Author Topic: Mission Mv-8E speaker upgrade  (Read 1306 times)

Offline Orcish75

Mission Mv-8E speaker upgrade
« on: April 23, 2020, 12:25:57 PM »
Hi Everyone,

I did this project about a year ago, unfortunately work kept me busy in the evenings and didnít 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 Iíll post what I have. Sorry about that!  :facepalm:

I bought a pair of Mission Mv-8Eís 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 @Nchebe and setup the 5.1 in our lounge. The Mv-8Eís arenít 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 donít push them too hard theyíre pretty good.





A few months later, Nchebe let me know that one of the drivers in the speakers I lent him wasnít 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 wasnít 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-8Eís 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 doesnít make sense to me, for me itís always been one or the other. Being annoyed by being ďripped offĒ by Mission, Iím 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 6.25Ē driver, but the rim of the driver is around 5.5Ē. I experimented with a couple of 6.25Ē car audio drivers, but they were too big, they didnít 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 6Ē 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 wasnít really an option. The other problem with this driver is that it doesnít 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 canít 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 didnít want to use a craft knife as one slip could cut through the cone and it would be game over. Hmm, my idea didnít 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 canít 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 wasnít 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 wasnít looking forward to drilling holes through the centre of each speakerís 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 hadnít centred the driver properly when I put the shroud back on, but wasnít 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 didnít 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 didnít 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, theyíre 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.





Offline PsyCLown

Re: Mission Mv-8E speaker upgrade
« Reply #1 on: April 23, 2020, 12:54:36 PM »
So when are you building your own set of speakers from scratch? :D

Sounds as if you had some fun with this mod.

Sent from my Redmi Note 7 Pro using Tapatalk

Amps: Building 2x Geco Audio Vanguard amps
DSP: MiniDSP NanoAVR HDA & UMIK
Speakers:Some Paradigm floorstanders
Sub: JL Audio 13w7 in a sealed enclosure
Headphones: Beyerdynamic DT770 LE

Offline DRNB

Re: Mission Mv-8E speaker upgrade
« Reply #2 on: April 23, 2020, 01:37:53 PM »
Nice, I like the look of these drivers especially with the new dust caps.

Verdict:

The change was subtle but profound, the speakers didnít 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, theyíre no longer as bright as they were before and revealed far more detail.


Since you haven't really increased the surface area of the bass driver it is to be expected that the mode won't shake the house.
It would be interesting to see what the new F3 compared to the old is, and also how the sensitivities compared. My guess is perhaps a little lower, and so the sensitivity.
Limiting the mid/bass to mid only will have a few advantages as I see it. 1) The midrange is no longer pushed to the limits on x-max. So mid performance should increase. 2) If the lo/mid frequency is at the right point, floor bounce will be less of an issue.

If you're up for it you could also play around with a 2.5 way configuration with that driver combination. I actually think toying with a project like this might be very interesting and good learning curve. Maybe better than jumping into a complete DIY build from the word go.

 

"There is no shame in not knowing; the shame lies in not finding out." (Russian Proverb)

Offline Orcish75

Re: Mission Mv-8E speaker upgrade
« Reply #3 on: April 23, 2020, 02:43:14 PM »
Quote
So when are you building your own set of speakers from scratch? :D

I had planned to do exactly that during the lockdown, however, trying to do work and look after a 6 six year old and a 3 year old at the same time proved too challenging! :sweat:
All I've done so far is cut the boards and glued the back and sides together. I'm building them as experimental speakers for when we move the home theatre upstairs, consisting two 8" woofers, a 6.25" mid and a tweeter. It'll use the same 3 way crossover I used in the Missions. I'll also be building small-ish 2-way speakers for the surrounds and ATMOS using the rest of the 6" drivers I got for the Missions.

Quote
Sounds as if you had some fun with this mod.

Definitely!  ^-^ It ended up being a lot more work than I originally anticipated, but the results made it really worthwhile. The other cool aspect is that you learn a bit more each time you do a build.

Offline Orcish75

Re: Mission Mv-8E speaker upgrade
« Reply #4 on: April 23, 2020, 03:32:02 PM »
Quote
Nice, I like the look of these drivers especially with the new dust caps.

Thanks! :thumbs: They seem to be reasonably good drivers, particularly considering how cheap they were. They've got a decent Xmax and seem to have a low Qms, it's really easy to push the cone in with your fingers. I haven't found any T/S parameters for them yet, so doing any designs with them are gonna be interesting!

Quote
Since you haven't really increased the surface area of the bass driver it is to be expected that the mode won't shake the house.

Yup, for sure, fortunately the two 15" Targas doing sub-bass duty take care of that.

Quote
It would be interesting to see what the new F3 compared to the old is, and also how the sensitivities compared. My guess is perhaps a little lower, and so the sensitivity.

