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Old 6th February 2013, 06:20 PM   #1
Jaydog is offline Jaydog  Canada
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Default Do FR speaker builds require a High Pass XO?

Hi everyone,

I'm a noob. Was thinking about making a couple Bose-esque style of speaker with 4-6 drivers each one (thinking Mark Audio CHP-70's) to run with my NAD-C326BEE stereo amp. When I run Jeff Bagby's woofer cabinet design software, the excursion shown for a single woofer in a vented box goes above the X-Max below 40Hz or so in many configurations with only modest amounts of Wattage input. (Assuming I didn't mis-input something)
Is it common to put a high pass filter (40-45Hz) on FR speakers to limit the excursion on the deep low end such as is shown on those graphs? Explanation for this would be appreciated!

Thanks, Jeff Miller
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Old 6th February 2013, 06:47 PM   #2
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Hey Jeff,

Where are you from

It's normal what you're seeing in your box simulation. You plan to use 4+ drivers, so that's help reduce excursion a lot. That does raise some eyebrows though, why so many drivers?

As for the high pass, most people do not high pass. Depending on the type of music you listen to, not much content below 40hz. If you like to play loud and your music type does have bass that low then I'd consider a high pass.
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Old 6th February 2013, 07:45 PM   #3
Jaydog is offline Jaydog  Canada
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Thanks Tuxedocivic. Any recommendations for a crossover in that low range then? Or ideas where to look? I could use a crossover calculator and buy the necessary circuit parts; just have no experience with this.

I'm in Edmonton, Alberta, Canada. I like more drivers so I can handle more power, and I think it looks cool . My NAD amp is 50W/channel RMS, 100W/channel dynamic, and I have very limited control at low volume due to the crude volume control motor. I like that the speaker could suck up wattage, and I won't worry about cranking it either, once the speakers are broken in. I have a pair of FR125S from Creative Sound Solutions - they're great, but they can't handle enough juice for that amp to be able to turn up the volume.

I also want to use just the smaller drivers to get decent bass, mid, and treble because I think that's cool too, and I don't care much about deep thundering bass anyways. I can always add a sub one day if I change my mind.
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Old 6th February 2013, 08:01 PM   #4
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For a 40hz high pass, I'd go active. You'll need to find out how to do it, but it'll involve adding some parts between your preamp (source, computer, avr) and your amplifier. If you NAD is integrated, this might be trickier unless you only have one source. You basically need to block any <40hz content from reaching your amp.

Doing it between your amp and the speakers is way more expensive and difficult to do.

Before you go and spend money and time on 4+ drivers per cab, google "comb filtering". There's some fundamental issues with your plan.
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Old 6th February 2013, 08:18 PM   #5
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Quote:
Originally Posted by tuxedocivic View Post
For a 40hz high pass, I'd go active.

This could be as simple as a series cap between pre & power amp (or in a tape loop)

Quote:
Doing it between your amp and the speakers is way more expensive and difficult to do.
Difficult to do is probably better described as "nigh on impossible due to the resonance peak(s).

If you want max bass out of CHR, one of the 2 Woden ML-TLs (Wessex or Mercia) will get you as close as you can get -- just double the x-section area. If you do a bipole, you eliminate much of the comb filter issues (given suitabe listening distance.

Frugal-phile | Box Library / Mark Audio

Or even 1 driver/face like the old EPI miniTower/Rower (aka 500 & 1000), Mercia could be a 13.75" square column. Wessex would become a 12" column.

dave

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Old 6th February 2013, 08:19 PM   #6
Jaydog is offline Jaydog  Canada
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Thanks for the information - yes I see comb filtering will likely cause problems, I'll try to figure out something to help with that if it's possible.
I've got an integrated NAD amp, but it has pre-out and main-in for a pre-amp, so I could probably put an active filter in there if I need. I'll research on it a bit, much appreciated!
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Old 6th February 2013, 08:29 PM   #7
Jaydog is offline Jaydog  Canada
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Thanks for the pointers Dave, I too went to the best University in the world (I can compare to nothing else though). I really wanted to do a smallish array style speaker - sounds like you guys think it's may be too hard to deal with comb filtering.

I'll check into the capacitor(s) between the pre-out and main-in.
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Old 6th February 2013, 08:41 PM   #8
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You've got the right idea Jaydog.

Quote:
Originally Posted by planet10 View Post
PS:i went to U of A.
Hey so did I.
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Old 6th February 2013, 09:11 PM   #9
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I really wanted to do a smallish array style speaker
Then do it. Comb filtering looks worse in the graphs than what it sounds like... there are lots of pro (Roger Russell) & con arguments. Scott & i have been waiting for someone to build these and give some real world impressions.

Somehwere on Madisound is a modular line array project we did for Madisound for the CHR. (i also have it on my HD at home)

dave
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Old 6th February 2013, 09:15 PM   #10
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Somehwere on Madisound is a modular line array project we did for Madisound for the CHR.
I found it in webspace. http://frugal-phile.com/boxlib/TheCH...lan-040911.pdf

Easy enuff to juggle between 3 & 4 drives per module.

dave
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