Can anyone enlighted me re the science behind this design which has a conventional rear ported upper cabinet on top of an underneath stand. Five sided with a hole for further bass control out the rear. .
This make its look like a floorstanding speaker.
As their is no actual tube in the rerar hole this seems to be just an exit avenue for any booming from the above speaker. Their are suggestions to us a fom bung to control ? this. Is this correct ? and can it be improved upon?, Any suggestions or opinions appreciated as I have never actual been aware of anything like this.
First impression is that the main speaker box is quite solid and internally braced but the bottom (boom) box needs some bracing. Or is this the objective ? either way it seems a bit hit and miss.
D
This make its look like a floorstanding speaker.
As their is no actual tube in the rerar hole this seems to be just an exit avenue for any booming from the above speaker. Their are suggestions to us a fom bung to control ? this. Is this correct ? and can it be improved upon?, Any suggestions or opinions appreciated as I have never actual been aware of anything like this.
First impression is that the main speaker box is quite solid and internally braced but the bottom (boom) box needs some bracing. Or is this the objective ? either way it seems a bit hit and miss.
D
Was the idea that there was a plastic bung that you removed and poured in a specified amount of dry sand to stabilise the enclosure and improve bass tightness. The bung gets re fitted to prevent sand spillage.
Are the original bungs simply missing??
Are the original bungs simply missing??
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I read this:
The Mission M73 is the smaler version of the M74. With a slightly smaller body it has not two but one driver and, consequently, half the internal volume necessary for it to work. Therefore, the rest part of the body is, in fact, an improvised stand, the properties of which can be significantly improved by filling it with ballast, for which there is a removable lid at the rear.
The Mission M73 is the smaler version of the M74. With a slightly smaller body it has not two but one driver and, consequently, half the internal volume necessary for it to work. Therefore, the rest part of the body is, in fact, an improvised stand, the properties of which can be significantly improved by filling it with ballast, for which there is a removable lid at the rear.
raymondj and I are in agreement. The bottom section is simply acting as a stand. The working part of the speaker is the ported upper section. The hole in the lower section is there simply so you can add ballast to increase the mass of the enclosure and would normally be closed.
bottom empty portion od the mission speaker.
Well after several weeeks of experimenting ,audibly there is definitely an effect by the internal volume producing an almost tuned low frequency coming from that rear hole .
Please note I have also applied internal side wall bracing and wood glue liberally on those inside panels. Each of these mods has made a tiny difference and this has progressivlt improved indicidual note seperation and clarity on those lower notes.
This is a big surprise and sorry I did not take any measurements.
It certainly is better to have the hole bunged up to my surprise? ,so I assume th their is some internal secondary resonances from the upper speakers common walls. coming into play .
I have since applied Deflex panels to the speakers internals as well as sone bitumastic damping to the tweeters rear panel to great effect on clarity.
This is using hirez as a source. I have no low level CD.
Each of these experiments were given a small amount of time to settle in and I used the same reference material from complex large orchestral to simple guitar and organ pieces.
I may experiment further but I am now also considering turning these into a 3 way with larger sub woofer type speakers on side walls.
Starting with that large cutout hole as my port. This now has rounded edges.
Honestly could not tell a difference.
Well after several weeeks of experimenting ,audibly there is definitely an effect by the internal volume producing an almost tuned low frequency coming from that rear hole .
Please note I have also applied internal side wall bracing and wood glue liberally on those inside panels. Each of these mods has made a tiny difference and this has progressivlt improved indicidual note seperation and clarity on those lower notes.
This is a big surprise and sorry I did not take any measurements.
It certainly is better to have the hole bunged up to my surprise? ,so I assume th their is some internal secondary resonances from the upper speakers common walls. coming into play .
I have since applied Deflex panels to the speakers internals as well as sone bitumastic damping to the tweeters rear panel to great effect on clarity.
This is using hirez as a source. I have no low level CD.
Each of these experiments were given a small amount of time to settle in and I used the same reference material from complex large orchestral to simple guitar and organ pieces.
I may experiment further but I am now also considering turning these into a 3 way with larger sub woofer type speakers on side walls.
Starting with that large cutout hole as my port. This now has rounded edges.
Honestly could not tell a difference.
I'm surprised you didn't try filling the stand section with ballast as per the manufacturer's recommendations.
As you are aware, an empty lower section will introduce unwanted resonances which will colour the sound. Leaving an unplugged hole in the lower section will, as you have found, only communicate these resonances better to the room.
As you are aware, an empty lower section will introduce unwanted resonances which will colour the sound. Leaving an unplugged hole in the lower section will, as you have found, only communicate these resonances better to the room.
Hi Galu amd thanks .
