placing the driver 1/3rd of the length down a TL

[Bill poster]

Sorry, I asked this question once before but I couldn't find the answer.

..does the overall length of the line stay the same if the driver is positioned along the line rather than at the beginning?

And if so, is the general bass extension the same?

Thanks

[Scottmoose]

Yes and yes, but depending on the damping you've added, you may get a little less gain at the pipe fundamental.

[Bill poster]

Fantastic. Thanks Scottmoose.
The other question is tuning- I read somewhere that you should tune the quarter wave length around 5 khz away from driver resonance..the prob is I can't remember if that is above or below the driver resonance! Mind you I doubt its easy to get it spot on anyway, too many factors involved..

[planet10]

Also keep in mind that the 1/3 number is only an approximation of the optimum Zd. Download Martin King's tables. One of the tables is of the ratios of offset depending on the geometry of the line.

dave

[Scottmoose]

There are no 'shoulds' in terms of Fp, though it's generally inadvisible to tune below 0.707 Fs. Martin's Alignment tables assume tuning to Fs for e.g., but there are a wide variety of alignments (technically infinite, although that doesn't mean they're any use) depending on what is desired.

[Bill poster]

Ah I see. I wanted to try the new chr 70 which has a 65 hz fs but has quite a high qt. I think it goes down to 45 hz pretty flat. In this case shd i still stick to just above Fs or take the quite high qts into consideration?

[Leonidas]

You can also sim it in "hornresp".
Put the driver between S1 and S2 , in "driver-arrangement"".
Take the "speakerwizard" and watch response changes.

[GM]

Originally Posted by Bill poster

.........or take the quite high qts into consideration?

I do. Good rule-of-thumb in today's T/S centric 'society':

Up to a ~0.707 Qts after any series resistance is accounted for: sim a T/S max flat alignment and make Fp whatever Fb it calcs.

Above this point, it's generally better to use Fp = Fs/Qts and definitely if it's a >1.0 Qts or you want the TL equivalent of a T/S max flat [AKA max flat impedance] alignment.

Works for me anyway. Try it both ways plus ignoring Qts, calculate them using MJK's Classic Alignment Tables, sim them in his software and let us know what you think.

GM

[GM]

Originally Posted by Leonidas

Put the driver between S1 and S2 , in "driver-arrangement"".

Hmm, you sure about this? My understanding is that the driver is centered at S2.

GM

[Leonidas]

GM : you'r right, I'm wrong :

Correction : Put driver between S1 and S3 = S2 .
(Was too fast in replying and didn't check ed what I said!!)