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Old 24th August 2010, 06:53 AM   #521
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Quote:
Originally Posted by sba View Post
I think that the cap values remained the same throughout the production run, except for a few speakers with early serial numbers that used a 30uf (instead of 24uf cap) in the bandpass. When replacing, use a 24uf cap !

Attachment 184492
Actually, I've seen 2 early pairs of 44s that had a 24uF paralleled with an 6uF, making 30uF. I replaced mine with 30uF, as there may have been a reason for that choice in the early speakers, like the cones changing for example. Anyway, one is free to try either way I guess.

Also, on the issue of tweeter replacement, I have to question your preference for 25mm over 19mm tweeters for this application. 19mm will give better dispersion than 25mm, hence soundstaging, higher top end than the 25mm, and lower capability than the HF2000 making for more comfortable crossover point in the 66s than was possible in the day. What advantages do you see with a 25mm tweeter?
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Old 24th August 2010, 04:49 PM   #522
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Quote:
Originally Posted by LucasAdamson View Post

Also, on the issue of tweeter replacement, I have to question your preference for 25mm over 19mm tweeters for this application. 19mm will give better dispersion than 25mm, hence soundstaging, higher top end than the 25mm, and lower capability than the HF2000 making for more comfortable crossover point in the 66s than was possible in the day. What advantages do you see with a 25mm tweeter?

Itís just a preferenceÖ I like having adjustable extra output in the tweeter in case a particular room or program needs it. The larger domes generally have less excursion for a given SPL, thus lower distortion. The two that I listed are likely to have smooth FR right out of the box, and not be in need of much crossover modificationÖ an Lpad might be enough.

The top end, above 15khz, is not important to me. I know itís there in my 66Ďs, because the mic picked it up in my measurements, but I really canít hear it, unless I play test tones and increase the volume far above normal listening levels. Playing test tones (from a CD) is a good way to judge the importance of frequencies for yourself. I find that the important treble energy is down below 12khz.

I havenít seen too many published off-axis plots of dome tweeters. The few that Iíve seen show similar dispersion, and none were spectacular.

********

Interactive Frequency Chart - Independent Recording Network
.
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Old 28th August 2010, 06:54 PM   #523
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Default interim Post on alternate tweeters

Hello to everyone who has posted since I was last here.

Unfortunately I have had very little spare time recently, and not much now either, so I will start on the backlog of things to reply to,
but only a short reply to one today.

I hope to return to others before too long.

Quote:
Originally Posted by WayneSwann View Post

The MOREL CAT 298 is part of their new 'Classical Advanced (CA)' range of dome treble and mid-range units. Their spec as described in the Wilmslow Audio catalogue is as follows:-
Dia 104 mm (although they modified mine with a 94 mm faceplate so it would fit my Studios 66's).
Spl-89dB Imp-8ohm
Norm Power -80W Fs 900Hz
Freq range - 1.8 - 20kHz
£38 each.


I did a search for the Coles CE 4001 'Super-Tweeters' you mentioned. I could only find any information on the COLES own website. I have sent them an email regarding their cost and also the fact that they mention that they can alter the impedance of the speakers if required. I have never heard of this option before, so I awaiting their reply to find out what they mean exactly.

Cheers
Wayne
Wayne,

I have found and studied the Morel CAT 298 data.
It can be adapted to work in the Celestion 66, but will need some changes to the treble filter of the crossover because it has a different Impedance characteristic and a different frequency roll-off than the HF2000.
The changes will be similar to what I started describing to "damaltor" about his Hiquphon OWI tweeters, but as the Morel is spec'd about +2dB greater sensitivity than the OWI it will require different value resistors for its L-pad.

I recommend you read my Posts #443 and #445 on Page 45 -
- the relevant parts of those for you will be obvious -{I hope}.

The CAT 298 can be got to sound better integrated into the 66 with the mids than it is currently, however it will never sound like one of those old Realistic tweeters, but we may be able to get a little more of the character you want from the treble than you are currently getting.

