Hello everyone.
I have been given a sub Sony SS-WS53 that was part of a 5.1 home cinema system.
The issue I have is that its impedance is 1.5 ohm which is quite difficult to drive, or let's say to find cheap amps for.
The lowest I found seems to be a TPA3116D2 and TPA3118D2 with an admissible 1.6 ohm and a nominal 2 ohms impedance when in PBTL.
Most of the others amps have a 4 ohms minimal load impedance.
I understand that if I put a 2.5 ohms 100W resistor in series with my sub, I would loose 2.5/4 = 62% of the power of the amp in heat. So a 100W amp becomes a 28W.
Do you have any recommendation ? (except maybe changing my sub)
Thanks
I have been given a sub Sony SS-WS53 that was part of a 5.1 home cinema system.
The issue I have is that its impedance is 1.5 ohm which is quite difficult to drive, or let's say to find cheap amps for.
The lowest I found seems to be a TPA3116D2 and TPA3118D2 with an admissible 1.6 ohm and a nominal 2 ohms impedance when in PBTL.
Most of the others amps have a 4 ohms minimal load impedance.
I understand that if I put a 2.5 ohms 100W resistor in series with my sub, I would loose 2.5/4 = 62% of the power of the amp in heat. So a 100W amp becomes a 28W.
Do you have any recommendation ? (except maybe changing my sub)
Thanks
Impedance matching transformer though will still have some loss and assume you'll have to DIY since these have been 'out of fashion' since the late '60s unless there's electronic ones nowadays.
Proper solution is to make a 1 ohm happy power amp.
By the way, what Sony must have made, what else?
Practical needs:
Sony specs say (from https://www.manualslib.com/manual/1099178/Sony-Ss-Ct52.html#product-SS-WS53) :
SS-WS53
Speaker system Bass reflex, magnetically
shielded
Speaker unit 200 mm (7 7/8 inches) dia.
cone type
Rated impedance 1.5 ohms
Since it´s a "non standard" speaker, let´s think some "non standard" solutions.
In no particular order:
* get another and use them in series.
* paralleling two TPA311x drives 2 ohm or somewhat less ... I suggest you parallel four of them, in the usual configuration: 1 Master, 3 Slaves, doubled current capacity power supply.
* do it the DIY macho man way: take one classic design, such as one of excellent APEX ones, say it drives 100W into 4 ohm, or the popular Rodd Elliott one, and double (or triple) power transistors , adding individual emitter resistors for even current sharing.
You should reduce rail voltages by 20% or so, we are not trying to make a very high power amplifier,
Back in the 70s I made 400W into 1 ohm Bass amplifiers, using 8 x 2N3055 and driving 2 x 4 x 12" speakers cabinets each one 2 ohm
By the way, what Sony must have made, what else?
Practical needs:
Sony specs say (from https://www.manualslib.com/manual/1099178/Sony-Ss-Ct52.html#product-SS-WS53) :
SS-WS53
Speaker system Bass reflex, magnetically
shielded
Speaker unit 200 mm (7 7/8 inches) dia.
cone type
Rated impedance 1.5 ohms
Since it´s a "non standard" speaker, let´s think some "non standard" solutions.
In no particular order:
* get another and use them in series.
* paralleling two TPA311x drives 2 ohm or somewhat less ... I suggest you parallel four of them, in the usual configuration: 1 Master, 3 Slaves, doubled current capacity power supply.
* do it the DIY macho man way: take one classic design, such as one of excellent APEX ones, say it drives 100W into 4 ohm, or the popular Rodd Elliott one, and double (or triple) power transistors , adding individual emitter resistors for even current sharing.
You should reduce rail voltages by 20% or so, we are not trying to make a very high power amplifier,
Back in the 70s I made 400W into 1 ohm Bass amplifiers, using 8 x 2N3055 and driving 2 x 4 x 12" speakers cabinets each one 2 ohm
Not even need to simulate
, circuit looks good and has gobs of output current capability.25V rail will push 15A maximum/peak into a 1.5 ohm load, so 5 A per power transistor ... well within its capabilties.
Follows the
suggestion which is the classic, solid approach
Well, yes.
That´s why I suggested starting with the circuit of a 100W/4 ohm amp since it basic structure already is in the ballpark of what we need (while the often suggested around here TPA311x does not, "you have what you have"), and both:
* adding more transistors for increased current handling
* lowering rail voltages, since,precisely, "we don´t want a 300W amp"
Suggested (as examples) APEX amps or ESP´s, simply because there are PCBs available (or their design) adding extra power transistors is reasonably easy even for an average builder, just bolt them to heatsinks, wire them in parallel with existing ones, and add needed emitter resistors, which of course will not fit the original PCB (they are not expected) using , say, tagboards or terminal strips.
Of course your example is excellent and I said so, simply it will need custom designing and fabricating a PCB, the "boosted" already existing PCB may look slightly clumsy with 4 external transistors and resistors ... no big deal
That´s why I suggested starting with the circuit of a 100W/4 ohm amp since it basic structure already is in the ballpark of what we need (while the often suggested around here TPA311x does not, "you have what you have"), and both:
* adding more transistors for increased current handling
* lowering rail voltages, since,precisely, "we don´t want a 300W amp"
Suggested (as examples) APEX amps or ESP´s, simply because there are PCBs available (or their design) adding extra power transistors is reasonably easy even for an average builder, just bolt them to heatsinks, wire them in parallel with existing ones, and add needed emitter resistors, which of course will not fit the original PCB (they are not expected) using , say, tagboards or terminal strips.
Of course your example is excellent and I said so, simply it will need custom designing and fabricating a PCB, the "boosted" already existing PCB may look slightly clumsy with 4 external transistors and resistors ... no big deal
I have the same 1.5 ohm sony sub I ended up putting a car stero in my room it works great now
Ultimately, yes. At these low voltages (<100V) you can get a couple milliohms Rds(on) if you’re willing to drive 15000 pF. In principle not a big deal at subwoofer frequency. But P-channel devices aren’t that good. To go all N channel with rail to rail class AB makes for more complicated drive circuitry.
If you’re not trying to go R-2-R and can put up with 3-5 volts drop, just make life easier for yourself with bipolars.
If you’re not trying to go R-2-R and can put up with 3-5 volts drop, just make life easier for yourself with bipolars.