Unrestrained Mystery OB Subwoofer Finale

[aeroash]

Open Baffle Subwoofer built by Javad Shadzi - (just sharing here)

Some quotes from Javad on these.

Unrestrained Mystery OB Subwoofer Finale
I designed and built an open baffle speaker system last year called the Unrestrained Mystery, you can read about it here: https://m.facebook.com/groups/DIYLoudspeakerProjecPad/permalink/1400546016967898/
In a small room they have great bass down to 40hz, in a bigger more open room they need some help below about 50-60hz so I decided to design a dual 15” open baffle H-Frame subwoofer using a pair of the newish SB Audience open baffle 15” drivers, the Bianco-15OB350.

This is an easy subwoofer to build with good in room response down to 20hz and below, this wont knock paintings off your walls but for any music they will play full spectrum bass to a solid 110dB 1-meter and sound great with movies too. A pair of these would add 6dB and be a very nice setup.

The dimensions of the H-frame are 36” tall internally, 16” deep and 18” wide internally. I used 1.5” thick material so outside dims are 37.5” tall not including the feet, and 19.5” wide. A top cap simply needs to cover the top and will be determined by your final material dimensions.

I am running the pair of woofers stereo off an Adcom GFA-555 with a MiniDSP 4x2 HD before that and the amp for the UM towers.
This is a very easy build, it could be done with 3/4” plywood easily but I’d recommend doubling you the baffle at least. I made this from 1.5” birch counter top material from Home Depot and it’s held together with pocket screws so it’s easy to disassemble if I want to move it.
I only used one EQ filter at 30hz, these don’t have a ton of excursion so you can’t get carried away with EQ, and 24db/octave crossover at 80hz which hands off to the towers also crossed at 80hz.

OB bass doesn’t interact or pressurize the room like a boxed speaker does, they are generally more forgiving of room modes, these sound great in room and really disappear, I’d like to add a second, that would be perfect for movies.

in general I really like the sound of open baffle bass, it actually doesn’t sound any different, it’s just not very efficient, but what bass frequencies are produced sound clean and uncolored.
As you can see the response of this subwoofer goes well below 20hz and it can produce 110db of bass at 1 meter and loud sounding bass in room. Two 15” ported subwoofers would use a lot less power to get there and get even louder, at least 6db.

Does 20hz OB subs sounds substantially different from boxed subs? not substantially, this subwoofer sounds clean and accurate, just like any properly designed subwoofer should. OB bass is also more immune to room modes so the bass sounds more even anywhere in the room.

 

[aeroash]

I would do one each for each channel. With drums it’s great fun. Though I could not do a second H frame as my room width was small.

Absolutely! these should sound great for music in a dual setup. It could also be an easy project for anyone to take up.

Not sure if you built them or these are exact Javads build you have shared…

Javad Shadzi built these, and I have edited my post to remove any misunderstanding.

 

[srinisundar]

Can this be used a subwoofer for a boxed too ? Or it is specifically designed for OB ?

 

[Yelamanchili manohar]

Open Baffle Subwoofer built by Javad Shadzi - (just sharing here)

Some quotes from Javad on these.
















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Part 1 done

I already have 4 of these bianco drivers sitting in my cup board. Now just need to get out of my laziness and get some work done

 

[aeroash]

Part 1 done

I already have 4 of these bianco drivers sitting in my cup board. Now just need to get out of my laziness and get some work done

Going for open baffle?

Here is mine, quite simple for a starting attempt I did many years ago: F6 on full range duty.

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Still using them? How do the subs sound?

 

[Yelamanchili manohar]

Going for open baffle?

Unfortunately will be too big for my small room. So planning a dipole sub build.

 

[Decadent_Spectre]

OB is easy to do and fool proof, but it lacks output. I've said this before it's lack of output is why I don't try OB. I'm not sure I agree that it doesn't sound different than a boxed speaker, what I've read says otherwise. OB is often said to be very smooth and a little bit of a linger, not as fast as a box.

 

[srinisundar]

Never built a subwoofer on my own...Can this driver be used a subwoofer in this ported box specifically made for Altec 614 woofer ? How much will this will go down.. I have two boxes.. Just want to add these if it works below 50 to 30hz to my Altec A5 setup.

Just having doubt it is mentioned for OB ....

Any inputs ?

Thanks

 

[grindstone]

Had a look and, "no", not a good candidate for those. Big peak at 100, no real bass--definitely nothing to low-assist an A5. Box is too small to even really get anything by throttling (acoustic resisance) port or lengthening it.

 

[Hari Iyer]

Absolutely! these should sound great for music in a dual setup. It could also be an easy project for anyone to take up.


Javad Shadzi built these, and I have edited my post to remove any misunderstanding.

Why not push-pull if using dual woofers.

 

[Hari Iyer]

My H-frame sub have a reconed Bolton 10" low compliance woofer and they do 36Hz at -6dB. Good enough for my 180sqft room. I have noticed that electrical crossover is not much effective in rolloff, but acoustic crossover dictated by the height of the box dictates the crossover frequency- atleast in my case. YMMV. Also, I have tried usingca Dayton Audio 10" subwoofer having medium compliance. The bass sound bloated and boomy with the Dayton Audio driver. Bolton matches 100% to my frame. Only listening is believing.

 

[aeroash]

My H-frame sub

Pictures, please.

 

[Hari Iyer]

Pictures, please.

 

[aeroash]

First and second from the top are wideband? Looks like you changed the driver in the middle slot. What drivers are these?

 

[Hari Iyer]

First and second from the top are wideband? Looks like you changed the driver in the middle slot. What drivers are these?

First driver from top - JBL compression driver mounted on an 8" Dayton Audio waveguide. This was installed 2 months ago - model 2022.

Second driver - same - Sachenwerk 8" field coil driver - pre world war 2 Era-1938 - installed 2 years ago. This driver is installed from behind for time alignment with the 12" woofer as there are common frequency radiated by these two drivers. This is a two way speaker system.

Third driver - Cleveland Audio - 12" Alnico woofer - salvaged from church organ - 1962. This driver replaced the Ahuja 12" woofer 1 year ago

 

[aeroash]

@Hari Iyer What's the reason behind going for an H frame for the sub, while in the main baffle the woofer is in a U frame? Curious.

 

[Hari Iyer]

@Hari Iyer What's the reason behind going for an H frame for the sub, while in the main baffle the woofer is in a U frame? Curious.

The 12" woofer on the main baffle is driven by a 3+ 3 watts class A tube amplifier which is difficult to get driven unless it's very high seensitivity driver. Resonance is 70 Hz and roll-off below that quite rapidly. H-frame was used for bottom end support below 80 Hz.