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Kef 103.2- Where's the bass?

TellMeWhy

TellMeWhy

Active Member
Dear Friends,
My Kef 103.2 speakers sound good but I am underwhelmed by their limited bass response to the point where I guess something must be wrong. Bass needs to be turned up to 4 or 5 o-clock on the preamp dial to get anywhere near a balanced sound, even though both drivers are moving freely and seem to function fine.

Crossover caps look alright but haven’t been tested. I know at least one of the S-Stop protection units was bypassed by the previous owner due to a faulty cap, and have read that those circuits contain a 600uF in series with the woofer that helps to lower the cut-off frequency. If those circuits are bypassed might that be what’s going on? Might also recapping whole crossover board help? And is there anything I might be missing? I can’t imagine it makes much difference but the rubber grommets around the bass driver retaining screws had perished, and I removed them.

If anyone has any ideas of how to get these speakers working with a normal amount of bass I’d be very grateful for advice, as I’ve grown quite attached to their fine imaging, realism and gorgeous good looks. Or are these a very bass shy design best used with a subwoofer?

Thanks!
Jon
 
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I have had a couple of pairs of 103.2, they are wonderful speakers and not bass shy for their size. They obviously do not have the low end of full range floor standing models but they are balanced.

It would be worth having a look at the crossovers. They each contain a couple of small caps in the S-Stop circuit which were apparently under rated and they often fail.

Here is a post I made about having one of the pairs I sold to a friend repaired when one failed several years later:

http://www.audiokarma.org/forums/index.php?threads/kef-103-2-crossover-repair-help-needed.667167/

In this case failure muted the speaker, not sure if it would reduce bass response but they should be changed at some point anyway. Probably not a bad idea to restore the one that was modified.

Not sure what effect removing the grommets will have but I seem to recall Kef insisted they were important to the final sound.

Good luck, let us know how it goes.
 
Raynald said:
I have had a couple of pairs of 103.2, they are wonderful speakers and not bass shy for their size. They obviously do not have the low end of full range floor standing models but they are balanced.

It would be worth having a look at the crossovers. They each contain a couple of small caps in the S-Stop circuit which were apparently under rated and they often fail.

Here is a post I made about having one of the pairs I sold to a friend repaired when one failed several years later:

http://www.audiokarma.org/forums/index.php?threads/kef-103-2-crossover-repair-help-needed.667167/

In this case failure muted the speaker, not sure if it would reduce bass response but they should be changed at some point anyway. Probably not a bad idea to restore the one that was modified.

Not sure what effect removing the grommets will have but I seem to recall Kef insisted they were important to the final sound.

Good luck, let us know how it goes.
Click to expand...
Thanks Raynald. It could be the cap in the S-Stop. Or I wonder if the lack of rubber grommets on the bass driver is stopping a good seal from being made and therefore compromising the bass response?
 
That's very likely. simple check - grab a mono sound source (same music (not stereo) played into both channels and see if you have a solid center image and good bass also centered. If not and the image or bass seem diffuse and vague, just reverse one speakers' wire inputs and then try again. If the image is diffuse and the bass solid, or the other way around, then at least one of the woofers is wired wrong, or the internal connections are both wrong.
 
Otherwise, best to check the crossover and consider doing a recap. However, you might also swap the woofers and see if the problem changes with the woofers or the cabinets.
 
mech986 said:
Otherwise, best to check the crossover and consider doing a recap. However, you might also swap the woofers and see if the problem changes with the woofers or the cabinets.
Click to expand...
Thanks for the advice! Both speakers are equally bass shy and seem pretty balanced with a mono signal. I had thought that bad crossover caps normally resulted in poor clarity and highs but didn't realise bass response could be affected too. Also strange that both speakers have equal issues...
 
Probably will need pictures of the woofers with their labels on the back, plus pics of the crossovers and the mods done to them, then the wiring. Something is definitely amiss as the speakers were well known for decent bass response. Were they well sealed everywhere?
 
KEF makes a wonderful speaker. KEF could not do bass if their lives depended on it. The Brits, living in smallish homes that are often sharing walls do NOT DO BIG BASS sound. None of them; Harbeth, Spencer, Proac, KEF. The musical culture is not about bass reproduction. You want bass? Get an American speaker.
 
reddog48 said:
KEF makes a wonderful speaker. KEF could not do bass if their lives depended on it. The Brits, living in smallish homes that are often sharing walls do NOT DO BIG BASS sound. None of them; Harbeth, Spencer, Proac, KEF. The musical culture is not about bass reproduction. You want bass? Get an American speaker.
Click to expand...

