Zaph ZRT - Bracing question (re: 'holes' in braces)

Monroe · 3rd January 2010, 02:40 AM

I am 90% of the way through building a Zaph ZRT: Zaph|Audio - ZRT - Revelator Tower

This speaker is a floorstanding two way ported design.

A friend built the cabinets for me out of baltic birch plywood, following the design on Zaph's site.

The braces/shelves have been ventilated, but the holes are not particularly large or numerous compared to most builds I have seen. The hole coverage area is perhaps 10%; see photo attached.

My question: Am I likely to have problems if I do not increase the number of holes in the braces?

I understand that the woofers have to see a certain air mass; would undersized holes in the braces change the effective volume/air mass? Would other problems arise?

The braces are not removable and it will be difficult to add more holes at this stage. Do I need to add more holes?

Thanks!

Andersonix · 3rd January 2010, 02:55 AM

I think you can get in there with a 3(?) inch diameter hole saw, as I think it's not open enough now. Or use the technique of drilling small holes around the perimeter of the holes you want, and then filing or sawing the rest.

DIFORCE · 3rd January 2010, 05:40 AM

I dont think it's enough ,the scanspeak moves alot of air

rabbitz · 3rd January 2010, 06:23 AM

You need to lose around 50% of the shelf brace material to allow good airflow. A shelf brace combines a cross brace and horizontal brace so needs material around the perimeter as well as a + in the centre to join the opposite panels in each direction.

If you can't do that then get a jigsaw or small handsaw and join the dots so the complete middle is open.

The 18W8531 does move quite a bit of air.

planet10 · 3rd January 2010, 07:12 AM

Make some holes. given their orientation... rabbitz 50% is probably a good target.

dave

Monroe · 3rd January 2010, 02:33 PM

Thanks! I will do my best to open them up.

What is the function of additional holes? Is a lot of air actually moving from one section to another, or am I simply allowing space for the waves to travel without being reflected back up?

Monroe · 4th January 2010, 03:23 AM

Also:

Are there any other improvements which I can make to the cabinet at this stage?

Right now, it has a lining of acoustic foam, and nothing else. I will be stuffing the cabinet at the bottom, per the plans.

Is there anything else that I can do to improve the cabinet? Other lining materials?

Volenti · 4th January 2010, 05:58 AM

Quote:

Originally Posted by Monroe

Thanks! I will do my best to open them up.

What is the function of additional holes? Is a lot of air actually moving from one section to another, or am I simply allowing space for the waves to travel without being reflected back up?

The way it is now you run the risk of having the "tuning" of the spaces+the holes (think of them as ports) effecting how the driver behaves, they become individual little resonant cavities instead of one big one that's tuned the way you intended.

rabbitz · 4th January 2010, 07:05 AM

The area of the brace is around 437cm² so 50% cut out would give around 218cm². This looks OK as is larger than the SD of the 18W which is 150cm².

I think the minimum required would be a bit more than the SD of the driver. However, a single large hole would work differently to several quite small holes so put more holes in than you actually need to make up the area.

I hope I haven't confused things.

Andersonix · 4th January 2010, 06:30 PM

Maybe you could work faster with a 90-degree chuck adapter thingy(?)

3rd January 2010, 02:40 AM	#1
Monroe diyAudio Member Join Date: Nov 2003 Location: Toronto, Canada	Zaph ZRT - Bracing question (re: 'holes' in braces) I am 90% of the way through building a Zaph ZRT: Zaph\|Audio - ZRT - Revelator Tower This speaker is a floorstanding two way ported design. A friend built the cabinets for me out of baltic birch plywood, following the design on Zaph's site. The braces/shelves have been ventilated, but the holes are not particularly large or numerous compared to most builds I have seen. The hole coverage area is perhaps 10%; see photo attached. My question: Am I likely to have problems if I do not increase the number of holes in the braces? I understand that the woofers have to see a certain air mass; would undersized holes in the braces change the effective volume/air mass? Would other problems arise? The braces are not removable and it will be difficult to add more holes at this stage. Do I need to add more holes? Thanks!

3rd January 2010, 07:12 AM	#5
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	Make some holes. given their orientation... rabbitz 50% is probably a good target. dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

4th January 2010, 07:05 AM	#9
rabbitz diyAudio Member Join Date: Jul 2003 Location: Newcastle, Australia	The area of the brace is around 437cm² so 50% cut out would give around 218cm². This looks OK as is larger than the SD of the 18W which is 150cm². I think the minimum required would be a bit more than the SD of the driver. However, a single large hole would work differently to several quite small holes so put more holes in than you actually need to make up the area. I hope I haven't confused things. __________________ No longer DIY active

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3rd January 2010, 02:55 AM	#2
Andersonix diyAudio Member Join Date: Jan 2004 Location: Silicon Valley	I think you can get in there with a 3(?) inch diameter hole saw, as I think it's not open enough now. Or use the technique of drilling small holes around the perimeter of the holes you want, and then filing or sawing the rest.

3rd January 2010, 05:40 AM	#3
DIFORCE diyAudio Member Join Date: May 2009	I dont think it's enough ,the scanspeak moves alot of air

3rd January 2010, 02:33 PM	#6
Monroe diyAudio Member Join Date: Nov 2003 Location: Toronto, Canada	Thanks! I will do my best to open them up. What is the function of additional holes? Is a lot of air actually moving from one section to another, or am I simply allowing space for the waves to travel without being reflected back up?

4th January 2010, 03:23 AM	#7
Monroe diyAudio Member Join Date: Nov 2003 Location: Toronto, Canada	Also: Are there any other improvements which I can make to the cabinet at this stage? Right now, it has a lining of acoustic foam, and nothing else. I will be stuffing the cabinet at the bottom, per the plans. Is there anything else that I can do to improve the cabinet? Other lining materials?

4th January 2010, 06:30 PM	#10
Andersonix diyAudio Member Join Date: Jan 2004 Location: Silicon Valley	Maybe you could work faster with a 90-degree chuck adapter thingy(?)

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