[RedmundjBeard]

Hello, I'm sure these question have already been asked but I can't seem to search the forum.

I would like to build an open baffle servo sub and would appreciate any impressions people have of the H style vs the W. I assume the W is better but the H is easier to build?

Has anyone built one of the these and could tell me their upper cutoff frequency? GR's website says how low they can go but do they sound good going up past 100Hz? Ideally I would like to go to 130 to mate with a 12inch woofer. They plate amp appears to go up to 120Hz, but do they servo subs sound good up there? Are they more of a 20-60Hz deal?

I have an active crossover, so I already have a -28db/decade low pass going into a 180 watt class D amp w/ rumble filter high pass at 17Hz. Are the plate amps that GR sells special in any way or do they just have the crossover built in and more power?

Thank you for your time,
red

Servo Sub
http://gr-research.com/sw-12-16fr.aspx

H frame
http://www.gr-research.com/pdf/H-frame%202.pdf

W frame
http://www.gr-research.com/pdf/obsub.pdf

12 inch woofers I am trying to decide between if you are wondering
https://www.madisoundspeakerstore.com/pro-sound/audax-pr330m0-13-professional-woofer/
https://www.parts-express.com/aurum-cantus-ac300-75c2c-12-woofer--296-458
https://www.midwestspeakerrepair.com/shop/home-audio/woofers/mw-audio-1/mw-audio-oc12wf-8b-12-inch-woofer/

[jimbones]

I built the H Frames and they go up to about 110 maybe 125

[Danny Richie]

I would like to build an open baffle servo sub and would appreciate any impressions people have of the H style vs the W. I assume the W is better but the H is easier to build?

Nothing is better about the W frame other than it is shorter. It also leaves a little larger unbraced panel area on the front side. So side panels need to be made a little thicker.

Has anyone built one of the these and could tell me their upper cutoff frequency? GR's website says how low they can go but do they sound good going up past 100Hz?

We've crossed them as high as 300Hz, but 200Hz and down is really the sweet spot. Above that starts getting into the lower mids and should be handled by your main speakers.

Ideally I would like to go to 130 to mate with a 12inch woofer. They plate amp appears to go up to 120Hz, but do they servo subs sound good up there? Are they more of a 20-60Hz deal?

Keep in mind that the numbers on the plate amp are references for electrical slopes. They are not -6db down points. And crossing them in the 180Hz to 200Hz region usually requires a setting on the dial in the 90Hz to 100Hz range.

I have an active crossover, so I already have a -28db/decade low pass going into a 180 watt class D amp w/ rumble filter high pass at 17Hz. Are the plate amps that GR sells special in any way or do they just have the crossover built in and more power?

Yes, very special. They use the Rythmik Audio patented servo control technology. There is nothing else like it.

12 inch woofers I am trying to decide between if you are wondering
https://www.madisoundspeakerstore.com/pro-sound/audax-pr330m0-13-professional-woofer/
https://www.parts-express.com/aurum-cantus-ac300-75c2c-12-woofer--296-458
https://www.midwestspeakerrepair.com/shop/home-audio/woofers/mw-audio-1/mw-audio-oc12wf-8b-12-inch-woofer/

None of those are really suited for open baffle applications.

[Tyson]

I have dual 12 GR Research OB subs and they'll go up to 250 hz in my setup. 

[RedmundjBeard]

Thanks for the replies everyone, exactly what I was looking for.

My 12 inch woofer for 100ish to 650ishHz will just be sealed.

[jimbones]

I have dual 12 GR Research OB subs and they'll go up to 250 hz in my setup.

Ive been told they go that high, I just dont see it I have the same woofers but I am using the A370 amp. Unless that is limiting it to 125.

[Danny Richie]

Ive been told they go that high, I just dont see it I have the same woofers but I am using the A370 amp. Unless that is limiting it to 125.

You must have missed what i just said in my last post.

"Keep in mind that the numbers on the plate amp are references for electrical slopes. They are not -6db down points. And crossing them in the 180Hz to 200Hz region usually requires a setting on the dial in the 90Hz to 100Hz range."

[emailtim]

I had similar questions.  Using the 370 amp, this is as high as I could get without resorting to a different amp, XO and DSP.

[Captainhemo]

Are you  using the  AVR/12 slope  ?

jay

[mlundy57]

Are your A370 amps connected to an AVR and if so, is the AVR's bass management/room correction turned on?

[emailtim]

Are you  using the  AVR/12 slope  ?

jay

The plot I posted is of both the 80/20 and the AVR/12 settings with the XO dial rotated clockwise as high as it will go.  Neither setting got me there, so I am currently using a different XO and amp to get there.  I would like to defeat the XO in the 370 amp entirely if possible to retain the servo functionality.