Spoken like a true ignoramus:thumbsup:
 
Although the 103.2 is a small speaker with a single 8'' woofer,it should have a good,smooth and fairly deep bottom end. Do keep in mind that these were NOT intended to knock the crockery out of your kitchen cabinets! You will certainly have to move up the KEF food chain for that experience:rolleyes:

My thoughts are that something is amiss with the crossover networks.The manufacturer-installed 600 mfd (2x 300mfd?) caps that are in line with the woofers served two purposes: Low end roll-off and protection from dc offset or pure dc from failed amplifiers. When I had my 105/2's, these caps (3x 120mfd in this case) had seriously degraded,and the bottom end was almost gone.I bypassed them completely,which greatly improved the bottom end.
 
reddog48 said:
KEF makes a wonderful speaker. KEF could not do bass if their lives depended on it. The Brits, living in smallish homes that are often sharing walls do NOT DO BIG BASS sound. None of them; Harbeth, Spencer, Proac, KEF. The musical culture is not about bass reproduction. You want bass? Get an American speaker.
Click to expand...


Huh. Good to know. I wonder what IS coming out at the low end of my Epos speakers. I have been fooled all this time.
 
NAD80 said:
Found this on HIFILOUDSPEAKERS.INFO.http://www.hifiloudspeakers.info/Anatomy/Crossovers/103.2/SP1144103.2CrossoverIndex.html. Didn't know if Jon_Bawn needed a schematic of the crossover.
Click to expand...
arts said:
My thoughts are that something is amiss with the crossover networks.The manufacturer-installed 600 mfd (2x 300mfd?) caps that are in line with the woofers served two purposes: Low end roll-off and protection from dc offset or pure dc from failed amplifiers. When I had my 105/2's, these caps (3x 120mfd in this case) had seriously degraded,and the bottom end was almost gone.I bypassed them completely,which greatly improved the bottom end.
Click to expand...

Thanks guys that is helpful. I am gonna open them up these evening and check the wiring, visual inspection of caps and see what has been done with the S-Stop. Regarding the 2 x 300mfd, I had read this from another post but struggle to make sense of it:

"The 600uF in series with the woofer is essential for the correct operation of the protection circuit, but it also extends the low frequency response by its interaction with the inductance in the woofer equivalent circuit, due to the driver/box suspension. The cut-off frequency is reduced below the box resonance and the roll-off below cut-off is increased from the 12dB/oct of the closed box to 18db/oct, which is still less than a reflex design. There is an equivalent effect above resonance as the series inductance of the woofer crossover becomes large. The crossover inductor interacts with the capacitance due to the mass of the moving parts, which produces a peak in the response, with a corresponding drop in impedance, in the region above resonance. The only way to avoid this it to have impedance compensation networks across the woofer to make it look resistive."

That suggests to me that those 300mfd caps might be needed to extend the low end rather than roll it off. Either way, I guess that all parts of the crossover and S-Stop should be working properly for unit to function as it should do!
 
arts said:
Although the 103.2 is a small speaker with a single 8'' woofer,it should have a good,smooth and fairly deep bottom end. Do keep in mind that these were NOT intended to knock the crockery out of your kitchen cabinets! You will certainly have to move up the KEF food chain for that experience:rolleyes:

My thoughts are that something is amiss with the crossover networks.The manufacturer-installed 600 mfd (2x 300mfd?) caps that are in line with the woofers served two purposes: Low end roll-off and protection from dc offset or pure dc from failed amplifiers. When I had my 105/2's, these caps (3x 120mfd in this case) had seriously degraded,and the bottom end was almost gone.I bypassed them completely,which greatly improved the bottom end.
Click to expand...

Right, I've had a good check and the 2 x 300mfd are in line with the + input and they look good. After that the signal goes via a relay to a thick film package and onwards (see attached diagram and pics from one of my crossovers...). Not sure if the empty pin on the relay was ever meant to be attached?

Should I try bypassing the 2 x 300mfd?

Can you (or anyone else) see anything obviously wrong by the pics here?

Spade connectors to LED are badly corroded- should I detach them?

Is the relay the protection circuit or is there more to that than just the relay?

Thanks a lot!
Jon
 

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