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Topic: Revive Logitech subwoofer and satellites with after market amp - will it work? (Read 414 times) previous topic - next topic
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Revive Logitech subwoofer and satellites with after market amp - will it work?

I'm a bit of an audio noob (or have fallen back down there since it's been decades).

 
My ancient Logitech Z2300 2.1 system recently gave up the ghost. It makes no discernible noise when switched on, but the power light on the cabled remote (an non OEM replacement) still comes up. I've pulled the subwoofer speaker out and looked at the circuit board but can't find any obvious fault, and don't really know what I'm doing with my multimeter, beyond testing that the switch on the back isn't faulty. There are no obvious bulgy capacitors or heat damage/burn marks.

However, rather than learn how to fix it, I'm thinking I'd lke  to just use the subwoofer and speakers which ought to still work fine to hook up to something like this https://fosiaudio.com/products/bt30d-bluetooth-5-0-2-1-channel-power-amplifier-with-bass-and-treble-control?_pos=1&_sid=b6c1652bf&_ss=r Fosi_BT30D bluetooth amp.


 
I would be removing the the coil (the big heavy copper coil bolted to wall of cabinet) and circuitry of the old board inside the zx2300, as these would be scrap now - or is that heavy coil actually part of how a sub woofer works?.

 
Then I'd like to plug the speaker cables from the subwoofer into the passive subwoofer outlet on the new amp, and similarly the satellite speakers into the passive speaker outlets. Is this going to work or would I need a separate subwoofer amp to make the subwoofer speaker work as an active subwoofer?

 
Would these 2 satellite speakers and 1 subwoofer be a good match for this amp? Or is a 10W per channel increase likely to blow those satellites at volume? Similarly, will a bass output of only 100W cf the original 120W be too weak or create undesireable load on the amp?

Or is there another amp I can get to serve this purpose.  Happy to go to any links you can provide to upskill my understanding.

 
Logitech z2300 specs:
Audio Quality Certification: THX certified
Total RMS Power: 200W [FTC Rated Power]
System THD: Better than 0.05% before clipping
Total Peak Power(RMS): 400W less than 10% THD
Power distribution: 120 W (Subwoofer) + 2 X 40 W (Satellites)
Subwoofer: 120 W @ 8 ohms @ 10% THD @ 100Hz
Subwoofer Size (inch): 8
Subwoofer Type: Long throw
Satellites: 80 W (2 X 40 W) @ 8 ohms @ 10% THD @ 1kHz
Satellite Size (inch): 2.5
Satellite Type: Polished aluminum phase plug driver
Frequency response: 35 Hz - 20 kHz
Signal to noise ratio(SNR): @ 1kHz at 100dB
Sound Pressure Level (SPL): 117db
Subwoofer dimensions(HWD): 11" X 11" X 15"
Satellite dimensions(HWD): 6.75" X 3.5" X 6"
Total weight : 15 Kg

 
The fosi amp has the following specs:
Model: BT30D
Chippest:TPA3116D2
Maxpower Output: 50W*2+100W
THD: 0.05%@output 1W; SNR ≥98dB
Working Voltage: 12-24V
Speakers Frequency Response: 20Hz-20kHz(±3dB)
Bass Cutoff Frequency Range Adjustment: 40-300Hz
Device Dimension: L118 x W132 x H35 mm/4.72 x 5.2 x 1.38inch
Input mode: Bluetooth/RCA
Output mode: Passive Speakers + Passive/Active Subwoofer
Bluetooth: Bluetooth 5.0, up to 15m/49ft wireless range without hindrance
Easy Connection
Bluetooth Network Name: FOSI AUDIO
Wireless Range: Up to 15m/49ft.
Works with All of Today’s Latest Bluetooth Devices(IOS, Android, Smartphone, Pad, Tablet etc.)

Re: Revive Logitech subwoofer and satellites with after market amp - will it work?

Reply #1
Your plan sounds reasonable...

Quote
would be removing the the coil (the big heavy copper coil bolted to wall of cabinet) and circuitry of the old board inside the zx2300, as these would be scrap now - or is that heavy coil actually part of how a sub woofer works?.
Usually a coil is part of a passive crossover (or part of a power supply) but in any case you shouldn't need it.

Quote
Then I'd like to plug the speaker cables from the subwoofer into the passive subwoofer outlet on the new amp, and similarly the satellite speakers into the passive speaker outlets. Is this going to work or would I need a separate subwoofer amp to make the subwoofer speaker work as an active subwoofer?
That's a 3-channel amplifier so you're good with a passive sub.

Quote
Or is a 10W per channel increase likely to blow those satellites at volume? Similarly, will a bass output of only 100W cf the original 120W be too weak or create undesireable load on the amp?
I think you'll be fine.   I generally don't trust wattage ratings for amplifiers or speakers anyway...  ;) And speaker ratings are "complicated" because they are based on musical peaks.  You can usually fry a speaker with constant test-tones, especially the tweeter which can't handle as much power as the woofer (or midrange).

According to my handy-dandy spreadsheet going form 120W to 100W is a change of -0.79dB. 

Re: Revive Logitech subwoofer and satellites with after market amp - will it work?

Reply #2
The big "coil" is the transformer for the amp. Yes, you can jettison since the amp is dead, but it's not necessary unless you want to shed dead weight for the sake of it. There will be wires running from it to plate amp that you would have to cut. I'd say leave it be. Same for the plate amp on back.
The only thing you really need to do, is unscrew/remove the subwoofer driver (woofer) and disconnect, desolder or cut the wires going to it. Pay attention to the polarity, which is +/-. Then you need to run wires from FOSI sub out to the woofer. Maintain the correct polarity. Luckily you have a port on the sub that you can route wires through. Otherwise, you will have to get those wires into the sub box in some way. You could drill as small a hole as needed underneath and run wires through. Ported subs are not as critical with small "leaks" like this.
Then run wires from FOSI L/R speaker out to satellites. Again, maintaining polarity. I would guestimate a 150-200hz setting on Sub Freq (crossover) would be ok, given the competing interests between small satellites and localization. That was most likely where they were crossed originally, but  you can "tweak" that setting by ear.
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