Crossover nightmare!!!!!!!

[tinitus]

Originally Posted by LucasAdamson

Tinitus, I din't mean to be rude

Its your right to right, I respect a man who talks straight

Maybe they're a terrible design and I should really change them a lot, like removing caps completely and changing values

No, I never implied that, I wouldnt be here if they were
When you asked how a better xo design would look, I said "not much different from now"

but you're contradicting your earlier advice not to change much, so it gets very confusing and not helpful in the end.

I did say "if you like them as is, leave them be

Again, sorry if I was rude. I know you were trying to help, and I may look back later and see that you were right about some things.

If changing caps, which does cost money, I see no reason not to try and do it better
Mind you, some of my suggestions could actually save you money, even if using better components
To change the now obviously OK working components fore some of the cheapest available seems a bit pointless to me, sorry

Lucas

Well, we are here to be critical, not negative
Unfortunately they go all too well together

And yeah, dont believe all we say
Maybe I went too far in my questioning doubts about the easy explaining of what goes on in an xover
Maybe Im the one who doesnt understand the simplicity
Well, I admit I dont

My appology, I tried too hard

[LucasAdamson]

Well, I've changed the caps in one of my speakers so far: treble 4uF and 6uF caps and the midrange 33uF and 6uF caps with Jantzen polyprops, and both of the bass 72uF caps with bipolar electrolytics, with no series compensation resistors anywhere at this stage, and have this to report: the sound has changed very little indeed. I'm unsure whether I'm happy or not about that...on the plus side it means that nothings ruined, but then again, there's a bit of "what's the point?"

I have no balance control, which slightly complicates comparison, but with both old and new configurations playing together, there is little to report, if anything.

Perhaps alternating between the two using a mono signal will help discern the difference. I'll see what I can wire up tomorrow.

Lucas

[tinitus]

Hmm, thats probably ok, I guess
But I can understand if you had some expectations

I may be able guide you to determine whether a few small adjustments could be of some benefit
But I wont promisse any improvements, other than that it wont ruin anything so that it can always be brought back to original state, and it wont cost much either

[LucasAdamson]

Hi Alan. OK, I've changed all the caps in both speakers, and after a quick listen I now realise that they do sound quite different.

More detailed, sweeter, but also a touch colder. They are less warm than they were and I suspect they are lacking a touch of the lower midrange they had. The midrange seems to be more aggressive, much more forward than they were. Another way to look at it is to say they are more detailed and have lost the fuzziness they had.

I will add the resistors tomorrow, to see the effect, because these effects may be due to the mid and treble being more pronounced due to the new poyprops removing the inherent resistance of the old electros, and hopefully resistors will knock them back to where they were. Did I understand that right Alan?

The only way to suspend the resistors in air on all surfaces is to place them close to the drivers. Is that ok?

[tinitus]

The new components may need to sit there fore a while before they are at their best
Just play a lot of music and they may change, bit by bit
May be a bit early to judge them

Also important to have both speakers alike to play in stereo before you can fully evaluate them

[LucasAdamson]

Originally Posted by tinitus

Hmm, thats probably ok, I guess
But I can understand if you had some expectations

I may be able guide you to determine whether a few small adjustments could be of some benefit
But I wont promisse any improvements, other than that it wont ruin anything so that it can always be brought back to original state, and it wont cost much either

Thanks Tinitus. I will introduce the resistors tonight, and see how that changes things, because it now seems that Alan was quite right about the inherent resistance that the old electros put out. The sound report I made basically boils down to a very bass-light result, or rather mid and treble rich result, owing to the impedance changes in the mid and treble. Celestion obviously allowed for that in their design. I'll report again tomorrow when I've finished and had a listen.

[LucasAdamson]

Originally Posted by wintermute

Hi Lucas, yes I believe you are correct in saying there is no impedance compensation, it just looks like a standard low pass filter on the woofer to me.. That is why I said if you add it, it will almost certainly change the sound of the speakers I thought you were mostly interested in keeping the crossover as close to original as possible but upgrading the aging capacitors... I haven't seen some of the more recent posts, so sorry if I missed some important info...

Tony.

Hi Tony. The reason to add resistors to the mid and treble drivers, is essentially because I am changing from electrolytic caps to polypropylene in those circuits, and the old electros had an inherent resistance which is not found in the new cap, a resistance that if not re-introduced, will lead to the mid and treble being too forward, which is exactly what I've found now that I've replaced the caps and not put resistors in. I am putting the 5 watt wire-wound resistors in tonight and will let you all know whether this worked. They are large MOX type resistors.

