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12" Peerless XLS dual passive radiator sub project

This page shows off a subwoofer project of Adrian Mack using the excellent drivers manufactured by peerless

Click here to go to Adrian Mack's Audio DIY homepage with my other subwoofer projects and audio related items

    830500 back view

  • Aims
  • Planning
  • Materials
  • Construction
  • Pictures
  • Final Product
  • Acknowledgments

I. Aims

I've always been an audio fanatic and hard-core DIYer all my life, and it was time to build yet again a new subwoofer for my stereo system. But what is a subwoofer??? Well to define that a subwoofer is basically a loudspeaker design to reach into and below the bottom octave of frequency's. Really, a subwoofer should be able to reach down to 20Hz to be any good. For SPL, I wanted something around 105db @ 20Hz. I wasn't quite sure on the budget yet, but it was around AU$1300 in the end.

II. Planning

Okay. Time to choose a wooofer. Today, there are SO many available that the choice can get hard. (taking a look at how much you have in your wallet may help though!) The design I choose was a former of the vented. The passive radiator. This was chosen as no port noise is emitted, and the the most part, ease of use. It is much easier to just throw in a PR instead of dealing with 4m long ports! Also, the ported designs are +3db more (sealed is only half-power). This proves a good choice for SPL. This sub was intended for both home theatre and music use (which is why the low F3 is chosen).

I was looking at these subs in detail: Adire Audio Shiva, Peerless XLS 830500, TC Sounds HE12, lambda acoustics drivers and a few blueprint drivers. At the end of the day, I decided to go with the Peerless XLS 12" 830500 driver because of its very good value for money in Australia (to import a us sub to Australia ends up costing a LOT of $$$). At first thought it was going to be very difficult to have a vented design, as it was calling for huge 4 or so meter long ports. The idea of passive radiators did come to mind, but they were going to cost me AU$150 each, and I was going to use two. So thats AU$300 worth of stuff which is the same as a $10 PVC pipe - damn. In the end though I knew it was the only way to go. The great thing about these peerless xls drivers is their very small vas and low fs. This means that it can be used in a really small enclosure. The size for this project was just a small 50 litres! So here are some of the benefits of using a passive radiator in place of a port:

  1. Low tuning in small cabinets possible as their is no long ports to deal with
  2. The active driver is more protected from large excursion at low frequency's because of the suspension progresitivity of the PR
  3. Being properly tuned can result in very high performance
  4. Low distortion
  5. No port noise
However some of the drawbacks include high cost, bad transient response if not tuned properly and excursion may be all used at low frequency's. The XLS drivers also have very good driver construction. Take a look at the diagram below:

xls cutaway view

A. Aluminium Spacer The aluminium spacer serves as heat sink for the coil to reduce power compression.

B. Black Anodized Voice Coil The 2-inch 4-layer voice coil is wound on thick black anodized aluminium for improved heat dissipation.

C. Stacked Magnet System The twin stacked magnetic system is optimized by FEA (Finite Element Analysis), to create a symmetric powerful magnetic field in the air gap, and provide space for the 44 mm max excursion of the voice coil.

D. Distortion Reduced Motor A long 4 layer voice coil normally results in high self induction and impedance varying with excursion. Its many ampere turns react on the magnetic field in the air gap. These two main factors causing motor distortion in subwoofers are practically eliminated by the combined impact of the Aluminium Short Circuiting Ring (D) and the Aluminium Spacer (A) on the pole piece. At the same time they both contribute as heat sinks for the voice coil, reducing power compression. The result is unbelievable clean bass reproduction.

E. Vented Cone To eliminate compression under the dust cap the cone is vented by 8 large holes. This way the coil is cooled and there is no need for a bore in the pole piece.

F. Nomex® Spider The spider is made of high tech Nomex® material. This material is chosen for its high rigidity and long term stability. The suspension will stay in shape for a very long time under heavy load.

G. Rubber Surround The surround is made from SBR rubber because of the wide operating temperature, low creep and long term reliability.

