Sub Integration

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poseidonsvoice

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Re: Sub Integration
« Reply #20 on: 25 Apr 2019, 12:06 pm »
I haven’t digested the info on house curves yet, I’t’s all I can do to get ready for LSAF and my day job right now. I’ll spend more time reading up on this once things calm back down. 

What I’ve read so far looks interesting but I’m not sure how to accomplish any of them. I can boost the bass easy enough but since top end is passive it seems like it is what it is.

Mike

Top end is intrinsic to the design of the speaker. It’s the reason constant and controlled directivity are important points of discussion  as the designer of said speaker takes that into consideration.

Best,
Anand.

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Re: Sub Integration
« Reply #21 on: 25 Apr 2019, 04:43 pm »
I believe most speakers roll off at the top at least a little bit just due to being in a room, unless the room is totally undamped. The problem is for digital systems run through SW programs like JRiver that allow equalization. The temptation is to make the system measure flat. If you do, in most cases it will sound way too bright.

emailtim

Re: Sub Integration
« Reply #22 on: 28 Apr 2019, 04:49 am »
FWIW, Here is a recent REW plot (1/24 octave smoothing, Cross Spectrum Calibrated USB Mic) of some OB subs mated to Magnepan 20.1 bass panels measured at 5 feet. 

LP/HP XO point is at 40Hz 48db (black vertical line).  Note the flat line to the left of the 40Hz line.

2 - 12" subs are in stacked cabinet configuration similar to the Orion 4's. 

Both drivers are facing up, stacked on top of each other, but firing out of phase to average driver travel non-linearity, center driver weight and cancel cabinet resonances.  There is one larger "port" in the front and 2 smaller "ports" in the back.

On other tests in this cabinet configuration with a higher XO point, it remains significantly flat to @ 55Hz which is good for my application, but not if you are wanting to drive them higher into the woofer range.  Adding a notch filter past 55Hz extended its range a bit.

The top plot is done with a PEQ370 amp and the bottom plot is done with an ICEPower ASP1000 amp using a software Low Shelf Filter.



Settings on the PEQ370 are:
  • Dampening: High
  • Rumble Filter: ON
  • Phase: 0
  • AVR-12 - Using external XO
  • Volume: minus 5 clicks from 12 O'Clock
  • Bass Extension: 14Hz
  • No PEQ

REW and multiple overlayed measurement plots was very helpful in determining the optimal PEQ370 settings for bass extension, phase matching, level matching and minimized distortion.  Using an SPL meter and my ears would have resulted in less than optimal results.

Update: Image of cabinet configuration:
« Last Edit: 28 Apr 2019, 08:47 pm by emailtim »

poseidonsvoice

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Re: Sub Integration
« Reply #23 on: 28 Apr 2019, 02:35 pm »
emailtim,

Thanks for contributing with your personal measurements. Nice extension to 15hz.

What would be your solution(s) for the area to the right of the 40Hz line, ie 40Hz to 250Hz or so?

Best,
Anand.

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Re: Sub Integration
« Reply #24 on: 28 Apr 2019, 03:29 pm »
emailtim





emailtim

Re: Sub Integration
« Reply #25 on: 28 Apr 2019, 03:54 pm »
emailtim,

Thanks for contributing with your personal measurements. Nice extension to 15hz.

...

Best,
Anand.

Poseidonsvoice,

I was surprised to see how "flat" the sub response was in that cabinet but higher frequency range extension seems to be limited.  I could get a few more Hz bass extension if I disabled the Rumble Filter, but REW indicated the distortion measurements went up accordingly so I left it off.  Someone more knowledgeable of cabinet and driver characteristics could probably come up with more optimized cabinet dimensions than what I did.   I measured it both in the garage when making the cabinet and then in the house.  I have some 1.5" MDF laminated up and am ready to make some H-Frames out of them to test next.  Have to make a router dado jig first.  Wish I had access to a nice CNC.

... What would be your solution(s) for the area to the right of the 40Hz line, ie 40Hz to 250Hz or so? ...

I don't exactly understand your question.  The area to the right is the actual response of both planar bass panels including the room response measured at 5 feet.  This will change as you move the mic around the room.  Smoothing is set at 1/24 and the plot is zoomed in so it is showing a lot of the warts.  If I set the smoothing to 1/12, 1/6th, 1/3rd, ... the plots flatten out more.  I have not tried to create any PEQs for the rest of the plot yet. 

As for strategy, I would try to understand what are causing the specific anomalies (furniture, location, reflection, room mode, etc.).  Fixing the cause is usually better than resorting to a PEQ because it usually fixes the anomaly in all locations of the room and not just the mic location.  I have noticed you have to examine multiple smoothing settings in REW analysis because a given "smoothing plot setting" may give you a false impression that is an artifact of the smoothing algorithm else you will start chasing ghosts under the microscope.

