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Old 29th December 2003, 07:27 AM   #1
diyAudio Member
 
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Location: Mumbai
Default transducers manufactured by me in india ,

Transducers in India – plus an article on a wide range of speaker related issues

Hi

I am a transducer design engineer in India and have a manufacturing set up in Calcutta ,
( My range of products and transducers are discussed down below like the 400 watt longthrow subwoofer )

This article has been inspired by my diy audio enthusiasm and to aid all constructors

To begin my perspective of diy is to construct and enjoy not only something one has made himself but to make better than what is available at amazing prices to impress all and construct for others _ have an identity , to be creative and be absorbed in a fulfilling hobby for hours

I have constructed all types of transistorized and mosfet amps from 30 to 1000 w rms (sine) , they have mostly been elektor circuits (though I have made some audio amateur and other designs too ) , most of the pcb layout and design / construction idea has been changed by me _ for better efficiency , ease to construct , thermal and long run stability , currently I redesign pcb,s and advise circuits to aid my customers , to suit their cabinets and budget (making all components , potentiometers spk socket / input sockets ets pcb mounting )

To revert back to transducers a speaker cannot play on its own it needs drive

To cut down to basics - In a complete speaker construction procedure there are three stages :

1.determine the T/S parameters of the driver
2.run it through box design calculations / software with the cut off frequency size and type _ bandpass / bassreflex etc in mind
3.construct the box solidly assemble the speakers

then perform final measurements with a microphone plus software analysis of the speaker

upon this test result and personal taste

the crossover can be tweaked , notch filters and impedance correction put in and phase tuned

the above is nirvana but it does not include power handling , the sweetness required from hi fi speakers or the accuracy factor in professional audio / monitors
(this topic would go into realms if I have to put down all that comes instantly to my mind)

Reverting to important issues governing diy and speaker design

1 . The speaker matching with the amplifier ,

I can provide a double magnet (155 to 230 mm) subwoofer in a lambada extended pole underhung sfg topology magnet structure with a kapton voice coil with imported aluminum wire voice coil lengths in excess of 60 mm with a xmax of 25 mm at 4 ohms , a imported non-press paper rubber surround cone (which totally absorbs all mid + hi frequency due to the cone design)
and
if the user constructs the most powerful IC amp it will not match
infact it won’t match a 150 w rms transistorized design using latest Toshiba ets transistors
the reason – the magnet structure is over damped
now if it was the crescendo mosfet amp then we are going somewhere ,

Two

the type of the transducer , its power handling , has the voice coil size been increased blindly to increase power handling without magnetic efficiency and x – max in mind ?

the type of cone used , pressed paper , semi press paper , non press paper , felted composite , reinforced ets ( this decides how the speaker will sound )

the motor structure , sfg (symmetrical field geometry magnet structure) , for full range and pro drivers if there are eddy current shorting rings , other shorting rings employed to extend frequency response , linearise impedance , improve transience

the vc material and wire , the vc inductance – 2 layer , 4 layer , dual vc type etc

the suspension system and compliance
surround material , eg rubber then type natural or synthetic ets , the extent of the roll of the surround and its match with the spiders

the construction – at the end all parts of a speaker is held together by adhesives , the quality of adhesives used / and the process of manufacturing , for eg if I repair a toy with a epoxy hardener type adhesive and do not allow for the correct drying time …

at the end all manufacturers are increasing production speeds

To this end I have spent a considerable time in exploring speaker matching (helped by my audio electronics knowledge) to guide my customers

And

My transducers are

1. Symmetrical field motor structure (magnet and plates design) of all types , extended pole piece and bumped or dual magnet design to allow long travels of the voice coil

2. All types of high quality paper cones , non press , semi press cones , fully pressed and
felted cones

we even design our own cones and have them manufactured to suit application

Cones developed for specific application _ subs , mids , full ranges

For eg my subwoofer’s _ nonpress paper rubber surround cones do not require a passive or active c/o it naturally rolls off at about 200 hz to absorb all mid and hi frequencies mechanically