[LucasAdamson]

Well everybody, I added 1.5R resistors in electrical series before the mid speaker tonight, and this has set them back to near where they were and brought quite a bit of balance to things. It's late so I can't crank it up and hear them properly, but at lower volumes they sound not so aggressive now. Thanks everybody for your help

I may go up from 1.5Ohm to a 2Ohm, as you say this will possibly further set back the upper mids, and I like warmth.

I think I will also buy and add a 0.5R before the tweeter to set it back a touch, as you suggested Alan, because it does seem a little pronounced and to need very slightly attenuating.

Maybe then I will call it a day for a while, before thinking about inductors.

Maybe L-pads would be good, one for tweeter and one for mids, each with a few resistor choices ????? It always seemed to me that you can discuss the "tone" of your amp and record deck and pre-amp and all the other stuff in your hi-fi, and you're talking about tiny details, but the sound of speakers is MUCH less uniform and can vary enormously and the range of tonal balance with speakers is vast compared to everything else, so it makes sense to be able to adjust the tonal balance to taste..........Opinions on l-pads anyone?

[LucasAdamson]

My conclusion after a week of listening is that they now sound pretty amazing if I'm honest, and others have said so too, including Lorien, who also has a pair of these downstairs. Thanks ever so much Alan et al. I could never have done such a good job of choosing caps and resistors without you. I settled on 2.0 ohm resisters for the mids in the end, and 0.5 ohm resistors for the tweeters. They have the balance just right now, to my taste/ hearing.

Thanks again to all who helped. I will look into inductors in the future...

[alan-1-b]

I see several Posts to reply to, and I will reply to all of them, though probably not sufficient time today to get through the lot, thus please be patient for a few days.

Originally Posted by tinitus

Pardon me if wrong, but are there not TWO equally sized value 72uf in paralel on woofer ?
Its pretty daft
If it at least dont ruin response too much, it certainly will screw up phase
I dont understand how they left it like that
I bet almost anything else works better
But at the time I believe it was one of those slick ideas some believed in

Man, there have even been very skilled guys who made 2ways 12db with equally sized mirror imaged reversed values on woofer and tweeter, or whatever we should call it

Hi tinitus,

Is it the 2.2mH inductor in electrical Parallel with the Series network of 72uF + 72uF = 2.2mH//36uF resonant circuit -{a Tank circuit, the old Radio fellows used to refer to such as}- that is worrying you ?

Such would be a relevant concern in some circumstances, but I doubt it is here.

To cause a significant audible resonant problem, at about 566Hz, the Impedance from the centre tap -{of the two caps}- to the Ground return at the amplifier would have to be a significant size.
Such can occur, and does in some Power Supplies with that type of filter when used after the rectifying diodes in the Secondary circuit of the Transformer - when there is a significant Impedance between the caps' Common point and the input of the filter via the transformer windings.

To be significant in a loudspeaker x-over, the cable's resistance between x-over and amplifier would have to be large-ish.
I don't know if a 2ohm cable loop would allow an audible resonance to build up, but likely 4ohms loop would.
Unless the cables are very long or very thin, their loop is probably about 1ohm,
and there is a small DC resistance through the 3.5mH inductor -{how much Lucas ?}.

BUT, that x-over circuit is NOT only a 2.2mH//36uF Tank.
Consider the behavior of ALL the other components connected around it.

Let us consider the initial millisecond of time following a signal pulse arriving at the Input to the x-over, and for the bass filter circuit.

First there will occur an anti-resonance through the 3.5mH <--> first 72uF path at about 317Hz.
Extremely soon after there will follow the anti-resonance through the 2.2mH <--> second 72uF path at about 400Hz, and then the 566Hz Tank resonance of 2.2mH//36uF, but very very soon after will be another Tank resonance caused by the driver's voice-coil inductance -{a currently unknown to us mH - let's name it Lvc}- and the Parallel 72uF cap --> Lvc//72uF, at an unknown to us Hz.
All these will interact within the initial millisecond, and such will determine the action of the filter, along with the shape of the frequency response of the bass driver.

The Lvc//72uF tank is reduced in onset and in magnitude by the driver's voice coil DCR -{about 4.5ohm - what do yours measure Lucas ?}-,
AND by the ESR of the 72uF cap, which is about 1ohm around the 300Hz<-->600Hz region.
Similarly, the ESR of the other 72uF cap will reduce at least a little the onset and magnitude of both the Tank resonance and the anti-resonance through it, as also will the DCRs of both the 3.5mH and 2.2mH inductors.

Likely the filter could be fine-tuned to better performance by changing one or perhaps both of the caps' values a little, but probably only by a very little,
and there was not then a sufficiently wide range of caps' values available for engineers to do this cost-effectively for Consumer Products that have limited Retail Price ceilings before buyer resistance starts !

One would have to do a lot of measuring to determine the optimum, but for home-users the final decision is based on listening enjoyment versus money available.