Curious_George Posted June 14, 2012 Share Posted June 14, 2012 Hello All, New to the forum, but not audio. I've recently procured some 1979 Heresy's from the original owner. I've been itching to build something lately and I don't want to cut or hack on the Heresy's. Reading through the posts about ported Heresy's, I found an MCM woofer that appears to have the correct specs to work well in 2 cubic foot ported enclosure (http://www.mcmelectronics.com/product/MCM-AUDIO-SELECT-55-2952-/55-2952). Anybody tried this or have any comments? I figure you could make a new back panel with a port and easily convert from sealed to vented without compromising the original speaker too much, plus you could easily "restore" it for resale value if you wanted. Quote Link to comment Share on other sites More sharing options...
djk Posted June 14, 2012 Share Posted June 14, 2012 What makes you think that will work in a 2 cu ft box? The Qts and Vas suggest more like 4 cu ft to me. (I have four of that driver) Quote Link to comment Share on other sites More sharing options...
Curious_George Posted June 14, 2012 Author Share Posted June 14, 2012 Well plugging in the "advertised" specs yields an F3 of 50Hz, tuned to 45Hz in a 2 cubic foot box, which is roughly the volume of a Heresy. If the average original Heresy has a roll off of 60~65Hz, then extending that down to 50Hz (for $25) might be worth something. In addition, room gain will net you a few extra dB of bottom end, depending on your speaker placement. When I get my woofer samples, I'll run them on the Klippel and confirm the T/S parameters. Of course there is nothing like building sample enclosures and hearing the results. Quote Link to comment Share on other sites More sharing options...
djk Posted June 15, 2012 Share Posted June 15, 2012 I'm using them in 2.5 cu ft tuned to 50hz (actually a pair in 5 cu ft), and they're not bad. The Heresy I and II are about 1.85 ft^3 gross (21.375"x15.5"x13.25" with a setback of .25 for grill, 3/4" construction), and with the rear-mounting of the original woofer driver, network, and horns I figure about 1.6 ft^3 net. If you do build a 2 ft^3 (net) box and tune it to 50hz, it will be about 3dB down at 50hz according to BBPro v6.0 Name: 55-2952 Type: Standard one-way driver Company: MCM No. of Drivers = 1 Fs = 38 Hz Qms = 2.8 Vas = 108 liters Cms = 0.271 mm/N Mms = 64.8 g Rms = 5.525 kg/s Xmax = 4 mm Xmech = 6 mm P-Dia = 259.8 mm Sd = 530 sq.cm P-Vd = 0.212 liters Qes = 0.385 Re = 7.2 ohms Le = 1 mH Z = 8 ohms BL = 17.01 Tm Pe = 100 watts Qts = 0.338 no = 1.484 % 1-W SPL = 93.86 dB 2.83-V SPL = 94.32 dB ----------------------------------------- Box Properties Name: Type: Vented Box Shape: Prism, square Vb = 2 cu.ft Fb = 50 Hz QL = 7 F3 = 49.93 Hz Fill = minimal No. of Vents = 1 Vent shape = round Vent ends = one flush Dv = 4.091 in Lv = 3.278 in **************************************** In 1.6 ft^3 tuned to 42hz (4" dia x 9" long, a 4" 90° elbow is about right) they're about 7dB down, with 'room gain' it might sound reasonable, and the group delay looks much better on this design. Quote Link to comment Share on other sites More sharing options...
Curious_George Posted June 15, 2012 Author Share Posted June 15, 2012 So our data (and thinking) yield similar results. My plan is to build some Heresy "clones" for home theater. I wanted the main speakers to go down to at least 50Hz so my sub could take over from there. I prefer the sound of paper cones, even for bass. And the treated cloth accordion surrounds seem to last forever. I have the space for larger enclosures, but try and balance performance vs size. Quote Link to comment Share on other sites More sharing options...
cheric Posted June 15, 2012 Share Posted June 15, 2012 I am using two of these right now in my (Heresy) Extreme and they seem to work well. BTW, they are on sale, only $15 each. http://www.mcmelectronics.com/product/55-2952&t=1 Quote Link to comment Share on other sites More sharing options...
