Dynaudio BM15a

[Oliver Sheen]

I have Dynaudio BM15a's and have been tempted by these £500 speaker stands from http://www.aaa-design.com/black_box/index.htm
They certainly look great but would you still reccomend soffit mounting over these. Are there any plans around for constructing soffit mounting?

Cheers

Oliver

[barefoot]

Oliver,

£500 for speaker stands!:shock: In my opinion expensive speaker stands are a waste (along with expensive speaker wire). You'd be much better off using that money to upgrade your speakers and/or your room.

Soffit mounting actually does make a difference, but the BM15a's don't appear to incorporate a -6dB low shelf filter which I explained in this thread http://johnlsayers.com/phpBB2/viewtopic.php?t=100. The LF Trim might work, but I fear you might wind up with a response bump in the 200Hz region.

Thomas

[Oliver Sheen]

Do I really want to start incorporating filters into my monitoring system?

Well, the filters are there already. You can't get away from them. I guess the best you can do is try to minimize their use.

Placing the monitors away from the wall as you suggested is probably the best solution in your case. That's really how the speakers were designed. Like I said, however, nearfields do have a mismatch in total power output between the high and low frequencies in order to flatten out the anechoic response. So the spectral balance of the sound coming directly from the speakers to your ears prior to any reflections is correct, but the reverberant field is bass heavy (or treble light depending on how you look at it). This being the case, you want your room to compensate for the mismatch. The room should have fairly good absorption below about 300Hz while being relatively reflective but diffuse above that frequency.

As far as using and external power switch, it's been my experience that most devices other than computers don't mind being turned on that way. In most audio appliances the power switch works directly on the main power input anyway. But power switches always produce a spike due to the slight arc that occurs when the contacts approach one another. The monitors will most likely have an internal device to shunt this spike, but it's probably better to be safe than sorry. Who knows what might happen over repeated use? If you want to do it this way, I would suggest using the switch on a high quality filtered power strip. Or, if you want to use a light switch, you can buy a couple very inexpensive items from your local electronic supply store to suppress the spike. You need a Metal Oxide Varesistor (MOV) and a 0.01uf/600V capacitor. You wire them into the light switch like this:

Code: Select all

   hot----+----+--o/ o--+----o
          |    |        |
        [MOV]  +---||---+
          |    0.01uf/600V
          |
common----+------------------o  

Thomas

[Oliver Sheen]

Thomas,
IS there a problem in powering my BM15a's on and off from the wall socket? IF the monitors are enclosed I wouldn't be able to get around the back to switch'em on.

Cheers

Oliver

[barefoot]

Err..uuum????

Oliver,

In trying to quote you, I somehow I managed to delete your post and replace it with mine. Sorry about that. Mabye I need to figure out these moderator privileges a little better.

But then I see now that I wasn't even logged in????

Anyhow, you can see my answers above.

Thomas

[Oliver Sheen]

Thanks for that Thomas. I've decide not to flush mount after all. Who am I kidding - the're only BM15a's when alls said and done.

I know these monitors stands sound expensive at £500 but have you seen them. Take a look here and you can see where the moneys is going. Anyway if you had a friend who was a spot welder (or a spot welder who was a friend, it doesn't matter which) I reckon you could knock them out for around £100. Which is more like it.

Take a look at them here:
http://www.aaa-design.com/black_box/index.htm


Cheers

[Oliver Sheen]

why didn't aaa's website come up as a live link, anyone?

[John Sayers]

Not sure Oliver - I don't add the url tags and it picks it up antomatically which is the easiest way to go.

cheers
john

[Oliver Sheen]

Thomas, doesn't the rocking motion that is inherent in most speaker stands over a metre in height blurr the sound and stereo imaging?

What speaker stands do you recommend to compensate for this? I guess you could screw common or garden stands to the floor but this can wreck your floor and it makes postiioning them a difficult job.

The ones I'm having made have a large Y-shaped footprint to illiminate any forward and backward rocking. I guess this is a bit experimental but there not much more in cost than other stands (at £120), they have a vatiable height so they must be at least as good as other stands on the market (right?) What are your thoughts?

Cheers

Oliver

[barefoot]

Oliver,

It's difficult to imagine that a stand could so directly effect imaging. Assuming you had feather weight monitors placed on rickety lamp tables purchased from the bargain basement warehouse it's conceivable that, apart from vibrations and panel resonances, the actual rocking motion could create some Doppler type modulation distortion. Even in this extreme example, however, that particular distortion modality would likely be very minor. And any magazine-writer/golden-ear/speaker-stand-salesman type who would specifically identify such distortion as "image blurring" is definitely reaching for straws with their painfully limited understanding of physics.

Stacked milk crates stolen from your local grocer, or lead filled, carbon fiber composite, quadruple reinforced, kiloton lifting, bank account busting behemoths.... it's all the same to me.

When you have a set of monitors who's distortion levels never rise above 1% over their entire frequency and power range and which are placed in a pristine acoustic environment, then it might be time to worry about how the stand motion is affecting the sound quality.... or not.

Thomas