Subwoofers in the midrange...

worlds largest subwoofer



http://www.royaldevice.com/custom3.htm

 

Looks like yer gonna need an extension on yer flat merlin

 

I started this thread, obviously I find cohesive the referred arguments, or I wouldnt quote them, but you came back with "too many generalisations and inaccuracies", is this what you consider constructive...

 

Both Steve (a talented speaker designer) and myself then countered to which you simply replied with the usual petulance.

Do you have any thoughts of your own?

 

Steve's subwoofers are more similar to my REL than to your JBL, as is the xover frequency he uses...

Fortunatelly I dont have to re-invent hifi like you do all the time, the laws of phisics have been around for a long time before you...

 

Antonio, I have better things to do

You are the one trying to reproduce 2 channel recordings using 7 speakers scattered around the room with loads of processing crossovers and filtering.

So don't talk to be about breaking the rules

 

I didnt invent surround, actually more people use it every day, but of course we are all wrong...

 

Nothing like as big as the sub featured in www.royaldevice.com but not a bad DIY effort I suppose.

http://forum.hifichoice.co.uk/viewtopic.php?t=11420

 

I think its the same one Dev

what amp will they use,Windscale?

 

Hi Saab

From what I remember its a horn loaded bass driver, so it only needs a few watts! crazy eh?

 

blimey,a house that will resonate to 1 hz using 1 watt,now that is clever

that guy must like bass then

 

Antonio,

test results show quite clearly that odd order harmonic distortion is a problem with many commercial subwoofers. It is also generally accepted that this type of distortion is both unpleasant (not occuring naturally) and destructive to perceived sound quality.

Now in Rel's case, 3rd harmonic distortion is greater than 10% even in their top models, and is even greater on the Strata. This problem exists regardless of playback level. If you are replaying a piece of music with say a low piano note at around 30hz, this distortion will be audible at 90hz (remember third harmonic) and like wise a 25hz organ note will produce annoying distortion at 75hz.

Thinking logically, it would make sense in this case to crossover below the point at which this distortion interferes with the music, so crossing over at 60hz (assuming a 4th order crossover slope is employed in the Krell) would make the distortion at 75hz a further 6db lower in relation to the main signal. As the majority of music contains no true notes below 30hz, the main distortion is likely to be at 90hz and above, so employing the filter setting you do would reduce the odd harmonic distortion to about -30db at 90hz and make it all but inaudible at higher frequencies.

So by crossing over at 60hz to you satellites, you are able to compensate for the distortion inherent in the design, producing a cleaner and more pleasing sound. Due to the high distortion measured in many commercially available subwoofers, this is accepted practice and indeed products are designed under the assumption that lower crossover settings will be used.

But what happens if you start off with very low distortion in the first place?

Just edited to add that having looked at the follow ups to Mr Greene's original response, you will see that provided one adheres to basic acoustic guidelines, there is no issue with higher crossover frequencies in a properly designed product. I hope that will clarify matters for you, but I will of course happily answer any questions you might have.

 

As Steve well said, if you use xover higher than 120hz, it is a 3 way system, regardless how many and where you place the subwoofers, and then you have all the related problems you so well mentioned, but, of course, well designed 3 way systems do exist...

About the distortion you mention, it is produced by the subwoofer, so it doesnt matter how low one sets the xover, it wont be affected, it will be all still played and heard...

I dont doubt those reports of distortion from REL subwoofers, but I dont doubt my ears and my guest's either, and no one ever noticed any problem with the bass in my room, on the contrary, then again, tube amps have a lot of distortion too, not to mention the speakers themselves...

 

OY!

All amps have distortions of one type or another, including digital ones.

PS
Dont ask me to explain that, cos I havent got the technical knowledge!.. but I read it so I know its true

 

So we all have to live with distortions, just choose, if you can, the ones that bother you less...

 

Glad we got that out of the way. So I am happy to have a reasonably designed three way system that keeps me entertained. I hope we can leave it there.

 

Chris,

Is correct THD........Total Harmonic Distortion however low 0.02% is still distortionm, weather you can hear it is another matter, however is Distrortion

 

At what point does distortion become audible?

It is worth remembering that valve amps produce maybe 2% of even order distortion, but I understand even order exists in the real world. The Subs create 10% of 3rd harmonic, which has been suggested is the reason for many s/s amps having that signature

 

I have a REL StentorII, could the distortion from the sub be the reason that it's now under my computer desk not being used since the change to Quad ESL-63 with there lack of distortion. Having tried to integrate it with the quads to no great effect, the speed of the bass was good problem is that I could always hear it alone not a part of the music.

PS: found a great use for it, every time the next-door apartment turns up his sub I just run a 30hz tone loud from the computer and the whole unit block moves he then turn it down. "Better than banging on the wall"

 

Class!