[undertowogt1]

Hello AC Members,

I am seriously considering building the "Sandbox" Sub woofer utilizing the GR Research Driver Sub woofer and Direct Servo Subwoofer Amp A370PEQ.

My plan is to make the sealed Sub woofer first (the Sandbox) but later experiment with an open baffle design using the same woofer. The question is which driver to purchase? Will both drivers perform well in a sealed design and OB design?

On the GR Website it says:

SW-12-04 sub woofer is meant for a sealed enclosure
SW-12-08FR is designed for applications operating in free air, on an open baffle, or in an infinite baffle application

I plan to pair the sub woofer with the Direct Servo Subwoofer Amp A370PEQ

Any advise is appreciated.

[PDR]

Why not try a OB sand filled baffle.
Best of both worlds....

[rajacat]

Very creative and aesthetically pleasing solution.

[Danny Richie]

That is a good looking OB cabinet.

undertowogt1,  I think you really answered your owe question about which subs to use.

On the GR Website it says:

SW-12-04 sub woofer is meant for a sealed enclosure
SW-12-08FR is designed for applications operating in free air, on an open baffle, or in an infinite baffle application

The SW-12-08FR woofers are also designed to allow two woofers to be powered by one amp.

[Captainhemo]

Love that cabinet Perry   

undertowogt1,   You'll probably want to use a pair of the SW12 08FR's when you try an OB design,  a single OB woofer won't reach   the same SPL as the sealed driver.

Also, when you  move to OB down the road, you'd have to have the shelving circuit added to the A370PEQ (assuming you want to use the same amp) that adds gain as frequency decreases to maintain a flat response down to 20Hz in the OB configuration.  Brian at Rhytmik can easily do this for you when the time comes.

jay

[mlundy57]

Or you can add the shelving circuit yourself. It is very easy to do:

1) unscrew the two screws securing the existing board
2) disconnect the wiring connector
3) connect the new wiring connector
4) screw the new board back where the old one was

You just have to make sure when you order the boards from Brian you tell him the model & serial numbers of your amps, that want to convert them for OB use and what make/model drivers you are going to use. 

Mike

[bdp24]

Hello AC Members,

I am seriously considering building the "Sandbox" Sub woofer utilizing the GR Research Driver Sub woofer and Direct Servo Subwoofer Amp A370PEQ.

My plan is to make the sealed Sub woofer first (the Sandbox) but later experiment with an open baffle design using the same woofer. The question is which driver to purchase? Will both drivers perform well in a sealed design and OB design?

On the GR Website it says:

SW-12-04 sub woofer is meant for a sealed enclosure
SW-12-08FR is designed for applications operating in free air, on an open baffle, or in an infinite baffle application

I plan to pair the sub woofer with the Direct Servo Subwoofer Amp A370PEQ

Any advise is appreciated.

For a sealed sub, you must use the 12-04 woofer---it is not appropriate for OB use. The 12-08FR is for open baffle only; it cannot be used sealed, unless the enclosure is huge!

[mlundy57]

BIG major caution here.

How do you plan on using this sub?

If you plan on using it for music only than OB is viable. However, if you plan on using it for home theater also then OB by itself is not the way to go. OB subs cannot handle the heavy low frequency effects of action movies like a planet blowing up in Serenity or a star destroyer flying over in Star Wars. These effects will cause the drivers to bottom out.

If you want to use your system for both music and HT and you want all the sonic benefits of OB subs you can do it, you just need to add a sealed (or ported) sub designed for HT use to the system. The OB subs are connected to the left and right main channels (which are set to large/full range) and the HT sub is connected to the LFE channel (subwoofer out).

This is how I have my system set up. I get all the benefits of OB subs for music, including the soundtracks of movies, and can shake the walls and rattle the windows when the special effects kick in without over driving the OB subs.

Mike

[Early B.]

If you want to use your system for both music and HT and you want all the sonic benefits of OB subs you can do it, you just need to add a sealed (or ported) sub designed for HT use to the system. The OB subs are connected to the left and right main channels (which are set to large/full range) and the HT sub is connected to the LFE channel (subwoofer out).

This is how I have my system set up. I get all the benefits of OB subs for music, including the soundtracks of movies, and can shake the walls and rattle the windows when the special effects kick in without over driving the OB subs.

Mike

I've been contemplating using my OB subs for HT along with my HT sealed sub. Do you have an HT bypass option on your HT preamp that you use when listening to music? Just curious to see how you've got it all hooked up. 

