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.
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.
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.
And this is how it looked with the Ultimate T1 driver.
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.
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
The Right Speaker
Top View
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