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Multi-Way Conventional loudspeakers with crossovers

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Old 19th February 2009, 12:03 AM   #61
jonjin is offline jonjin  United Kingdom
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No worries Mark. I'm always fascinated about the theory and continuously learning. I'm actually chuffed to bits with the Onken bass (using lambswool)... do feel free to pop down...

I'm still busy messing around with my Behringer... such a great toy but I think I'll need a better mic... fun and games... fun and games...

JJ
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Old 20th February 2009, 12:35 AM   #62
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IslandPink, yes, the Supravox/Jensen pix are exactly what I was thinking of. The choice of damping material makes a big, big difference to the sound. In the "Beyond the Ariel" thread, I was surprised to see recommendations for pearlite (available at garden-supply stores) and activated charcoal (dunno where you get that). I think feather pillows are worth exploring as well.

It may sound like wacko speculation, but I suspect some of the bass-reflex sound is due to the small point-source vents having a suboptimal coupling to the room. I tried the Ariel with a rear vent halfway up the enclosure and there was no bass at all - well, not really, but it was thin and uneven-sounding. The speaker was also very fiddly about room locations, too. Moving the vent to the floor made a big difference in subjective and measured smoothness of the bass. I really think the distributed vents of the Onken are a big part of the bass quality.
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Old 21st February 2009, 12:26 AM   #63
Pano is offline Pano  United States
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Quote:
Originally posted by Lynn Olson
Vent locations matter, although this doesn't show up in the simulations.
I thought this worth pursuing, to see if my CARA software would simulate a different vent position (it should).

And it does! See image below for an idea of the room and speakers. You will see the dual woofer floor-standers. The left speaker has the vent near the bottom on the front, the right has the vent on the back near the top (you can't see it).

In simulations of the room, there is a noticable difference at many frequencies. I can post captures of the sims, if anyone cares to see them.

So maybe this distributed port thing is what is going on. Very interesting.......
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File Type: gif bass-room-sim1.gif (47.3 KB, 1033 views)
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Old 21st February 2009, 12:59 AM   #64
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I'd like to see it. Port locations matter more than people think, especially considering the narrow spectral output of the ports in most vented-speaker alignments. You have a one-octave emitter driving the room with what amounts to a point source (relative to the wavelengths involved).
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Old 21st February 2009, 01:01 AM   #65
Pano is offline Pano  United States
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OK Lynn - I'll put together some graphs later today.
(back to soldering, now)
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Old 22nd February 2009, 02:00 PM   #66
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jonjin,
Nice project.
I also have ah425 and gpa CD.
I think that horn sounds really good but I am newbie and give them to mr.Lampizator, to check it.
http://www.lampizator.eu/
(He live 180km from me)


Best
C
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Old 23rd February 2009, 01:16 AM   #67
Pano is offline Pano  United States
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I did the port position simulations - that ws the easy part. Getting them into a format that was meaningful and web friendly was not!

So I settled for 2 strips of graphs that show the SPL at 28 different frequencies from 18 to 160 Hz. The 2 different port postions are shown side by side. The speakers with the port on the bottom is shown on the left - speaker with the port on the top rear is shown on right.

The speakers were placed in what the CARA software found to be the best postion in this room given the restrictions of eqaul distance from back and side walls and pointing at the listener. Both sims (hi & lo ports) have the speakers in the same place.

Here is strip 1.

edit: The speakers are under the blue pins. Listener under the yellow pin.

(you can see both together and larger here
http://www.dactransformations.com/ports/
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File Type: jpg port-strip1.jpg (95.7 KB, 968 views)
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Old 23rd February 2009, 01:19 AM   #68
Pano is offline Pano  United States
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and the second half of the series is below.

These look like wasves in the roon, but they are not. It's just a 3D view of sound levels at a given frequency. It could be done in 2D, but the 3D is more dramatic.

You can see the the bass levels are higher at a number of frequencies with the low ports (more red).

Other than that, draw your own conclusions.

(you can see both together and larger here)
http://www.dactransformations.com/ports/
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File Type: jpg port-strip2.jpg (94.8 KB, 931 views)
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Old 23rd February 2009, 01:22 AM   #69
Pano is offline Pano  United States
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Here is the spl graph for the drivers and port that CARA used to calculate to SPLs in the room. Port is 70mm round.

The room is a bit too live in the low end, it would be boomy. CARA simulated 5 reflections for each ray, the default amount.
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Old 23rd February 2009, 01:25 AM   #70
Pano is offline Pano  United States
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And finally this is the end of the room with the speakers.
Shown are the low port version. Speakers are 80cm tall.

High port version is the same, but port is in on the back behind the tweeter.


Next step is to build a simulated Onken box and compare it to a normal BR box of the same size and shape.

Hope you enjoy the pretty pictures.
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File Type: jpg speaker-room.jpg (21.8 KB, 912 views)
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