Full Range Drivers For Open Baffle Design

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Full Range Drivers For Open Baffle Design

Baffle Range Hood
Open Baffle Speaker Design
Full Range Open Baffle Speakers
Outdoor Range Baffles
Best Full Range Driver For Open Baffle
Started a DIY build this week for the future son inlaw. Open Baffle design. Audio Nirvana 10' cast drivers ( purchased from an SNA member ) Have wanted to build some open baffel speakers for a while now but the final inspiration came from a recommendation to build an off centre driver placement design. Free support for loudspeaker projects, sourcing OEM speaker building supplies, and passive crossover design. We sell raw speaker drivers (tweeters, woofers, subwoofer, midrange drivers, full range drivers), speaker kits, amplifiers, capacitors, resistors, and inductors.
Eminence Alpha 15A Experimental Open Baffle DesignIntroduction :Baffle Range Hood Ever since I wrote my article 'Designing a Passive Two Way Open Baffle Speaker System' the idea of combining an Eminence Alpha 15A woofer with a smaller full range driver has been something I have wanted to try. Since I am already using an active crossover system with two SS amps, the choice for the full range driver opens up to just about any available 3' or 4' model. In reality the choice of full range driver could also include many 6' and even 8' models. The lure of an inexpensive two way OB design with enough flexibility to not lock me into a single driver combination convinced me to finally build this experimental OB system late last summer. 
Open Baffle Speaker DesignBaffle Construction Details : Over the years, I have accumulated a nice stash of veneered plywood in various sizes and thicknesses. Digging through my collection, I found enough scrap pieces to build this 20' wide by 38' tall OB speaker system. Recognizing that I wanted to try a variety of full range drivers, each requiring a different diameter cut-out and pattern of mounting screws, I devised an easily removable baffle arrangement. In the picture above you can see an 8' x 8' removable black baffle; a close up view is shown below. When building the speaker I cut enough of these removable baffles to try five different pairs of full range drivers, good enough to get me started experimenting. 

Full Range Drivers For Open Baffle Design

The back of the OB design is shown in the picture below. You can see the bracing arrangement used to reinforce the baffle, attach the removable full range driver's baffle, attach the feet, and provide a method for mounting the terminals for the two pairs of speaker cables required for a bi-amped configuration. The plywood used was the metric equivalent of 3/4', by adding bracing the total thickness approached 1.5'. A strip approximately 1.5' wide and 1/8' think was glued around the perimeter to prevent the plywood laminations from showing along the edges of the finished OB. A close up showing the back of the full range driver's removable baffle is included below. The removable baffle is held in place with four long toggle bolts, Toggle bolts are typically used for attaching objects to dry wall where some added strength is required. For this application, four toggle bolts allow rapid assembly and removal of the baffle. Each full range driver is pre mounted in a painted 8' x 8' removable baffle with a short piece of speaker wire that can be quickly attached to the barrier strip mounted just below the opening. The removable baffles are the metric equivalent of 1/2' thick. A rubber gasket is used to make up the required thickness so the removable full range driver is flush with the main baffle. The woofer is mounted near the bottom of the OB. The Eminence Alpha 15A woofer shares a hole size and mounting screw pattern with a number of other Eminence 15 woofers so this driver can also become a variable for study, for example at some point I would also like to try the Eminence Beta 15A woofer. A final experiment might be to try a low Qts woofer and see what adding low frequency equalization using the active crossover will yield in the way of bass performance.

 Brackets to support the OB are attached on either side of the woofer to each of the vertical bracing strips. Two rubber feet are used for each side providing a good stable contact with my carpeted listening room floor. A horizontal stand-off is attached to the brace at the very bottom of the OB for the bi-wire terminal cup. Two speaker wires are run in parallel to the Alpha 15A woofer and the full range driver's barrier strip from the internal tabs of the two sets of binding posts on the terminal cup. Bi amping using my dBx Driverack PA crossover means that two sets of speaker cables, one set from each amp, are attached to the appropriate pair of binding posts on the terminal cup. 
 The two pictures below show the full range driver's baffle removed from the main baffle and resting on the floor leaning against the main baffle. In the open cut out you can see the black gasket used to mount the thinner full range driver baffle flush with the main baffle. The second picture is a close up of the gasket; the gasket is made from rubber weather stripping purchased at the local hardware store. Those are the construction details of my simple two way active OB speaker system. There is nothing special about the construction details other than the final dimensions and driver placement. Building your own system using these drivers but different construction details should yield equivalent acoustic performance.

