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In Reply to: RE: cheap 15" woofer rated to 50Hz with sealed Q of .72, or a high power one rated to 23Hz with a Q of 1.35? posted by thump on October 30, 2016 at 01:06:58
WELL seeing as the forum has deleted a couple REPLACEMENT paragraphs i tried to re-do AGAIN, i'll start ANOTHER post to discuss the alternative.as i've already said TWICE, i wasn't liking the MCM's 50Hz cutoff or 200w power limitation as my planet audio amp CLAIMS 600w bridged at 4 ohms, so i looked for a beefier woofer. after some research, i stumbled on a "top 10 affordable 15" subs" list that mentioned VM audio as the cheapest of the bunch, so i looked those up and read some reviews. for $70, they seem to have a lot going for them... similar 91dB ratings, a much lower 23Hz cutoff, higher power handling, & better overall looks with a nice plump rubber surround and no cheesy stamped steel basked edge or cardboard trim ring showing.
https://www.vminnovations.com/Product_56154/VM-Audio-Elux-15-Inch-Competition-Subwoofer-EXW15-.html#features
TECHNICAL SPECIFICATIONS
Nominal Impedance: Dual 4 Ohm
RMS Power: 1300W
Peak Power Handling: 2600W
Voice Coil Diameter:2.5" (60.6mm)
Magnet Weight: 49.6oz * 2
Frequency Response: 23Hz - 340Hz
Clone Material: Polypropylene
Surround Material: Butyl Rubber
Mounting Diameter: 13.54"(344mm)
Mounting Height: 7.24" (184mm)
Warranty: 1 YearPARAMETERS
Free Air Resonance (Fs): 32 Hz
Driver Total Q (Qts): 0.8
Electrical Q (Qes): 1
Mechanical Q (Qms): 4
Equivalent Stiffness (Vas): 99 Ltr (3.5 cubic feet)
Driver Compliance (Cms): 0.12 mm/N
Moving Mass (Mms): 205 g
Effective Cone Area (Sd): 194 sq.cm
Inductance 1kHz (Le): 2.4 mh
Motor Force (BL): 17.1 T-M
Efficiency (no): 0.26%
Sensitivity (SPL @1W/1m): 91 dB
D.C. Coil Resistance (Re): 7.2 ohm ea.the PROBLEM is that when i ran the numbers, this woofer has a Q of 1.35 in the box which, as far as i understand, means that it might cause a hollow boxy sound.
the peak doesn't look too pronounced, and i know that a Q of 1 is considered acceptable. the reason i'm here is to find out if the Q is a deal breaker for this box or not as otherwise, this woofer will have about 5dB more output at 20Hz BEFORE even accounting for its superior extension.
i place sound quality over SPL which is why i'm sticking with a sealed box instead of ported. i just don't like the boomy sloppy sound of port no matter how many port lovers get offended that anyone would prefer lower distortion over resonant bloat. i like the sound of 8 inch sealed subs, but this is intended to be a dance system, so moving some air at the bottom octaves is important too, but i want to keep as tight a thump on it all as possible.
the 15" is a temporary sub until i can afford the 12s, but i might even go with 8 x 10s if i go all out and do carbon fiber over glass on the final system.
right now, i'm looking to get the biggest thump i can out of my amp and up to about $100 in woofer & box.
so what do YOU think? is that VM audio woofer a worthy upgrade over the MCM despite the 1.35Q?
Edits: 10/30/16 10/30/16Follow Ups:
HERE'S the curve i calculated for the MCM woofer that can NEVER be put back into the original post as every time i try to go into edit to add it back, where it belongs, i just lose everything else again. i SHOULD be able to add EVERY PIC in a post in just one pass and have them in the right place too at that instead of having to copy them from the top and paste them back where they belong. i've wasted an HOUR trying to fix the asylum's mistakes already.
anyways, THAT's the MCM curve. to my eye, the VM beats it in every way EXCEPT for having that 54Hz resonant peak i'm hoping is really more of a molehill than a mountain.
THIS TIME I DIDN'T EVEN ATTEMPT TO EDIT THE ORIGINAL POST, BUT IT EFFING GOT CUT OFF AGAIN!!! ABOUT THE TENTH EFFING TIME!!! FIX THAT CRAP ASYLUM!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
the REST of the MCM specs
General Specifications:
Nominal Diameter: 15 inch
Rated Impedance: 4Ohms
Operating Bandwidth: 50 ~ 3KHz (-3dB)
Power Handling Capacity: 200W RMS
Sensitivity (1W/M): 92dB (±3dB)
Voice Coil Diameter: 2 inch
Thiele-Small Parameters:
Resonance Frequency Fs: 32.5Hz
DC Resistance Re: 3.4O
Mechanical Q Factor Qms: 3.203
Electrical Q Factor Qes: 0.5342
Total Q Factor Qts: 0.4578
Equivalent Cas air load Vas: 322.23 L
Surface Area of Cone Sd: 0.0840 m2
Efficiency Bandwidth Product EBP 60.8
Voice Coil Over Hang X-max 6 mm
Physical Information:
Cutout: 13.82"
Mounting Depth: 5.63"
Basket: Pressed steel chassis
Magnet Type: 40.0 oz.
Cone Material: Polypropelyne
Surround: Rubber
Dust Cap: Polypropelyne
Damper: Cloth
you know, it's been so many times trying to fix what the asylum keeps breaking, i can't even remember what i had to add to this anymore and i'm too infuriated to care at this point. the basic statistics are all here now and i'm sure many of you are more well versed in thiele small theory than i am and can connect the dots yourselves.
seeing it's a dual voice coil sub, there are 3 options for wiring it
- both coils in parallel for a 2 ohm load (i don't like the "blow my amp up whydoncha?" sound of)
- run each of the coils to one channel of a 4 ohm stereo pair (wouldn't that be a redundant waste of power?)
- run the coils in series for a nice happy 8 ohm load on one bridged channel (which would lower the available power)
every option has its drawbacks, but to me, frying an amp because of low impedance is the absolute worst choice, especially on an entry level unit.
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