tuning a 40 years old box made in Belgium.

e3k

Member
2010-09-04 8:08 am
Earth
i have got one box "hifi sound project 2981l" made in Belgium in 70/80ties.

it is tree way and i would like to change the lows cone as it does not meet my expectations. unfortunately the lows cone was already changed so i cant find out the specifications of the original one. i just know it was 8ohms and the hole in the box is 18cm in diameter :confused.

the mid cone is: philips AD 50800 which has the frequency range of 400-5000hz

the crossing had 2 caps 2.2uF and 6.8uF both for 60V.

please let me know what is the highest frequency for the lows cone you think i should choose.
 
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Galu

Member
2018-04-17 6:50 pm
This is likely to be the original, matching Philips 8" driver. AD 50800 M8. It is a full range driver

Here's the data sheet: Breitbander

Mid drivers image attached for good measure! :)
 

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Galu

Member
2018-04-17 6:50 pm
please let me know what is the highest frequency for the lows cone you think i should choose.
The frequency response of most 8" bass drivers will extend up to where it needs to cross over to your mid driver, let's say 1,000Hz as a minimum. If I am correct, the original bass driver extended higher in frequency than that!

However, I would like to be sure of how the crossover is designed and at what frequencies the mid driver and treble driver are crossed over to.

What are the details of the treble driver?
 
The frequency response of most 8" bass drivers will extend up to where it needs to cross over to your mid driver, let's say 1,000Hz as a minimum. If I am correct, the original bass driver extended higher in frequency than that!

the 8” bass drivers were often used in a 2-way. IIRC the generic XO claimed to XO at 500 and either 3.5 or 5kHz. They sucked,

What are the details of the treble driver?

Probably an AD0160/T8:

s-l640.jpg


Pictures of the box & drivers would be useful.

dave
 

Galu

Member
2018-04-17 6:50 pm
View attachment 820283
here a pic of the box. by the way i already ordered this bass speaker as replacement.
Yes, not what I expected either! Since you've already ordered the replacement, I can only suggest you try it and come back if any problems result.

Am I understanding you correctly - you've only got one speaker cabinet, not a pair?

Would still be interested in more photos, particularly of the crossover network.
 

e3k

Member
2010-09-04 8:08 am
Earth
Galu. My first line in this thread quote: "hifi sound project 2981l" so yes it is Hi-Fi Sound Project.

I have only 1. A friend of mine bought similar (a pair) but one was broke so he bought a replacement. But we managed to fix the original one and now i have the replacement from my friend. Since it is meant only for a mono system 1 is enough.

crossover pic. description:

on the top you have + of the low speaker. there is a copper wire connected which leads to the coil (other photo) and then to mids i guess?

on minus a white cable.
a brown cable with 2x1uF capacitors (originally it was one with 2.2uF)

a black cable with 2x3.3uF capacitor (originally it was one with 6.8uF)
 

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Galu

Member
2018-04-17 6:50 pm
Looking at that wiring, perhaps you need to wait for more advice before fitting your replacement bass driver! The manufacturer's original one had a peculiar arrangement. Can you show a photo of how the current replacement is wired - a mistake there may account for why it doesn't meet your expectations. What do you make of it Dave?


EDIT: Got your photos, just saw your edit!
 

Galu

Member
2018-04-17 6:50 pm
Looks like the original bass driver just had an extra set of terminals to hang the capacitors on and I see an extra set of terminals in your photo. Looks like the big cap goes to the mid and the small cap goes to the treble. Can you confirm?

Not a very satisfactory crossover and the cap values don't seem to make sense.
 

e3k

Member
2010-09-04 8:08 am
Earth
Galu you spammer! ;)

1. the wiring looks like a mess because the crossover was mounted on the lows speaker and this was replaced by somebody who did rip it off the speaker.. but as far i can see nothing was changed on it. it just hangs loose. no short circuit visible when i checked it.

2. it looks like your first diagram with just one coil but to be sure i would have unmount the mids and tweeter also and that means 16 screws out and in. maybe i will do it but i guess your diagram is already the correct one.

3. replacing the mids capacitor to 12uF. thank you for that idea. i can give it a shot but i have only electrolytic caps (nichicon golden caps and some nichicon regular ones) at home and not sure if i have exactly 12uF. would have to put some in parallel again to get something close to 12uF.

the replacement bass cone should arrive today so:

1. i will replace it and check how it plays with the current crossover.

2. will try to replace the caps for mids to your suggested ~12uF
 
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Since the current flowing is AC, electrolytics are no good for loudspeakers.
Use BP ( bipolars ) or film caps.
The two coils are usually needed in the two LP points: one for the woofer and one for the midrange, as you'd never want to let the speaker run full bandwidth.
Except the ones that do not "shout" when feeded with treble frequencies > usually this happens at medium-high power