35 mm port tube for GR CHR-70 - diyAudio
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Old 25th January 2014, 12:18 AM   #1
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Default 35 mm port tube for GR CHR-70

Anyone aware of source for 35 mm port tube in US? Looking to make a Golden Ratio CHR-70 for my workshop. I just need the drivers and suitable material for ports. Could I get away with 1.5" pvc? Thanks.
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Old 25th January 2014, 09:20 PM   #2
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or you could convert to rectangular port / slot or even corner mounted triangle of equal area? (962mm^2 in this case)

I'm a big fan of slot ports, as seen in many of the boxes on commercial website listed in signature line - with a high enough aspect ratio, the slot can run full width (with dividing spacer if needed) , and all you need is a flat panel shelf
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Old 25th January 2014, 09:51 PM   #3
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http://p10hifi.net/FAL/downloads/Changing-Port-Size.pdf

dave
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Old 25th January 2014, 10:37 PM   #4
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Quote:
Originally Posted by bnorrish View Post
Looking to make a Golden Ratio CHR-70 for my workshop.
If that's the older box (2011 7.5L?), it doesn't look all that hot with the Gen.3 driver. I would just scale it up to 10L, and tune it to ~50Hz. Port would be 1.5" ID x 4.25" long.

jeff
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Old 25th January 2014, 11:11 PM   #5
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Default 35-mm port tube designed and made by Mark

Hi Guys,
I make a 35-mm (and a 25-mm) modular port tube system for Japan. It comes in self-sealing snap-fit sections, thus making pretty much any length needed. You can see it here:

?????-?????????????

I did offer this system to USA but Madisound said there's so many cheapo ports available, they weren't sure a more up-market looking system like mine would sell. Maybe we're wrong???

Cheers
Mark.
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Old 25th January 2014, 11:36 PM   #6
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Dave

Thanks for the info! Nice sheet.

Mark
If Madison stocked, I would order those ports with the drivers. The smallest they have is 2" (51 mm). I thought it was funny they had the plans, but not the ports available to build. If use Dave's formula and calculate correctly (miss my college HP RPN calculator) with a 2", I would need a length of 163 mm - longer than the depth of the Golden Ratio enclosure. Would not work so I would have to go elsewhere - sale lost!

For my workshop speakers, some scrap MDF and scrap PVC OK. In the house for wife acceptance factor, you want something nicer.

I would revisit selling with Madison and tell them one of their customers had to drive to Home Depot 20 miles each way because they did not stock. I could not find anyone stocking the 25 and 35 mm diameters you have.
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Old 25th January 2014, 11:44 PM   #7
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Personally i prefer PVC plumbing pipe to dedicated ports, but then it is not often i use them preferring the resistive effects of a slot vent.

Have you seen the Classic Golden Ratio CHR-Ken 70?

http://frugal-phile.com/boxlib/P10fr...Ken-301113.pdf

dave
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Old 25th January 2014, 11:45 PM   #8
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Quote:
Originally Posted by bnorrish View Post
I could not find anyone stocking the 25 and 35 mm diameters you have.
Largely because the US is officially Imperial and the rest of the world is metric.

dave
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Old 25th January 2014, 11:52 PM   #9
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Quote:
Originally Posted by vinylkid58 View Post
If that's the older box (2011 7.5L?), it doesn't look all that hot with the Gen.3 driver. I would just scale it up to 10L, and tune it to ~50Hz. Port would be 1.5" ID x 4.25" long.

jeff
I was looking at the CHR 70 Chamagne(?) plans on the MarkAudio website, Golden ratio bass reflex box design. That would not work well with Gen3?

I am open for suggestions/recommendations for my workshop. 14 ft wide x 11 ft deep. Bookshelf speakers - near field. I have nice scrap 18 mm baltic birch plywood I am looking to use up. The 4 largest pieces (330mm x 432mm) I could use for fronts and backs - these plans would utilize the wood I have on hand.

I am complete newb when it comes to speakers - fairly new with DIY Audio. Builit a Pass F-5, ACA, Pearl 2, DAC.

Thanks for the information.
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Old 25th January 2014, 11:54 PM   #10
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Originally Posted by planet10 View Post
Largely because the US is officially Imperial and the rest of the world is metric.

dave
Maybe - but I cannot find equivalent imperial 1" and 1 1/4" anywhere. Seems to be more the smaller size.
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