Indian equivalents of the following DIY items.

[ssSai]

Hello everybody,

Both fabmart.com and firstsecond.com do not list the book in their catalog. Any ideas as to how I can get my hand on one.


Navin BHAI, I did understand what you meant but I really do not know what drivers to buy for the stereo system.

>>> Do I settle in for two 8" woofers and a tweeter in a MTM configuration.
>>> Do I decide upon two 5" or 7" mids and a tweeter.
>>> How about a 8" woofer, a 5" mid and a tweeter.

ANY SUGGESTIONS ON THE 5", 7", 8", AND THE TWEETER DRIVERS.

NOBODY is an expert in every thing right? Other wise there would be no MadiSound or AdireAudio........

If this is the case then all you DIYers are good at one and OK at the rest. So if you are good at the art of making a good cabinet, you look up to others for the crossover and amps.

I am a starter and I wonder how come every body are just avoiding the subject of Amplifiers. Do I assume that every one build their own amps (if that is the case "hats off to you"). I searched a LOT (I really mean LOT) and no one even has any idea of any amplifier of more than 60 watts RMS (forget the amps the car accessories people stock... half of them are crap and the rest should be costly crap).

Hence I once more request you guys........any idea on the drivers for the stereo setup and what about an amp for the sub and another for a stereo setup (head room for a home theater would be fine).

[ajju]

5" vs 8".

This is what i gather..Please feel free to correct me if i'm wrong..

1) As the size of the cone increases the chances of cone break up in frequency of interest are high. These have the effect of causing unecessary dips in the response. The no of modes of breakup within the frequency of interest also increase as the fundamentals go to the lower frequencies. Cone breakup in addition distorts the radiation pattern and causes huge lobbing effects at the specific frequencies.

2) Above manifests itself as huge irregularity in frequency response towards the higher frequencies. thus for a two way system u would require a 8" speaker with a well damped cone if a smooth response is to be obtained over the crossover points. Moreover the choice of crossover point becomes critical. also one might require a tweeter with a good midfrequency extension.

3) For a good point source representation it is best if the two units are concentric and time alligned. This is hard to achieve with off the shelf independent units. Conventionally we place the tweeter somewhere on the periphery of the larger woofer. At the crossover point, the woofer primarily radiates from the centre of the cone and hence the system can be treated as two point sources seperated by a distance equal to the distance between the centre of the speakers, the least here being the radius of larger speaker + radius of smaller speaker. This interaction also causes lobing effects on the final radiation pattern. And on either extremes of the usable range of a speaker the phase response is extremely unpredictable. Thus it becomes difficult to judge the interaction of seperation of the units and crossover frequency if we are using drivers which are crossed over at the boundaries of their usable range. If u select smaller dia woofers the high frequency extension will be better and hence mating it with a tweeter becomes a breeze. Also u can choose the crossover point such that there is still some overlap of the usable frequency range of the units which falls in their respective stopbands. Thus the speakers are never required to operate at the dirty extremes of their response curve.

4) Edge diffraction effects from the discontinuities on the front of the baffle. This can be tamed to an extent by shaping the edges of the baffle and using compensatory circuit. The idea behind having a narrower baffle board for the speaker mounts is to push the fundamental inteference frequency(which again causes lobing) to as high a range as possible so that the no: of harmonics falling in the audible frequency range are less and also the density of occurance is less.

All the above effects are extremely difficult to measure and control. But i feel the coloration due to these effects can be considerably less if woofers of smaller diameters are used and might have a positive effect in reducing them. The imaging(mainly attributed to the radiation pattern of a speaker) improves as the lobing effects in the response reduce.


ajju

[Pixo]

Hello everyone

Sai,
If you are thinking of making an amplifier yourself, here are some

Crescendo : I don't know much about this amplifier, but the schematics and the PCB pattern are already available. So you can save the time starting from scratch.

The Leach Amp : Professor Leach has a detailed description of this amplifier and the PCB pattern is availabe for this one too at his site.

Rod Elliot's P3A : check out the projects section of his site. It's titled Project 3A and hence the name. It should be capable of 100 Watts into 8 ohms.


I have a question for you guys :

I came across two Pioneer drivers - a 10" rated for 300W and a 12" rated for 650W (1000W peak!?) originally meant for car audio. I wondered if those would make a good choice for a subwoofer. What do you guys think?

[navin]

Originally posted by ssSai
Navin BHAI, I did understand what you meant but I really do not know what drivers to buy for the stereo system.

I am a starter and I wonder how come every body are just avoiding the subject of Amplifiers.

i built my own stereo pre and power amps but use a MArantz SR7000 for my AV setup. in fact my power amp is my own design based on teh B&K ST140 but using 3 pairs of output resistors instead of teh 2 they use. also using slightly different basing and a 1200VA tranny and 60,000uf of caps i get close to 200W at 8 ohms. the preamp uses relay switching and a OP275 for control.

Originally posted by ajju
5" vs 8".

1) As the size of the cone increases the chances of cone break up

2) Above manifests itself as huge irregularity in frequency response towards the higher frequencies.

3) For a good point source representation it is best if the two units are concentric and time alligned.

4) Edge diffraction effects from the discontinuities on the front of the baffle.

All the above effects are extremely difficult to measure and control.
ajju

materials are often as important as size as far as cone break up is concerned. sometime cone break up can start as low as 1000Hz. Edge diffraction is not the same as Baffe step. baffle step can be comepnsated more easily than edge.

almost all of the above is diffcult to control but more so for different listening rooms that is why i always say that the biggest advatage DIY has that they can compensate for the room.

[tcpip]

Originally posted by ssSai
Both fabmart.com and firstsecond.com do not list the book in their catalog. Any ideas as to how I can get my hand on one.

