This mod is designed to balance out this effect by simply letting less air move through the foam. By adding thin material to the outside of the pads greater bass response is achieved. There is no reason to follow my mod exactly but I tested several different methods looking for the result of rebalancing the pads so they sound the same as the original Donuts supplied with the SR325is.

You can test this without doing a permanent mod – simply create a small paper wall around the edge of your pads and tape it into a loop so you can slide it on and off – this will give you an idea of what we’re aiming for.

So what materials have I used? Well if you find some materials you like better that’s great – this is a simple and basic mod that I would love to see others improve for their own tastes. There are copper tapes, aluminium tapes, the really skilled craftsman out there might turn some wooden sleeves or access to a vacuum former could yield great results but I’ve gone with what I know and my method is pretty non destructive and could be improved on at a later date.

You will need

Gaffer / Duct tape (or any reliably sticky and dense tape you like – Metal? Fabric?)
Good quality thin plastic sheet or card (I used a thin type of sheet acetate)
Sharp knife / scalpel
A decent cutting surface / board
Sharp scissors
A ruler
A pair of compasses (for drawing circles)
Tape measure

Grado GS1000 pad

Obviously you need to do a mirror image repeat of this for the second ear pad!

1 – Each pad will eventually have received 2 layers of tape around the circumferences flat outside edge. The first job is to accurately measure this circumference. Also measure the width you want the tape to cover. I made mine the exact width of the outside edge until the curved bottom lip.

2 – I ran a length of tape along the edge of my cutting board so that the perfect width was overhanging this edge giving me a perfect line edge to cut along with the scalpel. I added 1

cm to the length of the circumference to give a comfortable overlap when it is applied.

3 – So you should have a piece of tape a little longer than the circumference of the pad. Firmly and carefully apply this tape tightly so there is no slack but not so tight you distort the pad shape.

4 – Now it’s time to make the cone shaped insert – I found this the hardest part – First of all measure the diameter of the pad. Using the pair of compasses carefully and accurately mark out a circle with a diameter 2cm wider than that of the pad onto your card or thin plastic. Now mark another concentric circle from the same centre point but decrease the diameter by 3cm. Hopefully you are now looking at a 2D donut with a width of 1.5cm.

5 – It’s time to add the tabs that will keep this section in place, draw six small 1cm long trapezoid evenly spaced on the outside of your donut keeping the bit touching the donut to under 0.5cm and the other end a little wider.

6 – With the scalpel cut a neat line from the centre to the edge of one of the tabs. Now cut this crazy shape out as carefully as possible.

7 – Bend the tabs down and curl this shape along the edge of the conical part of the pad, you should be able to find a position where this sits neatly with the tabs overhanging the edge and a decent overlap, remove most of this overlap and use a small neat piece of tape to join this new conical shape and keep it fixed. It should now be sitting in its final position on top of the conical section of the pad with tabs sitting on the original layer of tape.

8 – This step is similar to step 2 with the circumference (+ 1cm) length bit of tape but this time we will make it slightly wider, only by about 0.5cm, so when it is wrapped around the circumference this time it will hold the tabs in place and have a small lip to tuck over onto the edge of our conical section sealing that edge.

And you should be complete!

Good luck and happy listening

More Information

For more information on the SR325is or any of the Grado Headphones range please visit the HiFi Headphones store.

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