SL3-eXtreme Center channel speaker – a design and build story

[kach22i]

I've just skimmed through this thread for the first time.

WOW!
WOW!
WOW!

Anything I do from now on will seem minor in comparision.

Nice work.:rocker:

 

[Liquisonic]

rendering question

Hey Jon, just wondering how you did that "concept" rendering of the center channel.
Thanks Steve

 

[JonFo]

Jon,

This is easily one of the coolest DIY projects I've seen. Just a thought... not that you'd have any interest in changing the wiring of an already assembled and finely tuned speaker, but had you considered a different wiring setup to result in a single 4 2/3 ohm load with these six 7 ohm speakers? If you put three of the drivers in parallel, you'll have a 2 1/3 ohm load. Then put each of those sets of three in series with one another, for a single 4.67 ohm setup.

It's nice to drive the array with two amplifier channels as I believe you indicated you've done, but the somewhat high impedance load would probably not bring out the best of the amp's capabilities.

Anyway... just a thought. Thanks for fully documenting such a fantastic project!

- Jason

Hi Jason, thanks for the feedback and the notes on wiring options.

I do parallel the two series of drivers into a single 12 Ohm load for the amp.

I tried it with two channels driving each set of three, but the loads were too high.

Whenever I take down the screen again, I'll open up the line-array and redo the wiring to form two sets of paralleled drivers as you suggested.

I've read in several books and sites that paralleled should result in lower THD.

But for now, it’s working so well, I hardly want to mess it with it, I’d rather enjoy some music or movies

 

[JonFo]

Hey Jon, just wondering how you did that "concept" rendering of the center channel.
Thanks Steve

Steve, I used both photoshop (for editing the Sequel Pic and cutting out the Adire driver pic) and Visio to assemble the whole thing together.

Pretty simple, nothing fancy.

Next time, I'd use SketchUp to render the whole thing in 3D.

 

[JonFo]

Thanks to all for your enthusiastic feedback.

I sure love the results several years on. This center channel just has to be the best match I’ve ever heard short of using equal speakers across the front.
It’s ability to play clean and loud is amazing on movie materials. I’m pretty sure those using factory centers are missing out on some of the soundtrack at high volumes. This thing gets a real workout.
The recent movie, Dark Knight on BluRay with the HD soundtrack was a good example of a torture test for a center (heck, for the whole audio system).

I’m convinced more than ever that to truly get correct voicing and depth-of-field dispersion, the center has to be a vertical line-array (ESL part specifically).

Unfortunately, that really limits the possible installations to those willing to do acoustically transparent screens.

As my collection of SACD/DVA-A and BluRay music discs continues to expand, I appreciate its musical abilities more and more. This is truly a great sounding speaker.

 

[JonFo]

Here is a recent side view (I can't do front views without removing the screen), showing the array of RealTrap MiniTrapHFs lining the wall behind the SL3XC center.

There is also a Mondo Trap laid across over the top of this setup to mitigate mid-bass and sub room modes.

The brownish-looking cloth is actually black GOM acoustically transparent cloth used to reduce through-screen reflection issues.

The big ESL is reflective, and the screen is 'transparent' enough to let that shine back on bright scenes. So the extra bit of black cloth is there to mitigate.

With the wall behind it treated for absorption now, it is extremely clean.

 

[Tosh]

Jon,

I remember following this ambitious and impressive re-design when I was still just dreaming of a pair of SL3's, and your project was helpful in me deciding to get some for myself. Now I'm gathering some background on the SL3 and have some questions for you:

A. I'm trying to decide if the stock SL3 panel can play lower than 250Hz if crossed over steeper, or if there are other considerations. Your XO frequency and slope to the ESL is 450Hz at 12dB/oct which I'm assuming is to play them louder? (Stock SL3 is 250Hz @12dB/oct.) Did you try other frequencies and slopes? If so, how did it sound at 250Hz? Lower?

