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more bass needed from my reference 105 II
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audiolabtower
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PostPosted: Thu Oct 22, 2009 11:34 am    Post subject: Reply with quote

ColinR wrote:
the difference between the two crossovers is the change between T52 SP1049 and SP1072 and associated target function calculation.


I always thought the 2 T52's were identical, the only difference being the square/circular with cut ends mounting plate?
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ColinR
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PostPosted: Thu Oct 22, 2009 1:31 pm    Post subject: Reply with quote

Quote:
I always thought the 2 T52's were identical



Letís see metal parts are different sizes and weights (are the coercivities?), the lead out wires are 60mm and 65mm apart so the domes are not interchangeable, one is built on a PCB the other on thin card, so I have always thought the opposite Very Happy .
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audiolabtower
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PostPosted: Thu Oct 22, 2009 2:14 pm    Post subject: Reply with quote

that's interesting, I asked the question of Kef years ago and they sent me both data sheets showing the printed specs were identical and told me the only difference was the mounting plate. The magnet specs are identical 10000gauss density and 50000maxwell total flux. How is a pcb used inside the drive unit, is it the coil former?
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T.O. Chef
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PostPosted: Thu Oct 22, 2009 6:49 pm    Post subject: Reply with quote

Hmmmm. Admittedly, I'm a bit confused now too. I seem to recall it being said that the extra iron around the SP1072 results in only a very small decrease in its sensitivity.
Does the construction of the SP1072 contribute other sonic variations over its predecessor too?
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speakerguru
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PostPosted: Fri Oct 23, 2009 8:17 am    Post subject: Reply with quote

ColinR wrote:
Letís see metal parts are different sizes and weights (are the coercivities?), the lead out wires are 60mm and 65mm apart so the domes are not interchangeable, one is built on a PCB the other on thin card, so I have always thought the opposite Very Happy .


I'm not sure about the 60 or 65mm difference. Maybe Colin is going back to the T15? That's a minor point anyway.

The SP1072 was a redesign, mostly to reduce cost. There was no intention to change the characteristics. The magent is identical except that the expensive deep drawn pot was replaced by a short tube and separate backplate. The Alnico slug remained the same. The SP1049 again had an expensive circlircular top plate with two cropped straight sides. The SP1072 used a plain flat square plate. I don't recall there being any change to the pcb mounted diaphragm assembly. In both caes it was fixed to the top plate with a thin double sided adhesive yellow tape. The SP1049 used an expensive machined recess on the top plate for voice coil location. The SP1072 used semi-shear pins in the top plate, copied from the T27 SP1032.
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ColinR
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PostPosted: Fri Oct 23, 2009 11:16 am    Post subject: Reply with quote

Quote:
I'm not sure about the 60 or 65mm difference. Maybe Colin is going back to the T15


No Very Happy .

Both T52s have an identical failure mode, which can first be identified by a "tizzyness" in the treble region.

What has occured due to a failure of the lacquer is a split in the voice coil which will propogate until eventual breakdown; it's spectacular in Meridian M2s.

Having carefully removed domes from these kinds of failures the following are extracts from my notes.


Quote:
the domes are not interchangeable


The lead out wires from the SP1049 voice coil emerge at 60 degrees before connecting with the blue and black wires (solder dimples 62mm apart) which pass through the faceplate 80mm apart.

The lead out wires of the SP1072 are connected to the PCB (it's green and etched) backing as are the black and blue wires which are soldered to short terminals in a different position 65mm apart.

These soldered joints (theyíre too long/deep) will foul a SP1049 faceplate even though itís milled out for the voice coil/lead out wire connection OR because the SP1072 faceplate's not milled out the soldered joint won't allow the dome to seat.

Rolling Eyes
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audiolabtower
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PostPosted: Fri Oct 23, 2009 7:06 pm    Post subject: Reply with quote

thanks for the clarification guys Smile , so the tweeters are interchangable as far as performance was concerned but obviously needed different flush mounting arrangements. So the early 105.2s had 1049s? and later ones 1072s without the series small inductor in the crossover (or maybe this was a select on printout depending on the measured drive unit)?

One more clarification of the diagram please - I assume the later crossover was 450uF total series caps, or was it 2x450 which would be quite a jump from the earlier total 480uF?

cheers Very Happy
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ColinR
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PostPosted: Fri Oct 23, 2009 8:33 pm    Post subject: Reply with quote

Quote:
was it 2x450


From my blueprint.

"C1 and C3 450uF 50V to make a combined total value of 900uF+/-5% see table G."


Although in the "Orphan bass modules and heads reunited - sort of" thread, Lee in Montreal's RHS crossover > SNo. 2966 has 4*120uF Shocked .


