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Old 14th August 2011, 20:36   #1
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Default Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosures.

This is the story of an experiment gone right!

It all started when a fellow BHPian posted a pair of 4" Ultimate speakers for sale in the Classifieds section. I jumped in, PMed him, transferred money and received a pack-sealed, un-used lovely 4" ULTIMATE - T1s (Ultimate models packs a punch! but because of their understated looks they dont stand in the show biz unfortunately). Only then I realized I had no idea on what to do with the speakers!


Meeting the Carpenter:
Fast forward few months, one day, I happened to locate a carpenter in the next street and immediately an idea was born. Decided to check if the carpenter can build speaker enclosures. Spoke to him and he asked me to show me the design model. He had not worked on any speaker enclosure for a long time. Had my doubts about his workmanship quality. But decided to give a try.

Selecting an Enclosure design:
Rushed home, browsed my computer archives and found the speaker enclosure design PDFs from FOSTEX. Fostex is a japanese brand specializing in full-range drivers as well as mid-bass and tweeter drivers. They are one of the few manufacturers who put up speaker enclosure designs for free in their website. I had downloaded their whole bunch and archived it some 4 years ago. Now, having located them I skimmed through and found a matching double-bass reflex enclosure which seemed to be a perfect for the 4" Ultimate T-1s.

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Last I read, Fostex products are available from Coimbatore based AUDIRE technologies who specializes in their own portfolio of speakers and amps.

3D Design:
Kick started Google Sketchup and sketched a 3D design matching the dimensions of the enclosure in PDF. Instead of the 73mm hole for the speaker, I opted for a 100mm hole matching the T1s. I know, the sound character will change. But i am okay with that.

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Construction:
Met the carpenter again, explained the design (took a lot of time to convince him to start the work) and handed him the print-outs and the speakers. The construction took nearly a whole day (I was in the office, so no photos could be taken). As mentioned in the Fostex PDF, 15mm plywood was used. The carpenter did a okay job. He was not keen on doing such precision jobs. His interests lies only in easier, money-making jobs. So the construction was little crude, with not-so-precise position of the ports and some visible gaps inside the inner-port plank. Brought the boxes to home and this is how they looked.

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And this is how it looked with the Ultimate T1 driver.

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The Amplifier
Now the speakers are almost ready in draft fit. Next item to procure is an amplifier. With the least budget in hand, I cannot afford any high-end stereo amps. So I called my friend in Karur who assembles Audio amplifiers. After a brief explanation of my idea, he suggested to settle for a 50w+50w stereo amp which will be more than enough for my requirements. Then came the important question. MOSFET or STK ? We squared on MOSFET based design. He informed me that there is a temporary shortage of MOSFET supply in his town and asked me if I can get the mosfets from Chennai. As I was busy with office works at that time, I decided to settle for STK which was available in his town. He agreed and sourced a STK 4192 II, a 50+50w IC. Soon things started building up, and the amp was ready in a compact body. He slotted an additional USB card reader (some chinese make) just for my convenience. Received the amp after a week of random testing.

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The Setup
As I spend most of my time with my computer - I connected the amp to my computer and set the speaker on the floor. Also painted them white (inspired by AudioEngine A2) and screwed the original round grill. It looked cool (atleast for me. heheh)

The Left Speaker
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The Right Speaker
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Top View
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Audition Demo
Please note : My Handycam's mic picked up the hi-frequency like anything. So the video clip's audio is dominated by hi-frequency waves. Assume a 30-40% drop for HF, in real world performance. Volume set at 2 points , Bass at 8 points, Treble at 7 points. (1-10 scale in potentiometers).

The audition starts at 1:43 in the clip below



Conclusion
For an average guy like me, who likes to watch movies and listen movie songs, instrumental music etc, this setup fullfills my requirement very much. I really like the tight bass-punch produced by the brilliant enclosure design from Fostex. I must admit that I have meddled with the box's original frequency tuning by using a 4" car speaker at 4 ohms, instead of the original 73mm fostex driver. So I was skeptical of the end-result. But fortunately, the end result was a pleasant surprise. This piece rocks! I love it.

Movies : Rocks! I do not need a subwoofer now. The double bass reflex ports are good enough to bring out the low frequencies better. The bullet sounds, dialogues, warmth are there and felt good.

