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Open baffle subwoofer - anybody?

ppataki

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I was just brainstorming with myself on a potential next DIY project and somehow the topic of open baffle subwoofers came into my mind :)

Is there anybody here who has actually done that? What is the experience compared to regular sealed or reflex subwoofers? Are there any in-room real-life measurements available?

A dummy design question: can I design/simulate open baffle subs just like how I would do sealed subs but instead of specifying the planned cabinet size I input there my room size? (67 000 liters in my case)

I was thinking about having 2x4 pieces of 15" OB subs in the front corners to begin with

I would appreciate any real-life experience comments
Thank you in advance
 
OB Subwoofer in the corners make no sense at all. The optimal place for OB Subwoofer is near listener, well out of wall.

Yes you can simulate OB speaker with your room size as box parameter.

OB have dipole characteristic in low frequencies, so it can not pressure the room below the first room mode. So depend on your room, the OB Subwoofer only work down to certain frequency. For my living room, it is around 28 Hz. So I use sealed subwoofers with 40 Hz low pass filter to assist my dipole speaker.
 
Yes, I have a pair of Caintuck W15 bass compensators (Lii Song drivers) that are paired with other open baffle speakers. These are used for music and work fine in that application.

Screenshot 2025-01-13 at 5.31.16 PM.png
 
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Is there anybody here who has actually done that? What is the experience compared to regular sealed or reflex subwoofers?
They are inefficient because the out-of-phase sound waves from the back "leak around" (or bounce off the walls) and cancel the waves from the front. The whole point of a box is to avoid that.

With enough big woofers you might "get-away" with it but you could almost certainly do better with a more traditional design.

I assume there is software that can simulate it but I've only used WinISD and it does not. :(

It's inexpensive to try, but no not so inexpensive if you want to build a cabinet version just to compare. ;)
 
I would go either infinite baffle subwoofer, or your normal sealed/ported enclosure.

There's likely a reason you can't find much on it, and I expect its because an open baffle subwoofer doesn't work very well.
 
I guess the best start for dipole woofers - and that includes real world implementations and measurements - is Siegfried Linkwitz.
The simplest approach is probably the H-frame construction.
You should not forget that Linkwitz was interested in recordings of classical music in the first place. If you are looking for use in bass heavy music or movies YMMV.

EDIT: This quote might give you an incentive ;) as you seem to aim for a similar effort.
I saw the H-baffle concept for the first time, constructed as two woofer towers with six 12" drivers each, with D=16", and placed against the side walls, at the home of Brian J. Elliott, Ph.D, Consultant in Electro-Acoustics, in Palo Alto, 1988. I had never heard bass reproduced so naturally before.
 
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They are inefficient because the out-of-phase sound waves from the back "leak around" (or bounce off the walls) and cancel the waves from the front. The whole point of a box is to avoid that.

Pretty sure even sealed and ported subwoofer boxes radiate bass in all directions. Google it.
 
Pretty sure even sealed and ported subwoofer boxes radiate bass in all directions. Google it.
I think you misunderstood. With open baffle the backwave is out of phase with the front wave and bounces around canceling out lower frequencies. The point of a box whether sealed or ported is to prevent that even using some of the back side energy. So you don't get that cancelation. So yes with a box it radiates in all directions. With an open baffle or no box, it does not. It is a dipole.
 
Pretty sure even sealed and ported subwoofer boxes radiate bass in all directions. Google it.
Speakers produce sound waves when they move outwards, but also do so equally when they move inwards. By nature, the inward-moving wave is 180 degrees out of phase with the outward-moving wave.

At low frequencies, any given wave will be omnidirectional, as you note.

In a typical closed speaker, the wave from the inward motion of the speaker cone is heavily attenuated.

In an OB / dipole, the inward-moving wave is let into the room along with the outward-moving one.

Of course, waves that are 180 degrees out of phase with each other cancel out when they meet.

This is more of a problem for low frequencies than high, since as you note, the wave wraps around whatever is smaller than it. For very low frequencies this means you are cancelling out a lot of bass before it even travels away from the speaker.

This is why @DVDdoug said they are inefficient, because a lot of the amp and speaker's output is used up by this cancellation, where they would not be in a box speaker.
 
Y'all can say I misunderstand all you want, even though I do understand the theory. Am speaking from actual experience. Have two sets of speakers with open baffle woofers and in my rooms they make plenty of bass at the listening position. Qualifier though, they are far from the back wall by most people's standards and power supplied to them is not a limitation.
 
Y'all can say I misunderstand all you want, even though I do understand the theory. Am speaking from actual experience. Have two sets of speakers with open baffle woofers and in my rooms they make plenty of bass at the listening position. Qualifier though, they are far from the back wall by most people's standards and power supplied to them is not a limitation.
Having owned mostly panel speakers I have experience too. No one said OB woofers couldn't make bass. Doesn't change the fact they are dipoles and not monopoles and that does have consequences.
 
To answer one of the OP's questions, "Are there any in-room real-life measurements available?"

Yes, here are in room measurements at the listening position for Lii Song F-15s and Fast 8s in Caintuck baffles paired with W-15s in Caintuck baffles. A miniDSP 2x4HD is being used to low pass the signal to the W-15s. One mistake made in the Fast 8 and W-15 sweep is failed to lower the W-15 input signal by ~5dB to account for the Fast 8s being most sensitive than the F-15s. IIRC, REW uses a 1k Hz signal to check levels and that is why the F-15s and Fast 8s are the same SPL at that frequency.

1736819696658.png
 
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OB Subwoofer in the corners make no sense at all. The optimal place for OB Subwoofer is near listener, well out of wall.

Yes you can simulate OB speaker with your room size as box parameter.

OB have dipole characteristic in low frequencies, so it can not pressure the room below the first room mode. So depend on your room, the OB Subwoofer only work down to certain frequency. For my living room, it is around 28 Hz. So I use sealed subwoofers with 40 Hz low pass filter to assist my dipole speaker.
Like this?

IMG_0479.jpeg
 
The picture above shows a dipole subwoofer system I used to have. It was four towers surrounding the listening position at very short distance, less than 2 meters. It had sixteen Beyma 21SW1600nd drivers. Despite the massive cone area and 30mm Xmax it failed to produce really low bass at high SPL.
 

Anyone remember these
 
The picture above shows a dipole subwoofer system I used to have. It was four towers surrounding the listening position at very short distance, less than 2 meters. It had sixteen Beyma 21SW1600nd drivers. Despite the massive cone area and 30mm Xmax it failed to produce really low bass at high SPL.
When you say "really low" and high spl you must mean 12hz @120dB right? o_O
 
There are several problems with dipoles and efficiency.

One being that the required cone excursion for a given SPL increases by a factor of eight per octave below the dipole peak. If you need 1 mm to reach 90 dB at 100 Hz, 50 Hz = 8 mm and 25 Hz = 64 mm.

An other is that dipoles don’t pressurise the room, and therefore have no room gain. The response usually drops like a cliff below the lowest room mode.
 
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