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Old 8th September 2012, 07:37 PM   #901
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Location: Midlands
Default interims to: sba & nigel pearson , including about LS3/5a

Hi sba ,
great stuff - your CSD plots , etc ...
Thankyou for posting these !
I see you have some JBL and Altec also - more than I will have time to comment on for a long time,
except to say now that both loudspeakers can be improved, especially the JBL.

--- --- --- --- ---

'ullo Nigel ,
yes, a lot of the sound character of the LS3/5a is owing to its crossover, and in part that tapped inductor.
The purpose of the tapped inductor was to compensate for sample variations amongst the tweeters,
though modern manufactured tweeters should be more consistent/less degree of variation between samples.
For Music reproduction I prefer to not use cored inductors, but some designers insist we cannot hear any detriment result of the core so long as it is suitable size for the intended power dissipation within it.
OK , some people don't hear it, but some people hear differently to others, and the simplistic Text Book engineers will not allow for that ,
because they have not read modern in-depth Audiology text books, and they don't hear what some other people do hear.
I respect the LS3/5a design, and understand what it was intended for:
near-field monitoring of speech for long periods of time, primarily for Radio Broadcast.
It was not designed to portray accurate Timbre of musical instruments, as the BBC had other monitors designed for that.
I can accept that some listeners like its peculiar timbral character,
though mostly what enthusiasts of it like is its Imaging - and that is an artefact of its design, and not actually the truth of the audio signal.
There is PART similar in the Celestion 44 and 66 , which is why I mention this here, because I think Reggie could be hearing that in the treble.

Why are you "too lazy these days" ?
You can be not lazy and help us here:
For a tweeter with 6.5 ohm impedance in the middle of its audio-band ,
with an L-pad of 15 ohms Parallel and 1 ohm Series - how much attenuation in dB ?
I estimate about -2dB or slightly less ... if you have whatever necessary, can you calculate closer for us please ?
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Last edited by alan-1-b; 8th September 2012 at 07:40 PM. Reason: to add a phrase
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Old 8th September 2012, 08:43 PM   #902
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Default interim to Reggie

Quote:
Originally Posted by reggie View Post

(1)- But, on many so so recordings I get the impression the higher frequencies have been mixed too far back and I am not getting all the picture.

(2)- By the by I am not at all sure where the tweeter take over from the mid . Is it in the violins or cymbals?

(3)- Same again between the bass and the mid. What should I be listening for?

(4)- With the recent changes you suggested I think I'm hearing more upper bass but that's not possible is it?

(5)- Anyway, with regard to the make-up of my new crossovers I admit to being guided by the capacitor testing done by humblehomemadehifi. He appears to be the only one to test capacitors in a crossover scenario.

(6)- I am leaning toward the Obbligato's and the Jantzen Superior Z's

(7)- I would like to at least try the Obbligato 70uf film oil in the bass.

(8)- and the Jantzen elsewhere
Replies:

