For a passive dipole speaker system, the U and H frame geometries represent an interesting set of trade-offs against an OB configuration. However, in each case the recommendation is still to use a high Qtd woofer driver. Many of the lessons learned in the previous study of a passive two way OB speaker system also apply to passive U and H frame designs. The trade-off between OB and U or H frames is increased bass extension with a loss of SPL. This needs to be carefully balanced against the important requirement to mate with a suitable midrange or full range driver.
The maximum length of the U and H frame geometry should be sized so that the first quarter wavelength resonance occurs above the low pass crossover frequency. Lmaximum < c / (4 x fcrossover) If the length is set correctly, there is no need for fiber stuffing in the cavities used to form the U or H frame. Adding length will not increase low frequency efficiency, it will only produce peaks in the SPL response. Efficiency of a U or H frame can be adjusted up or down by increasing or decreasing the cross-sectional area of the cavities.
A few concepts not explored in this study are the impact of an unsymmetric H frame and tapered or expanding U or H frame geometries. Each of these options could be used to control or fine tune the bass system’s SPL frequency response. There is still a lot of interesting possibilities for U or H frame design which can be reviewed using the appropriate MathCad worksheet. The three cases shown in this document are the default configurations in the latest MathCad worksheets. If I decide to incorporate one of these dipole geometries in a future speaker system design, which is highly likely, I will be trading off many of these variables looking to maximize bass extension and SPL.
DIY-dipole-1A correctly designed and damped U- frame woofer potentially achieves 6dB greater on axis sensitivity than an H frame dipole woofer with the same bulk dimensions or foot print. The U-frame woofer does not have a dipole radiation pattern, but rather a cardioid* like pattern.
tangenAVdesign skrev:Jeg ville ikke valgt L26RO4Y framfor L26ROY, men det er nå så...
Førstnevnte har lavere følsomhet og mer ugunstige T/S parametre, og det trenger man ikke akkurat i en dipol synes jeg.
tangenAVdesign skrev:Flere spørsmål på en gang her...
4-lags versjonen av L26 tåler IKKE mer effekt. Det er bare å se på databladene, de er oppgitt til samme effekt - 250W AES. Mer spoletråd gir ikke høyere belastbarhet i dette tilfellet.
Som sagt før tror jeg Linkwitz ville ha 4-lags versjon for å få mindre nivå oppover i frekvens, men jeg har ikke fått dette bekreftet med sikkerhet.
Linkwitz har hele tida med Orion og nå med LX512 benyttet små lang-slag basser. Ja selvsagt for å få mest mulig ut av en så liten høyttaler som mulig.
Lang Xmax er alltid en fordel i dipoler, jo lengre Xmax jo mindre forvrengning for et gitt SPL. Jeg har jo valgt lang Xmax på mine egne bass-systemer, +/- 15 mm er ganske barskt (Beyma 21SW1600nd).
Quote:"There is more to a woofer than its published TS small signal parameters and X-max, derived from mechanical measurements.
In the Orion's open baffle, a woofer operates in the large signal domain; and its distortion, dynamic stability and limiting behavior
determine the sound. An open baffle is the most demanding and difficult environment for a long throw woofer."
To meet these stringent demands, the L26RO4Y subwoofer builds upon the already excellent chassis, magnet system, cone,
and surround of our L26ROY. An all new FEA designed spider and 4 layer voice coil wound on a stiff glass fibre former have been employed, resulting in
a driver with ultra long throw, very low distortion, and extremely stable mechanical operation under all conditions; including open baffle systems.