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Old 7th July 2013, 03:42 AM   #11
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Quote:
Originally Posted by Greebster View Post
jacozz,

There are two things I see that stand out is your choice of crossover point. The B200 should be lower, say 1700-1800Hz based on the polar plots I've seen.

....
Can we assume you have real world tests and not mfgr specs?

Here is the Visaton website on the B200 -

B 200 - 6 Ohm

Here is their frequency plot, it does not look quite as extreme as yours -

http://www.visaton.com/bilder/freque.../b200_6_fs.gif

Just passing it along.

Steve/bluewizard
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Old 7th July 2013, 04:15 AM   #12
Pano is offline Pano  United States
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A great question - with a complicated answer. I have to tune from the listening position, nothing else works as well for me. That can include x-over points, levels and EQ.

One big complication you've got going is the open baffle. Open baffle crossovers are not like box crossovers - because the drivers don't behave in the same way. You have to take into account the rising response of the woofers caused by the wrap around cancellation. Usually a lower than normal 1st order (or staggered 2nd order) can make up for the cancellation and bring the woofers back to flat.

If you are using a large midrange cone and crossing low, it too, may have a rising response that you need to take into account.

Bottom line: Plugging typical box crossovers into Open Baffle usually sounds bad. You need to think "Outside the Box."
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Old 7th July 2013, 11:51 PM   #13
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Gotcha Pano,
Inductor brings the rising response flat followed by a first order @1k.
Forgot about that

OB cross would be closer to say -3dB @ 30-45 degrees (something like that ... I'm clearing out cobwebs here)
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Old 8th July 2013, 08:54 AM   #14
jacozz is offline jacozz  Sweden
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Blue Wizard wrote:
Quote:
WAIT! - I just realized something, you said 18uF COIL. Is that a Typo? Is that 18uF Capacitor?
Yes thats a typo, it's a capacitor...
The reason I chose to cross as low as 1 kz on the B200, is to combat the rising response between 1-2,5. So in practice, the crossover point is more like 2,5k.
But the Hivi Tweeter has a in line f-mod crossover point around 2,5k + a 18 uF capacitor for protection. So...

My computer is sadly on service, but I try to upload some measurements when I get her back
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Old 8th July 2013, 10:06 AM   #15
AllenB is offline AllenB  Australia
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It could have been worse, I normally follow up such thoughts with "OMG, I just changed those output transistors"
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Old 8th July 2013, 03:47 PM   #16
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Quote:
Originally Posted by Pano View Post
A great question - with a complicated answer. I have to tune from the listening position, nothing else works as well for me. That can include x-over points, levels and EQ.

One big complication you've got going is the open baffle. Open baffle crossovers are not like box crossovers - because the drivers don't behave in the same way. You have to take into account the rising response of the woofers caused by the wrap around cancellation. Usually a lower than normal 1st order (or staggered 2nd order) can make up for the cancellation and bring the woofers back to flat.

If you are using a large midrange cone and crossing low, it too, may have a rising response that you need to take into account.

Bottom line: Plugging typical box crossovers into Open Baffle usually sounds bad. You need to think "Outside the Box."
hi pano
what EQ do you use?
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Old 25th July 2013, 08:47 PM   #17
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Quote:
Originally Posted by jacozz View Post
Blue Wizard wrote:


Yes thats a typo, it's a capacitor...
The reason I chose to cross as low as 1 kz on the B200, is to combat the rising response between 1-2,5. So in practice, the crossover point is more like 2,5k.
But the Hivi Tweeter has a in line f-mod crossover point around 2,5k + a 18 uF capacitor for protection. So...

My computer is sadly on service, but I try to upload some measurements when I get her back
Quoting myself -

"The FMOD passes everything above 2.5khz from the amp to the tweeter, which mean nothing between 1100hz and 2.5khz reaches the coil on the tweeter. You seem to have a gap in your frequency response. "

I've yet to see anyone correct or dispute this statement. You have a gap in your frequency response between 1100hz and 2.5khz.

Care to explain how my statement is wrong?

Repeating my point -

----[FMOD 1.0khz]----[T-Amp]----[6 ohms B200 Mid]
----[FMOD 2.5Khz]----[T-Amp]----[18uF (1100hz]----[8 ohm tweeter]

One assumes the FMOD 1.0khz is a LOW PASS.

One assumes the FMOD 2.5khz is a HIGH PASS.

Were are the frequencies between 1khz and 2.5khz?

I think I understand the 18uf better now. That is a failsafe and is intentionally below the working range so as to have no effect.

But how do a 1khz Low Pass combined with a 2.5khz High Pass, not create a gap between 1khz and 2.5khz?

I assumed if I made such a bold statement and was wrong, people would jump in and correct me. Yet no one has.

So, how about people address this so we can put it behind us -

FMOD 1.0khz is a LOW PASS.

FMOD 2.5khz is a HIGH PASS.

Creates a GAP between 1khz and 2.5khz.


Steve/bluewizard
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Old 26th July 2013, 03:20 AM   #18
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I'll attempt

Quote:
Originally Posted by jacozz View Post
Real world acoustical crossover points between mid and tweeter:
about 2500 Hz with a true 6 db slope one the midrange driver, but the planar tweeter measure more like 12 db slope from 2k downwards...
Look at the response I posted. Notice there is a ~5+dB rise from 1k to 2.2k. Ignor the dips, this won't be heard when listened to with music, but the peaks will be. So one octave up the FMOD has only attenuated the signal level by ~6dB by the time the tweeter is brought onto the scene. Here @ 2.5k we have another second order filter, high pass. Now is where I would like to point to the tweeters FR but lets skip that for the time being. Tweeters normally roll off at a 12dB per octave rate and are at least crossed at an octave above their natural resonance. When adding a 2nd order network above the natural rolloff of the tweeter will result in a 12dB slope until the natural rolloff where it increases to a 4th order network. So when the two are combined, there would only be a dip in the responce @~ 1600-1700 of (off the top of my head) ~31dB. Hardly an issue, really, could be better but unless you personally modify the FMODs your stuck.
Quote:
It's sounds really great and they measure pretty flat., except, compared to my fullrange drivers, the vocal is somewhat confused, and somewhat distant. Maybe that is the trade of with multiple drivers in the critical frequency range, or it's take some woodoo work to get that coherence that I hear with my full range drivers work in a 2-way?
From here we hear his description of the problem.
This is in the critical range of hearing and where full range drivers excel. The issue here is due to slightly mismatch crossover points, but more significantly the electrical phase is off. If these are not in phase @ the crossover point a disconjointed sound results.
I don't know if these are LR passive crosses or not, but would guess not. That would help with the phase issue, which when I design a crossover won't stop unless I can get good phase tracking of at least 1 octave @ crossover point. The biggest issue here is the choice in using FMODs for the crossovers.
Personally I'd slap a miniDSP on it. Infinitely more flexible than FMODs and now two MiniDSP's 2x4's can be had for $160. I wouldn't bat an eye for a second and be done with it, well that is after many hours of further listening/tweaking and after the drivers are physically time aligned. I'll add that I don't run to the miniDSP, everything is done passive first and then if that can be done with the miniDSP then I'll go for it. Seriously cheaper when prototyping speakers.

Last edited by Greebster; 26th July 2013 at 03:24 AM. Reason: tweak
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Old 26th July 2013, 03:27 AM   #19
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Additionally the baffle width comes into play here and I would think it smart to have it at the crossover point, not wider and not narrower, equal to.
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Old 26th July 2013, 11:39 AM   #20
AllenB is offline AllenB  Australia
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Interesting. I'm not sure it would make much difference.
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