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Old 22nd January 2009, 04:40 PM   #11
Helmuth is offline Helmuth  Netherlands
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Quote:
What is the secondary port resonance of that BandPass Sub? How are you dealing with it? Very curious as I've had a similar design brewing in my head.
Hi RJ,

I do not understand your question. Or you are thinking of a vented bandpass.

This is a closed bandpass. See this figure. I have chosen a closed bandpass to get the impulse behaviour of a closed box. Because I think with a Q of 0,75 it is better controlled then a vented type.
Click the image to open in full size.

The plan.
Click the image to open in full size.
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Old 22nd January 2009, 05:30 PM   #12
RJ is offline RJ  United States
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In WinIsd under the vents tab, lower right is a box with the 1st resonance frequency. In Unibox I think it's called secondary port resonance. Sometimes these resonances have a very high spike and larger than the primary resonance. Also a 24 db plate amp might not dampen that spike enough, adding a lot of stuffing helps lower it.
If I had Microsoft Office installed I could probably post a graph.
I'll work on that later.
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Old 22nd January 2009, 06:12 PM   #13
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That is exactly the critical aspect of pipes

Sure Helmuth know it , anyway differents "profiles" of the pipe can help, ie flared/ exponential, etcetera. ( B&W have made big work in that sense in the Nautilus line).

Cheers,
Paolo
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Old 22nd January 2009, 06:44 PM   #14
Helmuth is offline Helmuth  Netherlands
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Quote:
In WinIsd under the vents tab, lower right is a box with the 1st resonance frequency. In Unibox I think it's called secondary port resonance. Sometimes these resonances have a very high spike and larger than the primary resonance.
you mean this one I do not think it is a problem this one is filtered


The TI100 port wants to resonate on 1.5kHz i did not notice a problem there but on 2.5khz there is some interference I want to deal with.

The wind noise is a bigger issue IMO.
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Old 23rd January 2009, 04:03 PM   #15
RJ is offline RJ  United States
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The resonance is high enough to be adequately filtered.
I've modeled quite a few woofera and quite a few had resonances as low as 200 to 500 hz.
Good job and very nice cabinet work.
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Old 23rd January 2009, 07:33 PM   #16
bastek is offline bastek  United States
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This design can sound really good, my BA Lynnfield 500L II use a bandpass enclosure with dual 6.5" woofers, and they produce deep and tight bass.

Click the image to open in full size.
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Old 23rd January 2009, 11:06 PM   #17
Helmuth is offline Helmuth  Netherlands
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Quote:
The resonance is high enough to be adequately filtered. I've modeled quite a few woofera and quite a few had resonances as low as 200 to 500 hz. Good job and very nice cabinet work.
About the cabinet. First I layed 8 parts next to each other. taped it to gather. Placed it vertical glue between the parts and roll it up.
Click the image to open in full size.

Look inside
Click the image to open in full size.

Click the image to open in full size.

Worked really quick the outside is already Formica with wood structure. And not expensive.
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Old 24th January 2009, 12:31 PM   #18
Helmuth is offline Helmuth  Netherlands
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More pictures of the manufaturing.

The bassreflex pipe rectangular 8,6cm x 8,6cm real FAT.

Click the image to open in full size.

See the face plate of 3mm witch will be covered with velours colour chocolate. One to cover the bass tube. And the other to sink the ribbon tweeter and cover also the basstube.

Click the image to open in full size.

Painted black with a little radius.
Click the image to open in full size.
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Old 24th January 2009, 01:06 PM   #19
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dear mine friend, 8,6x8,6 is not FAT, it is little!

In a bandpass the pipe must be really big, up to 50% of Sd in order to not have "wind"-turbolence from excessive air speed.

This is rilevant at high SPL, of course, so I assume you put in crises the Visatons before.........

friendly,
Paolo
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Old 24th January 2009, 01:11 PM   #20
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Quote:
Originally posted by bastek
This design can sound really good, my BA Lynnfield 500L II use a bandpass enclosure with dual 6.5" woofers, and they produce deep and tight bass.


Hi !

Oh, the nice Lynniefild project !

A friend of mine have another friend who has these speakers.
They sound quite accurate IMO. The bass is solid!
If I remember well the 5 1/4 " ( sealed) is crossed at 125 Hz.........

Cheers,
Paolo
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