Fosi Audio V3 Mono Amplifier Review

[Jimster480]

There are many variables that influence how much amplifier power someone might truly need -often more than people initially expect.

Factors like;
listening distance,
typical volume levels,
and whether a person listens to bass-heavy music all play significant roles.
On top of that, using room correction, EQ, or DSP can drastically increase power demands.

Another key aspect is speaker sensitivity, and not just the rated spec -real-world sensitivity across the full frequency range can vary a lot.

So ultimately, without knowing these specifics, it’s not really possible to make definitive statements about how much power someone else needs. Context is everything.

I suppose, but this is why I asked what he would need more power for... I suppose if you had really insensitive speakers and had An extremely large space where you need to fill it up at a loud volume then sure...

 

[Old_School_Brad]

I suppose, but this is why I asked what he would need more power for... I suppose if you had really insensitive speakers and had An extremely large space where you need to fill it up at a loud volume then sure...

Your point about power seemed rooted in your own setup and listening habits. I just wanted to highlight that others might have different needs and circumstances, so a broader perspective can sometimes be more helpful.

 

[Jeff29]

The idea, with time, would also be to add 2 more V3 mono and go on a horizontal passive bi-amp for my KEF R700.

Here is my today 2.1 setup :

Wiim ultra with RC as mentionned above...
Smsl D6 dac to V3 mono connected on XLR inputs.
KEF R700.
Subwoofer with in 50 Hz crossover .

 

[Jimster480]

Your point about power seemed rooted in your own setup and listening habits. I just wanted to highlight that others might have different needs and circumstances, so a broader perspective can sometimes be more helpful.

Sure, but I also pointed out that I can bring my speakers to ear bleeding volume.
I installed these amps in my church and I can bring the church (using the RP-8060 FA II's) with the Fosi Amps driving the Atmos + normal channel as a single channel all bridged to ear bleeding volume. And with this the amps still have headroom.
Those speakers main drivers have 98db @ 2.83V / 1m sensitivity; so they can be more sensitive than other speakers. Like the KEF R700 posted above is 89db.
I was just mentioning that it is quite a bit of wattage, unless you are driving PA speakers for concerts or something... which isn't the use case for these amps.

Now sure, there are some super insensitive speakers which would need more wattage.... but this is also why I asked them what speakers. Now they said KEF R700; which the V3 would have power to drive even with it being less sensitive.... it would drive it to ear bleeding volume even in a space as large as nearly 2400sq foot open.

The idea, with time, would also be to add 2 more V3 mono and go on a horizontal passive bi-amp for my KEF R700.

Here is my today 2.1 setup :

Wiim ultra with RC as mentionned above...
Smsl D6 dac to V3 mono connected on XLR inputs.
KEF R700.
Subwoofer with in 50 Hz crossover .

These Amps will do totally fine with this speaker setup.... Bi Amp would be even more insane.... it would be even more power lol
Amplification required: 25–200W. <--- these are the specs from KEF themselves.

 

[Old_School_Brad]

Sure, but I also pointed out that I can bring my speakers to ear bleeding volume.
I installed these amps in my church and I can bring the church (using the RP-8060 FA II's) with the Fosi Amps driving the Atmos + normal channel as a single channel all bridged to ear bleeding volume. And with this the amps still have headroom.
Those speakers main drivers have 98db @ 2.83V / 1m sensitivity; so they can be more sensitive than other speakers. Like the KEF R700 posted above is 89db.
I was just mentioning that it is quite a bit of wattage, unless you are driving PA speakers for concerts or something... which isn't the use case for these amps.

Now sure, there are some super insensitive speakers which would need more wattage.... but this is also why I asked them what speakers. Now they said KEF R700; which the V3 would have power to drive even with it being less sensitive.... it would drive it to ear bleeding volume even in a space as large as nearly 2400sq foot open.

Using speakers with a sensitivity of 98 dB requires 9 dB less power. That's 8 times less power needed than with 89 dB sensitivity speakers.

