Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Phonic P8A reloaded
Phonic P8A reloaded
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th July 2012, 09:39 AM   #1
wxn is offline wxn  Lithuania
diyAudio Member
 
wxn's Avatar
 
Join Date: Sep 2003
Location: Vilnius
Default Phonic P8A reloaded

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:
  • 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/z...g?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:
  1. Relocated the ports to the sides of the cabinet, changing them to 4cm PVC tubing in the process (WinISD helped a lot)
  2. Completely refinished the cabinets
  3. Laid about 1" of rockwool on inside walls
  4. Changed the tweeters to Seas 27TFF
  5. 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.
Attached Images
File Type: jpg p8a native xover.jpg (86.3 KB, 231 views)
File Type: jpg p8a finished spl.jpg (75.0 KB, 213 views)
File Type: jpg IMG_2378.jpg (261.4 KB, 215 views)
__________________
Nothing is as simple as it seems
  Reply With Quote
Old 11th July 2012, 01:10 AM   #2
Inductor is offline Inductor  Portugal
diyAudio Member
 
Inductor's Avatar
 
Join Date: Feb 2006
Location: Cascais
They look nice now. Good job ("from beast to best" diy, I would say).
  Reply With Quote
Old 11th July 2012, 06:26 AM   #3
wxn is offline wxn  Lithuania
diyAudio Member
 
wxn's Avatar
 
Join Date: Sep 2003
Location: Vilnius
Quote:
Originally Posted by Inductor View Post
They look nice now. Good job ("from beast to best" diy, I would say).
Thanks!
__________________
Nothing is as simple as it seems
  Reply With Quote
Old 12th October 2013, 09:17 AM   #4
Pruimenvlaai is offline Pruimenvlaai  Netherlands
diyAudio Member
 
Join Date: May 2009
Very interesting! Could you explain how WinISD helped with the port? WinISD doesn't take into account the position of the port, right? And how exactly did you block the ports in front? I'm looking to convert my P8 passive to a sealed speaker, but can't seem to remove the plastic thingies.
  Reply With Quote
Old 12th October 2013, 01:25 PM   #5
wxn is offline wxn  Lithuania
diyAudio Member
 
wxn's Avatar
 
Join Date: Sep 2003
Location: Vilnius
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.
__________________
Nothing is as simple as it seems
  Reply With Quote
Old 11th October 2015, 01:11 PM   #6
ccyrano is offline ccyrano
diyAudio Member
 
Join Date: Oct 2015
Default 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?
  Reply With Quote
Old 17th September 2018, 10:36 AM   #7
wxn is offline wxn  Lithuania
diyAudio Member
 
wxn's Avatar
 
Join Date: Sep 2003
Location: Vilnius
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:

P8A-plate-001.jpg

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/s
Attached Images
File Type: jpg P8A_1.jpg (233.1 KB, 31 views)
__________________
Nothing is as simple as it seems

Last edited by wxn; 17th September 2018 at 10:44 AM.
  Reply With Quote
Old 17th September 2018, 05:10 PM   #8
wxn is offline wxn  Lithuania
diyAudio Member
 
wxn's Avatar
 
Join Date: Sep 2003
Location: Vilnius
Additionally woofer and tweeter responses
Attached Images
File Type: jpg juostos.jpg (63.7 KB, 22 views)
__________________
Nothing is as simple as it seems
  Reply With Quote

Reply


Phonic P8A reloadedHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Phonic P8A schematic wxn Solid State 3 23rd January 2013 11:05 PM
ZD5 Reloaded. zdr Multi-Way 23 1st February 2011 08:04 AM
Thiele-Small reloaded with LTspiceIV steph_tsf Multi-Way 12 9th May 2010 09:59 AM
Bryston 3B-SST Reloaded Sanken Solid State 5 21st August 2004 03:16 PM
Name these soundtracks (Matrix Reloaded and F&F) VEC7OR Music 5 19th July 2003 03:32 AM


New To Site? Need Help?

All times are GMT. The time now is 01:13 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki