Re-designing speakers

[doors666]

I will quote from wiki, for which link is already given above.

* Sd - Projected area of the driver diaphragm, in square metres.
* Mms - Mass of the diaphragm, including acoustic load, in kilograms.
* Cms - Compliance of the driver's suspension, in metres per newton (the reciprocal of its 'stiffness').
* Rms - The mechanical resistance of a driver's suspension (ie, 'lossiness') in Ns/m
* Le - Voice coil inductance measured in millihenries (mH) (Frequency dependent, usually measured at 1 kHz).
* Re - DC resistance of the voice coil, measured in ohms.
* Bl - The product of magnet field strength in the voice coil gap and the length of wire in the magnetic field, in tesla-metres (Tm).

Fs Resonance frequency of the driver
* Qes Electrical Q of the driver at Fs
* Qms Mechanical Q of the driver at Fs
* Qts Total Q of the driver at Fs
Vas Equivalent Compliance Volume, i.e. the volume of air which, when acted upon by a piston of area Sd, has the same compliance as the driver's suspension:

* Xmax - Maximum linear peak (or sometimes peak-to-peak) excursion (in mm) of the cone. Note that, because of mechanical issues, the motion of a driver cone becomes non-linear with large excursions, especially those in excess of this parameter.
* Xmech - Maximum physical excursion of the driver before physical damage. With a sufficiently large input, the excursion will cause damage to the voice coil or other moving part of the driver.
* Pe - Thermal power handling capacity of the driver, in watts. This value is difficult to characterize and is often overestimated, by manufacturers and others.
* Vd - Peak displacement volume, calculated by Vd = SdXmax

If this whets your appetite, you can read more at wiki and elsewhere. These parameters basically describe the driver scientifically. Given these parameters, and a cabinet internal (air volume inside the speaker) volume, softwares like winisd will model the speaker and show you the frequency response curves (in an anaechoic chamber, not in room). It also shows you a lot of other useful information. e.g. in a ported system, if you go below a certain frequency, your woofer xmax will be exceeded and it will blow.

The software usually validates these parameters also against each other and reports any issues, this only works upto a certain extent. if the numbers are way off, you will get weird results.

Usually, you really dont need to know most of the calculations as softwares will do most of the stuff, assuming you already have t/s parameters. But in your case, since you dont know the parameters and you might end up finding out yourself, it will help if you get a decent understanding of the parameters and its impacts. Its always a good idea to have some info on these (and other related info) as it will give you a decent understanding of how a speaker really works, the relation between cabinet size and drivers.

crossovers are another nightmare, but i am still learning that, so i think its time for some guru to take over...

 

[t.antony]

My query is, what aspects of speaker design are determined by the TS parameters

These parameters define the electrical, mechanical and acoustical characteristics associated with the driver. Most enclosures contain an air column that has certain mechanical and acoustical characteristics provided by the shape and size of enclosure. When TS parameters are known, the behavior of the driver in such and enclosure can be predicted.

In short TS params are instrumental in almost every aspect of speaker design: from choosing the type and size of enclosure that suits the driver, designing a crossover and predicting the frequency response.

You can get a basic idea of some enclosure types from this link - Loudspeaker enclosure - Wikipedia, the free encyclopedia

Regds...

 

[doors666]

try out winisd pro, its free. install it and choose some driver, specify some iternal volumes and see different graphs available. read the help file first (its not very big). try to enter the T/S parameters for a new driver not listed in its database (method given in help file). Play around with it for a few days and you will get a good idea about the whole thing.

 

[captrajesh]

Where you purchased fabric cone tweeter from ritche street and what is the price? Please PM me. I am planning to purchase that.

Don't know the name only the location. Will check when I visit that place & let you know.

i look at it this way -

captrajesh has identified a DIY project that he wants to do without involving himself (too much) with technicalities and specifics-

captrajesh will (perhaps) want to make something that will warm his heart each time he looks at it - perhaps, run a hand over the black piano gloss finish and shed a tear over the magic(o) he has created! - certainly, it will be a conversation piece

Bang on Suri. Yes, That's what this project is about.:thumbsup:

captrajesh can add fail-safe this way - look up proven designs on the www - with same driver dimensions - and similar external front baffle and driver arrangement - and similar (approx) internal volumes- i have seen some scanspeak designs - and i think a sonus faber (clone) design is available - with almost the same dimensions as captrajesh's speakers (and the magico mini shape)

Couldn't find by googling. Could you kindly provide me the link if possible??

Maybe its a good idea to calculate the t/s parameter and see the response in software.

Measuring TS parameters and simulating in a software like Winisd is a proven and scientific method for getting best results for any driver.

These parameters define the electrical, mechanical and acoustical characteristics associated with the driver. Most enclosures contain an air column that has certain mechanical and acoustical characteristics provided by the shape and size of enclosure. When TS parameters are known, the behavior of the driver in such and enclosure can be predicted.

In short TS params are instrumental in almost every aspect of speaker design: from choosing the type and size of enclosure that suits the driver, designing a crossover and predicting the frequency response.

try out winisd pro, its free. install it and choose some driver, specify some iternal volumes and see different graphs available. read the help file first (its not very big). try to enter the T/S parameters for a new driver not listed in its database (method given in help file).

Sorry guys, was out of station and back only now. It is a pain to go through the posts on mobile and a bigger pain to post messages. So here I am.

I'm really thankful for all your valid suggestions. AFA I can understand, TS Parameters are required to predict the driver behaviour in the given enclosure.

But since I already have a decent sounding cabinet and am satisfied with the sound for the given application (Improve SQ of TV) and if I make a speaker of the desired shape with exactly the same internal volume of the original box as suggested by Suri, do I still need to check for the TS parameters?

 

[suri]

in connection -

Preamplifiers & Mixers

looks like something you might need!

 

[t.antony]

But since I already have a decent sounding cabinet and am satisfied with the sound for the given application (Improve SQ of TV) and if I make a speaker of the desired shape with exactly the same internal volume of the original box as suggested by Suri, do I still need to check for the TS parameters?

Since this is a ported design, the dimensions of the enclosure and position of the port could be as important as volume as they are directly related to the behavior of the air column inside. Constructing a cabinet taking only the volume into consideration might not give you same results. The following suggestion looks like a worthwhile try.

...or change the front baffle to wood.

If you plan to follow this approach, consider countersinking the wood baffle from the inside equal to the thickness of plastic baffle and fixing the woofer from the inside at the exact x and y co-ordinates as before. This will keep the internal volume and air column properties almost same. IMO a piece of 9mm or 12mm teak plank should do good for aesthetics and rigidity.

Regds...

 

[captrajesh]

Where you purchased fabric cone tweeter from ritche street and what is the price? Please PM me. I am planning to purchase that.

Don't know the name only the location. Will check when I visit that place & let you know.

Hi

The Shop is Raj Lakshmi Electronics, #8, Md. Hussain Sahib St, Um rao Complex, Shop #2 (Ritchie street area) Mob: 98940 17177

 

[madvenu]

Hi

The Shop is Raj Lakshmi Electronics, #8, Md. Hussain Sahib St, Um rao Complex, Shop #2 (Ritchie street area) Mob: 98940 17177

Thanks Capt. Rajesh

I spoke to Mr. Motilal and ordered a few sample speaker drivers from him.
I was also on lookout for drivers - especially fabric dome tweeters.

Interestingly, he has some 5 1/4" Easttech woofers for Rs 175 !!! and the tweeters for Rs 50 each !!! Others DIYers --- Its a steal

Will let you know next week about the drivers after I receive them..

Cheers
venu

 

[Vijay KD]

Thanks Captain.
Do they have any 8" woofer and 10 or 12" sub woofers? I am planning to go there next weekend.
Thanks for your info.

 

[captrajesh]

Do they have any 8" woofer and 10 or 12" sub woofers?

AFAI noticed, he has drivers of all sizes and shapes though do not know about specific sizes.

Why don't you talk to him over telephone to check it out.

 

[madvenu]

Hello All

Another source for drivers is Peerless India distributor Varsha Electronics...
Just called up Peerless India phone numbers as listed on their website and was put through to a gentleman Mr. Sunit S. Over 8 years with Peerless, but sadly for us will be leaving for further education to USA....

Wonderful person - he explained the benefits of the many drivers they make for the Indian market and was very helpful when I said I was a DIY speaker builder. He recommended that I pick up a pair of their low resonance fabric tweeters with a Resonance Freq = 800 Hz and frequency range from 1k - 20k...

He then asked me to get in touch with their distributor in Ghatkopar / Mumbai. I noticed the name of this distributor before: Mr. Jeetubhai -- another DIYer from Mumbai has a blog somewhere about how he built his speaker and saw a pair of Kevlar woofers with Mr. Jeetubhai. If someone remembers this blog link, please forward to me... ( And by the way, they do have the kevlar woofers for 1500 Rs a piece - Peerless Denmark ones... )

Anyway - I have ordered some sample tweeter drivers to check out. Good thing about these is that we get the manufacturers specifications. Bad part is that they are pricey -- 700 - 900 per tweeter..
But hopefully still worth the price .. will let you know more when I receive them..


