Sound Quality Vs. Measurements

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Pano

Pano

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Sure, not hard. You just need the proper size inductor for that woofer (it will be big) and the appropriate driver to had off to in the mids.
I've worked with OB from from 0.3 to 1.1 Qts. You just have to learn the trade-offs

EDIT: Just looked again. I would not use that as a woofer on OB. A 12" would be minimum. Or go with four 8" per side.
 
a.wayne

a.wayne

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Joined 2008
Pano said:
I'm using the big bother of that GRS driver, 2 per side, on a 52"x24" baffle. (~1300x600)
GRS 15PF-8 15" Paper Cone Foam Surround Woofer 292-415

The 12 should certainly get you started - but on a baffle that big, why not use a 15" or even an 18, if you can find one cheap. We are lucky here in the U.S. to have great, inexpensive sources for drivers, like Parts Express
Click to expand...

Yeah and the good ones are as much or more than what they pay in Europe, cheap badly design is still cheap , agree ...

A good 12 inch woofer here is easily 300.00
 
Pano

Pano

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Sure, but it depends on "good for what". I can tell you, the GRS are cheap, but are superbly suited for open baffle. I like high quality drivers and own too many, but some of the crazy things out of the East will surprise you. Used where well suited, they excel.
 
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dvv

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Joined 2004
Wayne, good quality drivers were ALWAYS expensive.

10 years ago, I paid € 210 per bass unit (10", uses Son Audax' version of aerogel, rubber surrounds, die cast frame, etc) - and that was the low price for manufacturers, on the street at least 40% more.

Assuming an inflation of just 2%, that would be something like € 260, or about $ 340. I think this is unrealistically low, prices have a tendency to escalate.

So what's new?
 
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nigel pearson

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Joined 2007
a.wayne said:
Yeah and the good ones are as much or more than what they pay in Europe, cheap badly design is still cheap , agree ...

A good 12 inch woofer here is easily 300.00
Click to expand...

In the world of baffle speakers bad might work better . For example the 25 Hz to 50 Hz ability can not be realized . 50 Hz -3dB as in Magneplanar SMGa is about as good as it gets .

Typical Qts for a high quality woofer is about 0.6 . Ideal Qts for a baffle speaker " might be " 1.5 . Insertion of a resistor or inductor with the high quality 0.6 unit might well level the playing field . Doubtless the high quality speaker can be EQ'ed in addition ( active and passive options or mix ) . Doubtless also that Fostex can relieve me of much money for something suitable , it will have the 1950's RCA look and have bananas in the mix ( yes ) .

Having said all of that a baffle speaker is a daft idea . That lovely pressure from the box is gone in a mystical belief that the box is a problem . A 12 inch bass unit isn't my idea of audio heaven . My conjecture is that the quality of a baffle speakers will be 90 % the maths being right and 10% money thrown at it . There seems a narrow window where it might work and not sound slow . 800 Hz might be my crossover point on 1200 x 740 baffle 12 inch bass . 4 x 3.5 inch line array , cheap piezo at 7kHz . I hope to borrow a PA active crossover to try every combination of frequency and filter rate . It has been suggested that first order and brick wall are best . At 40 Hz I suspect brick wall will be required . That is to stop the cone flap on frequencies it can not reproduce . The Qts high helps it do the pole jump rather than run under the pole . That might mean 12 db more bass and still have good power handling .

One idea which might work is a Boffle . That is baffles like a two stroke motorcycle exhaust , an open box . Rather nicer than a port .

Wharfedale fashioned a polystyrene lump glued to a standard paper cone . This lived on as a KEF B139 ( Cooke left Wharedale to develop the idea ) . I might give it a go . Everything is wrong with baffle speakers so why not make it more wrong ? Wharfedale are often quoted when discussing open baffle . Gilbert Briggs did a very good examination of speaker box design and materials which says ultimately a box is not a good idea ( re-radiation of filtered and distorted information from box side walls back to the ear ) . Briggs advocated plywood with sand filling . I think 3 tons was thought to be where the box competed with an open baffle ?


Anyone got good reading on line arrays , better still a simulator ? The idea is to filter N1 & 4 to get better vertical / horizontal compromise .

One idea I did have is to buy some cheap JBL PA boxes . Would look cool to have JBL on the bass units . Even better is some weird Sony 12 inch car subs ( $120 UK ) . The drive units look like a pastry cutter . They look the dogs whatsits . Reality says the cheap ones pole jump better .
 
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nigel pearson

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Joined 2007
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Fostex W400 . Retail $3500 ( seen at $2550 to Euro 3295 ). Probably less good for pole jumping . With a bit of corruption it could be made to work . It is said it is only good for 1800 Hz . The cheap one shown might do better ! How ironic that damping factor must be destroyed to get it to work . The big deal is when forced to do it other benefits arrive . Keeping the junk that the amplifier has to look at resistive is no bad thing . It seems the output impedance should be kept to SE valve design levels , above that ringing is likely .

Variable Amplifier Impedance
 
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