X-over slope question - AVS Forum
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post #1 of 14 Old 01-16-2014, 10:15 AM - Thread Starter
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Hi All,

Got a question with regards to cross over slope choices.

I am planning on replacing my LCR speakers in the near future. I have been looking for several years now at speakers, but concentrating on a tower for the LR. I have two 15" Titanics which have been collecting dust for quite some time now. I recently thought about getting a 3cuft flat pack from DIYSG and making a bass module and getting the Atlantic Technologies 8200e speakers for it. I have a Denon AVR-4520CI and a Sherbourn PA-7 350 for power in the 11.2 channel setup.

I just need a very basic/simple 2-way active crossover. I wasn't sure how steep of a slope I should go for when crossing over the main to the bass module (24, 18 or 12dB per octave). I was looking at the Rolls SX45 since it is 12dB.

The bass module would be just that, a bass module. Sub duties will be handled by eight 18" drivers in an IB set up (4 along screen wall and 2 each in each rear corner of the room) powered by an LG Clone.

Thanks in advance!


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post #2 of 14 Old 01-16-2014, 07:01 PM - Thread Starter
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## DIY Rustic ConcreteBunker HT Build w/8 x 18" IB subs & 25KW ##

Denon AVR-4520 11.2 | Sony VPL-HW55ES | Elite Screens 11' screen | Sanway FP-14000 | Sherbourn PA 7-350 | Buttkicker BKA-1000(3x) | Behringer iNuke NU1000DSP | GR Research LS-9 + LS-C | 8x IB318's | Buttkicker Original(2x), LFE(2x), MiniLFE(8x) | MinDSP 2x4 | 21'W x 27'L x 10'H | MiniSplit
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post #3 of 14 Old 01-16-2014, 08:37 PM
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post #4 of 14 Old 01-18-2014, 06:56 AM - Thread Starter
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Actually, the standard I ran across on most active filters was 24dB slopes, not 12. Most all of the "simple" active crossovers from most of the players (Behringer , Ashly , Art, DBX, Peavy, BBE, Rane, Alto, Nady...) are 24dB slopes.

Thanks for the input though.

My question was not which slope is a standard, but which slope would be better for the filter between a bass module and speaker? A narrower slope (12dB) or a steeper slope (18, 24+) ?


## DIY Rustic ConcreteBunker HT Build w/8 x 18" IB subs & 25KW ##

Denon AVR-4520 11.2 | Sony VPL-HW55ES | Elite Screens 11' screen | Sanway FP-14000 | Sherbourn PA 7-350 | Buttkicker BKA-1000(3x) | Behringer iNuke NU1000DSP | GR Research LS-9 + LS-C | 8x IB318's | Buttkicker Original(2x), LFE(2x), MiniLFE(8x) | MinDSP 2x4 | 21'W x 27'L x 10'H | MiniSplit
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post #5 of 14 Old 01-18-2014, 07:00 AM
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My question was not which slope is a standard, but which slope would be better for the filter between a bass module and speaker? A narrower slope (12dB) or a steeper slope (18, 24+) ?
It's not that simple.
It involves acoustic integration and localization perception.
Bob McCarthy calls it a case of a tiger chasing it's tail.
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post #6 of 14 Old 01-18-2014, 07:17 AM
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Originally Posted by rms8 View Post

My question was not which slope is a standard, but which slope would be better for the filter between a bass module and speaker? A narrower slope (12dB) or a steeper slope (18, 24+) ?
Whatever works the best. That depends on the specific characteristics of the speakers and the room. 12dB is too little slope in most cases. 18dB is considered the minimum for a good result, and with digital filters you often see 48dB used. Deciding what's best is a matter of taking in-room measurements to see the result. That also applies to the high pass and low pass knee frequencies, which aren't necessarily the same. Very often you might low pass 10 to 20Hz below the high pass frequency to arrive at the best result, especially with lower order filters.

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post #7 of 14 Old 01-18-2014, 07:26 AM - Thread Starter
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Originally Posted by Bill Fitzmaurice View Post

Whatever works the best. That depends on the specific characteristics of the speakers and the room. 12dB is too little slope in most cases. 18dB is considered the minimum for a good result, and with digital filters you often see 48dB used. Deciding what's best is a matter of taking in-room measurements to see the result. That also applies to the high pass and low pass knee frequencies, which aren't necessarily the same. Very often you might low pass 10 to 20Hz below the high pass frequency to arrive at the best result, especially with lower order filters.

Thanks Bill !!

So it would be better to spend more $$$ on a filter with a variable slope vs. fixed so one can experiment with what sounds best. The price difference between those is pretty substantial though.


## DIY Rustic ConcreteBunker HT Build w/8 x 18" IB subs & 25KW ##

Denon AVR-4520 11.2 | Sony VPL-HW55ES | Elite Screens 11' screen | Sanway FP-14000 | Sherbourn PA 7-350 | Buttkicker BKA-1000(3x) | Behringer iNuke NU1000DSP | GR Research LS-9 + LS-C | 8x IB318's | Buttkicker Original(2x), LFE(2x), MiniLFE(8x) | MinDSP 2x4 | 21'W x 27'L x 10'H | MiniSplit
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post #8 of 14 Old 01-18-2014, 07:36 AM
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Just 1 of many options:
http://sound.westhost.com/project09.htm

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post #9 of 14 Old 01-18-2014, 07:47 AM
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Originally Posted by rms8 View Post

The price difference between those is pretty substantial though.
Not when the crossover is bundled in a DSP that allows you to do many other things as well, including EQ and delay.

