Active Speakers

[Thropplenoggin]

Quad have just announced the release of the 9AS active loudspeakers with built-in DAC.

http://www.gramophone.co.uk/classical-music-news/quad-launches-new-active-loudspeakers-for-the-desktop-and-beyond

http://www.whathifi.com/news/quad-gets-active-with-compact-9as-speakers-with-built-in-dac

More specs here: http://www.quad-hifi.co.uk/Product.aspx?lang=En&Tab=53

It seems to provide a cheap(ish) way to get more out of downloads and streaming without the need to shell out on a separate DAC and amp. Not exactly easy o'the eye, though.

[jayne lee wilson]

AS with the AVI adm range, a great solution for some people in a world with too much choice, but if you want the best possible sound this can't be the way. The signals running between and within DACs and amplifiers are tiny & very delicate, and the vibrating cabinet of a loudspeaker is not the best place for them, they'll be vulnerable to all kinds of electro-acoustic interference. I'm sure the designers will do all they can to deal with that, but a music-loving hifi purist will want as much as possible in mains-isolated separate boxes, with protection from vibration and preferably well away from speakers.

But the main thing with system-building is to ask yourself what YOU want out of listening - where, how, what do you listen to, are downloads/discs important, size of the room etc... the biggest problem is a bewilderment of choices! Active speakers with DACs do simplify all that, but what if you feel differently later on? It's much harder to change, or add, anything.

Earlier this year I was a goner for 24-bit downloads, I was planning major changes to bring them in en large. But the purchase of a 2ndhand DAC (T&A DAC8 replacing Cambridge DACMAGIC) made CDs sound so good I lost interest in the files... so now I have the more traditional problem back again - the invasion of coffee tables by new CDs.
(Having fondly imagined the CDs already here would keep me occupied... )

Behaviour is very telling - the more you listen and buy (enthusiasm aflame), the more you know you're going in the right direction with the system. A point about choices: the impression left in your memory AFTER listening is often the truest one. You'll know if it's right or not, and you can't deceive yourself over that.

[richardfinegold]

AS with the AVI adm range, a great solution for some people in a world with too much choice, but if you want the best possible sound this can't be the way. The signals running between and within DACs and amplifiers are tiny & very delicate, and the vibrating cabinet of a loudspeaker is not the best place for them, they'll be vulnerable to all kinds of electro-acoustic interference. I'm sure the designers will do all they can to deal with that, but a music-loving hifi purist will want as much as possible in mains-isolated separate boxes, with protection from vibration and preferably well away from speakers.

But the main thing with system-building is to ask yourself what YOU want out of listening - where, how, what do you listen to, are downloads/discs important, size of the room etc... the biggest problem is a bewilderment of choices! Active speakers with DACs do simplify all that, but what if you feel differently later on? It's much harder to change, or add, anything.

Earlier this year I was a goner for 24-bit downloads, I was planning major changes to bring them in en large. But the purchase of a 2ndhand DAC (T&A DAC8 replacing Cambridge DACMAGIC) made CDs sound so good I lost interest in the files... so now I have the more traditional problem back again - the invasion of coffee tables by new CDs.
(Having fondly imagined the CDs already here would keep me occupied... )

Behaviour is very telling - the more you listen and buy (enthusiasm aflame), the more you know you're going in the right direction with the system. A point about choices: the impression left in your memory AFTER listening is often the truest one. You'll know if it's right or not, and you can't deceive yourself over that.

That is a great post, Jayne.
I have started a new position which involves a lot more time at a desk than I was formerly used to and I was considering a pair of active speakers for the desktop. I was going to use a usb-dac out of my computer (Audioquest Dragonfly). I was hoping that there would be a way to bypass the dac in the speakers.
I don't know if that is possible and will have to investigate further.

[johnb]

AS with the AVI adm range, a great solution for some people in a world with too much choice, but if you want the best possible sound this can't be the way. The signals running between and within DACs and amplifiers are tiny & very delicate, and the vibrating cabinet of a loudspeaker is not the best place for them, they'll be vulnerable to all kinds of electro-acoustic interference. I'm sure the designers will do all they can to deal with that, but a music-loving hifi purist will want as much as possible in mains-isolated separate boxes, with protection from vibration and preferably well away from speakers.

