I have a blown set of PSB Alpha PS1 powered bookshelf speakers. They popped and died one day when I touched the aluminum volume knob after walking across the carpet with socks in winter. Oof.
They're nothing wildly special, but I like the way they look, and as a tinkerer, I'm thinking it might be fun to get them to make noise again. Most internet folks say it's a lost cause with powered speakers. There's either not enough technical information about the components, making it hard to pair the drivers and crossovers with a proper amp, etc, or the juice just isn't worth the squeeze. I'm not sure. Not having opened them up yet, I don't know what I'll find in there (not exactly easy to open), but could I feasibly turn these into passive speakers, or (possibly) repair the onboard amp and give them new life?
Thanks for your patience. Very new to this side of audio.
They're nothing wildly special, but I like the way they look, and as a tinkerer, I'm thinking it might be fun to get them to make noise again. Most internet folks say it's a lost cause with powered speakers. There's either not enough technical information about the components, making it hard to pair the drivers and crossovers with a proper amp, etc, or the juice just isn't worth the squeeze. I'm not sure. Not having opened them up yet, I don't know what I'll find in there (not exactly easy to open), but could I feasibly turn these into passive speakers, or (possibly) repair the onboard amp and give them new life?
Thanks for your patience. Very new to this side of audio.
Welcome to the forum.
I presume the speaker is opened by removing the rear panel. You may find labels stuck to the tweeter and woofer magnets which give the part numbers, although that is unlikely to be of much help.
The nearest passive equivalent appears to be the PSB Alpha B1: https://www.diyaudio.com/community/threads/psb-alpha-b1-internal-pic.137546/
Without access to measurement equipment (as the experts will stress in the following posts!), it will not be possible to come up with the perfect crossover. However, if you just want to "tinker" with these speakers and get them up and running passively at minimum cost, you could possibly use the Alpha B1 crossover as a rough guide.
Even if you possess the required knowledge and skills, repairing the onboard amp is unlikely to be cost effective in component terms.
I presume the speaker is opened by removing the rear panel. You may find labels stuck to the tweeter and woofer magnets which give the part numbers, although that is unlikely to be of much help.
The nearest passive equivalent appears to be the PSB Alpha B1: https://www.diyaudio.com/community/threads/psb-alpha-b1-internal-pic.137546/
Without access to measurement equipment (as the experts will stress in the following posts!), it will not be possible to come up with the perfect crossover. However, if you just want to "tinker" with these speakers and get them up and running passively at minimum cost, you could possibly use the Alpha B1 crossover as a rough guide.
Even if you possess the required knowledge and skills, repairing the onboard amp is unlikely to be cost effective in component terms.
Thank you, Galu.
So apparently they're super easy to open. I had tried once after they blew, but after removing the back panel screws, it seemed they were glued or fused to the plastic cabinet, and I gave up for a while. Today the panel just popped right off when the screws were out.
I've only a foggy idea of what I'm looking at here, but if anyone can decipher the printed circuit board or the crossovers, I'd love to know what you find. PSB website says this is a 20w RMS amp.
Could I theoretically bypass the stock amp and connect wire terminals to the crossovers of each speaker and power these with a stand-alone 20w mini stereo amp?
So apparently they're super easy to open. I had tried once after they blew, but after removing the back panel screws, it seemed they were glued or fused to the plastic cabinet, and I gave up for a while. Today the panel just popped right off when the screws were out.
I've only a foggy idea of what I'm looking at here, but if anyone can decipher the printed circuit board or the crossovers, I'd love to know what you find. PSB website says this is a 20w RMS amp.
Could I theoretically bypass the stock amp and connect wire terminals to the crossovers of each speaker and power these with a stand-alone 20w mini stereo amp?
Attachments
Have both speakers gone dead or just one?
It's difficult diagnosing things like this at a distance... you would need first of all to check that the supply voltage is present. Assuming that is OK then most likely the main power amp chip has failed.
Whatever lives under that small metal heatsink will be the main power amp and I think I can see some coils on the main PCB (not those on the crossover) which suggests the power amp is a Class D 'switching' type of amp. Replacing that is probably something you couldn't do without familiarity and practice. Perhaps worth a look for curiosity though.
You can use an ordinary amp with the crossover. Just locate the two wires that go from the crossover to the main board and feed the audio into there,
It's difficult diagnosing things like this at a distance... you would need first of all to check that the supply voltage is present. Assuming that is OK then most likely the main power amp chip has failed.
Whatever lives under that small metal heatsink will be the main power amp and I think I can see some coils on the main PCB (not those on the crossover) which suggests the power amp is a Class D 'switching' type of amp. Replacing that is probably something you couldn't do without familiarity and practice. Perhaps worth a look for curiosity though.
You can use an ordinary amp with the crossover. Just locate the two wires that go from the crossover to the main board and feed the audio into there,
Yes, as Mooly describes.
I can now see that the active speaker contains a passive crossover.
The secondary speaker is passive, so I'm assuming it's unharmed. The only input to that speaker is the proprietary speaker cable (looks very similar to the power cable) that runs from the "master" speaker. Not sure what this type of cable is called, but it exits the master speaker from the terminal at the top right corner in the last image of the circuit board (to the right of the volume pot). The power cable enters from the terminal in the bottom right (to the right of the USB port).
Hopefully. Speakers get damaged when the power amp puts a high DC voltage across the speaker. It's probably OK but easy to check.
I assume just a light gauge twin cable. It's nothing special, just lightweight and flexible.
If I bypass the amp, do I need to be too concerned with driver impedance? This amp here specifies speaker impedance between 4-8ohms. Would it be safe to assume these drivers would be within that range? If not, would a multimeter give an accurate impedance reading?
Impedance is really a dynamic figure rather than a fixed value. The impedance is actually different depending on the applied frequency of the signal. A meter simply measures the DC resistance presented at the terminals. I would guess yours are fairly low impedance in order to maximise the available output given the low voltage the amp has to work with.
An 8 ohm speaker (for example) might have a minimum impedance of 5 or 6 ohms at some frequencies and be as high as 30 or 40 ohms at others.
An amp that is 4 ohm rated should be fine.
An 8 ohm speaker (for example) might have a minimum impedance of 5 or 6 ohms at some frequencies and be as high as 30 or 40 ohms at others.
An amp that is 4 ohm rated should be fine.
I'll just add that if you measure the DC resistance (DCR) with your multimeter and add on one third of that reading, you will arrive at a figure that is pretty close to the nominal impedance (Z) of the speaker. For example DCR = 6 ohm gives Z = 8 ohm.
The replacement woofer appears to be PSB AL 82-IT (as used in the passive Alpha B1). Can you verify the model number?
You may have to search for a second hand woofer as illustrated below, but a Canadian listing would be your best bet.
https://reverb.com/item/34970318-ps...-5-al82-for-alpha-b1-black-bookshelf-speakers
However, check the diameter. Is yours really a 3.5" woofer?
You may have to search for a second hand woofer as illustrated below, but a Canadian listing would be your best bet.
https://reverb.com/item/34970318-ps...-5-al82-for-alpha-b1-black-bookshelf-speakers
However, check the diameter. Is yours really a 3.5" woofer?