Order from Amazon or Barnes and Noble, pay over the Net by int'l credit card, and either ship to a friend's address in the US and ask him to get it with him when he visits India, or get the book shipped direct by courier to your Indian address. No book is difficult to get sitting here in India if it's available with these outlets and you are willing to pay courier charges. In addition, almost all large bookstores in big Indian cities are willing to procure any book in print, if you can give them details (ISBN number, publisher name, etc). I know Strand in Bombay is willing to do this. They will typically charge list price plus 15% for shipping and overheads, and take 6-8 weeks of time. (Amazon often sells the books much cheaper, but if you add courier to India, it may turn out more expensive.)

I am a starter and I wonder how come every body are just avoiding the subject of Amplifiers.

I wouldn't exactly say this Website is avoiding discussing amplifiers, considering that there are forums for valve amps, solid state amps, and the highly specialised chip amps on diyaudio.com. We just don't like to mix up amps and speakers in the same forum.

no one even has any idea of any amplifier of more than 60 watts RMS

I don't think DIY chaps on the amps forums here will agree that they're stuck with 60WRMS. Have you checked these forums?

You've already received excellent suggestions from Pixo. In addition, I'll add the books by Randy Slone and Douglas Self, which have PCB designs, in case you are willing to get them fabricated and start from there. (Randy also used to sell ready-made PCBs; you can send him email after you buy his books.) He starts with ultra-low distortion Class A 40W and Class AB 80W designs (0.0009% THD in Class B!), and goes up to 400W-RMS/ch designs using lovely L-MOSFET output devices. And his books are a total treat to read. I've seen umpteen circuit articles in Elektor and never understood any of them till I read Randy's books.

If you are open to investing, say, USD 500 for a monoblock amp kit, you can go for the AKSA amp kit. People claim it's absolutely top-class. There's one Singapore Website which seems to sell PCBs and full kits for high-quality amps; its designer is a member of diyaudio. And then there's the Pass forum on this Website which discusses Nelson Pass' amp designs. Those designs have a very loyal fan following and Nelson himself participates in "his" forum. If you want to build valve amps and can procure all the valves needed, I am sure the valve forum can point you to at least a dozen good sources of designs and kits. Check the Bottlehead site as one example.

Incidentally, the Crescendo, being an Elektor design, will have its PCB available for INR payment from the Indian publishers of Elektor. Contact them. You may have to hunt a bit for the devices it uses, though. And by all accounts, those who have built it say it's an excellent amp. If I had to build something that complex, I'd probably opt for the Leach amp or one of the Randy Slone designs. Just personal preference.

Tarun

[navin]

since amps are the topic of the day i should mention i have NOT had good exp. with the BUF devices in many of elektor desiigns.

[ssSai]

Hello every body.

You people got me wrong, I did not mean what Tarun thinks. Let me explain.........

NOBODY is an expert in every thing right? Other wise there would be no MadiSound or AdireAudio........
If this is the case then all you DIYers are good at one and OK at the rest. So if you are good at the art of making a good cabinet, you look up to others for the crossover and amps.


The above is my case. I have not yet got the sealed enclosure stisfactorily into my system (brain) on the first hand and this is my first project. I therefore decided that building an amp is not my cup of tea. Hence I looked up to you people for some advice....


I am a starter and I wonder how come every body are just avoiding the subject of Amplifiers. Do I assume that every one build their own amps (if that is the case "hats off to you")

This goes to Navin BHAI and every one in the DIY amp club.



I searched a LOT (I really mean LOT) and no one even has any idea of any amplifier of more than 60 watts RMS (forget the amps the car accessories people stock... half of them are crap and the rest should be costly crap).

Given my take on the amp part of the DIY project, I went hunting for an "Off the shelf amp". I visited many places where I thought I could find an amp. My logic was, "If I can get a AVA250 amp for 178 USD, I should surely get a 250 watt amp here in Bangalore for atleast a 190 USD." But even after a LOT of hunting I found no one with an idea of a Home Theater amp of more than 30 watts per channel (forget a dedicated subwoofer amp). One thing I observed was that every one (at the shops) were showing me car ams when ever I ask a 250 watt amp.

The only place I got to see a 300 watt RMS (2 Channels) was at "ProFx" which is in Barton Center, M.G. Road, and the price was a whopping 28,000 (INR).


I hope I have not annoyed anyone.

Now since I have got my question right (Justified :-)), any one want to guide this fellow??

[ajju]

Sai,
If u r looking for ready made amps ..y dont u consider local makers like Pulze or DNM pace etc..though i dont have any experiences with them... else if u want to try out urselves u get a large number of kits...basically buy the ready made PCB's (and u can redesign/tweak the basic circuit which is a rare case) or get better quality parts and assemble them. I'm sure they wont dissapoint u..! Otherwise u can use some IC's ...the STK series would be a good choice...they come in the same shape but various power ratings...may be u can bridge them...there are numerous options... Also i remember seeing a sub amp module(if we are talking about that) at the DNM stall at AV-expo bangalore...u can contact them for details. They sure will respond..may be a lil delayed though...BTW did u recieve ur shipment of woofers..?

[ajju]

Ajju, do you know where Olson's book is available?

Ashwin...
There are a lot of them by Olson.
If its "Fundamentals of Acoustics by HF Olson" that ur referring to the copy i saw was a special reprint from a microfilm...and it was a pretty fat book with all kinds of data...very mathematical..covering all kinds of topics from normal baffles to various kinds of horns..noise control and all..but i remember seeing that it was out of print and only microfilm reprints are available ...i dont have that book now...i found it at the reference section of a research organisation's technical library...!

ajju

[ashwin]

Originally posted by ajju

i found it at the reference section of a research organisation's technical library...!

ajju [/B]

So that puts it out of my reach

- Ashwin