KEF LS50 disappointment :(

[Native_bon]

I did say from the start these speakers are not to your liking. I think you better sell & look at alternatives.

Use recomemmendations only as a guide. One thing I have learnt dnt buy because ever one says it good. your own ears is the ultimate answer to what sound you want, even then its still hard to narrow things down.

 

[hg]

Can I use PEQ to lift bass response of a standmount speaker? If yes, what is the limit of this approach? How much increase at lower frequencies (in db) is accoetable? For a speaker with -6db point at 50 hz and -12 db at 32 hz, can I raise 12 db using PEQ for a flat frequency response till 32 hz. That would be sufficient for all kind of music except for home theater. one negative could be danger of burning the speaker by pumping so much energy in the speaker at that low frequency. How do I estimate what is the max energy I can put in the speaker safely? For average music listening levels ( about 86 to 90 db at 1 m), is there a danger for kef ls50.

As mentioned ealier, you have a desk speaker and not a main speaker. The coaxial unit is tiny and sized for work as a midrange above about 400 Hz in main speakers. The KEF LS50 starts to roll off below about 120 Hz and produces high levels of distortion below 500 Hz for 90dB at 1m. There is no plot for 95dB at 1m like a normal main speaker. The port is tuned somewhere around 55Hz from the impedance plot below which the output rolls off steeply (the anechoic chamber used in the measurements is too small for reliable measurements at these frequencies). The port is now starting to move in the opposite direction to the woofer, starting to cancel the radiated sound and reducing the pressure inside the cabinet. Given any sort of significant signal the tiny cone will move from maximum deflection inwards to maximum deflection outwards grossly distorting the signal at higher frequencies while producing almost no low frequency output. The idea of trying to boost the output at these frequencies by something like 20dB is not viable.

What your speakers really need is a pair of woofer cabinets something like this to sit on. A pair of subwoofers that are clean to well above 200Hz would be another option. A single subwoofer would also help substantially if properly integrated. I strongly suspect the problems you had with the subwoofer you tried was a failure to get it to work properly in your room rather than a problem with the quality of the subwoofer itself. Which is not to say it was the optimum subwoofer for your situation but almost any properly integrated subwoofer has got to be a significant improvement on trying to use desk speakers on their own as mains.

 

[Vladimir]

So... what he basically needs is a pair of KEF R700s. *biggrin*

 

[hg]

So... what he basically needs is a pair of KEF R700s. *biggrin*

...or a pair of Q700s to keep the cost near that of the LS50s.

shkumar4963, for an easy way to get a feel for how to integrate a subwoofer I would suggest downloading the free Room Eq Wizard and having a play with the Room Simulator (5th picture down). This lets you put in your room dimensions, hardness of walls and then interactively move the listening position and sub positions while showing the room response. A good way to get a rapid idea of what needs addressing at low frequencies.

 

[shkumar4963]

Thanks to everyone. Lots of good suggestions. To clarify, my intention was not to do this with my speakers but to better understand why or why not it could be done. In fact i am very happy with ls50 and the more i listen the more i like them. Last weekend I auditioned cm5. The bass response was much better for sure but the vocals were not natural. You can clearly feel that the singer was not there and it was just a speaker. With ls50 in my set up vocals are so clear that you almost mistake it that the singer is just there. Besides WAF prevents me from getting r700.

At the first glance, the logic about 20 db dynamic range made sense to me but on further thinking it did not seem right. Assuming that the speakers are rated at 100wrms and are audiophile speakers, they must be capable of handling dynamic peaks of 20 db (if that is what we are assuming peaks to be) at 100 wrms power. That means while speakers can take only 100 watts rms power, the driver excursions or movements are capable of dynamic peaks of 20 db. In that case as long as the rms power stays within 100 watts, we need not worry about the 20 db dynamic peaks. Am i thinking about this incorrectly?

Also if RMS power is of concern then we just have to limit the overall volume to less than 91 db. so the question is what base boost (how many db at 50 hz and how many db at 32 hz] can be applied without damaging the speakers?

Distortion will be a concern and may impact the quality of sound but would that be worse than not having any sound at 40 hz. Besides, I have read that distortion at less than 80 hz is really not discernable to human ears. Not sure if that is true.

 

[hg]

At the first glance, the logic about 20 db dynamic range made sense to me but on further thinking it did not seem right. Assuming that the speakers are rated at 100wrms and are audiophile speakers, they must be capable of handling dynamic peaks of 20 db (if that is what we are assuming peaks to be) at 100 wrms power. That means while speakers can take only 100 watts rms power, the driver excursions or movements are capable of dynamic peaks of 20 db. In that case as long as the rms power stays within 100 watts, we need not worry about the 20 db dynamic peaks. Am i thinking about this incorrectly?

