OB project, Jame's Quasars copy

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IslandPink
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Re: OB project, Jame's Quasars copy

Post by IslandPink » Fri Jan 12, 2018 5:24 pm

Absolutely. James could probably give us some further insight.
There's no need to change the inductor ( once you have one ) for the two FR drivers. The main change I'd see is the capacitor would need to be larger for the EX3 , as being a low-Q driver it's already rolling off a bit below 200Hz, whereas the PM6C is flat towards 150. The attenuation resistor on the bass driver would be smaller or not required with the EX3.
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Re: OB project, Jame's Quasars copy

Post by chris661 » Sat Jan 13, 2018 5:56 pm

Here's a nice article by Rod Elliott on the comparison between series and parallel crossovers.

http://sound.whsites.net/parallel-series.htm

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Re: OB project, Jame's Quasars copy

Post by thomas » Sun Jan 14, 2018 1:58 pm

OK I have finally ordered, as a start, a reasonably priced pair of 1.5mH air core inductors, from CPCFarnell.

Looking back to my choice of 1.5mH / 30uf, I think I had been looking here

http://www.audio-talk.co.uk/phpBB2/view ... 3&start=45

as James' idea of a fairly high crossover value albeit with the Lowther EX4 seemed a reasonable place to start. However in the meantime I'll have to pick a quiet moment and try bigger caps, and it seems bigger value inductors will have to follow.
simon wrote:
Fri Jan 12, 2018 2:05 pm
What Nick and Mark said, which was my point earlier. But also, I find the louder the volume the more the volume relatively from the bass driver. This was most notable when I took the Quasars to Owston a couple of times ago. Played in the barn of a room (at much higher volume) compared to a bedroom at home the bass completely overwhelmed the sound.

I "fixed" it by using half an Lpad as the series resistor so I can vary the amount of bass to suit now. And by having more bass at lower levels I found I don't push the volume control as much. Which has to be good. But I can easily tweak it if I do want to turn up the volume.
I remember those bass monsters a couple of Owstons ago! Curiously this seems to be my experience too, at low volumes my OB's sound pleasant enough, but when I crank them up the bass seems intrusive.

An Lpad seems a good idea for bass attenuation.

Dim question now, but is your Lpad right by the bass driver, and 'within' the bypassing cap or in series with your inductor?

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Re: OB project, Jame's Quasars copy

Post by simon » Sun Jan 14, 2018 8:59 pm

The Lpad was one of my more recent pragmatisms! I've actually built the crossovers on a board with bananas and Lpads and anything else I could think off to make it convenient.

I've attached two crossovers - the first is James' EX4 version and the second is his 208 version - it should make it clear where to put the resistance.
Attachments
EX4 Quasar Filter.png
EX4 Quasar Filter.png (9.56 KiB) Viewed 79 times
F208 EZ Quasar Filter.png
F208 EZ Quasar Filter.png (10.66 KiB) Viewed 79 times

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Re: OB project, Jame's Quasars copy

Post by IslandPink » Sun Jan 14, 2018 9:17 pm

Wow - I'd never seen that - it is a high crossover. You could go a bit lower with the EX3 , but see how it goes.
Actually I don't in that case understand the 7.2mH with the 208Ez, I tried something like that and I couldn't get it to gel - the Fostex is even lower Qt than the EX4, so I'd expect any solution to use a really high crossover.
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Re: OB project, Jame's Quasars copy

Post by simon » Sun Jan 14, 2018 11:18 pm

Aye, they're BIG chokes...

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Re: OB project, Jame's Quasars copy

Post by IslandPink » Sun Jan 14, 2018 11:43 pm

The 7.2 is, the 1.5 isn't.
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Re: OB project, Jame's Quasars copy

Post by simon » Mon Jan 15, 2018 7:20 pm

Yes, I was referring to mine which I use with the 208s

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