Help with Adire 281 TL design

[trpltongue]

Hello all!

I've been lurking here for a while and recently registered. Of course, now I am hoping to lean on the experience of the folks here to help mw with a problem I've encountered.

I recently built the Adire Audio 281 speakers in a Transmission line version. The Adire 281's have been noted for their strong bass performance and have been considered a strong speaker for home theater as noted in this audioxpress review . Unfortunately, the pair I built have very poor bass response below 100hz, dropping off to -12db at 50hz. I've taken some measurements using RoomEq and my Radioshack SPL meter and they are shown below.

I'm not smart enough to diagnose the problem and was hoping to provide the forum with the relevant info to see if there's anything I can check / do. Any help or ideas would be greatly appreciated.

Thanks,

Russell

I've included the cabinet and crossover plans below.

281 cabinet
TL line stuffed with 24oz polyfill in 4.5" section, 18oz in 3.5" section, 6 oz in 3" section.



281 XO



281 TL (right channel measured in room ~3' away)
Solid Black line is RS SPL calibration line
Dotted black line is sound card calibration line
Blue line is corrected speaker line




Previous speaker (wharfedale modus 1.6 right channel measured in room ~3' away)
Solid Black line is RS SPL calibration line
Dotted black is sound card calibration line
Purple is corrected speaker line

[Shaun]

Hi Russel

How did you go about determining the box dimensions? Are you aware of Martin King's work on transmission lines?

[planet10]

Originally posted by Shaun
How did you go about determining the box dimensions?

Designed by Dan Wiggins using classic methodology.

dave

[Shaun]

Dan Wiggins... OK, check that. But what do you mean by "classical" methodology? Recently, that has become a swear word around these parts. Check the Clarity on Seas Thor Kit* thread, and you'll understand. Martin's spreadsheets come closest to predicting final as-built response.

One thing to inspect is the amount of stuffing inserted. Too much can overdamp the back wave. Try experimenting with removing some (or a lot).

Edit: *the action starts at post #10

[planet10]

Originally posted by Shaun
But what do you mean by "classical" methodology? Recently, that has become a swear word around these parts.

And i hope that i played a role in making that so Classic is what we were doing before Martin (and George) came along and showed how much more could be gotten out of a QW box.

MJK should always be consulted when doing a TL.

I've been chatting with Russell by eMail, and have made a few suggestions already in the hopes of saving him from having to start over on the boxes.

One of the problems is that they are very heavily stuffed (i haven't checked Russell's density calcs, been busy) and with them all closed up he has no way of pulling it out and playing.

dave

[Shaun]

Originally posted by planet10 And i hope that i played a role in making that so

Oops!

OK, you're on the ball. I did not notice that it was you who replied! LOL!

[GM]

Originally posted by trpltongue

I recently built the Adire Audio 281 speakers in a Transmission line version. The Adire 281's have been noted for their strong bass performance and have been considered a strong speaker for home theater as noted in this audioxpress review .[/IMG]

Greets!

Well, after browsing the assembly manual and review as well as doing an approximate sim using MJK's software, you got exactly what DW said you were getting, a ~anechoic response down to 35 Hz, i.e. a ~IB response in a relatively small cab. If you wanted the Kit281's potential strong bass response, then you should have built the vented version that was reviewed.

Note that this isn't a TL per se, but a Daline like the Seas Thor.

GM

[trpltongue]

Thanks to all for the great replies!

I have been working with Dave and Dan via email and as mentioned, I have no real ability to remove all the stuffing. Right now I have ~ 1.8lb/cuft of stuffing as per the 281 design manual. From speaking with Dave and Dan, that seems a bit overstuffed.


GM,

I am admittedly very new to TL design, but based on the descriptions of the vented and TL design, I thought the TL design would reach somewhat lower, flatter than the vented design:

Vented:
anechoic response to 45Hz with a box tuning of 28Hz
typical in-room extension into the 30hz range

TL:
anechoic response to 35hz with a line tuning of 37Hz
typical in-room extension to 28hz

Either way, I didn't expect such a sharp falloff at 100hz.

[trpltongue]

*edit to above

I just spoke with Dan and he informed me of where I was misunderstanding I thought that the TL would have a -3db response at the F3 of the driver, but Dan has informed me that the typical TL response is -10db at the F3 of the driver, which is spot on what I'm getting.

I will still try removing the stuffing from the first line section as much as possible and listening, but if all else fails I will try blocking the line terminus and porting the rear to see how it sounds.

Oh the joys of being a rookie

[Scottmoose]

Seems a rather strange design to me. Leaving aside the discontinuities, it seems over-long & lacking sufficient volume to get much useable LF gain. And that kind of stuffing density is excessive in the extreme IMO for almost any TL.

This is the cabinet with no damping applied, in the TL sections sheet & the drivers paralleled for the sake of the sim.