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post #10 of 14 Old 01-18-2014, 08:06 AM - Thread Starter
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Originally Posted by WVSyd View Post

Just 1 of many options:
http://sound.westhost.com/project09.htm

That's really nice! I would love to go the DIY route (EE is my prefession), but time is not my friend at the moment; hence why I've been looking for a simple 2way active crossover. I definitely bookmarked that PCB though for future reference, in case time wants to play nice!

THANKS for the link!


## DIY Rustic ConcreteBunker HT Build w/8 x 18" IB subs & 25KW ##

Denon AVR-4520 11.2 | Sony VPL-HW55ES | Elite Screens 11' screen | Sanway FP-14000 | Sherbourn PA 7-350 | Buttkicker BKA-1000(3x) | Behringer iNuke NU1000DSP | GR Research LS-9 + LS-C | 8x IB318's | Buttkicker Original(2x), LFE(2x), MiniLFE(8x) | MinDSP 2x4 | 21'W x 27'L x 10'H | MiniSplit
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post #11 of 14 Old 01-18-2014, 08:12 AM - Thread Starter
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Originally Posted by Bill Fitzmaurice View Post

Not when the crossover is bundled in a DSP that allows you to do many other things as well, including EQ and delay.

I considered some of the DSP models out there, but wanted to keep it simple since it is a basic bass module with the main speaker sitting right on top, thereby negating a real need for a delay feature. The EQ would be really nice too, but for now I would just let the Audyssey MultEQ XT32 on the 4520 handle those chores. I also have an AntiMode too.

Thanks for all the advice thus far, it's causing me to rethink a bit of what I want to accomplish in the beginning stages.


## DIY Rustic ConcreteBunker HT Build w/8 x 18" IB subs & 25KW ##

Denon AVR-4520 11.2 | Sony VPL-HW55ES | Elite Screens 11' screen | Sanway FP-14000 | Sherbourn PA 7-350 | Buttkicker BKA-1000(3x) | Behringer iNuke NU1000DSP | GR Research LS-9 + LS-C | 8x IB318's | Buttkicker Original(2x), LFE(2x), MiniLFE(8x) | MinDSP 2x4 | 21'W x 27'L x 10'H | MiniSplit
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post #12 of 14 Old 01-18-2014, 08:28 AM
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Originally Posted by rms8 View Post

That's really nice! I would love to go the DIY route (EE is my prefession), but time is not my friend at the moment; hence why I've been looking for a simple 2way active crossover. I definitely bookmarked that PCB though for future reference, in case time wants to play nice!

THANKS for the link!

You're quite welcome.
I studied active filter design in the 70's and Walt Jung's book.
Active crossover circuit boards have been around for the hobbyist since the 70's ( I built filters around the Old Colony Sound WMJ board ).
What you will find is that even if one has the fabrication ability, it is often cheaper to buy a commercial offering.
They have the advantage of cost reduction due to scale - a DIYer often has to find parts from numerous sources without the quantity advantage of volume purchasing.
In my case - It was certainly easier and cheaper to buy than build an active crossover.
The best commercial products are not cheap; some cheap brands have poor Q.C. and utilize cheap mechanical parts to cut costs that cause later problems.

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post #13 of 14 Old 01-18-2014, 08:54 AM - Thread Starter
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Originally Posted by WVSyd View Post

You're quite welcome.
I studied active filter design in the 70's and Walt Jung's book.
Active crossover circuit boards have been around for the hobbyist since the 70's ( I built filters around the Old Colony Sound WMJ board ).
What you will find is that even if one has the fabrication ability, it is often cheaper to buy a commercial offering.
They have the advantage of cost reduction due to scale - a DIYer often has to find parts from numerous sources without the quantity advantage of volume purchasing.
In my case - It was certainly easier and cheaper to buy than build an active crossover.
The best commercial products are not cheap; some cheap brands have poor Q.C. and utilize cheap mechanical parts to cut costs that cause later problems.

Yeah, I know too well about trying to source parts for a DIY build....I built a 500w/chnl amp some time back (early 90's?). I ended up using two cabinets with an umbilical between them. One for the power supply, the other for the amp. I remember each of the 4 caps being the size of a soda can and the transformer weighing nearly 10-15lbs! It simply took up way too much real-estate and was replaced a few years later. Not to mention the transformer had a noticeable buzz which resonated in that cabinet. The build was definitely fun and challenging, but today's market makes those builds too expensive.


## DIY Rustic ConcreteBunker HT Build w/8 x 18" IB subs & 25KW ##

Denon AVR-4520 11.2 | Sony VPL-HW55ES | Elite Screens 11' screen | Sanway FP-14000 | Sherbourn PA 7-350 | Buttkicker BKA-1000(3x) | Behringer iNuke NU1000DSP | GR Research LS-9 + LS-C | 8x IB318's | Buttkicker Original(2x), LFE(2x), MiniLFE(8x) | MinDSP 2x4 | 21'W x 27'L x 10'H | MiniSplit
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post #14 of 14 Old 01-18-2014, 09:03 AM
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Definitely:
Even the quality of available kits can vary.
Some amp kits in the 70's were based upon designs that had stability issues.

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