Curious_George Posted June 15, 2012 Author Share Posted June 15, 2012 %*%^@#$ and I just ordered some a few days ago at the "normal" price. MCM = Stupid Head. (Sheldon from Big Bang Theory) Quote Link to comment Share on other sites More sharing options...
cheric Posted June 15, 2012 Share Posted June 15, 2012 For the (current) price tags, they are worth a try! Quote Link to comment Share on other sites More sharing options...
djk Posted June 15, 2012 Share Posted June 15, 2012 Note: This driver does have some glue issues at the attach point of the cone/spider/coil. It is probably fine for home use. Quote Link to comment Share on other sites More sharing options...
cheric Posted June 16, 2012 Share Posted June 16, 2012 Shipping is $5......Only for this weekend (shipping price). Quote Link to comment Share on other sites More sharing options...
Pete H Posted June 16, 2012 Share Posted June 16, 2012 Note: This driver does have some glue issues at the attach point of the cone/spider/coil. It is probably fine for home use. What's your opinion as to their possible application in a KP250 that is already ported? Quote Link to comment Share on other sites More sharing options...
djk Posted June 16, 2012 Share Posted June 16, 2012 "possible application in a KP250" No where near as efficient as it would need to be, and won't handle the power. Quote Link to comment Share on other sites More sharing options...
Curious_George Posted June 18, 2012 Author Share Posted June 18, 2012 I'm using them in 2.5 cu ft tuned to 50hz (actually a pair in 5 cu ft), and they're not bad. The Heresy I and II are about 1.85 ft^3 gross (21.375"x15.5"x13.25" with a setback of .25 for grill, 3/4" construction), and with the rear-mounting of the original woofer driver, network, and horns I figure about 1.6 ft^3 net. If you do build a 2 ft^3 (net) box and tune it to 50hz, it will be about 3dB down at 50hz according to BBPro v6.0 Name: 55-2952 Type: Standard one-way driver Company: MCM No. of Drivers = 1 Fs = 38 Hz Qms = 2.8 Vas = 108 liters Cms = 0.271 mm/N Mms = 64.8 g Rms = 5.525 kg/s Xmax = 4 mm Xmech = 6 mm P-Dia = 259.8 mm Sd = 530 sq.cm P-Vd = 0.212 liters Qes = 0.385 Re = 7.2 ohms Le = 1 mH Z = 8 ohms BL = 17.01 Tm Pe = 100 watts Qts = 0.338 no = 1.484 % 1-W SPL = 93.86 dB 2.83-V SPL = 94.32 dB-----------------------------------------Box Properties Name: Type: Vented Box Shape: Prism, square Vb = 2 cu.ft Fb = 50 Hz QL = 7 F3 = 49.93 Hz Fill = minimal No. of Vents = 1 Vent shape = round Vent ends = one flush Dv = 4.091 in Lv = 3.278 in **************************************** In 1.6 ft^3 tuned to 42hz (4" dia x 9" long, a 4" 90° elbow is about right) they're about 7dB down, with 'room gain' it might sound reasonable, and the group delay looks much better on this design. MCM 55-2952 Real T/S Parameters measured via Klippel Electrical Parameters #1 Re 8.26 Ohm electrical voice coil resistance at DCLe 0.623 mH frequency independent part of voice coil inductanceL2 0.860 mH para-inductance of voice coilR2 9.38 Ohm electrical resistance due to eddy current lossesCmes 981.24 µF electrical capacitance representing moving massLces 15.24 mH electrical inductance representing driver complianceRes 18.62 Ohm resistance due to mechanical lossesfs 41.2 Hz driver resonance frequency Mechanical Parameters (using laser) Mms 58.935 g mechanical mass of driver diaphragm assembly including air load and voice coilMmd (Sd) 51.689 g mechanical mass of voice coil and diaphragm without air load Rms 3.225 kg/s mechanical resistance of total-driver lossesCms 0.254 mm/N mechanical compliance of driver suspensionKms 3.94 N/mm mechanical stiffness of driver suspensionBl 7.75 N/A force factor (Bl product)Lambda s 0.059 suspension creep factorLoss factors Qtp 1.453 total Q-factor considering all lossesQms 4.726 mechanical Q-factor of driver in free air considering Rms onlyQes 2.097 electrical Q-factor of driver in free air considering Re onlyQts 1.452 total Q-factor considering Re and Rms onlyVas 107.6013 l equivalent air volume of suspension n0 0.344 % reference efficiency (2 pi-radiation using Re) Lm 87.56 dB characteristic sound pressure level (SPL at 1m for 1W @ Re)Lnom Zn