Hi,
This was prompted by the rather excellent performance of the
Vifa TC9FD18-08 :Zaph|Audio see the Dec 4th 2011 entry.
Vifa TC9FD18-08, 3.5" Full Range: Madisound Speaker Store
Now have a look at MJK's : http://www.quarter-wave.com/OBs/OB_Design.pdf
My suggestion for the woofer to go with the above is two of these :
GRS 12PF-8 12" Paper Cone Foam Surround Woofer 292-412
Criminally cheap for 4. Will be 93dB sensitivity for a pair albeit 4 ohms.
Use MJK's baffle and FR positioning, stack the woofers below.
Remember to chamfer properly the rear of the FR's opening.
For the bass c/o in MJK's article you need to halve the inductor value
and double the capacitor value, which works out cheaper, all good ....
Other than modest efficiency what is there to complain about ?
(Though the circa 85dB on axis may sound a bit more in room
due to the extra rear radiation, for farfield listening postions.)
I haven't built them, but they seem a compelling proposition.
rgds, sreten.
P.S. don't think for one minute these are high power handling
speakers because the two bass units give a rating of 240W.
They will be suited to normal modest hifi amplification.
This was prompted by the rather excellent performance of the
Vifa TC9FD18-08 :Zaph|Audio see the Dec 4th 2011 entry.
Vifa TC9FD18-08, 3.5" Full Range: Madisound Speaker Store
Now have a look at MJK's : http://www.quarter-wave.com/OBs/OB_Design.pdf
My suggestion for the woofer to go with the above is two of these :
GRS 12PF-8 12" Paper Cone Foam Surround Woofer 292-412
Criminally cheap for 4. Will be 93dB sensitivity for a pair albeit 4 ohms.
Use MJK's baffle and FR positioning, stack the woofers below.
Remember to chamfer properly the rear of the FR's opening.
For the bass c/o in MJK's article you need to halve the inductor value
and double the capacitor value, which works out cheaper, all good ....
Other than modest efficiency what is there to complain about ?
(Though the circa 85dB on axis may sound a bit more in room
due to the extra rear radiation, for farfield listening postions.)
I haven't built them, but they seem a compelling proposition.
rgds, sreten.
P.S. don't think for one minute these are high power handling
speakers because the two bass units give a rating of 240W.
They will be suited to normal modest hifi amplification.
Last edited:
Similar to these
Here's a similar design.
The best affordable DIY open baffle loudspeaker I've listened to so far.
Here's a similar design.
The best affordable DIY open baffle loudspeaker I've listened to so far.
Hi,
Yes it is similar but also different it some respects. The main difference
is the nominal difference in the bass driver and FR drivers sensitivity.
In the ultra this is 2dB and in the above its 8dB, its all very much
as described by MJK. In his article the difference is 6dB but I recall
reading somewhere for the active version the bass was lifted by a
further 2dB for best balance so 8dB should be fine.
I can't comment on now the Ultra 2dB (+ the drivers 3.5dB peak)
works compared to MJK's design, but I guess baffle size needs
to be a lot larger so you get less baffle loss in the bass.
The above is much closer to MJKs arrangement, you've got a total
difference of 12dB at 35Hz (driver has a 4dB peak) to play with.
I would be tempted to fold the baffle a little to reduce width,
but inherent in the above arrangement is the baffle loss that
is needed for balance allows a relatively small baffle.
It is very much a version of MJK's design, a very cheap version.
rgds, sreten.
Hi, the real star is of course MJK, (and Zaph), great article, rgds, sreten.
Prices
Hi,
The Vifa FR's are $12 each
Vifa TC9FD18-08, 3.5" Full Range: Madisound Speaker Store
The GRS bass units $12 each (for 4)
GRS 12PF-8 12" Paper Cone Foam Surround Woofer 292-412
The inductors are $11 each
4.0mH 18 AWG I Core Inductor 266-562
4.5mH 18 AWG I Core Inductor 266-564
The FR film capacitors $7 each
Dayton Audio DMPC-25 25uF 250V Polypropylene Capacitor 027-438
The bass unit capacitors $7 pair
125uF 100V Non-Polarized Capacitor 027-362
Dayton Audio DMPC-10 10uF 250V Polypropylene Capacitor 027-428
That makes a grand total of ~ $125 per pair (+postage).
rgds, sreten.
Air cored inductors with reasonably low DCR don't make any real sense
here, it would be cheaper to go active with T-amps than buying those.
Hi,
The Vifa FR's are $12 each
Vifa TC9FD18-08, 3.5" Full Range: Madisound Speaker Store
The GRS bass units $12 each (for 4)
GRS 12PF-8 12" Paper Cone Foam Surround Woofer 292-412
The inductors are $11 each
4.0mH 18 AWG I Core Inductor 266-562
4.5mH 18 AWG I Core Inductor 266-564
The FR film capacitors $7 each
Dayton Audio DMPC-25 25uF 250V Polypropylene Capacitor 027-438
The bass unit capacitors $7 pair
125uF 100V Non-Polarized Capacitor 027-362
Dayton Audio DMPC-10 10uF 250V Polypropylene Capacitor 027-428
That makes a grand total of ~ $125 per pair (+postage).
rgds, sreten.
Air cored inductors with reasonably low DCR don't make any real sense
here, it would be cheaper to go active with T-amps than buying those.
Last edited:
The Vifas have been pretty successful in this role in several designs. I think they sound pretty good. The graphs actually look pretty good for an extended range driver.
Vifa TC9FD-18-08 3-1/2" Full Range Paper Cone Woofer 264-1062
http://www.parts-express.com/pdf/264-1062s.pdf
Hi,
Given the above I don't think so but off axis response would be limited,
like all FR's. Yes you could add a tweeter but you'd be moving away
from MJK's basic premise. The off axis responses in the PDF suggest
a slightly off axis response could be flatter and a respectable power
response. Compared to similar drivers the highs won't suck at all.
For a real graph (Zaph's) the response looks very impressive to me.
I guess an option would be to look at this co-axial if a tweeter is needed:
http://www.parts-express.com/pdf/264-827s.pdf
Might work well with a zobelled bass/mid and high 1st order (series) x/o
to hit ~ 2nd order L/R acoustic around the x/o point, drivers out of phase.
rgds, sreten.
(Yes PE do do the Vifa, so that would be $120 a pair delivered free ....)
Last edited:
Sreten,
Vifa TC9FD-18-08 3-1/2" Full Range Paper Cone Woofer 264-1062, from the spec. sheet the eff. is about 84dB and a PAIR in parallel should give you about 90dB not 93dB as you implied.
BTW, I use Mark Audio Ch-70 mark III the eff. is about 85.5dB and a parallel PAIR in dipole config. in a box gives me about 91.5dB good enough for my 10W tube amp.
Vifa TC9FD-18-08 3-1/2" Full Range Paper Cone Woofer 264-1062, from the spec. sheet the eff. is about 84dB and a PAIR in parallel should give you about 90dB not 93dB as you implied.
BTW, I use Mark Audio Ch-70 mark III the eff. is about 85.5dB and a parallel PAIR in dipole config. in a box gives me about 91.5dB good enough for my 10W tube amp.
Hi,
You need to read more carefully, the 93dB refers to the pair of suggested
bass units, not the driver itself. You have to mean bipole as opposed to
dipole, and quite frankly what has that got to do with this OB thread ?
Seems your just lazy and haven't worked out what this thread is about.
rgds, sreten.
Last edited:
I know you have contributed a lot to this forum this does not mean you can start accusing whoever you want. I may have misread your post you don't have this rude it does go very far.
Goodbye I leave this forum to you and your follower.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.