Project post reserved for progress updates.
Crossover – Crossover 3-Way 8 Ohm 800/4,500 Hz 200W
The woofer section rolls off 6 dB at 800 Hz while the tweeter section uses a 12 dB per octave roll off at 4,500 Hz. The midrange section uses a true band pass filter with a response of 750-5,000 Hz. 12 dB per octave roll off. All crossover frequencies are rated into a 8 ohm load. Net weight: 1-1/2 lbs. Dimensions: 7″ W x 4″ D x 1-1/2″ H. Replacement tweeter protector #260-231.
After doing much research into crossover construction & design, I have settled on an easy pre-made one to use for the speaker stands for this project. The crossover points at 800hz & 4,500hz should be a good fit & allow for a broad range of speaker selection. The 8ohm load should provide for the option to go with single 8ohm or dual 4ohm in series drivers, and the 200watt capacity should keep the whole thing from frying when loaded with dual drivers per output terminal.
Highs – Dayton Audio PT2C-8 Planar Tweeter
*Power handling: 80 watts RMS/115 watts max *Impedance: 8 ohms *Re: 6.9 ohms *Ribbon radiating area: 120 mm x 27 mm *Frequency range: 2,000-26,000 Hz *SPL: 94 dB 1W/1m *Dimensions: A: 6-5/8″ x 3-1/2″, B: 2-5/8″ x 6-3/16″, C: 7/8″.
This piece of mechanical wonder is very high tech. The key to the remarkable performance of this speaker is the almost weightless ribbon element: a Kapton film membrane etched with a pattern of aluminum conductors and placed precisely between two rows of neodymium magnets. The result is an immediate response to any transient impulse found in the original signal. Very high tech stuff. The best part of this speaker is the fact that it floats along at 80-115watts, perfectly in line with the rest of the audio components. Most tweeters you find are 15-30watts and require a hefty resistance to offset the power being put into a floor unit. I really couldn’t have asked for a better match for the crossover. With the crossover high pass cutoff residing at 4,500hz, even though it is a 2nd order 12db/octave slope, this tweeter will be safe from damaging lower frequencies as it is rated for sound all the way down to 2,000hz. I really cant wait to hear what this sounds like.
Mid – Pyle Pro PDMR5 5” Sealed Back Midrange
Power handling: 100 watts RMS/200 watts max • Impedance: 8 ohms • Frequency response: 450-7,000 Hz • SPL: 92 dB 1W/1m • Dimensions: Overall diameter: 5-1/8″, Cutout diameter: 4-3/8″, Depth: 2″.
This driver is an excellent choice in both power handling & the fact that it is sealed. By choosing sealed mid & high drivers for this application I will be free to min-max the available space within the enclosure – the mid & high’s will not require their own segregated enclosure within the floor unit. This allows the floor unit itself to be smaller overall.
Since the pre-made crossover does not contain any Zobel filters, I am going to try to keep all of the drivers around the same wattage. At some point in the future I would like to try constructing my own crossover to get around such limitations in future projects.
Low – Dayton Audio DC250-8 10” Classic Woofer
Power handling: 70 watts RMS/105 watts max • Voice coil diameter: 1-3/8″ • Le: 2.57 • Impedance: 8 ohms • Re: 6.7 ohms • Frequency response: 25-2,500 Hz • Magnet weight: 20 oz. • Fs: 29 Hz • SPL: 89 dB 1W/1m • Vas: 3.93 cu. ft. • Qms: 4.05 • Qes: 0.50 • Qts: 0.45 • Xmax: 4.5 mm • Dimensions: Overall Diameter: 10-1/16″, Cutout Diameter: 9-5/16″, Mounting Depth: 4-7/16″, Magnet Diameter: 4-3/16″, Magnet Height: 1-1/4″.
This driver has excellent lows for a driver of its class. Digging deep down to 25hz this driver will provide all the sound from 25-850hz for the units.
Wood – Cherry gloss finish
I’m fond of this type of finish for the wood. Instead of MDF I think I’ll go with Oak Hardwood Plywood finished to something similar to this
As we can see from the calculations done for the
selected woofer, we have the option of going with a 2.67 cubic foot enclosure (too small likely) at a unappealingly high resonant frequency of 45.5hz, or a vented enclosure with 5.68 cubic feet (much better) and a nice deep resonant frequency of 25.9hz. Port diameter of 4” will require a length of 5.68”, tapered on both ends.
Precision Port 4″ Flared Port Tube Kit
Dimensions: • 7-1/4″ outside flare outer diameter • 6-1/4″ cutout • 6-3/16″ inside flare outer diameter. 17” long tube.
This guy will provide the 4 inch wide, 5.68 inch long port I will need to have a nice high peak at 25.9hz. Looking forward to hearing it. With floor speakers that dive down as deep as these, I’m really going to have to pull off something special with the stand alone subwoofer unit to beat the lows on these guys.
Subwoofer – Dayton Audio RSS390HF-4 15″
Power handling: 500 watts RMS/800 watts max • VCdia: 2-1/2″ • Le: 1.00 mH • Impedance: 4 ohms • Re: 3.3 ohms • Frequency range: 18 – 800 Hz • Fs: 18 Hz • Magnet weight: 150 oz. • SPL: 90 dB 2.83 V/1m, 87 dB 1W/1m • Vas: 9.95 cu. ft. • Qms: 3.10 • Qes: 0.49 • Qts: 0.42 • Xmax: 14 mm • Dimensions: Overall diameter 15-5/16″, Cutout diameter 14-1/8″, Depth 6-1/8″.
The power handling exactly matches my Kenwood amp (two channel 500w@2ohms) and should do well to complement the rest of the acoustics of the audio system. With proper porting this subwoofer should reach lows of 16.9hz. Earthquake anyone?
From the calculations, I will need a vented enclosure to reach the low frequencies required for ROI of this driver. A vented enclosure having a volume of 11.3 cubic feet with a 6 inch wide port 17.5 inches long. A port that long will likely be done using an angled port.
Standing Floor Speaker
Created exclusively for the drivers listed in this project, tuned to 25Hz. **not pictured – floor foot pegs, internal bracing**
Picture pending design completion.
so, after subjecting this to the pros at AVS forum, I’ll be scrapping this speaker & going for a proven design.
like always, i end up biting off more than i can chew. may as well do it again with the next project – see MMThree Clone project.