Subwoofer Tests - Fall 2007

**jmcomp124** · **11-02-07, 01:05 PM**

Quote:

SteveCallas wrote:

Needing a highpass at 20hz or else bottoming occurs is a problem in my book. There's a million options out there if you are only after good headroom, linear FR, and low distortion from 20hz on up. That's no longer a very difficult set of performance measures to excel in - it used to be a handful of years ago, but no longer. I won't say infrasonics is the latest craze, but when using a modern, high excursion 18" driver with an expensive low distortion motor technology like the LMS 18", solid <20hz performance should be a given.

Ricci is convinced the design is PR limited below 20hz - that sounds like a much more plausible explanation for the troubles going on when not using the highpass than it being anything driver related.

I don't know how else to explain to you guys. I have video taped PR and cone excursions and being PR limited is not the case. The WinISD models also say the same and it co-relates to my observations.
Why is this so hard to comprehend?

**Mark Seaton** · **11-02-07, 01:09 PM**

Quote:

jmcomp124 wrote:

I do have a very important question about HP filters. There has been a lot of disagreement and some people feel that I have been overly cautious and not using the full potential of my subs because of setting the rane PE-17's 2nd order BW filter at 20Hz. My subs are tuned to about 15Hz. Anything below 20Hz I consider unsafe for material like FOTP Sandstorm/Plane crash and WOTW (ground implodes) when listening close to reference/at reference/a few dB beyond reference (MV at 0). I have calibrated my subs (you know I have 2 of these babies) for 80dB AVIA for MV0.

Jai,

Questioning if your high pass at 20hz is rather pointless without context. Have you measured the electrical response to see that the high pass is in fact at 20Hz? You are using an analog device that has a rather wide range over a relatively small slider and the PEQ on the PE-17 has the same issue. It functions fine, but fine adjustment requires angular rotation that is equal to minutes and seconds on the dial. Have you measured the in-room response to see what the observed low frequency extension is despite having the filter in place?

While many overlook the interaction, the EQ applied has a significant effect on what is going on with the net electrical response. A couple of cuts or boosts in the lower octave or just lower Q filters will quickly affect the low end roll of as they interact with the filter. There are also questions of amplifier clipping. The CE4k is a nice amp, but I have yet to meet an amp I can't clip or a sub I can't overdrive or otherwise find the limits of.

Remember that there is an impedance minimum at the tuning frequency, and it would be expected that the amp would clip sooner there than elsewhere. How the amp behaves at clipping could just as easily be an issue. Ilkka should be able to note at what level, if any, he experienced any system limit, and possibly what the limiting factor was.

**SteveCallas** · **11-02-07, 01:09 PM**

Maybe a PR makes it easier for a driver to unload below tuning than a port? Ilkka, anything preliminary you can share?

**jmcomp124** · **11-02-07, 01:15 PM**

Quote:

Ricci wrote:

jmcomp124,
I know that we already discussed this once, but your design would seem to be PR limited below 20hz, especially right around tuning 15-16hz. I know I'm beating a dead horse here...

What makes you think it is PR limited.
Have you tried a WinISD or Unibox or some other model that tells you this design is PR limited? If so, my modeling is incorrect and I have calibrate to yours.
I have tried the model and I also have the box in real life. As I already mentioned, my observations with the box matches the model.
If Ilkka's observations are different, then I would need to investigate this further and hence my questions on HP filters.
I appreciate responses like yours but I want them to be backed by good reasons and not just "I think" or "would seem".
I am data driven, let's put it that way.

**jmcomp124** · **11-02-07, 01:20 PM**

Quote:

Mark Seaton wrote:

Jai,

Questioning if your high pass at 20hz is rather pointless without context. Have you measured the electrical response to see that the high pass is in fact at 20Hz? You are using an analog device that has a rather wide range over a relatively small slider and the PEQ on the PE-17 has the same issue. It functions fine, but fine adjustment requires angular rotation that is equal to minutes and seconds on the dial. Have you measured the in-room response to see what the observed low frequency extension is despite having the filter in place?

While many overlook the interaction, the EQ applied has a significant effect on what is going on with the net electrical response. A couple of cuts or boosts in the lower octave or just lower Q filters will quickly affect the low end roll of as they interact with the filter. There are also questions of amplifier clipping. The CE4k is a nice amp, but I have yet to meet an amp I can't clip or a sub I can't overdrive or otherwise find the limits of.

Remember that there is an impedance minimum at the tuning frequency, and it would be expected that the amp would clip sooner there than elsewhere. How the amp behaves at clipping could just as easily be an issue. Ilkka should be able to note at what level, if any, he experienced any system limit, and possibly what the limiting factor was.