[mlundy57]

I've been contemplating using my OB subs for HT along with my HT sealed sub. Do you have an HT bypass option on your HT preamp that you use when listening to music? Just curious to see how you've got it all hooked up. 

I have three sources 1) an external DAC connected to a computer for my digital library; 2) a turntable; and 3) an AVR for movies.

All three sources are connected to a DODD tube buffer (0 gain preamp) with three inputs and two outputs. The DAC is on input 1, the turntable is on input 2 and the AVR is on input 3. Output 1 goes to a Prima Luna Prologue 4 power amp with a pair of inline filters in between to prevent the lows from getting to the Wedgies. The Wedgies are connected to the power amps binding posts. Output 2 from the DODD goes to the A370PEQ plate amps.

The Marantz AVR has a full set of preamp outputs so I connect the left and right preamp outputs to the DODD tube buffer with RCA interconnects.  My sealed sub is connected to the subwoofer output of the AVR. The surround speakers are connected to their respective binding posts on the AVR. I don't use a center channel speaker. The main speakers are set to large / full range and the subwoofer to LFE only.

The reasons for going through the tube buffer are to filter the lows off the Wedgies and to keep the music and movie connections the same as much as possible. Using the DODD I can easily switch between my digital library, turntable and AVR. As for master volume control, with digital files or vinyl I use the DODD's volume control while for movies I use the AVR.

Mike

[Odal3]

PDR - that looks really great. Do you have any pictures with the drivers installed? Also, does it make a difference of not having the center brace between the drivers?

[undertowogt1]

All this info is great, thanks you. Since I can't really utilize one driver for both OB designs and Sealed designs I have had to re think my plans. I guess it is best to go with 2 SW-12-08FR Servo Sub Woofer with the Direct Servo Subwoofer Amp A370PEQ and do it OB design from the start. After all, this is for Music playback only.

[mlundy57]

All this info is great, thanks you. Since I can't really utilize one driver for both OB designs and Sealed designs I have had to re think my plans. I guess it is best to go with 2 SW-12-08FR Servo Sub Woofer with the Direct Servo Subwoofer Amp A370PEQ and do it OB design from the start. After all, this is for Music playback only.

For music only go with OB all the way. You'll have a hard time wiping the grin off your face 

Just beware of the monster you will be creating. Look at Jay (Captainhemo), he started off with one dual 12" driver OB sub and now he has two triple 12" driver OB subs, one for each channel Bwaaahhhaahahahahaha !!!!! 

FIY, if you go with the SW-12-16FR drivers you give up some output over the 08FR's but if you decide you would like the three driver version later on you would only have to buy one more driver. The A370PEQ amp can drive two of the 8 Ohm or 3 of the 16 Ohm drivers.

Mike

[bdp24]

All this info is great, thanks you. Since I can't really utilize one driver for both OB designs and Sealed designs I have had to re think my plans. I guess it is best to go with 2 SW-12-08FR Servo Sub Woofer with the Direct Servo Subwoofer Amp A370PEQ and do it OB design from the start. After all, this is for Music playback only.

Are you thinking of one OB sub (with two drivers), or two? Even for music only, I don't know that one OB sub will give you enough output. What is the size of your room? At what volume do you listen? What are your main speakers? What music do you listen to? Maybe someone who has used a single OB can offer advice?

[undertowogt1]

Are you thinking of one OB sub (with two drivers), or two? Even for music only, I don't know that one OB sub will give you enough output. What is the size of your room? At what volume do you listen? What are your main speakers? What music do you listen to? Maybe someone who has used a single OB can offer advice?

The room is about 11 by 15 or so. I am mainly listen to 70's (Neil Young, Floyd, Alan Parsons) to more modern music (Steven Wilson, Tool, Beck, Sigur Ros). I listen at a moderate volume, not too loud but not too soft.
After looking into this more and more and now that I have decided to buy 2 sub woofers, thing have changed. I would think it would be best to make

2 / SINGLE DRIVER OB subwoofers

                  instead of

1 / DOUBLE DRIVER OB subwoofer.

My speakers are book shelf speaker and this way I can set the cross over higher and still have the stereo imaging

Right? AT the same time ........two 12 inch subs seem like crazy over kill for the space

I am totally new at this.........any thoughts?

Am I wrong

[PDR]

PDR - that looks really great. Do you have any pictures with the drivers installed? Also, does it make a difference of not having the center brace between the drivers?