In the above #443 you will read why I do not recommend higher sensitivity tweeters.
The Audax TWO34XO and Ciare MT 320 will NOT give their best performance with the lower sensitivity Celestion mid-domes,
{though both those tweeters would be very suitable for higher sensitivity loudspeakers, or for loudspeakers being driven to very high volume levels}.

sba's JBL tweeters, though higher Sensitivity than HF2000, do NOT sound like modern Dome tweeters, but have a unique sound of their own
-{albeit similar to a few of the other old cone-type tweeters}.
If anyone wants the "sba sound" they will have to obtain JBL 25 or 26 model tweeters !
What sba is doing is fine-tuning his 66s to give a pleasing sound with those JBL tweeters ... and I have no doubt that such can be achieved ...
{and I intend to return to this point sba - I think the JBL tweeters may work better with the older MF domes than with the MD domes, given your measurements to date}.

Using an adjustable L-pad, such as the one sba posted a Link to will allow you to decide relative volume level, but it will not be optimum in the crossover if the Celestion capacitors values are used ... as I explained in those earlier posts about resistors and impedance, because an L-pad is similar to 2 resistors.

Wayne,
if you have decided to continue with CAT 298, please Post and confirm that,
and then I will calculate some suitable cap and resistor values for the treble filter,
but if you've decided a different tweeter, please Post whatever here.

Also,
did Coles reply to your email ?
If so, what did they say ?

*********************

Wayne, and "tojohndillonesq"/SW if you are still proceeding :-

please look at the Photos earlier in this thread of the different types of crossover boards and Post which type is in your 66s,
so that I know what parts I have to refer to,
and so that I can advise a bit on placement of the larger new components.

*********************

sba,
the Interactive Frequency Chart is useful, and it is good that you have posted it here for members to refer to,
however there is more to hearing high frequency harmonics of instruments in optimum balance with their fundamentals than can be deduced from the chart alone.

I accept what you have discovered about your own hearing,
and likely the JBL tweeters' highest frequency extension characteristics match the treble characterisics of the particular types of recordings you like ...
but some other types of recordings are different, as are other types of tweeters despite similar measured high frequency extension.
I will post more about this when it becomes relevant to modifications to the 66 crossover to accomodate other tweeters.

Also, bass drums and tympani can be tuned to lower fundamental frequencies than the 50 Hz shown on that chart,
but rarely are lower frequencies left in for Popular Music recordings, however they are for some Classical Music recordings.
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Last edited by alan-1-b; 28th August 2010 at 07:11 PM. Reason: to better space some paragraphs
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Old 28th August 2010, 08:47 PM   #524
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Default New changes to my Celestion 66's

Hi Alan,

Thanks for all of your comments. Because I wasn't totally happy with the sound of the Morels I have sent them back to Wilmslow Audio. To be quite honest I did like the 'highs' reached by the Radio Shack (Realistic) Super Tweeters that were installed when I first obtained the 66's as I said before. I have done a little research on them , the model number is 40-1310B. I found the original operating instructions for them. They were supplied with a small crossover circuit to provide 12dB/octave attenuation below 5kHz. This could be mounted outside the required speaker or be used as a Super Tweeter and mounted inside the speaker enclosure. The crossover consisted of a 2.2uF capacitor and a 0.27 inductor coil. What they didn't come supplied with was an L-pad to adjust their output due to their high sensitivity, although it is referred to in the operating instruction . I guess the previous owners of the 66's replaced the original HF2000 tweeters with them but discarded the crossover network and did not install an L-pad.
I had another look through The Wilmslow Audio catalogue and found the Vifa XT19TD00-04 tweeters listed. These tweeters have an impedance of 4Ohms and their frequency range that extends to 30kHz. I thought they would make a better fit and reach the higher frequencies that seemed to be missing from the Morels.
I also thought I might add the Realistic Super Tweeters mounting them in their own enclosure with the necessary crossover and L-pad. According to their instructions they are to be connected to the speaker's binding Posts along with the existing speaker cable. My thinking behind this is to recreate the benefit of the 'nice' highs they previously reached without overpowering the overall sound making it too bright. The L-pad would allow me to do so, I think! I must admit this is all rather new to me and I certainly don't want to damage my 66's, but this is one of ways they were intended to be used!
I have some photos of the crossover circuits currently installed in my 66's. They seem to be the same as the one's previously posted except that the the bottom capacitor is split into 2 parallel capacitors of 6uf and 24uf (C4 & C5). I will try to post the photo into this thread but I'm not exactly sure how to do it. I have managed to attach itCrossover like mine serial no 013259 2nd generation.jpg I think.