Mark,
Very good points. Yes, I am absolutely sure that the slider in the Rane PE-17 is at 20Hz and yes I did measure the electrical response (loopback mode, you know what I mean). This was done very carefully with ETF. Yes, I have measured the in-roop response and also the electrical response of each filter setting.
I haven't found the limits of the CE4K yet

**jmcomp124** · **11-02-07, 01:30 PM**

Quote:

Mark Seaton wrote:

Jai,

Questioning if your high pass at 20hz is rather pointless without context. Have you measured the electrical response to see that the high pass is in fact at 20Hz? You are using an analog device that has a rather wide range over a relatively small slider and the PEQ on the PE-17 has the same issue. It functions fine, but fine adjustment requires angular rotation that is equal to minutes and seconds on the dial. Have you measured the in-room response to see what the observed low frequency extension is despite having the filter in place?

While many overlook the interaction, the EQ applied has a significant effect on what is going on with the net electrical response. A couple of cuts or boosts in the lower octave or just lower Q filters will quickly affect the low end roll of as they interact with the filter. There are also questions of amplifier clipping. The CE4k is a nice amp, but I have yet to meet an amp I can't clip or a sub I can't overdrive or otherwise find the limits of.

Remember that there is an impedance minimum at the tuning frequency, and it would be expected that the amp would clip sooner there than elsewhere. How the amp behaves at clipping could just as easily be an issue. Ilkka should be able to note at what level, if any, he experienced any system limit, and possibly what the limiting factor was.

Just to clarify. When I say 20Hz, it is the -3dB point of the electrical response which means roll-off starts slightly earlier. When the filter is set to 16Hz, the electrical response shows the roll-off starting around 20Hz (recalling from memory here).
I also measured the electrical response of the SVS Marchand black box and that 4th order filter had a boost in the vicinity of the roll-off. The Rane PE-17 looks like gold (no unnatural boost) as far as electrical response is concerned. Another option was to use a steeper filter at 16Hz but some modeling suggested that a 2nd order BW at 20Hz has similar roll-off to a 4th order L-R at 16Hz.

**Ilkka** · **11-02-07, 05:59 PM**

Quote:

jmcomp124 wrote:

This is very good to know. So was I right about how good these subs sound?

I do have a very important question about HP filters. There has been a lot of disagreement and some people feel that I have been overly cautious and not using the full potential of my subs because of setting the rane PE-17's 2nd order BW filter at 20Hz. My subs are tuned to about 15Hz. Anything below 20Hz I consider unsafe for material like FOTP Sandstorm/Plane crash and WOTW (ground implodes) when listening close to reference/at reference/a few dB beyond reference (MV at 0). I have calibrated my subs (you know I have 2 of these babies) for 80dB AVIA for MV0.
So here are my questions for you Ilkka,
1. Are you using any HP filter, if so, to what value have you set it to and what type of filter?
2. Have you tried the FOTP and WOTW scenes I am talking about, if not, can you try it sometime soon and report back? If you have tried it, how close to peak excursion was the driver?
3. How big is your room? Leaky? How far is your LP from the sub?
With FOTP (when they escape and the plane emerges from the valley) I registered 118dB at LP with subs calibrated equal to mains. I haven't tried calibrating the subs +3dB hot on this scene yet. I think it would cross 120dB at reference (MV0 and calibrated to 80dB with avia). With Happy feet avalanche scene, calibrated 6dB hot (LFE), I registered 117dB. Note that my room is effective 7000 cu ft (about 6000 cu ft and add another 1000 for leaky room). LP is about 16ft.
What are your thoughts Ilkka on the HP filter? I fear going below 20Hz with the 2nd order BW filter. I am almost 100% sure that if I set that filter at 16Hz and play FOTP at reference level my sub will bottom out.
Thoughts?
Can you try this sub in a larger room with various HP filter settings? The HP filter is the "Achilles feet"

for this sub IMHO.

1. At the moment I'm not using any HP filter. During the GP session I used a 20 Hz 2nd order BW high pass filter (the lowest the DCX2496 allows). But I added a low-Q boost at 20 Hz so it became an effective ~16 Hz filter. I didn't bottom out the active driver or the PRs (well you can't really bottom out them).

2. I haven't yet tried those scenes with this sub. I will try them and report back. Though I'm not sure if I'm able to push this sub up to its limits. Remember that I live in an apartment.