missing dB nominal sensitivity (SPL at 1m for 1W @ Zn)rmse Z 2.30 % root-mean-square fitting error of driver impedance Z(f)rmse Hx 1.75 % root-mean-square fitting error of transfer function Hx (f)Series resistor 0.00 Ohm resistance of series resistorSd 547.39 cm² diaphragm areaElectrical Parameters #2 Re 8.14 Ohm electrical voice coil resistance at DCLe 0.592 mH frequency independent part of voice coil inductanceL2 0.966 mH para-inductance of voice coilR2 10.07 Ohm electrical resistance due to eddy current lossesCmes 701.90 µF electrical capacitance representing moving massLces 19.51 mH electrical inductance representing driver complianceRes 24.45 Ohm resistance due to mechanical lossesfs 43.0 Hz driver resonance frequency Mechanical Parameters (using laser) Mms 58.453 g mechanical mass of driver diaphragm assembly including air load and voice coilMmd (Sd) 51.207 g mechanical mass of voice coil and diaphragm without air load Rms 3.407 kg/s mechanical resistance of total-driver lossesCms 0.234 mm/N mechanical compliance of driver suspensionKms 4.27 N/mm mechanical stiffness of driver suspensionBl 9.13 N/A force factor (Bl product)Lambda s 0.045 suspension creep factorLoss factors Qtp 1.159 total Q-factor considering all lossesQms 4.637 mechanical Q-factor of driver in free air considering Rms onlyQes 1.543 electrical Q-factor of driver in free air considering Re onlyQts 1.158 total Q-factor considering Re and Rms onlyVas 99.3444 l equivalent air volume of suspension n0 0.492 % reference efficiency (2 pi-radiation using Re) Lm 89.12 dB characteristic sound pressure level (SPL at 1m for 1W @ Re)Lnom 89.05 dB nominal sensitivity (SPL at 1m for 1W @ Zn)rmse Z 2.09 % root-mean-square fitting error of driver impedance Z(f)rmse Hx 1.89 % root-mean-square fitting error of transfer function Hx (f)Series resistor 0.00 Ohm resistance of series resistorSd 547.39 cm² diaphragm area In addition, the voice coil assembly appears to be out of the magnetic gap. Like they used the wrong "jig" when assembling the woofer. This may account for the low BL product since the VC is barely in the magnetic gap. If the manufacturing quality was better, this woofer might perform quite well in small(er) enclosure. Quote Link to comment Share on other sites More sharing options...
Curious_George Posted August 3, 2012 Author Share Posted August 3, 2012 I tried the MCM woofers listed earlier in this post ans was not happy with the results. I recently came across a woofer that appears to be a great candidate for a "Ported" Heresy project, the Celestion TF1225. They are only $56.99 from J&R Music World. http://celestion.com/product/102/tf1225/ I am currently testing a 3.5 cubic ft ported enclosure with TF1225 woofer, K55V mid / 700 horn and K77 Alnico tweeter. I am also using a Heresy Type E crossover slightly modified for said driver combination. I'll post frequency response graph, impedance graph and cross over schematics soon. So far it sounds great, just like a Heresy, but with more Bass. Preliminary testing shows the response down to about 45Hz (F3) in this enclosure. Quote Link to comment Share on other sites More sharing options...
djk Posted August 5, 2012 Share Posted August 5, 2012 $52 http://reconekits.com/celestiontruvox122512.aspx Quote Link to comment Share on other sites More sharing options...
Tony Reed Posted August 5, 2012 Share Posted August 5, 2012 So how would this woofer work in the Heresy 1? If not, what would be a good "economical" choice? Thanks Tony Quote Link to comment Share on other sites More sharing options...
Curious_George Posted August 5, 2012 Author Share Posted August 5, 2012 This woofer is not suitable for a direct replacement in a Heresy. I am not certain what "economical" choices there are out there. I certain that particular topic has come up a good many times. Use the search function and see what comes up. I am fairly new here myself. CG Quote Link to comment Share on other sites More sharing options...
Tony Reed Posted August 6, 2012 Share Posted August 6, 2012 I hope djk will chine in on this. Quote Link to comment Share on other sites More sharing options...
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