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Active Speakers Reference Thread

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29 minutes ago, bencat said:

To make a speaker active you need an adjustable Digital Crossover taking a digital signal from the source. This can then either be passed as a digital signal out to your DAC (Digital Analogue Convertor not Digital Active Crossover) of choice and then on through your system with 4 x mono amplifiers or 2 stereo amplifiers for a Two way speaker and additional amps as you increase the number of drivers .

There is though the complication that a DAC used as above needs to be a 4-channel DAC (or a pair of stereo DACs).

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1 hour ago, PuritéAudio said:

I believe there are advantages to be gained in active operation of a passive design but even more to be gained if the speaker is designed as active from the outset.

Grimm explain in their paper, chapter 2 ‘designing an active loudspeaker’ page 3.

http://www.grimmaudio.com/site/assets/files/1088/speakers.pdf

Keith

Hi,

I read some of the text. There are advantages of an active system when you select drivers - the higher frequency range drivers compared to the woofer can be less efficient. In the end, you always design the cabinet around the bass response required. That is, if the bass driver cannot produce low frequencies, using DSP to extend will probably cause the driver to exceed its linear excursion or even be damaged. So, you can obtain extended lower frequency response, but with limitations.

If you use a DSP approach, then you can optimise the response of the speaker, such as correcting the frequency response etc., but the cabinet remains the same. You have these advantages when you take a passive speaker and create an active system.

The document referred takes an existing passive design, and moves to an active design, it does not initiate the design from scratch, showing how an active design changes the cabinet, drivers used etc.

Taking a passive design, and moving to an active design is no more disadvantageous than initiating an active design from inception.

Regards,

Shadders.

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Super Wammer
5 hours ago, Tin said:

You may want to read this link about DSP.

You may refer to me as a 'Linnie' if you must, but you have, for analogue inputs, an ADC to convert analogue inputs to digital, before the DSP can digitally process them, and a DAC to transform the digital stream back to analogue.

DACs are very relevant in an active/passive discussion, even it not with your or mine current setups.

If you were planning to buy a very expensive dCS, Chord, or heaven forbid a Linn, streamer or DAC, and direct its output to a MiniDSP meatgrinder to create an active system, I have some very bad news for you.

You actually can get away with it if you want to use a MiniDSP for sub integration, as the long wavelenghts make processing easier and accuracy is less relevant, but for an active system it is far less desirable, and, if combined with a good DAC upstream, a total waste of money on the DACs behalf. 

But anyway, DSPs and DACs go together, even if the DSP does the Digital to Analogue Conversion itself as it doesn't need to be a separate chip.

Thanks. I understand DSP. I understand DACs. I own passive and active speakers.

I wasn’t trying to be offensive in calling you a Linnie! I was merely stating that your reference point products are not ones I’m familiar with. 

What would be helpful here would be a simple generic block diagram showing a digital source, an analogue source, a DAC, a pre-amplifier and then either (a) a passive set-up = power amp > passive speakers incorporating passive crossover > drivers and/or (b) an active set-up = active crossover > power amps > drivers. Then we could draw boxes around things to show some brands/models and their scope of contents, and we’d might all learn from the sharing. I might try to rustle something up later.

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Super Wammer

Start a new thread on this Nigel and I'll post up a schematic of my system too 👍

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Super Wammer
2 hours ago, TheFlash said:

Thanks. I understand DSP. I understand DACs. I own passive and active speakers.

I wasn’t trying to be offensive in calling you a Linnie! I was merely stating that your reference point products are not ones I’m familiar with. 

What would be helpful here would be a simple generic block diagram showing a digital source, an analogue source, a DAC, a pre-amplifier and then either (a) a passive set-up = power amp > passive speakers incorporating passive crossover > drivers and/or (b) an active set-up = active crossover > power amps > drivers. Then we could draw boxes around things to show some brands/models and their scope of contents, and we’d might all learn from the sharing. I might try to rustle something up later.

35 minutes ago, MF 1000 said:

Start a new thread on this Nigel and I'll post up a schematic of my system too 👍

You rang sir?

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@MartinC & @bencat ,

The reason why I called the MiniDSP a meatgrinder is because they are 24 bit. That should be plenty for normal DAC operations, but when you are doing calculations on Fourier transformed data, you suffer from data loss. It is measurable and I know from experience noticable; the music gets a bit harsher.

I'm not saying you should avoid miniDSPs because they absolutely rock at their pricepoints, and I wouldn't hesitate a second to advise someone to use a MiniDSP instead of a passive crossover. But that doesn't mean they're flawless.

I'm also not implying, nor have been, that Linn has all the solutions, because they don't. The previous generation of Linns, and the current range of less expensive DACs suffer from the exact same issue.

DSPs and digital crossovers as a species are work in progress and I expect a lot of innovation in the next decade.

As for the 48kHz, that is a somewhat religious discussion and I try to avoid those.