3. My room is really small, only around 1500 cu ft and open (regular doorway) to ~2500 cu ft.

Here's the FOTP scene you mention. I doubt the <15 Hz material is strong enough to make the active driver bottom out. If it bottoms out, it is caused by the 25-30 Hz material instead. Also the WOTW chapter5 doesn't have that much strong sub-15 Hz material. All the really loud stuff is higher.

**Ilkka** · **11-02-07, 06:01 PM**

Quote:

ISLAND1000 wrote:

Jai, it sounds like YOU should be the one giving all the listening impressions not Ilkka.

Quote:

Does your speaker wire get warm to the touch after playing loud and low?

What kind of wire (gauge) you are using? That is definitely not normal.

**Ilkka** · **11-02-07, 06:09 PM**

Quote:

Mark Seaton wrote:

Ilkka should be able to note at what level, if any, he experienced any system limit, and possibly what the limiting factor was.

During the GP measurements the performance was limited by the active driver (long sine sweeps). It couldn't take the 120 dB (nominal at 50 Hz) sweep, which is no means bad performance.

The 118 dB sweep went well all the way down to 10 Hz.

**Ilkka** · **11-02-07, 06:17 PM**

Quote:

SteveCallas wrote:

Maybe a PR makes it easier for a driver to unload below tuning than a port? Ilkka, anything preliminary you can share?

I don't believe this is the case. Of course I can't be 100% sure because I was using a HP filter during the GP session.

But I did notice that the measured frequency response doesn't match the simulated response as well as with the 270L LLT I measured earlier. The LMS/PR starts to roll-off sooner than the simulation shows, as if the Qmp of the PR's was really low (around 1). The -6 dB (+/- 3 dB) frequency for the LMS/PR was around 18.5 Hz. And this was without any HP filters/EQ. The measured tuning frequency was 16.1 Hz. The LLT did ~13.5 Hz (-6 dB) with a 16.5 Hz tuning. I'm thinking 200 liters is too little for the LMS/PR combo. Something around 250-300 liters should boost that low end quite nicely.

**noah katz** · **11-02-07, 06:22 PM**

"Here's the FOTP scene you mention. I doubt the <15 Hz material is strong enough to make the active driver bottom out. If it bottoms out, it is caused by the 25-30 Hz material instead."

I seem to have forgotten how to read these graphs, or maybe I never knew.

I thought the SPL level was represented by color, in which case there's a high level just above 10 Hz.

But what does the vertical axis represent? If it's SPL, then what does color represent?

**jmcomp124** · **11-02-07, 06:30 PM**

Quote:

Ilkka wrote:

I don't believe this is the case. Of course I can't be 100% sure because I was using a HP filter during the GP session.

But I did notice that the measured frequency response doesn't match the simulated response as well as with the 270L LLT I measured earlier. The LMS/PR starts to roll-off sooner than the simulation shows, as if the Qmp of the PR's was really low (around 1). The -6 dB (+/- 3 dB) frequency for the LMS/PR was around 18.5 Hz. And this was without any HP filters/EQ. The measured tuning frequency was 16.1 Hz. The LLT did ~13.5 Hz (-6 dB) with a 16.5 Hz tuning. I'm thinking 200 liters is too little for the LMS/PR combo. Something around 250-300 liters should boost that low end quite nicely.

My box is larger (I think around 240, I have to go back and check) and yes I agree the larger the better for that lower end.

**Ilkka** · **11-02-07, 06:32 PM**

Quote:

noah katz wrote:

"Here's the FOTP scene you mention. I doubt the <15 Hz material is strong enough to make the active driver bottom out. If it bottoms out, it is caused by the 25-30 Hz material instead."

I seem to have forgotten how to read these graphs, or maybe I never knew.

I thought the SPL level was represented by color, in which case there's a high level just above 10 Hz.

But what does the vertical axis represent? If it's SPL, then what does color represent?

The vertical axis represents time. The scene/time rolls from top to bottom. Colour represents the SPL; dark red/pink being the highest.

Yes, there is a fairly strong signal around 11 Hz, but I don't believe it could bottom the driver at RL even if a 16 Hz HP filter would be used.

**Ilkka** · **11-02-07, 06:33 PM**

Quote:

jmcomp124 wrote:

My box is larger (I think around 240, I have to go back and check) and yes I agree the larger the better for that lower end.

Yes, your boxes are sightly larger (mine is around 210 liters to be exact) but I doubt that makes a difference regarding the HP filter/bottoming out.

**noah katz** · **11-02-07, 06:39 PM**

Ah, right, thanks Ilkka.

**jmcomp124** · **11-02-07, 06:46 PM**

Quote:

Ilkka wrote:

1. At the moment I'm not using any HP filter. During the GP session I used a 20 Hz 2nd order BW high pass filter (the lowest the DCX2496 allows). But I added a low-Q boost at 20 Hz so it became an effective ~16 Hz filter. I didn't bottom out the active driver or the PRs (well you can't really bottom out them).

