Fosi Audio V3 Mono Amplifier Review

[rolfrander]

Just how do you work that out? I've never heard of a x/over, active or passive ever built into a pre-amp.

MiniDSP does this. I suspect that high-end AVR/AVP-products might be able to as well.

 

[EddNog]

…I've never heard of a x/over, active or passive ever built into a pre-amp…

Never seen this:

Parasound New Classic 200Pre

Discover the Parasound New Classic 200 Pre, a versatile high-performance preamplifier with phono input, analog bass management, and a dedicated subwoofer output. Perfect for enthusiasts seeking clarity and precision in their audio setup.

store.parasound.com

Or this:

BasX PT2 Stereo Preamp/DAC/Tuner

Welcome to Emotiva Audio Corporation. Home Audio Systems, Speakers & Accessories and more. We use science to evoke the true emotion behind every note.

emotiva.com

?

-Ed

 

[gwing]

99.99 of course (99% of the remainder.)

Strictly speaking probably 99.95% as 5% is usually counted as the statistically significant level.

 

[NTK]

Because the crossover for the speakers would be in two places.

Wdym?

Bi-amping a pair of bi-amp-able speakers is perfectly fine, even without an external, active crossover.

The passive crossover built into the speakers is designed specifically for this purpose.

To give a bit more explanation to Zek's concern, the external cross-over in the preamp will introduce different phase shifts in the signal feeding the LF and HF inputs of the loudspeaker (as proposed in Fosi Audio's post #2055), which can screw up the phase alignment of the summed speaker output.

Below are some possible effects on adding Butterworth LPF and HPF to the 2 amplifiers, the intents of which is to filter out HF for the LF amplifier and LF for the HF amplifier. The phase shifts caused by these additional cross-over filters resulted in a cancellation notch at the cross-over point when these filters are combined with the cross-over filters in the loudspeaker. The top graphs (left - magnitude, right - phase) show the outputs of a 2-way LR4 cross-overs with cross-over frequency of 400 Hz. The bottom graph shows the outputs with the additional Butterworth LPF or HPF is cascaded to the LPF and HPF of the LR4 cross-over -- notice the cancellation notch at cross-over.

 

[somebodyelse]

Can you help me check if this diagram shows the right connection of bi-amping using 4 sets of V3 Monos? We're going to make a video to introduce it.
View attachment 374697

What exactly do you mean by bi-amping? To me it it involves speakers with passive crossovers, but separate terminals for HF and LF. In this case there is no crossover before the amps - the input to the amps is full range. I don't see how this is supposed to improve anything, but you can do it with commonly available hifi speakers.

Speakers designed to be used with an active crossover before the amps are rather uncommon in hifi, but do at least make sense.

 

[Down South]

Please don’t create this HOW to video Fosi without first articulating WHY one might do this. I believe that anyone who owns the distinctly exotic equipment necessary for bi amping to provide ANY real benefits does not need such a howto video. Likewise, anyone who needs the howto does NOT own gear that would benefit

 

[Down South]

If active wire/somebodyelse/NTK/mike70 would actually read Rod Elliot's explanation for bi-amping before posting they may then decide not to post.

Check out his ESP Philosophy (simplified) section and then if you think you can add anything do so.

 

[NTK]

If active wire/somebodyelse/NTK/mike70 would actually read Rod Elliot's explanation for bi-amping before posting they may then decide not to post.

Check out his ESP Philosophy (simplified) section and then if you think you can add anything do so.

Elliott's article is about the advantages of full active speakers (with active cross-overs feeding line level signals to the power amplifiers). It does not address the (problems of the) proposal by Fosi and is therefore irrelevant to this discussion.

 

[activewire]

If active wire/somebodyelse/NTK/mike70 would actually read Rod Elliot's explanation for bi-amping before posting they may then decide not to post.

Check out his ESP Philosophy (simplified) section and then if you think you can add anything do so.

Well according to Rod Elliot:

The most common question I get is "Do I need to disconnect the passive crossover in my speakers?"
The answer is ... Yes, otherwise you are not really biamping at all.

I stand by my statement

anyone who owns the distinctly exotic equipment necessary for bi amping to provide ANY real benefits does not need such a howto video. Likewise, anyone who needs the howto does NOT own gear that would benefit.

 

[mike70]

Well according to Rod Elliot:

That's what I said ... so, I don't regret my post at all.

 

[DavidMcRoy]

Fosi Audio’s diagram does not indicate speakers with passive crossovers built-in. It appears to show active crossovers feeding amplifiers which feed a woofer and a tweeter per channel.

 

[antcollinet]

Just think of the energy bouncing around inside the bass enclosure.

I think you'll find it's a rare speaker cabinet that uses materials that will contain any EM field within it, let alone bounce it around.

