GR Research Open Baffle Dipole Subwoofers

[marcl]

I'm starting this thread to document my next project, adding two GR Research Open Baffle Dipole Subwoofers to my system.  Each will be built with three of GR's SW-12-16FR 12" servo drivers, and one Rythmik A370PEQ servo plate amp, open baffle version.

The cabinets will be built locally rather than shipping flat packs from TX to PA.  The design is from GR's H-frame plans with two forward drivers and one reverse.

Since the drivers and cabinet will likely be ready a couple weeks in advance of the plate amps shipping (due to Rythmik folks being out of town 2-3 weeks) I'll take the opportunity to do the mounting and wiring of the drivers into the cabinets, and then do some testing with a conventional amp and no servo just to see how they behave.  I hope to do some somewhat "free-field" testing in the back yard, and then try some position experiments in my room.  Conventional thinking is to stand them on either side of the front speakers (Magnepan 3.7) ... but me being me, I will also test them laying on the floor end to end between the Maggies.  To that end I'll likely have the top and bottom made flush with the sides.

Drivers arrive tomorrow and with some luck maybe the cabinets will be done within a week.   More to come ...

[Boomzilla]

I'm MOST interested in the outcome of this. Open baffle speakers, I've heard. Open baffle subs? Not. When done, send us some photos of placement(s), please. Thanks - Boom

[marcl]

Apr 17, 2024 12:25:10 GMT -5 Boomzilla said:

I'm MOST interested in the outcome of this. Open baffle speakers, I've heard. Open baffle subs? Not. When done, send us some photos of placement(s), please. Thanks - Boom

I certainly will document it all with photos and measurements.  Part of my goal here is to answer all the questions I have had for several years ... questions that I have searched the inter-tubes to answer and mostly came up dry.  One guy on Planar Speaker Asylum has done extensive prototyping and testing, and has a new design he's working on.

I heard dual 12" versions with conventional drivers and amps at CAF last year and as soon as I entered the room I felt something was different from other rooms ... then I saw four of them.  At CAF and AXPONA there were a couple companies showing complete speakers with the bass being handled by several drivers in OB dipole configurations.  And of course I heard Magnepan's prototype with 8 6 1/2" drivers.

[marcl]

Test Ideas … there will undoubtedly be more!

- Which settings produce the maximum bass extension (hopefully to 16Hz) and fastest impulse response?
- Does distortion ever become excessive?
- What (if any) are the tradeoffs?

One Sub
Measure frequency (amplitude) and impulse response, distortion and decay – outdoors and indoors; 3ft and 7ft; vertical and horizontal.
1. Standard amplifier (no servo or EQ)
2. Standard amplifier with miniDSP EQ (no servo) – parameters TBD
3. Servo amplifier (no servo or EQ)
4. Servo amplifier, all combinations:
        a. Extension 14, 28, 20
        b. Damping Low, High, Mid
        c. PEQ peak resonance correction

Two Subs (Mono)
Measure frequency (amplitude) and impulse response, distortion and decay – outdoors and indoors; 3ft and 7ft; vertical (5.5ft apart) and horizontal (end to end).
1. Standard amplifier (no servo or EQ)
2. Standard amplifier with miniDSP EQ (no servo) – parameters TBD
3. Servo amplifier (no servo or EQ)
4. Servo amplifier, all combinations:
        a. Extension 14, 28, 20
        b. Damping Low, High, Mid
        c. PEQ peak resonance correction
        d. Delay/Phase 0-180

Other ideas are welcome!

[Boomzilla]

The ROOM RESPONSE of your subs will vary wildly depending on placement. Once you’ve selected locations for the two in your room, I’d be interested to see the frequency response curves for each individually as well as the combined output as measured from the listening position.

I’ve chosen, in the past to equalize the subs individually for maximum flatness lest one sub or the other become prominent at specific frequencies.

[marcl]

Apr 17, 2024 20:57:53 GMT -5 Boomzilla said:

The ROOM RESPONSE of your subs will vary wildly depending on placement. Once you’ve selected locations for the two in your room, I’d be interested to see the frequency response curves for each individually as well as the combined output as measured from the listening position.

I’ve chosen, in the past to equalize the subs individually for maximum flatness lest one sub or the other become prominent at specific frequencies.

For sure!  I have a lot of experience (12 years!) dragging my 3.7 and DWM combinations around and bass response from those will vary quite a bit, with the odd deep cancelation popping up (down?) with certain placements.  And that's why I hope to do an outdoor test to get a baseline of how they behave individually and together.

