Stereo amp and active sub wont work at high volume

danamal

Commendable
Feb 6, 2017
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hello
I have a 2x15W sterio amp which is hooked up to 2 wharfedale diamond 9 bookshelf speakers (power handling = 75W). This system works fine, however i just brought a dynamics 100W active sub. As my amp has no subwoofer output, i connected both the sub and the speakers to the 4 speaker wire inputs on the sub. This works fine at a low volume level but when its turned past half way both the speakers and the sub cut out. I have a limited understanding about speakers but my best guess is that my amp is too low powered? But i dont want to buy a new one and still have this problem.
 
@ 2X 15 Watts, the amp is hideously under powered. It is probably either going into thermal cut out, or the amp is just shutting off due to the excessively high power demand. Both will lead to the same answer! It will be a safety measure to protect the amplifier.
 
@ 2X 15 Watts, the amp is hideously under powered. It is probably either going into thermal cut out, or the amp is just shutting off due to the excessively high power demand. Both will lead to the same answer! It will be a safety measure to protect the amplifier.
 

danamal

Commendable
Feb 6, 2017
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1,510
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Sweet, thanks for your help. Ill look into getting a new amp. How much power would you recommend for the new amp.
 
No problem, glad to help.
Any normal 2 channel stereo amp will do, and seeing as your sub is active, you need only be concerned with your two wharfedale speakers. These speakers are rated at 6 Ohms, so make sure you get an amp that is capable of powering at that resistance! And you wouldnt need much more than 150 Watts (RMS) in power to drive these speakers perfectly well.
 

danamal

Commendable
Feb 6, 2017
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is that 150W per channel or total?
 

danamal

Commendable
Feb 6, 2017
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1,510
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hey, sorry to be a pain with my lack of knowledge,
but this website-
https://www.cnet.com/products/wharfedale-diamond-9-0-speaker/specs/

says that the recommended Amplifier Power is 15 Watt for the diamond 9s.
I believe this is why i brought the 2x15W amp in the first place.
The back of the speakers say that the "power handeling" is 75W,
is cnet simply incorrect? or am i missing something?

Thanks
Daniel
 

danamal

Commendable
Feb 6, 2017
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yeah sure,
so the sub is a dynamics bsw-8000, i brought it second hand and cannot find a link to it sorry, the specs shown on the back are-
power: 100W and frequency response: 40~150Hz.

the amp is a digitech aa-0487
https://www.jaycar.com.au/2-x-15-watt-rms-portable-stereo-amplifier/p/AA0487

Also just to clarify the speakers are the wharfedale diamond 9.0 bookshelf speakers.
 

madmatt30

Honorable
Yeah mate , I think your little amp is underpowered in all honesty.

Those diamond 9s are real HiFi Speakers at the end of the day , & I know it says 15-75w but theyll take 50-60w rms to run properly at the end of the day.

See the sub , what ports does it actually have on the back mate , all the pics are too low res to see properly .

Generally sub's with speaker level inputs should have speaker level outputs too ,if they don't then you're pretty much drawing double from the amp.

You can part rectify this by wiring amp to left right speaker , & running from the back of the speaker to the sub - so you're running in series rather than parallel (with 4 lots of cable from the back of the amp) .

However with this being an active sub , you are better running to the left/right line in from the original source & not even using the amp to power it at all.
 

danamal

Commendable
Feb 6, 2017
9
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1,510
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Yeah this sub only has speaker level inputs along with the rca iputs, I will definitely look into a new amp. Could u please clarify what you said-

"you are better running to the left/right line in from the original source & not even using the amp to power it at all".

Sorry im not very failure with speaker jargon.

Thanks
Daniel
 

madmatt30

Honorable
^ you can use the powered sub without the amp mate.

You're running a 3.5mm jack into that amp from the source as a input to the amp ??

Split that 3.5mm source into 2 with a splitter , run a 3.5mm to twin rca directly to the subwoofer for the source.

You bypass the amp for the subwoofer completely then - all you lose is the ability to control the sub volume from the amp.
 


I see the source that you go the information from, and I am convinced they got it wrong. These speakers are definitely 75W Per channel. Other sites including the manufacturer's state they are in fact 75w.

Regards,
Kenton.
 

danamal

Commendable
Feb 6, 2017
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So i went with your idea, with the 3.5mm splitter. This worked perfectly and the sub shook the floor of my uni dorm last night. I am now looking into getting another amp.

Thank you so much to everyone that helped
Daniel

 
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