Chorus II Passive Radiator

[paully]

I was reading where one poster felt that the Chorus II had to be in a

corner to really shine. That isn't going to happen, would get

some corner horns if I had a corner to use. I would be placing

the Chorus II's right in front of a doorway to another room so they

really won't have much in the way of "wall" behind them at all.

Do you think that this would be a problem? It doesn't strike me

for a passive radiator that it would.

[SilverSport]

not a problem per se but your passive would like a wall to extend its bass...I would think (...and this is where I usually get into trouble) that at worst, you would lose some bass response...now if you closed that door...I don't believe you need a corner either...I have Quartets with the rear passive and have mine about a foot and a half to two feet from a back wall and about the same from one side wall...the other is by a closet door.

Enjoy.

Bill

[paully]

If I lose a little bass, I lose a little bass. If that is the

worst of it, no problem. The Chorus seem to be about the top of

the line as far as what will fit in my room. La Scalas are iffy,

so I like to hear tht they will work.

[mark1101]

Paul,

Just my 2 cents. If you have nothing behind a speaker with a passive radiator, I think that would be far less than optimal. Not just a little less than optimal. The speaker performance depends on that radiator working properly.

Personally, I think you should look at some other model. I think the Chorus would great if Heresy is the next best fit...but if you can't use them properly you might be disappointed.

On the other hand you might free up a room or rearrange one to make things work later...or move some day and have different room opportunities. We moved a few times and shook up the stereo system for sure.

I just would not expect to hear magic if you buy something like that and try and use it as you describe.

[DrWho]

For what it's worth...

A passive radiator is operationally no different than a port. I don't

think people generally argue that a rear ported speaker needs a

corner...

The passive radiator in the Chorus II is tuned to around 40Hz, which

corresponds to a 28 foot wavelength. The polar response of a 15"

diameter membrane with a 336 inch wave is going to be nearly

omnidirectional. In other words, the sound coming from the passive will

go in every direction - including the direction towards the listening

position. The only loss in output as compared to a front-firing passive

will be mostly attributed to the ~24 inch pathlength difference (for

the sound to wrap around the cabinet).

However, there are certainly gains in bass when the speaker is placed

in a corner. I'm pretty sure the Chorus II was voiced to be in a

corner, but the presence of the corner is not fundamantal to the

operation of the passive radiator. So though the individual speaker

will operate properly in a non-corner environment, I would be more

worried about the lack of stereo symmetry if only one of the mains is

lacking a corner.

In other words, there is nothing inherant to the Chorus II that makes

it behave any differently than any other speaker as it pertains to

speaker placement.

[paully]

Well, that isn't what I wanted to hear...

I don't know if I understand. The Heresy's bass response rolls
off pretty high I think. Does the loss of the bass from the
passive radiator cause other aspects of the sound to be degraded or are
you really just missing some bass? I suppose a Heresy, or if I
can swing it, a pair of La Scalas might be a better idea.

[DrWho]

Maybe this analogy will help....

Take a speaker and put it in the middle of the sky (so no boundaries

anywhere near it) and put enough power into the speaker so that it

measures 100dB at one meter. Now take that same speaker and bring it

down into the middle of a field. If you can visualize a sphere

surrounding the speaker while it was in the sky, then by bringing it

down to the ground you can see that it looks like cutting that sphere

in half. The space now seperated by the ground reflects the sound up

such that the speaker radiates into half as much space. This is

referred to as "half space" and results in twice the output, or +3dB.

So for the same power going into the speaker, it will now measure 103dB

at one meter.

Now take the speaker in the field and then drop the Great Wall of China

behind it. This cuts that space in half and we're now looking at a 1/4

space situation. Or going back to the sphere, you're left with 1/4 of

the sphere that has sound being radiated into it. This gives you an

additional +3dB, yielding a total of +6dB. The speaker will now measure

106dB at one meter.

You can cut that 1/4 space in half again by adding another wall

perpendicular to the wall of china, effectively cutting the 1/4 space

in half - yielding an 1/8 space scenario. You now have +9dB relative to

full space and will measure 109dB at one meter with the same power

going into the speaker.

Just keep in mind that the reason for the additional gain is because

the boundaries are reflecting the sound (just like putting mirrors

around a flashlight). So if our speaker isn't radiating in every

direction (as depicted by the sphere), then the boundaries aren't going

to contribute to the sound. This is why the tweeters and squawkers will

measure 100dB in a corner and in free space. In the real world, our

boundaries also aren't perfect at reflecting the sound (some of it goes

through the walls), so 1/8th space is going to be closer to +6dB than

+9dB. (~2dB instead of 3dB for every halving of the space). So taking

into account that the directivity of the speaker isn't omnidirectional

until you get down to around 200Hz, and the nonperfect reflections, you

can expect about 2dB less output from 200Hz and below by having the

speaker near a door opening.

I probably made this sound way more complicated than it needs to be, so

I should probably go hunt down some pics if you're still confused. The

reason I bring this up is to note that the extra output from being near

boundaries is the result of reflections. And just like a mirror

reflecting a beam of light from a flashlight doesn't affect the light

coming from the lightbulb, the walls aren't going to change the manner

in which the drivers create sound. It just affects what ends up at the

listening position. In other words, your other frequencies aren't going

to be behaving any differently.

Anyways, a heresy and a lascala are both going to be affected by the

same phenomenon. In fact, every speaker is going to have the same 2dB

less output below 200Hz as compared to the other side. This is why I

was saying that it is not something inherant to the Chorus II and thus

should not be viewed as a problem related in any way to the passive

radiator.

For what it's worth, I've heard just about every vintage Heresy and

Lascala and there is no way I would trade my Chorus II's for either of

them. 2 years ago I was in an apartment without corners for both

speakers and didn't have any problems.