I generally really like the sound of my speakers but if I’m ultra critical I may be able to hear some coloration. This is really only audible to me on some spoken word on BBC on line radio where voices can sound a fraction like they’re in a tunnel. I am probably over stating this and it is also broadcast quality dependent of course. Its really difficult to pin point but for all their faults my previous Stirling LS3/6 BBC Ref didn’t seem to exhibit this to the quite the same extent. At least as far as I can remember.
My current 752 Freedom has one rear port and 3 front ones.
How would you go about trying to find out whether this is simply a result of the driver construction/xover or internal reflections through either the ports or the mid/bass unit itself?
If additional internal damping coild be the solution where would it most likely make sense and what material would be best?
Thank you
https://i.postimg.cc/YS9H51Mk/20230503_211023.jpg
https://i.postimg.cc/Qdb9gWdf/20230501_112519.jpg
My current 752 Freedom has one rear port and 3 front ones.
How would you go about trying to find out whether this is simply a result of the driver construction/xover or internal reflections through either the ports or the mid/bass unit itself?
If additional internal damping coild be the solution where would it most likely make sense and what material would be best?
Thank you
https://i.postimg.cc/YS9H51Mk/20230503_211023.jpg
https://i.postimg.cc/Qdb9gWdf/20230501_112519.jpg
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If you can measure simply set your mic in the port and sweep. Ideally only energy at resonance (bass!) should come out there but usually a lot of other things spurt out - its not good at all...
So not so much via the cone but probably rather from ports.
Ideas:
Good luck!
//
So not so much via the cone but probably rather from ports.
Ideas:
- close all ports and measure/listen to the speaker.
- cover the drivers somehow and measure/listen to the speaker.
Good luck!
//
Should that be hanging/covering just behind the mid/bass driver as to leave the ports completely unobstructed ie. a piece of felt perhaps 25 cm in length? Thanks
In my main monitors ( commercial) it hangs from top to bottom ( 75 cm) on whole width of box (50cm).
This loudspeakers are bass reflex too with a 'large'' (10cm diam) port on front.
This loudspeakers are bass reflex too with a 'large'' (10cm diam) port on front.
Ok, my answers had been very short, so a bit more info: there is two kind of absorbers for audio, pressure and velocity.
Pressure is most often located close to boundary, velocity away from them.
By using a thick felt material in hanging in the middle of box's depth you can 'tame' (a bit) low freq modes and you can really filter/attenuate the mid freq as they have to travel two time into the felt to come back to cone/port, add to that the increased travel distance and you have chance they will be far less audible in the end.
In my loudspeakers there is a bit more absorbing material used at the base of the box ( lower part) and it's there to lower a mode from box too.
Pressure is most often located close to boundary, velocity away from them.
By using a thick felt material in hanging in the middle of box's depth you can 'tame' (a bit) low freq modes and you can really filter/attenuate the mid freq as they have to travel two time into the felt to come back to cone/port, add to that the increased travel distance and you have chance they will be far less audible in the end.
In my loudspeakers there is a bit more absorbing material used at the base of the box ( lower part) and it's there to lower a mode from box too.
Blocking the front ports does not seem to make much change to spoken words. However, closing in near field, approx 1 meter makes voices sound beautifully textured and clear with none of the (very slight) 'boxiness' for lack of a better term, that I have at perhaps 2 meters distance.
I may have more of a room issue than the speakers themselves but can't be certain at this stage yet. I will further investigate and add some additional damping as suggested by krivium. It's easily reversible too if not needed.
Does anyone have any suggestions for a decent frequency sweep app for iphone which I can use without an external microphone?
I may have more of a room issue than the speakers themselves but can't be certain at this stage yet. I will further investigate and add some additional damping as suggested by krivium. It's easily reversible too if not needed.
Does anyone have any suggestions for a decent frequency sweep app for iphone which I can use without an external microphone?
Audio Tools can use the iPhone's mic or an external mic. LINK But you may need an external sweep source
To know if what you percieve as tunnel effect, did you have treble and bass eq on your amp to play with ?
To knowif it is the room placement, here the corner loading: after playing with the ports stuffing you can try to put one loudspeaker in the middle of the room or if little at 1 meter on the middle of the opposite wallin mono and check if the sound you dislike on voices is comming from the loudspeaker itself as well whatever the position in the room. I am not remembering Audax aerogel have that sort of sound while I never heard that particular iteration made for Mission.
To knowif it is the room placement, here the corner loading: after playing with the ports stuffing you can try to put one loudspeaker in the middle of the room or if little at 1 meter on the middle of the opposite wallin mono and check if the sound you dislike on voices is comming from the loudspeaker itself as well whatever the position in the room. I am not remembering Audax aerogel have that sort of sound while I never heard that particular iteration made for Mission.
usually correct damping a reflex box is: fixed foam of 3-5cm on all internal surfaces glued to the inside walls.
easy trick for taming vagabonding frequencies is glueing some piece of damping foam 5cm thick 25cm x 25cm onto the back of the mid bass driver, leaving out the ventilation through the magnet if it exists.
this 25 x25cm foam does wonders
easy trick for taming vagabonding frequencies is glueing some piece of damping foam 5cm thick 25cm x 25cm onto the back of the mid bass driver, leaving out the ventilation through the magnet if it exists.
this 25 x25cm foam does wonders
Thank you Freedom666. When you say 'foam' do you actually mean foam or felt? I guess it's mostly mids that can be converted to heat?
Open cell foam, same kind used for acoustic panels ( with pyramid shape or not). Must be open cell or it doesn't have any effect other than reducing internal volume and hence alignement of bass reflex tuning.
@crivium
I mean usual open cell foam sold for damping loudspeakers.
the clue is for good reflex function that the damping material cannot vibrate. It should be fixed.
Behind the driver a piece of it dampens in the middle of the box but is fixed, too.
I mean usual open cell foam sold for damping loudspeakers.
the clue is for good reflex function that the damping material cannot vibrate. It should be fixed.
Behind the driver a piece of it dampens in the middle of the box but is fixed, too.
I can garantee you it work very nice the way i described with felt hanging in middle of box.
Like Drummerman understood it is 'fixed' ( nailed) in place and doesn't really moove. But in that case where it's velocity absorber it's not really important as long as it's away from walls.
When it's pressure absorber indeed it is more important to stay located on or very close of boundary where it does have the most impact by 'absorbing' pressure thanks to open cell foam ( in fact transforming movement into heat).
For info the loudspeaker i own which use this are early 90's high end ( Technics SB-M2) which were used too as broadcast monitors in your own country Freedom666. 😉
And it's Krivium, not crivium ( i don't get notification if not accurate spelling).
Like Drummerman understood it is 'fixed' ( nailed) in place and doesn't really moove. But in that case where it's velocity absorber it's not really important as long as it's away from walls.
When it's pressure absorber indeed it is more important to stay located on or very close of boundary where it does have the most impact by 'absorbing' pressure thanks to open cell foam ( in fact transforming movement into heat).
For info the loudspeaker i own which use this are early 90's high end ( Technics SB-M2) which were used too as broadcast monitors in your own country Freedom666. 😉
And it's Krivium, not crivium ( i don't get notification if not accurate spelling).
I always liked transmission lines, especially ones pushing towards aperiodic, to “suck" the back wave down the line and thru ssuffienct damping material to largely remove the time-smeared backwave.
dave
dave