Criteria for new speakers

Yes, Mine are similar to the Kensai in the approach to tuning principles (although the Rhapsody -3dB point occurs 15 Hz or so lower down). I think that a lot of manufacturers deliberately tune for a higher (hump" as this makes small boxes sound more impressive on first listen). I wasn't really suggesting that all attempts to lower the tuning point wouldn't work properly due to Fs, Qts etc, just that optimal (ie flat) tuning volume is dictated specifically by the Vas of the driver and it's Qts figures.

TDrivers will work in boxes generally speaking up to twice the volume or half the volume IF their Q characteristics allow a response which is neither too under-damped nor over-damped at those volume extremes. Generally a 25% tuning ratio applies (so if optimal volume is doubled, then tuning should be 25% lower...providing that it doesn't coincide with the driver's resonant frequency).

The effects of taking a smaller than optimal enclosure and also DROPPING the tuning frequency would be to create a much earlier roll-off point, although less steep a roll off; ie roll-off would start much higher up the frequency range so bass SPL drops and the speaker loses impact at certain frequencies.

Every designer though has their own particular preferences depending on what the end goal to be achieved is.

 

Reffc, when you talk about 'my speakers' does this mean you are a professional speaker designer? If so, would you please put a link to your website in you signature.

 

Yes, sorry. I have PM'd "Admin" on the subject.

 

Excellent.

We just like industry figures to have the 'trade' name applied beneath the username.

All in the trade are welcome here, so enjoy

 

I don't think 'Admin' counts as a username to send PMs. Just update your profile to add a signature with your business link, that should do. Feel free to post adverts and announcements in the trade area.

Edit: Oh I see you have added a signature to your profile, but oddly I can't see it on these previous posts does it only show on new ones or something?

The 'Reference Fidelio' speakers have a lot in common with Dev's new DIY project!

 

Many thanks Rob, appreciated.

 

Yes, just seems to be applied to new posts I think. The Fidelios were my first commercial loudspeaker, and the result of about 12 months planning and design. They're a very large floor-stander but I'm currently about to launch a new stand-mount design (the Rhapsody). Sorry for the thread-jack folks. I haven't seen Dev's DIY project I'm afraid but will look it up.

 

Interesting to learn about these design choices.

Your charts above prompted me to look out the same for my Audience 40s - which are fine but the wrong impedance for my Quad 306.

http://www.soundstagemagazine.com/measurements/dynaudio_audience40/

Using the supplied foam plug seems to improve the performance on paper as well.

 

The Dyns there seem like a good example of a higher tuning. You can see a slight rise in the response as it goes down towards 100Hz.

It's doing exactly what my plot above shows, only at a higher frequency.



Taking the port out of the equation with the bung you can see the response down to 100Hz goes flat(er).



You can see the tuning frequency in the impedance plot. A closed box will show a single big spike at the driver resonance (somewhere below 100Hz). A port will drop the impedance drastically at the tuning frequency, so what you see here is actually not two spikes as it appears, but one big resonance spike with a big dip in the middle caused by the port. That middle minimum point is the port tuning freq. Here it is about 60Hz.

The spike at 2KHz is the crossover network, but the peak doesn't accurately tell you the acoustical crossover point.



Porting has sometimes been tuned to flatten the resonance spike as best as possible, rather than focusing on the frequency response. I'm not really sure of the advantage doing that. Sometimes transmission lines are tuned that way. It will minimise driver excursion (movement) I suppose.