4. kapton former and imported – eldra voice coil wires and high temp vcs
with voice coil lengths upto 60 mm and x max of 25 mm at 4 ohms

this allows the coil to remain in the magnetic gap during all instances of cone excursion

where as most manufacturers ( even the ones discussed in diy audio ) yet use short coils even in their subs resulting in the coil to leave the magnetic field when the cone moves , this would result in distortion at above 40 to 50 w rms and these speakers will always have the tendency to be inaccurate that is : the nature of sound they will produce tend to be same with all types of recording , where as deep bass should roll but punchy tracks should impact from the same driver

5. surrounds and spiders developed for long throw purposes ets
surrounds in own material – rubber and foam in own dyes in different densities , hardness and roll profiles

Power handling of my woofers are

from 30 w to :- 100 w (4 inch driver) , 30 to 150 w (5 to 6 inch driver) , 40 to 200 w (8 inch driver) , 60 to 250 w (10 inch driver) , 60 to upto 400 w (12 inch driver) w = amplifier power at sine wave rms

just in the 8 inch range and 30 to 100 w category I have 22 separate cones and different models

Our transducers are designed for its specific application with power handling and type hifi or pro audio in mind , not just a woofer cone thrown into a full-range magnet coil design as employed by other manufacturers named in a few article s , one Mumbai manufacturers drivers known to be exported do not even confirm to its t/s parameters or its power handling capacity or the Xeroxed measurements given with the driver , and their idea of a subwoofer is a four layer voice coil which due to its voice coil inductance has a lower mid/hi frequency response but come on what about this reducing the voice coil height and then we are left with the problem of the coil leaving the magnetic gap when it moves subs require a large coil winding height – thus the term long throw transducer


The above discussion generally is applicable to hi fi speakers

I am a sound reinforcement enthusiast and pro audio is too involving to make a start here

To all my friends out there who are sound engineers (me being fanatic about discos) phase and time are your enemies in multiple speaker systems

These are a few of my products in this range

I have pro audio drivers mainly amazing full ranges from 5 to 15 inch

12 and 15 inch are for sound reinforcement and pro monitors and are rated at 200 to 300 w rms

Low frequency transducers

jbl , ev , eminence type 600 w rms 15/18 inch low frequency transducers of ets

using company replacement parts
that is company : cone , edge wound voice coil , spider , dust cap , gasket – reconing kit

in my own aluminum die cast basket

with the same sfg magnet pole piece structure of the original driver

using general magnetics magnet and soft metals as used by jbl etc for their magnet plates

at amazing prices (lower than p – audio)

(this is dependant on my importing the re- cone kit but I plan to have most in my inventory all the time next year)

my own 600 w rms transducers

using imported cones and spider

own high temp aluminum wire voice coils on kapton former

sfg extended vented pole motor structure

this is also available in a dual magnet design to compensate for the tiny loss of the round wire voice coils to an edge wound one by increasing the field strength thus resulting in similar efficiencies of a edge wound voice coil driver

this is of course at a much lower price than that of the above

little about me – that is us , there are two of us , suranjan das gupta and vivek jaiswal - aka viki who are both transducer design engineers and audio electronics enthusiast ,

we can be contacted at
Suranjan Das Gupta – 9830005575
Viki Jaiswal – 033-30907825 and 033- 30912935

hunter_audio@yahoo.co.in

Hunter Audio , 77/B Amherst St , Calcutta 700009


We are also looking for a friend Tanmay Rao who was with us here in Calcutta but have now shifted to Bangalore . Our tel nos have changed if anyone is in touch with him please mail me his contact no / mail- thanx
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Old 29th December 2003, 09:50 AM   #2
palesha is offline palesha  India
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Join Date: Nov 2001
Location: Pune India
Congrates!
Ur message looks like a .phd note. U r telling about making highend speakers in India. It is very nice. Before few years back i hv gone through the project of making the speakers. But found that none of the high quality raw material is available in India. Peerless people r mostly importing the raw materials. How u can afford to import the raw material in such a small scale? Further the low carbon iron plates & t yoke r not available easily here. The T yoke must be one piece colled rolled one. this is not easily possible in India. Further the high quality cones r not made in India. Do you hv imported the cones in high quantity as required for imports? Then the chemicals & high quality high temperatute self bonding copper wires r also not available in India. It is difficult to keep them in stock because of their low shelf life. Due to this it becomes unviable to make the high qualtity speakers in India unless u charge for all this loss. Then it becomes costly. Further for speaker designing also special softwares r available. Where u can design the speaker T/S with the help of computer. Further for magnet assembly optimisation also need some softwares to be used. This all infrastructure is very expensive. Also u need experience & opportunities to master the technology.
This is just to give u & all my Indian friends to know more about
Speaker making. i hv almost visited top cone manufactures in India & abroad . Further i hv visited lot of speaker manufaturers in India, taiwan & China.
I still wish u all the best & successful venture in making the high quality driver. I really appreciate ur efforts.
Mahendra Palesha
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Old 29th December 2003, 10:38 AM   #3
sangram is online now sangram  India
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Join Date: Sep 2002
Location: India
Good to see you trying to put Cal on the hifi map of India, hopefully the world.

