Subwoofer project

A summary on speaker concepts can be found at http://www.danmarx.org/audioinnovation/theories.html

Push-Pull means working with 2 drivers, each driver gets half of the amp power and therefore the cone

excursion also halves. SPL output doubles and part of the distortion of the drivers is canceled out

because one of the drivers is mounted backwards.

- Driver: Dayton DVC310-88

This has been a much tougher choice, as there are so many drivers.

A few HTforum members (thx to Morca and MichelDW) pointed me to some quality drivers,

and I made some winisd simulations.

In all my winisd simulations I came accross a common problem, when I want to extend the frequency range,

I always go over Xmax of the driver.

The reason for this is that I overlooked the fact that when you take a signal of 400W (max output of the amp)

and you then boost 6dB @ 20Hz, the amp needs to deliver 1600W for this boost, and with 1600W, the

cone excursion goes behind Xmax.

In order to make a 6dB boost @20Hz, the output power for the other frequencies must be set to 100W in order

to deliver the quadruple power to deliver the extra 6dB@20Hz

A 3dB gain needs twice the power --> 6dB = 4 times the normal power.

As my listening room is about 45m2 and I wanted to have some headroom in case the 400W of the amp would no

be enough for movie effects, I decided to use dual 12' drivers, the advantage is that with the same amp power,

each speaker only has half of the cone excursion, the cones have a lower Mms weight = higher definition of the sound.

In the mean time, a moderator of http://forum.zelfbouwaudio.nl/ told me that Rms is a better indication for

the ability to have a tighter sound than Mms because it takes in account the total mechanical damping instead of

only the weight of the moving mass, so I will review my driver choice with that parameter in mind also.

I checked 3 Dayton drivers:

- SD315A-88: Was used in a push pull speaker I listened to and sounded good, Winisd simulation was ok,

but it does not have the extra headroom I would like.

- DVC310-88: Very low Fs (19Hz), enough headroom on Xmax (15mm) and max power it can handle

Good Mms and Rms values, indicating it can produce a thight bass.

- UM12-22 : More headroom on Xmax (19mm) but higher Fs, Mms and Rms values, higher price.

http://www.daytonaudio.com/index.php/loudspeaker-components/loudspeaker-drivers-by-series/dvc-series/dvc310-88-12-dvc-series-subwoofer.html

http://www.daytonaudio.com/specs/specsheet.php?prod=295-185

Here are some Winisd screenshots, I simulated the drivers in the recommended box volume for sealed and vented,

and also applied a boost to see how much headroom I have left and how much amp power is needed.

SD315 can only handle 120/235W, and goes over Xmax when I boost,

while DVC310 can handle 350/700W per driver and still has plenty of headroom on Xmax.

As you can see, I use Linux, and Winisd works perfectly.

Click to enlarge the pictures.

- Box design:

As I am curious on how a sealed box compares to a vented box (lots of fuss in the audiophile community about this)

I decided to build a box that is capable of giving me both options (convertible).

The box is made in 2 main parts:

Base part houses the drivers and has an internal volume which is good for a sealed setup.

The top is removable to allow a ported addon on top of the base part, enlarging the internal volume,

and equipped with a port.

Air tight sealing will be made with a rubber inlay or by means of sealing tape

http://shop.speakerenco.nl/afdichtband-voor-luidsprekers

I need to find a way to easily exchange the top lid with the extra ported box.

Perhaps something like this, but I'll try to find something a bit more eye pleasing.

http://www.ipsluitsystemen.nl/component/virtuemart/rvs/sloten1/spansloten1/rvs-spansluiting-77-3x20-verstelbaar-sluithaak-detail?Itemid=0#prettyPhoto[gal2]/1/

Depending on what sound I like best, the default setup will be either sealed or ported.

At this moment, I am thinking of defaulting to sealed for normal music and TV listening,

and occasionally for Home Theater purposes give the box an extra turbo boost with the addon ported section.

The driver will be fixed onto the housing with 'inslagmoeren'

to be able to easily remove and replace the drivers

in case I want to do some tuning to the box.

Underneath the box, damping feet will be mounted.

http://www.kieftijzerwaren.nl/IJzerwaren/IJzerwaren-overig/20147515/Trillingsdemper-RVS-M8-23.html

Kitlist/budget: about €770 without MDF, glue, ...

1 Hypex PSC2-400

2 Dayton DVC310-88

1 UMIK-1 cal microphone

1 MDF

1 Sealing tape

1 Misc (screws, ....)

1 Filling material

1 Binding post

Subwoofer construction

An easy to use drawing program is Google Sketchup, below is a link to youtube on how to draw a speaker box in Sketchup

https://youtu.be/ZCeUB63Sjks

Manufacturer recommended volume: Sealed= 52 liter Vented= 142 liter

Sketchup drawings of the sealed box part

Internal speaker board.