modifying tweeters on old celestions

[Fuller]

Hi Guys!

I've been dabbling with audio systems for some time now, but a recent problem has left me in the deep end without a paddle, and I'd appreciate the feedback of a community who may be able to give me some pointers.

This is the problem. I've been generously given a pair of Celestion 300 floorstanding speakers - £800 brand new 15 years ago.
However, the reason I've been given them is that one of the tweeters has completely given up the ghost, the voice coil is damaged and the membrane material over the tweeter itself has split. So, I had an idea. I'll try and find a cheaper pair of celestions on ebay with a similar tweeter to the 300's and swap them over. The nearest I found was a celestion SL6 and a celestion dl4. The SL6 has a far superior tweeter and is very similar to the 300's i have, the dl4 is much cheaper, but the tweeter is probably of less quality, i doubt it is machine drilled metal.

This are my main questions:
Will i ever be able to bring the celestion 300's back upto a decent state by replacing the tweeter?

Will I need to modify the crossovers in the speakers as the tweeters will obviously have different values. And if so - how? (A new thread in itself!!)

Would the pair of SL6's I get off ebay sound better than the modified 300's? The SL6's at the moment are going for £60 - I don't necessarily want to take them apart! But if I get a pair of £800 speakers working again from them I will.

Sorry for the lack of information, but I cant post links on my 1st post - I'll try to rack up a few more and edit this later.

Looking forward to hearing your replies.

 

[TLS Guy]

Hi Guys!

I've been dabbling with audio systems for some time now, but a recent problem has left me in the deep end without a paddle, and I'd appreciate the feedback of a community who may be able to give me some pointers.

This is the problem. I've been generously given a pair of Celestion 300 floorstanding speakers - £800 brand new 15 years ago.
However, the reason I've been given them is that one of the tweeters has completely given up the ghost, the voice coil is damaged and the membrane material over the tweeter itself has split. So, I had an idea. I'll try and find a cheaper pair of celestions on ebay with a similar tweeter to the 300's and swap them over. The nearest I found was a celestion SL6 and a celestion dl4. The SL6 has a far superior tweeter and is very similar to the 300's i have, the dl4 is much cheaper, but the tweeter is probably of less quality, i doubt it is machine drilled metal.

This are my main questions:
Will i ever be able to bring the celestion 300's back upto a decent state by replacing the tweeter?

Will I need to modify the crossovers in the speakers as the tweeters will obviously have different values. And if so - how? (A new thread in itself!!)

Would the pair of SL6's I get off ebay sound better than the modified 300's? The SL6's at the moment are going for £60 - I don't necessarily want to take them apart! But if I get a pair of £800 speakers working again from them I will.

Sorry for the lack of information, but I cant post links on my 1st post - I'll try to rack up a few more and edit this later.

Looking forward to hearing your replies.

This type of question comes up often. Retrofitting speakers, except in the most unusual circumstances is not possible. An exact replacement is required if these speakers are to be resurrected. Do those speakers have plastic or aluminum domes? Celestion had a lot of tweeters in their range back then, and they are all significantly different. Celestion tweeters especially the plastic domes also seem prone to disintegration with age. The metal cone tweeters seem to fare better. You are not the first to be looking for a Celestion tweeter replacement.

 

[Fuller]

Thanks for your reply, I thought that would be the case.

They have metal cones. It looks like a solid lump of aluminium with a cone drilled into the middle of it. Surrounding this cone and inset into the metal block is the voice coil. From my research, the SL6's have a similar machine drilled aluminium cone.

Having done a bit more reading, my other option would be to take the rest of the original speakers apart and sell the parts as spares to others in my predicament! Perhaps put the money towards a new set of bookshelves

Edit: I can add some links now:

Celestion 300 (the most information I've been able to find on them is here: http://www.stereophile.com/standloudspeakers/692cel/ - that link is for the Celestion 100's but as far as i can tell, the tweeters, and cones are identical, the 300's are just taller as they are floorstanding and feel like they have a substantial filling in them as they weigh a tonne!)

Celestion SL6 http://www.audioshopper.com/sl6a.htm

 

[TLS Guy]

Thanks for your reply, I thought that would be the case.

They have metal cones. It looks like a solid lump of aluminium with a cone drilled into the middle of it. Surrounding this cone and inset into the metal block is the voice coil. From my research, the SL6's have a similar machine drilled aluminium cone.