Movie Songs : Good to hear. Depending on the MP3 bit rate, and CD Mastering quality, the quality differs. CDs bring the best out of these speakers.

Audio Tracks : MP3 Instrumentals like Yanni, Kenny G sound good and pleasant. I do not have any CDs from that genre. So cannot comment on the CD playback.

The placement of speakers (on floor, below ear level) which is not right now. So I am planning for stands.

I assume when a 8 ohms speaker is connected, the amp's volume has to be crancked up more to get the proper effect.

Lesson learned : Stay along with the carpenter to make sure he adheres to the specs. Else he will skip some important things. Also purchase good quality plywoods and make sure the final construction is free from gaps.

PS : I was unable to procure sound damping material at the time when the speakers were built. Nor had any idea about their availability near my place (Velachery). So the speaker was built without sound dampeners. The result was - standing waves. Later, I pasted the inner walls (behind the driver) with off-the-shelf 1" foam sheets temporarily. There is a big difference with less standing waves and tight bass. Yet this is not the optimum setup. I may replace with proper sound dampeners, or go for a new construction matching the 4" drivers later. Hehe.

Cost : Total Rs.5000
Drivers - Rs.500 + Rs.200 (S&H)
Speaker boxes - Rs.1600 (material + labor)
Amplifier - Rs.2700

Last edited by rajeshsundaram : 15th September 2011 at 09:44.
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Old 16th September 2011, 17:06   #2
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Default Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

Thread moved from the Assembly Line to the Gadgets Section. Thanks for sharing!
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Old 16th September 2011, 18:37   #3
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Thumbs up Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

Quote:
Originally Posted by rajeshsundaram View Post
This is the story of an experiment gone right!...
Congrats on a job well done, rajeshsundaram

Wonderful details and pics! Hobby electronics is something that has interested me from long back, though I never got around to doing much. The STK-4192-II is a very good stereo amplifier IC. My favourite Indian brand of hi-fi components, Sonodyne, had the STK-4191-II in their SA-580 amplifiers, which were part of the Uranus-II system.

Last edited by Blue Thunder : 16th September 2011 at 18:41.
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Old 17th September 2011, 12:01   #4
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Default Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

Quote:
Originally Posted by rajeshsundaram View Post
This is the story of an experiment gone right!

Cost : Total Rs.5000
Drivers - Rs.500 + Rs.200 (S&H)
Speaker boxes - Rs.1600 (material + labor)
Amplifier - Rs.2700


Superb! This is just simply superb! I thought DIY died in the 80s (Video killed the Radio Star) it is fantastic that guys like you are keeping it alive. You are now offcially infected with the DIY bug.

For your next project (there will be a next, wont there) I would suggest considering a power amp using the LM1875 or 3886 (depending on the power you need). For the preamp an opamp like the OP275 are NE5532 are nice cheap options.

For the speakers I would mate a small 2" cone tweeter (there are so many available on Lamington Road in Mumbai) to a larger 6" or so woofer at say 300hz/6db. This will mean a rather simple crossover. If you pad the 2" driver a bit the 6" woofer can be designed to compensate for baffle step.

BTW there are forums tailored for diyers like you.

Again, I think what you did is just so fantastic. Enjoy the process.
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Old 17th September 2011, 21:11   #5
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Default Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

Quote:
Originally Posted by navin View Post


Superb! This is just simply superb! I thought DIY died in the 80s (Video killed the Radio Star) it is fantastic that guys like you are keeping it alive. You are now offcially infected with the DIY bug.

For your next project (there will be a next, wont there) I would suggest considering a power amp using the LM1875 or 3886 (depending on the power you need). For the preamp an opamp like the OP275 are NE5532 are nice cheap options.

For the speakers I would mate a small 2" cone tweeter (there are so many available on Lamington Road in Mumbai) to a larger 6" or so woofer at say 300hz/6db. This will mean a rather simple crossover. If you pad the 2" driver a bit the 6" woofer can be designed to compensate for baffle step.

BTW there are forums tailored for diyers like you.

Again, I think what you did is just so fantastic. Enjoy the process.
Can 2" Tweeters go that low or are we talking about Mid (0r 3000 Hz/6db). I know Navin-ji cant be wrong (know about you from Diyaudio), apologies if I am wrong here.