Once in the room I expect to run them mono.  I'll start with my current configuration which is to use Center Sub=LFE to get the LFE to a miniDSP, and the low outputs of my front channel active crossovers to get a summed L/R bass below 50Hz to the miniDSP.  I do bass management with the fronts so that's how the lows from the small speakers eventually get to the subs.  In the miniDSP I have the ability to do separate EQ and time alignment for the two subs, but I'll start with just letting the signals pass through and use the EQ and phase controls on the plate amps.  I will probably experiment with raising the L/R crossovers to 60 or 70Hz.  And of course Dirac to polish it all off once I settle the physical options.

My hypothesis is I will end up here with placement ... on the floor, playing L+R+LFE in mono, 7' from the MLP.

[Boomzilla]

Should you find a really good sub location in the room, consider vertically stacking the subs! Remember that your listening space is THREE dimensional - not two. I once stacked a pair of Powersound Audio 18” subs in my room. I then played a “Dead Can Dance” track, “Yulunga,” for my audio amigo, garbulky. I swear that he broke out in goosebumps or something when the drums kicked in…. The stacked subs sounded awesome!

[marcl]

Apr 18, 2024 5:33:01 GMT -5 Boomzilla said:

Should you find a really good sub location in the room, consider vertically stacking the subs! Remember that your listening space is THREE dimensional - not two. I once stacked a pair of Powersound Audio 18” subs in my room. I then played a “Dead Can Dance” track, “Yulunga,” for my audio amigo, garbulky . I swear that he broke out in goosebumps or something when the drums kicked in…. The stacked subs sounded awesome!

Like this?  80" high? Only ttocs would attempt such a thing!  

"Conventional" thinking would be to stand one on each side (40" high), inboard of the 3.7 around 2-3ft from the side wall and 6-7ft from the front wall.  In my Rooze arrangement of the 3.7 I have extended the baffle forward 2ft with 1" thick boards screwed to the end trim holes, so placing each sub against this extended baffle also extends the baffle length of the sub quite a bit on one side.  But laying the subs down on the floor as shown in my earlier post creates a very extended baffle in both directions on the side laying on the concrete floor.  It also puts the ceiling in the null, as well as the side walls.  I'm looking for maximum effective baffle length and minimum modal resonance excitement.

[ttocs]

Apr 18, 2024 3:21:18 GMT -5 marcl said:

My hypothesis is I will end up here with placement ... on the floor, playing L+R+LFE in mono, 7' from the MLP.

I'm keenly interested to know how the horizontal array arrangement performs in your proposed ending location vs against the front wall, or somewhere closer to the front wall being that these are open baffle. Even a distance difference of 6' closer to the front wall should prove to be more than enough to show how the front wall interacts with them.

It's the SBIR that I'm wondering about here. Or, does open baffle help with SBIR in some way?

[Boomzilla]

Apr 18, 2024 6:15:54 GMT -5 marcl said:

Apr 18, 2024 5:33:01 GMT -5 Boomzilla said:

Should you find a really good sub location in the room, consider vertically stacking the subs! Remember that your listening space is THREE dimensional - not two. I once stacked a pair of Powersound Audio 18” subs in my room. I then played a “Dead Can Dance” track, “Yulunga,” for my audio amigo, garbulky . I swear that he broke out in goosebumps or something when the drums kicked in…. The stacked subs sounded awesome!

Like this?  80" high? Only ttocs would attempt such a thing!   …

“ONLY ttocs???” - I thought you knew me better by now - LOL

[marcl]

Apr 18, 2024 7:49:23 GMT -5 Boomzilla said:

Apr 18, 2024 6:15:54 GMT -5 marcl said:

Like this?  80" high? Only ttocs would attempt such a thing!   …

“ONLY ttocs ” - I thought you knew me better by now - LOL

Yeah and seeing my room diagram you know nothing is too crazy to try!

[marcl]

Apr 18, 2024 7:31:32 GMT -5 ttocs said:

Apr 18, 2024 3:21:18 GMT -5 marcl said:

My hypothesis is I will end up here with placement ... on the floor, playing L+R+LFE in mono, 7' from the MLP.

I'm keenly interested to know how the horizontal array arrangement performs in your proposed ending location vs against the front wall, or somewhere closer to the front wall being that these are open baffle. Even a distance difference of 6' closer to the front wall should prove to be more than enough to show how the front wall interacts with them.

It's the SBIR that I'm wondering about here. Or, does open baffle help with SBIR in some way?

My thinking is to start with two principles:  Room modes are excited the least by placing the sub 25% from the front and side walls; and dipoles want to be at least 5.5ft from the front wall.  I proved the former many years ago by moving my (10" ported Outlaw) sub around in that range 3ft from the side and 6 1/2 ft from the front.  My initial vertical placement of these will be at those spots left and right.  My hypothesis on the horizontal position has to do with the baffle effect, and I would have the array 6 1/2ft from the front wall.

