The KEF LS50 and tubes WOW WOW WOW!

[garylkoh]

Try this one for size: http://www.rythmikaudio.com/F12.html

I recommend Rythmik subs when an old Genesis customer can't afford one of our new ones to replace a dead 20-year old G928. Are they as good? No. However, they are 80% cheaper. Are Genesis subs 5 times better? May be. You'd need two of those to equal a single G928 though......

IIRC, we had a very long thread on subwoofer integration a year or two ago on this forum. Don't dismiss it out of hand - I think that it might be worth the effort if the LS50's are as good as everybody says that they are.

 

[Andre Marc]

Try this one for size: http://www.rythmikaudio.com/F12.html

I recommend Rythmik subs when an old Genesis customer can't afford one of our new ones to replace a dead 20-year old G928. Are they as good? No. However, they are 80% cheaper. Are Genesis subs 5 times better? May be. You'd need two of those to equal a single G928 though......

IIRC, we had a very long thread on subwoofer integration a year or two ago on this forum. Don't dismiss it out of hand - I think that it might be worth the effort if the LS50's are as good as everybody says that they are.

Hey Gary:

Nice sub! I don't dismiss out of hand, I just think you would have to spend as much or more than the cost of the LS50 to get a subwoofer
that can integrate with the quickness of the KEFs. Certainly this looks like a great unit, but still $1000, then double that for stereo.

 

[mep]

Well, we have now moved from "you can't integrate a pair of subs with the LS50s" to "it's too expensive to integrate a pair of subs with the LS50s."

 

[Andre Marc]

Well, we have now moved from "you can't integrate a pair of subs with the LS50s" to "it's too expensive to integrate a pair of subs with the LS50s."

I will give you that.

In the end, nothing is impossible. It just comes down to logistics, expense, and the will.

We still have the question, is it better to buy the LS50, and spend as much or more on subs and cables, or buy something
higher up in the KEF line with the Uni Q driver and more bass? There is no right answer, each prospective customer
must decide for them selves.

 

[DaveyF]

IMO, there are two factors that come into play when one decides to entertain subs. One...the price and two ( which seems to be overlooked by most) is whether the room can support the bass. I was at a very good local dealer yesterday and we had long conversations on a variety of gear. He had just received a pair of Velo DD15's in stock. As most of you know, this sub uses a 15" driver in a large box. To entertain using a sub like this in a room like mine would be foolhardy, IMHO. We both agreed that with subs, one has to look very hard at the size of the room to dictate the maximum likelihood of having success with the sub in question. ( BTW, I do NOT believe the answer is to place any large sub in any room and simply turn down the sub volume to compensate for room overload).
With the LS50's in a small room...which is where they are MOST likely to be used ( again IMHO) would dictate a small sub at best, and like Andre is pointing out, a difficult IF not impossible task to blend. Probably NOT left to the less experienced a'phile to attempt.

 

[mep]

Davey-Your points are well taken. If your listening room is so small it could double as a broom closet, then of course it won't support big subs that are capable of true bottom end performance. Are the majority of people who are buying LS50s using them in small rooms? I personally have no idea. And no one said that "you can place any large sub in any room and simply turn down the sub volume to compensate for room overload." I know I didn't say that. Turning down the volume level on any sub in any room is good advice as a starting point to find the correct setting for your room.

 

[FrantzM]

This is coming from an owner of the LS50.I haven't tried subs with the LS50 and likely will not. As they are the LS50 are very satisfying and I will move toward a more fullrange and large scale speaker soon. These speakers will be matched with subwoofers, at least 3 likely more. This out of the way

Are the LS50 good? More than their lowly (in High-End Audio parlance ) price would suggest.
Do they need a sub? Absolutely ... but

