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Old 4th March 2013, 10:41 AM   #941
reggie is offline reggie  Australia
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scan0002.pdf
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Old 4th March 2013, 11:04 AM   #942
reggie is offline reggie  Australia
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Hi Alan,
The east coast of Australia is very very long. I'm located at the extreme south of the east coast. We have had very hot weather here; no fires but no rain either. Our "once in a hundred years flood/fire/cyclone" cycle now appears to be"once every few years".

.I think I have worked out how to post images. The diyAudio support page has details on how to do it. My post (#941) is (if you can access it) my understanding of your prescription for my crossover detailed at your posts #937 and #938. Forgive me if I have confused "in parallel" with "in series". Have I got it wrong??

Reggie
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Old 4th March 2013, 11:50 AM   #943
reggie is offline reggie  Australia
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Old 4th March 2013, 11:51 AM   #944
reggie is offline reggie  Australia
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Re Post #943

Hopefully this is the 1970's review of the Celestion 66 I've being trying to upload for ever.

Reggie
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Old 5th March 2013, 06:28 PM   #945
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Default #941 needs a correction ; #943 displays OK , and a comment about ...

G'day Reggie ,

About your schematic in #941 , the positions of the capacitors in the woofer section need to be reversed:
From the junction point of the 3.5mH and 2.2mH inductors connect the 68uF + 1 ohm and the 8.2uF + 8.2 ohm.
From the other end of the 2.2mH at junction to the woofer (+) connect the 68uF + 1.5 ohm -{ this is the Output of the filter }.


The midrange circuit is correct.
The tweeter circuit is correct , presuming the L-pad options are:
1.2 ohm and 15 ohm
1.1 ohm and 18 ohm

Post the schematic again after redrawing it if you want further confirmation.

About the Review in #943 , at bottom of first column where it is stated:
" a trough in the octave centered on 4kHz "
measurement there depends very much on the vertical axis - that is the height of the microphone with respect to the positions of the mid-dome and tweeter.
When measuring , and listening , on the optimum vertical axis that trough will largely fill in.
You should be able to hear the effect by crouching close to one cabinet and with one ear pointed towards it ,
then move up and down so as to listen on all of:
ear at tweeter ; ear about half way between tweeter and mid-dome ; ear at mid-dome.
When listening further away you will need a chair that allows you to have your ears at the height you preferred for the close test.

Listening at heights significantly above the tweeter and significantly below the mid-dome will result in peculiar tonal balances.

The review is interesting in other aspects - thank you for posting it !

Post your listening impressions after you have listened awhile with the new capacitors and L-pad in ,
and then we will consider reduced resistance inductors in the woofer filter.

I refer you also to my Post #925 on Page 93 , in particular to:
(4)- The upper bass problem may be owing to how you have blocked off the ABR/passive radiator.
Is it still in the cabinet , and with some thing fixed over its front ? ,
or , is it removed and something fixed into the open space ,
and if this latter then how thick and stiff is the new fixing and how well sealed so no air gaps around it ?
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Last edited by alan-1-b; 5th March 2013 at 06:36 PM. Reason: to add a paragraph
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Old 7th March 2013, 12:36 AM   #946
reggie is offline reggie  Australia
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Old 7th March 2013, 12:57 AM   #947
reggie is offline reggie  Australia
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Hello Alan. Thank you for vetting my draft crossover. The above post incorporates your changes (I hope). Unfortunately I cannot purchase anything right now. My wife has left for South America (she said she was going to the shops but I got a text from Manchu Pichu saying she would see me in April) and she has the credit card - I'm not allowed to have one because of my condition. Maybe by then you will have sorted the inductors. Alan, you asked about whether the level of treble was ok for my ears. But that's pretty difficult to assess when one has lost their frequency register. So, I often think that I am missing the full spectrum of sound. My gauge is the sound of cymbals. On something like Michael Frank's album "The Art of Tea" (featuring the great guitarist Larry Carlton) on the track "Eggplant" I can hear everything (so my wife assures me) whereas on something like Wishbone Ash's Album "Argus" at track no 6 "Warrior" about a minute in the music goes quiet with just a guitar playing a soft lead tune. BUT, if I put my ear to the tweeter I can hear the drummer playing a lovely rat a tat tat on the cymbal with the drum stick which I cannot hear from my listening position but my wife can. So, I can only conclude that if a high note is played too softly, is mixed too far back by the engineer or is just too high for my aged hearing then it's not going to be heard by me. As regards the bass I have taken the board off the passive woofer and am happy with what I hear. I think this is also highly dependent on how a record was produced. I think I will leave this at this for now until I hear from you re the inductors. I have one other question for you or other readers who have maybe experimented and that is as regards the foam stuffing inside the Celestion cabinets. Mine is stuffed head to foot with 3 inch yellow foam. Is this correct?