Always remember "design subject to modification" Very Happy .
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speakerguru
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PostPosted: Sat Oct 24, 2009 8:46 am    Post subject: Reply with quote

ColinR wrote:
...... OR because the SP1072 faceplate's not milled out the soldered joint won't allow the dome to seat.

That doesn't sound right. Weren't there two black plastic tubes to guide the wires through from front to back? Are you saying the solder blob could be so large that it didn't go down the tube? There was no possibility of misalignment because of the semi-shears.
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ColinR
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PostPosted: Sat Oct 24, 2009 9:51 am    Post subject: Reply with quote

Confused

The lined holes on the SP1072s are 57 mm apart.

Now the soldered joints on the SP1049 dome are side-to-side (in ths same plane as the faceplate), so the hole isn't big enough to locate them.

The SP1072 has metal lugs/rivets to which the lead out wires are soldered in an up-to-down (perpendicular to the faceplate) which fit into the lined holes.


The "bodgit" option of desoldering a SP1072 dome, filing down the metal stub and doing a new parallel joint for repairing a SP1049 OR making a new vertical soldered joint on a SP1049 dome to fix a SP1072 has never been investigated by me.
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audiolabtower
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PostPosted: Sat Oct 24, 2009 5:25 pm    Post subject: Reply with quote

ColinR wrote:
Quote:
was it 2x450


From my blueprint.

"C1 and C3 450uF 50V to make a combined total value of 900uF+/-5% see table G."



Thanks for the clarification Very Happy , your diagram was correct but I thought the difference might have been more in line with the other differences Smile Hmmm, seems quite a jump compared to the smaller variations in the other filters, those easily understood as either batch selection or manufacture variations over time.
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pfby
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PostPosted: Sun Feb 28, 2010 12:08 am    Post subject: Shy bass with Kef 105/II Reply with quote

Hi,
This is not a real reply - a little bit late I suppose - but rather a reflexion about what our friend named "a lack of bass" ... I have a pair of 105 from the beginning of the 80's (not 105 /II). I don't think there is an noticeable difference between these models.
I first used these speakers with a Sony pre+power amplifier (I can't remember the reference but it was at least rated 2x150 W). When this amp died, (no possibility to have it repaired) I wasn't able to buy another very good amplifier at hte moment. So I bought a Yamaha integrated AX 892 (rated 110 W per chanel). The result was sadly "standard" neither good nor bad...
Some years after, I bought a McIntosh power amp (2x270 W) used together with the Yamaha AX 892 preamp (this very model factory came with a strap between preamp out and power amp in).
It was "night and day" (more exactly, day and night...) A larger and deeper stereo image and more strong low frequencies.
Later, I bought a Mc preamplifier, and again, quality increased... more softness, more detail and very solid bass.
As a sound engineer, I have recorded many pipe organs, among them, in Paris, St-Eustache's, which has within its 100 stops - three 32' (one "reed" at the Pedal "Contretrombone", and another one in the Swell (rather unusual !) "Contrebasson"... At the Pedal as well at the Great Organ there is a mouth stop (real 32') 'called "Contrebasse" and "Flute".
I edit my recordings monitoring them with my 105 and I can assure you there is no loss in any part of the spectrum.
On the other hand, 105 "ne font pas de cadeau" this means they don't magnify the sound at all : if the recording is well-balanced, they sound good, but if there is something wrong, they sound quite "poor".
May be your problem only came from an amplifier not powerful enough to drive them correctly ? It might be easier to try a stronger amplifier rather than modifying filters...
Let me know...
Best regards
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proffski
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PostPosted: Sun Feb 28, 2010 1:51 am    Post subject: Re: Shy bass with Kef 105/II Reply with quote

Agreed!

Forget paper specs and 'average' listening power / volume go for an amplifier with grip & authority.

In order of my preference in the earlier days with KEF loudspeakers...

Krell, Amcron, Adcom. The differences are incredible yet on paper almost zero!

Oh, I once heard a monitoring session on early 105s being driven by professional Yamaha amplifiers at the Cheltenham Music Festival, amazing!
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Lee in Montreal
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PostPosted: Wed Mar 03, 2010 4:21 pm    Post subject: Reply with quote

One thing I noticed about the 105/2 is that it doesn't lack bass at very low frequencies, but the rolling bass (80-90Hz) is indeed sometimes missing. And I think it has to do with the crossover filtering it out. I came to this conclusion from when I had the other "foreign" filters in my FrankenKefs. The bass was way "rounder" while on a "real" 105/2, some of the bass you don't hear, you just feel.
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