Hi Everyone,
I did this project about a year ago, unfortunately work kept me busy in the evenings and didn?t get round to posting it. I discovered the photos whilst deleting tons of crap off my phone that people have been sending during lockdown. It seems some of the photos are missing so I?ll post what I have. Sorry about that! :facepalm:
I bought a pair of Mission Mv-8E?s a while ago, they were going for a good price. I got a full 5.1 set about a month later for a silly bargain on Gumtree, the wife was NOT impressed! Anyway, I lent the first pair to my brother [member=22015]Nchebe[/member] and setup the 5.1 in our lounge. The Mv-8E?s aren?t bad, certainly decent for the price I paid, they do have rather bright mids and the bass is somewhat lacking, but as long as you don?t push them too hard they?re pretty good.
A few months later, Nchebe let me know that one of the drivers in the speakers I lent him wasn?t working. With Nchebe being an Electrical Engineer, I asked him to take the speaker apart and check if there was anything obvious wrong with the driver. He discovered that the braided wire had broken off the terminal and just re-soldered it back into place. He then decided to check that the bottom driver wasn?t about to fail in the same way and to his surprise, he discovered that the bottom driver turned out to be a passive driver. When he told me about it, I was also really surprised as the MV-8E?s have a decent sized rear firing port.
I know Mission knows a lot more about speaker design than I do, but having a passive driver and a reflex port just doesn?t make sense to me, for me it?s always been one or the other. Being annoyed by being ?ripped off? by Mission, I?m sure this was a cost saving decision not to use an active driver for the woofer so I decided to take matters into my own hands. The problem with this driver, it that the mounting holes line up for a 6.25? driver, but the rim of the driver is around 5.5?. I experimented with a couple of 6.25? car audio drivers, but they were too big, they didn?t fit in the hole. (This is one of the photos that went missing) :nfi:
I scoured the Internet for a driver that would be suitable, I found a Tang Band 6? high excursion driver that would be perfect! However, $40 plus $20 shipping seemed a bit steep, so I continued looking. I found these on AliExpress, which seem to be near clones of the Tang Band, and they were $9 including shipping, so I bought a bunch of them!
I also needed a couple of 3 way cross-overs, I found these on Aliexpress, $25 for a pair. They can handle 150W and have 12dB/oct for the woofer and tweeter and 6dB/oct for the mid range.
First thing I did when I received the drivers was to wire them up to my test jig and check that they actually worked, was a bit concerned because they were so cheap. Fortunately they all worked, no voice coil scratching on the magnet or duds. However, as soon as I drove them a bit harder, there was a very distinct chuffing sound coming from them. It happened with all the speakers, not just one or two of them. It appeared that the chuffing was coming from the four small holes near the base of the cone.
This was a problem because making those holes a bit bigger wasn?t really an option. The other problem with this driver is that it doesn?t have a hole through the centre of the magnet like most high excursion drives and sub woofers. This means that the air trapped under the dust cap can?t move in and out freely as the cone moves and thus pressure (and negative pressure) builds up in that region causing the chuffing. I decided to sacrifice one of the drivers to determine the best way to solve the problem.
Initially I decided to drill a hole through the centre of the magnet, but I would have to remove the dustcap in order to remove any chaff created by the drill bit. I got hold of an old credit card and sharpened the edge in order to get between the dustcap and cone and carefully cut the glue holding the two together. I didn?t want to use a craft knife as one slip could cut through the cone and it would be game over. Hmm, my idea didn?t work out too well!! There is a very fine plastic film on the cone and it just tore off the cone as I maneuvered the credit card. This was the end result:
Fortunately, the film tore towards the centre of the cone and not towards the edge. As I was lifting the dustcap off the cone, I noticed that the concave shaped dustcap was actually touching the former. (The former is raised a few mm from the bottom of the cone, just can?t see it very clearly in the pic). I then realised that the dustcap touching the former was probably the reason for the chuffing, not the four holes not being big enough. The air in the former and magnetic gap wasn?t able to escape easily as the cone moved. I immediately tested the speaker again without the dustcap and the chuffing was gone, so that definitely pointed to former/magnetic gap air being the culprit. I had a brainfart, before I drilled a hole through the centre, I decided to put the dustcap back on, but invert it so that it was convex rather than concave, thus giving plenty of space between the former and dustcap.