(1)- read in my comments to Nigel in #901 above: "There is PART similar ... "
The 44 and 66 have their tweeters connected in reverse Polarity to their mid and bass drivers.
This causes a Distance effect in the treble, but not everyone hears it like that, though I suspect you might be.
{ There is at least 2 distinctly different types of human hearing, and perhaps more ... }
Experiment: swap the leads around at the tweeter between + and - terminals ,
then listen again with exactly the same music as before the swap.
Ask you wife to listen before/after also ... but remember, her brain priority allocation may be different to yours in this aspect.
Possible complication: when the Polarity is swapped with a 3rd Order crossover , which this one to tweeter is, the Vertical off-axis lobes swap over ,
thus that lip at the top of the cabinet will reflect treble differently, and may be audibly more unpleasant, and there-by confuse any other audible effects.
You should first stick some soft absorbent material under that lip down to the top of the tweeter flange, and along under the lip to the sides of the cabinet.
Temporary is to use rolled up Wool socks - real Wool , not Polyester because it does not absorb as well.
If you like the sound, then your wife may be familiar with Haberdashery or Crafts shops.
If so, buy some very soft wool felt, or very soft cotton felt if no wool, but NOT a polyester or nylon blend.
Roll it up to optimum thickness to fit to cover all the under side of the lip,
but do not roll it tight - it needs to be loose enough to remain soft to absorb sound.
Stick it in place with double sided tape, or similar that your wife may be able to do with Velcro.
If she wants to sew the roll to hold it together, then sew it only at its ends where it meets the sides of the cabinet.
Do not sew it tight where it is will be anywhere near the tweeter flange.
If the felt is compressed it will not absorb much sound.
-
(2)- read back though this thread to where I posted about solo violin recordings to DennyG.
Do you have any of Bach's Partitas and Sonatas for solo violin ?
If you like such, but don't own recordings, I will list some that are musical more-so than too scholarly technical so that you can enjoy the listening.
It is more difficult to decide about audio balance when listening to things one does not enjoy.
Soprano vocals also, true Soprano, not Mezzo singers who can also reach high notes, because Mezzo voices are richer in lower midrange harmonics even when singing high notes.
{NB: Soprano are Female, not that TV show or Movie about Male Gangsters, or whatever they are ... OK, you likely know that, but I'm getting in before the jokes !}
-
(3)- I'll describe this when we get to modifying the mids of the crossover.
-
(4)- yes, it is possible.
-
(5)- there are a few others, but more-so in posts in Forums than on dedicated web-pages.
-
(6)- these are very large size ! They may not fit on the Celestion board.
Are your Solen caps the 250 volt or 400 volt or 630 volt size ?
I think the Mundorf you have is 400 volt size .. ?
-
(7)- those are intended for Power Supply filtering, and may not be suitable in a crossover, but I do not know ... however look at their size:
55mm x 125mm , that is slightly larger than 2" x 5" !
Also, the Solens are OK there, and I doubt you'll hear much difference in that part of the circuit unless you happen to have very microphonic samples of the Solen.
You can use your Solen 8.2uF cap there later to increase the filtering. I will describe how later.
-
(8)- The Jantzen Superior-Z caps are in limited values.
If you want to use use single caps there, and remember they are physically very large size, you will have to buy a new inductor because 0.14mH will not work at 5kHz with 3.3uF and 10uF caps.
There is the Jantzen 20AWG aircore 0.15mH listed on Speakerbug. That would be suitable,
and not the other Jantzen 0.15mH there because it is too low in DCR. Some resistance is needed there.
If you want to keep the Celestion tweeter inductor you will need to buy 3.6uF and 11uF or 12uF caps.
It is possible to squeeze the filter a bit by slightly changing the effective Impedance, and then use the more common 3.9uF and 10uF values with the Celestion inductor,
but the result will not be quite as flat response through the crossover region.

First decide whether these huge Jantzen caps will fit ... then decide whatever else you would like to do about the above, then post decisions here.
Jantzen Superior-Z cap physical dimensions are here:
http://www.jantzen-audio.com/downloa...ies%20list.pdf
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Last edited by alan-1-b; 8th September 2012 at 08:59 PM. Reason: to add a line
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Old 9th September 2012, 11:24 AM   #903
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The tweeter problem is the typical British solution . A freind made speakers which had additional units to replace lost information in the crossover region . They could reproduce square waves accurately . I loved the speakers . Alas his skills in selling them were zero and they were dammed with faith praise . In my opinion he was reviewed and not his product . I wish I had bought a pair . Even more so than Quad ESL they told truths seldom heard . Not just tonality or low distortion , nor even imaging . Layers never heard before or after . These layers are not supposed to be heard and would annoy some . The speakers worked with modest amplifiers , most surprisingly even the Quad 306 . Amplifier coloration was more oblivious using them I than I ever remembered . Very bright yet not at all fatiguing . Only speaker I ever used which had a genuine 20Hz response .