But that’s far from typical. Most home Hi-Fi speakers fall in the 85–89 dB sensitivity range, not 98 dB. PA speakers -as an example you made -are generally much easier to drive than most residential speakers.

Take a 98 dB speaker at a 3-meter listening distance, with an average listening level of 85 dB and 20 dB headroom for transients. That setup would only need less than 1 watt for the average level and around 45 watts to handle the transients.

Compare that to something like the KEF R700, which has a sensitivity of 89 dB. In the same scenario, you'd need about 4 watts average and 358 watts for transients.

Once again, context matters. Your specific use case is clearly not the norm -rather, it's the exception. That’s why it’s not helpful to make absolute statements about how much power other people need.

Of course, if you don’t listen at high volumes, you’ll need much less power. For example, aiming for an 80 dB average SPL with the same 20 dB of headroom drops the requirement to 1 watt average and 113 watts peak.

 

[Jimster480]

Using speakers with a sensitivity of 98 dB requires 9 dB less power. That's 8 times less power needed than with 89 dB sensitivity speakers.

But that’s far from typical. Most home Hi-Fi speakers fall in the 85–89 dB sensitivity range, not 98 dB. PA speakers -as an example you made -are generally much easier to drive than most residential speakers.

Take a 98 dB speaker at a 3-meter listening distance, with an average listening level of 85 dB and 20 dB headroom for transients. That setup would only need less than 1 watt for the average level and around 45 watts to handle the transients.

Compare that to something like the KEF R700, which has a sensitivity of 89 dB. In the same scenario, you'd need about 4 watts average and 358 watts for transients.

Once again, context matters. Your specific use case is clearly not the norm -rather, it's the exception. That’s why it’s not helpful to make absolute statements about how much power other people need.

Of course, if you don’t listen at high volumes, you’ll need much less power. For example, aiming for an 80 dB average SPL with the same 20 dB of headroom drops the requirement to 1 watt average and 113 watts peak.

Of course you will have different power usages based on how loud you listen.
However the specs on his speakers say 200W... So based on the specs of the speakers themselves; the amp is fine. Which is why I asked in the first place.
Now if the speakers are not efficient and are only rated for 200W then... that is the problem of the speaker designer because it means the speakers cannot get too loud without distorting or breaking.

 

[Old_School_Brad]

Of course you will have different power usages based on how loud you listen.
However the specs on his speakers say 200W... So based on the specs of the speakers themselves; the amp is fine. Which is why I asked in the first place.
Now if the speakers are not efficient and are only rated for 200W then... that is the problem of the speaker designer because it means the speakers cannot get too loud without distorting or breaking.

Relying on the power specifications listed on speakers can be quite unreliable -it’s almost like rolling a dice and multiplying the result by 100.

It’s much more effective to consider your individual expectations and requirements, taking into account the details I mentioned earlier.

 

[Jimster480]

Relying on the power specifications listed on speakers can be quite unreliable -it’s almost like rolling a dice and multiplying the result by 100.

It’s much more effective to consider your individual expectations and requirements, taking into account the details I mentioned earlier.

Never heard of this before. So you are telling me that manufacturers have no idea how much power their speakers use or can handle?

 

[tomtoo]

Never heard of this before. So you are telling me that manufacturers have no idea how much power their speakers use or can handle?

One thing is what they know the other is what they say.

 

[Old_School_Brad]

Never heard of this before. So you are telling me that manufacturers have no idea how much power their speakers use or can handle?

*Marketing.

 

[Jimster480]

*Marketing.

Right so "Marketing" would be where they OVER RATE their speakers and the ability for it to use power. Marketing is usually not dumb enough to Under-rate what the product can do.
I have seen it before, but its usually pretty rare. Either marketing is spot on, or they over rate.... which is the most common. So if the specs show 25-200W then you would imagine that likely 200W is close to the real top if not more than what the speakers should handle (or 200W is 1% THD) so based on that idea... the amp would still be fine.