You really have not noticed how large woofers or subwoofers need to be in order to produce deep bass?

Your driver has a linear displacement of about 3 mm and a surface area of 75 cm^2 (not sure how the surround has been accounted for) which determines how loud it can play cleanly. At your 32 Hz this is about 70 dB at 1m distance. Sitting further away will reduce the level but room gain will bring it up so let's stick with about 70 dB. This is about 10 dB above the level of audibility and so will not be easy to hear in the presence of higher frequencies. Looks like my estimate of 20 dB was on the small side and your speakers are short by about 35 dB. This estimate was without a port, with a port and below the tuning frequency the port and cone are working against each other and will cancel to some extent giving you less than 70 dB output at full deflection.

A reasonable 12" ported speaker can give you 110+ dB at 1m and 32 Hz but nothing much smaller will. Which is why the standard high fidelity speaker used to be a 12" woofer, 5" midrange and a 1" tweeter and today is more like 2 x 8" woofers, 5" midrange and 1" tweeter.

PS I have had to remove the links to the data for your driver and the equal loudness contours to get passed the wretched spam filter. This forum is hard work.

 

[shkumar4963]

Thanks HG. Yes. I forgot the ported speaker part. Thanks for reminding me about that.

So if I input a sine wave at 32 hz to the speaker, what would I hear?

My guess. The port will get excited and I should hear the port frequency at 79 hz if that is where it is. Would I then get the port induced drop off from there to lower frequencies?

 

[hg]

So if I input a sine wave at 32 hz to the speaker, what would I hear?

My guess. The port will get excited and I should hear the port frequency at 79 hz if that is where it is. Would I then get the port induced drop off from there to lower frequencies?

If the cone is moving at 32 Hz then the port will also move at 32 Hz. Not sure where you are getting 79 Hz from? The cone will also produce harmonic distortion tones at 64 Hz, 96 Hz, etc... at a lower level. However, the distortion tones might actually be further above the threshold of audibility than the fundamental and therefore perceived as louder than the fundamental. You can see this on equal loudness contours ["equal loudness contours" in google]

To give some idea of how loud your speaker might play click on the measurement section on the RHS here ["Neumann KH 120" in google]. Although norminally a 5" like yours, this speaker has a larger surface area than yours (no tweeter in the middle), a greater deflection and probably a lower port tuning and yet it cannot quite make 70 dB at 32 Hz (if the plot can be believed - it is difficult to accurately measure at this frequency). The output from your LS50 is going to be less and might even be below the threshold of audibility.

If you want decent deep bass in your room then you will need something like a 12" driver or 2 x 8" drivers. A 10" might do it depending on factors like the room and placement but a single 8" probably not. Physics requires the compression of a lot of air at low frequencies whereas at high frequency a tiny 1" cone moving 1 mm may be sufficient.

PS Again the spam filter is preventing the posting of links and I am close to giving up with it.

 

[SteveR750]

So if I input a sine wave at 32 hz to the speaker, what would I hear?

My guess. The port will get excited and I should hear the port frequency at 79 hz if that is where it is. Would I then get the port induced drop off from there to lower frequencies?

If the cone is moving at 32 Hz then the port will also move at 32 Hz. Not sure where you are getting 79 Hz from? The cone will also produce harmonic distortion tones at 64 Hz, 96 Hz, etc... at a lower level. However, the distortion tones might actually be further above the threshold of audibility than the fundamental and therefore perceived as louder than the fundamental. You can see this on equal loudness contours ["equal loudness contours" in google]

To give some idea of how loud your speaker might play click on the measurement section on the RHS here ["Neumann KH 120" in google]. Although norminally a 5" like yours, this speaker has a larger surface area than yours (no tweeter in the middle), a greater deflection and probably a lower port tuning and yet it cannot quite make 70 dB at 32 Hz (if the plot can be believed - it is difficult to accurately measure at this frequency). The output from your LS50 is going to be less and might even be below the threshold of audibility.

If you want decent deep bass in your room then you will need something like a 12" driver or 2 x 8" drivers. A 10" might do it depending on factors like the room and placement but a single 8" probably not. Physics requires the compression of a lot of air at low frequencies whereas at high frequency a tiny 1" cone moving 1 mm may be sufficient.

PS Again the spam filter is preventing the posting of links and I am close to giving up with it.

Please stick with it, this is really interesting.

 

[Vladimir]

If mods are reading this, please add HG to the trusted list of posters. Thanks.

 

[shkumar4963]

Thanks. At 90 SPL the distortion THD is 89 db at 32, 68 db at 40, 65 db at 50 and 60 db at 60 hz. Is that you were referring to? For ls50 NRC measured the following for 84 db of sound at 2 meter the distortion was 74 db.

