Hi everyone,
I want to share with you my experience of the last half a year spent modifying these "monitors" made by Phonic. After reading the only review online ( Test: Phonic P8A - Studio - AMAZONA.de ) I acquired them for something like 200$ which I considered to be a goo deal. And it is, to certain extent - the P8A have some issues.
Let's start with the bad:
Now the good:
So now that I had a pair of crappy speakers, some spare money and a huge motivation to learn more about speaker building, I started modifying the hell out of them. Here's what I did:
See attchments 2 and 3 for what I ended up with. I'm very pleased with the sound and new appearance of the speakers, it was a long but very interesting journey to this point, with some quite radical design choices. There are things I'd do different now but that's probably the case with just about any project.
If anyone is interested, i can post some (a lot) more details.
K.
I want to share with you my experience of the last half a year spent modifying these "monitors" made by Phonic. After reading the only review online ( Test: Phonic P8A - Studio - AMAZONA.de ) I acquired them for something like 200$ which I considered to be a goo deal. And it is, to certain extent - the P8A have some issues.
Let's start with the bad:
- Unknown origin metal dome tweeter, slightly different model in each speaker (!) that sounded extremely harsh
- Front firing ports are non-functional. The extremely cheap plastic they were made of was all warped, God know how someone could manufacture this. (No photos, I threw them away but trust me those were THE worst imitations of ports I've seen)
- Extremely unpleasant sound, with weak bass, elevated 1kHz range I had my ears hurt after an hour of listening.
- The crossover was all over the place, I have the transfer function of xovers, see attachments. Obviously the "24dB/oct LR" is a bit overstated in the specs. Not to mention the ridiculous 15dB boost at 20kHz.
Now the good:
- Reasonable build quality, nice finish of the cabinet box.
- Very nice and compact amp design with toroid transformer (I'd estimate about 250W), all enclosed in nice metal casing.
- Plenty of circuitry to play with (2xTDA7293 for bass, another one for the tweeter, auto-off circuit, overload protection, plenty of opamps in the signal path to play with)
- Nice looking woofer with cast frame, from the looks identical to the one used in Behringer B2031 ( http://i836.photobucket.com/albums/zz286/my_graphs/Behringer B2031P/DSC03709.jpg?t=1290059946 )
So now that I had a pair of crappy speakers, some spare money and a huge motivation to learn more about speaker building, I started modifying the hell out of them. Here's what I did:
- Relocated the ports to the sides of the cabinet, changing them to 4cm PVC tubing in the process (WinISD helped a lot)
- Completely refinished the cabinets
- Laid about 1" of rockwool on inside walls
- Changed the tweeters to Seas 27TFF
- Completely redesigned the crossover and settled on a mixed active/passive solution
See attchments 2 and 3 for what I ended up with. I'm very pleased with the sound and new appearance of the speakers, it was a long but very interesting journey to this point, with some quite radical design choices. There are things I'd do different now but that's probably the case with just about any project.
If anyone is interested, i can post some (a lot) more details.
K.
Attachments
Hi, thanks. I measured the T/S parameters of the woofers, then did a simulation on WinISD as usual. There is nothing to take into acount regarding port positioning in a cabinet of this size, except for maybe mid-range leaking through them, which proved to be non-issue anyway.
The plastic thingies were just loosely glued in there, I used a small hammer to take them out. Then I glued some wood in the holes and evened it out with filler (IIRC it was automotive 2 part filler).
Your decision on converting these to closed cabinets is OK, the box is much too small for the ports to do anything useful really (the passive version could use different drivers though, measure them to be sure). I ended up plugging ports with foam too, because I use an active crossover and a very potent subwoofer with them.
The plastic thingies were just loosely glued in there, I used a small hammer to take them out. Then I glued some wood in the holes and evened it out with filler (IIRC it was automotive 2 part filler).
Your decision on converting these to closed cabinets is OK, the box is much too small for the ports to do anything useful really (the passive version could use different drivers though, measure them to be sure). I ended up plugging ports with foam too, because I use an active crossover and a very potent subwoofer with them.
P8A PCB board no sound after surge: replacing xover and ampli...
Hi, I was looking around for some way of replacing the internal board of my Phonic P8A with active/passive x-over and external ampli to retain the speaker.
My PCB is dead after power surge: power comes in, leds turn on, and I checked circuitry and voltages all the way to stabilize power ICs, yet no sound at all.
I read your article and I was thinking of maybe converting this to a passive monitor using an external ampli + passive crossover (I welcome suggestions) or use an active x-over with 2 ampli, one per way.
How did you do it? Any suggestions?
Hi, I was looking around for some way of replacing the internal board of my Phonic P8A with active/passive x-over and external ampli to retain the speaker.
My PCB is dead after power surge: power comes in, leds turn on, and I checked circuitry and voltages all the way to stabilize power ICs, yet no sound at all.
I read your article and I was thinking of maybe converting this to a passive monitor using an external ampli + passive crossover (I welcome suggestions) or use an active x-over with 2 ampli, one per way.
How did you do it? Any suggestions?
Just posting some stuff for archival purposes if anyone is interested.
