Sunday, 1 July 2012

2 way floorstanding speaker

New project, 2 way floor standing speaker.
Preparation for cutting

 
 

Slightly slanted front baffle design
 
Cutting holes for drivers and reflex port
 
Starting to take shape
 
With the extra long PVC reflex port glued to the front panel
 
2 pieces standing tall side by side
 
View from the back
 
Lining the internal wall with felt
 
 
Finally it's time to put them together.
 

It is time to put all the drivers in place to proceed for sound tuning
 

5.25" Bass driver is from Castle acoustic and 3/4" soft dome from Vifa
 

Inside is the modified 2 way crossover from the KEF C series speakers
 

After switching with a few different tweeters to match with the bass unit, i finally settled for a less expected combination which is a hybrid design tweeter. I would have to redo the mounting hole to accomodate the squarish magnet at the back of the tweeters.

A rectangular shaped hybrid tweeter. Don't know what brand but looking at the built quality is quite decent moreover they are made in Japan and also patented with individual serial numbers.


Up and ready for audition!
 

close up pic.
 
It is time to share a bit of my experience with this pair of speakers after a few listening sessions. First test i powered them with my old and faithful NAD 3020 Series 20 amplifier with Epos ES11 as the reference speaker, what immediately draws my attention was the coherence between the midbass and the high frequency units are superb. Worth the hassle of cutting and drilling holes to switch tweeters. Midrange is smooth with a good level of warmth and very well presented. The highs are crisp and detailed without any trace of harshness while the bass lines are clean and extended.

However the down side is that i will need to dail the volume up a little to push this speaker, comparing with my other speakers i estimated it's output sensitivity should be in the 86 to 87dB region only.

Conclusion-I am very satisfied with the initial test results.cheers Next is to power them up with different amplifiers and sources to see if they can perform better.
 
I cannot stop saying good things about this speaker when i switched driving them with my class A+AB 50 watter intergrated Duson PA50 amplifier combo with a Pioneer 20bit cdp. Improvements in every area and proven that the earlier 20 watter NAD is under powered. The soundstage opened up tremendously and bass has more slam and authority. It goes loud without sounding harsh or bright when pushed hard where i can continue listening on a pile of CDs for hours. I believed that it could be due to the natural characteristic of the hybrid tweeters itself that contribute to the overal oganic presentation. I can say that it outshines the ES11 in many areas.

I am eager to test them with more powerful amplifiers.Wink
 

The very final thing to do, dress them up with stainless steel wrap.
 

Looks very heavy and solid, no not only it looked heavy it is heavy! imagine 2 layers of 3/8" MDF with high pressure laminate on both sides.
 


Painstaking details











Labour of love I love you
Next, i am going to do modification on the midbass unit, to remove the dust cap and replaced them with custom made phase plug hoping for better midband delivery.
 

Dust caps removed, it looks like i will have to plug-up those ventilation holes near the neck of the cone before i can proceed to install the phase plugs.
 

Ok, i have the holes temporary covered with vinyl laminates to avoid the internal air escaping to the outside.
The immediate result of the initial test with the phase plug temporary in place is quite promising, fortunately the side effect on the bass is minimal.Rolling Eyes

I will need to work further on the wooden phase plug in order for it to fix properly.


The making of a Birch wood phase plug. First is to cut the wooden rod of a specific diameter in to desired length. Bore a hole at the centre to allow the fixture of a holding pole.
 

Next is to apply some heavy duty wood glue to fix centre pole in place.
 

Some knocking required to ensure the pole is properly fixed.
 

Well done.
 

A piece of foam gasket to seal the joining to prevent leakage.
 

Some painting to match the colour.
 

The installation of the plugs begins
 

I insert bamboo pegs to lock down the poles from behind.
 

Wolla! cheers Done!
 

Putting them back to the enclosure and ready for firing up
 



I am further working on a "T" base for the speaker using plywood and MDF
 



Painted in black and now have the N-nut screwed in to accept floor spikes
 
With the 3 floor spikes inserted. I always don't like the idea of having 4 spikes as its normally very difficult to get it stable especially on uneven flooring
 

Done!
 
It was the most satisfiying DIY project ever done by myself. After a few fine tuning and mix & matching process, they have now taken over the centre stage in my house and sings like a pro. They are driven by a pair of Antique Sound Lab tube monos hooked to a Promitious TVC passive preamp and a Pioneer 20bit CDP by AudioQuest cables. Quite difficult for me say how good they are but the replacement of my all-time favourite JM LAB Megane Carat with this Metalic Floor Stander is self-explanatory.

In conclusion, it worth all the effort of putting them together and it also make me start thinking how much they worth if the value of the speakers are determined by the quality of the sound in commercial markets.
 

 

 


Subwoofer DIY

My last year project, a DIY Subwoofer based on a 100W plate amplifier and 10" subwoofer driver.
Size 16"w X 12.5"d X20"h, approximate volume 50L.
Material-3/4" High density waterproof fibreboard laminated on both side (for wet kitchen cabinet application)
Design-tuned port with adjustable port length,currently tuned at 19hz for music listening.


Cutting- the board is so hard that jig saw or hand saw is a complete no no.
i have to use rotary cutter to do the cutting.

Putting the pieces together using industrial grade wood glue.
Binding posts are mount directly on to solid piece of wood for maximum strength
and to ensure airtight quality.

Cross and horizontal internal bracing are added.
Note the 2 standing pieces of wood also double up as a support for the
woofer magnet to minimize basket vibrations.
Hard felt and recycled cotton felt are use in different side of the internal walls to cut down standing waves.

Internal wiring is QED.

Putting the last piece together.

I use 2 pieces of wooden Chinese chess bond together and grind to
the shape of cones for the enclosure footing (4 sets).

Veneered in black
Note the finished wooden "chess" painted in black.
The 2 pieces of cross bar are layered by foam padding waiting for the driver
to sit on.

Time to wire the driver

I lined the edges with rubber weather strips instead of foam as foam tends to
deteriorate or soften in time.

Putting the adjustable spikes in place.

The driver is positioned with the 4 screws facing towards the side walls and anchored deep to the vertical plane of the cabinet to add strenght.
Done! time sit back and enjoy!