Really this has been a long conversation of back and forth over a simple post suggesting to the person asking the question, that likely this has enough wattage and asking him what speakers he is using. You seem to be very interested in arguing very technical points which may not have any value and nit picking on words that other people use.
The truth of that matter is that most every single AVR, Stereo Amp, etc produces under 250W per channel.... there are very few amps which provide more power than this per channel.... especially which are not professional amplifiers for venues and bands.... even many band amplifiers don't produce more than 250W per channel.
Which again shows your propensity for arguing moot points. This amp provides power which is close to the top power offered by 95% of amps on the market. If speakers couldn't run with this amount of power, then it wouldn't be the most common power peak for most of the market.
Truth is that most bookshelf speakers don't use 50W and that most floorstanding speakers don't use 50W for most normal listening volumes.

So I would suggest that you stop creating posts with very pointless arguments about nothing. As nothing that I have said or suggested is in any way incorrect or is in any way "imposing" or "assuming" based on anything that "I have done". It is instead based on intelligent observation of the entire market, the products on the market and the actual performance of those products.... between what I have used and tested as well as what I have seen in reviews either here or elsewhere.

One thing is what they know the other is what they say.

Sure, so they will over-rate their product.... to make it look better. Meaning that their wattage claims are likely at 1% or 10% THD just like they are with most amps.

 

[Old_School_Brad]

Right so "Marketing" would be where they OVER RATE their speakers and the ability for it to use power. Marketing is usually not dumb enough to Under-rate what the product can do.
I have seen it before, but its usually pretty rare. Either marketing is spot on, or they over rate.... which is the most common. So if the specs show 25-200W then you would imagine that likely 200W is close to the real top if not more than what the speakers should handle (or 200W is 1% THD) so based on that idea... the amp would still be fine.

Really this has been a long conversation of back and forth over a simple post suggesting to the person asking the question, that likely this has enough wattage and asking him what speakers he is using. You seem to be very interested in arguing very technical points which may not have any value and nit picking on words that other people use.
The truth of that matter is that most every single AVR, Stereo Amp, etc produces under 250W per channel.... there are very few amps which provide more power than this per channel.... especially which are not professional amplifiers for venues and bands.... even many band amplifiers don't produce more than 250W per channel.
Which again shows your propensity for arguing moot points. This amp provides power which is close to the top power offered by 95% of amps on the market. If speakers couldn't run with this amount of power, then it wouldn't be the most common power peak for most of the market.
Truth is that most bookshelf speakers don't use 50W and that most floorstanding speakers don't use 50W for most normal listening volumes.

So I would suggest that you stop creating posts with very pointless arguments about nothing. As nothing that I have said or suggested is in any way incorrect or is in any way "imposing" or "assuming" based on anything that "I have done". It is instead based on intelligent observation of the entire market, the products on the market and the actual performance of those products.... between what I have used and tested as well as what I have seen in reviews either here or elsewhere.

Sure, so they will over-rate their product.... to make it look better. Meaning that their wattage claims are likely at 1% or 10% THD just like they are with most amps.

I think it's important to clarify that using your own setup as a reference for what others might need in terms of power can be misleading. I’ve shared several examples and explanations to show why that approach doesn't apply broadly.

So I wouldn’t say this is a moot point -rather, I’m adding some nuance to help others avoid common misconceptions, such as:

• Assuming speaker sensitivity of 98 dB is typical
• Thinking that needing more than a certain amount of power is unusual, when in reality it varies significantly depending on individual circumstances
• Or believing that power ratings on speaker spec sheets provide solid, universal guidance for amplifier pairing

These assumptions -which you've referenced -can unintentionally lead people in the wrong direction if taken at face value.

That’s why I believe it’s worth acknowledging that power needs can’t be generalized without considering the kinds of factors I’ve mentioned earlier. My intention here isn’t to argue for the sake of it, but to ensure the discussion reflects the real-world complexity involved. -And to help avoid misconceptions that arise from incorrect assumptions or a limited perspective.

 

[Jimster480]

I think it's important to clarify that using your own setup as a reference for what others might need in terms of power can be misleading. I’ve shared several examples and explanations to show why that approach doesn't apply broadly.