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Old 9th September 2012, 11:24 AM   #904
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The tweeter problem is the typical British solution . A freind made speakers which had additional units to replace lost information in the crossover region . They could reproduce square waves accurately . I loved the speakers . Alas his skills in selling them were zero and they were dammed with faith praise . In my opinion he was reviewed and not his product . I wish I had bought a pair . Even more so than Quad ESL they told truths seldom heard . Not just tonality or low distortion , nor even imaging . Layers never heard before or after . These layers are not supposed to be heard and would annoy some . The speakers worked with modest amplifiers , most surprisingly even the Quad 306 . Amplifier coloration was more oblivious using them I than I ever remembered . Very bright yet not at all fatiguing . Only speaker I ever used which had a genuine 20Hz response .

Orchid Audio PLL1 [English]

Seems a duplicate !!!!
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Old 11th September 2012, 05:56 AM   #905
reggie is offline reggie  Australia
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Default New Crossover

Hello Alan,

Some responses to your questions and suggestions.

1(a). I have played with the tweeter polarity so many times now. The present iteration is that the polarity is reversed at the tweeter terminals. However my pre amp is a valve OTL (a TRAM 2) which the designer, Thorsten Loesch, said reverses polarity so my speaker wires are reversed at the power amps. I have also tried reversing only the midrange. I’ve tried all combinations but cannot truly say I hear a difference. Also, I’m not sure what the polarity is at the crossover itself. Regarding the recessed HF It may be relevant to quote from a review compiled by High Fidelity Magazine on the “Ditton 66” (wood faced) in the late 70’s....”Triangles, bells and such, which have their energy concentrated almost exclusively at the higher frequencies, are reproduced very well, albeit perhaps not quite in perfect loudness balance with the rest of the orchestra. In listening tests the reduced relative high-end response shows up mainly as a lack of sparkle and transient response that, though fairly good, is not up to the best we have heard. On the other hand, that same characteristic lends a sweetness to the sound that is quite appealing. There is no trace of harshness or hiss and yet the highs are indeed there – right out to 16kHz...” Is this relevant?
1(b). I have had wool felt around the tweeter (and midrange) since early last year. I got the idea from some of your earlier posts and from a 2005 article I found on the internet by a David Ralph entitled “Diffraction doesn’t have to be a problem” (www,speakerdesign.net). What I seemed to achieve was a greater focus to the music.
2(a). I will go back and look for the advice you provided to DennyG re listening to violin music.
2(b). I have 3 classical CD’s: (i) Beethoven Concerto for Piano, Cello and Orchestra in C combined with Boccherini’s Concerto for Cello and Strings in G (ii) The Best of Boccherini and (iii) Pegolesi”s Stabat Mater with Gillian Welsh soprano (which I really like) but in general I’m more middle of the road, with some left of centre stuff.
3. Ok
4. Ok
5. Yes, I’ve read a few but nothing as exhaustive as this.
6. Solens 400v. Mcap 400v. As for the size well, the present crossover is in 2 parts, bass and mid/tweeter but my intention is to have the crossovers outside the cabinets (at least initially).
7. If you think it is a waste to get the big Obbligato’s then we will retain the Solens. My concern was with the disparity between the values of the original capacitors (144) and my current ones (136) so your suggestion to use the 8.2uf is welcome.
8. Alan, unless something unusual occurs, I will probably keep these speakers (I’ve had them for 36 years now). So I’m up for spending money on totally renewing the crossovers. That’s new capacitors, coils and resistors. You tell me what I need and I’ll get them.

