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Passive high impedive filtering

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Posted on July 22, 2015 at 00:50:10
pix
Audiophile

Posts: 411
Location: sweden
Joined: March 18, 2006

Hi
I figure, since I use biamps for my Karlson K15 and 200Hx Tracstrix horns I might as well put the filtering in the high impedive postion before the power amps.

Is this a good or bad idea?



 

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RE: Passive high impedive filtering, posted on July 22, 2015 at 00:54:40
pix
Audiophile

Posts: 411
Location: sweden
Joined: March 18, 2006

This is how my system looks like
Now I plan to replace the integraded "SS-amp" with a Dynaco CSA-35 tupe-amp for the bass (Karlsson K-15/Beyma 15P80Fe) and a RE74 DHT pre-amp

 

RE: Passive high impedive filtering, posted on July 22, 2015 at 06:09:12
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
Seeing the cap after the 300b amp brings to mind a saying regarding active crossovers by the good Dr. Gizmo, "Doing it in the front is better than doing it in the rear." Now that's medical advice mind you.

Get you a Marchand analog active crossover. $500 for either a FET based active or a PPXLO. Having a two way makes the PPXLO an easy option for you.

Since you have the MiniDSP you probably played around with crossover points, but I would prefer 500hz over 600. I know your mid driver/horn can easily do it. I would even push it to 450hz just to try it.

You are doing great! Plenty of time to play with all this.


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Big speakers and little amps blew my mind!

 

RE: Passive high impedive filtering, posted on July 22, 2015 at 07:08:51
pix
Audiophile

Posts: 411
Location: sweden
Joined: March 18, 2006
Dr. Gizmo knew whats right

As for x-over points,
So far I hve ony tryed 350 and 600Hz (passive) high-pass x-over.
And by those two I prefered the 600Hz.
So far I have only used 1st order filtering (6dB/Oct), And my guess is that going to low will requre a higher order of filtering?

 

RE: Passive high impedive filtering, posted on July 22, 2015 at 08:22:08
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
He called a lot of things right a long time ago.

350hz is certainly too low for your mid driver, and first order only makes it worse. Gross distortion at moderately low volume I would think.

Hard to believe you've only tried two first order crossovers. Do you have the calibrated mic that goes with the minidsp? Considering you built your mid horn and your bass bin I would think it a necessity. You don't have to get fancy and take them outside. You can do it in the room. It will help to know if you need EQ.

Generally the lower you go the steeper the slope must be. It's always possible to figure in the acoustic roll off like you are doing. The Marchand I mentioned can go as high as a 48db eighth order slope. That's a crossover that's doing something.

You should be in a measuring mode right now. OTOH a 24db slope at 500hz would work fine as a start.

If you ever want a passive crossover, then I would say check out ALK's site first.


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Big speakers and little amps blew my mind!

 

RE: Passive high impedive filtering, posted on July 22, 2015 at 10:33:38
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
My ears do not like active crossovers with dissimilar amps over 100Hz. Even at 100Hz, I consider it dicey. YMMV, so listen for yourself. If you amps are identical, there crossover where every you want.

Dave

 

RE: Passive high impedive filtering, posted on July 27, 2015 at 08:40:53
bare
Audiophile

Posts: 1877
Joined: April 14, 2009
Dr Gizmo? rip.
Owning similar speakers to him. I find that Active gives little advantage to a well designed Passive .. in real life.
He liked to Talk :-)

 

RE: Passive high impedive filtering, posted on July 27, 2015 at 16:18:12
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
YMMV and all that, but a little advantage is more than none.

I'm sure you use a very low order slope, and yes passives excel at that. With multiple horns others might want the steeper slopes that are easier to do with an active. Don't take that too far. I have a passive that has something like a 110db slope, and with a flat impedence. It's about big enough to fill a car trunk. Yours is probably a two way, that makes a passive easier to do.

To me, slopes are all very specific to the speaker, and even to the listener. No one is right, and I go back and forth. Third and fourth order are my favorites. Now I'm talking too much!

>"He liked to Talk :-)"

People from NYC usually do. :)



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Big speakers and little amps blew my mind!

 

RE: Passive high impedive filtering, posted on July 29, 2015 at 18:23:51
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
It took a while for this to click. There is an inmate called Tre' who has almost the exact same set up as yours, but he puts the cap at the input of the tweeter amp, and not after it. You should try it. It's more like an active crossover. I say second order it if you are able.

Edit: The proper classification being; the cap before the amp is a low-level xover, and the cap after the amp is a high-level xover.

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Big speakers and little amps blew my mind!

 

RE: Passive high impedive filtering, posted on July 30, 2015 at 10:37:28
pix
Audiophile

Posts: 411
Location: sweden
Joined: March 18, 2006
Well, Now I have tryed miniDSP for low-level filtering in various x-over points and slopes, and none of those came close to the pressence I get with the high-level 1st order hi-pass filtering (bass falling of natuatelly)
I am not sure if itīs the miniDSP in itself killing the lifefullness of the music, or its higher order slopes. But the single cap filter is light years ahead in my ears.
The difference is most clear listening to high impact instruments (like piano) witch makes me think the key lay in less phase shifts.
I am fuly aware that lower high pass x-over point call for stepper filtering. But the best x-over point is also determand by the bass response, not the mid/tweeter horn alone. And I think the lowest possible hi-pass x-over point isīnt always the best, since this calls for higher order filtering, and thus more phase shifts.

 

RE: Passive high impedive filtering, posted on July 30, 2015 at 19:34:07
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
Oh I can understand the attraction of a one cap crossover. Can't get any more minimal than that. When done right, yes I'm sure it sounds great. I don't use my miniDSP for daily listening.

I understand your points about low order crossovers. The one bit of friendly advice I'd give is that acoustic horns / compression drivers almost always need more than a first order slope. Not always, but almost always. Second order usually does the trick. I'm no fan of letting the rolloff of the horn/comp driver form the majority of the high-pass acoustic crossover. Direct radiators are different. YMMV.

Like I said before, you have years to play around with it, and I know you will. :)



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Big speakers and little amps blew my mind!

 

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