Talking about Jamo, which is pronounced with a "J", I can say that I'm very impressed with the bass in their 907/909 dipoles. You can, with the help of the impedance curve
Stereophile: Jamo Reference R 907 loudspeaker
calculate that the drivers in these speakers (in baffle) have a Qts of about 0,62. The drivers are also claimed to have a sensitivity of 101 dB/w individually in free space, and a light and stiff cone. They also have long stroke capability!
I've done some experimenting see if I can simulate a driver like those Jamo drivers, but it seems to be impossible .....
Stereophile: Jamo Reference R 907 loudspeaker
calculate that the drivers in these speakers (in baffle) have a Qts of about 0,62. The drivers are also claimed to have a sensitivity of 101 dB/w individually in free space, and a light and stiff cone. They also have long stroke capability!
I've done some experimenting see if I can simulate a driver like those Jamo drivers, but it seems to be impossible .....
There here.......
OK.... Finally received four each of the PE DC380-8 fifteen inch specially priced woofers today... ($35.00 each on Thanksgiving weekend). After a 2-3 hour break-in at full excursion (16 Hz) & one hour cool down they have VERY similar T/S values.... good to see consistency at this price point.... Kudos to PE's Taiwanese manufacturer. The drivers look very good for the price. So far they appear to be quite a bargain. The results are averages as the individual drivers are all so close....
The Factory specs are: RE: 6.5, LE 3.34, FS 21.5, QM 3.52, QE .39, QT .35 & VAS 306L. SPL 92.8
The Measured specs are: RE: 6.2, LE 2.26, FS 18.1, QM 2.82, QE .34, QT .31 & VAS 432L. SPL 91 (prox)
All measurements via PE WT3. 3,000' elevation. We happened to have... for this part of the world, a record low barometer at the time (28.93") calibrated to sea level and hope this did not have a significant effect on the measured values. It is assumed the Xmax and other mechanical values are consistent with the advertised values.
So... we are in the Forest Gump "Box of Chocolates" world... usually most drivers have higher than advertised FS & QT... but here they both are lower.
Wouldn't you know it.... for the intended OB application this makes for some additional engineering... but they can still do the job well. As an aside... and as PE advertises... this woofer is well suited to a relatively small sealed box application, 2.4 cu. ft. stuffed will yield an F3 of around 38 Hz and a QTC about .84. This assumes a total RG of .65 Ohm. YMMV. May just mock up a 3 way monkey coffin with a HI-VI dome mid and Seas 27TDFC just for S&G's to see how it sounds.
Getting back to the intended OB application... just penciling out a basic design, it looks like 2 each of the 15's wired parallel in phase on an 18" wide baffle with a wing depth of 6"-8" and adding some significant series inductance 12-18 Mh, we should end up with a flat response to about 38 Hz with a 9-12 db per octave roll off below that. We will be trading away 9 db of efficiency to get this and end up with an half space operating efficiency of about 88 dbw. Again YMMV. I will do a heavy card board mock up this weekend and see if this pans out. After we see what we have I will then work on midrange integration issues. I hope to use the Tang Band 6-1/2" (W6-789E) woofer that was also on sale at $20 each with the DC380's. Undecided on the tweeter... but something inexpensive like the PE Silkie should do the trick. Trying to keep the driver cost per baffle around $100 or so. Also... the prices for the above are delivered and no sales tax.
That's it for now.
John
OK.... Finally received four each of the PE DC380-8 fifteen inch specially priced woofers today... ($35.00 each on Thanksgiving weekend). After a 2-3 hour break-in at full excursion (16 Hz) & one hour cool down they have VERY similar T/S values.... good to see consistency at this price point.... Kudos to PE's Taiwanese manufacturer. The drivers look very good for the price. So far they appear to be quite a bargain. The results are averages as the individual drivers are all so close....
The Factory specs are: RE: 6.5, LE 3.34, FS 21.5, QM 3.52, QE .39, QT .35 & VAS 306L. SPL 92.8
The Measured specs are: RE: 6.2, LE 2.26, FS 18.1, QM 2.82, QE .34, QT .31 & VAS 432L. SPL 91 (prox)
All measurements via PE WT3. 3,000' elevation. We happened to have... for this part of the world, a record low barometer at the time (28.93") calibrated to sea level and hope this did not have a significant effect on the measured values. It is assumed the Xmax and other mechanical values are consistent with the advertised values.
So... we are in the Forest Gump "Box of Chocolates" world... usually most drivers have higher than advertised FS & QT... but here they both are lower.
Wouldn't you know it.... for the intended OB application this makes for some additional engineering... but they can still do the job well. As an aside... and as PE advertises... this woofer is well suited to a relatively small sealed box application, 2.4 cu. ft. stuffed will yield an F3 of around 38 Hz and a QTC about .84. This assumes a total RG of .65 Ohm. YMMV. May just mock up a 3 way monkey coffin with a HI-VI dome mid and Seas 27TDFC just for S&G's to see how it sounds.
Getting back to the intended OB application... just penciling out a basic design, it looks like 2 each of the 15's wired parallel in phase on an 18" wide baffle with a wing depth of 6"-8" and adding some significant series inductance 12-18 Mh, we should end up with a flat response to about 38 Hz with a 9-12 db per octave roll off below that. We will be trading away 9 db of efficiency to get this and end up with an half space operating efficiency of about 88 dbw. Again YMMV. I will do a heavy card board mock up this weekend and see if this pans out. After we see what we have I will then work on midrange integration issues. I hope to use the Tang Band 6-1/2" (W6-789E) woofer that was also on sale at $20 each with the DC380's. Undecided on the tweeter... but something inexpensive like the PE Silkie should do the trick. Trying to keep the driver cost per baffle around $100 or so. Also... the prices for the above are delivered and no sales tax.
That's it for now.
John
Not too bad OB drivers with +/- 9 mm xmax and at a price of 20 Euros!
http://www2.produktinfo.conrad.com/...l-VISATON_WHC_30X8_OHM_HIFI_TIEF_de_en_fr.pdf
Additional data for this driver can be found in Visatons Boxsim driver data.
http://www2.produktinfo.conrad.com/...l-VISATON_WHC_30X8_OHM_HIFI_TIEF_de_en_fr.pdf
Additional data for this driver can be found in Visatons Boxsim driver data.
You can get the (German language) non-installment BoxSim program here:
Boxsim - Homepage
And the Visaton/Conrad driver data bank here:
http://www.visaton.de/downloads/conrad-serie-11-07-2008.zip
Run the program, press "Chassis&Einbau, then "Chassis 1", press "Chassis laden aus datei", choose the attached Conrad data bank, choose the WHC 30X driver and there you can see the additional data under "chassisdaten" and
"weitere daten"
Among other things, You can see that the voice coil height is 25 mm, and that the magnetic field transfer plate is 7 mm thick, which (theoretically) gives an Xmax of +-9 mm................................
Hasn't stopped raining!!
Hello all... a quick note.... still wanting to move forward with the PE DC 380 OB project... but it still keeps raining... to big a project to work - measure in my garage... full of stuff other than cars like most garages these days. Hopefully we will get a break this weekend and I will have some initial impressions... measurements soon... so hang in there!! Just FYI...
Hello all... a quick note.... still wanting to move forward with the PE DC 380 OB project... but it still keeps raining... to big a project to work - measure in my garage... full of stuff other than cars like most garages these days. Hopefully we will get a break this weekend and I will have some initial impressions... measurements soon... so hang in there!! Just FYI...
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