The Design: Upon the client's request, the enclosure was engineered around the principles inherent in my original "HellBoy" design, but with emphasis on the fact that it would fire into the trunk and not directly into the cabin. Space constraints presented another issue, however, one that could be overcome.
The Build: This build was another in a series of firsts; in case, the first screwless enclosure to feature wood bending. As this alignment will yield substantially high vent velocity, a 6" radius outer flare was implemented to keep down the audible turbulence:
The best way to keep a flush mount inset in perfect alignment with the woofer cut-out is to trace it with a rabbeting bit. Here you see a pair of standard mounting holes cut into the double-stack:
Once the enclosure is fully assembled, the mounting cut-outs are traced with a 0.75" rabbeting bit in multiple passes. Afterward, they are beveled out with a 0.25" radius round-over bit (as are the short outer edges of the enclosure.) The long outer edges are beveled with a 1" round-over bit:
In the end, we wind up with a sturdy build with no sharp edges for the carped to snag on as the enclosure is taken in and out of the vehicle:
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( 4 / 15 )The Goal: The object here was to sustain an even low frequency extension throughout a medium size room. In addition to all-around powerful bass, this enclosure needed to be suitable for music and movies alike.
The Design: After reviewing the client's room layout and the proposed subwoofer position, I arrived at a corner-loading bass-reflex design. In addition to the single 10" woofer, the enclosure would also have to house a plate amp, which I incorporated into the compression chamber.
The Build: This was already the second in the series of my screwless home audio builds. Here, you see a little bit of pressure applied to one of the panels:
As you can see, the design, itself, is quite rudimentary. I always tell my clients that complexity doesn't automatically translate to performance. I try to keep my designs as straight-forward as possible whenever I can and, luckily, achieving the desired results in the client's listening environment did not call for anything overly exotic:
The finished product was this single-axis bass-reflex with a plate amp cut-out centered along the side and a flush-mount inset for the woofer. The slot-loaded vent terminates at a 1.5" radius flare:
As a fun bonus, this enclosure was scheduled to ship around the time when Steve from Digital Designs was coming out for a visit. We postponed the shipping date so that both Steve and I could sign the enclosure.
From the right to the left, we have Steve Milton, his brother, and me. Oh, and the enclosure, of course.
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( 4.2 / 13 )The Goal: The client was looking to achieve "big sound" with a small sub inside of an '88 Honda Civic hatchback. In addition to out-performing the client's old enclosure, this new one was to remain musical and sustain a wide response range.
The Design: Even though the 8W7 bares a relatively low efficiency bandwidth product, the overall loading characteristics inside the cabin made it possible to horn-load this little woofer via a large throat chamber and a tight throat gap. The result was a rear-loading horn with a rather high cross-sectional expansion rate.
The Build: I decided to make this my first completely screwless car audio enclosure. Screws were used temporarily along the top and the bottom of the enclosure serving as vertical clamps while the vertical panels were clamped horizontally using a series of ratchet bars:
As you can see in the picture below, the horn's cross-section expands quite rapidly, going from 58cm^2 at the throat to 464cm^2 at the mouth--that's almost twice the woofer's effective piston area. The inner vertical edge of the mouth is beveled with a 1.5" round-over:
Once all the panels bonded, the screws were removed and the holes were filled with MDF paste. Since no counter-sinks were necessary, the holes could be kept very small and, once the MDF paste cured, it was sanded flush, leaving almost no trace:
A 0.375" radius round-over was used along all of the outside corners for a "soft" finish:
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( 4.2 / 13 )Introduction: This particular entry is especially significant as it documents a detailed walk-through of the very first set of home audio speakers to be built and ship from PWK Designs. On daily basis, I receive at least two or three calls from folks asking me about what it would take for them to see a PWK Designs speaker in their home theater or listening room. Well, here it is in-depth and illustrated:
Step One: As it is with any other project, it all begins with a call. This is where we discuss all the details of your listening preferences and all the conditions of your listening environment. At least six hours out of the day, I look like this:
In this instance, the client--Derrick--had already purchased a set of HT subwoofer blueprints from me and was now looking to upgrade the front stage to something of matching quality. Throughout our correspondence, we've established all the details such as his listening preferences, the dimensions of his listening room, location of the subwoofer, the speakers, and the listening position. With that, I was able to compile a parts list of the speaker and crossover components that, in conjunction with one of my designs, would best accommodate Derrick's listening objectives. Once everything had been established, I put together a price quote totaling the cost of the components, the enclosures, and shipping. The numbers looked good so, once the payment was made, I went ahead and purchased everything that I'd need to get started.