Subjectively, I think the F3 is a bit lower as the bass does seem to be a bit deeper. I'll whip out the AVR setup mic and do some measurements, fortunately I do still have the second pair of Missions so I can do a direct comparison. I haven't noticed a decrease in sensitivity, but the measurements will confirm that.

Quote
Limiting the mid/bass to mid only will have a few advantages as I see it. 1) The midrange is no longer pushed to the limits on x-max. So mid performance should increase. 2) If the lo/mid frequency is at the right point, floor bounce will be less of an issue.

Definitely makes sense, the improvement in the mids was significant and really unexpected.

Quote
If you're up for it you could also play around with a 2.5 way configuration with that driver combination. I actually think toying with a project like this might be very interesting and good learning curve. Maybe better than jumping into a complete DIY build from the word go.

Hmm, I've never considered a 2.5 way before, I was considering using 5 of them in a speaker, one as a mid and the other four in a parallel/series array doing bass duties. I'll definitely look up 2.5 way designs and check them out. Thanks for the heads up!  :thumbs:



Offline Nchebe

Re: Mission Mv-8E speaker upgrade
« Reply #5 on: April 24, 2020, 11:06:37 AM »
Yo Bro...

Can I have my speakers back now please...

 :rubhands:
 :giggle:

Offline Orcish75

Re: Mission Mv-8E speaker upgrade
« Reply #6 on: April 24, 2020, 11:17:52 AM »
 :giggle:

Hmm, don't think you really need them anymore, your Tannoys run circles around these Missions.

Offline Curlycat

Re: Mission Mv-8E speaker upgrade
« Reply #7 on: April 24, 2020, 11:33:31 AM »
What an interesting read. Thank you for posting. Well done.  :2thumbs:

Looking forward to your next build thread.

ďI have realized that the past and future are real illusions, that they exist in the present, which is what there is and all there is.Ē  Alan Watts

Offline Orcish75

Re: Mission Mv-8E speaker upgrade
« Reply #8 on: April 24, 2020, 12:37:25 PM »
Thanks Curlycat, much appreciated!  :thumbs:

Offline Orcish75


Offline bbe22

Re: Mission Mv-8E speaker upgrade
« Reply #10 on: April 26, 2020, 11:41:34 AM »
use Xover  as per link
Before spending good money rather measure or  have someone measure the current setup , lock down over soon , and get the X - over sorted properly :)

Offline adie

Re: Mission Mv-8E speaker upgrade
« Reply #11 on: April 26, 2020, 01:45:15 PM »
What an interesting read. Thank you for posting. Well done.  :2thumbs:

Looking forward to your next build thread.

+1.

Offline DRNB

Re: Mission Mv-8E speaker upgrade
« Reply #12 on: April 28, 2020, 08:59:59 AM »
@DRNB

For a 2.5 way build, would I use a standard 2 way crossover and connect the bass and mid driver to the woofer output or use a crossover in the link below?

https://www.aliexpress.com/item/32955210482.html?spm=a2g0o.detail.1000013.1.39e781be2Sr0hJ&gps-id=pcDetailBottomMoreThisSeller&scm=1007.14977.161853.0&scm_id=1007.14977.161853.0&scm-url=1007.14977.161853.0&pvid=704458fc-a0e2-4d19-9db2-e510ff056ea7&_t=gps-id:pcDetailBottomMoreThisSeller,scm-url:1007.14977.161853.0,pvid:704458fc-a0e2-4d19-9db2-e510ff056ea7,tpp_buckets:668%230%23131923%239_668%23808%237756%23625_668%23888%233325%233_668%232717%237561%23326

My first thoughts would be to use your old 2-way x-over for test purposes, with a large inductor (3 to 4 mH) on the bass only driver. Listen and decide if you like it. The difference would be more bass (louder not deeper), and more power handling. On second thought it doesn't seem like the old x-over will work for this test.
I agree to test first before buying. The one in the link seem to have the .5 way point a little high.
"There is no shame in not knowing; the shame lies in not finding out." (Russian Proverb)

Offline handsome

Re: Mission Mv-8E speaker upgrade
« Reply #13 on: April 28, 2020, 10:34:19 AM »
With the state of SAPO who knows when you will ever see the Aliexpress unit - it could be months? Wait for lockdown to end and get yourself a similar x-over from RSE Eleclectronics or one of the other local shops for cheaper. Meantime, use your original x-over and also try your new bass driver connected directly (bypassing the xover). Nice job!  :clap:

Offline Orcish75

Re: Mission Mv-8E speaker upgrade
« Reply #14 on: May 02, 2020, 08:59:21 PM »
use Xover  as per link
Before spending good money rather measure or  have someone measure the current setup , lock down over soon , and get the X - over sorted properly :)

Cool! I think I'm going to leave the Missions as is for now, they sounding pretty good for entry level speakers after the mods. I'll get a cheap 8" woofer and use one of my 6.25" car drivers I have lying around and build a box to experiment with a 2.5 way setup.