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Old 21st September 2013, 10:38 PM   #111
Greggo is offline Greggo  United States
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Ahhh.... got it. Thank you. I am just starting to read up on the possibility of a DIY digital active studio monitor and was under the impression that a digital crossover could essentially replace any slope/eq/voicing/contour circuit that one would do passively, but I guess that is not yet the case.
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Old 22nd September 2013, 01:09 AM   #112
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Quote:
Originally Posted by Greggo View Post
Doesn't the crossover slope in MiniDSP negate the need to put a cap on the tweeter?
The cap is starting at the top of where the wave guide is lifting the low end. Thats not at your cross over freq but rather up near 5000 to 6000hz. The cap gets you back to flat around 1700 to 2000 and then the mini DSP is doing the cross.

Here you see the wave guide starts the lift at around 6000. The cap gets it back to flat. You arent using the minidsp from 6000,; its not the cross over frequency. You also need a cap for DC protection.

This is the Seas 27-TDFC bare response
Click the image to open in full size.

This is the lift with a small 6" wave guide (I used a 8" wide for the XT25 = more low end lift)
Click the image to open in full size.

Last edited by SpinMonster; 22nd September 2013 at 01:12 AM.
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Old 22nd September 2013, 11:51 AM   #113
Juhazi is offline Juhazi  Finland
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Greggo, minidsp is not just a digital xo device. It gives many possibilites to do frequency response corrections in many ways. Each output channel can hava 5 different eq settings with different parameters. Also delay and polarity inverting is possible. These and xo are adjusted indpendently. In addition each input channel can have 5 eq settings too, mainly for room correction use.

However, it can't give protection to the tweeter if the low/high level signal (hum, noise, click) comes after minidsp (it's output - power amp-speaker lines being mishandled, and that happens easily!)
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Old 22nd September 2013, 01:05 PM   #114
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As you already said, the cap is protecting the direct interface to an amp. Little caps starting at 6000hz are far cheaper than bigger caps starting down lower in freq, so why not just use the smaller cap?

Keep in mind for those using active crosses that every EQ adjustment uses up memory and lowers resolution such as on the DCX2496.

The tweeter is at an acoustic 2nd order with just a cap and it is aligned with the midbass because the wave guide moves it deeper into the cabinet. This eliminates the need to slant the baffle for 2nd order crosses.

Last edited by SpinMonster; 22nd September 2013 at 01:21 PM.
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Old 25th September 2013, 12:05 PM   #115
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Instead of installing a cap, and after taking another look at the super-simple crossover in the Zaph Audio waveguide speaker, I dialed in similar crossover points into the minidsp.
I wound up with 10kHz first order on the tweeter and 1400Hz first order on the woofer. I added a -8db low shelf at 1kHz to the tweeter to reduce output at the resonance frequency further. Woofer is dialed down 4db, and a little EQ introduced to reduce room anomalies. Very smooth yet dynamic. I'll continue to evaluate and play.
Peter
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Old 25th September 2013, 06:08 PM   #116
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Why would you use such a limited slope if you are active? Using the shelf from 10K and then a 4th order electrical at 1900 would increase power handling and lower distortion far more than the passive values Zaph used to keep it simple. What Zaph built wasn't optimum. Its was value and simplicity motivated. Neither is a constraint in active systems.
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Old 25th November 2013, 04:14 PM   #117
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Default Waveguide fun

Spinmonster...
I have been playing with the waveguides and built a TMM with 6.6" Nomex woofers, since the Vifa 8" woofers are now back in my heavily modified ported Centaurs. The Apogees are firmly entrenched in my main music system and are now a huge improvement over the originals. However, the continuing lure of DIY is hard to resist - here is a picture of the TMM set up. I took your advice and wound up with a 8.2uf cap on the tweeter and added a 4.7ohm resistor to bring the level down. The woofers have a .68mH inductance on both, and a 2.9mH on the lower woofer. The result is not the smoothest speaker I have heard, but certainly the most lively. Reminds me of my Royd Heralds but with more weight and better dispersion. Should be a good match for my F5 clone - not tried yet.

Peter
PS - the cat is quite taken with the Centaurs, too
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Old 26th November 2013, 01:23 AM   #118
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Go active and it will open up a new world. You are missing out on ultra low distortion coupled with amazing transients. You will be able to have 4th order slopes which will remove the tweeter strain.
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Old 28th February 2014, 11:01 PM   #119
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It's been a very busy diy winter for me. I picked up a pair of Infinity 8 Kappas at the local thrift shop for $50 and found some decent 11 ply oak faced plywood at Lowes.
I knocked together a couple of 1 cu ft cabinets from the ply and mounted the waveguides and Peerless 6.5" Nomex mid/woofers in an mtm configuration. Using the minidsp and a 8.2mfd cap on the tweeter, these provide a stunning clarity to voice, piano guitar etc. My "sweet spot" Apogees have been in the closet for the past three months.
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