Those cabinets are the bottoms of the Super Vs I built.
The center brace was added a bit later.
Finished product is shown on my avatar.
If your interested heres the build link with plenty of pics.....
http://www.audiocircle.com/index.php?topic=111180.0

[gab]

The room is about 11 by 15 or so. I am mainly listen to 70's (Neil Young, Floyd, Alan Parsons) to more modern music (Steven Wilson, Tool, Beck, Sigur Ros). I listen at a moderate volume, not too loud but not too soft.
After looking into this more and more and now that I have decided to buy 2 sub woofers, thing have changed. I would think it would be best to make

2 / SINGLE DRIVER OB subwoofers

                  instead of

1 / DOUBLE DRIVER OB subwoofer.

My speakers are book shelf speaker and this way I can set the cross over higher and still have the stereo imaging

Right? AT the same time ........two 12 inch subs seem like crazy over kill for the space

I am totally new at this.........any thoughts?

Am I wrong

You probably need 4 drivers (2 per side). More is better. Here is why. To help explain the differences between a sealed sub versus an open baffle sub, I copied a FAQ from Linkwitz's site for the Phoenix OB woofer: http://www.linkwitzlab.com/faq.htm

Q5 - How much sound output can you get from the open baffle woofer?

A5 - I give a formula in Ref. 2 and in Design Models A1 that relates the sound pressure level from a driver on an open baffle to the SPL from the same driver in an acoustically small closed box, assuming that both have the same cone excursion.

        Fequal = 0.17 v / D

At frequency Fequal the SPL is the same for either driver arrangement. The open baffle driver output decreases at 6 dB/oct below this frequency relative to the closed box. Above this frequency it increases to an on-axis peak that is 6 dB higher than the SPL from the box. The peak occurs when the distance D between front and rear equals 1/2 wavelength, i.e. when the rear wave is phase shifted 180 degrees and in phase with the front wave.
For the PHOENIX woofer D = 19" (0.48 m). With v = 343 m/s

        Fequal = 120 Hz

Thus, for on-axis SPL at 120 Hz, one 12" driver in the open baffle cabinet is equivalent to the same 12" driver in a closed box. At 30 Hz, though, the open baffle SPL has dropped to 1/4, i.e. it would take four 12" drivers to maintain the same SPL as the single 12"  driver in a box, when all of them are driven to the same excursion. (See also FAQ14)
At 30 Hz the two woofer cabinets of the PHOENIX are equivalent to a single 12" in a closed box, assuming that the box speaker is flat to 13 Hz (-3 dB). Above this frequency, of course, the two open baffles generate considerably more SPL than the single 12" driver in a box. At 60 Hz the dipoles would be equivalent to two of those 12" box woofers and at 120 Hz equivalent to four in terms of maximum SPL. You can add 6 dB to this capability by doubling the dipole woofers and stacking them on top of each other for a height of 28", but this might negatively affect the WAF. The primary benefit of the stacked woofer arrangement would be reduced non-linear distortion when listening at the same SPL as before.
    A lot of air is shuffled back and forth between the two sides of the open cabinet. This sets up a strong sound velocity field but our ears only respond to sound pressure and we do not hear it. This is wasteful of cone excursion but the price to pay for natural bass reproduction. You can see why the open baffle woofer will never be a popular commercial item, when a majority of consumers loves excessive bass, and when a dipole woofer will just not get the room going in all its resonant modes for additional boom.

[Early B.]

After looking into this more and more and now that I have decided to buy 2 sub woofers, thing have changed. I would think it would be best to make

2 / SINGLE DRIVER OB subwoofers

                  instead of

1 / DOUBLE DRIVER OB subwoofer.

Build one double OB driver and set it in the middle of your monitors. If you build two single OB drivers, you'll need two amps in order to keep the wire runs as short as possible.  Eventually, you'll build another one. I've been there, bro.

[undertowogt1]

Build one double OB driver and set it in the middle of your monitors. If you build two single OB drivers, you'll need two amps in order to keep the wire runs as short as possible.  Eventually, you'll build another one. I've been there, bro.

Thank for clearing my brain . This is a simple, adaptable solution.
Thank for all the reply, I know I have been all over the map with my thoughts.

[Odal3]

PDR - Very Nice! I was going to ask for some more picture, but you beat me to it!

Build one double OB driver and set it in the middle of your monitors

What's the recommended way to connect only one sub if pre-amp/DAC doesn't have specific sub outputs. The HX300 amp only has mono inputs. Only use left channel? right? sum them up and if so how?