3145 components list, board layout?
Ian, I am attempting to build the 4345 (probably mostly inspired by your posts) and wondered if you have posted somewhere the parts list for your system (the crossover components you purchased, your board layout, your actual speaker elements you are using, whether you modified the crossover significantly from the original JBL circuit, if so your schematic) Any direction to the posts would be great. Thanks for taking the time to document and post all this.
Re: 3145 components list, board layout?
Quote:
Originally posted by andresohc
Ian, I am attempting to build the 4345 (probably mostly inspired by your posts) and wondered if you have posted somewhere the parts list for your system (the crossover components you purchased, your board layout, your actual speaker elements you are using, whether you modified the crossover significantly from the original JBL circuit, if so your schematic) Any direction to the posts would be great. Thanks for taking the time to document and post all this.
Okay,
Drivers:
2245H
2122H
2420 with 2425 diaphram
2405 Alnico
Crossover: The schematic is available from the jblpro.com
http://www.jblproservice.com/pdf/Net...%20Network.pdf
chokes
5.4 mh dcr 0.5 ohms
4.8 mh dcr unknown (or as above)
1.8 mh dcr unknown
Notes
JBL used iron core chokes to miniimise losses here but you can use air core which in theory are better but more costly. The 5.4 mh chokes JBL used had a dcr of 0.5 ohms for production reasons, you can shoot for a lower dcr but some retuning of the 2245 ports may be required according to Greg Timbers.
In my crossover the tapped chokes were not used (as they are unavailable to the best of my knowledge) and an alternative consisting of split air core chokes provides equivelant voltage drive. (courtesy of Giskard/GT)
0.68 mh/ 0.32 mh HF section
0.122 / 0.05 mh UHF section
I wound these values by trimming commercial standard values with an LCR meter. I am happy to provide these chokes for a small fee if you are unable to arrange this.
I will post a pdf of the equivelant circuit for the HF and UHF section shorlty. (Note the 0.24 hm choke is not used in the equivelant design)
I had the large chokes made to order, if you live in Australia Voller Transformers are excellent, if you are in the USA try Parts Express , SpeakerCity, Zalytron and others on www and if you are in Europe try Mundorf.
Capacitors.
This has to be the most debated area of DIY Audio. I will avoid any discuss as I am sure you will have fun tweaking the sound to your liking.
90 uf 250 VDC*
60 uf 250 VDC*
20 uf 250 VDC*
14 uf 250 VDC*
8 uf 100 VDC#
3 uf 100 VDC#
12 uf 100 VDC#
1.5uf 100 VDC#
1.0uf 100 DVC#
*I used metalised polypropolyene non polorised capacitors here, sourced from AOEN, bypassed with 0.1 uf film foil AEON.
# These are all Hovlands speaker capacitors.
#I highly recommend pure film and foil varieties in this design. They are expensive but the results show. Try PartsConnexion, Handmade Electronics, Welbourne Labs and the diy speaker supplier mentioned above.
You can of course use metalised polypropolyene or mylar and bypass with small film foils capacitors. JBL did this in the original design. I recommend North Creek Audio as a supplier for this approach.
Resisters
25 ohm 10 watt
5.1/5.1 ohm 10 watt
39/39 ohm 10 watt
62/62/62 ohm 10 watt
20 ohm 20 watt
39/39 ohm 10 watt
I recommend Mills power resisters here, the ceramic resisters and usable but they are very fragile.
The pads are all ( 3 ) x 8 ohm 50 watt, they can be sourced from Parts Express.
The layout I used was done with Tag Stripes and point to point, not on a PCB. I will post this when time permits
Ian