B. In your graph in post #31, it appears the ESL rolls off at about 24dB/oct at about 240Hz. Is this the natural roll-off or with a XO?

C. Do you have the measured values (mH) for the three inductors that are parts of the main bass XO; the ESL LCR notch (in series with the yellow 30uF cap); and the ESL LR high pass section (in series with the 1 Ohm resistor)? (Have I understood the purposes for the two ESL filter sections correctly?)

D. How did you arrive at settings for your DBX DriveRack to duplicate the passive LCR notch?

I'm hoping to at least set the frequency and slope with an active XO, but if I understand how and where the notches work, perhaps I can make these part of the XO. My aim is not to use digital filters like the DriveRack or Behringer DCX2496, but to use op-amps in the 'normal' way (having just recently fallen in love with the LM4562....)

Thanks,

Tosh

 

[JonFo]

Jon,

I remember following this ambitious and impressive re-design when I was still just dreaming of a pair of SL3's, and your project was helpful in me deciding to get some for myself. Now I'm gathering some background on the SL3 and have some questions for you:

A. I'm trying to decide if the stock SL3 panel can play lower than 250Hz if crossed over steeper, or if there are other considerations. Your XO frequency and slope to the ESL is 450Hz at 12dB/oct which I'm assuming is to play them louder? (Stock SL3 is 250Hz @12dB/oct.) Did you try other frequencies and slopes? If so, how did it sound at 250Hz? Lower?

I actually run all three fronts at 315Hz now, with a 4th order (24dB/oct) LR crossover.

I did try 250Hz, but it just can’t play those frequencies loud enough (remember, I’m shooting for 105db SPL with less than 1% distortion, so I need to remain well within the performance envelope of a driver).
I do plan to re-adjust the center to x-over a bit higher than 315Hz, maybe back up to 400Hz.

B. In your graph in post #31, it appears the ESL rolls off at about 24dB/oct at about 240Hz. Is this the natural roll-off or with a XO?

IIRC, that set of Line-array and panel measurements we’re done direct, bypassing any X-O, as I wanted to see what was the true response of the driver itself.
As you can see, the natural roll-off is pretty steep. So a 250hz crossover is too low IMHO.

C. Do you have the measured values (mH) for the three inductors that are parts of the main bass XO; the ESL LCR notch (in series with the yellow 30uF cap); and the ESL LR high pass section (in series with the 1 Ohm resistor)? (Have I understood the purposes for the two ESL filter sections correctly?)

I did not bother with measurements of the passive crossovers, as I was planning to dump them anyway, and measured the actual speaker response (in-situ) and corrected to those metrics.

D. How did you arrive at settings for your DBX DriveRack to duplicate the passive LCR notch?

I did not try to replicate the factory settings, rather aimed for integrating the bass and the panel using actual in-room measurements (plus some close-mic samples for validation).
Plenty of polarity / phase /delay adjustments and tweaks as well. Delay being a key one to time-align the impulse responses of the panel and woofers. Hard to do that with passives ;-)

A key point here is: to use an active XO, you must own and learn how to use a measurement system (like R+D, REW, FuzzMeasure, etc.). Since you really want to adjust the XO and any other parameters (like delay or EQ) to your specific environment.

I'm hoping to at least set the frequency and slope with an active XO, but if I understand how and where the notches work, perhaps I can make these part of the XO. My aim is not to use digital filters like the DriveRack or Behringer DCX2496, but to use op-amps in the 'normal' way (having just recently fallen in love with the LM4562....)

Thanks,

Tosh

Ah, if rolling your own active, then you have some work. But one approach is to use a digital to do all the measurement and modeling, and then transcribe the results of that into your analog electronics once you’ve lived with it for a few weeks (You will be tweaking it, trust me).
You could even use transfer function comparisons between the digital and your analog setup to validate that you got close to the target.