Clearly the surface area of the cone does not generate enough sound at that low hrequencies and no amount of PEQ can change that. Thanks HG.

On a separate note what threads do you, Vladimir, david@Harvey hang out at. I would love to monitor those threads. It is all very interesting.

 

[shkumar4963]

So to get lower frequencies what we need is ls500 that has ls50 type sturdy box and two side firing 8 inch drivers with tweeter and midrange same as what is in ls50. That will sound marvelous.

Oh wait a minute. They do have something very similar. It is called blade. Too bad I can not afford it and it is too big for my wife.

So now we are at square one again.

One question though. Kef r300 has similar set up. Cocentric tweeter and mid with a 6 inch bass driver. But it does not sound as good - not by a long shot. Vocals are not that clear and good. Why? any guesses?

 

[Frank Harvey]

Can I use PEQ to lift bass response of a standmount speaker? If yes, what is the limit of this approach? How much increase at lower frequencies (in db) is accoetable? For a speaker with -6db point at 50 hz and -12 db at 32 hz, can I raise 12 db using PEQ for a flat frequency response till 32 hz. That would be sufficient for all kind of music except for home theater. one negative could be danger of burning the speaker by pumping so much energy in the speaker at that low frequency. How do I estimate what is the max energy I can put in the speaker safely? For average music listening levels ( about 86 to 90 db at 1 m), is there a danger for kef ls50.

I'm just a bit puzzled as to why you would want to change the response of the LS50. It should show that the LS50 isn't the speaker for anyone wanting to do that. There are larger speakers with greater output should it be needed, but if they don't sound as good as LS50s, that tells you something

Many get hung up on numbers, and will tell you that LS50s will sound 'bass light'. That will be by those who haven't heard them. They're anything but. The LS50 has a fantastic tonal balance which doesn't lack bass, it just won't reach too deep, as the laws of physics will dictate. I've said it before, but try No Doubt's Hella Good at high levels on the LS50s and you'll hear what they're capable of (just one example that springs to mind).

Adding subs to extend that bass is not only possible but understandable, trying to increase the LS50's bass output is not.

You won't get a useable 32Hz from a speaker this size. To get any worthwhile output at 32Hz, you'll need a couple of very capable subs, and then you'd need to listen to music that will contain bass that deep to take advantage of it.

 

[hg]

I wrote a fairly lengthy reply while having my coffee with links to measurements which I was now allowed see in a preview so something seems to have changed. But when I tried to post it I received this:

"The word verification was not completed correctly. Please complete this new word verification and try again. If you feel this is in error, please report that you are blocked."

However there is no new word verification section and pressing save shows the same message again with no word verification section. Perhaps it could be sorted out by starting again and copying and pasting but I lack the will to try. Whether this message posts or I am blocked I think I have now had enough.

 

[steve_1979]

Can I use PEQ to lift bass response of a standmount speaker? If yes, what is the limit of this approach? How much increase at lower frequencies (in db) is accoetable? For a speaker with -6db point at 50 hz and -12 db at 32 hz, can I raise 12 db using PEQ for a flat frequency response till 32 hz. That would be sufficient for all kind of music except for home theater. one negative could be danger of burning the speaker by pumping so much energy in the speaker at that low frequency. How do I estimate what is the max energy I can put in the speaker safely? For average music listening levels ( about 86 to 90 db at 1 m), is there a danger for kef ls50.

I'm just a bit puzzled as to why you would want to change the response of the LS50. It should show that the LS50 isn't the speaker for anyone wanting to do that. There are larger speakers with greater output should it be needed, but if they don't sound as good as LS50s, that tells you something

Many get hung up on numbers, and will tell you that LS50s will sound 'bass light'. That will be by those who haven't heard them. They're anything but. The LS50 has a fantastic tonal balance which doesn't lack bass, it just won't reach too deep, as the laws of physics will dictate. I've said it before, but try No Doubt's Hella Good at high levels on the LS50s and you'll hear what they're capable of (just one example that springs to mind).

Adding subs to extend that bass is not only possible but understandable, trying to increase the LS50's bass output is not.

You won't get a useable 32Hz from a speaker this size. To get any worthwhile output at 32Hz, you'll need a couple of very capable subs, and then you'd need to listen to music that will contain bass that deep to take advantage of it.

Wise words.

 

[DocG]

I wrote a fairly lengthy reply while having my coffee with links to measurements which I was now allowed see in a preview so something seems to have changed. But when I tried to post it I received this:

"The word verification was not completed correctly. Please complete this new word verification and try again. If you feel this is in error, please report that you are blocked."

