'LGT' Construction Diary

[wigginjs]

What kind of enclosure do you have the 23cm woofer in? Strictly based on it's size I would think you'd probably like to cross it at 60Hz or perhaps a little lower at 50 or 40Hz. I think that sub should really only be used for the bottom octave or so. Just my 2c.

[ShinOBIWAN]

Originally posted by ackcheng
Shin,

Thanks for your advice. I am using AT 5'(15CM) C-quence as mid and 23CM as my woofer. both of them are 8 ohms version

Raven 2.0 - 2000Hz up
15cm C-quenze - 350Hz - 2000Hz
23 cm C-quenze - 150Hz - 350Hz
Tact W210 - 150 Hz and below

I am using Linkwitz filter cross at 96dB slope.

may be I should try this

Raven 2.0 - 3000Hz up
15cm C-quenze - 350Hz - 3000Hz
23 cm C-quenze - 100Hz - 350Hz
Tact W210 - 100 Hz and below

If I shift the mid down to 200Hz, my woofer will only be working from 100hz to 200 Hz?

I am using class D Hypex amps to drive the speakers

Thanks for your advise! Will try to take some photos tonight!

Hi again Arthur,

It sounds like your system is basically the LGT but in slimmed down TMW form. At least from a driver perspective anyway.

The thin midrange problem I was having and which you seem to be relating to was due to some over excessive stop band correction which Uli fixed and showed me how to avoid. Before making any changes are you sure you haven't fell into this trap also?

During this project I made a few discoveries about the RAAL ribbon which will very likely apply to any ribbon. I'm not sure about dome tweeters but their dead and lifeless nature means it probably doesn't matter how they're used, they'll still sound unnatural. Dome tweeter jokes aside, if I crossed the RAAL low at 1.5Khz it simply sounds wrong in comparison to what I have now. You lose the presence and body of the upper midrange/lower treble and this is true despite very similar measured performance. Perhaps it is odd high order harmonic distortion from the ribbon being crossed low? Perhaps it is a mass/radiating area issue? I'm not 100% sure about either but I can say it doesn't sound as good. Try the Raven at 3Khz, since your crossing to the 5" the narrowing directivity of the mid driver will improve overall power response and better mate the directivity patterns of the two drivers at the crossover points. I assume you mid and tweeter spacing is close here.

I would try to abandon the steep filters for use with AT drivers, it harms the sound more than it helps. They're wideband and smooth at both ends so why create a problematic solution to an issue that doesn't exist. Its best to evaluate on the basis of each case and go for the lesser of evils approach. For example I found steep filters worked well with the ATC midrange but this was actually beneficial because I was running it right upto its upper and lower limits where resonanaces and distortion, respectively, became an issue overiding negatives surrounding steep filtering.
In this instance I chose 24dB LR slopes and it really does suit the AT's offering a good blend of stop band rejection, lessening driver to driver crossover stopband interaction along with promoting a more cohesive sound from drivers more effectively blending creating less of a sense of shifting directivity lobes and tonality. By this I mean with steep filtering the drivers can become more subjectively isolated and I find I can tell a shift of sound direction and tonality when different frequencies, covered by different drivers, are playing. A bit more crossover overlap from shallower filtering can create a more cohesive speaker and we are lucky that we can make the drivers behave optimally to virtually eliminate the phase problems from doing so.

You've also got a lot going on down low: A sub crossed in at 150hz to an 8" driver that then works to 350hz. I haven't heard your system so can't say whether it works and maybe you have preference for this setup but looking at it on paper its less than optimal IMO. Personally I'd shift the mid down to 200hz which allows it to cover yet more of the frequency range, it works excellently in my setup where I tried it at 500hz, 300hz, 200hz and 150hz. 200hz had the best blend of mid/upper bass weight and seamless integration out to the midrange.

For the 8" I'd use this with just a low pass and no high pass then bring the sub in at non directional frequencies to blend with the overall sound and fill out the low end. Reason being the sub will be some distance from the main driver array and at 150hz sound is directional. Crossing in at say 50 or 60hz is much better.

These are just my thoughts on how I'd do it and not everyone agree's on how things should be implemented but since your not 100% happy with the sound and we also have similar drive units then I think some of the ideas might be worth looking at.

[ShinOBIWAN]

Originally posted by m0tion
What kind of enclosure do you have the 23cm woofer in? Strictly based on it's size I would think you'd probably like to cross it at 60Hz or perhaps a little lower at 50 or 40Hz. I think that sub should really only be used for the bottom octave or so. Just my 2c.

Great minds think alike!