I measured the drivers by themselves and together to see where the rolloffs, summing and cancellations of the XO were.  This is also how I determined the best phase settings. 

The XO is at 40 Hz and the slopes are symmetric at 48dB/octave.  That means drivers would be down 48dB at 20Hz and 80Hz (off the bottom of this plot at 20Hz and 80Hz).  It also means the phase of both drivers should match after going through both XO with the 48dB slopes (providing their starting phase is the same).


emailtim

Re: Sub Integration
« Reply #26 on: 30 Apr 2019, 01:36 am »
emailtim,

Thanks for contributing with your personal measurements. Nice extension to 15hz.

What would be your solution(s) for the area to the right of the 40Hz line, ie 40Hz to 250Hz or so?

Best,
Anand.

PoseidonsVoice,

FWIW, here is the same plot with 1/3rd octave smoothing versus 1/24th octave smoothing.  I don't know if there is a "standard/customary" smoothing value to be used when posting plots here.


Danny Richie

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Re: Sub Integration
« Reply #27 on: 1 May 2019, 03:24 pm »
Hey Chuck,

I got your message on this, but also noticed the post you made here so I figured I'd let some others give their feedback first, and then I have been so busy getting ready for the show that I haven't gotten back to it yet.

Ideally you need to take some measurements to dial it in perfectly.

The number one error in measuring them is everyone tries to measure left and right speakers and subs at the same time. This just causes cancellation effects from different distances and time delays created by multiple sources. Just measure left speaker and left sub individually and then together to get the phase, crossover, and amplitude correct.

The damping settings will have an effect on imaging to some extent. Don't assume that high just means tighter or better control and thus better sound. You may get better sound on low damping if the extension filter is set low, and better imaging.

And don't get caught up in trying to measure distortion figures. Measuring or trying to take any distortion measurements outside of an anechoic chamber is futile. The actual distortion numbers will be at or below the room noise level. So true data will be covered over by the room noise levels.

I'd also like to comment on implementing the servo woofers. I tend to prefer the H or W frame design. I like the H frame best as it divides the side panels into smaller areas and maintains a larger opening. The W frame leaves a much larger panel area on the front side between the drivers and the side panels have to be increased to thicker material to compensate for the pressure created in that area.

I'm using 1.25" think material on my H frames and lined with No Rez to eliminate and control any panel flexing and resonances, and that is about what it takes.

Going to a Ripole design like the one pictured unnecessarily loads the drivers and causes the amp to use more power to maintain the linear output levels. So it eats into amp headroom. It also will limit the upper range quite a bit. But more importantly is that it allows for very large panel areas in front of each driver. To do away with panel flexing and resonances that this alignment will cause will require panel thickness in the 2.5" to 3" thick range. Most of the designs I have heard using this alignment and 3/4" plywood is what I'd call a buzz box. So I don't recommend it.


emailtim

Re: Sub Integration
« Reply #28 on: 1 May 2019, 04:36 pm »
...

Going to a Ripole design like the one pictured unnecessarily loads the drivers and causes the amp to use more power to maintain the linear output levels. So it eats into amp headroom. It also will limit the upper range quite a bit. But more importantly is that it allows for very large panel areas in front of each driver. To do away with panel flexing and resonances that this alignment will cause will require panel thickness in the 2.5" to 3" thick range. Most of the designs I have heard using this alignment and 3/4" plywood is what I'd call a buzz box. So I don't recommend it.



Hi Danny,

FWIW, that is not a Ripole cabinet.  I believe it is called a "Linkwitz W-frame" according to the Subwoofer Origami page with drivers firing out of phase to null cabinet resonances/jumping (force cancellation) which an H-Frame cabinet does not do while averaging out the forward/backward driver movement characteristics and centers the driver weight to the middle of the cabinet.  https://www.hifizine.com/2012/12/subwoofer-origami/



This is supposed to be a RIPOLE (matches patent) with facing drivers firing in phase much closer together and much smaller cabinet volumes (loading the drivers as you mentioned) (motors/magnets protruding out the sides).



The Subwoofer Origami pages calls this an M-Frame (push-pull) which you refer to as a W-frame.



Is there a definitive reference on the cabinet naming conversions to avoid confusion ?  We know what a Ripole is because it was named after the inventor (Axel Ridtahler's DiPole) in his patent but there seems to be some ambiguity with the W and M frame naming conventions.

