KEF 103/4's and Amplifier sizing

[Buanadha]

HI Everyone and thanks to earlier posters for great info on these speakers.

I've found a pair that I was unfortunately, unable to test out ahead of time (good deal and decided to roll the dice). While they are supposed to be working, I'm assuming from the earlier posts that I"ll have to have them in for some work to get them into a restored shape. We'll see how they look, though.

In the near term, I'm thinking more about what I need for an amplifier for them. I have some options, but am not sure just how much juice I need. Pretty much all are NAD and mostly old, though:

- 3240 - 40 watts
- 7150 - 50 watts
- 7100 - 60 watts
- t773 - 110 watts per channel. An AV amp, but has nice audio performance also

I have some spare amps I could use as well if I need to be creative. I'm thinking I'll try the 7100 first, but not sure it's optimal. What do others think of the 103/4's and what I should be using to drive them?

thank you in advance

 

[SuperAvilyn]

Hello Buanadha,

I am the owner of a pair of 103/4s and I'm driving them with a NAD C356BEE amp that I bought last year to replace a NAD C350. Both amplifiers have/had no problems whatsoever with the KEFs. The C350 had 2x60w and the C356BEE is 2x80w. I don't hear any difference between the two, frankly, except that the old C350 developed some problems due to ageing. This may have been easy to fix, but as I found an end-of-line 356 for a steal, I went for that.

The 103/4s are now in very good condition, but they have had their problems in the past. First, the foam surrounds of the internal woofers had been replaced by a previous owner, but they weren't centered well, so the voice coils rubbed resulting a strange noises and a lack of bass. I've had this rectified by a professional and the bass is really good now. Please note that the bass will never be devastating, exaggerated or overwhelming, it is just accurate and natural. But if there's a lot of deep bass in the music, you'll definitely hear it. That is a very good thing as I hate exaggerated, unnatural bass.

Then, the previous owner had had the tweeters filled with new ferrofluid (this may be necessary after all these years, when the treble becomes weak due to the fluid drying out) and the caps on the filters were replaced. This is all good, but upon reassembly, something must have gone wrong, as one tweeter was out of phase relative to the mid-unit. I knew that something was not right but I couldn't find what it was, one speaker had weaker treble/higher mids than the other, I even went as far as opening one speaker to replace the ferrofluid (again) which was not necessary with hindsight (I wrote about this in another thread). After correcting the phase - it turned out to be the wiring of the mid speaker, not the tweeter - all was good. When tweeter and mid are out of phase, they can cancel out each other in certain take-over frequencies, which causes the muddy sound. But it has taken me a very long time to find out what was wrong.

The speakers are now really singing. After all these problems, it took me a long time to come to trust and to fully appreciate the KEFs. They're now as they should be, at last, and I'm now just enjoying the music rather than listening for faults. These are definitely no easy speakers to work on - everything is concealed inside, it is not possible to take out any unit, whether woofer, mid or tweeter, from the outside. And the crossover filters are very big and complicated twin-level affairs. But once the speakers are good, and they are, they sound great. I mainly listen to classical (orchestral and chamber music) and jazz. The sound is very precise, natural and spacious, but there's also some good punch and rhythm. There's a lot of fun to be had.

I think the NAD 7100 should do fine. The KEFs are 4 ohm, but they're not that difficult to drive.
I hope that your 103/4s will be in a good shape. If not, it is worthwhile to take them to a good professional, they're worth it in most cases. You won't find new speakers this good below €3000/$3500.

 

[Pyrrho]

SuperAvilyn's experience with previous work on speakers illustrates why I prefer buying used equipment that has not been "restored" by someone else. Too many people bungle it, and it is often a lot harder to find and fix the newly created problems than to deal with any original problems. It is also why, if I sell something, I do not do any restoration work that is not necessary for it to function (other than purely cosmetic things, like dealing with scratches on the cabinet), so the person buying it can decide for themselves what they want to change and what they want to leave alone.