Cheers
venu


PS: DIYers interested in the Datasheets (4MB pdf ) / catalogue / contact, please PM me.

PPS: The link to the other article: http://www.dhandanought.org/tcpip/site/node/24

 

[rikhav]

My first real introduction to hi-fi was through Tarun ji and that too by just exchanging emails.
I had many wrong notions about hifi and he cleared many of them
Never met him or heard his speakers but would really love to. Infact he is a member of hifivision but sadly is not active at all

 

[captrajesh]

another DIYer from Mumbai has a blog somewhere about how he built his speaker and saw a pair of Kevlar woofers with Mr. Jeetubhai. If someone remembers this blog link, please forward to me

Hi Venu,

You can find that article here

Hope this is what you are looking for.

Rgds


Rajesh

 

[madvenu]

Hi Venu,

You can find that article here

Hope this is what you are looking for.

Rgds


Rajesh

Yes.. it's the same one. I believe tcpip is Mr. Tarun !

Anyway, I am still waiting for the drivers to arrive. They had to ship from Mumbai via Road as the air cargo guys are refusing to carry anything remotely suspicious like speakers because of the Obama visit !

And the drivers from Chennai / Ritchie street dealer - well, Mr. Motilal has not yet shipped them ... he seems to be busy and postponed my shipment a couple of times inspite of payment a couple of days ago..

I will wait for a day and if still not done, would request one of the Chennai members to help collect from him...

I am, in the interim, re-reading tcpip's articles on cross over design Interesting.

Does anybody in Bangalore have a measurement Mic etc setup ? I have built a pair of bookshelves which I would like to measure and then build a cross over for. At the moment, I am surviving with a single 3.3microF cap in series with the Dainty Metal Dome tweeter ( Rs. 175 from SP Road / Pooja Electronics )


Cheers
venu

 

[madvenu]

My first real introduction to hi-fi was through Tarun ji and that too by just exchanging emails.
I had many wrong notions about hifi and he cleared many of them
Never met him or heard his speakers but would really love to. Infact he is a member of hifivision but sadly is not active at all

Yes Rikhav

Tarunji ( tcpip ) has through his blog helped many of us too ! He seems to be around online less frequently though. But it does not matter... I am sure his work is carried forward by others. As we see, his work is still very relevant today - after 6 years !

Cheers
venu

 

[suri]

I am sure his work is carried forward by others. As we see, his work is still very relevant today - after 6 years !

No-

that work was an amateur stab at the work that experts (with passion) do-

that work is not at all relevant today- and there is not anybody carrying forward this (past-time)

more relevant is the work done by -

Zaph|Audio

 

[ssf]

more relevant is the work done by -

Zaph|Audio

Evaluation Myths Busted

Enjoyed going through the article. Thanks.

Regards,

Sunil

 

[madvenu]

Hello Suri

No-

that work was an amateur stab at the work that experts (with passion) do-

that work is not at all relevant today- and there is not anybody carrying forward this (past-time)

more relevant is the work done by -

Zaph|Audio

tcpip's work may be an amateurs stab - yes, and this is precisely why it helped me ! I am an amateurs amateur ( what ever that means !! ).

I was quite impressed with the humble story of another amateur's search for better DIY speakers in 2004. And I was much encouraged to see that tcpip spent a lot of time reading, discussing with the community of other DIYers around the world, and made many mistakes, got frustrated, became lazy sometimes etc in his DIY journey to build the speakers....

It is precisely this 'human frailty' of his search and work that impressed me to take up my own DIY search. I realized, how I could take this up - even if I am lazy - because, there is help and hope !

Zaph -- is excellent and a great gentleman. Following your link, I intend to study his methods and try them ( if I ever become as competent or even understand him !! )

Cheers
venu

PS: You are an inspiration too... seeing the number of speakers you have built

 

[Adhiraj]

Zaph is good yes but Troels is the LORD

DIY Loudspeaker Projects Troels Gravesen

 

[Hari Iyer]

Hi,

4" kevlar cones usually have a mid-range response going till 7KHz before the 1st evident roll-off occurs. Use this to your benefit by using a cross-over around 3KHz (1st Order) as you will still have one more octave response left with the woofer. Using a cross-over above 3KHz will cause the tweeter to suffer from ringing effect and cone break-up at higher volume levels. Kevlar cones have good mid-range response hence do not use any cross-over between 300Hz to 3KHz range. Also the woofer and tweeter resonse will have to be tamed as the enclousre size is very small and you have used a vented design. I thnk a 1st order cross-over with a bit of time-alignment on the baffle will give that trainsent impact you require. Once built this will be an ideal speaker to connect to LCD / Plasma TV. Do let us know once completed.

Regards, Hari.