X-LS Encore Tweak

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Folsom

X-LS Encore Tweak
« on: 7 Aug 2016, 06:29 pm »
Hi everyone,

So I was playing around and doing some resonance testing. I'm not going to explain electrical resonances, but...

My result found that 82kohm across the big inductor for the woofer yields improved overall sound. The bass has more control. It sounds a touch less but to me it's less boomy; which wasn't bad to start with. It takes a couple hours of play before it settles and sounds correct.

jcotner

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Re: X-LS Encore Tweak
« Reply #1 on: 7 Aug 2016, 08:04 pm »
Interesting concept. And it should make the woofer more efficient
because you minimize the current at the resonance point.
However the resonance point is also frequency dependent so
there will be some change as the frequency sweeps.
I have no idea of what the Q would be for this network, but
it would be interesting to see the curves from a spice run
for that topology.
You shouldn't had to use too big of a resistor (wattage)
for that large of resistance I would think.

Folsom

Re: X-LS Encore Tweak
« Reply #2 on: 7 Aug 2016, 08:38 pm »
It won't change the resonance that's calculated with the capacitor. Q will actually be closers to what was selected when designing the crossover.

It's essentially invisible to the crossover and drivers. You might see 1mv or such that bypasses the inductor but it won't be enough to get the woofer moving. The DCR of the inductor will appear something like .01mohm higher; effectively nothing.

It's nearly impossible to use LTSPICE to model something like this... you can measure it with the right equipment but not necessarily easily.

The DCR of the inductor is high, so it was mostly dampened to start with. This change could be affecting higher frequencies, such as RF.

How it manifests in this situation as a correction is that the inductor is more linear, and will have less minor saturation so the amp should also respond more linear by not over correcting.
« Last Edit: 7 Aug 2016, 10:36 pm by Folsom »

S Clark

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Re: X-LS Encore Tweak
« Reply #3 on: 7 Aug 2016, 08:49 pm »
Ok, I'm lost, Jeremy.  How does letting a handful of electrons bypassing a baffle step inductor cause a noticeable difference in linearity??  I mean, it's 82 000 ohms... there's not much current going by.  What are we addressing here and how? 
Danny? 

Folsom

Re: X-LS Encore Tweak
« Reply #4 on: 7 Aug 2016, 09:53 pm »
The objective isn't to "let a few past".

Let's say for example you've got a 92mhz signal going to the inductor, except that instead of decreasing it it increases it substantially. That's a problem to varying degrees. If the 92mhz was strong enough it could turn the inductor into a resistor.

In this case the relative offending signal causes mostly minor differences, but I find the correction to be rather pleasing. Essentially you're voltage dropping it, with an alternative path, enough that it will no longer increase in strength in the inductor.

Anyone else is welcome to explain this better than my poor ability to convey the complicated subject... Especially if you want to throw in SRF etc...

srb

Re: X-LS Encore Tweak
« Reply #5 on: 7 Aug 2016, 10:10 pm »
It sounds like a personal preference more than anything.

I imagine Danny would have designed the crossover as a down-the-middle compromise between the amount and tautness of bass output.

Folsom

Re: X-LS Encore Tweak
« Reply #6 on: 7 Aug 2016, 10:30 pm »
Different speaker cables for example could change the needed value, but may not as it could be inherent.

This isn't something crossover designers plan for, ever. And it doesnt change the original crossover. It's more akin to putting higher quality footing under a CD player. You're just making the natural function better.

If the original crossover was intentionally manipulated to avoid good measurements because it was flawed with odd resonances, basically adjusting by ear, then sure you may have a problem. But you'd have a measurement that didn't look flat at all, and the X-LS measure very flat.

HAL

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Re: X-LS Encore Tweak
« Reply #7 on: 7 Aug 2016, 10:31 pm »
Any inductor has parasitic reactive components of resistance and capacitance.  There is no such thing as a pure inductor.

When the LC becomes a resonance circuit at a specific frequency, then adding the correct R will damp the resonance of the system.  This use to be specified as the quality factor for an inductor for RF circuits.

You can use an LRC bridge to measure the parasitic components of the inductor and calculate the R needed to damp the system. And then you can model it in PSPICE to find the R value needed as well.

Adding any extra component adds cost to the design that has to be weighed against the overall budget.  Simple as that.

Folsom

Re: X-LS Encore Tweak
« Reply #8 on: 7 Aug 2016, 10:39 pm »
In this case it adds $0.20 to the budget!


jcotner

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Re: X-LS Encore Tweak
« Reply #9 on: 8 Aug 2016, 02:42 am »
In this case it adds $0.20 to the budget!

Well it is a design tweak and it would be interesting if somebody else tried it and
perhaps could give the benefit of a second pair of ears.
I mean most of the changes Danny does to somebody else's design usually run
$50 or more, as I remember, so it is kind of hard to knock adding a single resistor.

Folsom

Re: X-LS Encore Tweak
« Reply #10 on: 8 Aug 2016, 03:19 am »
It's not a change in crossover frequency or baffle step correction. It wont bring as much quality as going from a poor crossover to Danny's work.

My other speakers are not GR-R, so for now these are the only ones I'm suggesting this about. What I really want is a second set of ears!

mlundy57

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Re: X-LS Encore Tweak
« Reply #11 on: 8 Aug 2016, 04:01 am »
Is this on the stock PCB crossover or an upgraded point-to-point wired crossover?

Mike

Folsom

Re: X-LS Encore Tweak
« Reply #12 on: 8 Aug 2016, 05:27 am »
Mine is a PCB with upgraded caps and resistors.

They're the same part values so it likely works the same either way unless an upgraded inductor has significant DCR difference (no other value is given for inductors for crossovers). The PCB probably can't generate any of its own resonances in particular since it's only got one layer.

The resistor is just connected to both leads of the large inductor.

Captainhemo

Re: X-LS Encore Tweak
« Reply #13 on: 8 Aug 2016, 03:44 pm »
If I had left the input leads a bit longer that last pair I just built, I'd pull the network and try this, next ones I'll leave the  input wires logner so it's simple to pull the networks out.
Jeremy, are your cabinets lined with no rez ( sorry can't remember) ? Have always used it   the Encore kits I've built and bass has always been very goo,  clean and quite punchy actually, I've definitely never found it to be boomy although this could be a bit room dependent I suppose
A $.20 resistor is  a lot cheaper than a sheet of no rez, but, if your cabinets are  not lined with it, you  really shold give it a try.

jay

Folsom

Re: X-LS Encore Tweak
« Reply #14 on: 8 Aug 2016, 05:09 pm »
I have no-rez. I'd never choose one or the other. My speakers didn't sound boomy to start with, I think they're just less so with the resistor. It's hard to understand till it sounds different

Captainhemo

Re: X-LS Encore Tweak
« Reply #15 on: 8 Aug 2016, 05:22 pm »
I have no-rez. I'd never choose one or the other. My speakers didn't sound boomy to start with, I think they're just less so with the resistor. It's hard to understand till it sounds different
Wasn't  really saying one or the other, was more  just wondering where your stating point was.
I['ve got another  kit I've got to build out one of these days, maybe I'll give the extra resistor a shot when I assemble the networks  :dunno:

jay

jay