As for the KEF speakers, KEF has made a lot of great speakers, particularly among their higher lines. Your Reference series speakers should sound great, if operating properly. Here is some information on them:

https://us.kef.com/explore-kef/kef-museum/1990s/reference-series-model-1034-1992-95

As for power needed, that is something that no one is going to be able to tell you. The reason is, it depends on how loud you want to play your music, the particular music you play, how far you will be from the speakers when listening, and the acoustics of your room. We are not going to know all of that with anything close to the precision necessary to make such a determination. (That is also why the manufacturer gives a wide range for their recommendation; as you can see at the link above, they recommend 50-200 watts into 4 ohms. 50 watts may be all you need, or maybe not, depending on all of the things mentioned above.)

When selecting an amplifier to use with the speakers, make sure you look at 4 ohm RMS continuous output ratings; what the amplifier does into 8 ohms can be ignored. And you can ignore any "peak" ratings as well.

I would probably try out the NAD 7100 with the speakers, just as you are planning on doing.

If everything is functioning properly, it should sound really good.

 

[SaSi]

I would recommend you to use as high powered an amplifier as you can find. The speakers are rated for 200W and their band pass low frequency section can take a lot of power. By using a 200 or 300W amplifier, listening at your normal listening levels, you will enjoy a large headroom allowing the dynamics of the music to be properly replayed. I have had that revelation using a pair of KEF 107. I was using a 90W/4Ohms amplifier and they sounded impressive. Since I put a dbx BX3 MkII amplifier that delivers more then 450W in the system, I can't stop listening to them. And it's not only at normal loud levels that the difference is apparent.

 

[Buanadha]

SuperAvilyn,

Thank you for the very helpful response and really happy to hear you got them to where you wanted them!

I have to admit that I am worried about the condition of the speakers. I'm hopeful that they are suffering more from benign neglect than from someone trying to fix them (and damaging them!). They look more like they were sitting in storage than were actively used recently. I did reach out to a local Chicago repair shop and their first comment was to say that I needed to make sure they hadn't been tampered with. They did say that they work on them, though, and I'm tempted to not even plug them in and play them, but to just drop them off for a rehab prior to risking damage by playing if they aren't in good condition yet.

I got them for a very good price so that even if they need work, I can invest up front to make sure they sound the way they should.

I think your listening style mirrors mine, which is why I like the KEFs. I like precise and clear base rather than exaggerated and also listen to a lot of classical and jazz. Something really nice about the NAD/KEF combination, IMO, for that kind of listening

 

[Buanadha]

SuperAvilyn's experience with previous work on speakers illustrates why I prefer buying used equipment that has not been "restored" by someone else. Too many people bungle it, and it is often a lot harder to find and fix the newly created problems than to deal with any original problems. It is also why, if I sell something, I do not do any restoration work that is not necessary for it to function (other than purely cosmetic things, like dealing with scratches on the cabinet), so the person buying it can decide for themselves what they want to change and what they want to leave alone.

As for the KEF speakers, KEF has made a lot of great speakers, particularly among their higher lines. Your Reference series speakers should sound great, if operating properly. Here is some information on them:

https://us.kef.com/explore-kef/kef-museum/1990s/reference-series-model-1034-1992-95

As for power needed, that is something that no one is going to be able to tell you. The reason is, it depends on how loud you want to play your music, the particular music you play, how far you will be from the speakers when listening, and the acoustics of your room. We are not going to know all of that with anything close to the precision necessary to make such a determination. (That is also why the manufacturer gives a wide range for their recommendation; as you can see at the link above, they recommend 50-200 watts into 4 ohms. 50 watts may be all you need, or maybe not, depending on all of the things mentioned above.)

When selecting an amplifier to use with the speakers, make sure you look at 4 ohm RMS continuous output ratings; what the amplifier does into 8 ohms can be ignored. And you can ignore any "peak" ratings as well.

I would probably try out the NAD 7100 with the speakers, just as you are planning on doing.

If everything is functioning properly, it should sound really good.

It's funny that was the first thing the Stereo repair shop said when I asked them about the Kef 103/4's. He was very emphatic -- Make sure nobody's tampered with them! I'm holding out hope that they're just stock and need regular fix and repairs and not rework to fix something broken by the previous fix.

