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Old 11th May 2011, 07:24 PM   #21
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Quote:
Originally Posted by planet10 View Post
Using 1/2" material about 4.4 litre including vent.

If you can stretch that a bit mMar-Kel70 works pretty well.

If you are intent on keeping it to 4ish litre i'd just leave it sealed.

dave
I really like the looks of the mMar-Kel70. Its just a little wider and maybe a bit too shallow. I was thinking of propping the front up a bit to keep it more on axis and bit more depth would give it better stability as well as looking sleeker on the desk.

I would assume making the cabinet narrower and deeper would through the slot port alignment all off? Would a conventional round port work in the same volume?
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Old 11th May 2011, 10:02 PM   #22
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I guess you could make it narrower and deeper. Issues you have to deal with are:

1/ you'd have to loose the champhers, and would be limited by the bezel size of the EL70/CHP.

2/ With the inside of the boxes closer to the driver, you will gain some chestiness/cupped sound in the midrange (our original prototypes were such and we had to widen them 10-15mm to minimize it)

3/ in the attachment i have illustrated the vent length. It is "L" shaped and you'd need to ensure the same length. I can imagine you might have to slope the back to gain sufficent breating room for the vent entrance.

4/ as long as the open part of the vent is the same, you are OK. ie take any width reduction out of the vent spacers not the vent.

No a round vent will not do the same job. The miniOnkens work because of the high ratio, high resistance vents.

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Old 11th May 2011, 10:19 PM   #23
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Hi I built some speakers based around the CHR-70 gen2 that get 75Hz (-3dB) in a 4L sealed enclosure by using the capacitor equalisation trick. Hence the roll off is steeper than a conventional sealed box but the corner frequancy lower:

Make a box with 4L internal volume like this:
System Pictures & Description
stuffing is quite heavy with all walls having 1.5" speakear stuffing blanket glued on on them (basicly fills the box but without squashing it).

then use this series network on the driver:
Mark Audio CHR-70 Application Thread

A closed box works better I think if sitting very close to the speaker (as the port is another radiation source with very poor group delay characteristics and you are sat very close) and allows a greater stuffing density allowing the front and back walls to be closer together giving a smaller footprint.
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Old 12th May 2011, 12:22 AM   #24
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Old 12th May 2011, 03:07 AM   #25
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For the sake of simplicity what about a more conventional round port vented cabinet? Re-working the mMar-Kel70 to a narrower cabinet might be kinda complicated and I wouldn't want to ruin the design.

These will at some point be paired with a sub so I can stuff the ports when that time comes but I would like to have a little more extension in the mean time. Or would I just be better off sealed using a capacitor to push the extension? If vented is a vialbe option what would be recommend for cabinet size and port?
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Old 12th May 2011, 04:58 AM   #26
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Quote:
Originally Posted by Operandi View Post
For the sake of simplicity what about a more conventional round port vented cabinet? Re-working the mMar-Kel70 to a narrower cabinet might be kinda complicated and I wouldn't want to ruin the design.
I couldn't bear the idea of a round port. And while i was at it i made it specific to the CHP-70

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File Type: gif Op-Slot-CHP-110511.gif (44.7 KB, 537 views)
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Old 12th May 2011, 07:31 AM   #27
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Originally Posted by planet10 View Post
I couldn't bear the idea of a round port. And while i was at it i made it specific to the CHP-70

dave
Wow, you just drew that up now? That was quick and looks great!

That’s pretty much the exact form factor I was looking for, I think that will work really well on the desk. Though when you say specific to the CHP-70 I assume that applies to the EL70 as well since that’s my only option currently?

Also what exactly are the benefits of the slot port over a round port? I always thought they were more or less variations of the same principle.
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Old 12th May 2011, 07:58 AM   #28
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Quote:
Originally Posted by Operandi View Post
Wow, you just drew that up now? That was quick and looks great!

That’s pretty much the exact form factor I was looking for, I think that will work really well on the desk. Though when you say specific to the CHP-70 I assume that applies to the EL70 as well since that’s my only option currently?

Also what exactly are the benefits of the slot port over a round port? I always thought they were more or less variations of the same principle.
As Dave said.

"No a round vent will not do the same job. The miniOnkens work because of the high ratio, high resistance vents."
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Old 12th May 2011, 09:00 AM   #29
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Quote:
Originally Posted by Operandi View Post
Though when you say specific to the CHP-70 I assume that applies to the EL70 as well since that’s my only option currently?
My bad. There are currently 2 threads going on pretty much the same subject, and i got you mixed up with the Spanish guy.

For EL70 the vent spacer shrinks to 20mm, and the length of the total length of the vent goes to 164mm. Holey brace needs to be adjusted for the EL70s double magnet as well.

I can also turn on the imperial units if you prefer to work in inches (drawing is rationalized for metric thou)

A note i didn't add is that for a dngle pair of speakers it is probably not practical (unless you have a lot of scraps) to do the baffle in 15mm if the rest of the box is 12mm. i'd build up the baffle with something like cork to get the 15mm (given the thickness of the EL70 bezel a 12 mm baffle with full rebate is likely not practical.

dave
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Old 12th May 2011, 01:30 PM   #30
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12mm baffle with EL70 is not to recommend. I have that and for my next project i will use either 15 or 18mm.
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