Well Meridian have centred their audio philosophy on active speakers and they seem to have a good reputation.

[Ferretfancy]

Well Meridian have centred their audio philosophy on active speakers and they seem to have a good reputation.

I have a Meridian 500 active speaker system and the results are excellent. The one snag is that, rather like Apple, the system is fully matched in a way that prevents much in the way of alteration or upgrades. The signal processor does a fine job, but does not have the facility to handle SACD surround, even though it is a 5 speaker set up, This is because Boothroyd Stuart do not believe in SACD. If I bought an SACD player I could use it, but not in surround sound mode.

There are a number of options for retrieving surround information from 2 channel material using a digital version of the ambisonic decoder, and this is very convincing, but it is not discrete in the manner of SACD. This doesn't bother me much in practice, and watching films, usually on DTS nowadays, the results are spectacular indeed ( I worry about the neighbours though ! )

[jayne lee wilson]

Yes - I've great respect for Bob Stuart and Meridian, they've been making great CD players and amps for decades, they understand digital and absolutely know what they're about, and they don't insult your intelligence with "ours is the one true way" proselytising. But like everyone else they have to sell to the market. So they are currently minimising disc replay and more complex systems with separate amps and sources.... Their active designs are probably better than most for build, technology and sound, but this needn't mean better than separates...

Whatever you input to a system, it's still a musical waveform that meets your ears. That's what you have to live with.

[Dave2002]

Earlier this year I was a goner for 24-bit downloads, I was planning major changes to bring them in en large. But the purchase of a 2ndhand DAC (T&A DAC8 replacing Cambridge DACMAGIC) made CDs sound so good I lost interest in the files... so now I have the more traditional problem back again - the invasion of coffee tables by new CDs.
(Having fondly imagined the CDs already here would keep me occupied... )
.

There's a discussion around the T&A DAC 8 here - http://www.hifiwigwam.com/showthread...9531-T-a-dac-8

At just under £2k it'd have to be pretty good - though the CEC unit mentioned in the thread costs more!
http://www.whathifi.com/review/dac-8 £1990

http://www.cec-international.com/PAGES/s11.html CEC DA 3N

Glad you're happy with your second hand purchase - and perhaps you paid rather less than the list price.

I wonder how the DACs above compare with these - http://schiit.com/products - which someone else recommended highly - and these are perhaps more affordable even with import costs.

[Phileas]

...a great solution for some people in a world with too much choice, but if you want the best possible sound this can't be the way. The signals running between and within DACs and amplifiers are tiny & very delicate, and the vibrating cabinet of a loudspeaker is not the best place for them, they'll be vulnerable to all kinds of electro-acoustic interference...

Can you quantify this interference Jayne, relative to other kinds of distortion in a typical audio replay chain?

[Beef Oven!]

The law of diminishing returns bites ferociously after £1,000, so active speakers are a Godsend.

[Gordon]

Active or multi-amp'd speakers have a lot going for them in design terms, the prime benefit is that they lose the high power crossover network and so allow a better match between amps and drive units. Most full size studio monitors these days are multi-amp'd. They solve other problems for users as well like a "one box" solution and avoid long speaker leads. That problem of course ends up as a potentially long lead for the signal cable from the source. For a certain sector of the market these devices are a good thing. Including a DAC these days makes sense.

Like all audio products these can be built to a budget and decent engineering will do the best possible within constraints.

Can you quantify this interference Jayne, relative to other kinds of distortion in a typical audio replay chain?

Quite so!! I thought the same when I first saw the post; I'm not sure what these "all kinds of electro-acoustic interference" are. The signal levels typical of the environment in which an active speaker exists will not be "tiny" they will be line level which is around half a volt. The main drive units will be powered with quite a few volts [15 volts for 30 watts in 8 ohms] and there will be some mains converters around spraying 50 Hz fields. That does not absolve the designer from taking care because a 24 bit DAC will have a very small quantum - see later below.

