I've done a lot of reading on the Beoworld Forums about this subject, but I can't seem to find a definitive answer.

Since the Beolab 5 converts an audio signal to digital to do processing on it before playback, it seems that digital -> BL5 is the best approach. However, I have a very nice Benchmark HDR DAC I'd like to utilize in the middle (listen to the same music via headphones), and I'm wondering if I'll really lose any fidelity sending analog to the BL5s? I imagine the DAC in the BL5 is quite high quality, but I'm concerned about digital -> analog -> digital -> analog playback.

Obviously I could (and may) do a bunch of testing on my own, but I'm hopeful that someone may have already been in this situation and knows whether it's something I should worry about.

nmook:

I've done a lot of reading on the Beoworld Forums about this subject, but I can't seem to find a definitive answer.

Since the Beolab 5 converts an audio signal to digital to do processing on it before playback, it seems that digital -> BL5 is the best approach. However, I have a very nice Benchmark HDR DAC I'd like to utilize in the middle (listen to the same music via headphones), and I'm wondering if I'll really lose any fidelity sending analog to the BL5s? I imagine the DAC in the BL5 is quite high quality, but I'm concerned about digital -> analog -> digital -> analog playback.

Obviously I could (and may) do a bunch of testing on my own, but I'm hopeful that someone may have already been in this situation and knows whether it's something I should worry about.

When I first took delivery of my Beolab 5s, I ran them in analog mode for about 6 months, driven by a good analog professional monitor controller that was being fed by analog outputs of a respectable digital mixing console.  I then replaced that monitor controller with a digital one, so that my signal flow became entirely in the digital realm from the input converters all the way to the loudspeakers.  I tend to be conservative about the audibility of differences like this, but I was pleased to find that I heard a difference (small, but convincing to me).  I'm not sure I could reliably pull it out in a blind trial all the time, but I find I really prefer the all-digital flow, especially when I'm running at a high sample rate (96 kHz.).  

So, I suggest that the digital input is worth using if you can.  The difference is small, certainly.  I think it's there.  

I hope this helps.  

Best regards,

Hi Dave - a question about the auto-calibration of the BL5 (just out of personal interest).

I understand that the bass compensation is calculated from a measurement of the reverb time of the room, so that the amount of bass generated is modified to prevent an overly "boomy" response, is this correct? If so, does it or even can it eliminate positioning issues such as standing waves or do you still need to experiment with speaker positioning/seating position etc. to avoid the worst effects of interference and get the best results.

My thinking is that maybe folk are expecting too much of the calibration facility, and that even with this feature normal bass positioning precautions have to be applied.

Dave Moulton:

When I first took delivery of my Beolab 5s, I ran them in analog mode for about 6 months, driven by a good analog professional monitor controller that was being fed by analog outputs of a respectable digital mixing console.  I then replaced that monitor controller with a digital one, so that my signal flow became entirely in the digital realm from the input converters all the way to the loudspeakers.  I tend to be conservative about the audibility of differences like this, but I was pleased to find that I heard a difference (small, but convincing to me).  I'm not sure I could reliably pull it out in a blind trial all the time, but I find I really prefer the all-digital flow, especially when I'm running at a high sample rate (96 kHz.).  

So, I suggest that the digital input is worth using if you can.  The difference is small, certainly.  I think it's there.  

Thanks, Dave. That's exactly what I wanted to know and your experience is very helpful. Now the only thing to consider is when I'm listening to non-perfect sources such as iTunes whether the same holds true.

Over-emphasized frequencies can be moderately compensated for with room-equalization/calibration.

A frequency "suck-out", however, can not.

Barry

Puncher:

Hi Dave - a question about the auto-calibration of the BL5 (just out of personal interest).

I understand that the bass compensation is calculated from a measurement of the reverb time of the room, so that the amount of bass generated is modified to prevent an overly "boomy" response, is this correct? If so, does it or even can it eliminate positioning issues such as standing waves or do you still need to experiment with speaker positioning/seating position etc. to avoid the worst effects of interference and get the best results.

My thinking is that maybe folk are expecting too much of the calibration facility, and that even with this feature normal bass positioning precautions have to be applied.

This is a good question, and the answer can be a little hard to get your head around.  

In this particular case (different from all other room calibration systems I know), the BL5, using the integral microphone, detects what Jan Abildgaard Pedersen calls "Room Radiation Resistance."  This is not reverberance as such, but the sum of all energies at each frequency reflected back to the particular speaker position.  This, in turn, is essentially the same as "power response" (which can be thought of as "the average of all frequncy responses at all positions in the room").  

