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Dev
Junior Contributor 20+
Joined: 17 Aug 2012
Posts: 24
Location: India
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 Posted: Fri Aug 17, 2012 9:53 pm Post subject: 105.2 woofer identification |
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Hi, Being an infant in the Vintage HiFi fraternity, I seek guidance from members in identifying the woofer on my recently bought 105.2.
Are they originals? Have they been repaired? The dealer I bought these from said 'All Original' but that may be to sell talk.
Please guide me on this .
Regards
Dev
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[URL=http://imageshack.us/photo/my-images/62/wooferd.jpg/]
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audiolabtower
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Dev
Junior Contributor 20+
Joined: 17 Aug 2012
Posts: 24
Location: India
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| Posted: Sat Aug 18, 2012 9:55 pm Post subject: |
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[quote="audiolabtower"]Possibly been repaired? The surround may be ok but the dustcap has definitely been replaced. Original looks like this
Thanks for the reply.
Today I got the woofer removed to fix the input terminal & following pics show the details...
As you have mentioned, they are original B300 but repaired again as you observed.
Please advice if any improvement can be done on them as Bass is hardly felt/ heard till 11'o clock volume knob position.
regards,
Dev |
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audiolabtower
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| Posted: Sun Aug 19, 2012 1:47 pm Post subject: |
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| Looks like it has had a voice coil repaired or replaced. A non original will change the design but not necessarily to the extent of having no bass. Looking at your terminal hole I would guess the cabinet is no longer airtight? and therefore no longer a closed box? This will definitely upset the bass and would be my first guess at your problem. Replace the terminal making sure no gaps and airtight, then screw down the bass unit to a high medium but not really heavy tightness. We have speaker designers here who may even be able to tell you the design torque! The bass unit is on rubber mounts which must be airtight but not tight enough to transmit vibrations through to the wooden cabinet in this design. |
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speakerguru
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Joined: 18 Nov 2005
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Location: Green Hut, Tovil
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| Posted: Wed Aug 22, 2012 8:44 am Post subject: |
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Everything looks correct except for the repair. I imagine that this is a pair of working B300s cobbled together from some with broken cones and some with burn coils. The good cones have been grafted onto the ones with good coils and then a large dustcap has been used to hide the join.
Do they measure ~ 6 Ohms with a d.c. meter? If so, then they should work OK.
Re your other queries. Yes the amount of foam looks about right, and there should be a C5 on the XO board. The value of the big capacitor in series with the woofers is not critical but you should measure to check that none of the capacitors have dried to an open circuit with age.
Re your reported lack of bass. Have you listened to the bass cabinets on their own without the heads? Maybe your expectations on the amount of bass are too high. This was designed as a high-fidelity loudspeaker, not an in-car boom box nor a drum 'n bass club setup. Try listening to a good orchestral or acoustic jazz recording, then report back. |
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Dev
Junior Contributor 20+
Joined: 17 Aug 2012
Posts: 24
Location: India
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| Posted: Wed Aug 22, 2012 7:39 pm Post subject: |
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[b]" | speakerguru wrote: | Everything looks correct except for the repair. I imagine that this is a pair of working B300s cobbled together from some with broken cones and some with burn coils. The good cones have been grafted onto the ones with good coils and then a large dustcap has been used to hide the join.
Do they measure ~ 6 Ohms with a d.c. meter? If so, then they should work OK."
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Thanks a lot for a much awaited reply. I really appreciate the effort & time you took out to reply on my concern.
I will check tomorrow & post about the Ohms factor. |
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Dev
Junior Contributor 20+
Joined: 17 Aug 2012
Posts: 24
Location: India
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| Posted: Wed Aug 22, 2012 7:45 pm Post subject: |
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| Quote: | | Re your other queries. Yes the amount of foam looks about right, |
This is a surprise ! But since you have certified , I will go with it. Please direct what is the best I should use? Foam? What density? Or anything else that will do the job better. |
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Dev
Junior Contributor 20+
Joined: 17 Aug 2012
Posts: 24
Location: India
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| Posted: Wed Aug 22, 2012 7:56 pm Post subject: |
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| Quote: | | and there should be a C5 on the XO board. The value of the big capacitor in series with the woofers is not critical but you should measure to check that none of the capacitors have dried to an open circuit with age. |
This capacitor should be NP ? Also all the others, Shall I change to NP? I read
that using NP music sounds better, Is that correct??