Don't want to sound demeaning, think your post should be in the trading section as you do have contact details and are in the business of audio. Maybe a mod will move it for you.

On the other hand, really great I stumbled across your post, you seem pretty well clued on into loudspeaker design and acoustics. Palesha brings up an interesting question on the materials used, but I see that using recone kits from the better manufacturers is a smart move anyway.

One thing that seems to be missing from the DIY market in India completely, is compact (4" and below) full range transducers like TangBands, shielded for video use, with high (93 dB+) sensitivity and neutral/open response. Ideal for DIY PC/HT setups, and the ability to daisy-chain for high power handling... Maybe that is an opportunity?

The other thing are good quality midrange and tweeter transducers. those are very hard to come by, and a max of one or two options exist for the quality-conscious DIYer.

One nit I still have to pick is that you seem to be focused on speakers with power handling and more power handling. I would think another direction can be toward sweetness, quality, neutral, open and accurate. That would really cause you to be positioned well. Maybe you can give box recommendations (it's a just a xeroxed sheet of paper) along with your product (if you are planning to be on the market as opposed to only custom installs), crossover suggestions and component values, etc.

Most people I know in India are anyway deaf as a doorpost, can't hear the difference between a 64 kbps and 320 kbps MP3 file, so what the hey. I am writing to you offline with a few contacts you can contact to spread the word and initiate inquiries. One would be a proper shop in Chandni, who does know quite a few enthusiasts, and one is a friend of mine who dabbles in this stuff.
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Old 29th December 2003, 11:10 AM   #4
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Location: Melbourne, Australia
How about a website with specifications and pictures and prices and buy-on-line?
__________________
Best-ever T/S parameter spreadsheet.
http://www.diyaudio.com/forums/multi...tml#post353269
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Old 29th December 2003, 12:47 PM   #5
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Join Date: May 2001
Location: Bangalore, India
Big Power Handling, upto 600watts RMS!! But you have not said a word about Sensitivity. Bl or Force Factor is another that you could quote when you talk about big drivers in Pro-Audio.

My brother and I have a Sound Rental Company (Credence Audio-Visuals). We have 600 watt 18" & 15" EV driven Horn loaded Bass Bins, 500 watt 12" DAS driven Mid-Horns and 250 watt DAS Compression Drivers. We drive these through Dynacord (German) Power Amps. So a head to head comparison will be interesting to me with future expansion in mind.

Thanks,
__________________
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Old 29th December 2003, 01:10 PM   #6
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Location: 3RS
Default You have everyones support.

Hi Hunter Audio,
You should now put up a web site with all details of your drivers and the possibility to order them like Circlotron suggested.
While you may not ( may not !) come up to the best available it is a good chance to see where you stand and get some feedback from people who have used or heard the best.
That gives you your global position and you can work on narrowing the gap between the best and your products. This will obviously take time and energy ( and money?) - lots of it !
If you can even come up to Vifa/Scan Speak standards
(consumer audio) at Indian prices , you probably will have the whole Indian market !!! Why do you think foreign companies are coming to India NOW ? It's the next greatest Hi-Fi market. If you work with an open mind and attention to the smallest details you can't loose . Let others blow your trumpet when the time comes!
Wish you guys all the best.
Cheers.
__________________
AM
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Old 30th December 2003, 07:31 AM   #7
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Join Date: Dec 2003
Location: Mumbai
Default reply yo your qs and posts

i would like to divide this into sections and firstly reply to palesha ,

1 st - section - motor structure

first of all , lets take apart the motor structure , other than for hf units _ which i will revet to later

