Amplifier recommendations for vintage KEF 105.1

[fordiebianco]

Dear All,

I am the happy owner of a pair of recently restored (crossover, tweeters) KEF 105 Mark Ones. They are standing in a medium sized room (ca 16square meters), away from the walls, about 3 meters away from my listening position. I mainly listen to Jazz, symphonic and chamber music, and quite a bit of what you would have called in the eighties 'New Jazz', but not particularly loud, because I quite like my neighbours.

I have a few chip amps amps (Allo Volt D+, Aiyima A07, etc), a few 'classic' but underpowered vintage receivers from the 70s (which I keep for the looks only), and a typical 80s 'big iron' Denon Power Amp (the SM-80: 100 w into 8 ohm per channel).

To remind you of the specs of the KEFs:

• Size: 965 x 415 x 455 mm (38 x 16.3 x 17.9 inches)
• Input Impedance: 8 ohms
• Rated maximum power: 200W programme
• Amplifier Requirements: 40-200 watts per channel into 8 ohms
• Frequency response: 38-22,000Hz +/-2dB at 2m on measuring axis
• Sensitivity: 86dB at 1m for 1W, anechoic conditions
• Crossover Frequencies: 400, 2500Hz

In your learned opinion, what is a reasonable amplifier's power output for these speakers? Am I ok with my 20-50w classic receivers (even though they might not have the THD of the Volt D+) or do they need something beefier, even for my moderate listening levels?

Many thanks for helping,

FB

 

[DanielT]

You have Sensitivity: 86dB at 1m for 1W ,.

It's probably not so stupid to have enough power so the amplifier can handle transistent peaks. I had probably invested in hm at least 250 W. Plus an amplifier that really has those fat bass modules in iron grip. BUT it depends on the type of music you play. If you play music that is compressed, it places less demands on the amplifier.

The red tops are the reason, among other things, why it is good to have much effect. Even at normal listening volume, it requires the amplifier to handle them in a good way. Otherwise, push the amplifier into clipping. An amplifier that clips sounds really bad.

Here is a video from a DIY Vintage fair I was at. The video does not do justice to how it sounded IRL but it does give an indication of what a capable rig that is not driven into clipping, or begins to show distortion can perform. It was all seriously completely incomparable.

Please note I am not an expert. Recommendations are more of a guess. A good rule of thumb now that pure many watts can be obtained for relatively little money, invest in getting space, headroom, lots off W. Then after that you should think about fixing even more headroom / effect.

You who like vintage. here some vintage porn. KEF is included, Björn's DIY

Hifi Vintage DIY fair with pictures

I visited this fair yesterday! DIY & Vintage meeting in Mölnlycke Here is a short report. When: 6 November 2021 Where: Country: Sweden City: Gothenburg I took pictures myself BUT most were so damn blurred so I borrow pictures from this thread, taken by other participants. Pictures taken from...

audiosciencereview.com

 

[fordiebianco]

Hi @DanielT

many thanks for your kind help and explanation. Definitely not listening to very compressed music. I might have to rethink my approach to amplifiers and get two beefy mono stages.

...and thank you for the cool pics. Looked like an amazing day out.

FB

 

[DanielT]

At least I would have done that if I were in your place. Too much or too little power 250 W I do not know but as I said better too much than too little.

Hope someone else gives you tips and advice. It based on your condition had been interesting to read about. I'm not that experienced so I will follow your thread with interest.

I think it's fun and interesting with vintage. Also sound and radio history. Tips on opportunity are available visit a radio museum.Nearby where you live.

Radiomuseet i Göteborg | Det kompletta radiomuseet

wordpress.radiomuseet.se

I think you can, for example, in the main system can have modern stuff. Sharp Hypex based amplifier for example. Then in the secondary system have vintage. In the bedroom, hobby room, garage for example. Then the vintage looks nice (of course the taste is like the butt, divided, but still).

You have nice speakers, by the way.

 

[Willem]

It is only a small room, so I would think your 2x100 watt Denon will do the job. If you want to spend money, I would go for a big Hypex stereo model. Monoblocks are unecessary in a room like this.

 

[DanielT]

It is only a small room, so I would think your 2x100 watt Denon will do the job. If you want to spend money, I would go for a big Hypex stereo model. Monoblocks are unecessary in a room like this.

Aha, about 16square meters), away..Sorry I missed that.

Is there no calculator regarding at least getting a clue on the appropriate effect?
I know, because I mentioned it earlier, that it depends on a lot of factors but still. It would have been fun to test such a calculator.