A moving coil cartidge will produce a few tens or hundreds of micro-volts - that is tiny - and a moving magnet perhaps a few tens or hundreds of milli-volts. Any DAC within the device will possibly be sourced by a USB link [an optical one would be better] from a computer say; USB 2 drive levels are 500 milli-volts balanced in a low impedance to avoid pick-up and permit long-ish cables, USB1 uses 3.5 volts, hardly tiny. That designer also needs to isolate the digital parts from the analogue, particularly the grounds, and one part of that is to use a decent DAC output level. No engineer would use voltage levels that are tiny if he/she can help it and in a speaker there is no need.

If the device also contained an ADC I'd be more concerned. A typical ADC chip will be driven by about 1 - 1.5 volts peak to peak, well clear of background clutter. However, in this case that engineer will recognise that a 24 bit PCM system will set the minimum quantum step size at 1/2^24 volts which is extremely tiny [a 16th of a microvolt, 60 nano-volts, which is less than basic thermal noise at room temperature in 600 ohms, 220 nano-volts] and we want each bit, including the LSBs, to carry meaningful audio, not rubbish, otherwise those LSBs are waste of time. As a matter of good design any external ground noise or extraneous interference will need to be catered for at that sort of level. Much more of a challenge; although the DAC suffers the same issue the problem is contained within the DAC unlike the case with the ADC.

It doesn't take many minutes with a pencil and a fag packet to see that assuring and maintaining 24 bits in an audio system is quite a challenge. So next time you think you hear the dfference between a 24 bit and a 16 download think about it!!

It is true that the usual speaker enclosure will be subject to vibration. So what mechanisms exist to cause harm in this case, other than the usual suspects of noise [unlikely in a speaker] and distortion [very likely in a speaker]? Any conductor that moves in a magnetic field will have a small voltage induced in it. There are wound components in a normal cross-over and any such component which is caused to vibrate in a magnetic field [eg stray leakage fields from the drive unit magnets or mains transformers] will have a voltage induced in it. Even if it vibrates in the earth's magnetic field it will do so. Those voltages will be very tiny compared to the signal voltages, nevertheless they exist. If you want a true dynamic range comparable to say 24 bit digital then these tiny signals may well fall into that range. An active speaker doesn't need to have wound components in the signal path [other than the voice coils] because the cross over is done at low signal level within the amp. Certain types of capacitor also exhibit this kind of mechanical/electrical behaviour. Ferrite used in coils is magneto-strictive and will vibrate acoustically in sympathy with the magnetic fields generated by the coil around it and so may add in a tiny way to the acoustic output of the speaker.

To avoid any such problem with coils of wire one must mount them in the magnetic fields so that the induced voltages are minimised. Cross-overs usually mount their several coils perpendicular to each other to avoid mutual inkage. IOW we should be aligning our speakers appropriately in relation to the earth's field; they might sound better pointing East than pointing North !!

What if the acoustic vibration also shakes the whole electronics board? What is the mechanism then? Difficult to see them other than the pure acoustic effect if the board isn't mechanically anchored well and that is like the box's own colouration.

Only the paranoid survive" Andy Grove, Intel

PS think of how vulnerable valves are to acoustic vibration [microphony] and stray fields!! What about the effect of high sound pressure levels at a microphone on its components. Capacitor mics have no moving parts but all the parts may be caused to vibrate. The Dynamic Range/Signal-to-Noise Ratio of any audio system is ultimately defined by the mics but often it is degraded by what follows.

[Stunsworth]

I have to admit I'd love to hear a pair of ATC active monitors. They seem to get universally positive reviews.

[clive heath]

One of the advantages of an active crossover is that there are designs such as the one I use from "Wireless World" where the two signals after the separation network are exactly in phase so that you can use 2 Khz as a crossover frequency. The woofer is not working at its usual upper octave, there are tweeters with resonance well below 1 Khz and the speaker centres are acoustically twice as close together. 4 Khz is usually the crossover frequency because with a passive crossover the phase differences are less audible at 4 Khz than at 2 Khz. Whether or not commercial active-crossover units take advantage of this I don't know.