Step Two: Given the advantage of having hands-on access to all the speakers used in the project, I like to perform my own T/S parameter analysis. In my experience, the actual parameters will almost always differ from the ones published in the owner's manual and, in a critical listening application such as this, the slightest deviation can mean a world of difference.
Once a definitive set of T/S parameters is established for each speaker, the engineering process can commence. This is where I determine the optimal alignment to achieve the desired results at the listening position. Many factors such as room modes, nulls, and diffraction can make this process quite challenging. The general density of the walls, the floor, and the ceiling, in addition to the furniture layout can also play a significant role in how a speaker needs to radiate.
Step Three: Once I've finalized the alignment and drew up the blueprints, I move the operation over to the wood shop where I bring the model into existence. Derrick's design calls for extremely rigid bass ports so, while the sound resonates inside them, the ports themselves do not. A typical bass port used in a home audio speaker is either a cardboard tube or a PVC / ABS plastic mold, anywhere from an eight to a quarter of an inch thick; you can cause it to resonate simply by tapping it with a pencil... These are 1" thick, they weigh approximately six pounds a piece, and they're built with 13 pressure-bound stacks of MDF:
To an audiophile, there's no such thing as overkill. Besides being virtually impervious to adverse resonances, these ports are composed of the exact same material as the rest of the enclosure for a perfect tonal match. I allow each ring to bind under heavy pressure for approximately half an hour before tracing it and stacking another layer. This process can be quite time-consuming but the results are well worth the effort.
I set the ports aside for the time being and go to work on the outer frames of the two speaker enclosures. In prepping the wood for this project, I made it a point for every cut to come from the same sheet of MDF as an additional measure to further assure consistent wood density. The frames are subject to the same amount of pressure as the ports, and are left under a heating lamp for approximately half an hour on each side:
Finally, it's time to shape the face baffles. No mistakes can be made here since the bass ports are already bound into place. Along the face, the ports flare out to nearly three times their original cross-sectional area and, on the inside, they are suspended with a quarter-inch gap between the bottom and side walls. A 1" radius bevel is used to round over the exterior vertical edges of the enclosures (both front and back) as a way to reduce wave diffraction:
A quarter inch radius bevel is also ran along the top and bottom of each enclosure to help reduce horizontal diffraction. Once the towers are complete, they are moved out of the wood shop and into a dust-free environment (in this instance, my listening room) for final tuning and, eventually a paint job. It almost pains me to have to conceal all this woodwork behind several coats of Polyurethane.
Now it's time to test-fit the components. Obviously it's a little late to rectify any cut-out or inset errors at this point, but that's what practice cuts are for; these final ones are dead-on:
And here's another shot from an angle to better illustrate the flush mount:
Step Four: Initial impressions: Once I've wired up the cross-overs (2nd order 12db/octave 3Khz high-pass for the tweeters), it was time for the first listening session. Right up front, I noticed the clarity of the speakers' on-axis response. The horizontal axis seem to be a lot more forgiving than the vertical axis--hence the 19 deg. tilt:
This, of course won't be an issue in Derrick's listening room as the speakers will sit at a sufficient height for the gap between the woofer and the tweeter to be level with the listeners' ears. (For this listening session, the speakers are on-axis with my ears both vertically and horizontally.)
Overall, the speakers exhibit a very flat response down to ~50Hz and a very shallow roll-off for a surprisingly deep extension; at 30hz, they're still audible. This, of course, will change as the speakers are raised further off the ground and moved away from the walls. With the two speakers and the listening position forming a 40 deg. angle, and with a listening distance of approximately 6 feet, the sound stage is exceptionally deep with the individual instruments easily placed even beyond the room's physical boundaries.
Finally, the enclosures are primered, re-sanded, and several coats of polyurethane paint are applied for a glossy finish. The cross-overs are then permanently attached with large amounts of hot glue (to limit resonance) and all the components are tightly mounted onto the enclosures which are now ready for shipping:
Let me start by saying I will forever be a PWK Designs customer. I have always had a interest in home audio since I was a teen. Before thump in the ride was the thing, it was normally a house party that got it jumping off.