And a guy I correspond with from Planar Asylum who has built these OB dipoles and others and did extensive testing ... said performance was better laying down.

I'm researching SBIR more ... but I have read OB dipoles are less prone to the effects.

[fbczar]

Apr 18, 2024 8:10:23 GMT -5 marcl said:

Apr 18, 2024 7:31:32 GMT -5 ttocs said:

I'm keenly interested to know how the horizontal array arrangement performs in your proposed ending location vs against the front wall, or somewhere closer to the front wall being that these are open baffle. Even a distance difference of 6' closer to the front wall should prove to be more than enough to show how the front wall interacts with them.

It's the SBIR that I'm wondering about here. Or, does open baffle help with SBIR in some way?

My thinking is to start with two principles:  Room modes are excited the least by placing the sub 25% from the front and side walls; and dipoles want to be at least 5.5ft from the front wall.  I proved the former many years ago by moving my (10" ported Outlaw) sub around in that range 3ft from the side and 6 1/2 ft from the front.  My initial vertical placement of these will be at those spots left and right.  My hypothesis on the horizontal position has to do with the baffle effect, and I would have the array 6 1/2ft from the front wall.

And a guy I correspond with from Planar Asylum who has built these OB dipoles and others and did extensive testing ... said performance was better laying down.

I'm researching SBIR more ... but I have read OB dipoles are less prone to the effects.

I would assume your new OB subs will have few , if any SBIR issues, just like your Magnepan’s. However, two drivers to the front and one to the back may not provide near total cancellation like you get with the Maggie’s. Of course, the wave from the backs of the drivers may be about the same as the wave from the front and cancellation at the sides, booth and tops of the subs may be near 100%. In my room SBIR became a non-issue with my Magnepan’s vs my TDL reference Standards.

[405x5]

Over the top “help” for Magnepans?

[marcl]

As I was modifying the plans a bit to send to Harry, the speakers were delivered.  Three 43lb boxes!  Fedex like to put things close to the door like that 

[marcl]

Modified plans slightly, to just have a flush top and bottom so I can stand them up or lay them down.  I have some spike plates coming which I'll use for more stability once I decide orientation.  Also going to have Harry drill the mounting holes for the speakers because after looking at the plans I don't think I could get a drill in there to make straight holes.

[405x5]

Apr 18, 2024 10:47:03 GMT -5 marcl said:

As I was modifying the plans a bit to send to Harry, the speakers were delivered.  Three 43lb boxes!  Fedex like to put things close to the door like that 

View Attachment

FedEx handling such precious cargo lucky everything got there intact I assume

[marcl]

Apr 18, 2024 10:22:55 GMT -5 fbczar said:

Apr 18, 2024 8:10:23 GMT -5 marcl said:

My thinking is to start with two principles:  Room modes are excited the least by placing the sub 25% from the front and side walls; and dipoles want to be at least 5.5ft from the front wall.  I proved the former many years ago by moving my (10" ported Outlaw) sub around in that range 3ft from the side and 6 1/2 ft from the front.  My initial vertical placement of these will be at those spots left and right.  My hypothesis on the horizontal position has to do with the baffle effect, and I would have the array 6 1/2ft from the front wall.

And a guy I correspond with from Planar Asylum who has built these OB dipoles and others and did extensive testing ... said performance was better laying down.

I'm researching SBIR more ... but I have read OB dipoles are less prone to the effects.

I would assume your new OB subs will have few , if any SBIR issues, just like your Magnepan’s. However, two drivers to the front and one to the back may not provide near total cancellation like you get with the Maggie’s. Of course, the wave from the backs of the drivers may be about the same as the wave from the front and cancellation at the sides, booth and tops of the subs may be near 100%. In my room SBIR became a non-issue with my Magnepan’s vs my TDL reference Standards.

I'm watching an Audioholics YouTube again about SBIR .... Gene, Poes and Grimani.  I don't recall them talking about open baffle but it's a good refresher.  So far it seems confirmed that even with conventional subs, moving away from the wall can solve a lot some issues, unless the cancellation is much above 100Hz ... in which case closer to the wall and with absorption would help.  But I can easily put them 6-7ft from the front wall.

[marcl]

[garbulky]

Apr 18, 2024 5:33:01 GMT -5 Boomzilla said:

Should you find a really good sub location in the room, consider vertically stacking the subs! Remember that your listening space is THREE dimensional - not two. I once stacked a pair of Powersound Audio 18” subs in my room. I then played a “Dead Can Dance” track, “Yulunga,” for my audio amigo, garbulky. I swear that he broke out in goosebumps or something when the drums kicked in…. The stacked subs sounded awesome!

yep. they were psa 15 vented. their sealed 18" you had was also very nice