I did make a token effort at using bagged (sausage type sand for a quick test prior to battening accross the bottom interior. ) Did not notice anything but physical movement of already heavy cabinets for a pensioner like me .So I used an ingenious method of gluing a base internal 3 x 1inch crosspiece using string and a small hole in base to do this and same method for rear panel. (quicker) ie fed wire through from exterior and located it internally and new the 2 x 1 inch battens pre glued into location.
I did have previous experience doing a Max Townshend special plaster for internal damping many many years ago on his speakers but they later became a problem as the absorbed water from the atmposphere and started smelling. So I was a bit reluctant to go to far that way living in a North West UK Location.
Yep the colourationwas interesting as slight adjustments to toe in and therefore reflections became noticable. (except when bunged) So it was all of interest.
More interesting was the change from polyester to Polypropylene 5.6 uf capacitor which sharpened up the seperation of bass notes. Improved clarity in mass male chorus and drums and cellos in large louder pieces ( Thats the reviewer in me coming out) These were well used and run in.
So poisting as it may be of interest and I will probably part fill the cavity with Long wool fibre next or varying chunks of foam. So you can see covid lockdown is having an effect south of the border from you ?.
I did make a token effort at using bagged (sausage type sand for a quick test prior to battening accross the bottom interior. ) Did not notice anything but physical movement of already heavy cabinets for a pensioner like me .So I used an ingenious method of gluing a base internal 3 x 1inch crosspiece using string and a small hole in base to do this and same method for rear panel. (quicker) ie fed wire through from exterior and located it internally and new the 2 x 1 inch battens pre glued into location.
I did have previous experience doing a Max Townshend special plaster for internal damping many many years ago on his speakers but they later became a problem as the absorbed water from the atmposphere and started smelling. So I was a bit reluctant to go to far that way living in a North West UK Location.
Yep the colourationwas interesting as slight adjustments to toe in and therefore reflections became noticable. (except when bunged) So it was all of interest.
More interesting was the change from polyester to Polypropylene 5.6 uf capacitor which sharpened up the seperation of bass notes. Improved clarity in mass male chorus and drums and cellos in large louder pieces ( Thats the reviewer in me coming out) These were well used and run in.
So poisting as it may be of interest and I will probably part fill the cavity with Long wool fibre next or varying chunks of foam. So you can see covid lockdown is having an effect south of the border from you ?.
Yes, sand filling would make moving the speaker rather hernia inducing! 😀
Battening will reduce vibrations of the wooden walls of the bottom section, so that's a plus.
Resonances may still be set up in the air in the empty chamber - producing colourations that could be particularly noticeable if you leave the opening unplugged.
I would certainly, as you suggest, try packing the lower chamber with an absorbent material - it could inexpensively be the stuffing from an old pillow or two! 🙂
P.S. There are no borders when it comes to that of which we must not speak. 🙁
Battening will reduce vibrations of the wooden walls of the bottom section, so that's a plus.
Resonances may still be set up in the air in the empty chamber - producing colourations that could be particularly noticeable if you leave the opening unplugged.
I would certainly, as you suggest, try packing the lower chamber with an absorbent material - it could inexpensively be the stuffing from an old pillow or two! 🙂
P.S. There are no borders when it comes to that of which we must not speak. 🙁
Interesting thoughts re that sound escape via rear opening and its been obviously there on all ported designs in some form or another to a small degree However most of it never gets out probably.
I personally also line and coat the reflex ports within the speaker itself but its near paranioa so |I was told.
Musings Ive had whilst I await each of my modifications giving them time to be analysed which is painfully slow especially when you change parts in the circuits. ie The very last four Vishay foil resistors going into a highly modified Rotel 980x Even though I know roughly know how these run in from 30 years of using them . .
I also had thought of doing a sonic recording from these internal empty spaces as this would not really be something to delay the next step. Its just fun.
I personally also consider the amount of battening to be part of the mass absorbtion of entirity of the speaker and previous test with the Volt Allegros from a Wilmslow audio design showed that to be very important. 10kilos a speaker added.
ps
As there are no unspeakable borders currently ,we may be heading up to Glasgow pre Xmas. Agggggh That Steps concert may have just ruined it.
I personally also line and coat the reflex ports within the speaker itself but its near paranioa so |I was told.
Musings Ive had whilst I await each of my modifications giving them time to be analysed which is painfully slow especially when you change parts in the circuits. ie The very last four Vishay foil resistors going into a highly modified Rotel 980x Even though I know roughly know how these run in from 30 years of using them . .
I also had thought of doing a sonic recording from these internal empty spaces as this would not really be something to delay the next step. Its just fun.
I personally also consider the amount of battening to be part of the mass absorbtion of entirity of the speaker and previous test with the Volt Allegros from a Wilmslow audio design showed that to be very important. 10kilos a speaker added.
ps
As there are no unspeakable borders currently ,we may be heading up to Glasgow pre Xmas. Agggggh That Steps concert may have just ruined it.