4 inchers modded within an inch of their lives - diyAudio
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Old 23rd January 2007, 10:41 AM   #1
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Default 4 inchers modded within an inch of their lives

Here are some picks of some experimental mods I talked about over on full range driver forum to some cheap 4 inch PA drivers, the mods include:

1) Tissue paper to outside cone to improve joint to surround

2) PVA g;ue to front and rear of cone

3) Whizzer heavily PVAed

4) Dustcap cutout so as a small section in the centre only radiates

5) Serrating the whizzer

6) 5 felt pads to cone behind whizzer

7) Legs cut out except the one with the contact wires and replaced with wire which is araldited in

8) Lower part of frame surround also cut down to add extra breathing space

9) Edge on lower frame surround has rubber tubing glued to it to direct the air smoothly over the edge

10) Bluetac around edge to smooth flow further

11) Plastic desert cone inverted over magnet to smooth flow behind cone and in reverse direction

12) Plastic cone filled with rubber matt, but will be filled with expanding foam on final drivers

13) Junction between plastic cone and frame filled with bluetac

14) Spider and surround treated to a good dose of virgin olive oil, which seems to free them up nicely and no downsided on previous drivers I tried this on

15) Small rubber half dome applied to centre cap as a type of dome tweeter.

I will include a socond post with the std driver to compare

These things are about 94db efficient and they sound amazing on an open baffle when used with a sub and an active filter to stop frequencies below 50Hz.

Oh and they sound absolutely nothing like the original at all

They extend to about 16khz no worries and I have used a rear firing super tweet fro additional ambience.

Have yet to try them in a double bass box, but should be good as I am using a far less modded version in some at present with very nice results.
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Old 23rd January 2007, 10:42 AM   #2
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Here is the rear of the driver
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Old 23rd January 2007, 10:43 AM   #3
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And here is the original driver, rear view
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Old 23rd January 2007, 10:44 AM   #4
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And of course the front of the original
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Old 23rd January 2007, 01:04 PM   #5
poynton is offline poynton  United Kingdom
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Default How cheap is cheap???

HI.

Interesting if not dramatic mods !!!!

Can I ask the brand and unit cost of the speaker

I am just about to embark on my first attempt at speaker building.

Andy
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Old 24th January 2007, 06:32 AM   #6
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Hi Poynton

Oh there pretty cheap, $12.50 each in OZ or about $9.50US.

They are on special at the moment for $25.00 a pair but normally they are about $17.00

There from altronics

Heres a link

http://www.altronics.com.au/index.as...=item&id=C0626
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Old 24th January 2007, 03:46 PM   #7
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Hiya zero one, that's a pretty impressive set of mods. After poking around here I'm starting to become interested in driver mods, but haven't yet stumbled across a good collection of information about it. Searches I do on 'speaker driver mods' seem to cast too wide a net. Is there a good collection of information about this topic out there on the net? If not, perhaps people would be interested in pouring info into this thread?

I've got questions like:
What problems does each of these mods address? What are the sonic charecteristics of the problem and of it's resolution? Some of these I can motivate just by looking, others (tissue paper? dustcap cutout?) not so much. What considerations should lead me to perform a given mod or rule it out? Do these mods change the design parameters of the driver?

could you dish out some specifics of the execution on #7 and #14?

I am interested in a first driver modding project along these lines. Hmmm maybe that pioneer 8"? Or perhaps a friend's cheapo towers where the marketing dept kept coming back with "can we get more drivers in there?" If I can talk him into it... Hmmmm ideas, ideas....

thx!
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Old 24th January 2007, 10:27 PM   #8
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Hi Adam

Your right about sites on speaker mods, not so easy and I have yet to find one definitve source, and of course you find many conflicting ideas

Most mods I have made in my audio gear have been "gut feeling" derived, and many have been failures, I do a lot of tweaking so I guess thats to be expected. I go only on what my ears tell me.

With these drivers most of the mods are driven from past experiments.