Danny Richie

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Re: Sub Integration
« Reply #29 on: 1 May 2019, 04:57 pm »
Ah, thanks for the correction of terminology.

The issues that I pointed out though still remain. There are still significant pressures in each area that flex and excite each panel. 

emailtim

Re: Sub Integration
« Reply #30 on: 1 May 2019, 05:15 pm »
Ah, thanks for the correction of terminology.

The issues that I pointed out though still remain. There are still significant pressures in each area that flex and excite each panel.

I would think the internal pressures of the Linkwitz W-Frame are less than a RiPole because the cavities and ports are much larger.

What are your impression of my first 1/24th octave plot with respect to the subs flat frequency response.  Is that typical for a H-Frame cabinet, or is it more of a hump.  Note, it has no EQ other than the Hardware/Software Low Shelf filters and the XO point.



P.S.

Also, why would you ignore distortion measurements ?  Isn't distortion the reason for using a Servo (to eliminate it) ?

Danny Richie

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Re: Sub Integration
« Reply #31 on: 1 May 2019, 06:30 pm »
I would think the internal pressures of the Linkwitz W-Frame are less than a RiPole because the cavities and ports are much larger.

It is less than the pressures of the Ripole, but still very extreme compared to an H frame.

Quote
What are your impression of my first 1/24th octave plot with respect to the subs flat frequency response.  Is that typical for a H-Frame cabinet, or is it more of a hump.  Note, it has no EQ other than the Hardware/Software Low Shelf filters and the XO point.

It looks good. I am surprised it isn't humped up more from the loading.

Quote
Also, why would you ignore distortion measurements ?  Isn't distortion the reason for using a Servo (to eliminate it) ?

Distortion measurements outside of an anechoic chamber are impossible to get any meaningful data from. Even the manual for my Clio measuring system states such. Since it is impossible to separate from the noise floor it has little value. And to be honest even taken correctly in a chamber the data is just a drop in the bucket compared to settling time and panel resonances. Those are 100 times greater and more significant. When you are laying power to these things and really moving the drivers pretty hard then those issues get real. And the servo system really speeds up settling times. Cabinet resonances have to be addressed in other ways.

Tyson

Re: Sub Integration
« Reply #32 on: 1 May 2019, 06:38 pm »
It is less than the pressures of the Ripole, but still very extreme compared to an H frame.

It looks good. I am surprised it isn't humped up more from the loading.

Distortion measurements outside of an anechoic chamber are impossible to get any meaningful data from. Even the manual for my Clio measuring system states such. Since it is impossible to separate from the noise floor it has little value. And to be honest even taken correctly in a chamber the data is just a drop in the bucket compared to settling time and panel resonances. Those are 100 times greater and more significant. When you are laying power to these things and really moving the drivers pretty hard then those issues get real. And the servo system really speeds up settling times. Cabinet resonances have to be addressed in other ways.


Speaking of settling time - is that why the Neo10 panels sound so good?  Because they are driven by magnets from the front and rear simultaneously and thus have a much faster return (settle time) vs. a cone/spider setup?

Early B.

Re: Sub Integration
« Reply #33 on: 1 May 2019, 07:29 pm »
Danny -- for those of us who already have our servo subs built with only 3/4" MDF and would like to address the cabinet resonance issue, would it be helpful to add "decorative" wood or stone panels to the sides of our cabinets?

Danny Richie

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Re: Sub Integration
« Reply #34 on: 1 May 2019, 08:50 pm »
Danny -- for those of us who already have our servo subs built with only 3/4" MDF and would like to address the cabinet resonance issue, would it be helpful to add "decorative" wood or stone panels to the sides of our cabinets?

It sure would.

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Re: Sub Integration
« Reply #35 on: 2 May 2019, 01:40 pm »
Thanks, Danny

Ideally you need to take some measurements to dial it in perfectly.

I'll be taking REW measurements shortly

The number one error in measuring them is everyone tries to measure left and right speakers and subs at the same time. This just causes cancellation effects from different distances and time delays created by multiple sources. Just measure left speaker and left sub individually and then together to get the phase, crossover, and amplitude correct.

That's the sequence I was looking for: 1. phase; 2. crossover; 3. amplitude. Otherwise it's easy to chase your tail.

The damping settings will have an effect on imaging to some extent. Don't assume that high just means tighter or better control and thus better sound. You may get better sound on low damping if the extension filter is set low, and better imaging.

You're right: I had assumed that. I'll try messing around with damping.

And don't get caught up in trying to measure distortion figures. Measuring or trying to take any distortion measurements outside of an anechoic chamber is futile. The actual distortion numbers will be at or below the room noise level. So true data will be covered over by the room noise levels.

OK.

Regards,
Chuck