[ackcheng]

Thanks for your detailed response. I will certainly experiment with your suggested settings! Sound very logical and should be an ideal way to start!

Here is my speaker.

[FullThrottleRic]

Very nice work on the cabinet! Do you have a work log posted anywhere?

[tinitus]

That is pretty nice work ... looks very professional with finish like a violin ... have you built it yourself

[Salas]

Has it ever fallen on its side? I can see dents, or is it the lighting conditions playing with low res?

[chrismercurio]

I see lots of stuff in the room reflecting on a well prepped surfaced doused in poly.

C

[tinitus]

From the picture, the craftmanship appears like true artwork, and nothing less!

[ShinOBIWAN]

Truly beautiful work on those cabinets, I love the curves with the huge bevels to break up the shape and make things more interesting. Shame the photo and lighting quality isn't a wee bit better so we could see more.

[ackcheng]

It was done locally by a friend of mine. He knows someone in China who manufacture speaker cabinets and this was done as a sample........

Will try to take some more photos during the day time. I was trying to avoid using the flash and so this was taken using ISO1000.

[ackcheng]

When I look at my speaker again, I think the mid is actually AT 18J52 (18cm). Silly me! I will try to cross it as 3000Hz at the upper end and 200Hz at the lower end as a starting point!

[tinitus]

I did wonder about the size of that mid ... its also worth to mention that AT drivers are a bit bigger than others at the same nominal size, because ATs are measured by their actual cone size which others rarely are not, some are even measure with the chassis... so if you want a 5" you may actually need to consider a 4" AT ... if things hasnt changed

[ShinOBIWAN]

OK this may or may not prove interesting but it certainly brings home just how useless most of our rooms are and given this horrible performance, I frankly think its suspect to put across opinions on amplifiers, sources and loudspeakers anywhere outside of your own listening room. To think that cables make a difference here is frankly laughable, you've got far far bigger problems to worry about!

All measurements taken at the listening position some 2.7m away from the LGT's.

Please note none of these graphs are indicative of the loudspeaker natiive performance. I took them to show the just how much the room influences the loudspeaker and the sound you finally hear. Hopefully it brings home just how large a problem it is. Also bare in mind that this is with room correction[/b] expect things to look about 20-30% worse than this without.

First is a 1/24th smoothed FR and a 1 octave smoothed FR overlay with phase response. Its about +/-5dB, the saving grace is that most of these dips and peaks are narrow and the ear isn't so quick to pick up on such things, its still very far from ideal though No gating used


Next is step response.
Absolutely no way would a 3.5 way design using IIR filters look this good at the listening position. This at least shows a good transient behaviour is possible even at the listening position and in a poor room which is quite remarkable really. Nothing much to complain about here.


CSD showing decay behaviour during 1 second. Something to note is that noise floor of my measurements is around 55dB below the peak level of the loudspeakers hence you can see 'noise' in the area above 1Khz including the high pitch fan noise from the projector at 2.4Khz. Looking below 1Khz we can see awful decay behaviour. Digital room correction has somewhat calmed these problems but only physical treatments will serve to create cleaner behaviour. This type of plot is especially useful for seeing where treatment are most effective when applying them to your room.


By far the weakest link in the audio chain is not the loudspeaker but the room.

For comparison I will post the native performance of the loudspeaker to show just how much influence the room has on final sound quality.

[ShinOBIWAN]

Originally posted by ackcheng
When I look at my speaker again, I think the mid is actually AT 18J52 (18cm). Silly me! I will try to cross it as 3000Hz at the upper end and 200Hz at the lower end as a starting point!

Good point, now you've mentioned that and I've taken a closer look. I think your right. They're definitely larger the the 15cm.

With that in mind also try 2.5Khz.

[Salas]

I see something indicative of correct balance. You have the proper slant towards HF at listening position. See a plot from a speaker I measured at 2m that sounds subjectively accurate enough. Almost same trends.

[Dan_E10]

Hi Shin,
Awesome speakers! I've been following this thread for quite a while now. As has been said here so many times already, your work is very inspiring. I noticed that your using the Emu 1820M as your audio interface now. I'm using Emu's 1212M right now and I've been thinking about picking up an Audiodock or a whole 1820M off of e-bay to get the 8 channels out. Your positive experience with using it for a crossover duties is pushing me in that direction.

