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https://www.decware.com/cgi-bin/yabb22/YaBB.pl SUPPORT FORUMS FOR DECWARE SPEAKER PLANS >> Deathbox Support Forum >> DB210 pedestal tube project - tuning troubles! https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1192691792 Message started by PC on 10/18/07 at 08:16:31 |
Title: DB210 pedestal tube project - tuning troubles! Post by PC on 10/18/07 at 08:16:31 Hi Guys, As a bit of background to my project I have recently built to working stage a 4 foot long 1 foot diameter tube DB using 2 x 10" dual voice coil drivers in isobarik, based loosely between Steve's original square boxed DB10 and 212 designs. It differs because it is of a tube design, and also is tunable on-the-move - ie I dont have to disassemble the end/s to move the inner tube/drivers up and down - I tune via a 5/8" threaded rod (with a nut welded on the end) going through the top plate and threaded through another nut welded to struts connected to the inner tube/drivers . Anti clockwise (from top) pushes down, clockwise pulls up! The whole time it remains sealed thanks to self adhesive closed cell foam strips and a fine mist of silicon lube on the tube inner wall. I am very happy with the type of sound produced, and want to commend Steves on his rubber throat design idea - much more musical than a uniform cylindrical port in my experience! I am using 2 x 140W monblocks (1 for each 10" dual voicecoil driver) and can connect the drivers in any parallel series combination; I have connected each VC to a pair of terminals on the outside of the tube. I am however unhappy with the performance of my project in one aspect.... I am querying as to how it seems best tuned- its lowest frequencys and smoothest band seems to be produced when the flange plate is only 20mm from the bottom plate - but is still annoyingly ringy/peaky around the 100Hz and above range- mainly evident with tracks containing these bass music notes? At low volumes it seems to benefit being even closer to the bottom plate with a smoother bandwidth (less peaky around 100Hz up) , but at the expense of chuffing when playing at higher levels. I am worried that I may have chosen 10" drivers with parameters not suited to this design, or could there be a simple fix? Questions I have asked myself, but cannot exactly answer and hope you could help me with are: 1. Could I stuff more polyester fill tightly into the sealed chamber thus reducing effective volume? 2. Given the driver's parameters (see attached) and design of my tube, what would be better - wiring the drivers dual Voice Coils in series or parallel? 3. I am also worried that I may have made the flange plate opening rather small - I notice Steve's original flange covers around half the cross sectional area of the box - whereas mine covers 3/4 of the cross sectional distance across my tube- about 1/5 of the area - should I remove the flange plate and trim to half the distance across? Specifications: * Nominal Impedance : 2 x 2 Ohm Voice Coils * Power Handling: 250 Watts RMS * Sensitivity: SPL - 87.2 db - 1 Watt @ 1 metre * Voice Coil Resistance (Re): 1.3 Ohms * Resonant Frequency (Fs): 23.7Hz * Mechanical Q Factor (Qms): 3.976 * Electrical Q Factor (Qes): 0.382 * Total Q Factor (Qts): 0.348 * Equivalent Volume (Vas): 66.085 litres * Voice Coil Diameter: 65mm BASV * Xmax: 10mm * Speaker Dimensions: A 274, B 250, C 235 Specifications are for 1 driven voice coil only My Volumes for the tube are as follows – Upper sealed is 42L without Polyester fill. 12 litres is taken up by the flange plate/ throat volume when tuned to best listening position. The coupled isobaric driver chamber volume (irrelevant I suppose) is 16.5L. I can email a Word doc for more pics and details for anyone curious! Any informative help would be much appreciated! Thanks Steve & guys PC |
Title: Re: DB210 pedestal tube project - tuning troubles! Post by Bart_West-VL. on 10/18/07 at 16:50:25 1. Better put something solid in there, to reduce volume. 2. Both speakers MUST be connected parallel, each speaker can have the DVC wired in series. Now you have only 2 Ohm. (1 DVC in series = 4 Ohm ... both drivers in parallel = back to 2 Ohm) Or if you're amp can take it, wire everything parallel → 0.5 Ohm 8-) 3.Yes, trim it. I would like to see some pics now. :D |
Title: Re: DB210 pedestal tube project - tuning troubles! Post by Bart_West-VL. on 10/18/07 at 16:54:41 I forgot to say; The DB10" also has a second resonance, at ±125hz. Set you're crossover to maximum 80hz or less. B. |
Title: Re: DB210 pedestal tube project - tuning troubles! Post by Adrian on 10/18/07 at 17:08:29 the 125hz resonance is really nasty :( |
Title: Re: DB210 pedestal tube project - tuning troubles! Post by 60_and_up on 10/18/07 at 20:00:21 subwoofer - 60-80hrtz and down only. |
Title: Re: DB210 pedestal tube project - tuning troubles! Post by PC on 10/19/07 at 04:42:15 Thanks fellas. Whats a good starting point to reduce the sealed chamber volume? 1.I will connect DVC in series, and then drivers in parallel - my amps are stable to 2 ohms, delivering then 200Wrms. Not stable below that load. 2.Can I hook up the two drivers each with their own amp? - Or not the same result? 3. I will trim the Duct flange. [img][/img] |
Title: Re: DB210 pedestal tube project - tuning troubles! Post by PC on 10/20/07 at 07:41:53 Here is a view of the duct on the outer Tube. Tube will be painted with iron oxide paint to make it look a rusty one piece cast iron pedestal. |
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