Cheers,

Jonathan

 

[Tosh]

Thanks for all the info, Jonathan!
Maybe you can tell by my questions that I don't have ANY measuring tools, not even an inductance or capacitance meter? I agree that a proper measuring system is vital to ultimate full active XO success tailored to my room, but for now I think I would be happy if I could just make the bass section active. I'll try setting my cheapie active XO at 250Hz (and bypass the bass passive XO) and see what it sounds like. Baby steps!

Thanks again!

 

[TYY]

Hello Jonathan,

Thank you for posting this inspiring project. When it comes to the replacement SL3 panels, did you notice/measure a significant difference in performance between the original and new panels?

Based on your experience with the stock SL3, where would you recommend crossing over with a subwoofer (e.g. 50, 60, 70, 80 Hz)?

If using the stock woofer and panel configuration, do you have any opinions regarding active crossover order? Based on your measurements and assuming lower SPL, have you found there is much to be gained by veering from the high and low transfer functions of the original schematic?

Regards,

TYY

I actually run all three fronts at 315Hz now, with a 4th order (24dB/oct) LR crossover.

I did try 250Hz, but it just can’t play those frequencies loud enough (remember, I’m shooting for 105db SPL with less than 1% distortion, so I need to remain well within the performance envelope of a driver).
I do plan to re-adjust the center to x-over a bit higher than 315Hz, maybe back up to 400Hz.


IIRC, that set of Line-array and panel measurements we’re done direct, bypassing any X-O, as I wanted to see what was the true response of the driver itself.
As you can see, the natural roll-off is pretty steep. So a 250hz crossover is too low IMHO.


I did not bother with measurements of the passive crossovers, as I was planning to dump them anyway, and measured the actual speaker response (in-situ) and corrected to those metrics.



I did not try to replicate the factory settings, rather aimed for integrating the bass and the panel using actual in-room measurements (plus some close-mic samples for validation).
Plenty of polarity / phase /delay adjustments and tweaks as well. Delay being a key one to time-align the impulse responses of the panel and woofers. Hard to do that with passives ;-)

A key point here is: to use an active XO, you must own and learn how to use a measurement system (like R+D, REW, FuzzMeasure, etc.). Since you really want to adjust the XO and any other parameters (like delay or EQ) to you specific environment.




Ah, if rolling your own active, then you have some work. But one approach is to use a digital to do all the measurement and modeling, and then transcribe the results of that into your analog electronics once you’ve lived with it for a few weeks (You will be tweaking it, trust me).
Your could even use transfer function comparisons between the digital and your analog setup to validate that you got close to the target.

Cheers,

Jonathan

 

[JonFo]

Hello Jonathan,

Thank you for posting this inspiring project. When it comes to the replacement SL3 panels, did you notice/measure a significant difference in performance between the original and new panels?

Based on your experience with the stock SL3, where would you recommend crossing over with a subwoofer (e.g. 50, 60, 70, 80 Hz)?

If using the stock woofer and panel configuration, do you have any opinions regarding active crossover order? Based on your measurements and assuming lower SPL, have you found there is much to be gained by veering from the high and low transfer functions of the original schematic?

Regards,

TYY

Yes, the improvement is both measurable and noticeable. I don’t have consistently taken before/after of the SL3 panels, but I did for my Monolith panel updates.

I’d recommend a sub for any ML model. Not because they don’t have good bass performance, but mostly because a good sub (such as a Depth) will enable you to both position it for optimal integration, as well as an ability to play louder and deeper with less distortion. The SL3 woofer, relieved of low-frequency duties will also now deliver improved mid-bass performance as well. So all these add up to improved audio reproduction.

Crossover for an SL3 should be no lower than 80hz IMHO.

If bypassing stock passives (removing parts, as I did in this project) then the slopes I recommend between woofer and sub are fourth-order, and between woofer an panel, second order or fourth order.
Personally I use fourth-order (24/dB octave) LR alignments in my setup with great results.

Are you planning an active setup?

If so, please start a new thread and we can discuss at length.