H. Fibre Composite Cone The cone is moulded from a propriety air dried wood free pulp with a blend of Nomex®, Kevlar® and glass fibres bonded together by deep impregnation with polymers. This creates an ultra stiff and relatively light cone that will stay stable even under very large sound pressures.

I. Rigid Cast Aluminium Basket The rigid cast basket with an aerodynamic profile provides the necessary sturdy base for the magnet structure and suspension and allows for the 44 mm max excursion of the cone. The spider is ventilated to achieve the lowest possible compression and allow air to flow freely to create a cooling effect for the voice coil.

This was to be an active subwoofer (as passive subwoofers draw to much power from the main amp) so I needed another amp for it. I ended up getting the AA0508 350wrms 4/8ohm plate amplifier. This deemed appropriate for the design, which will provide the sub 109db SPL @ 30Hz in anechoic chamber. Below are the Thiele/Small specs for this woofer. Notice the large Xmax, low fs and low vas of the driver:

Thiele/small parameters



Free air



Nominal impedance






Minimum impedance/at freq






Maximum impedance






DC resistance






Voice coil inductance






Capacitor in series with 8 ohm(for impedance compensation)






Resonance frequency






Mechanical Q factor






Electrical Q factor






Total Q factor






Xmax (linear one-way)





F (Ratio fs/Qts)





Mechanical resistance






Moving mass






Suspension compliance






Effective cone diameter






Effective piston area






Equivalent volume






Force factor






Reference voltage sensitivity Re 2.83V 1m at 106Hz (Measured)





Magnet and voice coil parameters


Voice coil diameter





Voice coil length





Voice coil layers





Flux density in gap





Total useful flux





Height of the gap





Diameter of magnet





Height of magnet




Weight of magnet





Now lets get onto the thiele/small specifications for the 830548 passive radiator:


Thiele/small parameters




Resonance Frequency




Mechanical Q factor




Equivalent volume




Mechanical Resistance




Moving mass




Suspension compliance




Effective piston area




Xmax Peak (one-way)




The calculated design for this subwoofer ended up showing good SPL and very low bass in the following setup. The peerless XLS 12" 830500 driver to be used in a 50 liter enclosure, with two peerless 830548 12" passive radiators massed to 790grammes each, and a 350wrms AA0508 amplifier with active eq (20-35Hz depending on room size). This would produce a flat response to 20Hz (ie: F3). The system was expected to produce SPL levels of 110db or so at around 20-30Hz. I loved this design, especially because of the small box size! Usually a good 12" would require boxes of 100 liters or over! With all these components to be mounted in the box, it would be very hard to fit bracing in (bracing makes the box sturdier and reduces box resonances). Every wall (except the top and bottom) was to have something mounted on it (4 things total - 2 pr's, 1 driver and 1 amp). So instead of your standard 1" MDF box, I made it 1.75" (or 43mm converted). This meant using two layers of wood - the first layer was 3/4", and the second was 1". These were on top of each other and with this combination, was actually making a rebate for the driver itself (flush-mounted). Now a grill could be put on with no trouble of having the surround and cone hit up against the cloth. A cut list is provided in the next few sections for anyone wanting to build off this idea. Also, once the enclosure is finished, a layer of acoustic foam/lining is used on the top and bottom of the enclosure to help decrease box resonances.

The Driver - Peerless 830500

The Peerless XLS family consists of a range of drivers especially developed for the high performance subwoofer application. The goal with the design has been to produce drivers with an unexcelled long excursion performance with low distortion. Using Strontium Ferrite Magnets and Finite Element Analysis to optimise the iron circuit, high levels of BL have been obtained. With the high BL available, Peerless has been able to design drivers with a high moving mass and low fs but without high Qt and low sensitivity. Mechanically the subwoofers offer a strong base, which will provide many years of high performance bass reproduction. The aerodynamic cast aluminium frame supports the vented Nomex spider and rubber surround for a heavy-duty suspension that will not fatigue. The rigid fibre reinforced and deep impregnated cone will produce low distortion bass without coloration.