I tested the speaker again and lo and behold! The chuffing was gone! What a relief, I really wasn?t looking forward to drilling holes through the centre of each speaker?s magnets. I then ordered a bunch of convex dustcaps from AliExpress, I think it was $2 for four of them. :2thumbs:
While I was waiting for the dustcaps to arrive, I concentrated on getting the driver installed in the box. It turned out that the mounting holes on the driver were just too close to the centre of the driver to be able to mount it in the box. The screws had nothing to screw into. I had a couple of MDF shims made so that the driver would fit flush in the hole.
I glued the shim into place and let it dry. (Sorry, this was another lost pic) I then removed all the wiring and old 2 way cross-over and then installed the 3-way cross-over and new wiring. (Yet again, a lost pic) :sulky: I installed the driver and immediately tested it!
I realised I hadn?t centred the driver properly when I put the shroud back on, but wasn?t too fazed at this stage as I was going to remove the driver again once the new dustcaps arrived. The dustcaps arrived after a few weeks, I dismantled everything again and removed the old dustcap once more. I used a thin film of regular wood glue to stick the dustcap on, so it was easy to remove the second time around and didn?t damage the cone. I glued the new dustcap in place, paying a lot more attention to getting everything properly centred. The new dustcaps are about 2mm bigger than the old ones, so they covered up the tear marks on the cone perfectly.
Put the driver back in place, also making sure that it was centred properly this time.
Final result!
Verdict:
The change was subtle but profound, the speakers didn?t suddenly become bass monsters and shake the house. The bass definitely tightened up and had more control as well as being a bit deeper. Surprisingly, the biggest change was in the mids, they?re no longer as bright as they were before and revealed far more detail. One spot that really jumped out at me was the intro to Game of Thrones. I could hear the individual strings vibrating on the cello, not the muffled mess that was there before, real goose bump inducing stuff! Now I really understand what muddy means.
I changed back to the original speakers after listening to the modded ones for a while and could easily notice the difference. The modded ones are definitely a lot better, it was well worth the effort doing the mod. I was surprised that it made such a difference to the mids, clearly the original cross-over was crap.
I did this project about a year ago, unfortunately work kept me busy in the evenings and didn?t get round to posting it. I discovered the photos whilst deleting tons of crap off my phone that people have been sending during lockdown. It seems some of the photos are missing so I?ll post what I have. Sorry about that! :facepalm:
I bought a pair of Mission Mv-8E?s a while ago, they were going for a good price. I got a full 5.1 set about a month later for a silly bargain on Gumtree, the wife was NOT impressed! Anyway, I lent the first pair to my brother [member=22015]Nchebe[/member] and setup the 5.1 in our lounge. The Mv-8E?s aren?t bad, certainly decent for the price I paid, they do have rather bright mids and the bass is somewhat lacking, but as long as you don?t push them too hard they?re pretty good.
A few months later, Nchebe let me know that one of the drivers in the speakers I lent him wasn?t working. With Nchebe being an Electrical Engineer, I asked him to take the speaker apart and check if there was anything obvious wrong with the driver. He discovered that the braided wire had broken off the terminal and just re-soldered it back into place. He then decided to check that the bottom driver wasn?t about to fail in the same way and to his surprise, he discovered that the bottom driver turned out to be a passive driver. When he told me about it, I was also really surprised as the MV-8E?s have a decent sized rear firing port.
I know Mission knows a lot more about speaker design than I do, but having a passive driver and a reflex port just doesn?t make sense to me, for me it?s always been one or the other. Being annoyed by being ?ripped off? by Mission, I?m sure this was a cost saving decision not to use an active driver for the woofer so I decided to take matters into my own hands. The problem with this driver, it that the mounting holes line up for a 6.25? driver, but the rim of the driver is around 5.5?. I experimented with a couple of 6.25? car audio drivers, but they were too big, they didn?t fit in the hole. (This is one of the photos that went missing) :nfi:
I scoured the Internet for a driver that would be suitable, I found a Tang Band 6? high excursion driver that would be perfect! However, $40 plus $20 shipping seemed a bit steep, so I continued looking. I found these on AliExpress, which seem to be near clones of the Tang Band, and they were $9 including shipping, so I bought a bunch of them!
