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Theatre 4 Woofer RC network: I just removed it. [message #34867]

Thu, 24 January 2002 08:29

BillEpstein
Messages: 886
Registered: May 2009

Illuminati (2nd Degree)

I liked the 8 ohm attenuation on one speaker and especially when I ran it on one speaker with the other not attenuated. Apparently the 2 "blended".
But with both speakers attenuated I find the mid-range sounds "muffled". I'd rather have the bass a little peaky but the right balance in the mids with the treble.
It's because the Delta runs to 1600 Hz, right? Changing cap values or resistor values make any difference?
Comments, anyone? Wayne?

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Comments about Zobel networks [message #34870 is a reply to message #34867]

Thu, 24 January 2002 11:33

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

Page 58 of the crossover document shows the response you should expect from the system without the woofer damper filter. It's not too bad, really, but there is some peaking in the woofer at the crossover frequency. The effect of the Zobel in this particular loudspeaker is subtle, but I think it's worth adding. On some speakers, the peaking is much more severe without a Zobel, so its influence is stronger.

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Question for Wayne, re: RC fine tuning. [message #34879 is a reply to message #34870]

Fri, 25 January 2002 07:42

Garland
Messages: 269
Registered: May 2009

Grand Master

Wayne, If one were to want to slightly adjust the amount of damping in the RC network of the Theater 4 Pi, how much would the values used change. ie how much + or - in resistor and Capacitor values would you change to? Hope this makes sense! Thanks.

Garland

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Re: RC fine tuning [message #34881 is a reply to message #34879]

Fri, 25 January 2002 10:57

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

A Zobel is a very high-tolerance network and small component value changes do almost nothing. Component changes less than 35% are inaudible and barely measurable. So if you're going to change resistance or capacitance values and expect to hear a difference, don't even bother to buy components of less than 30% different than specified. Perhaps 30%, 50% and 100% variance would be good choices to make. You can easily model the network in Spice to see what effect changing the values will have.

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Re: RC fine tuning [message #34887 is a reply to message #34881]

Fri, 25 January 2002 15:38

BillEpstein
Messages: 886
Registered: May 2009

Illuminati (2nd Degree)

I've got (2) 10 ohm 20 watt wire wounds I could parallel to make 5 ohms, 20 watts, right? The only caps I have lying around are 2.0uF. I have 2 of those which would make 4uF in parallel.What should I expect with 40% less resistance and 80% less capacitance? Is it worth trying or should I wait to get a 10uF cap?
What the hell, I'll probably give it a shot anyway although the caps are the famous Bottlehead "greenie meanies" (metallised polyester) from the Foreplay kit.

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Questions for Till E [message #34889 is a reply to message #34887]

Fri, 25 January 2002 16:27

Garland
Messages: 269
Registered: May 2009

Grand Master

Hi Till,
If you have the time I was wondering if you could answer a few questions for me:
You said you felt the midrange was a bit "muffled" with the RC network on the woofer. I was wondering if you could describe the sound a bit more: is the sound recessed, or blurred, or seems to be hidden( the proverbial "veil"); that sort of thing. I am getting ready to fire up my Theater 4's in a day or so and wanted to listen for the effect you commented on. What brand and value components did you use in your crossover and zobel? The last thing we want in our loudspeakers is a muffled midrange,eh?

Thanks!

Garland

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Re: Questions for Till E [message #34891 is a reply to message #34889]

Fri, 25 January 2002 19:16

BillEpstein
Messages: 886
Registered: May 2009

Illuminati (2nd Degree)

Blurred, lack of focus, missing the aliveness that pours out of the Pi's from the first minute they're fired up. Came right back with the removal of the Zobel but so did the slightly overcooked bass. I'm playing with cable now. Have 26 ga. RS magnet wire in now sounds like a transistor radio. But the same twisted pairs of RS 26 ga. sounds great on the JBL 3677's. Go figure.

Double run of Cardas something 12 ga had been sounding good. Have single runs of 12 ga. and single runs of 16 ga. zip ready to go. All these are internal hook-up. Speaker cables to amp continue to be Mapleshade double helix. Crossovers are wired up with Jena labs 18 ga polyprop dialectric. Wish I could afford the additional 40 feet ($4/ft) to wire internal with it. Or the Mapleshade, for that matter. Paramour/ Pi seems to be very sensitive to wire. Let me know what you're using.

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Re: Questions for Till E [message #34894 is a reply to message #34891]

Sat, 26 January 2002 03:58

Garland
Messages: 269
Registered: May 2009

Grand Master

I'm using Cardas 17awg hook up wire internally. I'll first use some older audioquest quartz for amp to speaker while I experiment with some DIY cables (cat 5 braids, Jon Rische co-ax etc.) Interesting, the different results using the magnet wire! I have installed the eminence crossover in my Pi's; did you use this or make the xover up from scratch? And what quality caps/resistors did you use?

Right now the 4 Pi's are waiting the addition of the bracing, damping material and then sealing up and installation of drivers. Lastly I plan on veneering with cherry veneer though the cost of the veneer pushes my allotted outlay for this project over what was budgeted and cleared by the holder or the bank book, my wife; But then the veneer will go along way in allowing these large speakers to reside in our living room! Wives don't always approve of birch ply peppered with drywall screws, eh?

Please keep posting about your fine tuning. And good luck!

Garland

P.S. Paramours are in the initial stages of assembly- ready to start wiring today.

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Re: Questions for Till E [message #34897 is a reply to message #34894]

Sat, 26 January 2002 08:35

BillEpstein
Messages: 886
Registered: May 2009

Illuminati (2nd Degree)

OK, the magic is back. Ripped out the magnet wire and replaced with 14 ga. that I pulled out of the Home Theatre excess as it had been playing for months and there would be no break-in issues. Instant gratification!

Now the upper mids seem a tad hot on Milt Jackson's vibes, for instance. So I'm about to put alligator clips on the woofer Zobel to, dare I say it, A/B it.

I think I mentioned before that Joe Bfttpslk is my patron saint? One of the 12AT7 in the Paramour has become microphonic AND I discovered that you can only R&R (remove and replace) the CH-3 lens a few times before the heads of the bolts dig away the plastic and cruise right down to the wood. Wayne, what do you think Peavey would do for me? Woe is me! Where do you get black oxide washers?

Oh yeah, I used the Eminence x-over and just added the network. Mills WW 16 0hm, 10 watt resistors and 0.47uF 450V Auricaps, though. And I only used one resistor as I knew it would be used exclusively with the Paramour and wattage wouldn't be an issue. Figured one resistor would sound better than eight! And why spend $2 when you can spend $12? I liked the Auricaps so much in the Foreplay against Solens that I didn't even bother trying anything else. Have to get some Auricaps for the Paramour outputs.

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Re: Questions for Till E [message #34898 is a reply to message #34897]

Sat, 26 January 2002 09:27

Garland
Messages: 269
Registered: May 2009

Grand Master

Bill, I've posted on the Bottlehead forum questions concerning the parafeed cap in our paramours. I was wondering if the value of the caps could be varied to effect the low freq roll-off or woofer damping. It might be that we could effect some sort of bass synergy between the amps output and the woofers and delete the zobel. We'll see!

Garland

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