KEF C55 + Topping TP32 - Unimpressed, what's wrong?

[maravillo]

Hi guys,

I recently got a new Topping TP32 (TA2024B) at 15WPC @ 4ohm amp and purchased some used KEF C55 (4ohm, 8" woofer) I am not very happy with the combination.

I tried USB DAC or analog inputs on the amp and it doesn't get very loud. At listenable volumes it really lacks any depth. It is mostly high-mids and highs but there is little to no bass. The sound you hear is very well defined and clear and the speakers look great.

I have very limited previous experience on decent gear, but my previous setup sounded WAY better, but unfortunately is in another country. Old setup: Panasonic XR55 with Odyssey audio Epiphony I speakers (8ohm, 89db, 5" woofer).

Is this a problem of the amp driving the speakers poorly and not being able to get them vibrating fully, even at low volumes? Are the C55's really known for such poor bass? Should I sell the speakers, get a more powerful amp or get a subwoofer?

This forum is a great resource. Hope to get some feedback from you.

Felipe

 

[wmgwizard]

I found the C55 to require a bit of power for them to "wake up"

Low power/ low volume is not one of their strong points.

They don't have to be driven to ear splitting volume but something closer to 50wpc should do the trick.

The lack of bass at low volume is mostly because of the large passive radiator. You need to get the air in the cabinet moving before the bass shows up.

Mids and highs are good to excellent and the imaging is hard to beat. Try them on a set of taller stands so the lower speaker with the tweeter is close to SAE level when you are in your listening position.

 

[Poultrygeist]

I have the Topping TP21 which needs high efficiency speakers to sound good. The speakers I've used it with are 93 dbs and above.

T-amp power ratings can be misleading. My Dayton is rated at 50 watts into 4 ohms but it's probably no more than 20.

 

[maravillo]

Thanks you both the good input.

I will try to couple the speakers with a more powerful amp to see the difference but wmgwizard's point of the speakers needing enough power to get the passive resonators moving is a big concern. At the moment I can't use higher volumes or even what I think is 'normal' listening levels.

Would I need a different speaker for full range at lower volumes? (assuming it is driven by a more powerful amp) or would it be better to keep them and add a subwoofer.

 

[wmgwizard]

Tough choice.

Bass requires the excitation of larger volumes of air than mids or highs do.

Adding a passive subwoofer probably won't help. The low power you are using now will be divided between the sub and your mains.

Adding an active sub is also adding more power, just in a restricted frequency range.

If your system is already too loud for your space an active sub will almost certainly annoy the neighbors as low frequencies have longer wavelengths and thus travel farther. Right to your sensitive neighbor.

Perhaps a system designed as a sub/sattelite like Boston Acoustics Sub/Sat 6 or similar may be your best bet.

 

[adam-ads]

Make sure you have them both wired with the same polarity.

There's a chance that someone miswired them internally, either at the factory or during a repair.

 

[sreten]

Hi,

A passive radiator does not need "enough" power to "get it moving".

They work at all signal levels just like ports do, its a red herring.

rgds, sreten.

 

[Raynald]

I used to sell the Kef C55 and I was very unimpressed with them, and I am a Kef fan who owns two pairs now.

 

[wmgwizard]

Hi,

A passive radiator does not need "enough" power to "get it moving".

They work at all signal levels just like ports do, its a red herring.

rgds, sreten.

I was trying to explain a fairly complex interaction between woofer & passive radiator in terms a less experienced individual might understand.

The point being that with only a few watts the main woofer is not moving enough air to fully excite the passive radiator. Yes it is always coupled by the air trapped in the cabinet but it is only extending low frequencies within a fairly narrow pass band. Without sufficient excitation output will suffer.

 

[maravillo]

Thanks for the kind replies. Raynald: I saw you use the Reference 2, which are about 6x the price. What is the other model? Did you see the speakers responded to a certain kind of amp or were they consistently under powered in the low-end?

Above all I'd like to know how an amps max watt power relates to frequency response at lower levels.

In the example of a Tripath, if I have a 15W amp running at a low level, way beyond its max volume will it trigger a more narrow frequency response than a 60W amp running at the same volume level?

Can the 60W amp trigger a speaker response that another amp can't?

 

[sreten]

I was trying to explain a fairly complex interaction between woofer &
passive radiator in terms a less experienced individual might understand.

The point being that with only a few watts the main woofer is not moving
enough air to fully excite the passive radiator. Yes it is always coupled by
the air trapped in the cabinet but it is only extending low frequencies within
a fairly narrow pass band. Without sufficient excitation output will suffer.

Hi, What you are saying is simply wrong, it doesn't work like that, rgds, sreten.

 

[Raynald]

Thanks for the kind replies. Raynald: I saw you use the Reference 2, which are about 6x the price. What is the other model? Did you see the speakers responded to a certain kind of amp or were they consistently under powered in the low-end?

Above all I'd like to know how an amps max watt power relates to frequency response at lower levels.

In the example of a Tripath, if I have a 15W amp running at a low level, way beyond its max volume will it trigger a more narrow frequency response than a 60W amp running at the same volume level?

Can the 60W amp trigger a speaker response that another amp can't?

I actually have Reference 107 and 103.2 right now. When the C55 and other first generation Uni-Q Kefs came out I was working in a store that had a huge choice of good electronics to drive them with. We tried everything but with little success. It has been a couple of decades so I don't remeber details anymore, more like "liked" or "did not like". In general I would say that series was indeed weak in the bass and those first Uni-Q drivers had an odd cupped sound in the midrange. Apparently they were much improved in later iterations in the reference line but by then I had left the business.