Edit

Fordiebianco you will not like this considering your new passive filters, but I throw up the idea anyway. Powerful class d amplifier that drives the bass modules, another amplifier that drives the top speakers.

Then you need to split the signal from your source into two different amplifiers and either run an active analog filter or set the filter in the digital world.

EQ and bass modules / subwoofers are a happy marriage. In case you want to freshen up and get a smoother frequency curve in the lowest frequency registers.

This one for your bass modules should fix it well. I think.Good price on it too.

Conclusions
The Behringer A800 does what pro amps try to do: provide solid, middle-of-the-road distortion and noise with tons of power in quiet and light package for little money. The design is stable and better than the A500. As such, I can recommend the A800 as an everyday amplifier.

Behringer A800 Stereo Amplifier Review

This is a review and detailed measurements of the Behringer A800 Class D Stereo Amplifier. It is on kind loan from a member. The A800 costs US $299 including free shipping from multiple sites. The member who loaned it me has done a youtube video of it which you can see by clicking on this...

audiosciencereview.com

Are these your model of Kef speakers?

 

[fordiebianco]

Hi Daniel,

not quite. Mine are (not quite as well preserved) like these:

 

[fordiebianco]

It is only a small room, so I would think your 2x100 watt Denon will do the job. If you want to spend money, I would go for a big Hypex stereo model. Monoblocks are unecessary in a room like this.

Many thanks @Willem . I will get the Denon out of storage and schlepp it downstairs and give it another whirl. In the meantime I have ordered one of the TPA3255-A based chipamps with alleged 2x150W into 8 Ohm. See how that pans out.

 

[DanielT]

Hi Daniel,

not quite. Mine are (not quite as well preserved) like these:

View attachment 166839

Those goodies are worth a good amplifier.

 

[Keauval]

Many thanks @Willem . I will get the Denon out of storage and schlepp it downstairs and give it another whirl. In the meantime I have ordered one of the TPA3255-A based chipamps with alleged 2x150W into 8 Ohm. See how that pans out.

Hi

Sorry to dig up this topic but having just bought these same speakers, I'm in turn looking for an amp to drive them.
I ordered a Fosi V3 Mono (120WPC) but I have the impression that it will be light considering the size of my room (45m2) and the listening distance.
Do you have any recommendations?

Thank you!

 

[sergeauckland]

Hi

Sorry to dig up this topic but having just bought these same speakers, I'm in turn looking for an amp to drive them.
I ordered a Fosi V3 Mono (120WPC) but I have the impression that it will be light considering the size of my room (45m2) and the listening distance.
Do you have any recommendations?

Thank you!

If you want to preserve historic appropriateness, these were often driven by Quad 405s at the time. Apart from that, any amplifier of around 100 watts will do fine.

S.

 

[fordiebianco]

Hi

Sorry to dig up this topic but having just bought these same speakers, I'm in turn looking for an amp to drive them.
I ordered a Fosi V3 Mono (120WPC) but I have the impression that it will be light considering the size of my room (45m2) and the listening distance.
Do you have any recommendations?

Thank you!

The Fosi didn't have any issue with the KEFs, and the the two Fosi Monos will do fine. Enjoy!

 

[Timcognito]

Modern tech with period appropriate look, great test results, DAC and phono preamp.

Yamaha A-S701 Stereo Amplifier Review

This is a review and detailed measurements of the Yamaha A-S701 stereo integrated amplifier with included DAC and Phono stage. It is on kind loan from a member and costs US $800. The A-S701 is one of the best looking amplifiers I have tested. Yes the controls are plastic unlike the glory days...

www.audiosciencereview.com

 

[momato]

Dear all
I also just got these. Will be restoring first, but would like to plan my amplifier needs.
I have different stuff:
Luxman L-430 integrated with pre out, 105 WPC
NAD C275BEE power amp 150 WPC with variable input
NAD 2200PE power amp, >200 WPC, no variable input
NAD 1300 & 1000 preamps.

I like the Luxman. Pretty and sounds good. Was thinking to couple it with a power amp and bi-amp the speakers, as they already have the crossovers separate from each other. So that the power amp handles the bass units. And the power amp with variable input should handle any input sensitivity differences - or?
What am I missing? Why do people say I “need” an active cross-over? Below is ChatGPT answer to this question. Seems to me the setup was intended for this exact use case?
Thanks for any input

From ChatGPT:
The KEF 105.1 speakers were designed for passive bi-amping, meaning that they are equipped with passive crossovers to divide the frequency bands between the drivers. KEF designed the 105.1 speakers to be used with passive bi-amping configurations, where separate amplifier channels are used for the bass and mid/treble sections, each driven through the passive crossover network built into the speaker.