I hope this all makes some sense to you. I would especially like to hear from you about my new choice of the Vifa tweeters and the possible use of the additional Realistic Super Tweeter in their own enclosures as I previously described. Of course I want to make sure I don't do any harm to 66's

Best Regards

Wayne
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Old 29th August 2010, 06:05 AM   #525
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Default Technical Details of Vifa Tweeter and Realistic Super Tweeter

Hi once again Alan,

Here is some more information regarding these Realistic Super Tweeters :-

User Guide.pdf

Here is the Techmical Spec for the new Vifa twteers I am now intending to install into my 66's:-


Vifa XT19TD-00-04
19mm Dual Concentric Treble
Dia-94mm
Spl-89dB
Imp-4ohm
Fs-682Hz
Freq Range 1 - 10kHz

Wayne
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Old 29th August 2010, 06:49 AM   #526
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Default Additional information

Hi once again Alan,

Here is some more information regarding these Realistic Super Tweeters :-

User Guide.pdf

Here is the Technical Spec for the new Vifa tweeters I am now intending to install into my 66's:-


Vifa XT19TD-00-04
19mm Dual Concentric Treble
Dia-94mm
Spl-89dB
Imp-4ohm
Fs-682Hz
Freq Range 1 - 10kHz

The photo of the other version of the 66's crossover schematic for my 66's crossover:-

Crossover different single C5 Cap serial 27343.jpg

Notice that the bottom Capacitor is a single one. Whereas on mine this has beeen split between two. A 6uf & 24uf Capacitors (C4&C5)

Here is a list of 66's componants-

66 Xover with component numbers.jpg

I still want to restore the crossovers on my 66's, replacing the capacitors and coils if necessary but I'm still clear on certain things! Why have they used capacitors in prallell i.e. C4 & C5; C6,C7 & C8; C9,c10,C11 & C12?
Also I have not been able to find exact matches for C1 & C2 @72uf! what happens if I cant find an exact match.
Could you let me have a list of replacement Capacitors & any resisters required to bring them bang up to date using good quality components

The Schematc:-

crossover schematic.jpg

Wayne
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Old 29th August 2010, 09:54 PM   #527
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Default Error in previous thread

Hi,
of course when I mentioned the frequency range for the Vifa tweeters I intend to use now is 1 - 30kHz.

Cheers

Wayne
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Old 31st August 2010, 05:07 PM   #528
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Default Tweeters:- Vifa XT19TD is no better than Morel CAT 298

Quote:
Originally Posted by WayneSwann View Post


I had another look through The Wilmslow Audio catalogue and found the Vifa XT19TD00-04 tweeters listed. These tweeters have an impedance of 4Ohms and their frequency range that extends to 30kHz. I thought they would make a better fit and reach the higher frequencies that seemed to be missing from the Morels.


I hope this all makes some sense to you. I would especially like to hear from you about my new choice of the Vifa tweeters and the possible use of the additional Realistic Super Tweeter in their own enclosures as I previously described.

Best Regards

Wayne
Sorry Wayne,

but after seeing the Data sheets for both the Morel CAT 298 and the Vifa XT19TD00-04, the Vifa will be no better in actual audible treble extension than the Morel, because BOTH tweeters have rolled off treble above about 8kHz.

Neither will sound identical -{because of other differences in their relative designs}- but both will sound "civilised" -{to use your word}-
and not produce Hi-Hat sounds like the Realistic tweeters.

(Note: you did not actually hear the Morel's true potential, because the 66 crossover was not changed to work with the higher Impedance Morel.
The Morel will sound a bit different, and better, with a suitably modified cross-over.)

Yes, the Vifa is Specified to 30kHz, but it is -3dB there,
and I doubt you will hear above 16kHz, and note the Vifa is -2dB there.

The Vifa has a prominence in the 6k - 7.5kHz region, and that will audibly dominate,
because human hearing is more sensitive there than above 8kHz.
The 16kHz output is -3dB relative to the 6k - 7k5 prominence of +1dB.
It would be good to get Flat to at least 16kHz for Hi-Hat, Cymbals, Violin harmonics, etc ...

Note also how rapidly the Vifa's treble response rolls off at 30 degrees off-axis.

These Vifa XT, and DX, series tweeters have disappointed a lot of diyers,
because despite their specification they do not give true audible high treble extension nor good dispersion.
They are designed for a specific purpose which has to be understood when choosing to use them.