Reggie
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Old 15th March 2013, 06:48 PM   #948
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Default Corrections to #946 , and replies to #947 , and do we have sba and DennyG reading ?

G'day Reggie ,

In your schematic in #946 , the woofer circuit is now correct ,
however you have omitted the 3.9/4uf + 3.9 ohms in the midrange circuit !
{ The mids circuit was correct in your schematic in #941. }

The L-Pad resistor combinations around the tweeter are NOT correct in #946.
They should be:- 1.2 ohms with 15 ohms , and 1.1 ohms with 18 ohms.

Note to other readers ,
these L-Pad values are only for application with a Hiquphon OWII tweeter , and not for any other tweeters we have discussed to date in this thread.
-

Reggie , if I was to go to Machu Pichu I might not come back !
thus it is fortunate for you that I do not have your credit card.

A while ago my cousin in Australia and I were discussing international payments for components , etc ...
He said that in Australia there are Debit cards available which can be used on-line as substitute for the Credit card information the sellers require.
They are issued by the Banks and Credit Unions and Building Societies there , and are Master Card and Visa Debit cards.
None have annual fees , though some banks apply small monthly fees ,
however my cousin has one with a Credit Union that does not charge any fee for it.
There is an International Currency Transfer fee , and that varies between 2.5% - 3% depending on which Bank or Credit Union.
The good thing about these Debit cards is that one can only spend one's own money ,
because they draw only from what one has in the linked account ,
thus one cannot overspend , and there is no Interest charged because one is using one's own money , not the bank's.
Perhaps you can get one of those for your own use ...

I do not have a copy of Michael Franks' "The Art Of Tea" -{ though I do drink tea ...} , and it is a very long time since I heard it ,
and about the sound I can remember only that it likely had a tidily balanced mix of the type common for such music in that era.

I do have Wishbone Ash - "Argus" - it is one of my favorite albums from way back soon after it was originally released !
... it was a Classic album of its era , and remains such I think !!
I have the original vinyl LP plus a later copy as the original got a bit worn ... of course ... and two CDs.
One CD is a direct transfer of the original tapes , plus one extra song that had been originally released only on a 7" single ,
and the other CD is the 2002 "Expanded Edition" , which sounds like a re-mix because a few instruments are placed slightly differently in the stereo field ,
and are at different levels to the original.
It sounds like a Digital re-mix , and possibly the original analog multitrack tape was copied to a digital multitrack before remixing.
This CD has 3 extra tracks - all from a live concert from Memphis , and are songs from the band's earlier albums.
Which version of the CD do you have ?

I am not sure where I have put the first CD , so I listened to only the later CD before replying here.
Its sound is noticeably brighter than the original CD and the LPs , and that is quite nice for the Acoustic Guitar parts ,
though I'm not entirely convinced it is necessarily better for any of the rest.
For the track "Warrior" - you are referring to the section that starts about 1 minute in from the beginning.
The quiet cymbals' pattern there continues behind some vocals , and there are 2 guitars playing ,
and that cymbal pattern continues till about 3 minutes in till the band change rhythm.
That is what I hear in the mix on the "Expanded Edition" CD.
The cymbals are fairly quiet , though I can hear them with no difficulty with the volume level moderate in my medium-small listening room.

After you install the 11uF cap in place of the 8.2uF to the tweeter the lower treble will fill in , and I think you will better hear that cymbal part ,
unless you have the earlier CD and it is mixed differently ... ?

-

FOAM STUFFING :-

sba and DennyG ,

The foam stuffing - 3 inch thick - is it only a single 3" layer against all walls inside your cabinets ,
or is there double thickness or more in some places ?

For the bass response to be even and no major internal resonances inside the cabinet that tall cabinet needs at least one quarter of its height filled.
That can be one eighth at top and one eighth at bottom , or all at bottom behind the ABR/passive radiator.
For balanced control of the ABR it will likely be better if the entire area behind it is filled , firmly , but not stuffed tight.
Behind the woofer needs to be only 3" on both side walls but perhaps thicker than 3" on the back wall , because ideally one quarter of the depth should be filled ,
however if the entire space behind the woofer is filled that may be to obtain the bass damping that Celestion wanted ,
and I would not necessarily change it , but I might experiment with the foam there only on the sides and back to hear how different the sound is.
The 3" should continue on both sides and back to the top , and 3" under the top would be useful.