The waveguide added several dB boost to the 27TFF in higher mids, improved directivity and and decreased distortion (good). To make it match the woofer I added a 10uF caps in series with tweeters, which corrected the boost nicely and also allowed for lower order high-pass on them to perfectly match woofer in LR4 arrangement, phase and time-wise.
I changed all the signal caps and probably some if not all 4580 opamps to NE5532:
Also attached the schematic for anyone wanting to tinker with it
What I did right:
Waveguide loading is probably a must for 8" matching with 1" tweeter
The speakers play nice at low to moderate levels, which was their primary purpose (near field monitors).
Now the bad part:
Either I got the xover wrong or the tweeter didn't like my waveguide but I get load of 3rd order distortion in 1-2kHz range, which makes the speakers sound very muddy at any reasonably loud level. Fine for HT or party mode though.
I don't like the woofers - very soft cone and poor low frequency extension, no matter the tuning. I ended up leaving some of the low-boost circuitry active to compensate for that.
This tweeter doesn't like this waveguide in that above 10kHz is beamed in an indredibly narrow angle. I got around that by EQing it a bit and listening at 15 degree angle or so.
TS parameters for the woofer (measured):
The waveguide added several dB boost to the 27TFF in higher mids, improved directivity and and decreased distortion (good). To make it match the woofer I added a 10uF caps in series with tweeters, which corrected the boost nicely and also allowed for lower order high-pass on them to perfectly match woofer in LR4 arrangement, phase and time-wise.
I changed all the signal caps and probably some if not all 4580 opamps to NE5532:
Also attached the schematic for anyone wanting to tinker with it
What I did right:
Waveguide loading is probably a must for 8" matching with 1" tweeter
The speakers play nice at low to moderate levels, which was their primary purpose (near field monitors).
Now the bad part:
Either I got the xover wrong or the tweeter didn't like my waveguide but I get load of 3rd order distortion in 1-2kHz range, which makes the speakers sound very muddy at any reasonably loud level. Fine for HT or party mode though.
I don't like the woofers - very soft cone and poor low frequency extension, no matter the tuning. I ended up leaving some of the low-boost circuitry active to compensate for that.
This tweeter doesn't like this waveguide in that above 10kHz is beamed in an indredibly narrow angle. I got around that by EQing it a bit and listening at 15 degree angle or so.
TS parameters for the woofer (measured):
Code:
fs 46,7 Hz
Qms 1,694
Qes 0,360
Qts 0,297
Fts 157,4
Mms 33,67 g
Cms 0,345 mm/N
Rms 5,830 kg/s
Vas 19,79 litres
Bl 9,521 Tm
Eta 0,55 %
Lp (1W/1m) 89,54 dB
Dd 16,00 cm
Sd 201,1 cm^2
Added mass 3,85 g
Air temperature 20,0 C
Air pressure 1013,25 mB
Air density 1,2041 kg/m^3
Speed of sound 343,2 m/sAttachments
Last edited:
Hey Wxn,
I’m TEN years later but hey. Let’s try.
For ten years I didn’t make any music. And now I’m starting again. I want to build up my studio again. So two questions. I own a pair of P8’s
1. but I blew up one of the tweeters (yes, that’s stupid..).
how hard is it to replace the tweeters? And if I’m right. You only replaced te small center of it right? Not the entire square thing
and 2. If I don’t replace the holes at the front. Is it still a good intervention to add the rockwool? And what is the effect of that?
greetings from The Netherlands.
Beo
I’m TEN years later but hey. Let’s try.
For ten years I didn’t make any music. And now I’m starting again. I want to build up my studio again. So two questions. I own a pair of P8’s
1. but I blew up one of the tweeters (yes, that’s stupid..).
how hard is it to replace the tweeters? And if I’m right. You only replaced te small center of it right? Not the entire square thing
and 2. If I don’t replace the holes at the front. Is it still a good intervention to add the rockwool? And what is the effect of that?
greetings from The Netherlands.
Beo
Hi everyone I'm Alfonso.
I need help, my P8A monitor smoked yesterday.
I can't explain how it could have happened: after 2 hours of use the speaker was in on but without audio input (it was only powered). I opened the back and from what I see is that the power cord is loose at one point.
The cable touched the TDA7293's heat sink, (the heat from the heat sink melted the cable and created a short circuit).
Design error or assembler's error.
I have dealt with power amplifiers but never had such a bad situation.
I hope I can fix the circuit.
Do you have any advice? I saw that you have posted the circuit diagram and this helps me a lot (even the amount of damage).
I am attaching a photo of the damage. the two TDA 7293 of the woofer are cooked.
I await your precious advice.
Thank you very much.
I need help, my P8A monitor smoked yesterday.
I can't explain how it could have happened: after 2 hours of use the speaker was in on but without audio input (it was only powered). I opened the back and from what I see is that the power cord is loose at one point.
The cable touched the TDA7293's heat sink, (the heat from the heat sink melted the cable and created a short circuit).
Design error or assembler's error.
I have dealt with power amplifiers but never had such a bad situation.
I hope I can fix the circuit.
Do you have any advice? I saw that you have posted the circuit diagram and this helps me a lot (even the amount of damage).
I am attaching a photo of the damage. the two TDA 7293 of the woofer are cooked.
I await your precious advice.
Thank you very much.
