Celestion CDX1-1425 deviations

Salas

diyAudio Chief Moderator
Paid Member
2002-10-08 11:31 am
Athens-Greece
Hello all

Does anybody have experience on what kind of frequency response tolerances I must expect from these drivers?

I bought them directly from a reputable UK stockist. They look unused indeed but maybe they had a rough trip, the (+) terminals were beaten a bit on both, I don't know if they received a side blow.

I run impedance curve tests first and one driver's shape looked weird. Their unmounted frequency plots were too different as well. I took them apart and re-assembled them carefully to best close impedance plots I could before mounted on horns (Z plots before & after horn mounted attached).

The orientation of the diaphragm sub-assembly proved very influential to the impedance curves. There is no form of mechanical orientation aid. Only two centering teeth at the rim. The diaphragm chassis can turn like a sports watch bezel to where decided. So I had to look on advertisement photographs for how it should point regarding the frame.

The four self tapping screws that fix the magnet and motor to the plastic cross frame do not inspire confidence on both units. Although they don't allow for visible gaps at the mating, they don't screw to a stop either. Maybe one or two did initially but the plastic threads loosened up easily even when being careful.

Anyway these are the responses I get from them when mounted on FaitalPro STH100 horns. Its just quick close up measuring in very low SPL with no baffle, mouths sitting at the edge of a desk. But indicative enough to check the matching. Any expert comments?

Thanx
 

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Hylle

Member
2005-02-08 2:39 pm
Denmark
I belive your drivers are very fine and matched as well as can be expected. Thank you for showing these measurements, I have been interrested in these drivers for a while. nice output all the way to 20KHz, I dont like the peak at 1KHz though. I expect the two last impedance measurements are with the horn put on the drivers?
Do you have other horns to try them onto?
 

Salas

diyAudio Chief Moderator
Paid Member
2002-10-08 11:31 am
Athens-Greece
I belive your drivers are very fine and matched as well as can be expected. Thank you for showing these measurements, I have been interrested in these drivers for a while. nice output all the way to 20KHz, I dont like the peak at 1KHz though. I expect the two last impedance measurements are with the horn put on the drivers?
Do you have other horns to try them onto?

I hope so because I had to tamper with them. Yes the two last ones are when horn loaded. No other horns around for tests right now. Mainly because only the B&C ME10 would also fit in the narrow tower speaker's baffle and the FaitalPro is the only metallic one I could find that fits, but with a bit of more care in the cutting. But I have non horn mounted close up frequency chart if it tells you anything about the 1kHz thing when raw.
 

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Salas

diyAudio Chief Moderator
Paid Member
2002-10-08 11:31 am
Athens-Greece
I like Celestion CD's. Dollar for dollar, they're the best in business IMO. Your response is as smooth as any CD on the market which would make for an excellent top end down to 1.5khz or so.

I plan to replace the now dome tweeters for mating my PHL1220s with those. So at 2.5kHz but better at 3kHz if able. That Faital short elliptical Tractrix waveguide looks like taking good control just about there. I moved the listening position at 4.4 meters from the face of the speakers and the domes don't cut through the room sound and its HF absorption as good as they could up to 3 meters anymore.
 

Salas

diyAudio Chief Moderator
Paid Member
2002-10-08 11:31 am
Athens-Greece
POOH thanks for the confirmation because I thought I might have tampered wrongly with them. That gradual 0.5dB to 1dB last octave output difference I will have to re-evaluate after the padding down and I can boost the weaker one with a small capacitor across a series resistor if it persists enough.

What is your opinion about I devise some modification for the magnet to frame assembly? Like drilling the chassis brackets for long screws with nuts? Maybe the deep threading in the plastic that loosened does not guarantee enough or alike screws pressure between the units and makes for the last octave output differences?
 

Salas

diyAudio Chief Moderator
Paid Member
2002-10-08 11:31 am
Athens-Greece
The mounts are fine, these are what I call treble drivers and they need some high pass at at least 2k - a series 1 mf cap and a 12 ohm resistor works well in the little Faital horn. Smooth, dynamis and detailed - the 1730 is the same but better lol
The 1730 wins on THD and threshold level of compression below 3kHz I suppose.
 

POOH

Member
2010-10-05 9:06 pm
Ohio
The 1730 wins on THD and threshold level of compression below 3kHz I suppose.

I like it because it does go lower and it has better rendition of tone and organic realistic sound. It needs less contour on the top end too. A really crazy good treble driver. The 1425 is no slouch though - I like to crossover around 3K and the 1425 is a little bit on the metallic shimmer side where the 1730 is very much real - either one in the right set up should be SOTA if you value realism
 

Salas

diyAudio Chief Moderator
Paid Member
2002-10-08 11:31 am
Athens-Greece
I like it because it does go lower and it has better rendition of tone and organic realistic sound. It needs less contour on the top end too. A really crazy good treble driver. The 1425 is no slouch though - I like to crossover around 3K and the 1425 is a little bit on the metallic shimmer side where the 1730 is very much real - either one in the right set up should be SOTA if you value realism
I do have only DIY FET or tubes preamps and power amps which are polite on the highs so no problemo. Thanks for your valuable input as you have hands on experience with the specific CD + horn I just got. :up:
 
Salas would it be posible for you to make a few on/off aksis measurements on your Celestion/Faital combo?
I am also very interested in the HF108. Does anybody know what is the difference on that one compared to HF108R model?
HF108 was tested in voicecoil magazine, I think It had much distortion around 9-10KHz, and that have made me look for other alternatives. Right now I am also considering Celestion CDX1-1730 and B&C DE-250 I like its low resonance frequence.
 

Salas

diyAudio Chief Moderator
Paid Member
2002-10-08 11:31 am
Athens-Greece
Maybe in the next few days I will have the opportunity to make more meaningful measurements of my combo. About the other CDs you ask I don't know much. From B&C I had used DE12, DE16 and DE38 on Eighteen Sound XT120 horns. I much preferred the DE12 cut at 3kHz on that horn when it had to be with a minimal 12dB electrical passive. DE16 & DE38 were wilder to control on a small horn.