cold rolled (or forged) low carbon material is used to improve in lay terms the magnetic field flow therby increasing the field strength at the magnetic gap leading to optimising the efficiency of the magnet used and larger bl / damping etc
a ,
cold rolled t yokes even in complex designs are available in delhi fm a local manf and alcast (alcast adds come out in hi fi news , india) , but the carbon content is a guess
my way out ,
i have gone through a lot of old full range drivers , isophone , rola ets (alnico mags) in my knowledge low carbon steel was used mostly then (nowadays its chinese steel with commercial manf) and now most of Myers audio (there spks are astounding) magnetplates
these were (for myers are) all tightly machined high accuracy units , it is difficult to maintain tight tolerances with forged t-yokes , this has been pointed out in the sounreinforcement handbook , the chapter on transducers by some one very high up with EV im forgetting his name , Martin Colloms has mentioned this too
therefore in my way i select the alloy steel - if required i have it tested (luckily i have made spks for a customer turned friend) who has a mattelurgy (spl?) lab and then have them machined , the t,s are grinded to exact size and -riveted- to the back plate
all my t yokes are machined , mostly t shape , or extended pole to have a symmetric motor structure , by the t shape pole piece is difficult to forge ...
b,
in above part a , i discussed the need to use low carbon / other materials to improve - magnetic flux at the magnetic gap ie between the top plate and the polepiece (then have them machined etc etc) - another process - i call this one , bangla/desi process - use a double magnet motor structure , throw in one more magnet ...
but this may over damp the drive unit and amplifier matching may be a problem , another it doesnt work at all with hi frequency drivers

i can go into hf units if someone is interested ,

section 2 cones

a non press rubber surround paper cone with a good roll profile in 12 inches capable of handling 100 to 200 w from _
penshien (taiwan - chinese) 5 to 9 $s i have quotes from Kurt Muller (UK plant) and Nu-way (Usa) they were of-course more than this , other than ordering a large no. sending a lc being stuck with 1 type of a cone eg coil neck (coil diameter size) there are other manf probs , :- there s a way out

firstly understand how a cone is manufactured , how a non press cone is manufactured , the pulp , fibres , beating etc - and make your own cone ,

i do not want to go into lengths on cone manufacturing here
but if any one is interested i will discuss it

secondly understand rubber moulding , natural - synthetic rubbers have a few samples tested for composition ets , make your own moulds , try different hardnesses and make your own rubber surround

thirdly devolop a high quality rubber to paper adhesive

i have made my own cones

can make them in any shape - neck dia , any thickness / hardness ,
my own surrounds ,
in large roll profiles - for extreme excursions the type we like
in the same mould i can mould a 35 hardness rubber _ suits for hi-fi or a 60 hardness rubber _ suits car audio

result _

i have 8 to 12 inch rubber surround nonpress paper cones which cut of at around 250 hz totally absorbing most of the mid band a and all of the hi bands - when fed a full range signal - Without any crossovers and boosting the mid and hi bands from a tone control / eq ets

all my cones are unique - and have killer looks devoloped by me ,

foam surrounds are devoloped by me too

section 3 - wires

i use imported wires , which are very carefully selected , some alloy types , or copper and alumunium (round) wires -
some are self solderable as mentioned by you , but spk industry uses self solderable in my opinon to ease and speed production , i use a insulation removing chemical (please i dont burn the insulation !) the wires are all high temp insulation to 230 deg centigrate mostly , good formers , kapton , glass fibre only in high risk spks alumunium (anodised - black) , the voice coils are coated with a high temp black backing chemical and baked

and since i design the motor structure cooling is employed according to needs

section 4 pro audio

jayaraj thanks 4 getting back on this i need to discuss on non lateral fets with you , by the way dynacord has been bought out by ev , i think you know, and they have great torroids in them

first and foremost _ all spks which should be compaired head to head should be in similar rock solid cabinets and should not jar

bl - is the factor of the number of turns of the voice coil in the magnetic gap * the magnetic field strength (lay mans terms employed)
a 4 layer coil has a larger bl than a 1 layer edgewound one _ thats why the killer bass drivers of car audio are all four layer coils with a winding hight above 1 / 1/2 inches (including jbl) _ i dont know of the gti latest series never had or think will have an oppurtunity of opening up one of those babies

then the magnetic field strength can be increased by a dual magnet

in my intial pro audio driver discription i mentioned i have a model with a double magnet that was designed with exactly your qs in mind _ sensitivity , with an edge wound coil efficiency is improved immensly as maximum wire is in the magnetic gap without and space lost as in the case or a round wire winding , there fore i use a similar light weight alumunium wire coil (round) in a double mag config

yes if the cost factor is kept in mind i am ready for a bang on comp , with the driver - which has all of my parts other than that of a imported cone / spider

using company replacement part kits in own basket / motor structure - drivers , ev kits are exactly original , jbl mostly are and so are peavey , fostex ets , the cones are kevlar reinfoced .