The "but" is not a matter of their "speed". This falsity needs to be buried. It is too often invoked.
The question remains that of an always difficult proposition. Matching a two way mini-monitor type with a sub. One usually ends up with a speaker with a schizophrenic character: As long as music calls for small scale and relative limited SPL all is well the 2-way + subs better than the 2-way alone.. Once scale changes to large and/or more SPL, the system sounds "broken", the previous integration is destroyed and one come back to the ugly cliches of "slow" subs and "fast' mains ... The reality is: most speakers in the vast majority of rooms regardless of the speakers intrinsic bass output need subs. This is based on the physics underlying small-room acoustics. The paradox is that subs work better with speakers that have substantial bass output. By that we mean , speakers able to produce good and in undistorted output in the upper low bass (50 to 100 Hz) and the mid bass ( 80 to 300 Hz) by their lone selves. The LS50 are very good and can fool a person once in a while into thinking they re capable bass reproducer. A quick listen to speakers capable of true bass will quickly erase that notion.

Thus mating the LS50 with subs is risky, not easy and likely one would have to be careful on the volume control so not to reach the LS50 output limitations, but it can be accomplished, I would suggest DSP if one is not adverse to the notion (an unfortunate although widespread audiophile tendency).

 

[DaveyF]

Mep, I'm not saying that you stated that. However, I have had many hobbyists tell me that it is no problem to put any size sub into any size room as the volume simply needs to be reduced to compensate for the room overload. IMHO, this is simply bunk and shows that the poster has really no experience in setting up a sub.

 

[Andre Marc]

IMO, there are two factors that come into play when one decides to entertain subs. One...the price and two ( which seems to be overlooked by most) is whether the room can support the bass. I was at a very good local dealer yesterday and we had long conversations on a variety of gear. He had just received a pair of Velo DD15's in stock. As most of you know, this sub uses a 15" driver in a large box. To entertain using a sub like this in a room like mine would be foolhardy, IMHO. We both agreed that with subs, one has to look very hard at the size of the room to dictate the maximum likelihood of having success with the sub in question. ( BTW, I do NOT believe the answer is to place any large sub in any room and simply turn down the sub volume to compensate for room overload).
With the LS50's in a small room...which is where they are MOST likely to be used ( again IMHO) would dictate a small sub at best, and like Andre is pointing out, a difficult IF not impossible task to blend. Probably NOT left to the less experienced a'phile to attempt.

DaveyF, good points all around. Clearly the room is a major factor. That I would, add also applies to large floor standing speakers, does it not?

I really wonder if Mikey gets the very best out of the XLFs in his small room.

 

[Andre Marc]

Mep, I'm not saying that you stated that. However, I have had many hobbyists tell me that it is no problem to put any size sub into any size room as the volume simply needs to be reduced to compensate for the room overload. IMHO, this is simply bunk and shows that the poster has really no experience in setting up a sub.

+1.

 

[DaveyF]

This is coming from an owner of the LS50.I haven't tried subs with the LS50 and likely will not. As they are the LS50 are very satisfying and I will move toward a more fullrange and large scale speaker soon. These speakers will be matched with subwoofers, at least 3 likely more. This out of the way

Are the LS50 good? More than their lowly (in High-End Audio parlance ) price would suggest.
Do they need a sub? Absolutely ... but

The "but" is not a matter of their "speed". This falsity needs to be buried. It is too often invoked.
The question remains that of an always difficult proposition. Matching a two way mini-monitor type with a sub. One usually ends up with a speaker with a schizophrenic character: As long as music calls for small scale and relative limited SPL all is well the 2-way + subs better than the 2-way alone.. Once scale changes to large and/or more SPL, the system sounds "broken", the previous integration is destroyed and one come back to the ugly cliches of "slow" subs and "fast' mains ... The reality is: most speakers in the vast majority of rooms regardless of the speakers intrinsic bass output need subs. This is based on the physics underlying small-room acoustics. The paradox is that subs work better with speakers that have substantial bass output. By that we mean , speakers able to produce good and in undistorted output in the upper low bass (50 to 100 Hz) and the mid bass ( 80 to 300 Hz) by their lone selves. The LS50 are very good and can fool a person once in a while into thinking they re capable bass reproducer. A quick listen to speakers capable of true bass will quickly erase that notion.

