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Old 1st April 2007, 08:57 PM   #1
phn is offline phn  Sweden
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Default Altec x-over questions

I plan to upgrade the x-overs in my speakers. The speakers have this N800-8K x-over, meaning x-over point at 800 Hz. A 2nd order Butterworth network should have 17.5uF caps and 2.25 mH inductors. That's also what I find on the Internet: http://members.tripod.com/~ThunderBobWorld/A7xover.htm

What confuses me is that the N800-8K x-over has 0.55 mH inductors and one 8 uF cap and one 21 uF cap. (My x-overs say nothing about the inductor values. The 0.55 mH comes from an image I found on the Internet.) Why the 8 and 21 uF caps?

Once that is sorted out, do you recommend I replace the caps only or everything?

Why should I bother if it's Butterworth or Linkwitz-Riley or whatever as long as it's a 2nd order x-over?
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Old 1st April 2007, 09:04 PM   #2
Zen Mod is offline Zen Mod  Serbia
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Default Re: Altec x-over questions

Quote:
Originally posted by phn
I plan to upgrade the x-overs in my speakers. The speakers have this N800-8K x-over, meaning x-over point at 800 Hz. A 2nd order Butterworth network should have 17.5uF caps and 2.25 mH inductors. That's also what I find on the Internet: http://members.tripod.com/~ThunderBobWorld/A7xover.htm

What confuses me is that the N800-8K x-over has 0.55 mH inductors and one 8 uF cap and one 21 uF cap. (My x-overs say nothing about the inductor values. The 0.55 mH comes from an image I found on the Internet.) Why the 8 and 21 uF caps?

Once that is sorted out, do you recommend I replace the caps only or everything?

Why should I bother if it's Butterworth or Linkwitz-Riley or whatever as long as it's a 2nd order x-over?

why don't you try with Hiraga's xovers?

search here
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Old 1st April 2007, 09:25 PM   #3
phn is offline phn  Sweden
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Didn't know there was such a thing. I have searched now. Came up with nothing relevant, here or google, yet. Will have to try more search phrases.

Maybe the Hiraga x-overs will answer my question about why the 8/21 uF caps. As I understand it it should mean overlapping (gap in the frequency response isn't that likely). But that still doesn't make much sense since the idea use to be that there should be no overlapping. Not that I mind what I hear.
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Old 1st April 2007, 10:10 PM   #4
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by phn
Didn't know there was such a thing. I have searched now. Came up with nothing relevant, here or google, yet. Will have to try more search phrases.

Maybe the Hiraga x-overs will answer my question about why the 8/21 uF caps. As I understand it it should mean overlapping (gap in the frequency response isn't that likely). But that still doesn't make much sense since the idea use to be that there should be no overlapping. Not that I mind what I hear.

from Sound Practices issue 11
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Old 1st April 2007, 10:49 PM   #5
phn is offline phn  Sweden
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Thanks.

This is for A7, 800Hz? I have to ask especially since most of what I came up with searching related to A5.

Also, what is the E in resistor value "5E"? Is it simply "5R"?

I will test this as well as the original network in spice just to see what they do. Replacing the entire xover is a future project. I was stupid to make this small but nasty mark in one of the speaker cabinets. Not intentional, but still stupid. Ideal would be to make new, better cabinets. But since I don't have a workshop, I will need to have it professionally done. That's expensive. It will cost more than the speakers cost me. That I do not like.
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Old 2nd April 2007, 11:40 AM   #6
sreten is offline sreten  United Kingdom
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Hi,

Unless you know exactly what is going on, replace the components
with the same values. The electrical response of the network is not
the same as the end acoustic response result.

/sreten.
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Old 2nd April 2007, 03:08 PM   #7
GM is offline GM  United States
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Default Re: Re: Altec x-over questions

Greets!

Interesting! The 'E' model is the most current of the N800 series XOs I was aware of before the N801 series. Got a picture of the front? What components is the A7-800 loaded with and year manufactured ? Does the compression driver have a loading cap?

The Hiraga XO is for the A5, so even if the schematic will work, the component values won't, at least not optimally.

Regardless, short of a complete new XO with impedance compensation and HF contouring network like used in some later models, best to follow sreten's advice.

BTW, there's an Altec users forum: http://www.hostboard.com/cgi-bin/ult...b=forum&f=3729

GM
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Old 2nd April 2007, 05:57 PM   #8
phn is offline phn  Sweden
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sreten, will do. My problem was the differen't cap values. Everything I have read (which is limited), says this thing and then I have this.

I didn't get the Hiraga design to work.

GM, my speakers are 846B Valencias. I thought they had the same components as the A7-8. At least that's what Altec, and everybody else, says. But the compression driver seems to differ based on this: http://www11.plala.or.jp/se_ke5583/A...aker/a7-8.html

And the same might go for the xover.
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Old 3rd April 2007, 02:15 AM   #9
GM is offline GM  United States
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Greets!

OK, I had a 'senior moment' and forgotten about the 846B's network. This speaker uses a weaker motored compression driver combined with a slightly weaker motored 416 than the A7-8 or A7-500, so a simple 2nd order Butterworth won't work well at the 800 Hz min. XO point of the 811. Still, an R/C network between the pot and HF like used in the Hiraga can smooth out its response to a higher roll off. Even just a cap across the pot will help if you feel the HF lacks 'sparkle'.

GM
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Old 3rd April 2007, 08:26 PM   #10
phn is offline phn  Sweden
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Thanks. I'm very happy with the HF. Doesn't have the "buzzing" of traditional tweeters. But I expect to change my opinion of what is good-sounding and good HF once I upgrade the xover.

With the relatively low values needed (.55mH, 8 + 21uF), it will be a relatively cheap xover.
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