"Aliexpress" Subwoofer Plate Amp Review

[amirm]

This is a review and detailed measurements of a generic subwoofer amplifier from Aliexpress. It is on kind loan from a member costs roughly US $160 to $190.

There are a ton of products with the same backpanel and features but different guts. Maybe the owner can chime in with which version this is. The closest I could match is this one.

The feature set is startlingly good with even balanced pass through!

For testing I set the gain to around 25 dB (was hard as this is start of the gain knob) and left crossover at max as you see in the picture above.

We have no reference for this type of amplifier. Fortunately the owner sent me two others from Parts Express which I will measure soon.

Subwoofer Plate Amp Measurements
Since I had used 40 Hz for bass performance of full range amps, I decided to stay with that for our dashboard. I also limited the bandwidth to 11 kHz.

We see spray of harmonic distortion setting SINAD. They continue well to 500 Hz and above, which gets them out of simultaneous masking, assuming the sub driver plays them.

Noise performance is nothing to write home about even though again, I limited bandwidth to 11 kHz:

Frequency response shows that there is some kind of high pass filter which we don't want in a subwoofer amp:

Heaven help you if your room has a mode at 60 Hz to to go with that peak!

Power curve is kind of odd: (test frequency: 40 Hz)

At least it doubles into 2 ohm:

For our burst frequency, I used the 50 Hz tone from CEA-2006:

It oddly produced less power.

Just sitting there, the amp's SINAD goes up and down:

Conclusions
The feature set of this plate amp is great for an analog product. Performance though, is not anything to write home about, albeit may not matter as much for a sub. Power output of 200 watts is modest for a 4 ohm subwoofer. 2 Ohm doubles that if there is no price to pay on the driver end with this impedance.

Will have to see how brand name products perform before making a recommendation one way or the other.

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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

 

[TonyJZX]

subwoofer 'ethics' sound, you say that word but you dont know what it means

i'm not all that into subs even though i have several all over the place but is XLR common?

 

[amirm]

i'm not all that into subs even though i have several all over the place but is XLR common?

It is as the sub is likely to be at a distance with its own power supply: perfect recipe for hum.

 

[Grenadine]

Fun. I am the owner/donor. I use this amp in the garage with a Dayton 15” mx15-22 in a 5ft3 ported enclosure and some CSS critons 1-TDX, it plays stupidly loud, and purely for fun, DIY build. I believe I paid $125 a few years ago for the ethics plate amp. It’s been reliable for heavy use. Cannot say that about other reputable brand plate amps, including Bash class d 500 watt which needed repair very soon after minimal use, as well as, 2 Dayton 300 watt sub plate amps were sent back for warranty replacement. Aliexpress amp is very slim compared to the Dayton plate amps, I believe a height of around 1.75" with feet. Here’s the link to the listing I'm not surprised by the results. I have another one of these on bass shaker duty, it does the job. I had low expectations when purchasing, and ive been satisfied for what i'm using them for. In the real world, such as in a garage where I'm using power tools, and the washing machine is going, all I hear is clean, and deep low end response from 15" ported sub:

https://aliexpress.us/item/3256802620301301.html

From the product listing: "A low-cut is also designed, which cuts all the frequency below 15Hz and converts the energy to the frequency range of 25Hz-60Hz"

Edited for spelling corrections and added details.

 

[JSmith]

Interesting... thanks for the testing Amir. Could be a bit better, but likely fine for sub duties.

This appears to be the one;

US $136.25 - $138.19

https://www.aliexpress.com/item/1005002806616053.html

I am the owner/donor.

Cheers for sending it in.


JSmith

 

[milosz]

Weird FR. Just weird.

 

[pma]

+2.5dB, just a bit of "boom" effect.

 

[MCH]

I buy a lot of small electronics from AliExpress, but, or maybe hence, I would be very concerned about plugging a 360w device like this at home.
It would be interesting to read what knowledgeable members here think of the power supply etc if good pictures of the internals are posted.
Thanks for the review though, these sort of reviews could one day discover a hidden gem.

 

[Sokel]

Not bad at all for what it is.
Whoever thinks that the price is fair though, just remember the older YZ (or something like it) older generic plate amps found in every el. shop.

Those had way higher quality, toroidal trafos, decent components, a gazillion of options and I/O , etc and were about half the price of this one.
It would be a better option, for sure, even without the filters.

Thanks Amir!

 

[AudioSceptic]

Fun. I am the owner/donor. I use this amp in the garage with a Dayton 15” mx15-22 in a 5ft3 ported enclosure and some css critons tdx1, it plays stupidly loud, and purely for fun, diy build. I believe I paid $125 a few years ago for the ethics plate amp. It’s been reliable for heavy use for years. Cannot say that about other reputable brand plate amps, including Bash class d 500 watt which needed repair very soon after minimal use. Here’s the link to the listing:

https://aliexpress.us/item/3256802620301301.html

View attachment 546021

Thanks for submitting this, but were you disappointed in any way with the measurements? The FR seems really odd, I must say.