Thus mating the LS50 with subs is risky, not easy and likely one would have to be careful on the volume control so not to reach the LS50 output limitations, but it can be accomplished, I would suggest DSP if one is not adverse to the notion (an unfortunate although widespread audiophile tendency).

Frantz, this is why I so like the REL subwoofer connection method. It takes the signal from the amp speaker output and does away ( to a great extent) with the mains having to struggle as the scale increases. If I'm not mistaken, REL is the ONLY subwoofer company that offers this connection ability.

 

[DaveyF]

DaveyF, good points all around. Clearly the room is a major factor. That I would, add also applies to large floor standing speakers, does it not?

I really wonder if Mikey gets the very best out of the XLFs in his small room.

Andre, I would strongly suspect that Mikey is getting nowhere near the performance that the XLF's are capable of in his room, or that he paid for...( well maybe he is getting that, LOL).

 

[Andre Marc]

Andre, I would strongly suspect that Mikey is getting nowhere near the performance that the XLF's are capable of in his room, or that he paid for...( well maybe he is getting that, LOL).

LOL, maybe so. Interestingly, in his room, he loved the Joseph Audio Pulsars, which IMO, are terrific speakers with very impressive top to bottom performance, and
very realistic bass.

 

[FrantzM]

Frantz, this is why I so like the REL subwoofer connection method. It takes the signal from the amp speaker output and does away ( to a great extent) with the mains having to struggle as the scale increases. If I'm not mistaken, REL is the ONLY subwoofer company that offers this connection ability.

Davey

The connection method would not help in this regard. You still are feeding the full output of the amp to the mains. TO reduce the potential problem you would need to have something reducing the level of low frequencies to the mains.. You can't do it witht he parallel method advocated by REL.

As for taking the signal from the amps REL is far from the only company doing so. It ids actually a very common way of hooking up subs.

To understand this let's take an imaginary 2-way monitor with limited output, the so-called mini-monitors. Let';s suppose that the 2-way is not comfortable at level above 95 dB... We can safely assume that this speaker will not be comfortable outputting a 60 Hz signal at 100 dB. A decent subwoofer with a 10 inch cone is capable of that and even lower with not much problem of distortion ... You can see the 2-way leaving where the subs continue to play ... And this not even considering what happens up in frequency , still below 500 Hz on term of directivity. The subs and mini-monitors are likely to have different dispersion characteristics. Depending on crossover frequency, slopes, room treatments, room dimensions, listener position and frequency content this variation in dispersion characteristics can be clearly heard. There are other factors but these IMO are preponderant.

 

[microstrip]

(...) I really wonder if Mikey gets the very best out of the XLFs in his small room.

I think your question needs reformulating, as the answer is too easy and surely unanimous - the XLF would sound better in larger rooms.

IMHO the real question is if any other speaker would sound better for him (or the few lucky invited people ) in his room.

 

[microstrip]

Frantz, this is why I so like the REL subwoofer connection method. It takes the signal from the amp speaker output and does away ( to a great extent) with the mains having to struggle as the scale increases. If I'm not mistaken, REL is the ONLY subwoofer company that offers this connection ability.

Davey,

Many subs have this type of connection - its supporters say it is advantageous as the sub woofer will keep the amplifier balance and flavor in the bass, and no strange and unforeseen filter will be applied to the main speakers. But this approach will please mostly those who say that the best systems who use with subs are those that would not need them by electrical reasons, as it will not make things easier for the system. I have built two double L-Pad resistor attenuators to use with my Behring DCX2496 in balanced mode with connection to the amplifier speaker outputs.

 

[DaveyF]

Davey

The connection method would not help in this regard. You still are feeding the full output of the amp to the mains. TO reduce the potential problem you would need to have something reducing the level of low frequencies to the mains.. You can't do it witht he parallel method advocated by REL.

