Ok, I'm brand new here so hello everyone and thanks in advance for any ideas.
So... Call me insane, but I have a 50 watt Marshall AS50R Acoustic Soloist acoustic guitar amp/auxiliary amp which I used as a sub for my PC's audio setup for years via the two RCA inputs on channel 2.
It always did a wonderful job but after it accidentally got stored in a damp basement mold grew inside the box so I had to pull the amp out of the box.
The stock speakers inside of it still sounded ok, but looked pretty nasty and smelled even nastier so I trashed them.
The stock speakers were two 8" custom voiced and a tweeter all wired up to the amps single 4 ohm output channel.
I replaced those with a single 4 ohm Pioneer TS-W303R 12" subwoofer which is rated at 250 watt RMS and 1200 watt peak.
Once I hooked that speaker to the amp It seems the chip is getting a lot hotter, and it'll cut out on loud bass hits which sounds like a clicking sound if I turn the amp above half volume. so I haven't been using it.
I KNOW for a fact the ohms are matched because I downloaded the PDF for the amp from Marshall which stated the output is 4 ohm, and the box the speaker came in says 4 ohm.
A friend told me that if the box the speaker is mounted in is sealed the trapped air can cause more resistance causing the amplifier chip to overheat.
so not having a hole saw and not wanting to have a nasty looking hole in my brand new speaker box my quick fix was to raise the speaker out of the box half an inch by putting two 1/4" thick bolt nuts under the speaker screw holes then screwing the speaker down through the nuts.
This let a good bit of air travel in and out of the box as I could tell by shortly testing the amp at quarter volume, but the problem still persists.
If I leave the amp below half volume the bass sounds amazing, but I wont use it other than to test the problem for a short period of time.
Any advice would be VERY much appreciated as this amp was my fathers who passed away and I'd like to be able to get some good use out of it.
The impedance quoted by a manufacturer is only approximate. The impedance of a speaker always follows a plot against frequency.
The next issue is that in any reactive load, and a speaker is one, voltage and current are out of phase. This leads to a gap between actual power consumed and apparent power. Unfortunately the current for the apparent power has to be provided by the amp. The wider the phase angle, the greater the margin between actual and apparent power.
The next issue is that I doubt your speaker is properly matched to the enclosure.
Your old guitar instrument speaker, almost certainly had a stiff suspension and low Qt and was likely quite efficient.
Now all drivers have what is known as Thiel/Small parameters, that describe certain mechanical and electrical aspects of the driver. Some drivers need to be in a ported enclosure and some sealed, some can be either. Now correct tuning raises the impedance in the sub range.
Here you can see the
Dayton RSS315HF-4 12" four ohm woofer in a properly modeled vented box. If you look at the impedance curve you will see two peaks of impedance with the null at the driver's free air resonance frequency Fs.
Here is the same driver in a sealed enclosure.
You will see just one peak of impedance.
Your plan creating an air gap between cabinet and driver makes no sense and will make things worse.
If you want to use that driver you need to find the T/S parameters so the correct enclosure can be modeled. I can find no parameters for this driver, but it is apparently designed for a sealed enclosure of 0.85 to 1.75 cu.ft. internal volume.
In the end I suspect however your guitar amp is not designed for subwoofer drivers, but instrument speakers. Instrument speakers make very poor subwoofer drivers.
If you want to use that woofer, I would buy a subwoofer amp.