I'm hopeful the 7100 will work for me. My listening levels aren't super high, I rarely have my amp's up above 30% even in our basement listening area where I won't torment the neighbors.

 

[Pyrrho]

It's funny that was the first thing the Stereo repair shop said when I asked them about the Kef 103/4's. He was very emphatic -- Make sure nobody's tampered with them! I'm holding out hope that they're just stock and need regular fix and repairs and not rework to fix something broken by the previous fix.
...

I am guessing that he has seen things bungled, too. Probably a lot more than I have, as it is not my profession to repair audio gear.

People can make something that would have been a relatively easy fix and make it into something that is practically impossible to fix. This can dramatically affect how much it costs to get it working again, or whether it is worthwhile to get it working again.

I hope that yours have not been ruined, and will soon be playing beautiful music. It is a shame when someone wrecks something as nice as those speakers.

 

[Buanadha]

I would recommend you to use as high powered an amplifier as you can find. The speakers are rated for 200W and their band pass low frequency section can take a lot of power. By using a 200 or 300W amplifier, listening at your normal listening levels, you will enjoy a large headroom allowing the dynamics of the music to be properly replayed. I have had that revelation using a pair of KEF 107. I was using a 90W/4Ohms amplifier and they sounded impressive. Since I put a dbx BX3 MkII amplifier that delivers more then 450W in the system, I can't stop listening to them. And it's not only at normal loud levels that the difference is apparent.

I'm hoping the NAD 7100 has enough headroom for me to enjoy them. The rooms they could end up in aren't huge, although one has 10+ ft ceilings, and I'm typically not turning my amps up past 30% very often, but I see your point about having the headroom to allow the music to be replayed the way it deserves.

I do have some options if the 7100 isn't sufficient. A t773 that has 110W across channels and I could potentially be creative with splitting channels on that as it has a lot of flexibility on how I use them (I can remove jumper cables in the back and make it a dedicated amp - although I haven't experimented much with it so far). I also have a second 7100 and a 3240/7240 that I could maybe use to combine two amps with the speakers.

These will be the nicest speaker's I've had, so just hoping to get a good pairing for them.

 

[SuperAvilyn]

So fingers crossed then! Even if the speakers would require a major overhaul, you would probably be looking for a few hundred $ maximum (worst case), since you wrote you could acquire them very cheap. For that same money, you would never find a new speaker that is anywhere near as good as these, once yours are brought back to perfect condition again. It will always be a good deal .

Typically, with an older 103/4, you could expect that the 4 foam surrounds of the internal woofers will need replacing, the ferrofluid in the tweeters may need to be changed and the crossovers could use some new capacitors here and there.
Nothing dramatic in itself, but due to the complex construction it is time-consuming. But those guys at the repair workshop will have the experience to do that much quicker than a guy like me, who has 'two left hands'. Please keep us informed!

 

[Buanadha]

So fingers crossed then! Even if the speakers would require a major overhaul, you would probably be looking for a few hundred $ maximum (worst case), since you wrote you could acquire them very cheap. For that same money, you would never find a new speaker that is anywhere near as good as these, once yours are brought back to perfect condition again. It will always be a good deal .

Typically, with an older 103/4, you could expect that the 4 foam surrounds of the internal woofers will need replacing, the ferrofluid in the tweeters may need to be changed and the crossovers could use some new capacitors here and there.
Nothing dramatic in itself, but due to the complex construction it is time-consuming. But those guys at the repair workshop will have the experience to do that much quicker than a guy like me, who has 'two left hands'. Please keep us informed!

OK, so they got here. The guy had 4 for sale, and because I was having to arrange someone on uShip to lug them back from New Jersey to Chicago, I ended up making an offer for all 4 and got them.

On a positive note they appear to be in much better shape than I expected and likely spent a long bit of time in storage instead of being beaten up. They aren't mint and have some scuffs, but they definitely don't look abused, or even used hard. Nor is there any sign that they were tampered with by the previous owners.

While I should have just taken them to the shop, I couldn't stop myself from listening to them and trying a few different types of music and amps.

