Flat FR, harsh sound???

[Klimon]

Hi,

I just measured the FR or a pair of vintage 12" fullrange drivers and removed the whizzer cones; result is a practically flat response up till about 3,5khz where it starts to roll-off (zobel pre-installed)

Strangely enough they sound very forward!

For the moment placement isn't very good, they're made for corner duty (the cabinets are aristocrats, sort of corner horns) which will augment bass and change subjective FR balance although I'm sure that won't be enough...

Does anyone have a clue what could be causing this harsh, thin, metallic, shouty sound and doesn't show up on the frequency response? Maybe something that'll show on a waterfall diagram?

Next step is to give them a few coats of dammar, then move on from there. My initial plan was to use the natural roll-off and coaxially install a pair of small tweeters at 4khz. If I can't get rid of the forwardness it'll have to add a coil to the woofer and lower the crossover....

I welcome any suggestions or explanations for this weird phenomenon

Simon

 

[Nortp]

It sounds to me like you are describing the effects of baffle loss. As the sound goes from a 2Pi to a 4 Pi space the lower frequencies experience a 6 dB loss, the frequency when this occurs depends on baffle geometry. The thin tinny sound might be because the lower frequencies are weak relative to the others due to baffle loss. You might consider trying a baffle step correction circuit. It's really just an inductor and resistor in parrallel that shelve down the higher frequencies to make them match the weaker lower frequencies.

 

[Klimon]

It sounds to me like you are describing the effects of baffle loss

That's it!!! thanks!

I hope I'll get away with less than 6db drop; read somewhere that a part of the bass output 'lost' in 4pi does return in reflection, certainly if I put these babies in their intended place: the corner! Bummer to go from 97 to 91 db with my 1.5W amps , still an easy solution

Simon