SEAS H737-08/19TFF1 is as close to a Flat Response as one can reasonably expect in this price region.
It will give a bit better audible high frequency extension for Hi-Hat, etc ... than the Vifa and the Morel.
It will not sound like the Realistic.
If you want the Realistic sound we will have to design around its specification,
or, look for a dome tweeter that has a frequency response that rises in level above 10kHz.
Look at some in the "Scanspeak" range.
Yes, they are more expensive ... and given how it seems you are not clear with understanding Tweeter data,
Post whatever model numbers you may be considering BEFORE you buy, and I will look at their full data ... if it is available.

I recommend you cancel the Vifa order, and either order the SEAS or hold Credit with Wilmslow till you can decide more knowlegeably about other tweeters.

Do not worry about Specified Impedance for replacement tweeters,
because as long as the Sensitivity is greater than the HF2000, the Impedance of the replacement tweeter can be accomodated for in the cross-over
-{but within reason, eg: a 6 ohm or 8 ohm tweeter will be better suited than a 15 ohm or 16 ohm model}.
Consider more-so the Sensitivity - for the reason I gave in the Posts I refered you to.
An 87dB dome tweeter -{or similar Sensitivity}- can be got to work better for the treble sound you seem to want than a higher sensitivity tweeter.
Look instead for Flat treble or rising treble above 10kHz.

***************

Do you have a Multimeter ?
If so, measure the DC resistance of both your Realistic tweeters and Post the figures here.

***************

Did Coles reply to your email ?

***************

I have to go now as I have run out of time.
I'll Post more next time, but do Post the Realistics' resistances so that I can estimate what maybe can be done ...
but they will not be easy to integrate with the mid-domes at 5kHz ... more about that next time.

***************

Do you have MF500, or MD500, mid-domes in your Celestions ?
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Last edited by alan-1-b; 31st August 2010 at 05:17 PM. Reason: to better space the paragraphs
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Old 31st August 2010, 09:43 PM   #529
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Default Changes to my Studio 66 upgrade!

Alan,

I seem to have jumped the gun regarding the Vifa tweeters. I will cancel the order with Wilmslow Audio and ask them to wait until I decide exactly which tweeters I am going to decide upon. They do seem to stock the Seas H737-08/19TFF1 so I could do a straight swap. I don't mind spending more money in order to reach a satisfactory conclusion to all these efforts. Including your very welcome advice. I have looked at the Scanspeak tweeter range, I am rather limited due to the flange size of the 66's. I have found the D2010/8513. The basic technical summary is as follows:-

19mm Fabric Dome Tweeter
Spl-90dB
Impedance-8ohms
Nom Power 150w
Fs-800Hz
Freq range 4-20kHz

I have sent Coles another e-mail regarding the 4001 Super Tweeter, do you think that would be a better overall choice?

I may have 'jumped the gun' again but I have ordered the capacitors and inductors (2.2uF & 0.27.mH) for their crossovers as specified in the Realistic Super Tweeter instruction manual (I attached this in my previous post), along with a couple of L-pads to allow for their high sensitivity of 95dB..

As I previously mentioned I intend mounting them in their own enclosures and use them as originally intended. I have got some enclosure I intend to use for this purpose. As I have never used Super Tweeters before I was a little concerned about the load presented to my amplifier when connecting them in parallel to the 66's binding posts but I was reassured that it would not be a problem, bearing in mind that all external Super Tweeters are connected this way.
I don't have any testing equipment that's sensitive enough to measure the DC resistance of the Realistic tweeters. I wasn't sure why you needed this reading though?

Last edited by WayneSwann; 31st August 2010 at 09:46 PM. Reason: To add some extra remarks
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Old 1st September 2010, 11:47 AM   #530
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Default Regarding the Scanspeak D2010/851300

Hi Alan,

I would be gratefull if you could look at the response curve of this Scanspeak D2010/851300 Tweeter. I have spoken to Wilmslow Audio and cancelled the order for the Vifa tweeter. They seem to be getting a little upset with my ditthering, still I'm the customer who's paying them!
If you don't think it matches the kind of response we are looking for I'll go ahead and purchase the Seas H737-08/19TFF1.
I will still go ahead and build these seperate Super Tweeters using the Realistics I have with their specified crossovers in their own enclosures.
Cheers
Wayne
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