Rear mounting Altec MR-931-12 "Mantaray" Model 14 horns?

ICTWoody

No longer a junior member
Hey guys,

My friend Justin is going to have one of his guys (he owns a high-end finish carpentry company) start on the "top hats" for my Altec 614 cabinets tomorrow. He built my 614's. And my plan was to have the opening cut to rear mount the Model 14 horn in the cab... really for aesthetics to not see the black plastic flange. But today when he told me they were going to do them tomorrow I found myself worrying about the 3/4" baltic acting like some kind of a wave-guide on these horns messing them up? I believe Altec only ever front mounted them on the baffles of the Model 14 and 9842's. There is a raised "beauty rib" that is painted silver usually. I was going to have them make the opening so that would set in from behind to position the horn.

I just think they will look way way better rear mounted. Would a big 1/2" roundover, or 45deg chamfer on the opening be enough to mitigate any concern? I need some opinions from you guys with more knowledge than me.

Here's some pics for reference. Thanks in advance.

- Woody

46e0a46630ff05e5a1832f700c1f6850.jpgAltec-Lansing-Mr931-12-Mantaray-Constant-Directivity-Horns-Pair-_57.jpg
 

ICTWoody

No longer a junior member
They are going to match, and sit on top of these speakers. The 288's are sold and gone and the Eminence horns are 2" or 1.4" with the adapter. The 902/Mantaray with the 3000mhz crossover should work great.

- Woody

C5F8C5EF-3CFC-42FE-B50C-40F4A760DF75.jpeg
 
I suggest that you do not rear mount them. Some calculated acoustical engineering went into those, I wouldn’t want to alter the edges of the horns in any way. Just my 2 cents.

Edit: That said, you DO have a good eye for aesthetics and I wouldn’t want my suggestion to take away from your vision of how these should turn out. The change to sound or dispersion may be very minimal with a large beveled or rounded edge.

Fun project, looking forward to seeing how they turn out!
 
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ICTWoody

No longer a junior member
I suggest that you do not rear mount them. Some calculated acoustical engineering went into those, I wouldn’t want to alter the edges of the horns in any way. Just my 2 cents.

Fun project, looking forward to seeing how they turn out!

Ugh... but AESTHETICS! Haha... I was kinda figuring that. I guess I have about 24hrs to decide.

- Woody
 

ICTWoody

No longer a junior member
See my above edit 😀

Ha. I don't doubt there would be SOME measurable effect... but will my ears be able to hear it. I kinda doubt it. Rear mounted it would echo the look of the port hole. I think that would be cool. I might be willing to roll the dice and compromise with a 45deg chamfer. It would still match the overall aesthetic of the speakers angular looks since there isn't any other round-over-ing.

- Woody
 
I would think a 45 degree chamfer would at least mitigate some of the diffraction issues from mounting it on the inside of the baffle.

Ideally front mount, but a 45 degree chamfer would likely mitigate the audible issues, and it gives you the aesthetic result you desire.

You could ask him to make the hornt mount baffle removeable so you can try both.
 

ICTWoody

No longer a junior member
You could ask him to make the hornt mount baffle removeable so you can try both.

I thought about that... but I honestly don't see it being worth the effort and I really want them to match the 614s...

The reality is these probably aren't long-term keepers for me anyway. They are great. But they are kinda homeless in my loft. They are basically a tertiary system already and with a couple 604 projects waiting in the wings, they'll likely be sold within a year or two.

I agree the chamfer might be the best compromise that would have less of an audible affect on these horns than something like crappy room acoustics.

- Woody
 

ICTWoody

No longer a junior member
I would think a 45 degree chamfer would at least mitigate some of the diffraction issues from mounting it on the inside of the baffle.

Ideally front mount, but a 45 degree chamfer would likely mitigate the audible issues, and it gives you the aesthetic result you desire.

You could ask him to make the hornt mount baffle removeable so you can try both.

If it ever REALLY became an issue, which I doubt, it wouldn't be that hard to open up the opening and move them to front mount.

- Woody
 

Audionut

Next Round Is On Me
You can do one of three things; rear mount and put a 45° bevel on the front like you noted above, surface mount but recess a cut the thickness of the front of the horn so it sits flush or...rear mount and recess a cut on the backside of the baffle so it’s closer to the face and up to you whether you put an angle cut on the front edge like option one.
 

Audionut

Next Round Is On Me
You can do one of three things; rear mount and put a 45° bevel on the front like you noted above, surface mount but recess a cut the thickness of the front of the horn so it sits flush or...rear mount and recess a cut on the backside of the baffle so it’s closer to the face and up to you whether you put an angle cut on the front edge like option one.
Just another idea; on option number two you could then have the front baffle veneered, which would entomb the horn but then leave a cleaner appearance of just a horn opening (at the silver lip area).🤷‍♂️
 
Is it possible for your friend Justin to measure the flare/expansion angles of the horn? If yes, rear mount the horn and bevel the same angles to the front baffle to match. IMHO, maintaining the same horn expansion should maintain the original design intent.
 

ICTWoody

No longer a junior member
Just another idea; on option number two you could then have the front baffle veneered, which would entomb the horn but then leave a cleaner appearance of just a horn opening (at the silver lip area).🤷‍♂️

That had crossed my mind. As well as just making grills. But I need to be able to remove the horn to remove the driver as needed since there isn't a way to easily get to the nuts when it's installed.

I guess grills would be easy... hmmm...

- Woody
 

ICTWoody

No longer a junior member
Is it possible for your friend Justin to measure the flare/expansion angles of the horn? If yes, rear mount the horn and bevel the same angles to the front baffle to match. IMHO, maintaining the same horn expansion should maintain the original design intent.

I think the angles are too steep... it would leave very little material for the horn to be bolted to.

- Woody
 
If the horn is to be rear mounted, then, it's pretty straight forward to make some sort of bracket/frame to sandwich the horn flange and mount to the back of the baffle. This method does not require the existing horn mounting holes and will not be visible from the front.
 

ICTWoody

No longer a junior member
If the horn is to be rear mounted, then, it's pretty straight forward to make some sort of bracket/frame to sandwich the horn flange and mount to the back of the baffle. This method does not require the existing horn mounting holes and will not be visible from the front.

That's a good point. Could do a back frame that would be wide to reach out to the thicker material.

- Woody
 

ICTWoody

No longer a junior member
Rear mounting and a monocle mount to support the driver itself.

These horns aren't very deep. I don't see any need to support the CD. Even rear mounted the load is being transferred to the 6 screws in the flange mostly the same way as they would be front mounted. Big fender washers will be utilized.

- Woody
 

rogerfederer

Junior Member
if you are thinking you might sell in a year or 2, imagine explaining all this to your potential buyers. if they going to put down some serious coin for an altec setup they are probably more concerned with the sound. however, you have a great eye and i'm sure your rear mount vision would end up looking pretty cool.
 

ICTWoody

No longer a junior member
if you are thinking you might sell in a year or 2, imagine explaining all this to your potential buyers. if they going to put down some serious coin for an altec setup they are probably more concerned with the sound. however, you have a great eye and i'm sure your rear mount vision would end up looking pretty cool.

Haha... I'm just gonna sell them to some rich guy who thinks they will look cool in his man-cave.

Kidding.

I'm going to talk with my buddy tonight. When I get home from work and measure my horns, I THINK that the 45deg chamfer might allow rear mounting now, but ALSO provide adequate clearance if they needed to be moved to the front. I haven't ruled anything out yet.

I've also been thinking about grills today. If that is going to happen... then the mounting would be less of an aesthetic worry.

- Woody
 
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