I'd also use it for measurement and there's something I'm wondering about. Emu only give specs on their soundcards for 20-20kHz on the analog outs even though that dac and the card can operate at 192kHz. I'd seen some tests with the Soundblaster X-fi which I believe uses the same dacs and is also a Creative Labs family product. Even though that card could also run at higher sampling rates, it looked like it had a brick wall lowpass filter slightly above 20kHz, at least on the line in. For testing, it would be nice to get some of those higher frequencies to preserve tweeter phase information lower down. From you loudspeader testing, does it look like the 1820M is taking in anything above 20k?
thanks!
Dan

[wigginjs]

For testing, it would be nice to get some of those higher frequencies to preserve tweeter phase information lower down.

Huh? Why would you need information from frequencies above 20KHz to get phase information below 20KHz?

[bigwill]

Here's a silly idea - why not record the speakers playing some music and post the recording online for people to listen to on headphones? I am completely aware of why this is silly but I think some SORT of idea of how a speaker sounded could be realised from this. I think more people should do this! IE "Help me cure my midrange honk! Listen to this recording"

This isn't specifically aimed at the OP but speaker builders in general..

[tinitus]

not a silly idea ... occationally I listen to sound clips of motorcycle exhausts

[geminni]

Originally posted by bigwill
Here's a silly idea - why not record the speakers playing some music and post the recording online for people to listen to on headphones? I am completely aware of why this is silly but I think some SORT of idea of how a speaker sounded could be realised from this. I think more people should do this! IE "Help me cure my midrange honk! Listen to this recording"

This isn't specifically aimed at the OP but speaker builders in general..

Hm.... Interesting, very interesting
But, you'll need the recording of your speaker too. Also it had to be recorded with same settings like ShinOBIWANs, mic, preamp, amp, music... I think....

[Dan_E10]

Hi Motion,

Huh? Why would you need information from frequencies above 20KHz to get phase information below 20KHz?

Programs like SoundEasy need to know the high and low end rolloffs of your drivers to accurate determine the minimum phase response. You need this to perform an accurate crossover simulation, at least the way SoundEasy does things. Check out Dave's speaker pages for a better description of this: Dave's Speaker Pages
Click on Driver Model Accuracy and its Impact on Phase for a full description of this. John Kreskovsky also has an excellent explanation of this somewhere on his site.

I would also imagine it would be important when performing the driver corrections as Ant has done with his Acourate generated filters. For most tweeters I believe the high end rolloff will occur above 20kHz. At least with SoundEasy, if you only have data up to 20k or so, you'll have to guess at what frequency the tweeter will start dropping off and you'll also have to guess what slope it will roll off at. If you get it wrong, the calculated minimum phase will not be quite right, even all the way down at a crossover frequency of 2.5 kHz. How much it could be off in the case of my speakers I'm not sure. I'm still measuring with an old Soundblaster Live which cuts out at 22kHz. This doesn't let me see any of my tweeter's rolloff, it's a straight line to 22 kHz on-axis. I'd assume this would be much easier to get right if you have a mic and soundcard that can measure high enough to show some of the tweeter's upper end rolloff.

Anyway, since Emu only give specs up to 20kHz it makes me wonder if they're letting anything through above that even when the card is set to higher sample rates.
Dan

[ShinOBIWAN]

Dan, EMU isn't an X-FI or Audigy. Different designs intended for different markets.

Read some reviews and look at the Rightmark results.

Reason why older creative products brickwall at 22Khz is because of the 48Khz internal sampling conversion that was imposed on anything and everything regardless of what sampling frequency you choose.

Not a problem with EMU cards, however you will need a mic that measures past 20Khz. Behringer ECM 8000 is only reliable to about 18Khz. I do not correct frequencies above 16Khz for this reason and rely on the natural behaviour on the driver.

[ackcheng]

Today, I tried to cross at 200/3000Hz 24dB. The initial results are much better! A lot more dynamic and less thin for the midrange. I got an impression that it plays louder as well. But not sure why. Will try to fine tune a bit more later

Arthur

[ShinOBIWAN]

Originally posted by ackcheng
Today, I tried to cross at 200/3000Hz 24dB. The initial results are much better! A lot more dynamic and less thin for the midrange. I got an impression that it plays louder as well. But not sure why. Will try to fine tune a bit more later

Arthur

That's good news then.

Try playing with the stuffing on the mid driver. Doing so makes subtle differences to the subjective speed of the sound although looking at the CSD's it hardly makes much difference. I have manage to tweak out some minor dips in the driver response when measured near field so maybe thats it.

Here's how I have it now:



Wool up front directly behind the driver on all walls, then a gap with just 10mm foam on the walls and right to the rear there a dense fill of wool with a large chunk of foam behind it.

Also bought a few huge bass traps to try and do something with the bass issues I'm having. Just finished putting those up so will have a measure and see what sort of difference its made.