@ rajeshsundaram, can we order these Fostex from their Coimbatore dealers (online/mail order). I almost stopped DIY Audio because of lack of good drivers in India (for a decent budget) but your post has given me some hope.
One more suggestion, next time you build the box, use MDF/Chip wood which would be much better than Plywood.

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Old 18th September 2011, 02:04   #6
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Default Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

1. I am often wrong. I should not have used the word "tweeter". They are labelled tweeters but are in reality wide range drivers. They look similar to the Tangband W2-800 and can be played to about 300Hz/4W or so (somewhere in all the paper that is in my office is a 4W tube amp design just perfect to drive this). I think maybe JBL's Pheonix and Odyssey drivers are also designed in the same vein (edge suspension and voice coil etc..).

2. There are other 3" fullranges like what Gallo use in their Nucleus. Over on diyaudio Dave (Planet10) has been extoling the virtues of the latest incarnation of the Fostex ff85. This driver is more expensive than the drivers you have used but is not stratospheric in cost (about $40 each) and would be THE Fostex to get (look at Fonken box plans as well) if you are ordering Fostex. Another option is a 70mm driver from Wavecor. Due to a set on "circumstances" I have a pair of each (Gallo and Wavecor) on my desk. I stuck them into a simple ABS box I picked up from RS components and with a little LF filtering and a 1875 the sound the made was pleasantly surprising.

The bad news.....due a 600% increase in NdFeB prices in the last year (2000% over 2 years) both these drivers (Wavecor and Gallo) are now really expensive compared to their original prices.

The story I have is that China arbitrarily increased prices on Nd magnets to get back at Jap auto makers (wiper motors and other stuff) and the loudspeaker manufacturers got caught up in this.

If you feel the need to drop me a line, feel free to do. Since you know me from another forum. Before the internet forums became all the rage (email existed) and the internet connectivity took off (I can't call what we have in India as true broadband) this sort of news was confined to those who could subcribe to "Newsletters". Here is a sample from an archive http://www.diysubwoofers.org/digests/v2/v02n280.txt

If you are a regular over on diyaudio you will recognise many of the names in these digests as well!

Last edited by navin : 18th September 2011 at 02:19.
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Old 18th September 2011, 02:27   #7
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Default Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

Wow nice work, must have been super fun
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Old 18th September 2011, 09:56   #8
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Default Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

@blue thunder
Thanks Blue Thunder. On a distant note, I can say Sonodyne was one of the reasons I ended up DIY. Long back, I was interested in doing my first project (for my car) based on neodymium drivers. At that time Sonodyne was one of the few importers of such drivers in Chennai. But they did not agree to sell me a pair of drivers. And when I visited their shop at Seeyali Amman koil st, the response was not that good. Had their response was good, I may have ended up buying their amps and speakers. Then I shelved the idea totally.

@navin
Thanks Navin. I had an friend who specialized in stereo amps, in my native town.He is the one who inspired me with DIY amps and speakers. Add to that, we have a 60+ year old amateur electronics uncle, who designed his own pre-amps and stuffs and was doing CD-Audio tape recordings. These two people were my inspiration. Yes there will be a next project sometime later. I will going for a proper setup with 6" drivers, good X-over and a good tweeter. Increased budget too. I read long ago that Berillium (brazil) manufactures one of the best hf-bullet-driver. Not sure if I can get hold of that in Chennai. I will see about that later.

@venki
I do not know if Audire is selling fostex drivers alone. May be a direct ping could reveal that. Yes, I am going for MDF for the next project.

@bottle
Thanks Bottle. It was much fun for me. Wifey is not that happy though. Complains about me spending too much time with my computer. LOL!