[johnb]

As I have a Meridian G92 (tuner/CD/DVD/preamp) I would be very interested to hear a pair of the old Meridian DSP5000 24/96 speakers. (Each contain 2 DACs and 3 75 watt class A amps.) Many Meridian enthusiasts claim that they are an extremely good bargain at the SH prices they go for - even though that is usually around £1,500.

[jayne lee wilson]

Can you quantify this interference Jayne, relative to other kinds of distortion in a typical audio replay chain?

I think Gordon has answered with the sort of detailed expertise I can't begin to approach!

But... having heard the advantages of anti-vibrational supports (here, mainly "floating" platforms using opposed magnets) and using separate DACs and transports (though this doesn't always sound better), amps/preamps, it would be hard for me to feel happy with so much in one vibrating box, however controlled those resonances may be. But that's why I said the designers have to take care over it... ages ago I had a Musical Fidelity PreAmp placed on top of the power amps...when I finally arranged to place them on separate supports - the improvement made me laugh (and cry a bit for lost time...)...

But it will vary hugely from case to case, I'm sure.

Stunsworth - I lived with the ATC ASL 50s for about 3 weeks in 2005. They showed me more of what was going on in a given studio or concerthall, more of what made pianists or acoustics different from one another than anything I've ever heard - at least until the arrival of the T&A DAC8, which has similarly remarkable qualities. But I found them hard to live with as they needed a higher volume level to bring them to life in this room, than I was comfortable with - so, with the "forward" soundstaging, I found them fatiguing. But you never forget them, once heard. I think I've tried to recapture their qualities in a gentler setting ever since. If you can afford and live with an ATC Active, you've got it made!

D2K2 - That WhatHiFi review of the DAC8 is sketchy, but fairly accurate (surprisingly, from that source...) but they don't understand the filter choices - more than one of them is useful, especially the "short linear" (FIR2) option. John Bamford's HiFiNews review is much better.

[Gordon]

... ages ago I had a Musical Fidelity PreAmp placed on top of the power amps...when I finally arranged to place them on separate supports - the improvement made me laugh (and cry a bit for lost time...)...

That is the sort of experience that has old cynics like me wondering what is going on; HiFi manufacturers should be measuring a lot more of their product behaviour than they do, at least in public specs. Does anyone know of any reputable magazine/journalist who has investigated this sort of thing. I know Malcolm Hawkesford at Essex has done some evaluation like this but with inconclusive results.

With a turntable playing vinyl it is all too easy to see the multiplicity of ways in which mechanical linkages can feed back to the stylus tip, the whole system is alive with resonances. But it is hard to see a mechanism that would link mechanical vibration to the quality of sound with a couple of boxes of electronics with no moving parts. A pre-amp with a power amp beneath MAY just have stray mains fields from a powerful transformer affecting low level signals in the pre-amp together with inadequate screening, both electrostatic and magnetic, or even the large voltages driving an inefficient speaker system?? That should be measurable and may have been evaluated during design/development BUT that sort of thing is never part of a specification, perhaps it should be. Another non-mechanical cause could be poor earthing both via signal leads, which may not be sufficiently screened, and ultimately the mains earth. Power supply design and grounding is not a trivial part of Pre and Power Amp construction. One can imagine the boxes vibrating in sympathy with high sound levels in a listening room but I don't see how panel/structural resonances would convert into meaningful electrical disturbance.

I have a Cyrus system with each of CD player, Pre-amp and Power amp all using their own separate PSX PSUs. Their mains supply is all from one dedicated pair of double sockets in the downstairs ring main and I know that the impedance to the company earth pin at the meter is very, very small probably because it happens to be very short. In moving these boxes around - stacked, non-stacked etc - I can't say I can hear any difference in the sound quality. Removing the PSX PSUs one by one does alter the sound slightly but I would not say it is a big change and is confined to the power amp, the CD player shows no difference at all, to my ears at least. That is what I would expect because the power amp PSU has to work a bit harder than the mostly Class A in the CD and Pre-amp. A fingertip gently on the boxes whilst loud music is playing feels no sense of sympathetic vibrations anywhere and also using a saucer of water resting on them shows no surface ripples. Not necesarily scientific but a indicator nevertheless.