What I’m hoping to get from this is: (a) improved clarity (which I interpret to be a greater intimacy with and insight into the music, (b) a tighter bass (nb. I’ve closed off the bass reflex speaker with no readily apparent loss of bass (my speakers are near room corners) and (c) maybe a small increase in efficiency (to get the Celestions to sing I have to turn up the volume slightly more than my wife appreciates)(even with the door shut). Quoting again from High Fidelity Magazine (stop me if you’ve heard this before)...”Although the efficiency of the Ditton 66 is about 3 and ½ dB below what we have come to consider average – CBS reports an on-axis sound pressure level of 83 and ¾ dB at 1 meter from a 0.dBW noise level, 250 Hz to 6kHz – it is an easy speaker to drive. The impedance curve is relatively smooth and well contained. Except for a 22.5ohm peak at resonance (49Hz) the load stays between 4 and 10.5 ohms throughout the audio band. We rate the impedance as 4.6 ohms (the minimum reached just above resonance) but over the important midrange the curve averages about 2 ohms higher: low, but not so low as to be dangerous...” and so on (there’s more of this technical stuff).

Several more questions please. Given my desire to try the Morel midrange at some future time (the MF500’s are not going to last forever - they are already 36 + years old and I need the Celestions to last another 20 years (I’m 63) will these new crossovers be compatible?

What is your view of tri wiring. What would have to change on the crossover and how would my push pull valve mono power amps (operating in triode) feel about feeding 3 x 12 gauge wires (Paul Speltz Anti cable). I’ve read all the pro’s and con’s on the internet: some say it’s good some say it’s bad and some say it makes no difference. I think it would be helpful for me in fine tuning the crossovers. I think at the very least I will bi-wire. I won’t be using (banana) plugs but rather some mechanical means of connecting the speaker wire to the crossover.
OK. Enough now.
Regards
Reggie
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Old 12th September 2012, 01:33 PM   #906
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If it is not a diversion you might like to see if any of this makes sense . I had the opportunity to buy this company . Alas as someone said you couldn't buy Joe . The company was Joe . An un-respected genius of speaker design . As far as I know not in business now ?

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Old 12th September 2012, 04:56 PM   #907
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Default Ditton 66: Midrange Noise

I own a pair of Ditton 44s... every once in a while, one might pick up a scratchy noise from the midranges... if you catch it early, (I was told) that if you take out the midrange, rotate it and then put it back in, the noise might go away...something to do with the weight of the magnet and the way the rear part of the cone sits in it.... one of the other techies in this forum may be able to explain more clearly why it happens... all I can tell you is that I did it and it worked!
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Old 12th September 2012, 05:05 PM   #908
Mooly is offline Mooly  United Kingdom
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Good that it worked for you.

I'd guess that the voice coil (on the cone) and the air gap it sits in, in the pole pieces of the magnet assembly have a very tight (too tight) tolerance and the coil is rubbing. If the weight of the magnet and rotating the whole driver fixes it then maybe the chassis of the speaker is subject to distortion (flimsy).

There's many a speaker that "rubs" when you hold the chassis and lightly twist it. Also many a speaker that rubs when the mounting surface isn't flat and the fixing screws twist the frame.
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Old 13th September 2012, 10:40 PM   #909
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Given the massive cast frame on the midrange of the 44 its not likely that its due to it being flimsy!
I'll bet Ditton Fan in your case whats happened is over the years gravity has taken its toll and the cone has sagged, this often happens where where the surround is very complaint and/or the cone very heavy. (in the case of the Dittons it'd be compliance) This then causes the voice coil in the air gap to no longer be central and to rub. An extreme example, A friend of mine owns a pair of Chartwell PM400's with massive 12" Bextrene bass units, after many rubbing problems he simply turns the bass units by 1/4 every six months - no more rubbing..
It would be worth you turning the other one too as if one has sagged its likely the other will and if not caught the rubbing can wear through the coil insulation causing it to short..
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Old 14th September 2012, 11:03 AM   #910
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Some people rotate Tannoys to extend life . Spendor BC1 drivers also . It also ensures bolts are tight . There was a craze of tweeter cone tightening . I offered to do it for my customers free of charge . It should be done finger tight so as not to deform or overly compress components ( gaskets ) . Spendor always said it was a dilemma whether to optimally tighten the rear cabinet screws or have them all the same . All the same won the day .
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