2. I haven't yet tried those scenes with this sub. I will try them and report back. Though I'm not sure if I'm able to push this sub up to its limits. Remember that I live in an apartment.

3. My room is really small, only around 1500 cu ft and open (regular doorway) to ~2500 cu ft.

Here's the FOTP scene you mention. I doubt the <15 Hz material is strong enough to make the active driver bottom out. If it bottoms out, it is caused by the 25-30 Hz material instead. Also the WOTW chapter5 doesn't have that much strong sub-15 Hz material. All the really loud stuff is higher.

Thanks for this info, Ilkka.
I recall the scene that made me move the HP filter higher. It was the "Exploding THX ball before the intro in Star Wars:Phantom Menace". A waterfall chart like what you did for the FOTP scene, on this one would be great! Can you?
This scene caused one of the subs to bottom out. It was not a hard bottom thankfully and the driver survived. I noticed a couple of things was not set correctly/as desired. First, the right sub (I have two), had the HP filter in the CE4K set to 30Hz (negligence on my part). Second, the pre-amp was set to post-process to Dolby Pro-logic II, since I have 7.1, it shoudl have been Thx Ultra2 on the AVM-20. Also, the HP filter on the Rane was set to 16Hz.
As I recall, the left sub bottomed out. I was playing at MV0 and the subs were calibrated +6dB hot.
Immedietly thereafter, I fixed the 2 issues (bypassed the filter on the CE4K and set the Anthem pre to do the correct post processing, Thx Ultra2) and then I moved up the PE-17 up a notch to 20Hz.
Though the post processing was not the desired one and though the second sub had it's HP filter set to 30Hz, the bottom out made me very uncomfortable with the 16Hz filter. Ever since recalibration. I have yet to bottom out the subs.
Last night I video taped the cone and PR excursion for the FOTP scene. It does not look like neither the driver nor the PR is nearing peak. I will try to post the video, this weekend.

**Ilkka** · **11-02-07, 07:01 PM**

Quote:

jmcomp124 wrote:

Thanks for this info, Ilkka.
I recall the scene that made me move the HP filter higher. It was the "Exploding THX ball before the intro in Star Wars:Phantom Menace". A waterfall chart like what you did for the FOTP scene, on this one would be great! Can you?

Sure I can (I had these in my archive). It's a tough scene with wide bandwidth of material. Definitely more stronger sub-15 Hz signal than the FOTP scene.

Quote:

First, the right sub (I have two), had the HP filter in the CE4K set to 30Hz (negligence on my part).

Wow, that is a pretty bad "mistake".

Quote:

Last night I video taped the cone and PR excursion for the FOTP scene. It does not look like neither the driver nor the PR is nearing peak. I will try to post the video, this weekend.

Looking forward to that video.

**jmcomp124** · **11-02-07, 07:18 PM**

Quote:

Ilkka wrote:

Sure I can (I had these in my archive). It's a tough scene with wide bandwidth of material. Definitely more stronger sub-15 Hz signal than the FOTP scene.

Wow, that is a pretty bad "mistake".

Looking forward to that video.

You are one incredible guy

Thanks for that chart!

**jmcomp124** · **11-02-07, 10:18 PM**

Ok folks,
I thought I would push it to the limits, so I calibrated my subs +3dB hot and played the same FOTP at reference level and "HOOOOLY COW" it was 121.5dB at LP this time!!.
It felt like the building was going to collapse and the floor was about to cave in. I don't know how to describe this

. After all these months, these subs continue to surprise me.
I am not going to push them anymore. Period. I don't want to lose them. They sound so incredibly good.
I video taped this too! So stay tuned. I think these suckers still have some more headroom left.
If I move that slider down to 16Hz, am I going to feel something more than what I get now. I don't think so. So the slider in the Rane will remain at 20Hz. I know this will annoy and disappoint some of you. But that is where I stand at least for now. Happy man here. Buy that LMS

.
Keep in mind, my room is very large and very very difficult to pressurize. At 17ft away from the subs, getting more than 120dB is simply incredible. There are 2 subs though. I wish TC would revert back to the original price so more folks can enjoy. Very distressing. This thing is a DIY dream, I hate it when it is destroyed with overpricing. I want more folks to enjoy this. I really do. TC are you listening?
Ilkka you are a lucky man to own these. Aren't you glad you pursued on this?

. And thank you for being a part of my decision on these awesome drivers and design.
I may sound hyper, but th

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