Last edited by rajeshsundaram : 18th September 2011 at 10:03.
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Old 18th September 2011, 10:27   #9
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Default Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

rajeshsundaram-amazing job dude,i always wanted to make a diy home theater setup, but never had the guts or the technical knowledge regarding this , so never took the risk. now i do have a yamaha thx amp with wharfedale speakers in the front, klipsch as center,yamaha subwoofer,bose 301 as surround and bose 201 as back surround.other than the tv[hitachi 42 plasma],yamaha amp and sub woofer the rest is all second hand and bought at a budget. my question to navin or any audio gurus is, would a really good diy speaker and amplifier set up be better than branded setup for eg. like the one i have?
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Old 18th September 2011, 15:34   #10
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Default Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

Rajesh, Nice DIY. Kudos to you in venturing to build the audio rig yourself. I always wanted to do this and your success would be an inspiration. did you assemble the AMP yourself? More specifically the AMP board. Does it come as a kit? I am planning to procure the components in Bangalore. I have searched on other forums, but the more I read the more confused I get :(

Also, heard a lot of Fostex and would love to get hold of them.

Thanks,
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Old 18th September 2011, 17:37   #11
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Default Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

Quote:
Originally Posted by bejoy View Post
Rajesh, Nice DIY. Kudos to you in venturing to build the audio rig yourself. I always wanted to do this and your success would be an inspiration. did you assemble the AMP yourself? More specifically the AMP board. Does it come as a kit? I am planning to procure the components in Bangalore. I have searched on other forums, but the more I read the more confused I get :(

Also, heard a lot of Fostex and would love to get hold of them.

Thanks,
Bejoy
@Bejoy

No I did not do the amp assembly. I left the job to my friend who is an electronics guy. I think he used a kit board and IC.I did not use any Fostex drivers, just used the fostex recommended enclosure design.

This is the contact details found in Audire website. Try them to check if they sell the drivers alone.

Contact nos:
00919003355444
00919003344644
00919894722600
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Old 18th September 2011, 17:48   #12
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Default Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

Nice work, Rajesh. Couldn't you get any of these stuff from Ritchie Street ? especially the mosfets.
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Old 18th September 2011, 21:07   #13
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Smile Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

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Originally Posted by esteem_lover View Post
Nice work, Rajesh. Couldn't you get any of these stuff from Ritchie Street ? especially the mosfets.
Thanks Esteem Lover. I wish I had the time to visit Ritchie st. :-) That whole fortnight was total hectic. Office-home-office-home.. no other go. My next project is definitely MOSFET based.

Quote:
Originally Posted by navin View Post
They are labelled tweeters but are in reality wide range drivers.
\
Oh my bad. It is not Berillium, it is SELENIUM of Brazil. Looks like Parts Express has a good range of selenium drivers. Will check later.

Last edited by rajeshsundaram : 18th September 2011 at 21:20.
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Old 19th September 2011, 01:20   #14
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Default Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

Thanks for sharing! and hats off to you for the effort.

PS: instead of a paint use cloth specially made for speaker box. It will make your speakers look professional.
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Old 19th September 2011, 13:32   #15
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Default Re: Assembled Home Audio Rig with 50w+50w STK AMP, Fostex Double Bass Reflex Enclosur

Quote:
Originally Posted by desigNation View Post
rajeshsundaram-amazing job dude,i always wanted to make a diy home theater setup
This is a stereo setup. a HT set up is more complicated to DIY as it involved DSPs, Delay tools and video switching.

Quote:
Originally Posted by rajeshsundaram View Post
Oh my bad. It is not Berillium, it is SELENIUM of Brazil. Looks like Parts Express has a good range of selenium drivers. Will check later.
Selenium makes Pro and PA drivers. I know them a bit. I would request you to listen to them before plonking down the money. Pro and PA drivers are deisgned and built for a very different application that home audio. Not they cannot be used, but for example you might find the Vas to the larger that what you are used to or the Fs to be hgiher than normal and the Cms numbers to high etc..

However there are many manufacturers of Pro/PA drivers that do recommend their drivers for home audio: take Beyma, BMS, 18sound, Ciare, Eminence, etc.. for example.

Many moons ago I build a small (48" tall, 10" wide and 16" deep) 3 way using a 8" Eminence woofer mated to a 6" TC series Vifa woofer and tweeter (it was a biamped cabinet with the 6" and 1" using a series XO). I had never done a series XO before and I wanted to learn their advantages and disadvatages.

For me any new project has to be different from anything I have done before, in looks, sound or application. I do discuss (sanity check) my ideas with a few audio gurus (two of which - Sam Kapasi and Bass and Trouble - are members of TBHP) but never get any encouragement. Their typical response is "Why?"
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