The microprocessor in the speaker calculates an inverse curve to the power response for that speaker position, essentially flattening the "average frequency reponse" throughout the room from about 10 Hz. to 300 Hz.  

Are you with me so far?  

What this means is the the average response is flat, but at any given position in the room it may not be flat, although it is usually fairly close.  So, ABC is a generalized average correction for low frequencies throughout the room.  It does not correct for a specific listening position.  Further, it does not and cannot correct for the problems presented by standing waves in a room.  Those waves are specific to the room dimensions and cause there to be changes in level at the standing wave frequency as a function of the listening position in the room.  Hard to think about!  

Interestingly, traditional room correction systems place a microphone at the listening position, calculate the frequency response at the position (after "windowing out" the room reflections, sort of), and yielding an optimized response for that position.  Sounds good, in theory.  Unfortunately, it often makes the speaker sound quite bad at other positions in the room, some of them quite close to that optimized listening position.  

The upside is that such a system can be used for full bandwidth, and if you want ONLY that listening position, it can be fine.  The downside is that the calibration is not simple and requires the services of an expert.  In addition, the calibration needs to be redone every time the room changes (furniture, occupants, doors, windows, etc.).  A pain.  

ABC is an elgant low-frequncy solution that is automated.  It's now been 7 years, and I continue to be impressed by how effective and practical it is. 

With all that said, you may wish to experiment with seating position and speaker position, especially to deal with standing waves.  Check out an article about control rooms in home studios I wrote a couple of years ago: 

http://www.moultonlabs.com/more/making_your_home_control_room_the_best/

I hope this helps.  

Best regards, 

Dave Moulton:

Puncher:

Hi Dave - a question about the auto-calibration of the BL5 (just out of personal interest).

I understand that the bass compensation is calculated from a measurement of the reverb time of the room, so that the amount of bass generated is modified to prevent an overly "boomy" response, is this correct? If so, does it or even can it eliminate positioning issues such as standing waves or do you still need to experiment with speaker positioning/seating position etc. to avoid the worst effects of interference and get the best results.

My thinking is that maybe folk are expecting too much of the calibration facility, and that even with this feature normal bass positioning precautions have to be applied.

This is a good question, and the answer can be a little hard to get your head around.  

In this particular case (different from all other room calibration systems I know), the BL5, using the integral microphone, detects what Jan Abildgaard Pedersen calls "Room Radiation Resistance."  This is not reverberance as such, but the sum of all energies at each frequency reflected back to the particular speaker position.  This, in turn, is essentially the same as "power response" (which can be thought of as "the average of all frequncy responses at all positions in the room").  

The microprocessor in the speaker calculates an inverse curve to the power response for that speaker position, essentially flattening the "average frequency reponse" throughout the room from about 10 Hz. to 300 Hz.  

Are you with me so far?  

What this means is the the average response is flat, but at any given position in the room it may not be flat, although it is usually fairly close.  So, ABC is a generalized average correction for low frequencies throughout the room.  It does not correct for a specific listening position.  Further, it does not and cannot correct for the problems presented by standing waves in a room.  Those waves are specific to the room dimensions and cause there to be changes in level at the standing wave frequency as a function of the listening position in the room.  Hard to think about!  

Interestingly, traditional room correction systems place a microphone at the listening position, calculate the frequency response at the position (after "windowing out" the room reflections, sort of), and yielding an optimized response for that position.  Sounds good, in theory.  Unfortunately, it often makes the speaker sound quite bad at other positions in the room, some of them quite close to that optimized listening position.  

The upside is that such a system can be used for full bandwidth, and if you want ONLY that listening position, it can be fine.  The downside is that the calibration is not simple and requires the services of an expert.  In addition, the calibration needs to be redone every time the room changes (furniture, occupants, doors, windows, etc.).  A pain.  

ABC is an elgant low-frequncy solution that is automated.  It's now been 7 years, and I continue to be impressed by how effective and practical it is. 

With all that said, you may wish to experiment with seating position and speaker position, especially to deal with standing waves.  Check out an article about control rooms in home studios I wrote a couple of years ago: 

http://www.moultonlabs.com/more/making_your_home_control_room_the_best/

I hope this helps.  

Best regards, 

 

 

Thanks for that - am I right in therefore paraphrasing, as I said before (albeit in much less detail) that the ABC will not/cannot correct for standing waves in a particular room and so, even though you have ABC with your BL5's, you should still experiment with speaker/seating position with your BL5's.

After all, if you spend that much you should ensure you're getting the best from your investment, especially if it just means shifting your speakers or your seat a foot or two!!

