What’s this Amps 8 ohm RMS? Help


I got this amp it’s says 1200w Max blah blah…

The actual rms is 2x

200w for 2omhs

I got a sub coming that’s 200rms 400max
It should be fine, the amp got 2 speaker outputs and it’s 2-16omh amp, could I run my sub from one speaker output and my 4x30rms watt 3way coaxial 4omhs speakers from the second channel?

Running the coxial speakers at 8omhs will make them take 60rms, just not sure can’t find the amps 8omh load rms but am guessing from the image above it’s somewhere 70watt at 8omh

Please correct me if am wrong

This is for home project I already am running my coxial speakers with a cheap amp.
could I run my sub from one speaker output and my 4x30rms watt 3way coaxial 4omhs speakers from the second channel?

That seems rather a strange thing to do with a stereo amplifier.

The car amp is possibly capable of delivering 75 W into an 8 ohm load.

Do you intend to wire two 4 ohm, 30 W coaxial speakers in series to give you an 8 ohm, 60 W capable combination?

P.S. 60 W speakers can be run from a 75 W amp provided you do not max out the volume control!
@Galu yes exactly how you say it

I got those coaxial speakers thinking they are 210watt max 😅but after doing my research the max don’t matter as they are 30watt rms, and I set them up in a 2.1 class d amp 2x50+100watt amp now am getting a sub and got this amp that use to be my friends

So it’s either I use the Thunder 2125 with a sub and the coaxial speakers


I use the to amps together with rca receiver that will let me run them of Bluetooth


A question:How much power would it need because this is a AB amp it’s 60% efficient right? If my sub is running 200rms+60rms from my coaxial speakers, then 12v 40ah power supply should do right?
The class of the amp (AB or D) is irrelevant, the power supply must simply be able to supply sufficient current to drive the amp at the required volume.

The amount of power delivered to your speakers depends on the setting of the volume control and can vary from a small fraction of a watt at low volume, up to the amplifier's full rated power at an unbearably high voluime!

At comfortable listening levels, your speakers will only draw a few watts from the amp. Turn up the volume and the speakers will draw more power.

I would reckon that a 12V, 40 Ah battery, as used in small cars, is beefy enough to use as a power supply.
@Galu thanks for your help

Just couple more questions, am going to run it off power supply not a battery but the power supply is 12v 40ah it should be even better as it’s constantly giving power.

Also, the amps speaker channel outputs are separate right? Because if am running…

One channel running 4omhs for sub
One channel running 8omhs for speakers

This should be okay?
Mains operated power supplies are rated by current, i.e., in amps (A). Batteries are rated by charge capacity, i.e., in amp hours (Ah).

So, do you mean your power supply is 12V, 40 A?

It is OK to run 4 ohm off one channel and 8 ohm off the other, if that's what you really want to do.

P.S. I was hoping that by now you'd be spelling your "omhs" correctly! ;)
Thanks for the photos.

I see a pair of coaxial speakers at either end of the bench, and can see how you could place a sub box in the middle - that's cool! :cool:

For stereo reproduction, you would connect one pair of coaxial speakers to the RH channel of a stereo amp and the other pair to the LH channel.

The sub would have to be connected to its own, dedicated low pass filtered amp.

This can be achieved using your existing 2 x 50 W + 100 W class D amp. The 2 x 50 W section is the stereo amp and the 100 W section is the low pass filtered subwoofer amp.

I'm not sure if the Thunder TCA-2125 car amplifier can perform the same function as above. I would need to know more about it and its connections, but all the details I can find appear to be written in Bulgarian. I can, however, translate "Автомобилен усилвател" as "Car amplifier"! :D

Your suggestion of connecting the sub to one channel of the Thunder and the coaxial speakers to the other doesn't quite make sense to me, I'm afraid.


That’s the amps connections, I was thinking to use the 2x50+100watt amp for coaxial speakers and the Thunder 2125 amp for sub.

Using a Bluetooth receiver that supports RCA and Aux inputs

I use the 100watt output from the Class D amp for leds

Would that be the best option?


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So, you intend to use a low pass filtered output from one of the channels on the Thunder to power the sub?

And to use the 2 x 50 W section of your class D amp can power the coaxial speakers in stereo?

Your initial descriptions puzzled me, but you seem to be on the right track.

As for powering the LEDs, I'll leave that entirely up to you! :cool:

Good luck with your project. Do let us know how it turns out.

From simple logic amps inside sub box don’t get affected as there is no moving parts in the amp, because I want it inside the box then being outside, Also if so it don’t affects amps same should go for the power supply right.

Main point is that I want to put my amp and supply in the box just worried that may affect it
Getting the stuff, not the coming Thursday but the one after it will take couple days to build it

About the active sub box’s, am sure they designed to not have much heat, so guessing class d amp and a power supply that would provide the watts it needs

But for me my amp is class AB which is 65% max efficient rest goes to heat also the power supply providing 12v 40A is ganna heat up on a hot day, both amp and power supply will be in there own little sections closed off

Am thinking about adding one or 2 small fans to keep the air circulation in the amp box and in the power supply box, as I need to make the box a little more for better performence as the sub is ds18 slc8 and it says 0.9ft3 for ported, I have about 2ft3 in the box, so by adding amp and power supply it will make it cleaner safer and will take some space inside, making it 1.5ft3 I ran that in the Winsl program and it’s just right
Yes, most active speakers seem to use class D amps and switch mode power supplies, which cuts down the heat generation.

It also seems to result in active speakers failing a lot, as evidenced by the experience of several members of this forum.

Glad to see you're taking the problem of heat generation and the volume occupied by the electronics into account.


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Yeah it was 70£ when I found it now it’s 35£ it’s a steal I mean for a outside table and a little project it will do well.

Am ganna have 2 7x60cm acrylic panels on the sides ganna echt in a design and let leds light it up when base comes on :p ganna look sweet.

I would just put them on each side without boxing them off but I need it to take space, if I left them open to the sub that would constantly refill the air in the box that would cool it down more.

And thanks, I done watch a lot about all thes amps and speakers now, 😂😂 before I thought u twist the speaker wires together and just put in a input 🫣 now I know ohms and rms and so much more it’s cool stuff, good to know about active subs, this amp is also part of a semi active speaker, as I seen this amp should be with its sub 1200w sub saw a pic online whiles trying to find info on the thunder amp, my mum did have it but the cone ripped couple years back so they kept the amp and gave it to me 😎trying to make the most out of it

Can’t wait to hear it ganna be my first sub box 🥹
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Width: 31.5cm
Hight: 20cm

So on the short sides I’d like it to be some what symmetrical, one side ganna have the port 20x8cm plus a fan then do some what same on the other side just no port

Am thinking of using a fan to pull out air, so if I make a small hole (on the long side of the box) it won’t be noticed, if it will it will be symmetrical so both sides have same thing so it won’t catch the eye much, therefore keeping it all closed of from the main sub enclosure 🫡