So I wouldn’t say this is a moot point -rather, I’m adding some nuance to help others avoid common misconceptions, such as:

• Assuming speaker sensitivity of 98 dB is typical
• Thinking that needing more than a certain amount of power is unusual, when in reality it varies significantly depending on individual circumstances
• Or believing that power ratings on speaker spec sheets provide solid, universal guidance for amplifier pairing

These assumptions -which you've referenced -can unintentionally lead people in the wrong direction if taken at face value.

That’s why I believe it’s worth acknowledging that power needs can’t be generalized without considering the kinds of factors I’ve mentioned earlier. My intention here isn’t to argue for the sake of it, but to ensure the discussion reflects the real-world complexity involved. -And to help avoid misconceptions that arise from incorrect assumptions or a limited perspective.

Considering that I never said any of the things that you are saying you are "adding some naunce to" I would say that it is all a moot point.
At the end of the day 95% of amps on the market don't provide more than 250W per channel. Most every speaker on the market (unless it is a large PA speaker) doesn't support wattages much higher either. Real world speaker draw is typically under 100W per channel and all of this information is COMMON and should be taken at face value for what the AVERAGE PERSON READING A THREAD WOULD NEED.

Instead you are adding tons and tons of lines of complication that only lead people to ask more questions and become more confused about things they do not understand. At the end of the day; if you need more than 200W for your speakers; you have to find some specialized setup that is not common.

So it is very important to not write long posts about absolutely nothing (as you have just done) and "add naunce" where it doesn't need to be added and try to guide people away from sound advice based in reality.
No matter which speakers you have; if you need more than 250W of power (per channel) then you are in a special use case which requires a special amp which is not a commonly available product on the market.
All of everyones favorite big amps (even Topping B200 now) doesn't really exceed 250W of power. Which is exactly what my original post was asking... what you would need all that power for. This is why originally I asked for which speaker they are using.

You have now spent 5 posts simply writing nonsense and trying to claim that I was off base in my question or recommendation. While providing literally ZERO useful information yourself.
You claimed that manufacturers don't know the specs of their speakers, and that they somehow under-inflate them. You claimed that ear bleeding volumes might be just "personal preference" and you claimed that people might need way more than 250w per channel for normal listening.
All of these are complete nonsense and total insanity.
I suggest if you are going to post on this forum (because it seems you do this all day every day) that you should get used to providing useful information, asking useful questions and doing research to help people. Rather than spending your time writing long useless posts condemning other members (just like my time that is wasted here to respond to your pointless post above again). Please stop this nonsense and keep it scientific.
Since you have nothing at all scientific to say, it would be better if you don't post anything at all, instead of clutter up threads like this.

 

[Old_School_Brad]

Considering that I never said any of the things that you are saying you are "adding some naunce to" I would say that it is all a moot point.
At the end of the day 95% of amps on the market don't provide more than 250W per channel. Most every speaker on the market (unless it is a large PA speaker) doesn't support wattages much higher either. Real world speaker draw is typically under 100W per channel and all of this information is COMMON and should be taken at face value for what the AVERAGE PERSON READING A THREAD WOULD NEED.

Instead you are adding tons and tons of lines of complication that only lead people to ask more questions and become more confused about things they do not understand. At the end of the day; if you need more than 200W for your speakers; you have to find some specialized setup that is not common.

So it is very important to not write long posts about absolutely nothing (as you have just done) and "add naunce" where it doesn't need to be added and try to guide people away from sound advice based in reality.
No matter which speakers you have; if you need more than 250W of power (per channel) then you are in a special use case which requires a special amp which is not a commonly available product on the market.
All of everyones favorite big amps (even Topping B200 now) doesn't really exceed 250W of power. Which is exactly what my original post was asking... what you would need all that power for. This is why originally I asked for which speaker they are using.