| Quote: | | Re your reported lack of bass. Have you listened to the bass cabinets on their own without the heads? Maybe your expectations on the amount of bass are too high. This was designed as a high-fidelity loudspeaker, not an in-car boom box nor a drum 'n bass club setup. Try listening to a good orchestral or acoustic jazz recording, then report back. |
[/quote]
I appreciate your reasoning but most of my music consists of Indian Classical & Instrumental along with Western Classicals & fusion... No heavy metal or hard rock! N none of my cars have a music system as I drive my classic cars on daily basis !  I respect your observation & will revert. Cheers! |
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speakerguru
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Joined: 18 Nov 2005
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Location: Green Hut, Tovil
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| Posted: Thu Aug 23, 2012 8:28 am Post subject: |
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| Dev wrote: | This capacitor should be NP ? Also all the others, Shall I change to NP? I read
that using NP music sounds better, Is that correct? |
Both the Elcap and Alcap capacitors in your photos are the reversible electrolytics used by KEF in production. The XO design takes into account the loss factor of this type of capacitor. If you want to change to non-electolytic types then you must add series resistance or the response will not be design intent. |
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Dev
Junior Contributor 20+
Joined: 17 Aug 2012
Posts: 24
Location: India
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| Posted: Thu Aug 23, 2012 8:38 am Post subject: |
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| speakerguru wrote: | | Dev wrote: | This capacitor should be NP ? Also all the others, Shall I change to NP? I read
that using NP music sounds better, Is that correct? |
| Quote: | | Both the Elcap and Alcap capacitors in your photos are the reversible electrolytics used by KEF in production. The XO design takes into account the loss factor of this type of capacitor. If you want to change to non-electolytic types then you must add series resistance or the response will not be design intent. |
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Thanks ! Keeping the same values & types, do you suggest changing to the best available capacitors ( solen or any that you think is better) ? Will that do any good? I am told caps are good right now in values, have not dropped. But this test is done while they are mounted. Shall they be taken off & measured?
Regards
Dev |
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speakerguru
Über Contributor 1000+
Joined: 18 Nov 2005
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Location: Green Hut, Tovil
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| Posted: Thu Aug 23, 2012 5:52 pm Post subject: |
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| Ideally you should unsolder and lift one leg of each capacitor and then measure the value (capacitance) and also the losses (dissipation factor/tan delta or series resistance). I do not have a much experience of measuring old capacitors but I believe the losses change more that the value as they dry out with age. I do not believe any particular capacitor brand "sounds" any better than any other if the value and loss are the same. |
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Dev
Junior Contributor 20+
Joined: 17 Aug 2012
Posts: 24
Location: India
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| Posted: Thu Aug 23, 2012 7:42 pm Post subject: |
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| Quote: | Everything looks correct except for the repair. I imagine that this is a pair of working B300s cobbled together from some with broken cones and some with burn coils. The good cones have been grafted onto the ones with good coils and then a large dustcap has been used to hide the join.
Do they measure ~ 6 Ohms with a d.c. meter? If so, then they should work OK |
.[/quote]"
I got them checked thru a DC meter, measuring 8 ohms Iam told.
I guess I should elaborate the lacuna with the speakers. In my observation, is the bass,or lack of it, leading to lack of 'warmth'. The soundstage is fantastic, they disappear in no time. Treble is good, though I find details a little less crisp but I guess that's okay with speakers of that age. Still it's the depth in music which I am unable to get. I hope all the seniors can understand my non technical language & feel what I am trying to explain.
Please guide me if I am wrong in my expectations or else how do I get the warmth & depth in the music.
Regards,
Dev  |
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Dev
Junior Contributor 20+
Joined: 17 Aug 2012
Posts: 24
Location: India
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| Posted: Thu Aug 23, 2012 7:46 pm Post subject: |
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| speakerguru wrote: | | Ideally you should unsolder and lift one leg of each capacitor and then measure the value (capacitance) and also the losses (dissipation factor/tan delta or series resistance). I do not have a much experience of measuring old capacitors but I believe the losses change more that the value as they dry out with age. I do not believe any particular capacitor brand "sounds" any better than any other if the value and loss are the same. |
Thank you ! Will get the test done tomorrow & report back. Can this be done using a multimeter? |
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speakerguru
Über Contributor 1000+
Joined: 18 Nov 2005
Posts: 1192
Location: Green Hut, Tovil
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| Posted: Fri Aug 24, 2012 10:04 am Post subject: |
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| Most multimeters will not measure capacitor loss factor. You need to get an LCR meter which has this feature. |
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Dev
Junior Contributor 20+
Joined: 17 Aug 2012
Posts: 24
Location: India
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| Posted: Tue Aug 28, 2012 2:02 pm Post subject: |
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| speakerguru wrote: | | Most multimeters will not measure capacitor loss factor. You need to get an LCR meter which has this feature. |
I will be able to check the caps with LCR meter tomorrow & post the result for further direction.
Meanwhile, here's the circuit diagram of the Xover in present form.
May i request experts n seniors to take a look & suggest if all's gud except the missing C5. (will that be NP ?)
The serial No. is 10065 & 10066., & the date in the cabinet says 14 may1984.
Does this help?
Last edited by Dev on Tue Aug 28, 2012 3:56 pm; edited 1 time in total |
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