Peerless 830548 passive radiator

The passive radiator version of the 12" XLS family of drivers. The passive radiator is available in three different standard moving masses. To enable the designer to fine-tune the moving mass an M5 threaded hole has been added on the mass block. This way extra mass can be added in an easy and simple way. The moving components and the frame are the same as the 12" active driver providing the solid base for a high performance passive radiator.

III. Materials

The total for the project cost me a little over AU$1000.
The materials used for this project is in the table below:


830500 12"XLS driver

830548 12"XLS passive (X2)

350wrms AA0508 amp module


2400mm x 1200mm sheet 1" MDF

1200mm x 600mm sheet ¾" MDF

Wood screws (X3)

Self tapping screws

Liquid nails (X2)

Liquid nails dispenser

Jarrah gloss stain

Clear gloss stain

Can "satin black" paint

IV. Construction

Well first of all, you guessed it, you have gotta cut the wood. So I marked up all the dimensions on my MDF board and then cut them with a circular saw. Be sure to sand off any rough edges when finished. Next, its time to cut the holes for the driver, amp, remote receiver and passive radiators (a jigsaw or a router will do this). You can find a complete cut list down the bottom of this page. Now we can start assembling it. Its as easy as 1, 2, 3. Just simply put the enclosure together one by one, using liquid nails and then wood screws for a tight solid join. This also seals the joints.  The image to the right shows how to join the pieces together/what order they should be in. You first assemble the inside box, then join the outside pieces on. Leave the top till last for easiness. To attach the inside box to the outside box layers, use lots of liquid nails and screws. Again, sanding down any rough edges along the way. Once you have the whole thing together, use a belt sander to sand down the actual surfaces of the enclosure. Well thats basically about it. Make sure you use screws long enough to go through the 43mm MDF. I used 75mm screws - I would recommend you use them too if you wish to make my subwoofer. The finishing is up to you. I painted mine with a jarrah gloss stain, with black strips on all edges, then applied a clear gloss over the top. You can do whatever you like though - its whatever aesthetics suit you. You could put wood veneer over it, or tile it. Your option.

Also visit THIS PAGE for more images of the enclosure.

Box dimensions

Inner front: 450*386*18
Inner sides: 450*350*18
Outer front: 450*436*25
Back: 450*386*25
Outer Sides: 450*393*25
Bottom: 350*350*35
Top: 500*475*34

All dimensions in mm (millimetre)
The above is in the format of: HxWxT. Basically, take the inner front for example: 450*386*18. This means you must use 18mm thick MDF (3/4"), and cut it to dimensions 450mm X 386mm



V. Pictures


VI. Final Product

The final results were very outstanding indeed. It reaches well to 20Hz, and hits very good SPL levels, considering the enclosure size. This is the most bass I've ever made out of a 50 litre box. Here are the SPL (sound pressure level) results:

SPL 104db @ 20Hz
SPL 109db @ 30Hz
SPL 112db @ 50Hz

All these SPL levels were measured anechoic - this is so room gain will not get in the way of the results.
Indoors, its flat to 20Hz and plays at about 112db throughout its passband.
If you wanted to cut costs a bit, you could use just one passive radiator instead of two. But make sure you don't add any extra mass to this - it must be massed to 435 grams.
Please excuse the image quality my digital camera is a real piece of crap. The sub looks WAY better than this in real life.

VII. Acknowledgments

I must thank peerless for their excellent subwoofer drivers used in my project. I would also like to thank William Cowan from his own company, Cowan Audio for all his help in this design, and also being the person who I bought the equipment used for my project at a great price.

Check out the Peerless XLS 10" version of this project, its the same idea as the 12" sub on this page, except its 10", has one XLS 10" Passive Radiator and is only 20 litres in volume !!!

Please EMAIL me at macky888@wasp.net.au if you have any comments, suggestions, questions, etc. I would love to hear from you!

