Hi All,
As always I should start with a big thanks for all the knowledge provided within these threads - such an amazing resource.
I'm in the process of designing a set of 3-Way active speakers and am trying to get my head around the best way to power these, previously I've only built passive speakers with an active cross over so this is all very new to me. I'm trying to keep the build relatively cheap - just to see what's possible on a bit more of a budget - but can stretch the budget if necessary, I've come up with a couple of ideas, explored below and would like some input as to whether my approach is feasible or if I should explore some other options.
Driver ratings are roughly 100W sub, 50W mid, 20W tweeter.
Option 1:
Each speaker has a 100W per Channel amp board. One channel for mid / high (this channel has a cross over and a high pass filter on mid), 2nd channel is exclusively for the bass driver with a low pass filter. I've attached a schematic of what I think this would like.
Thinking to use either of the following amp boards:
100W Amp board 1
100W Amp board 2
With maybe this power supply or something similar
Power Supply
Option 2:
I use a plate amp, installed into one of the speakers, I'd then just connect the other speaker to this plate amp via the 'Link' port.
500W Plate Amp
This is of course a slightly cheaper option coming in at maybe half the price of option 1, however I'm unsure as to the quality of this amp, I'm unable to find detailed specifications on it and haven't used the website previously, so who knows what that'd be like. I also think that designing the cross over for this option would be far more involved, although perhaps I'm wrong about this.
The only other thing I think I'd need to take into account is the difference in internal volume betw. the speaker with the amp and the one without.
So, are there any issues with the above approaches? Which would you go for? I'm also open to others (budget allowing) - I guess there's things like mini DSP or just making them passive (although would really like self contained units on this build).
Many thanks,
Lawrence
As always I should start with a big thanks for all the knowledge provided within these threads - such an amazing resource.
I'm in the process of designing a set of 3-Way active speakers and am trying to get my head around the best way to power these, previously I've only built passive speakers with an active cross over so this is all very new to me. I'm trying to keep the build relatively cheap - just to see what's possible on a bit more of a budget - but can stretch the budget if necessary, I've come up with a couple of ideas, explored below and would like some input as to whether my approach is feasible or if I should explore some other options.
Driver ratings are roughly 100W sub, 50W mid, 20W tweeter.
Option 1:
Each speaker has a 100W per Channel amp board. One channel for mid / high (this channel has a cross over and a high pass filter on mid), 2nd channel is exclusively for the bass driver with a low pass filter. I've attached a schematic of what I think this would like.
Thinking to use either of the following amp boards:
100W Amp board 1
100W Amp board 2
With maybe this power supply or something similar
Power Supply
Option 2:
I use a plate amp, installed into one of the speakers, I'd then just connect the other speaker to this plate amp via the 'Link' port.
500W Plate Amp
This is of course a slightly cheaper option coming in at maybe half the price of option 1, however I'm unsure as to the quality of this amp, I'm unable to find detailed specifications on it and haven't used the website previously, so who knows what that'd be like. I also think that designing the cross over for this option would be far more involved, although perhaps I'm wrong about this.
The only other thing I think I'd need to take into account is the difference in internal volume betw. the speaker with the amp and the one without.
So, are there any issues with the above approaches? Which would you go for? I'm also open to others (budget allowing) - I guess there's things like mini DSP or just making them passive (although would really like self contained units on this build).
Many thanks,
Lawrence
Attachments
Considering this and the general concept of active speakers why (on earth) would you use expensive passive filters? "Active" is all about active filters!
Edit: have a look at rod elliott's article (called "bi-amping" which may be confusing, but it's about active speaker systems):
https://sound-au.com/bi-amp.htm
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Please note this solution, which is designed for three-way digital active speakers.
https://www.diyaudio.com/community/threads/3-way-dsp-amp.415065/#post-7734938
https://www.diyaudio.com/community/threads/board-3-way-dsp-amp.415079/
Thanks for the input - @stv I hadn't yet got round to researching the cost of passive XO components so assumed that if they just consisted of electrical components eg. resistors/capacitors that the cost of a single amp board per speaker + XO parts would be less than that of active XO + multiple amp boards per speaker. Thanks though, I guess I'll have to research power supply + XO options / prices all at once.
