Celstion 66 & 55 crossovers - question

[lorienblack]

I have a pair of celestion ditton 55's and a pair of 66 bass units as well as a pair of bass reflex units. So naturally I am wanting to build a pair of 66's. My question is -

Are the crossovers from the 55's and 66's the same? And could I re-cap the crossovers from the 55's and use them to re-create the 66's. I believe the both operate at the same crossover frequencies.

Any advice would be most welcome.

[osvaldo]

Hi,post a photo crossover 55 ( ditton 55 never see this model make photo of this and photo midrange and tweeter )face component and face printed circuit board for make schematic diagram and comparate with crossover 66 regards Osvaldo sorry for my little english osvaldo.figini@alice.it

[lorienblack]

many thanks dude - that helps a lot

[alan-1-b]

Hello Lorien,

are you sure you have Celestion Ditton 55 ?
I have never seen a 55, nor can I find any information about one ever existing.

Look carefully at what you have - is it a Celestion {Ditton} 551 ?
That model had a 10" woofer, and a ported -{bass reflex}- enclosure.


There was also 442 and 662.
Both had 12" woofers, BUT they are a higher Impedance 12" woofer than the woofer used in 44 and 66.

What is the T**** number printed on the back of the 2 woofers you have ?
{there will be a T followed by four digits.}

Am I misunderstanding what you mean by:- "bass units" and "bass reflex units" ?
Are these Woofers or Cabinets ?

442, 551, 662 crossovers are not the same as the crossover used in 44 and 66.

[lorienblack]

Hi Alan, here (I hope) is a pdf of the 662 schematic and below a link to some photographs. The caps with the asterixs are the green ones, the 2.5 being two in parallel. The 40uf is three in parallel the 102uf is two in parallel and the 28.7 is two in parallel, this may be of little importance?

2 X Celestion Ditton 662 3-Way Crossovers on eBay (end time 28-Jan-10 17:06:51 GMT)

I have opted to remake the crossovers point to point because I think I would need watchmakers hands to compose it all on the existing board, plus experiment with resistors.

Thank you again - LB/Hamilton

[lorienblack]

Try again with the schematic.

[event horizon]

You might have been thinking of the Ditton 25 which is similar to the 66 in that it uses a 12" bass unit & a 12" ABR. They might be the same drivers & ABR, i don't know.

I have a pair of 66s in another room, unfortunately the original HF2000 tweeters were toast when i bought them (dead cheap) so i replaced them with some Goodmans 1" domes from the Magnum

They sound really good, which is surprising considering how cr*ppy the cabinet build is compared to more modern speakers

[lorienblack]

No - the cabinets are the 551's the bass drivers are chopped in from 44's, the crossovers have been pinched from a pair of 662's.

On the whole they sound great, the bass is awesome, the mids a little absent and the highs a wee bit harsh. Im attempting to resolve the last issues by re-vamping the crossover with poltprops and switching from a circuit board to point2point. I'm in deeper than I was expecting, nobody warned me that crossover design was dark arts with more variables than an octopus could juggle.

One thing for certain - if you own some 551's buy some bass units from the 44''s or 66's and swap them for the 10inch driver. You will not look back, you will bin the old ones. Oh and I have 2 spare sets of 44 bass drivers up for grabs

[alan-1-b]

There are SEAS 10" drivers available which can be used in Celestion 551 if the original drivers have deteriorated, or if one wants to improve on the performance of the original woofer.
I will post about this if anyone is interested.
I think an old 12" Celestion driver is not necessarily the optimum choice,
nor good value if its price is high to buy, and depending on its condition it may not last as long as a new SEAS 10".

But of course if one likes the sound of the old 12" Celestion woofer in the 551 loudspeaker, then that is fine.

Lorien, is the internal volume of the 551 the same, or close to the same,
as the internal volume of your Celestion 44 ?

[alan-1-b]

Originally Posted by lorienblack

Try again with the schematic.

Lorien, this circuit is not correct, at least not in part.

The components along the top line form a band-pass filter, thus will be for a mid-range driver and not for a tweeter.

The components along the middle line form a high-pass filter, thus will be for a tweeter and not for a mid-range driver.

The components along the bottom line form a low-pass filter, thus are for a woofer.

The + and - connections for the drivers are not labelled at the outputs.
I think at least one of the outputs will have its -ive connected to its components' line and its +ive connected to ground, and perhaps two of them will.


Looking at the photos on the ebay page I cannot read the values printed on some of the capacitors, though I can guess some of them, but not the black one labelled C11 under the 24MFD black capacitor on the Left-side - what is printed on it ?

Also, what is the value printed on the resistor ?

Look closely beside each inductor and you will see L numbers.
I can see only L3 in the photo.

What I need to know is:-
what is the L number for the other inductor which is the same size as L3 ?
what are the L numbers for the two smallest inductors ?
what is the L number for the largest inductor ?

Why I ask all this is that I am a bit surprised by this crossover.
Are you sure that you have followed all the circuit paths correctly ?

L3 with 4.7uF in complete local parallel with it is possible, but do check.

L1 and 28.7uF form a lower order filter than I would expect, but it is possible that works correctly for the later model Celestion woofers, though the crossover frequency will be much higher than I would have expected.
Are you sure that the combined capacitors there and L1 are the only components in that line ?

If the middle line of your drawing is correct for the tweeter, its crossover is higher in frequency than for the older 44 and 66 Celestions.

If the top line is correct for the mids' filter, its crossover from the bass is at a higher frequency than I would have expected.

If all the components are connected in the way you have shown in the diagram, then I fully expect "the mids a little absent" - as you wrote - when this network is used with the older Celestion 12" woofer in comparison to "bass is awesome" - as you wrote.

To get the mids to balance better with the bass when using the 44 woofer you will likely have to increase the capacitance to more than 28.7uF.
Are you sure there is only one inductor in this section of the filter ?
I would have expected there to be two.

Ideally, we need to know the mH value of each inductor to adapt this crossover to the 44 woofers.

"the highs a wee bit harsh" - this can be reduced with suitable modern capacitors and a small value series connected resistor.

I hope you don't have 662 crossover connected in your 551 in the way you have shown the connections in the diagram.
If you do then harsh highs and absent mids is exactly what you will be hearing ! ... and the tweeter will be damaged if you play the speakers loudly.

Compare the 662 crossover with your 551 crossover.
Is the number of components exactly the same ?
Are the capacitors all the same values ?
Are the combinations and connections all exactly the same ?

Smaller size, metal cored inductors in 551 crossover does not mean different inductances, but I would expect a different inductance value for the bass filter of 662 to the one for 551, and a different combined capacitance there, both because of the different size woofers used.

Check everything in both 551 and 662 crossovers, and Post new diagrams for any differences.

Mark the +ive and -ive connections from the drivers on the outputs of the crossover diagram - this is relevant to the sound.