3way Design


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	Name: Mains 3-way ported (custom) Construction: 8/21/99-9/4/99 Sensitivity dB @ 1m/2.83V 90dB Impedance (ohms) 7-8,dips to 5 Bass Driver 12" Swan305 4" diameter flared port - 11" long (tuned to 30hz) Midrange Driver 5" Seas MP14RCY w/ 1.7L chamber High Frequency Driver 1" silk dome Vifa D27TG-35 Chambered Power Rating 10 -100 watts Dimensions HxWxD 42 x 13 x 16" 5degree sloped front and top 2.56cuft true volume Frequency Response 30hz - 20kHz Cost $550/pair

Introduction and Criteria: This project started as a driver replacement for an old set of 3way speakers. After the realization I would need to modify the cabinet design to accept any new drivers I decided to build an entirely new set of speakers from scratch. The new speakers would be my primary listening speakers and the mains in a home theater setup. They needed to be full range 3-way design with respectable bass output to 30hz. Driver components needed to be cheap, especially the woofer to keep the cost down, crossover components needed to be in the $50-70$ range using metalized polypropylene caps which is 'middle of the road'. The cabinets needed to have a small footprint and look stylish. Total cost needed to be under $750.

	Cabinet design: I originally had plans to build a truncated pyramid cabinet. Construction would have proved to be difficult and the aesthetics questionable. I definitely did not want to build a rectangular box though. After looking at various commercial designs I choose to model these after the beautiful Sonus Faber Grand Piano's but at a much larger scale. This design includes a sloped front and top which eliminates parallel walls except for the sides. I originally wanted to cover the cabinet with gloss black Formica. The cost and durability of gloss black was prohibitive however. A flat black Formica would be used instead. I usually despise ported design speaker since most commercial models have a bloated low end response. After a quick glance at available drivers in the 10-12" range that cost under $100 I soon realized I would need to port the enclosure. AutoCAD drawings are available here.

Driver Selection: Since cost was a primary concern my driver choices narrowed down pretty quickly. My choices were as follows Tweeter: Vifa D27TG-35 (click to see data sheet) $23.70 The D27TG series fabric dome tweeters feature ruler flat pass band response combined with textbook-perfect LF roll off. All under $25. The D27TG-35-06 and D27TG-45-06 feature a lower 650 Hz resonance, which makes crossover design less critical. This is the same tweeter used in the Dunlavy Signature VI ($25,000/pair). The Seas TFFC tweeter was high on my list as well but out of stock at Madisound. Many DIY builders have been recommending this tweeter lately. Update: I've heard rumors the current D27tg tweeter has a higher Fs than the ones I used. This shouldn't effect performance since it is crossed so high. Midrange: MP14RCY/P (H 422) 5" PP cone midrange. $38.60 This unit features exceptionally flat response. It's also notable for a low Fs value (compared to other 5" drivers) of 43 Hz, but the Q is so low that it's really unusable as a mid/bass driver. Comparable versions of these drivers are used in Vienna Acoustics Haydn ($895/pair), Vienna Acoustics Mozart ($2,500/pair), Vienna Acoustics Beethoven (4,500/pair). The Vifa P13WH was also high on my list, This is a 5" (13 cm.) PP cone mid/bass. This driver is used in the popular Ariel and many other highly regarded DIY projects. Its ruler- flat passband response and well-controlled roll off have led many DIY'ers to declare this to be the finest midrange driver in existence. It is used in the Dunlavy Signature VI ($25,000), Halladay Acoustics Hallavox SE ($1750/pair) Woofer: Swan 305 $58 I didnt have many options in this category due to prices. After modeling the various drivers in WinISD it was clear the Swan 305 would meet my objectives. The Swan 305 was originally designed for a DIY project in a 1988 issue of Speaker Builder. Unfortunately, the vendor went out of business and they were unavailable for a while. An identical unit was reverse engineered and is now available from Madisound and Meniscus. Suitable for either sealed or vented systems, the 12" Swan 305 is priced under $60 and features exceptionally flat FR and really good numbers. The only caveat is that it uses a foam surround which tends to deteriorate over time. The Madisound 1252DVC was also on my list but the low power handling scared me away. Port: PNR Aeroport $19.95 PNR Aeroport's patented flared ends eliminate turbulence and maximize air flow, thus greatly reducing distortion and wind noise in any ported enclosure. This results in a more accurate bass response with an average increase in SPL of 3 dB Simulation and Design:

	Modeling the Swan305 in WinISD for bass response. This determined box volume, port length and tuning frequency. WinISD is pretty powerful for this since you can adjust the parameters by dragging the mouse and see the results real-time.

To simplify crossover design I took advantage of Madisound's LEAP crossover design service. Below are the charts prepared by the computer modeling program. The crossover was built using this information. Box volume was based on 2.1cuft at the time of their design but I changed it to 2.5 cu. ft. after more analysis on my end. Low frequency information is not entirely accurate on the below charts. With the increased enclosure size to 70L the slight rise on the low end goes away and adds more extension.
Crossover Design	Crossover Response Impedance	On Axis Response

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					3way Design (DIY)