This project was copied with permission from http://www.geocities.com/adrian_mack/homepage.html


Peerless XLS 10" Dual Passive Radiator Sub

Here is a nice little sub, and is it small indeed, at 30 liters! It uses a Peerless XLS 10" driver (part code 830452) and two passive radiators, also made by peerless (part code 830468). This sub was designed to extend to ~22Hz in a very small enclosure. I personally did not make this sub, it was built by Mark Beaulieu, I did the design work for him (Mark can be contacted at markb1@cableone.net). Don't let the small box size fool you, this is a very capable sub. It is a 6th order design, as it uses active equalization to achieve a flat response taking into account the room gain. The bass is very clear, and for such a small enclosure, output is still over 110db. Output to 22Hz can even be made in as small as a 20L box if required. The sub is powered by a 250Wrms plate amplifier with remote from Parts Express.

The driver used is one from a favourite brand of mine, Peerless :) Features include extended pole piece, faraday ring in voice coil assembly for lower distortion, rubber surround, cast chassis, small box operation, and all the other well known features of the XLS series. See the 12" Peerless sub project for more info on driver choice.

Here are some pictures of the box being built, and the final pictures. They are rather large pics, and may take a while to load depending on what connection you have.


Adrian Mack's Homepage


Excel Subwoofer Designer

Here is a Microsoft Excel spreadsheet that I have made which models the response of vented box systems and sealed box systems. It is based on Brian Steele's spreadsheet (diysubwoofers.org), but I have modified it to provide more functions to aid in designing a subwoofer. Some of the functions of this modified spreadsheet are:

  1. Alignment Comparisons - calculate box size/tuning for Thiele and Small vented/sealed box alignments such as SBB4/BB4, SC4/C4, QB3/SQB3, etc and different sealed box Qtc's

  2. Compare vented box and sealed box response simulations on the same graph

  3. Simulate almost all types standard active crossovers, user specified Q and center frequency for Linkwitz Riley, Butterworth, etc

  4. Set Qa/Ql/Qp losses

  5. Parametric and sallen key EQ modelling

  6. Simulate effects of adding extra mass to the cone and shows new T/S parameters of driver when mass added

  7. Simulate extra circuit resistance in cabling/xover/amplifier

  8. Calculate frequency of 1st port resonance

  9. Calculate usable xmax of driver based on voice coil length and gap height, with more complex calculation for cone overdrive

  10. Compare real world to measured results, user enters measured frequency response data

  11. Model the response contribution of car cabin gain and room gain

  12. Model transfer function of vented and sealed systems including effect of active filters/EQ

  13. Model phase and group delay of sealed and vented systems, including effects of active filters/EQ

  14. Model electrical impedance of sealed and vented systems with circuit resistance effects and voice coil inductance

  15. Model port air speed including effects of active filters/EQ

  16. Model cone excursion of vented and sealed systems including effect of active filters/EQ

  17. Model excursion limited SPL at given power level of vented and sealed systems including effect of active filters/EQ

  18. Model port contribution to system SPL including effect of active filters/EQ and SPL caused by leaks

  19. Model phase and group delay response separately of active filters/EQ

  20. Model transfer function response of active filters/EQ

  21. Calculate components required for 2cd sallen key active EQ and schematic provided

  22. Help notes throughout entire spreadsheet - move mouse pointer over the red tag to see help note, more on this in Introductory tab in spreadsheet

It's an easy to use spreadsheet too. As stated above, there's also help notes right throughout the spreadsheet in case something doesn't make sense. Please contact me if you have a problem with it though.

Click the link below to download Excel Subwoofer Designer

Download page

Download excelsub.zip (6.5Mb!)

Alternate Link excelsub.zip

You will need Winzip to extract the Microsoft Excel spreadsheet. You can download a free copy of winzip from http://www.winzip.com/

I would like to hear any comments, suggestions, etc about this spreadsheet.
Please email them too macky888@wasp.net.au Back to homepage



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