As Dave wrote:

With all that said, you may wish to experiment with seating position and speaker position, especially to deal with standing waves.  Check out an article about control rooms in home studios I wrote a couple of years ago: 

http://www.moultonlabs.com/more/making_your_home_control_room_the_best/

After all, if you spend that much you should ensure you're getting the best from your investment, especially if it just means shifting your speakers or your seat a foot or two!!

I have spent a considerable amount of time working to get the best placement of BL5s, according to established principles of speaker placement. As an owner of BL5s, I believe I can permit myself a bit of criticism of B&O when it comes to how these speakers were sold to the market. Maybe they were afraid of getting too audioholic, but they did the innovation the BL5s represent a great disservice with the "Place them wherever you want" nonsense. They turned a potential Stradivarius into any old violin.

In my opinion, and Dave can correct me if I'm wrong, setting up BL5s properly requires consideration of at least the following:

1. Room geometry - with the ideal setup being symmetrical to walls and listening position.
2. Room properties - is the room lively or overly dampened. Do you need to do something to the acoustics, independently of what the BL5s do to the bass?
3. Space - will the speakers have to be right up against a wall(s), or can they be moved into the room, away from walls?
4. Side wall symmetry - will both speakers be the same distance from their respective side wall, in a symmetrical setup, ensuring that the ALT is as effective as it can be (side reflections are essential to getting these speakers to speak.)
5. Is your head right up against a back wall, or is there enough room behind the listening position for you not to be getting bounce-back mixed in with the direct sound from the speakers?

Point 1 needs to take standing waves into account, and you will find that repositioning the speakers even a little, can have considerable impact on how you experience the sound they produce.

BL5s, for the reasons Dave explains above, are so good in both the manner they have been optimally shaped and functionally engineered, that they will produce better sound than you're likely to have heard even when you don't bother with the above. But just as with most things in life, a bit of fine tuning can produce spectacular results.

I really wonder why B&O went for the convenience aspect with these speakers. It's as if Audi built the R8, and then marketed its parking ability. Back in 2003, B&O could have owned public perception when it came to many of the principles underlying BL5 technology and performance. Seven years later, a number of HiFi-manufacturers are catching up, and realizing that what BL5s can do is something most speakers should try to do.

soundproof:

In my opinion, and Dave can correct me if I'm wrong, setting up BL5s properly requires consideration of at least the following:

1. Room geometry - with the ideal setup being symmetrical to walls and listening position.
2. Room properties - is the room lively or overly dampened. Do you need to do something to the acoustics, independently of what the BL5s do to the bass?
3. Space - will the speakers have to be right up against a wall(s), or can they be moved into the room, away from walls?
4. Side wall symmetry - will both speakers be the same distance from their respective side wall, in a symmetrical setup, ensuring that the ALT is as effective as it can be (side reflections are essential to getting these speakers to speak.)
5. Is your head right up against a back wall, or is there enough room behind the listening position for you not to be getting bounce-back mixed in with the direct sound from the speakers?

Soundproof really got down to it here – I think it's an excellent and thoughtful post.  

Regarding item 1: Lateral symmetry and a common median plan are the most important, here.  A ceiling height of at least 2.5 m is important, too.  

Regarding item 2: Very important.  As Soundproof suggests, the character of the room has a profound effect on the performance of the loudspeaker. I've come up with a room topology called a "Moulton Room" which (a) works quite well and (b) doesn't cost very much.  With BeoLab 5s, it gets even simper and cheaper.  Key ingredients (along with symmetry) are a very absorptive front wall and a mildly absoptive floor (a thick carpet) and front half of ceiling (usually foam or soft fibreglass panels).  Hard sidewalls.  

Regarding item 3: The BoLab 5 was designed so that it COULD go close to the wall behind it without severe problems.  However, getting it 1-2 m out from the wall behind it and 1 m from the side wall really helps with depth and phantom images.  

Regarding item 4: See items 1 and 2.  

Regarding item 5: a very good, sometimes overlooked point.  All standing waves have nodes (build up of sound pressure) at the walls, so there will be extreme bass at those frequencies perceived close to the boundaries.  It's good to be at least .7 m from the rear wall – 2 m is better.  

A note about marketing: advertisements always make (and are expected to make) the best case for a product.  As a result, claims are often idealized and a little removed from science (where we are always expected to make our worst case).  Given the sales success of the BeoLab 5 (which, in sales volume, has simply blown away ALL of the other high-end speakers – those costing more than $3,000 apiece), I suspect B&O has actually done an excellent job of marketing and advertising, as well as understanding their customers' needs and desires.  

As Soundproof so correctly points out, you can make BeoLab 5s sound soooo much better by some attention to their placement and room acoustics that, to me, it is almost criminal not to.  

Best regards,