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9 minutes ago, Tin said:

The reason why I called the MiniDSP a meatgrinder is because they are 24 bit. That should be plenty for normal DAC operations, but when you are doing calculations on Fourier transformed data, you suffer from data loss. It is measurable and I know from experience noticable; the music gets a bit harsher.

Hi,

I checked this, and even the low cost miniDSP 2x4 HD has a floating point processor, as per the ADSP21489 400MHz Sharc DSP which seems to have 64bit width - sufficient for all calculations.

Given that most music is 16bit, the 24bit DAC's should provide adequate headroom too.

Regards,

Shadders.

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Posted (edited)
9 minutes ago, Shadders said:

Hi,

I checked this, and even the low cost miniDSP 2x4 HD has a floating point processor, as per the ADSP21489 400MHz Sharc DSP which seems to have 64bit width - sufficient for all calculations.

Given that most music is 16bit, the 24bit DAC's should provide adequate headroom too.

Regards,

Shadders.

I would advise you to start with a random 24 bit number and try to figure out what happens with it, starting with padding a lot of 0s to it, doing some calculations and transferring it back to a 24 bit number. The DACs wouldn't enjoy 64 bit numbers, so they have to lose the added weight the moment the data leaves the processor.

It is not about music being 16 bit, it is about doing math to 16 or 24 bit numbers. Just do the math, shift some bits around.

Edited by Tin

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Just now, Tin said:

I would advise you to start with a random 24 bit number and try to figure out what happens with it, starting with padding a lot of 0s to it, doing some calculations and transferring it back to a 24 bit number.

It is not about music being 16 bit, it is about doing math to 16 or 24 bit numbers. Just do the math, shift some bits around.

Hi,

Are you referring to dithering, where they do not use a triangular probability density function for the generation of the dither ?

That is something that can be added as a firmware upgrade.

Regards,

Shadders.

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2 hours ago, Tin said:

The reason why I called the MiniDSP a meatgrinder is because they are 24 bit. That should be plenty for normal DAC operations, but when you are doing calculations on Fourier transformed data, you suffer from data loss. It is measurable and I know from experience noticable; the music gets a bit harsher.

I'm not saying you should avoid miniDSPs because they absolutely rock at their pricepoints, and I wouldn't hesitate a second to advise someone to use a MiniDSP instead of a passive crossover. But that doesn't mean they're flawless.

First up, am I right to conclude that you haven't heard any miniDSP product?

For info. the two SHD miniDSPs are 32 bit. They have four outputs and so enough for a pair of 2-way active speakers but more than one would be needed for more complex setups. They are a fair bit more expensive though.

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Posted (edited)

Actually, checking the miniDSP website I believe that the 2x4 HD is 32 bit for DSP processing, whilst 24 bit for ADC and DAC stages. I've not checked through all their other products.

Edited by MartinC
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22 hours ago, MGTOW said:

I have, that is one of the dsp systems that I referred to in my post.

That a hifi company has produced components that integrate all of this into a hifi system is what I find phenomenal.

My music file player does that too... It cost me a hundred quid.

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4 hours ago, Tin said:

I would advise you to start with a random 24 bit number and try to figure out what happens with it, starting with padding a lot of 0s to it, doing some calculations and transferring it back to a 24 bit number. The DACs wouldn't enjoy 64 bit numbers, so they have to lose the added weight the moment the data leaves the processor.

It is not about music being 16 bit, it is about doing math to 16 or 24 bit numbers. Just do the math, shift some bits around.

HQ Player uses 64/80-bit floating point processing. These are processing bits.

What the f*ck is 32 bit floating?

https://audiohertz.com/2017/02/23/what-the-fck-is-32-bit-floating/

.

Analog Devices Education > Fixed-Point vs. Floating-Point Digital Signal Processing

https://www.analog.com/en/education/education-library/articles/fixed-point-vs-floating-point-dsp.html#

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7 hours ago, tuga said:

My music file player does that too... It cost me a hundred quid.

So.. why bother with expensive equipment as we all do, and not buy a JBL Boombox instead? Could it be that, .. because, you know.. improvements do matter?

Or are there some parts in stereos that for some reason are immune to upgrades? Have you found out by -wanting it to- or have you found out by -listening-?

I ask because I'm getting a bit confused whether the last part is required or frowned upon. In my experience, not all DACs are equal, and neither are all DSPs.

If MiniDSP themselves sell different versions at different price ranges, where the more expensive seems to be better, why suddenly becomes everybody agitated the moment someone suggests that there may be other brands that have even created even better versions?

Did I miss the memo that said the MiniDSP is the absolute best, cannot be improved upon, no way sirree, uhhuh, and yet.. yet.. that somehow the MiniDSP HQ is bestest?

You lot are a lot more religious towards MiniDSP than I am towards Linn, I got to tell you that.

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