 

[Matias]

Thanks for the owner for sending and of course Amir for testing! This plate amp series of reviews is going to be a nice refresher from the usual DACs and amps we see here.

 

[Azrael]

Frequency response shows that there is some kind of high pass filter which we don't want in a subwoofer amp:

I guess I don't count among that "we," since I wouldn't want to do without a high-pass filter—especially with bass-reflex subwoofers—and certainly not if it isn't a model tuned to a particularly low frequency.

However, such a high-pass filter should be freely configurable, as is possible with DSPs. I usually set the high-pass filter’s frequency and slope so that the driver's amplitude below the tuning frequency fb does not exceed that above it. I'm only evaluating this through simulation, but so far nothing has broken, even at extreme levels.

For a home audio system that I also wanted to be suitable for parties, I built two compact subwoofers, each equipped with a B&C 12TBX100. The tuning frequency fb is around 40 Hz. Since music sometimes contains frequencies that are lower than that, and because the driver excursion increases significantly below fb, a high-pass filter was essential. The achievable volume is no longer mechanically limited, but is restricted almost exclusively by the driver's thermal capacity (and that's not exactly small in the 12TBX100).

The following graph shows a Q&D simulation in WinISD—in this case, for cone excursion. Blue shows the result without a high-pass filter, and red shows the result with one:

I also have four bass-reflex subwoofers in the living room, each equipped with an Eminence LAB12. However, their low-frequency response is so low—around 25 Hz—that I haven't used a high-pass filter with them so far.

The high-pass filter on the plate amplifier tested here is, of course, completely unsuitable for something like that, mainly because it can't be freely configured. I just want to say: High-pass filters can sometimes be extremely helpful for subwoofers, too.

 

[jbrown]

I would LOVE to see a test of the Dayton Audio SPA500DSP that is supposedly identical to the amp used in the Wilson Lōkē subwoofer.

Dayton Audio SPA500DSP
Wilson Lōkē Subwoofer

 

[Tell]

Weird FR. Just weird.

Sure it's quite odd, but seeing that one should really measure and EQ the bass for optimal performance that wonky FR doesn't really matter that much.

 

[sealman]

I guess I don't count among that "we," since I wouldn't want to do without a high-pass filter—especially with bass-reflex subwoofers—and certainly not if it isn't a model tuned to a particularly low frequency.

However, such a high-pass filter should be freely configurable, as is possible with DSPs. I usually set the high-pass filter’s frequency and slope so that the driver's amplitude below the tuning frequency fb does not exceed that above it. I'm only evaluating this through simulation, but so far nothing has broken, even at extreme levels.

The high-pass filter on the plate amplifier tested here is, of course, completely unsuitable for something like that, mainly because it can't be freely configured. I just want to say: High-pass filters can sometimes be extremely helpful for subwoofers, too.

I think a configurable high pass filter would be great as an option for subwoofer plate amp or even a standard amp if designed for a sub.
The key is configurable.
I have not been in the market for a sub amp in a while but I would have gladly paid extra for that option when I was.
Does Audyssey or Dirac have a configurable high pass option?

 

[Timcognito]

Wow a new category of testing. DIY guys are going to love ASR for this. Great Amir, keep them coming as there are a number of small and inexpensive plate amps on the market.

 

[kboe]

This high-pass is commonly called subsonic filter ;-)
In this case it is set quite high though.
In budget amps this filter is sometimes designed with some overshoot to give small boxes a little more oomph at the bottom end. So not all too unusual IMHO.
If one had the schematics a change of filter frequency should be feasible by changing a few capacitors.

 

[Azrael]

This high-pass is commonly called subsonic filter ;-)
In this case it is set quite high though.

In my country, this once used to be called a 'Rumpelfilter'. In any case, it’s a filter that was primarily built into amplifiers in the past to prevent excessive excursion of the woofer, for example, when a vinyl record was warped.

It wouldn’t be suitable for specifically limiting the excursion of bass-reflex speakers below the tuning frequency fb, because fb can vary from speaker to speaker.

For the design I mentioned above using the B&C 12TBX100, for example, I implemented a second-order high-pass filter with a cutoff frequency of about 35 Hz. (*edit*: ....if I remember correctly.)

In this case, therefore, the high-pass filter on the Plate amp tested here would be set too low.

*edit2*:
I’ve just realised who I’m replying to. So there’s no need for me to tell anything about ‘Rumpelfilter’.

 

[amirm]

The problem with the high-pass filter is that it is overshooting and is undocumented as far as response. You sim your subwoofer, then go and test it with this amp and get something different because the sim assumes flat amplification (perfect voltage source).

 

[kemmler3D]

I could maybe overlook the noise and distortion for a sub amp, but the FR is too odd for my taste...