I'm certain they were bipole, not dipole. ie, both drivers firing in-phase.
I once mounted an 8" driver to a 12" square open baffle, and then EQ'd it flat to 30Hz. Result: even at very gentle listening levels, any LF content would cause large excursions. Turn it up a little, and the driver bottomed out. I tried similar with 15" drivers. With approx 30mm of p/p excursion, a pair of 15"s managed decent LF output.
There's a tradeoff with nearfield OBs: larger baffle = lower LF cutoff. However, a larger baffle will also block reflected sound coming back to you, which is part of the OB "sound" - the spacious presentation etc.
So, do you use small baffles and get the spacious sound, or big baffles, and have a weird boxy backwave?
If it was mine, I'd go with smallish sealed boxes and EQ the result. Less distortion in the LF range (due to much reduced excursion requirements), and (with adequate stuffing) a nice clean midrange.
They won't have the "spacious" OB sound, but I'm not a fan of that anyway.
Chris
Nice work. Creative and original in the best DIY spirit. Its has a very small footprint and efficient use of precious desk top surface area.
I imagine you get a nice high soundstage thats stable with different listener heights eg slouching down or lowering the chair.
Are you using digital EQ? Beware going too low and bottoming the drivers. High pass at 40Hz would be generous.
What drivers are they?
Any rocking at higher SPL?
Thanks! and yes desktop space has been liberated.
No EQ yet. Just built them over the weekend - haven't been able to listen to them much. From whatever I've heard they sound open and relaxed. And yes they sound pretty much same irrespective of how tall and farther away I sit from the desk.
Drivers are : Peerless by Tymphany TC Series TC8FD00 3″ Full Range Speaker 4 Ohm
I'm not expecting them to go low and I don't think they can go down to 40Hz . Planning few tweaks - will post the results here!
Well, Chris please read the following review of the Logitech speakers from 2009:
https://www.audioholics.com/computer-speaker-reviews/logitech-360-degree-speaker-systems
Clearly stated as dipole.
Jim
Jim,
Looks to me like the reviewer made a mistake. For starters, dipoles do not provide 360-degree sound. Further, the Z320 is a ported box, and there's no way a ported box would be effective with the drivers wired as dipoles.
Chris
Looks to me like the reviewer made a mistake. For starters, dipoles do not provide 360-degree sound. Further, the Z320 is a ported box, and there's no way a ported box would be effective with the drivers wired as dipoles.
Chris
Chris, the reviewer in my Post #24 reference states:
"The back of the driver is open making it a true dipole speaker. This is where Logitech is getting their "360 degree" claim. This will not only shoot sound forward but backwards reflecting the sound off the back wall."
I'm assuming that these speakers (Z320) have only a single driver in each enclosure. Thus open back means dipole radiation.
I agree that the 360 degrees claim by Logitech is not valid as figure 8 polar plots result.
Jim
"The back of the driver is open making it a true dipole speaker. This is where Logitech is getting their "360 degree" claim. This will not only shoot sound forward but backwards reflecting the sound off the back wall."
I'm assuming that these speakers (Z320) have only a single driver in each enclosure. Thus open back means dipole radiation.
I agree that the 360 degrees claim by Logitech is not valid as figure 8 polar plots result.
Jim
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The largest driver I have found at a decent price that could play nearly full range on a small open baffle with the right equalization is the SB poly 6 inch
Inductance is low, the cone is very light and not overdamped. On an 8 inch wide baffle it is capable of 93db at 141hz at x-max, and 83db at 100hz. If you cross to a sub, add 6db of spl capability at the crossover point. With the right EQ on the top end it can do a decent job of the whole show, and crossing it to a tweeter is not difficult. How often does anyone hit 90db with their desktop set up? Sober that is...
Inductance is low, the cone is very light and not overdamped. On an 8 inch wide baffle it is capable of 93db at 141hz at x-max, and 83db at 100hz. If you cross to a sub, add 6db of spl capability at the crossover point. With the right EQ on the top end it can do a decent job of the whole show, and crossing it to a tweeter is not difficult. How often does anyone hit 90db with their desktop set up? Sober that is...
Be careful under 100Hz not to do X damage:
It would be great to do a two way with bass module to unload bass excursions from the OB tower.
Putting a sealed sub under the desk is an old trick but its only good under 80Hz and even then is compromised.
OB bass on the desktop is going to be sonically the best fit with OB mids. A SLOB can do that without needed a wide baffle or woofer on the desk. For you a narrow SLOB tower right behind the OB array would be excellent. A SLOB (Slot Loaded Open Baffle) will do <200Hz really well and match the OB mids. A SLOB has higher dB projected forward in the near field when designed right. Perfect for desk top near field use.
For you the SLOB could be a narrow tower to match the array. Four 6" cheap drivers off set and stacked. About 4" x 18" front dimensions with slots at the sides firing bass either side of your OB tower.
What are the drivers? About how low to they go if there's nothing behind them for a few yards? Using any equalization? No tweeters? If they're doing the high frequencies are they projected rearward as well? Because that would be an interesting benefit if they did. Are there any midrange drivers that hit 150 hz and also do OK in the highs? I'm curious how it would be if there was a large baffle with open baffle speakers. Really wide. Like 3-4'. How would it help the bass?
@Clarity2022 my answers inline above in bold
I'm certainly planning to add subwoofer. I would love to do SLOB but initially will try a pair of cheap 6 inch sub drivers that I've with me with low pass filter.
When you are ready to slob plan it carefully. It seems tricky to get right but with good design:
Nelson Pass wrote:
They have a fairly deep bottom, and are very punchy in the sense that transient attacks come
at you with all the troops in formation, a nicely aligned shock wave. They are well behaved
with regard to mating with full-range speakers, and with the crossover presented you can run
both top and bottom in-phase, which makes for an improved sense of space and imaging
Jim,
Look at pictures of the Z320. There's clearly another driver on the back, as well as the bass reflex port. The reviewer doesn't know what they're talking about.
Chris
@bhpistorqintorpm,
Any updates?
Are you still using and happy with them?
What did you do about base?
How do the compare to your previous box speakers?
I’m interested in maybe build something like this with a SLOB.
Any updates?
Are you still using and happy with them?
What did you do about base?
How do the compare to your previous box speakers?
I’m interested in maybe build something like this with a SLOB.
not the one who got asked but i have built two passive cardioid 6" enclosures for a 2.1 system. I think 6" woofers with like 8mm xmax like Reckhorn D165 should have enough displacement for a "near field SLOB" to get decent bass. In a normal dipole or cardioid 100hz or maybe 80hz is possible at decent volume but with the slob gain it should work out.
Since your desk is out in the middle of the room, there‘s no real advantage to OB bass in such a nearfield situation
Linkwitz Pluto/lx mini is your friend here and almost the perfect solution.
Linkwitz Pluto/lx mini is your friend here and almost the perfect solution.
My desk is not in the middle of the room but against a wall. Thats why i switched from LX Minis to a cardioid (first ME Geithain clone, now like a kef r3 with cardioid woofer) and the differencein the lower midrange is noticeable. LX Minis are still great speakers but not against a wall.