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Multi-Way Conventional loudspeakers with crossovers

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Old 21st October 2011, 07:05 PM   #481
Pano is online now Pano  United States
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Quote:
Originally Posted by FOXYE View Post
What C1 cap affects ? bigger value will give less/more treble?
Bigger gives more midrange from the Vifa. It won't affect the treble. The bigger the cap, the lower the Vifa plays. It is now set to blend well with the Peerless 12". You should start with 5.7-6.2uF and listen to how it sounds. 6uF will be best for most rooms.
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Old 21st October 2011, 07:48 PM   #482
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Default Stands and Legs

It's funny how everyone wants to make a floor stander out of this. I understand, so did I! But it's better with the short baffle up off the floor.

So here's an idea: Why not give it legs?
Since you need to build a 2x2" subframe anyway, you could extend that frame down the the floor. The two 2x2 sticks that run the vertical length behind the baffle, just make them long enough to reach the floor. Those become the front legs.

At the floor run another stick of 2x2 directly backward on the floor from behind each leg. Go back 15-24". Those are the feet. From the back of the feet, run a diagonal stick up to the baffle on each side. Voila! Stand, frame and feet all in one. From the side it would look like a triangle.

The shelf can go at the bottom of the baffle as per normal, or down on the floor. EZ to do, no stand needed and the baffle floats free, as designed. You could even use 2x4" lumber if you wanted the stand to be heavy and solid.

Do I need to draw a picture?
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Old 21st October 2011, 08:10 PM   #483
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Default High Pass cap value

An additional thing to keep in mind is that we have to be careful not to have too much cap as it could extend the low end far enough down toward the Vifa's 110 Hz resonance to cause excursion troubles. Even with the 6 MFD, there is still quite a bit of energy delivered at resonance. Much more capacitance could result in over excursion and driver damage issues. Not to mention an unwanted bump in the frequency response.
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Old 22nd October 2011, 04:11 PM   #484
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Thanks for the information,

What cuts should be done for the units?
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Old 22nd October 2011, 04:35 PM   #485
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Default More crossover thoughts

OK, I will be adding a few comments concerning the crossover. Will need to break this up, so just dealing with C1 in this post. The info below assumes a Pad resistor (R2) between 4 and 4.5 ohms.

Using Pano's pretty crossover schematic as a reference, (thanks again Pano) I want to look at the current C1 value and where one may want to experiment.
Click the image to open in full size.

Keep in mind, the current set up is MY personal preference in My listen room. The main goals were to find a simple layout that provided the best combination of low parts count, tonal balance, power response, musical qualities and long term listen-ability. As with all designs there is room for improvement.

The High pass cap C1 helps to set the low end roll off and partially determines the roll off rate. The best I can measure (combo of RT3 and ARTA) the 6 Mfd provides a 3rd order net acoustic shape with the roll off starting at about 600 Hz and is 18 db down at around 150 Hz. The calculated 1st order electrical predicts a - 3 db at around 1,350 Hz and we should be somewhere around -18 to minus 21 db around 150 Hz. So what is happening is the roll off is delayed by well over an octave, but once it starts it is much steeper than theoretical. What we are seeing is a combination of electrical, baffle (OB F Peak & F = factors) and driver induced roll off forces combining to form a 3rd order acoustic response. So much for depending on electrical only factor(s). I will forward a couple of RT3 files to Pano so he can post them. A picture really demonstrates what is going on.

BTW, the data was taken with the Vifa at 44" off a carpeted floor at a microphone distance of 8'. (On axis) The wall behind the speaker is standard sheet rock and the speaker has about a 10 degree toe in toward the center and is 43 " from baffle face to rear wall. Large room, 21' X 26' X 8' with a lot of furniture and such.

As for playing with the 6 Mfd. To be honest, this value was selected by ear and experience. A smaller room could possibly benefit from a smaller value, say between 5 and 5.8 MFD. But for most I think the 6 Mfd will prove to be the best compromise.

Will talk about the Vifa Pad and trap in the next post.
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Old 22nd October 2011, 06:36 PM   #486
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Here are two RTA graphs that John took of the Manzanita in his room at 8 feet away. We have full speaker and also just the Vifa with crossover.
Attached Images
File Type: png Manzie-RTA.png (8.5 KB, 1651 views)
File Type: png Vifa-RTA.png (9.9 KB, 1632 views)
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Old 23rd October 2011, 01:18 PM   #487
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Pano or John

Would there be any advantage to using a lower dcr 2mh inductor on the trap? I recall Seas recommending a low dcr inductor for the suggested trap on one of their 8" full rangers. Costs $19 instead of $10..............
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Old 23rd October 2011, 03:19 PM   #488
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Default Trap inductor

The current design (as in my personal pair) uses a Solen 14 ga. perfect lay which measures about .3 ohm.

Basically if you stay at or below .5 ohm ( 15 ga wire or 16 ga. foil air core) there will be little problem with the trap working as intended. I would avoid iron core inductors for this part of the circuit. Not a lot of price difference and the lower DCR is not needed.
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Old 23rd October 2011, 03:29 PM   #489
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Default Peerless and Vifa Cut out diameters

Cut out dimensions can be found at the Madisound or PE web sites. Just for S & G's, the Peerless cut out is 275 MM (10.83" diameter) and the Vifa cut out is 78 MM (3.07"). I add a MM or two on the Peerless and a MM on the Vifa for a touch of wiggle room! Best thing to do of course is once you have the drivers, measure and verify BEFORE you do your cut outs!
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Old 23rd October 2011, 03:48 PM   #490
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Thanks John.

And don't forget the larger cutout/countersink in the back for the Vifa. It needs to breath.
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