Are your A370 amps connected to an AVR and if so, is the AVR's bass management/room correction turned on?

I have this version of the plate amp with no LFE support.  My DRC, XO and filters are done in the PC.  The external XO was set at a LR 200Hz/48dB low pass.

[mlundy57]

For the sub's crossover control to go higher, you have to send the A370 amp a high enough frequency signal. If there is any processing that limits the signal to the sub too much, the sub won't be able to play as high as you want. In my open baffle system, where the subs need to play up to 200Hz, depending on the monitor I'm using, I send a full range signal to the A370 amp then use the sub's crossover control to blend with the monitors.

Try setting the external crossover to the sub to at least 400Hz, or send a full range signal until you determine what frequencies you need to send the sub to get the blend you want.

[emailtim]

Try setting the external crossover to the sub to at least 400Hz, or send a full range signal until you determine what frequencies you need to send the sub to get the blend you want.

I hear what you are saying.  Here it is with and without the plate amp (but a digital shelf).  It appears it has plenty of signal to work with.  Also, I don't want 2 XO's competing with each other (shelves, phase and cutoffs), so a LFE version that defeats the XO would be a better option for this application.

[mlundy57]

I hear what you are saying.  Here it is with and without the plate amp (but a digital shelf).  It appears it has plenty of signal to work with.  Also, I don't want 2 XO's competing with each other (shelves, phase and cutoffs), so a LFE version that defeats the XO would be a better option for this application.

The A370PEQ3 has LFE inputs that defeat the sub’s crossover as well as line level inputs

[HAL]

The Rythmik Audio A370PEQ does not have LFE inputs, where the A370PEQ3 has LFE inputs.  You would need the shelving filter with the A370PEQ to make it act like the A370PEQ3.   

The A370XLR3 would work as well with both RCA and XLR inputs as it has LFE inputs.   

[emailtim]

FWIW, here is the integration.

Low and High Pass individually:


Low and High Pass together:

[Danny Richie]

Using the A370PEQ amp I was easily able to get a crossover point as high as 300Hz.



You may have some room issues knocking out the output in that upper area.

And like Hal said, if you want to run them up even higher then you can use the A370PEQ3 amp with it's LFE input.

[emailtim]

Using the A370PEQ amp I was easily able to get a crossover point as high as 300Hz.



You may have some room issues knocking out the output in that upper area.
...

If the "room issues" are knocking out the upper area, it should probably also knock out that area when using an external XO at 200Hz and 250Hz, but it doesn't.  I will try it again with a full range signal.

Danny, what settings are you using to get this ? 

The slope appears to be at least 18dB or 24dB/octave.  Also, your lowest peak looks different than mine.  Mine comes out pretty flat to @ 40Hz without additional DSP.

[Danny Richie]

If the "room issues" are knocking out the upper area, it should probably also knock out that area when using an external XO at 200Hz and 250Hz, but it doesn't.  I will try it again with a full range signal.

Danny, what settings are you using to get this ? 

The slope appears to be at least 18dB or 24dB/octave.  Also, your lowest peak looks different than mine.  Mine comes out pretty flat to @ 40Hz without additional DSP.

Mine was an in room response from the listening position.

I had the crossover point turned all the way up and it was on the 12db per octave setting.

[emailtim]

I think I eliminated the "Room Effects" and also eliminated the "250Hz versus Full Range Effects" with the following test results leaving me to think the XO in my 370 is really as silk screened [25Hz-120Hz] and not [25Hz-240Hz] as suggested.

First, eliminate the 250Hz versus Full Range assumptions:

• The GOLD is the AVR/12 - 120Hz with an external 250Hz/48dB XO with some slight external XO gain.
• The GREEN is the AVR/12 - 120Hz without the external XO and slight gain, straight from DAC output, full range.

Note: No change in HF rolloff other than the slight additional XO gain.

Second, eliminate the "room effect assumptions".

The BLUE is full range with an external amp and SW low shelf filter.
The PURPLE is full range with an external amp, no low shelf filter, no DSP at all.

Note: Both extend upwards of 600Hz with a resonance spike @ 210Hz.  No HF room cutoff.

Note: All 3 with either a HW low shelf or SW low shelf have a relatively flat initial peak from [14Hz-40Hz].



Now that the "room effects" and "additional steep 250Hz XO effects" have been eliminated, it looks like my version of the 370 plate amp's XO rotary function is really [25Hz-120Hz] versus [25Hz-240Hz].

Here are the full range 25Hz -50/80/AVR12 and 120Hz 50/80/AVR12 settings.  The XO knees all appear earlier than expected compared to using an external XO.



The only other explanation that I have is that I created my SW low shelf filter specific to my application where the one in the Rythmik Servo amp is general purpose.