You have now spent 5 posts simply writing nonsense and trying to claim that I was off base in my question or recommendation. While providing literally ZERO useful information yourself.
You claimed that manufacturers don't know the specs of their speakers, and that they somehow under-inflate them. You claimed that ear bleeding volumes might be just "personal preference" and you claimed that people might need way more than 250w per channel for normal listening.
All of these are complete nonsense and total insanity.
I suggest if you are going to post on this forum (because it seems you do this all day every day) that you should get used to providing useful information, asking useful questions and doing research to help people. Rather than spending your time writing long useless posts condemning other members (just like my time that is wasted here to respond to your pointless post above again). Please stop this nonsense and keep it scientific.
Since you have nothing at all scientific to say, it would be better if you don't post anything at all, instead of clutter up threads like this.

While I respect your experience, I think it's important to address the assumptions that underlie your statements,

if you need more than 200W for your speakers; you have to find some specialized setup that is not common

You're implicitly assuming that most speakers are fairly easy to drive -which would require high sensitivity (e.g. 98 dB). However, most common hi-fi speakers fall in the 85–89 dB range, and in those cases, 200W may be insufficient depending on the room, distance, and desired SPL and program material not to mention EQ or room correction. So, while the statement may be true for your setup or example, it doesn't scale to all others. I've provided calculation examples of this.

Real world speaker draw is typically under 100W per channel and all of this information is COMMON and should be taken at face value for what the AVERAGE PERSON READING A THREAD WOULD NEED.

This generalization overlooks scenarios where higher power is not at all exotic. Speakers with difficult impedance curves, large listening spaces, or users wanting high dynamic headroom for music or film playback can and do benefit from more power especially when factoring in real-world voltage drops and phase angles. Not to mention what you would need for transients or bass heavy content.

the specs on his speakers say 200W... So based on the specs of the speakers themselves; the amp is fine.

In reality, those numbers are very rough estimates. Taking spec-sheet values at face value is not wise. Unfortunately. That's on the manufacturers. You can for example look at compression graphs on Erins Audio Corner to see what I mean.

Spoiler: Example: Polk R700 Compression measurement

I bring nuance to the discussion by pointing out that amplifier power needs are context-dependent. While your points may hold true for your environment, generalizing them can mislead others with very different setups. It's thus worth emphasizing that speaker sensitivity, room acoustics, and listening habits all play major roles in determining how much power is “enough.”

Rather than dismissing higher power needs as excessive, we should encourage others to evaluate their individual requirements -not just spec-sheet assumptions or assumptions made by out own demands. -Please notice I do not mention if 100 W or 1000 W is more appropiate, but encourage to assess needs on an individual basis.

While you might view my comments as clutter, I see it as valuable nuance -and I genuinely believe this approach offers a more accurate way to assess power needs.

 

[Jimster480]

While I respect your experience, I think it's important to address the assumptions that underlie your statements,



You're implicitly assuming that most speakers are fairly easy to drive -which would require high sensitivity (e.g. 98 dB). However, most common hi-fi speakers fall in the 85–89 dB range, and in those cases, 200W may be insufficient depending on the room, distance, and desired SPL and program material not to mention EQ or room correction. So, while the statement may be true for your setup or example, it doesn't scale to all others. I've provided calculation examples of this.



This generalization overlooks scenarios where higher power is not at all exotic. Speakers with difficult impedance curves, large listening spaces, or users wanting high dynamic headroom for music or film playback can and do benefit from more power especially when factoring in real-world voltage drops and phase angles. Not to mention what you would need for transients or bass heavy content.



In reality, those numbers are very rough estimates. Taking spec-sheet values at face value is not wise. Unfortunately. That's on the manufacturers. You can for example look at compression graphs on Erins Audio Corner to see what I mean.

Spoiler: Example: Polk R700 Compression measurement

View attachment 445524

I bring nuance to the discussion by pointing out that amplifier power needs are context-dependent. While your points may hold true for your environment, generalizing them can mislead others with very different setups. It's thus worth emphasizing that speaker sensitivity, room acoustics, and listening habits all play major roles in determining how much power is “enough.”