While using the built-in passive crossover for bi-amping is the intended and typical configuration for the KEF 105.1 speakers, there are scenarios in which an active crossover might be considered, including:

1. Customization: If you have specific preferences for crossover points and slopes that differ from the built-in passive crossover, an active crossover can provide the flexibility to tailor the frequency response to your preferences.
2. Driver Matching: If you are using different amplifiers with significantly differing gain or power output, an active crossover can provide more precise control over the frequency bands to ensure balanced power delivery to each section of the speaker.
3. Room Acoustics: In situations where room acoustics present challenges, an active crossover can help address specific room-related frequency response issues, allowing for more precise correction of peaks and nulls in the frequency spectrum.

 

[sergeauckland]

What bollocks!
Firstly, the 105 was never fitted with dual input sockets, as the crossover wasn't split.

Secondly, the crossover is integral to the loudspeaker and isn't available externally without taking the 'speaker apart, so turning it active isn't an option without a great deal of DIY.

I don't know why anyone would ever ask anything of Chat GPT, as it seems to get so much wrong, so can't be trusted with any answers.

S.

 

[momato]

What bollocks!
Firstly, the 105 was never fitted with dual input sockets, as the crossover wasn't split.

Secondly, the crossover is integral to the loudspeaker and isn't available externally without taking the 'speaker apart, so turning it active isn't an option without a great deal of DIY.

I don't know why anyone would ever ask anything of Chat GPT, as it seems to get so much wrong, so can't be trusted with any answers.

S.

Hmm.
My version 105.1 (SP1059) is definitely factory built with the crossovers split.
And a separate input socket directly on the
midrange/tweeter box.

And to add: I never mentioned making the current crossover active.

 

[sergeauckland]

Hmm.
My version 105.1 (SP1059) is definitely factory built with the crossovers split.
And a separate input socket directly on the
midrange/tweeter box.

And to add: I never mentioned making the crossover active.

No, you didn't, but GPT did.

As to the 105.1 crossover, be careful as to those connections. I think that the input connections are on the head, but the crossover is all in the head, so the connections going to the bass bin is after the crossover, not before. I may be wrong on this as it's a long time since I say a pair of 105s, but at that time, split crossovers and biamping was definitely not a thing, and at that time very few if any manufacturers did it. Certainly the KEF 105.2 only had a single pair of inputs, as did the later 104.2.

Regardless, passive biamping is a total technical nonsense, so pointless.

S.

 

[momato]

The cross

No, you didn't, but GPT did.

As to the 105.1 crossover, be careful as to those connections. I think that the input connections are on the head, but the crossover is all in the head, so the connections going to the bass bin is after the crossover, not before. I may be wrong on this as it's a long time since I say a pair of 105s, but at that time, split crossovers and biamping was definitely not a thing, and at that time very few if any manufacturers did it. Certainly the KEF 105.2 only had a single pair of inputs, as did the later 104.2.

Regardless, passive biamping is a total technical nonsense, so pointless.

S.

No. It did not. It mentioned using an active crossover INSTEAD.

Nevertheless….

The crossover for the bass is in the bass cabinet and for the midrange/tweeter in the top box. And separate terminals.
So no bullocks here…

Why is passive biamping technical nonsense? You reserve the power of one amp to parts of the speaker.
In my case, a “weak” integrated might drive the top range and then be supported by a stronger power amp for the more power hungry bass units.

 

[sergeauckland]

The cross

No. It did not. It mentioned using an active crossover INSTEAD.

Nevertheless….

The crossover for the bass is in the bass cabinet and for the midrange/tweeter in the top box. And separate terminals.
So no bullocks here…

Why is passive biamping technical nonsense? You reserve the power of one amp to parts of the speaker.
In my case, a “weak” integrated might drive the top range and then be supported by a stronger power amp for the more power hungry bass units.

Because of the Superposition Principle.

S.

 

[DSJR]

If you want to preserve historic appropriateness, these were often driven by Quad 405s at the time. Apart from that, any amplifier of around 100 watts will do fine.

S.

405?

We were a higher end dealer and, just before we staff asked Naim and Linn to get their claws into us, the Crown D-150A drove them superbly.

Today and assuming the crossovers and drivers haven't drifted off as I gather they can (wasn't there a HiFi news test of a vintage pair compared to test results of a new set?), any decent 100WPC+ amp should do well, the modern class D types available now for well under £/$1000 a perfect choice I'd suggest.