Something stirs in the Undergrowth

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Nick
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#2236 Re: Something stirs in the Undergrowth

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IslandPink wrote: Thu Oct 25, 2018 10:25 pm I was going to post more but a fire alarm took us outside for over 40mins, some people nearly froze.
You should have started a fire to keep warm.
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#2237 Re: Something stirs in the Undergrowth

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Doesn't most of that article view the drivers as resistivity loads?

I like the last bit though, use of optically DAC's as isolating transformers. Though I might argue for using these instead

https://uk.rs-online.com/web/p/products/0459673/

BTW, you DAC has them inside Mark, FWIW.
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#2238 Re: Something stirs in the Undergrowth

Post by IslandPink »

Ah OK, so is that the bit immediately into the PP output stage ?
Nick wrote: Fri Oct 26, 2018 1:33 pm Doesn't most of that article view the drivers as resistivity loads?
Yes, Broskie always leaves some as an exercise for the student.
I think the next step is to put the whole thing in Spice and replace each 8R driver with the real Le and Re for that driver. Then plot the power response across each of the three 'Re's and try to sum them. Adjust some of the L and C values in the crossover accordingly to get back the target crossover points.
Then consider the actual lumps & bumps in the speaker response and see if you want to tweak the crossover points a bit.
The consider the driver fore/aft placement based on the acoustic centres.
Then let the special nurses take you away for a rest.

But seriously ( folks ) this is the way to get a 3-way Quasar working, though I think the variant with the steepening slope on the tweeter would be safest.
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#2239 Re: Something stirs in the Undergrowth

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IslandPink wrote: Fri Oct 26, 2018 1:58 pm Ah OK, so is that the bit immediately into the PP output stage ?
No they are between the SPDIF receiver, USB interface and DAC chip so each can live in their own data, power supply and ground environment.
I think the next step is to put the whole thing in Spice and replace each 8R driver with the real Le and Re for that driver. Then plot the power response across each of the three 'Re's and try to sum them. Adjust some of the L and C values in the crossover accordingly to get back the target crossover points.
I was thinking more of the complexity of James description of the series xover in my speakers as allowing the drivers to see each other more than a parallel one would and aid driver integration by this.
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#2240 Re: Something stirs in the Undergrowth

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Well, with series filters you've got in effect a single circuit where all components including the drivers are (to a point) connected with each other; in parallel circuits each leg is more or less independent electrically speaking. YMMV whether that makes for better integration or not. Quite possibly with symmetrical 1st order, since it is largely unaffected by changes in driver impedance & if the filter is designed to sum flat, then that's what it will do, albeit shifting the frequency. For other types? Maybe. One property I like about series (or quasi-series) is that you can design it so some of the components perform several functions relative to the parallel equivalent. The downside is they're harder to design since everything is in circuit with everything else, so a component change can affect the entire circuit, not just a given leg.

For what it's worth, 2nd order high pass with a 1st order low pass (or bandpass for a 3 way or higher) has tended to be quite popular with series crossover fans given the extra protection it gives to the tweeter / mid-tweeter / full-range / whatever you happen to be using.
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#2241 Re: Something stirs in the Undergrowth

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Scott - first things first, while you're here : do you know anyone in the UK who has built any of Ron Clarke's horns ? I really need to listen to one if at all possible.
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#2242 Re: Something stirs in the Undergrowth

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Not off the top of my head I'm afraid.
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#2243 Re: Something stirs in the Undergrowth

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IslandPink wrote: Fri Oct 26, 2018 4:33 pm Scott - first things first, while you're here : do you know anyone in the UK who has built any of Ron Clarke's horns ? I really need to listen to one if at all possible.
Mark,
you may find a UK builder of the Dallas II in this old WD forum thread http://www.world-designs.co.uk/forum/sh ... php?t=2345
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#2244 Re: Something stirs in the Undergrowth

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Thanks Colin, just put up a 'call out' for Pete2112 on the WD forum. Been a few years, fingers crossed.
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#2245 Re: Something stirs in the Undergrowth

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simon wrote: Wed Oct 24, 2018 10:26 pm Do you mean SB ACOUSTICS SB34NRX75-6? I'm using one in a 124L sealed cab with Alpair 12Ps in the James inspired tv console I've built this year. I'm surprised by just how much info I was missing, and songs have taken on a different perspective with that bottom end grunt. I like it a lot and have considered adding one to the Quasars, but James thinks it needs to be a 600L cab with a Supravox 400GMF :-D. But 600L is huge and I'm not sure I'd be able to get it up the stairs anyway...
Yes that was the (SB) one, good effort, would like to hear that . I'd like to hear the 400GMF sealed too, but we'll let James do that one !
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#2246 Re: Something stirs in the Undergrowth

Post by vinylnvalves »

My supravox’s I have tried sealed as well as aperodic, but they are only 200 Litre cabinets. The sealed needed a lot of lower end contouring to get below 30hz. The aperodic I found as a good compromise, over bass reflex, I still have a little bit of low end contouring to raise below 40hz up by 6db. If you want the ultimate flexibility go field coil then you can have what ever Q you like. Field coils mean more power supplies though.
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#2247 Re: Something stirs in the Undergrowth

Post by simon »

I'm a novice at speaker design but when I was playing around a year or so ago I just couldn't get the 285GMF to work as a sub, not sealed anyway.. I couldn't get the 400GMF to work well either, but James knows what he's doing and I don't! 600L is like a small wardrobe though!
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#2248 Re: Something stirs in the Undergrowth

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To get a 'sub' response you need a driver that has a heavier cone and a free-air resonance of about 20Hz for starters. I must have a look at the alignment with the 400, James is fond of Q under 0.7 which gives better transient response, he'd have probably traded-off some amplitude below 50Hz.
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#2249 Re: Something stirs in the Undergrowth

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Maybe. I couldn't get anywhere near his design performance.
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#2250 Re: Something stirs in the Undergrowth

Post by vinylnvalves »

Just looking at the specs of my 400-2000’s, they are quite different to the GMF’s, Fs is significantly lower, mine are 24hz, CMS is about half that of the GMF’s. Regarding the Beymas I mentioned, looks as if art of sound in Germany have some old stock...https://www.ebay.co.uk/itm/Beyma-15B100 ... SwMmBVhAS4. prices aren’t that bad for new drivers ( when you compare them to Supravox). Over in the states , the 18” peavy lowriders seem to be used a lot, at least on Diyaudio. Prices this side of the pond too high.

My mate Dave, has the linkwitz OB’s, which have a pair of seas lroy26 subdrivers per channel,in a W configuration, they keep up with the midrange BG neos, nicely - very deep chest thumping bass ( for cinema stuff) They need a good metre of space around them to sound good, which I don’t haven’t otherwise I would have probably have some too.
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