For Acoustic grade foam to work , it must NOT be stuffed compressed very tight , but only firmly placed so that it cannot move around ,
because if any internal damping material moves like a large floppy area when the woofer is moving , the woofer becomes unevenly Mass Loaded ,
and that detrimentally affects how it works.
The only movement in damping materials should be very small local area movement within the material - too small to see moving.
Damping material needs to vibrate as very small movement , as that is random phase and does not load the woofer at some frequencies differently to at other frequencies.
If the damping material is compressed there is not sufficient space between its fibres for them to vibrate in , nor for sufficient quantity of sound waves to penetrate.
The above also applies to damping material inside sealed mid-range enclosures and inside tweeters behind the dome.

-

INDUCTORS :-

Do the interested persons here want to wind their own inductors , or buy ready wound ?
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Old 17th March 2013, 06:26 AM   #949
reggie is offline reggie  Australia
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Hi Alan.
Thank you for actually looking at my diagram. Obviously it was more than I did. A note on credit cards. I got my first - and only - credit card in 1975 and spent my maximum in 1 day (by purchasing a motor-bike for $3000). When I got home I realised the type of person I could become and cut the card up. So now if I haven't got the cash it doesn't get bought. I could get a debit card but I use my wife's instead heh heh.
Michael Frank's "The Art of Tea" is a very beguiling record. It's humorous lyrics and understated playing leads one to dismiss it but.. The final track - Mr Blue - with just piano, guitar and voice and with several complicated changes of tempo is delicious.Anyhoo, I also have the expanded (3 extra tracks) version of the Warrior CD. In common with many other re-releases I find it too bright. Several exceptions to this are the wonderful 40th anniversary editions of Jethro Tull's "Aqualung" and King Crimson's "Islands" and a 2 cd re-release of John Martyn's "Solid Air" (Thick as a Brick was also a 40th anniversary release but something bad must have happened).
Thank you for the note on the filling. Obviously, it's something to experiment with. I might try some pink fibreglass batts (wearing a mask and gloves)(oopps there goes the F/A 18 war planes overhead. A flyover for the Melbourne F1grand-prix on this afternoon) and some synthetic stuffing.
For my money I will probably buy the inductors otherwise they will never be done.

Reggie
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Old 24th March 2013, 05:31 AM   #950
DennyG is offline DennyG  Australia
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Default Responses to posts by Alan

Alan, I've missed some of the recent discussion and suggestions so I've included some comments below under the post #

#925 #931 & #935
DIFFRACTION & FELT ON FRONT SPEAKER PANEL
I think adding the felt might be a very good suggestion Alan. It may help to smooth out the sound a bit. I need to work out what the diagrams you have drawn mean and source some suitable material. It may be a while before I can get to do it but I can source the material in any case. The link to David Ralph's Speaker Pages is appreciated as well as
SAE & Sheet Felt

#937 RESISTORS IN BASS CIRCUIT
---> DennyG - you have effectively 74uF in the central cap's position.
Ideally the 6.2uF cap you connected there needs its own separate resistor.
Use 8.2 ohm or 10 ohm in 1 watt Carbon film from a local shop.
If you have some 1 watt resistors already , then so long as not less than 4.7 ohms or larger than 12 ohms , try those you have.

I think I have (measured values) 66+6 and 67+6 in the central position. What would be affected by adding the 8R-10R to the 6uF's? I assume the resistor should go straight to the common and not to the 1R.

#940
FILE STORAGE FOR DIAGRAMS
The exetel site (it's an ISP) I used to store some files for easy access is a private site for exetel customers. I decided to use it because all the free sites I tried in the past either: deleted the files after a short while; were bought out and closed down by the big boys to crunch the competition or just disappeared. Some ISP's offer free space for file storage so this would be worth checking out if you need to have a reliable place for this sort of thing.

SPEAKER TESTING
When I start testing again I might have to go back to the old system as I haven't had success getting the USB audio interface to do what I want to do.

Note that all the speaker tests were done using the same (left) channel of the amplifier to avoid the inevitable channel differences you mention.

For amp tests I don't have 6.8R but I have two 8 ohm 50W resistors, will these be ok to test the L/R channel freq response? Power level for these tests? Say 5W?

If I remove the crossovers I'll try what you suggest for each channel using dummy R's. Again 5W say?

#948
INTERNAL SPEAKER FOAM
From what I remember the foam is layered on the sides, rear, top and bottom but next time I open them up I'll check. When adding foam what types should be used and what should be avoided? I've various types of absorbent material lying around so what should I avoid?

INDUCTORS
The inductors might be a worthwhile upgrade but what frequencies would be affected? And what inductors are you talking about?
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