Yes, the acoustic centers should be offset by several cm. I did expect that there would be a large change in frequency response, but there was very little, only 0,5 dB loss at 1700 Hz, indicating minimal phase difference. Therefore I didnt bother aligning the acoustic centers.
The positive effect of this push-pull arrangement is lower distortion and better sound. It does however not affect odd order distortion. To further reduce distortion, we must keep cone excursions as low as possible. Now the 5" mids hardly move, the 21" woofers dont either. It's the 8" midwoofers that's working hardest here. That can be improved by either adding more drivers, or to increase the XO a little bit. I will see if XO at 120-130 Hz works. Its also tempting to add a couple 8" above the 5" mids.... lets see. 🙂
but you don't already plan to lift you ceiling - in case you run out of available room height - no ?
😉
Michael
😉
Michael
Yeah
and after that - a lift platform for the chair to get the ear level right - LOL - seems we are awaiting even WILDER times here...😀
But seriously, very interesting that push pull is making an audible improvement - would not have thought so.
Thanks for sharing...
Michael
Why did you step away from the twin 12" Beyma's for this range? Also, you should be able to give the drivers some baffle without degrading dispersion.
Because I sold them and had a lot of the 8" from before.... 😛
"Some baffle" will be a lot of baffle to gain any significant SPL. I dont want baffles, I want nude drivers.
Since cone excursion in an OB increases 8 times when the frequency goes down one octave, there should be a lot to gain by increasing the XO just a little bit. As I said - will look into that.
Adding more drivers was just a wild thought.. dont think that will happen actually.
A couple of new pix... inside the H-baffles, and one showing the push-pull midrange.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Sorry guys! 😉Ow, come on Stig! You'd be letting us down!
😉
Did a little test today - moved the XO from 100 to 120 Hz. This reduced the excursion of the 8" woofer a lot - below half of what it was. So - what's easiest and cheapest? Four more woofers, or slightly higher XO ?😛
There's a lot to gain in moving the XO with OB's, since cone excursion is reduced by 8 times when the frequency is doubled (below the dipole peak). If 80 Hz requires 8 mm excursion, only 1 mm is required at 160 Hz.
Haven't bothered to test 100 vs 120 Hz XO yet..... later.
New pics of the room, both with and without listening chair:
New pics of the room, both with and without listening chair:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
have you thought of suspending the remote control instead of having the table? 🙂
nice stuff there! i like the shakespearean athmosphere from the clothes
nice stuff there! i like the shakespearean athmosphere from the clothes
That's rather a half-ended solution... the chair should really just be some wires on which to sit.