@uriy-ch thank you - that does indeed look interesting and perhaps the simplest method I've seen so far. I'll have to drop you a message privately with some questions as there's definitely some bits within those threads that go a bit over my head.
Other than what has been pointed out, is there anything actually wrong with Option 1 or 2 that I outlined above?
@uriy-ch thank you - that does indeed look interesting and perhaps the simplest method I've seen so far. I'll have to drop you a message privately with some questions as there's definitely some bits within those threads that go a bit over my head.
Other than what has been pointed out, is there anything actually wrong with Option 1 or 2 that I outlined above?
You can ask a question in the topic about these amplifiers, and if you want, you can ask questions in private correspondence, I will answer what I know.
Please clarify the question. It is difficult for me to guess what you want to have in the end.
Technically, it will work.
The stereo amplifiers that you have chosen to implement your active speaker system are implemented on the same TDA7498 power chip. Much depends on your sound requirements and your sensitivity thresholds to nonlinear distortions.
Nonlinear distortions of this chip at 3 kHz and 1 W power are 0.18%, usually such distortions are heard as strongly accentuated "Sssss" that can cut the ear, but here a lot depends on the speakers themselves and your sensitivity threshold and the genre of music.
In addition, your approach will greatly complicate the fine-tuning of your active speaker system. The passive filter will interfere with the alignment of the acoustic centers between the three speakers and to achieve synchronicity of all speakers, you will have to study for a very long time the methods of compensating for the phase shift using digital sound preprocessing.
A 500W plate amplifier is a single-channel amplifier for a subwoofer, it has one amplifier output of 500W. As a rule, such amplifiers have a very bad situation with distortions at frequencies above 300 Hz and the noise level at the output is higher than that of amplifiers with lower power.
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Thank you ! I didn't realise it was a sub amp, it's misleading that it's advertised as a full range amp then.
ok interesting so that's a relatively high level of distortion on that amp board then. Looks like I'll need to do a lot more reading to get a grip of phase shift compensation... as always, one questions leads to many more!
That's great though, was mostly looking for someone to poke holes in my logic or point out things I hadn't considered so thankyou - really appreciate the response
ok interesting so that's a relatively high level of distortion on that amp board then. Looks like I'll need to do a lot more reading to get a grip of phase shift compensation... as always, one questions leads to many more!
That's great though, was mostly looking for someone to poke holes in my logic or point out things I hadn't considered so thankyou - really appreciate the response
https://www.diyaudio.com/community/...oup-delay-using-reverse-iir-filtering.417505/
Yes, that's true.
I used FIR division in my three-way speaker system. FIR does not change the phase at the frequency of the band crossover, which saved me from many difficulties in fine-tuning the speaker system.
It does add an overall delay.
Especially when a lot of taps are being used.
So you have to take this into consideration when combining different elements.
Yes, of course, I know about it. I am in the near listening field and I did not use very steep cutoffs, i.e. I used only 512 taps to get the steepness of the cutoffs that met the requirements for suppressing the speakers in the frequency band I needed. The signal delay is only 512/48000 Hz = 10 ms.
I checked the division of the bands using different digital IIR filters, and in the end I liked the way FIR works the most, FIR eliminates many problems associated with IIR band division. But I have nothing against IIR division, it is purely a matter of taste and requirements for the final result.
I think that for a situation when the FIR pre-ringing is jarring to the ear, but there is an urgent desire to get a flat phase, then you can use a subtractive filter and thereby get a flat phase without FIR, i.e. without pre-ringing. But no matter how you look at it, to get an even phase you need to use active band division, and this is easiest to do with the help of DSP, which in turn gives greater freedom in choosing tools to achieve a particular goal.
Cool! yeah that's quite a nice approach! 🙂 👍
I always just mention it, because a lot of other people don't realize this.
The delay is only determined by the amount of taps vs sample rate, so the steepness isn't that much of an issue anymore seen from a delay point of view.
That is mostly only an issue with an high amount of taps as well as picking the wrong window type.
I often use a hybrid approach.
Meaning a FIR filter for midrange+high-side and IIR for crossover between midrange and low-end.
This also works with passive filters 🙂
As b_force pointed out you could try a hybrid approach, because the most expensive parts are usually the woofer coils and caps. Good low resistance coils for low crossover frequencies can be incredibly expensive.
So you could use an active x-over and separate amp for woofer and mid/high and only one amp and a passive x-over between midrange and tweeter.