However there is no new word verification section and pressing save shows the same message again with no word verification section. Perhaps it could be sorted out by starting again and copying and pasting but I lack the will to try. Whether this message posts or I am blocked I think I have now had enough.

hg, me too, I enjoy your contributions to the forum. And I'm not so sure the forum is followed-up closely by the mods. So could you please send John Duncan an e-mail to add you to the 'trusted users'? That is: john.duncan.whf@gmail.com. He monitors this address closely so he should get it sorted rather quickly. I hope (out of self-interest, that is)...

 

[Vladimir]

On a separate note what threads do you, Vladimir, Hi-Fi section.

 

[4Barry]

I have read some (but certainly not all) of the posts on this subject. As I bought a pair of LS50's not long ago I thought I might put in my two pen'orth.

Obviously I liked the sound of the LS50's or I wouldn't have bought them. But when I got them home and set them up in my system I was more than somewhat disappointed. I was aware that these speakers take a bit of breaking in - but it was a lot more than that. There was actually way too much bass to begin with. I experimented with the bungs - but this did not help fix the problem. To cut a long story short the solution came in two parts. The first was getting the right speaker cable made a BIG difference. But the main thing was getting them in the right position with regard to the rear and side walls. They turned out to be incredibly sensitive to small changes in position. There was indeed another position where the bass seemed to disappear altogether! After nearly two weeks of experimentation of changing position and toe in I finally found a sweet spot. And now they sound just great. I've never had a speaker that was SO sensitive to position before. I wonder if it is because of the rear port?

 

[davedotco]

I have read some (but certainly not all) of the posts on this subject. As I bought a pair of LS50's not long ago I thought I might put in my two pen'orth.

Obviously I liked the sound of the LS50's or I wouldn't have bought them. But when I got them home and set them up in my system I was more than somewhat disappointed. I was aware that these speakers take a bit of breaking in - but it was a lot more than that. There was actually way too much bass to begin with. I experimented with the bungs - but this did not help fix the problem. To cut a long story short the solution came in two parts. The first was getting the right speaker cable made a BIG difference. But the main thing was getting them in the right position with regard to the rear and side walls. They turned out to be incredibly sensitive to small changes in position. There was indeed another position where the bass seemed to disappear altogether! After nearly two weeks of experimentation of changing position and toe in I finally found a sweet spot. And now they sound just great. I've never had a speaker that was SO sensitive to position before. I wonder if it is because of the rear port?

Hi and welcome.....*bye*

What is the rest of your setup, it would be helpful to know.

 

[Jota180]

I have read some (but certainly not all) of the posts on this subject. As I bought a pair of LS50's not long ago I thought I might put in my two pen'orth.

Obviously I liked the sound of the LS50's or I wouldn't have bought them. But when I got them home and set them up in my system I was more than somewhat disappointed. I was aware that these speakers take a bit of breaking in - but it was a lot more than that. There was actually way too much bass to begin with. I experimented with the bungs - but this did not help fix the problem. To cut a long story short the solution came in two parts. The first was getting the right speaker cable made a BIG difference. But the main thing was getting them in the right position with regard to the rear and side walls. They turned out to be incredibly sensitive to small changes in position. There was indeed another position where the bass seemed to disappear altogether! After nearly two weeks of experimentation of changing position and toe in I finally found a sweet spot. And now they sound just great. I've never had a speaker that was SO sensitive to position before. I wonder if it is because of the rear port?

I found the same about positioning. Too close to the rear wall and the bass reinforcement was too much and I've not really been able to push them too far the other way. If I pull them any further our from the wall they'll be sitting on my lap!

On mine, from the rear wall to the front of the baffle it's 90cm. One other thing I changed was my speaker stands because the others were wobbly and caused the bass to lose focus.

 

[Frank Harvey]

I had mine about 6-7" from the back (solid) wall without any major issues, and without help from room EQ.

 

[shkumar4963]

@Vladimir. I enjoy reading all your comments, especially when they are substantive and are explaining reasons for the sound that we hear

 

[Vladimir]

@Vladimir. I enjoy reading all your comments, especially when they are substantive and are explaining reasons for the sound that we hear

Likewise shkumar. I enjoy your interesting exploratory posts that keep our minds busy as bees.

 

[4Barry]

I'm having trouble posting a reply. Was it something I said?!!

I'll try doing it in smaller chunks....

 

[4Barry]

Hi Dave

The rest of my system currently consists of a Marantz CD6005 running through a Dac Magic DAC. My Linn turntable is resting at present whilst it awaits a new power supply. Naim 42/160 (Get out your history books!) pre/power amps. I have been using Spendor BC1's as my main speakers (most of the time) since I bought them new 37 years ago! A guest managed to blow both woofers a few months ago for me. I then had to use a pair of Wharfedale 9.1's from my bedroom system until, after a lot of listening and reading and umming and aahhing, I bought the Kef LS50's.