Resonant chambers in a TL design? MJK, or any other officiando...ANy input?

[mondogenerator]

To begin a long story, i have begun a project using Visaton drivers. To make inital design more simple i basically pawned the x-over from a kit design from Visaton.com for the 'Vib 130 TL' as i am using the same drivers.

I have designed a SBB4 ported box aligment design, and also using MJK's tables, another design utilising a tapered QW tube 10:1 ratio and tuning to about 45Hz.

Having revisited the visaton site out of curiosity more than anything i noticed that their design seems to have a low order roll off of aroung 6dB/octave starting at about 80Hz which although high, gives an f-10dB of around 30Hz and 20Hz at around -12dB which to me seems very good for a 5" driver. Further inspection revealed that i had mistaken two small chambers behind the bass driver, which are ported into the 'closed' end of the TL; as a coupling chamber from which the line starts.

Im assuming these to be resonant chambers, (although lower Q as they are filled with BAF), and since one is twice the volume of the other, resonating at octaves...

The only purpose i can ascribe these is to either cancel some harmonic peaking, or to fill a null, due to the sligtly minimal use of BAF in the line, and of pipe resonances due to the straight pipe topology...

ANy ideas? any opinions on the design? good or bad?

MJK?
scottmoose?

ANyone?

Thanks for sharing any input you guys may have on the matter.

[planet10]

The Germans seem quite fond of helmholz resonators to kill some of the objectional harmonics.

dave

[PeteMcK]

Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories
"Two internal Helmholtz resonators are in use directly behind the woofer as sound absorbers"

[mondogenerator]

Originally Posted by PeteMcK

Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories
"Two internal Helmholtz resonators are in use directly behind the woofer as sound absorbers"

LOL yes...well i thought id read it better this time but i obviously hadnt....umm ILL get my coat

[mondogenerator]

anyway my idiocy being obvious.....i would love to hear if anyone out there has BUILT this project, and their opinions, if any

[PeteMcK]

haven't built it, but I think I prefer BR over TL from an engineering POV, fewer resonances to deal with (although the FR graph on the Visaton site is attractive). Perhaps sim an EBS alignment? I suppose it depends on how much LF you want out of that small driver...

[mondogenerator]

Originally Posted by PeteMcK

haven't built it, but I think I prefer BR over TL from an engineering POV, fewer resonances to deal with (although the FR graph on the Visaton site is attractive). Perhaps sim an EBS alignment? I suppose it depends on how much LF you want out of that small driver...

well i did consider EBS but im not a fan of EQing if at all possible and unless i misunderstand, thats what EBS requires...isnt it?

And for what its worth i have already designed a SBB4 alignment for these drivers...i get about 11 litres tuned to 44 Hz which is darn good...but i guess im tempted into a more gentle roll off by some experiments into sealed boxes with these drivers at home...despite my reservations F3 was about 85Hz which isnt too bad for a 5" driver and surprised me. Hence the movement in thinking back to the visaton TL as it has a very smooth roll off

[mondogenerator]

Originally Posted by mondogenerator

well i did consider EBS but im not a fan of EQing if at all possible and unless i misunderstand, thats what EBS requires...isnt it?

And for what its worth i have already designed a SBB4 alignment for these drivers...i get about 11 litres tuned to 44 Hz which is darn good...but i guess im tempted into a more gentle roll off by some experiments into sealed boxes with these drivers at home...despite my reservations F3 was about 85Hz which isnt too bad for a 5" driver and surprised me. Hence the movement in thinking back to the visaton TL as it has a very smooth roll off

Also considered chebechev alignment for extended response...well slightly extended, but i have little knowledge about it except that the transient response isnt as good as other reflex alignments, and nowhere what i (could) expect from a TL and definatly expect from a sealed box, albeit with a higher F3.....

[rcw]

It may go down to 30Hz. the trouble is that it does not have enough output for you to hear it.
rcw.

[mondogenerator]

Originally Posted by rcw

It may go down to 30Hz. the trouble is that it does not have enough output for you to hear it.
rcw.

so are you telling me that 68dB@ 1 watt is inaudible?! yes it is a lossy near aperiodic TL with a low average eff. of 80-82dB but as far as im aware 68dB is quite audible

as i have also got a SBB4 box built and ready, a comparison would be interesting.