As for taking the signal from the amps REL is far from the only company doing so. It ids actually a very common way of hooking up subs.

To understand this let's take an imaginary 2-way monitor with limited output, the so-called mini-monitors. Let';s suppose that the 2-way is not comfortable at level above 95 dB... We can safely assume that this speaker will not be comfortable outputting a 60 Hz signal at 100 dB. A decent subwoofer with a 10 inch cone is capable of that and even lower with not much problem of distortion ... You can see the 2-way leaving where the subs continue to play ... And this not even considering what happens up in frequency , still below 500 Hz on term of directivity. The subs and mini-monitors are likely to have different dispersion characteristics. Depending on crossover frequency, slopes, room treatments, room dimensions, listener position and frequency content this variation in dispersion characteristics can be clearly heard. There are other factors but these IMO are preponderant.

Frantz and micro, could you tell me another subwoofer company that utilizes the same connection protocol as REL. Speakon cable to amp speaker connections.....
You are right that you are still feeding the full output of the amp to the mains, BUT I do not see why you would have to reduce the level of low frequencies to the mains....they wouldn't be asked to reproduce anything in the bass that they wouldn't have to IF a sub wasn't present. Plus, presumably one has full control of the subwoofer parameters as far as volume and x-over point. If in your example the mains aren't comfortable at levels above 95db, this would apply whether a sub was in the system or not. In fact, i would say that with the sub in the system, the exact opposite is happening ( assuming that the set up is correct) and that is, the mains are now working less hard than before, not more.

 

[garylkoh]

Frantz, could you tell me another subwoofer company that utilizes the same connection protocol as REL. Speakon cable to amp speaker connections.....
You are right that you are still feeding the full output of the amp to the mains, BUT I do not see why you would have to reduce the level of low frequencies to the mains....they wouldn't be asked to reproduce anything in the bass that they wouldn't have to IF a sub wasn't present. Plus, presumably one has full control of the subwoofer parameters as far as volume and x-over point. If in your example the mains aren't comfortable at levels above 95db, this would apply whether a sub was in the system or not. In fact, i was say that with the sub in the system, the exact opposite is happening ( assuming that the set up is correct) and that is, the mains are now working less hard than before, not more.

Because the amp is still driving the mains even though they don't reproduce anything.

Look at the impedance of the LS50 for example:



Below 45Hz - where the speaker would not be producing any output, the impedance drops away to below 4 ohms. The power amp would still be putting out a lot of power for no sound. At worst, it would just heat up the voice coil. This would then result in thermal compression. Having a subwoofer that reduces the level of low frequency to the mains would help it sound even better in the mid/high frequencies.

 

[DaveyF]

Because the amp is still driving the mains even though they don't reproduce anything.

Look at the impedance of the LS50 for example:

View attachment 12550

Below 45Hz - where the speaker would not be producing any output, the impedance drops away to below 4 ohms. The power amp would still be putting out a lot of power for no sound. At worst, it would just heat up the voice coil. This would then result in thermal compression. Having a subwoofer that reduces the level of low frequency to the mains would help it sound even better in the mid/high frequencies.

Wouldn't this apply regardless of whether a sub was in the system or not?? Remember the sub has its own power amp...so in effect the amp for the mains is really only driving the mains.

 

[mep]

Gary-If I'm looking at the graph correctly, the impedance doesn't drop to below 4 ohms until the frequency is less than 20Hz. At around 55Hz, the impedance dips to over 5 ohms and then peaks again at around 42Hz to almost 12 ohms before the impedance starts nosediving. Sometimes when I look at the LS50s and then look at the KSA-250, I can't believe I'm driving the LS50s with that much amp. The LS50s make the KSA-250 sound like it is the most neutral amp on the planet-a real sonic chameleon that has no sound of its own. Or is it the other way around?