I was probably overly worried about enough amps. I've run it in the NAD 7100 and it seemed to handle the speakers (although the room has lower ceilings and is a smaller capacity space despite being pretty open) with the volume hitting 80-90 decibels pretty easily and that's a bit above where I normally listen. I also ran tested them with a NAD 7240 and they seemed to do well with that also although that took more effort and I didn't like the output as much as with the 7100. I didn't push either amp past half-way, though.

The good news, they sound really, really good. I have no doubt that given their age they can use professional maintenance to make sure they're running the right way and are safe from me playing them, but I love the sound. I've always liked KEF's sound, but this is better than anything I've had before even at this age and level of maintenance. I am imagining they'll even sound a lot better once I get the rest of the system dialed in better.

The bad news, there's a very rarely appearing buzz from two of the four speakers (start of Dvorak's 9th, Largo, for instance), but otherwise doesn't appear. i tried switching amps, but it still is appearing. But either way, I'm not put out, I was pretty sure I needed to take them all in for the maintenance you mentioned (thanks for that!), so that's what I'm doing with one pair this weekend.

 

[Buanadha]

2020-09-05 22.02.48

• Buanadha
• Sep 6, 2020

 

[Buanadha]

2020-09-05 22.01.19

• Buanadha
• Sep 6, 2020

2020-09-05 21.56.25

• Buanadha
• Sep 6, 2020

2020-09-05 21.53.32

• Buanadha
• Sep 6, 2020

2020-09-05 21.52.59

• Buanadha
• Sep 6, 2020

OK, trying again to post the pictures here. Of the 4, I only saw 1 of the foams with some level of cracking in them. I'm not experienced at looking at these. They sound good.

What do people think - should I take this in the re-foam as a preventative measure? Or do they look ok to continue playing for now?

thanks!

 

[BilboBaggins]

Get them all done while they are in the shop. Nothing worse than getting something fixed only to be done again within the year because you didn’t do the proactive parts.

 

[slimecity]

Agree - get the refoam sorted.

Re-fluid the tweeters at some stage too, it pays off.

As these speakers are biwirable - depending on the size of your room - you can run pretty much anything you like into the mid/tweeter section.

I have mine in a small bedroom and only bi-amp them. I'd recommend that you do the same. I run anything 40W plus into the bass section and run the mid/tweeter section with a wide range of low power amps with no issue, down to 8-10W tube and VFET homebrew amps.

You could use your NAD to power the bass section, and try something like a TPA3116 50WPC amp on the mid/tweeter section. I reckon that would sound great.

They sound lovely and are easily my fave speaker.

 

[Buanadha]

Get them all done while they are in the shop. Nothing worse than getting something fixed only to be done again within the year because you didn’t do the proactive parts.

I haven't even taken them to the shop yet, they sound so great and look to be in good shape, but I think you're right... I'll take them to the shop 2 at a time and get the full update done so I don't risk damaging them!

 

[Buanadha]

Agree - get the refoam sorted.

Re-fluid the tweeters at some stage too, it pays off.

As these speakers are biwirable - depending on the size of your room - you can run pretty much anything you like into the mid/tweeter section.

I have mine in a small bedroom and only bi-amp them. I'd recommend that you do the same. I run anything 40W plus into the bass section and run the mid/tweeter section with a wide range of low power amps with no issue, down to 8-10W tube and VFET homebrew amps.

You could use your NAD to power the bass section, and try something like a TPA3116 50WPC amp on the mid/tweeter section. I reckon that would sound great.

They sound lovely and are easily my fave speaker.

I haven't even done anything special with them and I love the sound already. I have one set in a basement that is fairly big about 15' x 20', but with fairly low ceilings so the volume gets pretty high. I have a second set in the living room which is about the same size, but with 10'+ ceilings so it takes a bit more to raise the volume in that room. I really like the idea of bi-wiring these speakers. I imagine a tube amp would make the highs just beautiful.

Time to separate from one set for a while and get the full service done at the shop, though!

 

[viennadad]

HI Everyone and thanks to earlier posters for great info on these speakers.