I also needed a couple of 3 way cross-overs, I found these on Aliexpress, $25 for a pair. They can handle 150W and have 12dB/oct for the woofer and tweeter and 6dB/oct for the mid range.
First thing I did when I received the drivers was to wire them up to my test jig and check that they actually worked, was a bit concerned because they were so cheap. Fortunately they all worked, no voice coil scratching on the magnet or duds. However, as soon as I drove them a bit harder, there was a very distinct chuffing sound coming from them. It happened with all the speakers, not just one or two of them. It appeared that the chuffing was coming from the four small holes near the base of the cone.
This was a problem because making those holes a bit bigger wasn?t really an option. The other problem with this driver is that it doesn?t have a hole through the centre of the magnet like most high excursion drives and sub woofers. This means that the air trapped under the dust cap can?t move in and out freely as the cone moves and thus pressure (and negative pressure) builds up in that region causing the chuffing. I decided to sacrifice one of the drivers to determine the best way to solve the problem.
Initially I decided to drill a hole through the centre of the magnet, but I would have to remove the dustcap in order to remove any chaff created by the drill bit. I got hold of an old credit card and sharpened the edge in order to get between the dustcap and cone and carefully cut the glue holding the two together. I didn?t want to use a craft knife as one slip could cut through the cone and it would be game over. Hmm, my idea didn?t work out too well!! There is a very fine plastic film on the cone and it just tore off the cone as I maneuvered the credit card. This was the end result:
Fortunately, the film tore towards the centre of the cone and not towards the edge. As I was lifting the dustcap off the cone, I noticed that the concave shaped dustcap was actually touching the former. (The former is raised a few mm from the bottom of the cone, just can?t see it very clearly in the pic). I then realised that the dustcap touching the former was probably the reason for the chuffing, not the four holes not being big enough. The air in the former and magnetic gap wasn?t able to escape easily as the cone moved. I immediately tested the speaker again without the dustcap and the chuffing was gone, so that definitely pointed to former/magnetic gap air being the culprit. I had a brainfart, before I drilled a hole through the centre, I decided to put the dustcap back on, but invert it so that it was convex rather than concave, thus giving plenty of space between the former and dustcap.
I tested the speaker again and lo and behold! The chuffing was gone! What a relief, I really wasn?t looking forward to drilling holes through the centre of each speaker?s magnets. I then ordered a bunch of convex dustcaps from AliExpress, I think it was $2 for four of them. :2thumbs:
While I was waiting for the dustcaps to arrive, I concentrated on getting the driver installed in the box. It turned out that the mounting holes on the driver were just too close to the centre of the driver to be able to mount it in the box. The screws had nothing to screw into. I had a couple of MDF shims made so that the driver would fit flush in the hole.
I glued the shim into place and let it dry. (Sorry, this was another lost pic) I then removed all the wiring and old 2 way cross-over and then installed the 3-way cross-over and new wiring. (Yet again, a lost pic) :sulky: I installed the driver and immediately tested it!
I realised I hadn?t centred the driver properly when I put the shroud back on, but wasn?t too fazed at this stage as I was going to remove the driver again once the new dustcaps arrived. The dustcaps arrived after a few weeks, I dismantled everything again and removed the old dustcap once more. I used a thin film of regular wood glue to stick the dustcap on, so it was easy to remove the second time around and didn?t damage the cone. I glued the new dustcap in place, paying a lot more attention to getting everything properly centred. The new dustcaps are about 2mm bigger than the old ones, so they covered up the tear marks on the cone perfectly.
Put the driver back in place, also making sure that it was centred properly this time.
Final result!
Verdict:
The change was subtle but profound, the speakers didn?t suddenly become bass monsters and shake the house. The bass definitely tightened up and had more control as well as being a bit deeper. Surprisingly, the biggest change was in the mids, they?re no longer as bright as they were before and revealed far more detail. One spot that really jumped out at me was the intro to Game of Thrones. I could hear the individual strings vibrating on the cello, not the muffled mess that was there before, real goose bump inducing stuff! Now I really understand what muddy means.
I changed back to the original speakers after listening to the modded ones for a while and could easily notice the difference. The modded ones are definitely a lot better, it was well worth the effort doing the mod. I was surprised that it made such a difference to the mids, clearly the original cross-over was crap.
