Dynaudio 12" transmission line subwoofer - diyAudio
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Old 20th September 2012, 11:10 PM   #1
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Default Dynaudio 12" transmission line subwoofer

Hello

I have a single Dynaudio 30 W100 12" woofer that I'd like to use in a transmission line-type subwoofer. After playing around with the TL design software I've come up with this design. According to the simulation, it has a quite smooth response even without acoustic stuffing and a -6 dB point of approximately 20 Hz.
I'd be glad to receive some opinions and comments about this design.
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Last edited by d1030180; 21st September 2012 at 11:10 AM.
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Old 21st September 2012, 01:01 PM   #2
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Upon closer examination of the line geometry the inner volume of the enclosure would be closer to 350 liters, which is way beyond my size constraints. It seems like I would have to go with a sealed enclosure type with ~120..150 liters (if I'm to use this driver).
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Old 21st September 2012, 04:08 PM   #3
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by d1030180 View Post
Upon closer examination of the line geometry the inner volume of the enclosure would be closer to 350 liters, which is way beyond my size constraints. It seems like I would have to go with a sealed enclosure type with ~120..150 liters (if I'm to use this driver).
Hi,

Other options:

b
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Old 21st September 2012, 06:34 PM   #4
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Hi

You defenately need a lots of stuffing!
Try 80" long pipe, sd 10>>1 taper ratio.

80" is long enough for 25Hz, if taper ratio is big enough.

VP
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Old 24th September 2012, 07:31 PM   #5
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Quote:
Originally Posted by bjorno View Post
Hi,

Other options:

b
Thanks for your suggestion!
Does your simulation show that it would be possible to attain an f-3 dB of 15 Hz using this driver in some kind of a special enclosure (OD-T-TQWT)?

I also simulated this driver in an ordinary ported enclosure by varying the tuning frequency. The yellow tuning produces a rounded response curve, but nothing like an f-3 dB of 15 Hz.
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File Type: png 1-fr.png (35.0 KB, 153 views)
File Type: png 2-gd.png (35.2 KB, 43 views)
File Type: png 3-mp.png (32.9 KB, 20 views)
File Type: png 4-ms.png (33.7 KB, 22 views)
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Old 25th September 2012, 06:41 PM   #6
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by d1030180 View Post
..Does your simulation show that it would be possible to attain an f-3 dB of 15 Hz using this driver in some kind of a special enclosure (OD-T-TQWT)?

I also simulated this driver in an ordinary ported enclosure by varying the tuning frequency. The yellow tuning produces a rounded response curve, but nothing like an f-3 dB of 15 Hz.
Hi d1030180,

Yes I prefer a T-TQWT or TQWP for the very low end. Search my contributions in various thereads I you will probably understand why.

A continuously variable 2nd to 4th order HPF from ~ 10 Hz-40 Hz to protect the driver from over-excursions is IMO handy when listening to demanding music using an relatively low xmax driver like the Dynaudio 30 W100.

b
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Old 29th September 2012, 08:13 AM   #7
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I will build the enclosure from 18 mm plywood and wish to add three horizontal panels and some additional slabs inside the enclosure for bracing.

As the bracing panels will divide the enclosure into four partitions, are there any advantages in cutting three of the horizontal panels into free-flowing "window braces", while making some kind of resistive port into the fourth panel. I have seen this kind of structure in the local loudspeaker manufacturer's subwoofer model seen on this website:
Google Translate

As the (unfortunately quite poorly translated) page mentions:
Quote:
Construction of the enclosure is closed, but the dual-chamber, a controlled leak in a partition wall.
Housing Principle improve bass response and dynamics control.
In the schematic drawing, "ylempi všlilevy" means the upper horizontal (resistive) bracing panel and "alempi všlilevy" the lower one.

Harri's design seems to be dividing the airspace V into approximately (1/3)*V for the upper enclosure and (2/3)*V for the lower. Does this kind of enclosure alignment have some advantages when used with woofers with certain T/S parameters (such as the Peerless SLS driver in the commercial design)?
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Old 29th September 2012, 07:50 PM   #8
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I have been busy with the build and it's progressing nicely. Three of the panels have been attached. I used support sticks, torx screws and plenty of wood glue on every joint, so the enclosure should end up being airtight.

In the end I might have to fix the backside wall by gluing & screwing it in from the outside.

There's not much information available regarding the design of a dual-chamber aperiodic enclosure and the Qts value of the driver is only around average, so I might choose a low-tuned vented alignment for this sub.
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File Type: jpg IMGP2933.jpg (144.4 KB, 74 views)
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Old 29th September 2012, 08:25 PM   #9
oshifis is offline oshifis  Hungary
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18 mm wall thichness is too little for a subwoofer of this size.
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Old 30th September 2012, 11:12 PM   #10
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Quote:
Originally Posted by oshifis View Post
18 mm wall thichness is too little for a subwoofer of this size.
I certainly hope not! I thought it would be quite OK with many bracing panels & sticks & triangles added inside the enclosure?

Here is a picture of one bracing panel glued and screwed, I didn't have enough time to finish installing the others on this weekend.

Hopefully I have some time to install the remaining panels next weekend! And also to add some triangular-shaped vertical braces.
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