cd,amp and speakers into the dining room  and for a few hours at least i had the sort of defined,solid deep  bass we all aspire to!

I suppose the concrete reflected the bass back into the room whereas the  wooden floor allowed it through into the cellar never to return.

Now,i'm not suggesting you fill the void under your floor  with cement but what it does prove is that the only way to audition speakers ,is in your own room with all  the alcoves,bay windows,chimney breasts and suspended floors etc that you never see in your dealers perfect dem room!

Even with your system placed in a symmetrical room, it's often the luck of the draw whether you end up with too much bass or too little bass. If I had to choose, I would go for the first one because it's still possible to treat. However, I have experienced a room with bass cancellation issues that is just impossible to get any decent bass in, no matter where I placed the speakers or moved the listening position. Absolutely frustrating!

You can actually treat a room that has a bass suckout using bass traps, people think that a bass traps just traps too much bass,whereas it actually can also help keep bass in the room, i'd rather has too little than too much, as bass I guess is the sound that annoys most neighbors.

 I'd also go for sealed designs. Bass reflex, no no.

follow the link below, many found the unit does help a great deal:
http://www.enjoythemusic.com/magazine/equipment/0705/behringerultracurve...

I dont recommend a Behringer,it's just a plaster, it can only measure from where the microphone is placed, so it will only treat the listening position, not the room, it can't cure many problems that can found in room, most people who buy these products tend to sell them quite soon afterwards.

If you are using it between transport and DAC it will become one truly amazing equipment! Don't forget that it's only cost £200! The build in DAC is good enough to rival the like of Cambridge Audio 640c. Very complicated but when get it right it's simply superb. (for the budget end)