KCW wrote:
However, what would be the minimum room size you would recommend to adequately accommodate the BL5s? I live in a Victorian house and I have a dedicated room for listening and cinema viewing. The room size is 4m wide by 5.5m long and 3m high ceiling.
I house my BL5s approx 0.5 m from the wall - equal distance from the back and side wall and symmetrical in-line. My BL5s each sits on top of a piece of solid granite base, which is about 340mm square (the same size as the diameter of the BL5 base) and 30mm thick. I had them specially cut by my local marble merchant and I found this arrangement improves the bass quality tremendously - more focussed bass by reducing the induced bass boom since the listening room is of solid floor construction as with all Victorian houses.
My comments about Small vs Sufficient room volume for these speakers are relative to an untreated room, where they're just plopped into place, usually because that's where it's handy to have them.
Once you begin paying attention to the principles of speaker placement, listening position, reinforcing the speaker base as you have done - thinking of where items of furniture can act as bass traps, or where a carpet can kill any secondary+ reflections, etc -- then you have begun doing things that will help the room play along better. Many of these things will help overcome the problems caused by the room being too small - and then it's a calculation between what it costs to fix a small room (in money and aesthetics), compared to moving the setup to a larger room.
The challenge is what to do about the energy BL5s generate when used at a realistic volume, whether you're listening to a solo guitar player or a symphony orchestra - and the paradox is that with an untreated and small room, where the placement is random, you may risk that the room is cancelling out the potential realism, because interference is created by the shortcomings of the room. (Standing waves, room modes, flutter echo.) Whether the room is small or large, china vibrating on a glass shelf will cause interference of its own, at certain volumes.
Here's an illustration by Ethan Winer, showing why large rooms have advantages:
It's impossibly (or insanely) expensive to counter all the unwanted effects of having speakers in a walled-in space, but the larger room provides greater volume for the sound energy to dissipate in, without creating energy "heaps". At the bottom, you see the frequency response of the smaller room going up and down in power (dB), with clearly marked highs and lows along the frequency spectrum. What's happening is that sound-waves are interacting, sometimes adding up, sometimes subtracting, creating a very uneven response where you'd want it as flat as possible.
The larger room above has similar additions and subtractions, but there are a lot more of them, the difference between high and low is smaller, and the overall effect is of a much more even response. You don't notice the highs and lows so much. So - even with room calibration in the BL5s, you could still have them in a room where the bass will be working against itself, because of the size of the room - and particularly noticeable at higher volumes, because that's when a lot of excess energy starts trying to find ways to go.
One nice thing about older houses, is that there's a lot of wood in the walls and floors, and that this can help absorb a lot of the excess energy - on the other hand, as we've seen in other threads, sometimes such rooms are so soft that they breathe with the bass pulses, taking the edge off the bass - so it's all a balancing act.
Your room is not too small. Ethan Winer (see below) would actually have wanted it to be a little shorter, to achieve an ideal room proportion of 1:1.28:1.54 - where the ceiling height is the base figure. Following those proportions, you can see that your width is quite good, and that the length is an issue.
Ideal room sizes/proportions describe a space where many of the negative byproducts of sound waves reflecting off the walls are avoided because the surfaces interact properly. Paying attention to speaker placement, where you listen, and possibly the use of bass traps, can create a very good listening space in your room.
And then, as I write below, it's also important to consider that the BL5s are a special creature - using side reflections, so you want to accommodate for those.
Ethan Winer knows a lot more about this than I do, and if you have the time one evening, reading through this will probably result in better listening: link
And Cardas has another, just as thorough discussion: (Note that at the bottom of each page, you can click through to the next.)
It's important to recognize that people discussing acoustics don't always agree - so don't get confused if Cardas, Winer and others don't see eye-to-eye. For instance, some of the recommendations they'll come with don't apply to the BL5s, because these are actually using side reflections to enhance the sound, where many audiophiles consider any reflection a potential source of problems.
The entire idea behind acoustic lenses is to add dimension to the sound created through them with side reflections. At any rate, the reflections that most often cause problems result from the bass - and even there, the BL5s have their own remedy: the room calibration.
So don't think you're in trouble because you have BL5s, compared to ordinary speaker designs, you're already way ahead. But you want to make certain that they're allowed to shine. Working with the room can give tremendous benefits - just thinking about what the furniture adds or subtracts will be an ear opener! (When I took all the furniture out of my listening room, it became too
responsive - with too much room tone (echo). Just bringing in the couch
helped dampen the room considerably towards the ideal.)