I've found a pair that I was unfortunately, unable to test out ahead of time (good deal and decided to roll the dice). While they are supposed to be working, I'm assuming from the earlier posts that I"ll have to have them in for some work to get them into a restored shape. We'll see how they look, though.

In the near term, I'm thinking more about what I need for an amplifier for them. I have some options, but am not sure just how much juice I need. Pretty much all are NAD and mostly old, though:

- 3240 - 40 watts
- 7150 - 50 watts
- 7100 - 60 watts
- t773 - 110 watts per channel. An AV amp, but has nice audio performance also

I have some spare amps I could use as well if I need to be creative. I'm thinking I'll try the 7100 first, but not sure it's optimal. What do others think of the 103/4's and what I should be using to drive them?

thank you in advance

 

[viennadad]

I have run mine with a 130 wpc Carver receiver, a 100 wpc NAD 2200 PE, and a 75 wpc Sansui G5700. All 3 were more than enough to get them as clear and loud as I needed.

HI Everyone and thanks to earlier posters for great info on these speakers.

I've found a pair that I was unfortunately, unable to test out ahead of time (good deal and decided to roll the dice). While they are supposed to be working, I'm assuming from the earlier posts that I"ll have to have them in for some work to get them into a restored shape. We'll see how they look, though.

In the near term, I'm thinking more about what I need for an amplifier for them. I have some options, but am not sure just how much juice I need. Pretty much all are NAD and mostly old, though:

- 3240 - 40 watts
- 7150 - 50 watts
- 7100 - 60 watts
- t773 - 110 watts per channel. An AV amp, but has nice audio performance also

I have some spare amps I could use as well if I need to be creative. I'm thinking I'll try the 7100 first, but not sure it's optimal. What do others think of the 103/4's and what I should be using to drive them?

thank you in advance

 

[SuperAvilyn]

Congrats! Looks good! And good to hear that you like the sound! These are wonderful speakers indeed.
Yes, there are some cracks visible in the foam surround, but that was to be expected after all those years. For the rest, the speakers look surprisingly tidy inside, clearly not messed with.
I would indeed recommend to have the surrounds replaced. They may look relatively OK, but now that the speakers are back in use, the dried-out foam will likely deteriorate quickly.

As to the tweeters: if they still sound crisp and clear, and if there are no audible differences between the left and right speaker, it may not be necessary to replace the fluid yet. It is a tough job to take the entire Uni-Q mid/high units out (it can only be done from the inside), remove the tweeters from the centre of the Uni-Q (can only be done from the rear of this 'contraption', pushing it out through the MF magnet) and especially to put everything back together. I've been through that and wouldn't want to do it again. Of course, the guys at the repair shop can do that much quicker than me, but it will always be labour-intensive, so if the tweeters are still OK, you may want to skip this job. Or you could see what the workshop recommends.

 

[Buanadha]

I got the first set back yesterday! It wasn't super cheap, but I wanted a pro who would take care of them the right way and took them to Stereo Rehab here in Chicago. I didn't have a chance to ask him about everything he had to do, but I got them set up and they just sound great.

My quick listen makes me think the Bass is tighter and more extended. Some of the highs seem cleaner and more rich as well. I set them up where I've been running my KEF Q70's that I like, but to my ears the 103/4's exceed them. Was Marantz CC4001 > NAD 7100 (functioning as Preamp) > NAD C352 Amplifier > to the 103/4's.

Checked out some Sonny Rollins, Dave Brubeck, Rebecca Pidgeon, Holly Cole, Cecilia Bartoli, Mozart violin concertos, Dvorak's 9th and some pop/rock as well. Went through all of them with beautifully and I thought I heard some things I hadn't noticed before (probably just biased, attentive listening on my part, though...). As others said, I wouldn't be able to touch this level of speaker for anything near the amount of money I put into them.

Have to take the second pair over, but dropped off an NAD 1700 (that or a 1600 will take the spot of the 7100 above) with the shop to have it cleaned up and brought back up to spec first.

Thanks to everyone for the advice and feedback in the thread. Your help is very much appreciated!