Based on low frequencyresponse models for the Peerless 83084 XXLS woofer, the desired cabinet volumefor the woofer alone is 2.2 cubic feet tuned to 27Hz. To obtain this target volume, we have to alsoaccount for the volume needed for the RS150-8 midrange, volume of the port andthe space occupied by the physical drivers in the system. Cabinet designs can be done by hand orpreferably using 3D computer aided design (CAD) software such as SolidWorks orSketchUp. It is much easier to see whatyou are working with and make changes in CAD instead of having to recutcabinets. Books could be written oncabinet design, but here are some basic things to think about beforestarting.
- Rounding over thecabinet edge reduces peaks and troughs in frequency response around the bafflestep diffraction frequency.
- Cabinet materialand material thickness play a huge role in reducing the sound a cabinetmakes. Medium density fiberboard is thestandard material because it is relatively inert, readily accessible and is prettyeasy to work with. Baltic birch andplywood are also popular choices. Inmost cases, 3/4” or greater wood thickness is recommended.
- Use plenty ofinternal cabinet bracing to reduce panel vibrations and space the bracingasymmetrically to reduce the effects of standing waves.
- Countersink alldrivers, the diffraction effects of a surface mounted driver might surprise you.
- Chamfer the backof all open back driver cutouts to allow for better airflow behind thedriver. This is typically required forall drivers except the tweeter.
- For 3-way systems,placing the midrange in a separate internal enclosure produces cleaner midrangeperformance. It is a good idea to slantthe back of the midrange chamber to prevent reradiating sound from the back ofthe chamber through the midrange cone.
- Build enclosures aminimum of 10% larger than design requires as it is easy to fill dead space buthard to create volume once it is built
- Determine properport tuning by starting with a longer than calculated port tube length andreduce the port tube length to meet the target port tuning by measuring eitherimpedance or acoustic output of the port.
- Use flared portthat is flared on both ends and has adequate diameter for the proposed ventedenclosure and expected sound pressure levels.
- Expect to invest aminimum of 3-5 full days of work for a high quality tower loudspeaker cabinet.
How to Design A Subwoofer Box Using WinISD Pro - Duration: 12:33. Austin Johnson 13,869 views. Harristech BassBox 6 Pro Software Demo - Part 2 - Duration: 6:55.
Determiningthe port parameters for a cabinet is not complicated but it is best to use acalculator on the manufacturer’s website. Flared ports are not all the same and reaching the target tuningfrequency is easy to determine by plugging in the necessary parameters into themanufacturer’s website. Just note thatit is best to leave the port tubes a little long and trim to reach the targettuning frequency. Tuning an internalvolume of 2.2 cubic feet to 27Hz requires a port tube that is approximately 9.7inches long for a 3-inch diameter port. This port occupies approximately 0.04 cubic feet so the internal cabinetshould account for the port volume. Also, it is important to determine the volume of internal bracing andestimate the volume of the drivers protruding into the cabinet. When all issaid and done, add an additional 10% to the calculated required internalcabinet volume. Once the internal volumeis determined, it is pretty simple to determine the required cabinetdimensions. Standing waves are greatlyreduced when cabinet internal dimensions are not the same or multiples of thesame distance apart. If you are brave, non-parallel walls should yield evenbetter results. For this project, themidrange is placed in a separate sealed space that is not included in thewoofer cabinet volume calculation. Themidrange chamber benefits from non-parallel walls as well. It is a good idea to run simulations on themidrange driver in the intended enclosure to confirm the enclosure size willnot negatively effect frequency response.
This project was designed inSolidWorks but could easily be done in Google SketchUp. The 3D CAD programs allow for easycalculation of internal volume and are really handy for test fitting driversand ports before building the cabinet. Ionce designed a simple sub cabinet but didn’t realize the port length wouldinterfere with the driver until the cabinet was finished. I ended up rerouting the port using a seriesof bends that ended up causing port noise when the volume was cranked.
- Because driver selection is such a crucial part of speaker design, WinSpeakerz includes a very sophisticated loudspeaker Driver Database. From the database page you can search for drivers that meet your requirements for a project.
- BassBox 6 Pro – A powerful speaker box design program with many professional features, including a design wizard and a huge driver database with the specs for thousands of drivers. Also includes a beautiful 364-page printed manual and an extensive on-screen manual with tutorials and sample designs.
- Design Your Enclosure. We strive to make the design process simple for you, whether you are an expert in enclosure design, or an electronics professional who is experiencing custom enclosures for the first time. Click on the tabs below to learn more.
- Eminence Designer is a state-of-the-art speaker enclosure design program for PCs running Windows 95, 98, NT4 or later. With Eminence Designer, box design is as easy at 1-2-3: 1. Enter the speaker parameters (for Eminence speakers, simply select the model; other speaker parameters can be entered manually). Calculate the box volume and tuning.
In this project, we used 3/4” Balticbirch with a 3/4” MDF baffle and bottom plate. This was selected because the loudspeaker sides were subsequentlycovered with album covers and Lexan for a unique finish. The panels were cut using a table saw and allchamfering and circular cutouts were completed using a quality plungerouter. A circle-cutting jig is aworthwhile investment as it provides accurate results in short order. The bottomof this speaker is removable with weather stripping between the detachablebottom and the rest of the cabinet. Abottom firing port is attached to the bottom plate, which requires 2-3 inch longfeet or spikes for clearance. Althoughit is probably obvious, it is highly recommended to test fit everything beforefinal assembly. When test fitting drivers, it is a good idea to drill holes anduse hurricane nuts to allow secure mounting and remounting of drivers. It is also recommended to use biscuit jointswhen gluing panel walls together although it is acceptable to use screws tohold panel walls together for gluing. Once the glue is cured, all screws should be removed. For this project, the baffle, bottom and backof the speaker were spray painted. Spraypainting MDF is time consuming because it requires several iterations ofsanding and painting to obtain a smooth finish since MDF absorbs some paint,especially on corners that are rounded over. Finally, album covers were glued to the cabinet and the covers wereprotected with a thin layer of Lexan.
Test Fitting Drivers
Hereis a list of materials and tools needed to pull off a typical cabinet build.
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- 3/4”Medium Density Fiberboard
- HurricaneNuts and Bolts for Driver Mounting
- FlaredPort Tube
- BindingPosts or Terminal Cup
- CarpetSpikes or Feet
- ElectricSander and Sandpaper
- BiscuitCutting Tool and Biscuits
- TableSaw with Solid Gate and Sharp Blade
- Seriesof Chamfer Bits for Router
- Seriesof Round Over Bits for Router
- 1/4”Straight Cutting Bit for Router
- CircleCutting Jig for Router
There are a largenumber of possible finishes for a DIY loudspeaker project. I have had success with paint and real woodveneer but both require a little practice and much patience. Once you havedecided on a finish, do some research to determine a good application method. I’ve never gotten a finish right the firsttime, so practicing on scrap material is highly advisable.