Don't forget how the impedance always messes up the response as well.
Getting a good crossover below 500Hz is not easy and definitely not a fun thing to do.
A 4th (or at least 3rd) order LP for the woofer is also very beneficial.
I have even done such hybrids that the bafflestep + param EQ blocks were done actively, and only the LP/HP parts were done passively.
So you really only need a few components.
If you don't care much about efficiency (aka see the entire system like a passive filter) you could add a passive attenuator for the tweeter to improve the SNR (noise) of amplifier as well.
The distortion will also be better with a passive filter.
The purpose of active crossover is not to save costs.
The fact that you use multiple power amplifier to drive the drivers individually means higher cost more often than not.
By using line level crossover before the power amplifiers, each amplifier only needs to take care of signal of a limited frequency range.
They can be optimised for the specific purpose and hence provide better performance.
https://dynaudio.com/magazine/2017/may/the-benefits-of-an-active-crossover
Contrary to what was said in the article, when you DIY, you always have completely free choice of components and design.
See also :
https://www.linkwitzlab.com/crossovers.htm
"I have a strong preference for line level active dividing networks ahead of the power amplifiers. In this approach the power amplifier output is connected directly - except for a very low resistance speaker cable - to the voice coil of the driver. The amplifier takes maximum control over the motion of the speaker cone which gives a greater sense of clarity and dynamism compared to a passive dividing network between amplifier and driver. Active crossovers make much more effective use of amplifier power. A clipping woofer amplifier is not seen by the tweeter, which has its own amplifier. The clipping of the woofer amplifier may not even be noticed in this case. It would surely be heard with a passive crossover, where it might even overheat and damage the tweeter, because of the large amount of high frequency energy in the clipped signal."
Patrick
The fact that you use multiple power amplifier to drive the drivers individually means higher cost more often than not.
By using line level crossover before the power amplifiers, each amplifier only needs to take care of signal of a limited frequency range.
They can be optimised for the specific purpose and hence provide better performance.
https://dynaudio.com/magazine/2017/may/the-benefits-of-an-active-crossover
Contrary to what was said in the article, when you DIY, you always have completely free choice of components and design.
See also :
https://www.linkwitzlab.com/crossovers.htm
"I have a strong preference for line level active dividing networks ahead of the power amplifiers. In this approach the power amplifier output is connected directly - except for a very low resistance speaker cable - to the voice coil of the driver. The amplifier takes maximum control over the motion of the speaker cone which gives a greater sense of clarity and dynamism compared to a passive dividing network between amplifier and driver. Active crossovers make much more effective use of amplifier power. A clipping woofer amplifier is not seen by the tweeter, which has its own amplifier. The clipping of the woofer amplifier may not even be noticed in this case. It would surely be heard with a passive crossover, where it might even overheat and damage the tweeter, because of the large amount of high frequency energy in the clipped signal."
Patrick
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Not always, a lot depends on the speaker itself and on the passive filter components themselves.
Moreover, the level of nonlinear distortions that can be suppressed by the required crossover filter may be simply insignificant, and sometimes, on the contrary, the crossover filter may slightly increase nonlinear distortions.
Calculate how much a high quality stereo crossover costs (especially around 200-500Hz).
You're easily hitting 80 bucks a piece (so times two)
If we stay in the DIY world anyway, now look at the costs of some 2nd hand amplifiers.
Hell even some well performing new amplifiers are pretty affordable these days.
I was referring to this;
https://purifi-audio.com/blog/app-notes-2/low-distortion-filter-for-ptt6-5x04-naa-11
Well that is only the summary.
Plenty of other people (incl myself) tested this, and it works.
You can find that here on the forum.
So a passive filter can actually lower the distortion of the driver significantly.
Obviously depending on the type of distortion, but cone break-up is one that often gets in the way even when it's out of the passband.
But I agree that it needs a bit more context.
It's only hard to say things without writing a whole page of text that way 🙂
Well, both my active crossovers and power amps cost a lot more than 80 bucks.
https://www.diyaudio.com/community/...ogue-active-crossover-filter-solution.329458/
https://www.diyaudio.com/community/...approach-the-build-thread.208880/post-6136583
80 bucks would not even buy a 300VA custom toroidal transformer.
🙂
Patrick