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Old 1st February 2009, 02:40 AM   #1
bvan is offline bvan  Denmark
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Default Ripole vs Dipole

I've got four Eminence Beta 15's and am looking to build a pair of subs to play bellow 200hz.

I havent been able to find too much opinion on the subjective differences, if any, in the sound of a ripole and a H-frame dipole, so am hoping for a bit of input here.

Another question I have, the ripole apparently lowers the resonant frequency bellow what it would be in an H baffle or 90 degree W baffle. Is this true, and would it offer any advantage over simple boosting the frequencies bellow fs in the dipole. (I'll have parametric EQ on the subs)

So apart from the more compact size of the ripole, I'm looking for any other reason to build this over an H or W baffle dipole.

Thanks for any opinion,

B.
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Old 1st February 2009, 08:43 AM   #2
Calvin is offline Calvin  Germany
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Hi,

there are only minor differences betwen the dipole types if any are audible at all.

The small folded dipoles do indeed lower the resonance ferquency.
My sims show that the Eminence Beta 15A profits very much from this fact. The new Fb could go down as low as 18Hz without, 17Hz with passive EQ-network in a cube of 44cm side lengths. Since the Betas are high Qt drivers you might even not need further basslift equing. But it needs not much power to drive the system into saturation. Just 4.5V@20Hz, 10V@30Hz and 20V@40Hz (drivers electrically paralleled) is what it takes to drive the Betas to their excursion limit. This translates to 97dB/104dB/109dB in theory. Subtract ~4dB and You get more real values.

The Beta15A though not a driver I´d prefer to use anyway clearly shows the advantage of the small folded dipole. You can use drivers with elevated resonance frequencies which You normally wouldn´t use for subwoofers. Drivers which often stem from PA-manufacture with accordingly good and massive build quality and a reasonable price tag attached. Drivers with relatively lightweight moving systems and rather stiff -and preferably very progressive- supensions. Drivers of this built are nearly undestructable even in OB usage.
Better suited to small folded dipoles are the Delta15 and the Kilomax 18A. Offering better build quality and higher power and SPL limits.

jauu
Calvin
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Old 2nd February 2009, 03:53 AM   #3
bvan is offline bvan  Denmark
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Thanks Calvin.

Yeah there are better Eminence drivers than the Beta, but was able to get them at a steal. Also, I never listen over 80db so overly engineered drivers might not make sense for my purposes. Will be interesting to see how these Betas compare to the current single Augies I use in my main system.

I've got one more question, assuming I go ripole. Which is better: drivers facing each other (ala Ridthaler), or facing the same direction like the Linkwitz Dipole Woofer.

Many thanks

Bevan
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Old 2nd February 2009, 09:35 AM   #4
Calvin is offline Calvin  Germany
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Hi,

the two drivers should work under identical conditions, which is not the case with most of the Linkwitzalikes, but always with the Ridtahlers. To my taste there´s no use to change the driver´s orientation to get lower distortion, when the two drivers work under different conditions (chamber sizes) and therefore produce different distortion patterns anyway.
Distortion values rarely play any role at bass frequencies. The small differences in distortion value numbers between the two incarnations shouldn´t play the major role in the decision process.
I prefer the Ridtahler-version simply because of the more pleasant optics and smaller built.

jauu
Calvin
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Old 2nd February 2009, 09:46 AM   #5
bvan is offline bvan  Denmark
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Thanks Calvin.

One thing I read mention of was the fact the the Linkwitz orientation reduces baffle vibrations, which may be beneficial if I sit my main speakers on top of the sub. What you think? cheers

B.

I also just found a quote by JohninCR saying he found the sound of the folded, ripole baffles to be inferior to flat or h-baffle, muddier sounding or something to that effect. The only slightly negative opinion of the ripoles I've dug up though. Hopefully he weighs in if he's still active here?
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Old 2nd February 2009, 01:08 PM   #6
Calvin is offline Calvin  Germany
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Hi,

both systems reduce vibrations. With the Linkwitz the drivers are ´in phase´ mechanically, but ´out of phase´ electrically. With the Ridtahlers its quite the other way round. But both work in push-push/pull-pull. So their mechanical forces cancel out.

There might be slight sonical differences between OB and folded dipoles, especially at the upper bandwidth limit. You shouldn´t use the typical Ridtahlers above ~200Hz, to stay far away from the chamber resonances.
Since the free air resonance drops considerably more with the Ridtahlers sonic differences to other dipoles might occur. The extended range towards the low end might sound to some as muddier. Another reason might simply be, that the thing they listened too was no really correct implementation of the Ridtahler-System (which is more often the case as most builders would like to admit). Taking some drivers off of the shelf putting them in a somehow folded small baffle results neither in a Linkwitz- nor a Ridtahler-dipole

jauu
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