celestion ditton hf2000 replacement tweeter (again) - diyAudio
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Old 12th February 2017, 10:05 PM   #1
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Default celestion ditton hf2000 replacement tweeter (again)

hello all,
ive have just recapped my celestion 66's and had a supposedly good matched spare pair of hf2000 measuring both at 4.5 ohms.
after recapping i thought id bung them in,too my surprise they sounded good but where lacking in hf,they just weren't as loud as the original tweeters.
it turns out they were from a pair of B&O 5700's which use the same hf2000's and mid driver MD500.

I removed those hf2000's and put the original ones back in and everything returned to normal!
the only downside to this is one measures fine,the other measures 9.6 ohms.

id like to replace them with something more modern and it seems from hours reading that the Seas 19TFF is a good drop in replacement.
there are lots of threads on hear with conflicting advice regarding what to change the hf cap values too and they are all very old threads.
i wonder if anyone recently has done this mod and what they used cap wise?

here's a pic of the newly rebuilt crossovers,caps were changed like for like.
Click the image to open in full size.

the B&O hf2000's
Click the image to open in full size.
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Old 13th February 2017, 05:33 AM   #2
system7 is offline system7  United Kingdom
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Hi again, Jamie.

Click the image to open in full size.

I just did some measuring on my old Celestion Ditton 44.

HF2000 is 100mm (4") in a 104mm rebate. Cutout is a mere 62mm, aka 2.5".

Tweeter filter is 4uF/0.14mH/6uF. DCR of the tweeters is 4R and 4.4R.

So a little filing down of the cutout needed for the 87dB soft dome 94mm SEAS 19TFF which has a DCR around 6.2 ohms. But doable. You'll just have to take your chances on any tonal changes. TBH, I'd fit the metal 19TAF/G with a 8.2R/0.68uF Zobel across it.

You could probably make a case for changing the 6uF to 12uF IMO.
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Last edited by system7; 13th February 2017 at 05:35 AM.
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Old 13th February 2017, 06:03 AM   #3
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Some info here - Celestion Ditton 44 - HF 2000 tweeter replacement? - UK Vintage Radio Repair and Restoration Discussion Forum which you might be aware of.

Andy.

Last edited by Dr Wobble; 13th February 2017 at 06:10 AM.
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Old 13th February 2017, 11:06 AM   #4
system7 is offline system7  United Kingdom
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Well, the bottom line from all the agonising in that thread, is that Kat Manton used a 1R/10R attenuator at the SEAS 87dB tweeter. That's about 2dB reduction.

I think the below is a better way to do things. Better impedance, and flatter response.

Probably a 3W for the 1R, and a 7W for the 8.2R. Small Loudspeaker tags available at maplin along with everything else.
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File Type: png Celestion tweeter filter.PNG (3.3 KB, 37 views)
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Old 13th February 2017, 05:07 PM   #5
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if you think that threads bad you wanna try reading the other ditton thread,it makes you eyes bleed! lol.
steve,could you explain in layman's terms what adding the resistors do and also the cap increase please?
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Old 13th February 2017, 07:52 PM   #6
system7 is offline system7  United Kingdom
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The issue here, is that the Celestion filter is for a near DCR= 4 ohms driver. Impedance of a filter tends to be root L/C. Here it's 140uH/4uF=35. Which gives about 6 ohms.

Whatever. If we use a DCR 6.2R tweeter, it's slightly underdamped, which takes impedance low. And makes it a bit peaky. IDK if you'll hear it.

Anyway, 1:3 is your regular 3rd order butterworth filter. It works well, hence my suggestion of 4uF/0.14mH/12uF. But you can keep the 6uF if you want. I like a RC Zobel on a tweeter, particularly with metal ones, because it gives an easy load to the amp and sounds nice.

We then might have to adjust level a couple of dB. Many ways to do that. Below is another way. Whatever you do, nothing is going to blow up. Every ohm in front of a filter takes level down 1dB.

TBH, it seems to me that people have made this far harder than it really is. You can probably fit any tweeter you like. Just adjust the levels. Harbeth use 91dB 104mm SEAS metal domes in this situation. I like them.
H1212-06 27TBFC/G
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File Type: png HF2000 type filter 4 ohms.PNG (2.9 KB, 23 views)
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