James
Lord of the Erg\o/s
This has been a long time coming, but I'm often told it's better late than never. At least I've learnt a little bit more about loudspeaker design and hopefully better at it.
At the risk of repeating myself, I should outline what I consider to be the prime criteria for such a loudspeaker. First and foremost, it must be capable of playing music from all genres. This means it needs to have a reasonably wide bandwidth and dynamic range, and capable of generating convincing scale.
Secondly, it must be affordable. But those who know me know I don't do things in halves, so to temper my penchant for the expensive - I have looked long and hard at cost-effective drivers for the job and have come up with this selection of Danish-made Vifa drivers.
The M26WR-09-08 is a 10-inch woofer that has a paper-pulp cone and a very generous +/- 6.5mm of linear travel. More importantly, this driver is happy to be loaded in a sealed box of only 40L, which should make for a reasonably compact floor-standing design. This driver retails in USA for round $90 each.
The D75MX is a 3-inch dome midrange that will be expected to cover around 500Hz to 3kHz. Unfortunately, there isn't an affordable 10-inch bass driver that can cover mid-frequencies with any real conviction so this has to be a 3-way design. The choice of the D75MX is also a deliberate one because it has an acoustic centre depth that is very close to the matching tweeter so that a vertical baffle can be used without the need to incorporate time-delay to ensure correct crossover summation. This driver retails in USA for around $42.
Last but not least, the D27TG-35-06 is a ferro-fluid cooled tweeter with a usefully low resonance frequency of 650Hz (which means I can probably get away without the need for a resonance trap circuit) that will be used from around 3kHz. It will extend cleanly without break up to beyond 20kHz, which is fantastic performance for a $25 tweeter.
All up, the drivers cost around US$314, which compares more than favourably with the US$1,200 for the E-V drivers.
Thirdly, the PFM-Special must be easy to build. This means a rectangular box with straight edges (OK, maybe a bit of a rounding over) - but no fancy curves, radiused profile or tricky joinery. I'm planning to use 18mm MDF for the main carcass, which will then be clad with 18mm marine ply. Others may choose to use MDF for the outside as well. No need for expensive hardwoods.
Finally, the PFM-Special must be true to the flat-earth listener. It will use acoustic suspension loading principles to produce a tight and tuneful bass. The bass extension won't be as low as a 'Brik, but that should make it more sympathetic to boundary placement whilst not being entirely dependent on it. Will have to suck this one and see what results.
Other design criteria includes ease of drive with minimum impedence phase swings, and I'll endeavour to keep the impedence minima above 5-ohms.
Work on the cabinet will start in earnest when the E-V cabinet is completed. I intend to measure both designs at the same time so that I need to place only one order for XO components.
Stay tuned.
James
At the risk of repeating myself, I should outline what I consider to be the prime criteria for such a loudspeaker. First and foremost, it must be capable of playing music from all genres. This means it needs to have a reasonably wide bandwidth and dynamic range, and capable of generating convincing scale.
Secondly, it must be affordable. But those who know me know I don't do things in halves, so to temper my penchant for the expensive - I have looked long and hard at cost-effective drivers for the job and have come up with this selection of Danish-made Vifa drivers.
The M26WR-09-08 is a 10-inch woofer that has a paper-pulp cone and a very generous +/- 6.5mm of linear travel. More importantly, this driver is happy to be loaded in a sealed box of only 40L, which should make for a reasonably compact floor-standing design. This driver retails in USA for round $90 each.
The D75MX is a 3-inch dome midrange that will be expected to cover around 500Hz to 3kHz. Unfortunately, there isn't an affordable 10-inch bass driver that can cover mid-frequencies with any real conviction so this has to be a 3-way design. The choice of the D75MX is also a deliberate one because it has an acoustic centre depth that is very close to the matching tweeter so that a vertical baffle can be used without the need to incorporate time-delay to ensure correct crossover summation. This driver retails in USA for around $42.
Last but not least, the D27TG-35-06 is a ferro-fluid cooled tweeter with a usefully low resonance frequency of 650Hz (which means I can probably get away without the need for a resonance trap circuit) that will be used from around 3kHz. It will extend cleanly without break up to beyond 20kHz, which is fantastic performance for a $25 tweeter.
All up, the drivers cost around US$314, which compares more than favourably with the US$1,200 for the E-V drivers.
Thirdly, the PFM-Special must be easy to build. This means a rectangular box with straight edges (OK, maybe a bit of a rounding over) - but no fancy curves, radiused profile or tricky joinery. I'm planning to use 18mm MDF for the main carcass, which will then be clad with 18mm marine ply. Others may choose to use MDF for the outside as well. No need for expensive hardwoods.
Finally, the PFM-Special must be true to the flat-earth listener. It will use acoustic suspension loading principles to produce a tight and tuneful bass. The bass extension won't be as low as a 'Brik, but that should make it more sympathetic to boundary placement whilst not being entirely dependent on it. Will have to suck this one and see what results.
Other design criteria includes ease of drive with minimum impedence phase swings, and I'll endeavour to keep the impedence minima above 5-ohms.
Work on the cabinet will start in earnest when the E-V cabinet is completed. I intend to measure both designs at the same time so that I need to place only one order for XO components.
Stay tuned.
James
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