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admin's picture
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BK XXLS400 or Monolith? Please help me decide

I'm moving into a bigger house and want to buy a better sub for the movies. I haven't measured the room yet, I'm waiting for the keys. I've seen the living room, it's medium sized for a 3-bed house.

The sub needs to be a downwards firing and up to £500.

I have a dilemma XXLS400 or Monolith?

Could you please see the below and help me decide?

My set up:
Amplifier: Yamaha DSP-AX763
Front: Wharfedale Diamond 9.1
Rear: Wharfedale Diamond 9.0
Centre: to follow
Current sub: REL Q200E

Pro's I found so far fo each:

- Deeper bass! I don't mind if it's a little bit slow and not good with music
- I mainly watch TV & films

XXLS 400:
- Better & more punchy higher bass (based on forum opinions). It could integrate better with my front speakers. I'm going to set crossover on 80 Hz
- Higher chance I won't need AntiMode (no bass reflex, easier to position)
- Smaller & easier to position correctly. Monolith migh need to stay in the corner
- Less risk of a complaint from neighbour (semi-detached house)

I could accept the bad sides of Monolith for the sofa shaking movie effects. The question is - Is it a bad idea in my case?

Thanks for advice!

bigboss's picture
Last seen: 9 hours 42 min ago
Joined: 25/03/2009 - 21:40
Posts: 18469
RE: BK XXLS400 or Monolith? Please help me decide

Beginner wrote:

I could accept the bad sides of Monolith for the sofa shaking movie effects.


CnoEvil's picture
Last seen: 7 hours 57 min ago
Joined: 21/08/2009 - 18:01
Posts: 17298
RE: BK XXLS400 or Monolith? Please help me decide

It may come down to the size of the room, both for the amount of bass generated and whether the sub will comfortably fit.

Secondly, it could depend if you will be using it to listen to music (now or in the future).

For me, the decision would be easy as I prefer the control of a sealed sub, and I like the Sub to be subtly integrated, without drawing attention to itself, until needed.

It's very personal though and there isn't a right answer, only your preferential one.

"We should no more let numbers define audio quality than we should let chemical analysis be the arbiter of fine wines."  Nelson Pass

fr0g's picture
Last seen: 1 year 2 months ago
Joined: 07/01/2008 - 18:38
Posts: 3440
RE: BK XXLS400 or Monolith? Please help me decide

If you give BK a call or use the form on the website and let them know your situation and preference, they will suggest the right one.


I ended up the the 400.

Pittodriered's picture
Last seen: 6 months 2 weeks ago
Joined: 20/09/2009 - 11:53
Posts: 69
RE: BK XXLS400 or Monolith? Please help me decide

I've just upgraded to a XXLS400 from a monitor audio R370HD and it's far superior. Bass is definitely tighter and no problems integrating with my speakers. Be warned though even after I had measured to make sure it would fit its still larger than I thought, but not too big and the other half says it looks ok. I also bought an Antimode but haven't had a chance to hook it up as I've injured my right knee (detached knee cap and torn lateral ligament), hopefully I'll get it set up this week.

ellisdj's picture
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Joined: 11/12/2008 - 17:55
Posts: 5357
RE: BK XXLS400 or Monolith? Please help me decide

Hello Mate


you need to consider room placement and the effect of your room on both subs

with a sealed box sub its relatively easy - put it in a corner and you are half way there - put in the right corner and you will get decent bass - however even the 400 will peak hard in the low frequencies causing boom so you will still need an antimode.  Room modes with bass are inevitable.

Once you buy an antimode you will realise it has been the best £200 you will have spent on your whole system - thats a promise- budget one in you will not regret it


The monolith on the other hand is a beast of a sub - its performance is staggeing in free air but put it in a room and the boundary effect will throw that all off - so you will need to work hard to get it placed correctly and definately need a antimode.  The antomode does not work miracles, all it does is reduces peaks in your bass performance to a certain degree, that also raises other dips you may have - however if your peaks are huge then it can only do so much.


The 400 will be easier to get to sound great and its a great sub for films and movies  - I have one, however if you can get the mono setup well it will take the sub performance to the next level for films, but if you cant its likely to be a boom fest.

If you know how to use Room Equalisation Wizard well then you have a good chance with the mono - if you dont learn and stick with the 400 - you will likely get better results

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Anonymous's picture
RE: BK XXLS400 or Monolith? Please help me decide

XXLS400 would be a reasonable choice. The fact is I have limited space for the sub and no experience with set up. However, Monolith is so tempting!


First I'll get the house furnished and I'll see if I have space for Monolith. Then I'll think about it again.


Thanks guys!

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