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Vituixcad2

#43
Foz said:
Maybe you cab/port tuning is off???
Click to expand...

Remember I have not measured this cab in any way shape or form, but what I do know, is this woofer likes a cab of right around 2.9 c.f. and tuning of 46 Hz. If the cab is any bigger, excursion power handling drops off quickly. Any higher tuning and the cab becomes a one note wonder.

I did the dancing rice test. Definitely 46 Hz.

My goals are:
  1. Get rid of the 4 db gank spike this woofer produces between 1100 and 2300Hz. Cause it sounds horrible.
  2. Improve dispersion by adding a midrange. Cause these woofers beam like crazy.
  3. Model a crossover that works with these drivers. Cause they are what I have
  4. Build the crossover, assemble the cab and test. Cause you can't test something that's not built.
  5. Fine tune and produce a workable solution. Cause it can always be better.
 
#45
agedhorse said:
That woofer doesn't beam like crazy, another model deviation from reality.
Click to expand...

I'm not trying to be argumentative, but the guys in my kid's band call the space directly in front of the cab the valley of death.

I also took some video of a couple of live shows with a zoom q8 and there's a huge increase in volume right in front of the cab. sweeping from one side of the stage to the other. It's very, very noticeable.

This is modeling the 3015 by itself: 3015polar.png

Which also indicates beaming. Starting at about 1k at 30 degrees off axis you see -3db and by 3k it's -24db. 0 db all the way up the gut to 4k.

Once the midrange is added and crossed over, same angle, there's -3 db from 1k to 3k. So this is better.
 
#47
Doufuss said:
Calling @Foz @Passinwind
Click to expand...

Just wanted to check in briefly and expain my absence. I'm a week and a half out from NAMM and still waiting on other people to build stuff so I can add my thing to their thing and we can all go to Disneyland. And I'm slacking about equally successfully myself!
Yel_wink.gif


But I would like to offer up one suggestion: I've learned a ton from biamping with a digital crossover appliance before I ever make any solder smoke. It may not give you all the right anwers for your passive solution, but it will surely show you some blind alleys to avoid.
 
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#48
Doufuss said:
I'm not trying to be argumentative, but the guys in my kid's band call the space directly in front of the cab the valley of death.

I also took some video of a couple of live shows with a zoom q8 and there's a huge increase in volume right in front of the cab. sweeping from one side of the stage to the other. It's very, very noticeable.

This is modeling the 3015 by itself: View attachment 3653365

Which also indicates beaming. Starting at about 1k at 30 degrees off axis you see -3db and by 3k it's -24db. 0 db all the way up the gut to 4k.

Once the midrange is added and crossed over, same angle, there's -3 db from 1k to 3k. So this is better.
Click to expand...
Your reality doesn't match reality's reality, I think you have errors in your measurement including possibly boundary contributions, or possibly saturation of the measurement on axis.

I'm suggesting this from 40 years of doing this professionally, including about 20 years in the pro audio industry. I learned very quickly to double-check the measurements when the data doesn't match what reality should be based on experience.
 
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#50
agedhorse said:
Your reality doesn't match reality's reality, I think you have errors in your measurement including possibly boundary contributions, or possibly saturation of the measurement on axis.

I'm suggesting this from 40 years of doing this professionally, including about 20 years in the pro audio industry. I learned very quickly to double-check the measurements when the data doesn't match what reality should be based on experience.
Click to expand...

Alright. Lots to chew on here.
 
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#51
I looked at some of my polar data (can't share) and it's nothing like what you are seeing. I suspect that there are assumptions being made in the software that deviate from real world conditions.

As an aside, IF the polars were accurate, many of the current bass cabinets would be essentially unusable.
 
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#52
There is definitely something funny with the impedance plots.

I received the frd and zma files directly from Eminence (These graphs are not in this post) and using these, I ran simulations in PCD by Jeff Bagby, XSIM by Bill Waslo and Vituixcad2 by Kimmo Saunisto.

PCD and XSIM calculate much higher impedances from the same data, using the same values in the crossover.

Hmmm...
 
#53
Update on this thread.
V4XO.png Crossover
V4FR.png Frequency response and driver filters
V4IMP.png Impedance
V4PPWR.png Power dissipation

A very simple 2 way 2nd order crossover. Driving the cab with 30v (100W RMS) will generate approximately 120db at low frequencies and 116db at the top end, 4300 Hz. The alpha will be maxed out here but will only see 51 watts through the crossover.

This is a sim but I used my DATS to measure both drivers in cab to get the impedance right. My minimum impedances left to right are 7 ohms at 43 Hz, 6.4 ohms at 140 Hz, and 6.4 ohms at 1700 Hz.

I have to buy one item - a 3 mh inductor.
 
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#56
I wound up not buying a new inductor. Instead, I got some magnet wire of the same gauge, and added a little (around 4 meters) to the inductor I have. I used a calculator from the internet to guesstimate how much wire to use.

I scraped the insulation off both ends of the magnet wire about a 1/4" back, soldered them together and slipped a piece of shrink over the joint. Then, wound her up. (this is harder than it looks) I overwound it a little and kept taking loops off, while measuring, until I got my value. I used a couple dabs of clear nail polish to glue the winds in place, then reused the cloth tape Erse supplied.

Here we have the measured cab. Impedance at @ 1700 Hz is lower than the model at 6 ohms, but is the same as modeled at 144 Hz, 6.4 ohms. I measured the inductor which was supplied by Erse using dats, and of course it was right on the money. Then after the modification, measured again. This dats tool is going to be useful.

15.6v4dats.png
inductor test erse 1.8mh.png
inductor test rewind.png

It sounds really good. Very smooth and neutral. The Mesa D800 + seems to like the load, as it gets very loud with all knobs at noon and master at 11 o'clock.

Now, I need some gear to measure frequency responses.
 

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