Active Crossover and Driver Options : Using an active crossover and bi amping the two way OB speaker system opened up a wide range of 3' and 4' full range drivers that can be easily mated with the Alpha 15A woofer. Not having to worry about the relative sensitivity and applying boost or cut to the full range driver to balance the SPL frequency response is a very powerful design tool. I always simulate the drivers being used and derived what I feel would be an applicable crossover configuration, then the final optimization is done by ear changing the active crossovers settings on the fly in my listening room. 
 So far I have tried the Fostex FF85K, Fountek FR88EX, Mark Audio Alpair 6, and Fostex FE-108E Sigma with great success. Right now the FE-108E Sigma is my favorite of all the drivers I have tried. Each of these drivers eventually produced a nice sounding SPL response after sufficient tweaking of the crossover settings. Several times I was ready to give up on one of the drivers only to find that a slight change in boost level or crossover frequency dialed in the performance to where I was happy. One thing I have observed in my room is that the boost to the woofer usually ends up being 2 or 3 dB more than I applied in the simulation. I am not sure why this is the case but it seems to be consistent for my set-up in my room. It might be different for another system in another room. 
Conclusions : This simple OB speaker system has opened up a lot of possibilities for using different small full range drivers and in the future probably a few different 15' woofers. I have on many occasions quickly swapped out a pre mounted full range driver to produce a different sound from my system. Free software, free download. Loads of fun, the perfect excuse to expand your collection of reasonably priced full range drivers, easy to build, infinitely adjustable crossover, endless EXPERIMENTATION. 
Download free Adobe Acrobat Reader DC software for your Windows, Mac OS and Android devices to view, print, and comment on PDF documents. Adobe reader 10 for mac free download.
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Full range drivers for open baffle designs

The back of the OB design is shown in the picture below. You can see the bracing arrangement used to reinforce the baffle, attach the removable full range driver's baffle, attach the feet, and provide a method for mounting the terminals for the two pairs of speaker cables required for a bi-amped configuration. The plywood used was the metric equivalent of 3/4', by adding bracing the total thickness approached 1.5'. A strip approximately 1.5' wide and 1/8' think was glued around the perimeter to prevent the plywood laminations from showing along the edges of the finished OB. A close up showing the back of the full range driver's removable baffle is included below. The removable baffle is held in place with four long toggle bolts, Toggle bolts are typically used for attaching objects to dry wall where some added strength is required. For this application, four toggle bolts allow rapid assembly and removal of the baffle. Each full range driver is pre mounted in a painted 8' x 8' removable baffle with a short piece of speaker wire that can be quickly attached to the barrier strip mounted just below the opening. The removable baffles are the metric equivalent of 1/2' thick. A rubber gasket is used to make up the required thickness so the removable full range driver is flush with the main baffle. The woofer is mounted near the bottom of the OB. The Eminence Alpha 15A woofer shares a hole size and mounting screw pattern with a number of other Eminence 15 woofers so this driver can also become a variable for study, for example at some point I would also like to try the Eminence Beta 15A woofer. A final experiment might be to try a low Qts woofer and see what adding low frequency equalization using the active crossover will yield in the way of bass performance.  Brackets to support the OB are attached on either side of the woofer to each of the vertical bracing strips. Two rubber feet are used for each side providing a good stable contact with my carpeted listening room floor. A horizontal stand-off is attached to the brace at the very bottom of the OB for the bi-wire terminal cup. Two speaker wires are run in parallel to the Alpha 15A woofer and the full range driver's barrier strip from the internal tabs of the two sets of binding posts on the terminal cup. Bi amping using my dBx Driverack PA crossover means that two sets of speaker cables, one set from each amp, are attached to the appropriate pair of binding posts on the terminal cup. 
 The two pictures below show the full range driver's baffle removed from the main baffle and resting on the floor leaning against the main baffle. In the open cut out you can see the black gasket used to mount the thinner full range driver baffle flush with the main baffle. The second picture is a close up of the gasket; the gasket is made from rubber weather stripping purchased at the local hardware store. Those are the construction details of my simple two way active OB speaker system. There is nothing special about the construction details other than the final dimensions and driver placement. Building your own system using these drivers but different construction details should yield equivalent acoustic performance. Active Crossover and Driver Options : Using an active crossover and bi amping the two way OB speaker system opened up a wide range of 3' and 4' full range drivers that can be easily mated with the Alpha 15A woofer. Not having to worry about the relative sensitivity and applying boost or cut to the full range driver to balance the SPL frequency response is a very powerful design tool. I always simulate the drivers being used and derived what I feel would be an applicable crossover configuration, then the final optimization is done by ear changing the active crossovers settings on the fly in my listening room. 
 So far I have tried the Fostex FF85K, Fountek FR88EX, Mark Audio Alpair 6, and Fostex FE-108E Sigma with great success. Right now the FE-108E Sigma is my favorite of all the drivers I have tried. Each of these drivers eventually produced a nice sounding SPL response after sufficient tweaking of the crossover settings. Several times I was ready to give up on one of the drivers only to find that a slight change in boost level or crossover frequency dialed in the performance to where I was happy. One thing I have observed in my room is that the boost to the woofer usually ends up being 2 or 3 dB more than I applied in the simulation. I am not sure why this is the case but it seems to be consistent for my set-up in my room. It might be different for another system in another room. 
Conclusions : This simple OB speaker system has opened up a lot of possibilities for using different small full range drivers and in the future probably a few different 15' woofers. I have on many occasions quickly swapped out a pre mounted full range driver to produce a different sound from my system. Free software, free download. Loads of fun, the perfect excuse to expand your collection of reasonably priced full range drivers, easy to build, infinitely adjustable crossover, endless EXPERIMENTATION. 
Download free Adobe Acrobat Reader DC software for your Windows, Mac OS and Android devices to view, print, and comment on PDF documents. Adobe reader 10 for mac free download.
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