 

[LSPhil]

To give a bit more explanation to Zek's concern, the external cross-over in the preamp will introduce different phase shifts in the signal feeding the LF and HF inputs of the loudspeaker (as proposed in Fosi Audio's post #2055), which can screw up the phase alignment of the summed speaker output.

Below are some possible effects on adding Butterworth LPF and HPF to the 2 amplifiers, the intents of which is to filter out HF for the LF amplifier and LF for the HF amplifier. The phase shifts caused by these additional cross-over filters resulted in a cancellation notch at the cross-over point when these filters are combined with the cross-over filters in the loudspeaker. The top graphs (left - magnitude, right - phase) show the outputs of a 2-way LR4 cross-overs with cross-over frequency of 400 Hz. The bottom graph shows the outputs with the additional Butterworth LPF or HPF is cascaded to the LPF and HPF of the LR4 cross-over -- notice the cancellation notch at cross-over.

View attachment 374775

I think every preamplifier has a way to adjust the crossover frequency or switch it off. Even if you don't pay attention, when you reverse the polarity of the tweeter, for example, a small error of -3dB occurs, but the load capacity increases by 12dB. Biamping brings with it the ingenious possibility of adjusting the high frequency range depending on the age of the person.

 

[Down South]

Well according to Rod Elliot:

I stand by my statement

Which is incorrect. If you had not cherry picked but had posted what Rod said it would have included what he said - if you want to go 'fully active' THEN you disconnect the passive x/over entirely - otherwise you leave the mid/tweeter section of the x/over in place.

My post was 'that if you want to 'try bi-amping' you will get a real taste of what is possible. Using 3 amps - one for bass, one for mids and one for the tweeter, than go active. The guy from Fosi has two way speakers, so using 4 amps makes sense. I think using 4 monos is overkill but why shouldn't he try that configuration.

My speakers use Tonigen ribbon tweeters that are now properly sealed from the mids which is also sealed from the bass section - there is an awful lot of energy generated by the bass unit. The wiring is protected from this energy inside FEP tubing. If you were to attach sensors to the wiring and as usual the passive x/over plate you would soon see just how much the function of the bass unit, inside it's enclosure generates sound pressure which changes in intensity all the time aka energy is moving/shifting. The Sextet has a downward firing port at the bass. If there was no energy being generated by the bass transducer there would be no point in having ports of any kind.

 

[JeremyFife]

Can you help me check if this diagram shows the right connection of bi-amping using 4 sets of V3 Monos? We're going to make a video to introduce it.
View attachment 374697

Hi @Fosi Audio
It's your product and your marketing strategy.

My only comment is that the key information here is that the crossover is before the amplification. Implicit is that there is no crossover in the speaker. That's not made very clear in your diagram, it's easy to miss.

I would appreciate your professionalism if you made that very clear, and made it equally clear that there is little benefit (if any?) in bi-amping when there is still a passive crossover downstream of the amplification.

 

[gwing]

Hi @Fosi Audio
It's your product and your marketing strategy.

My only comment is that the key information here is that the crossover is before the amplification. Implicit is that there is no crossover in the speaker. That's not made very clear in your diagram, it's easy to miss.

I would appreciate your professionalism if you made that very clear, and made it equally clear that there is little benefit (if any?) in bi-amping when there is still a passive crossover downstream of the amplification.

You are of course entitled to your opinion, on the other hand there are others who would really quite like to have a high pass filter in their pre-amp specifically to drive normal speakers with inbuild passive crossovers in conjunction with a sub.

 

[SMen]

You are of course entitled to your opinion, on the other hand there are others who would really quite like to have a high pass filter in their pre-amp specifically to drive normal speakers with inbuild passive crossovers in conjunction with a sub.

I think that this whole topic probably needs its own thread. Fosi posted one for suggestions regarding a pre-amp (I am presuming) for the v3 monos here: https://www.audiosciencereview.com/...-a-balance-preamplifier-should-be-like.47481/

But the whole subject of active crossovers would be beyond this also.

 

[JeremyFife]

You are of course entitled to your opinion, on the other hand there are others who would really quite like to have a high pass filter in their pre-amp specifically to drive normal speakers with inbuild passive crossovers in conjunction with a sub.

That's nothing to do with my comment

Agree that high/low pass filtering in amp for the purpose of subwoofer integration is a very nice feature. There are signs that more inexpensive equipment is offering this now, or at least talking about it, which is brilliant.

Nothing to do with bi-amping though, at least nothing in relation to my comment on Fosi's diagram and proposed video

 

[activewire]

Fosi Audio’s diagram does not indicate speakers with passive crossovers built-in. It appears to show active crossovers feeding amplifiers which feed a woofer and a tweeter per channel.

Sincere question: where does one purchase such speakers as this?

 

[mike70]

It would be interesting a thread about speakers with the possibility to bypass the passive crossover.
I think you only have the DIY path.