[scorpion]

I would like to support MJK's view that no resonances will occur in this type of OB if proper dimensions are in place. This is the frequency response
of the left woofer and a nearfield measurement: (the woofer is pictured and described in 'the venetian blind' thread, http://www.audiocircle.com/index.php?topic=40594.0 ) The discussion of MJK is here: http://www.audiocircle.com/index.php?topic=32919.110 .



No visible resonances at all. There is a LP 48dB/octave filter at 1 kHz.

/Erling

[MJK]

Erling,

Excellent!  Something seems to be working out the way I visualize it behaving, a rare occurance.

I am in the process of measuring my Lowther OB with my new Praxis setup and verifying for myself what I thought was going on behind the baffle in this cavity. I have been slowed a little bit learning how to effectively use the Praxis software and a nagging back problem which limits my ability to move the speakers into position. Those speakers are heavy!

Martin

[Rudolf]

Erling,
I can´t see any picture - just the two links. What am I missing?

Rudolf

[scorpion]

Rudolf,

I can see my frequency picture if I am logged in or logged out. I will mail it to you.

/Erling

[scorpion]

Martin,

I think your statements are quite to the point. I have put woofers in U-baffles with top and N-baffles. In both
cases it is quite easy to hear and identify resonances above 100 Hz. Now, for this design I am confident of the performance long up
to over 300 Hz which will be about the highest frequency I would like to employ for woofers with some various speakers
to test.

And I should also say, bass performance with good chassis is excellent !

/Erling

[AJinFLA]

I would like to support MJK's view that no resonances will occur in this type of OB if proper dimensions are in place. This is the frequency response
of the left woofer and a nearfield measurement

You won't see the peak if by nearfield you mean a few cm from the driver.
Try repeating that measurement outdoors at 1m with the baffle raised in the air as high as possible.

cheers,

AJ

[scorpion]

AJinFLA,

Please look at this measurements by Linkwitz: http://www.linkwitzlab.com/proto.htm , mine are no worse.
And how did Sigfried recognized it ?

/Erling

[MJK]

AJ,

You won't see the peak if by nearfield you mean a few cm from the driver. Try repeating that measurement outdoors at 1m with the baffle raised in the air as high as possible.

I have always had very good luck measuring TLs near field to identify the standing wave resonances. It cleared a lot of other acoustic interactions so the peaks and nulls were clearly seen. I am not sure what your measurement method will achieve, the floor boundary will be gone so the baffle is now open top and bottom. I would think that would be even more non-resonant. It would also seem to be unrealistic for the intended use.

Martin

[scorpion]

Nearfield measurement will clearly identify resonances. What is missed is the low bass OB roll-off.

/Erling