Having done a bit more reading, my other option would be to take the rest of the original speakers apart and sell the parts as spares to others in my predicament! Perhaps put the money towards a new set of bookshelves

Edit: I can add some links now:

Celestion 300 (the most information I've been able to find on them is here: http://www.stereophile.com/standloudspeakers/692cel/ - that link is for the Celestion 100's but as far as i can tell, the tweeters, and cones are identical, the 300's are just taller as they are floorstanding and feel like they have a substantial filling in them as they weigh a tonne!)

Celestion SL6 http://www.audioshopper.com/sl6a.htm

Yes, that speaker has the aluminum dome. The SL 6 and 600 have the copper dome.

Unfortunately those copper domes have a resonance notched out in the crossover. The aluminum dome is the better tweeter. I think the switch to aluminum occurred around 1989. By 1992 Celestion had been bought by an outfit from Honk Kong along with KEF. So unfortunately for you I think you have a narrow window from which to find the part you are looking for.

You might see one come up on eBay if you keep looking.

As a temporary measure you might want to play around with these.

You would have to change both speakers, and quite likely have to change the tweeter L pad values in the crossover. Do you know the sensitivity of your 300s?

 

[Fuller]

From the best information I've been able to dig up (I haven't yet taken a look at the actual crossover) the specifications of my 300's are as follows:

Drive-units: 1.25" (32mm) aluminum-dome tweeter, 6.5" (165mm) polyolefin-cone woofer.
Crossover frequency: 2.2kHz.
Crossover slopes: 3rd-order Butterworth, 18dB/octave, high- and low-pass.
Frequency response: not specified.
Low-frequency extension: –3dB at 65.6Hz, –6dB at 53Hz (both free-space measurements).
Sensitivity: 84dB/W/m (2.83V, free space).
Nominal impedance: 8 ohms.
Amplifier requirements: up to 120W program

The tweeters you linked look like just the ticket! and are about the most I'd want to pay for the experiment too.

When you mentioned about changing the tweeter L pad values in the crossover - I'm arfaid that's where I get a bit lost. I've never modified a crossover before, but I know what a capacitor is and I know how to solder! Is that a good start?

 

[TLS Guy]

From the best information I've been able to dig up (I haven't yet taken a look at the actual crossover) the specifications of my 300's are as follows:

Drive-units: 1.25" (32mm) aluminum-dome tweeter, 6.5" (165mm) polyolefin-cone woofer.
Crossover frequency: 2.2kHz.
Crossover slopes: 3rd-order Butterworth, 18dB/octave, high- and low-pass.
Frequency response: not specified.
Low-frequency extension: –3dB at 65.6Hz, –6dB at 53Hz (both free-space measurements).
Sensitivity: 84dB/W/m (2.83V, free space).
Nominal impedance: 8 ohms.
Amplifier requirements: up to 120W program

The tweeters you linked look like just the ticket! and are about the most I'd want to pay for the experiment too.

When you mentioned about changing the tweeter L pad values in the crossover - I'm arfaid that's where I get a bit lost. I've never modified a crossover before, but I know what a capacitor is and I know how to solder! Is that a good start?

Those are pretty steep slopes, so there is a good chance we will get away with this mod.

The L-pad reduces the power to the tweeter, to match the woofer. That whole Celestion series had very low sensitivity, and yet do not take much power, so they do not play very loud. They are fairly nicely balanced. The worst feature of that whole series was the bass, poor bass extension and the bass a little ponky to boot. However they are good enough to be worth a try at salvage.

Now the L-pad will consist of a resistor in series with the woofer, and a resistor shunting the woofer. You need to examine the crossover and tell me what the values are. Then I can tell if you need to change them, and if so, I will tell you what to change them to.

 

[Fuller]

Here is a picture, I hope this helps

 

[Fuller]

The worst feature of that whole series was the bass, poor bass extension and the bass a little ponky to boot.

Ponky? Do you mean quite flat and negative? I've never heard that term before!

 

[TLS Guy]

Ponky? Do you mean quite flat and negative? I've never heard that term before!

The bass has a slight ponk, ponk quality to it. It is so hard to describe a speaker in words.

l need a photograph of the other side of the board, with input connections, the woofer and tweeter connections marked. If you can please draw the circuit.

The low pass filter is not 18 db third order, but I think the tweeter circuit is. I need more detail of that board, so that you or I can draw the circuit, preferable you, since it in front of you.

 

[Fuller]

I don't currently have a tool that fits the nuts holding the board in place, and seeing as it's right inside the speaker i can't get to them even with pliers. I'll need to ask a friend if i can borrow his set of sockets and I'll get a picture and/or drawing here as soon as possible. Thanks for all your help already TLS Guy!

I might be a few days posting the next part up, dependant on when I get the board out. Have a good Christmas in the mean time!