All mods will change the parameters of the driver, but I don't get hung up on that all I'm interested in is the final sound which I derive from lots of fiddling, but for those who want to use speaker box design programs it would be a bit messy I guess.

Here are a few of my thoughts, but don't take it as gospel.

The tissue paper is used to strenghten the link between the cone and the surround in a sort of staggered fashion, there are three layers with the each having a different width, I feel this spreads the stresses at the interface better and improves bass reproduction. In my first experiment this was very pronounced so well worth while.

Of course the tissue paper does add a little weight along with the glue, but as these are PA drivers that tend to be quite forward in the mids this actually helps for a smoother result in my case anyway.

The removal of the legs does two things, cuts down HF relfection through the back of the cone and allows I feel for better and more balanced rearward airflow that I feel substantially improves the lower bass. The lack of HF relfection seems to clean up the mid/highs a bit

The use of round legs I feel gives a much smoother less disturbed air flow in both directions which should allow the cone to respond more accurately to any input, ideally I guess the legs should be sort of egg shaped in cross section but I won't go there.

The rubber tubing over the cutdown edge does much the same thing, when I looked at the frame above the rear of the surround area I felt it must cause some problems with smooth airflow as the frame lips on pressed frame drivers curve inwards with a sharp internal lip and airflow I feel gets directed into the dead area under the lip and would cause interactions with the air moving directly above the surround itself, which on 4 inch drivers is a pretty substantial proportion of the whole amount of air being moved in total by the rearward movement of the cone. Once again a gut feeling but the sound is good.

The treatment of the spider and surround with virgin olive oil is intended to add a little more flexibility, probably a does the same thing as breaking the driver in. only pretty much instantly. Anyway the fisrt time I tried this I did a back to back test (with ears) one speaker virgined and one not, the difference was pronounced, basically the sound was smoother all round.

I brush on three very light coats with an artist brush, on the faom surrounds they soak right in no problems, the spider needs to be treated lightly.

Now the dustcaps mods....

First up in std form these drivers are pretty squaky, so I tried phase plugs, this smoothed the sound massively but I also found the highs were now pretty reserved. The thing with these drivers is the coil former is actually a cardboard tube, and the dust cap adds a lot of strength to the top end of that tube, unfortunately I feel the hard dust cap also interacts with the whizzer to produce phase problems and harsh treble in some cases.

My feeling was if I could maintein the stength and remove the interaction I would get a better result, hence the cutout design, it works really well and comprared to the phase plugged drivers the difference is huge, the phase plugged ones really need a super tweeter for best results, this version sounds pretty much as good HF wise as the tweeter augmented version but with better upper mids.

I think the serrations on the edge of the whizzer also help a bit but I didn't get to do any tests with just this mod alone in place.

I think cutting out the contre cap this way also removes a little issue in that with these drivers the centre cap pretty much seals the area inside the former, this means there is air that has to be compressed with every stroke of the cone, I guess it adds damping but I also think it reduces the abiltiy of the driver to respond to electrical inputs as quickly as possible and possiblly also reduces bass response.

Overall I think modding drivers can be very beneficial, but I think using cheap drivers is the way to go at first anyway, less to loose.

If you have 3 drivers you can mod one as a sacrificial unit and compare it at each step along the way to an unmodded driver, when you get the result you want then mod the other 2 for final use.

Well I hope this helps and happy modding.
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Old 24th January 2007, 11:31 PM   #9
tinitus is offline tinitus  Europe
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As far as I know food oil hardens as time goes by - on surround at least use silicone oil

Looks like a nice driver - I would like to try a very thin coating with polyurethane glue (foam), much easier and very effective

Chassis, I would just strengthen it with small pieces of wood and pack some felt around it


But ofcourse you could go radical, and build a new chassis of wood - thats what I am doing, with another selfmade driver
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Old 24th January 2007, 11:43 PM   #10
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I have a page on 2 of the mods i continue to use over 7 over again....

http://t-linespeakers.org/design/tweeks.html

dave
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