Rather than dismissing higher power needs as excessive, we should encourage others to evaluate their individual requirements -not just spec-sheet assumptions or assumptions made by out own demands. -Please notice I do not mention if 100 W or 1000 W is more appropiate, but encourage to assess needs on an individual basis.

While you might view my comments as clutter, I see it as valuable nuance -and I genuinely believe this approach offers a more accurate way to assess power needs.

Please Provide a list of amplifiers that provide more than 250 watts per channel, which are audiophile grade and approved of here on this forum with objective measurements.
Each one must have power outputs greater than the Fosi V3 per channel.

I'll be waiting on your list as actual contribution to this thread.

 

[Old_School_Brad]

Please Provide a list of amplifiers that provide more than 250 watts per channel, which are audiophile grade and approved of here on this forum with objective measurements.
Each one must have power outputs greater than the Fosi V3 per channel.

I'll be waiting on your list as actual contribution to this thread.

I’m having a bit of trouble understanding the purpose of the question. Many amplifiers can deliver over 250 W dynamically, and without specifics like impedance, it’s hard to respond meaningfully. It feels a bit like it’s heading toward a ‘gotcha’ rather than a constructive discussion, and I’d really prefer to keep things focused and helpful.

It might be a good time to wrap up this conversation.

 

[rsqt]

Even a speaker with only 90dB/1w is loud. The problem is the ear which is about 10-15dB down in the deeper bass. That means for 1W at 1kHz you need 10-40W in the bass. The tone engineer in the studio mixes the music and kompensates this with higher levels in the bass. Adding to these 10-40W the dynamic jumps of 10-20dB you need 100 to maybe thousands watts for a ground level of 90dB (depending on speakers and your ear).

Thats why I have a fully active Hornsystem with DBA (4x22" from 20-45Hz and 18x10" from 45-120Hz in the front). No level problems any more.

 

[Jimster480]

I’m having a bit of trouble understanding the purpose of the question. Many amplifiers can deliver over 250 W dynamically, and without specifics like impedance, it’s hard to respond meaningfully. It feels a bit like it’s heading toward a ‘gotcha’ rather than a constructive discussion, and I’d really prefer to keep things focused and helpful.

It might be a good time to wrap up this conversation.

You can't produce a list because it doesn't exist. I'm calling you out as a troll. This conversation is over. You cannot contribute anything meaningful as I mentioned some posts ago.
It is just obvious that you are trolling the entire forum, the more I look at your posts; you have been here for months and done basically nothing but troll every single thread that is active.
z

Even a speaker with only 90dB/1w is loud. The problem is the ear which is about 10-15dB down in the deeper bass. That means for 1W at 1kHz you need 10-40W in the bass. The tone engineer in the studio mixes the music and kompensates this with higher levels in the bass. Adding to these 10-40W the dynamic jumps of 10-20dB you need 100 to maybe thousands watts for a ground level of 90dB (depending on speakers and your ear).

Thats why I have a fully active Hornsystem with DBA (4x22" from 20-45Hz and 18x10" from 45-120Hz in the front). No level problems any more.

This is exactly why subwoofers are active these days. There are very few passive ones, since it makes more sense to build a dedicated circuit for the subwoofer. Especially which can handle the high wattage of huge bass, which would be able to be controlled and capped.
Considering that almost every speaker amp on the market doesn't really provide more than 250W..

 

[RickS]

Please keep on topic here and avoid personal attacks.

It is just audio folks. If you find yourself stressed, take a break from here.

Thanks!

 

[damarfi]

Please Provide a list of amplifiers that provide more than 250 watts per channel, which are audiophile grade and approved of here on this forum with objective measurements.
Each one must have power outputs greater than the Fosi V3 per channel.

I'll be waiting on your list as actual contribution to this thread.

Most of the Hypex amps have more output than 250 wats per channel and all are audiophile grade.
Here is spec of Apollon NCx500st
Power rating: 675W @ 2ohm | 650W @ 4ohm | 380W @ 8ohm