I'm more layed back now but I still had a need to get a real setup. I wanted to get something that I can call my own. I wanted to go the custom route. I search and search until I found PWK Designs. Unlike other forums and websites. This guy (Pete) seemed to have more positve feedback than many. I joined his forum and got into asking audio questions pertaining to home theater and car audio as well. No matter who messaged me. Everyone said, "Pete is a speaker designing genious". If you don't believe me, go to the forum and read the workblogs/testimonials.
So after seeing pics of his designs and work displayed on youtube I was sold. Upon getting a case number for the design and build, Pete wanted to know details about what I want in terms of tonality, genre of music, & dimensions of the area (livingroom) the system will be playing. First, was a suggestion of a pair of towers but due to some space restraints, I wanted to go with something smaller. At the same time, I'm looking for big home theater front stage sound. Thus came the idea of a pair of mini-towers. I wanted some speakers that could set on the top of stand (72"L x 22"W x 26"H) next to my Samsung DLP. Pete said, "it would be a challenge but I can pull it off". Little did I know that was an understatement.
I was confident enough in Pete to let him select the parts for this project. The list as goes as follows: (2) Alesis 6.5" shielded carbon fiber cone woofers, (2) Vifa D19TD-05 3/4" dome tweeters, (2) Crossovers 2-way 8ohm 3,000hz 100w, and (2) pairs of Dayton BPA-38G binding post. The source I currently have is the Pioneer Elite VSX-TX24 THX certified (90x5 watt) digital receiver.
Periodically Pete emailed me with updates of progress to show me the details and engineering going into my design. I was like a kid again all excited. When they were finished I eagerly counted down the days while they were in shipment on route to my home. When they arrived (after four days) I ripped into the box and began hooking them up to my receiver.
In my first listening session, I did nothing but play r&b. The Mary J Blidge was very smooth and detailed but somthing was lacking. The pioneer receiver was struggling to get the towers to live up to there potential. At first I thought I would be just fine with the pioneer elite despite Pete telling me to invest into a separate source. Man was I wrong. I was explaining to him how I had the bass/treblegain all the way up and I just knew the speakers wanted much more. The alesis were hardly flexing at all with the volume up high. So I called and talked to Pete about what amplifier would be best for my application.
He recommended the Dayton APA150 and after reading all the customer reviews on Parts Express I got me one. It took less than three days to arrive so here's the moment of truth. I connect the rca's from the separate amp output located on the back of the pioneer receiver to the input jacks on the dayton amp. Then I ran the speaker wire from the speaker to there respective terminals on the back of the dayton amp and powered it up. I played Mary J. Blidge again to get a real feeling of the before and after effect.
With the volume turned up a quarter, the sound was astounding. I was hypnotized. I'm talking completely hammered on how great the sound drastically improved. I've read and seen videos of audioholics that say, "when you hear music in its true form, you drift into another world." Well, I can vouch for that. I was listening to my new setup for about six hours non-stop. Just playing one cd after the next. Pete told me that when he tested the speakers himself the mini-towers had a 50hz curve response with a 30hz roll-off. After getting the amp I needed to bring these speakers to life, he was not kidding around. This is by far the best front stage I've ever owned. I'm not an expert but I have sat in many listening rooms and theater rooms. This guy makes speakers that should cost around $3k a pair. You know you are lost for words when all you can say is WOW!!!!!!!
Rich deep tones with authority and smooth crisp accurate highs will make you swear you are there in person. That is the best way I can describe the performance of these mini-towers.
Because of Pete, I've got bitten by the audio bug. I am already making arrangements to upgrade to a 5.1setup. All being designed and built by Pete. I've only had this new setup for a week. I love my new front stage.
Thanks Pete
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( 4.5 / 60 )The Goal: The client was interested in an SQL enclosure with some pressure-building potential for his 1998 Toyota Avalon using a pair of Eclipse SW6210 12" woofers.
The Design: Working within a relatively compact space given given the cone area, I decided on a somewhat constricting compound-loading bass-reflex alignment, still making use of the trunk cavity as a resonant chamber for an in-cabin response of 33Hz - 78Hz with excellent efficiency throughout.
The Build: With a cross-sectional area of 62.5in^2 along the compound section, an aerodynamic air path was in order. In this design, all four corners of the compound vent section are beveled to a 1" radius quarter turn:
This particular project is another one of my horizontally screwless builds; a big bonus anytime I implement deep round-overs to compensate the vent's peak velocity potential:
Then we add the corner slants and the compound section waveguide:
And, as a finishing touch, half inch round-over along the length of the enclosure so that it slides in and out of the trunk easier:
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( 3.3 / 19 )
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