by the way sonodyne uses p- audio calls them imported from australia , and i have tested one which blew at 380 w rms after 30 mins (not a mos amp , a toshiba trans output amp)

section 5

i have cone tweeters readily available , 3 inch and 2 inch

i had made dome tweeters , all types including my own moulded alumunium domes with phase plug ets , moulded front plate ets ets
and had mostly solved the problem of them not being able to handle high power and the coils either disconnecting or burning (speaciality of the philips one)
but
i am in bengal , calcutta - has no takers , there are not many to spend even rs 250 on a dome

my cones employ a impedance stabilising ring _ as in celestion models and a shorting ring on the pole piece to reduce eddy currents , therby distortion , the cones have been devoloped by me , they are fully pressed , i am planning to devolop felted cones too

section 6

i have foam surrond 4 inch and 5 inch woofers from 50 to 150 w rms _ cones ets again devoloped by me

with rubber surrounds there tends to be a power loss ,

i have rubber surrounds too

a mid woofer using a alumunium coil like the the morel or scanapeak rubber- surrounds can easily be made

section 7 mids

for mids i love to use full ranges in their own ply cabinets

i have 4 ,5 , 6 and 8 inch fullranges from 50 to 100 w

i like fullranges since they sound open freeflowing do not pose problems for the c/o design and produce mid-bass to a degree

lastly a web site with price lists , frankly speaking i cannot generate the funds as of now ,

thanks for the replys i will make the best possible effort to aid any discussion

suranjan das gupta
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Old 30th December 2003, 07:53 AM   #8
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Default forget 1 thing

hi

section 8

for drivers to have a handsome power handling below 4 inches the motorstructre needs to be designed with neodynum mags

if any one would like to know the reason i could discuss on it

another is the manufacturing process - my way it will become too expensive as i can make a 8 inch woofer for which i have a fixed customer in the same time

one has to upgrade manufacturing process with turntable adhesive dispensors , cnc controllers ets

and they need to be ferro fluid cooled , ferro fluid is expensive and very difficult to devolop like the chinese ive tried devoloping it but failed , the difference is i didnt sell it , but there is a lot of fake cooling fluids in the market and we all can guess where it is coming from

by the way the cone size it self poses a few problems ,

and the bose jewel cube - neodynium and all and some snail port ! has a - 6 db point at 13 khz would not like to talk about the lower cut off , power handling _ 20 w
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Old 30th December 2003, 11:42 AM   #9
palesha is offline palesha  India
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Happy to note the efforts taken. I wish him all the success. I hv personally visite TB speaker office in Taiwan and had discussion with them. Then they came to India & visited us in Pune. They were ready to co-operate by all way. But the quantity required by them were huge & unviable in India.
I hv also visited the top two cone manufacturers in India. Further i hv visited many speaker factories in India, Taiwan & China.
I hv then decided to import what is required from them. Presently i hv imported few woofers & 2 way neodymium speakers. I am presently supplying to many professionals in Mumbai.
About making speakers i feel that now there r two ways. If u hv all the testing & designing infrastructure then only u can good speakers. U must hv all kind of raw materials at ur disposal.
I hv gone through the articals of the speaker designers from USA. I hv personally met Mr. Mike Klasko from USA. He is very famous speaker design consultant. He charges US$ 5000/- per month to many chinese & other companies.
Other method is to rely on experience, try & guess. This way u can't be assured of constant quality.
I am not here to discourage anyone. I am strickly expressing my personal experience & views.
Mahendra PAlesha
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Old 31st December 2003, 05:16 AM   #10
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Default Hunter Audio drivers

Till you have the website up and running, can you please post brief specs of some of the drivers that would interest the DIY community in India.

We all have been searching for good drivers in India with published specs.
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