Mark Audio Alpair 11ms Nostromo build

Hi folks,

Just wanted to share my build of Alpair 11ms driver in the Nostromo mid size box. Box is Birch ply on sides and 3/4 magohony for the front, top, back and bottom. This was salvaged from some old bookcase shelve ring from the 60's.

Nostromo plans were super easy to follow, thanks Woden Design! The drivers are BIG. Love they chunky look and feel. They sounds great right out of the box. I was concerned about the 9-10k bump in the graph, but so far its seems fine for my 54 year old ears.... the high are detailed and spacious with out being harh. stero imaging is great and depth too. lots of detail, but not clinical.

bass is good, still breaking them in so playing light music at low volumes.

some questions:
I only had a 1.5" hole drill for the port. what should the port length be now that the diameter is a wee bit bigger ? (shorter im guessing, but not sure how to recalculate length)

Should the box inside have stuffing or felt or something else inside?

These drivers are on sale at Madisound and if you are looking for full range drivers, these seems like a great deal for the money.

take care,
Jeff
 

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Nice build.

Good to hear that the "9-10k" bump is not intrusive. I suppose a lot of it can be ameliorated by listening off axis. Don't know your room but if you are satisfied with the bass response I would leave it alone.

Do you have any other speakers that you could compare the 11MS to?
 
The other speakers I have are:
Dayton Audio RS100-8 4"
folcal Chorus 706
jbl LSR305

room is just a 10x12 office/bedroom hardwood floors. one big soft chair and some desks.

have not just put the alpairs up with the others....I'd liked to get more break in time. Right not I say they have a better smoother top end than all but maybe the focal speakers.

once I get them broken in and I finish the cabinets, I'll do a subject comparison....in living room, 15 x 20.

I might try a .14 or .15 inductor and see if rolling off around 8-9k on the alpairs has any positive effects...cheap and easy to try.

Jeff
 
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The 11MS seems an interesting driver. There's an attractiveness about the simplicity of a full range speaker in a compact box that should be able to it all. It even has baffle step compensation built into the freq response. The only thing that concerns me is the dip at 400Hz. Possibly, off axis, this dip isn't as pronounced. And I read that dips aren't really audible. It would be interesting to hear your experience with that as they break in.
 
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...this may be difficult to fully achieve now if the only access point is through the drive unit opening

The driver hole is fairly large. Even with a holey brace i don’t have problems getting inside to lay in precut pieces of felt -- It helps that there is a 45° chamfer on the inside of the cutout. Friction fit is often enuff but hot glue if you need to attach it more permanently,

The examples of lining materials are just that, there is lots of stuff from many sources that can be made to work. Natural felts of medium density are 1st look.

Reflex boxes are typically just lined so as not to change the apparent volume of the box (so as not to affect the tuning) and still kill a significant amount of what is happening in the box acoustically at higher frequencies. If what you have 2x as thick 3 opposing sides works too.

Nice build. Don’t be afraid of chamfering or doing a roundover on the vertical edges of the baffle. If you start listening you might not get a chance to work on them again for awhile ;^)

dave

PS: i have pinched your pictures.
 
Taking advice...remove drives from box, so as to finish them and not have them incomplete.

found ports tubes at hardware store. using watco polywipe...here are some pics.

btw- hooked the speakers up to an lm1875 amp and the bass was waaaay better than SMSL d-class amp....I think chip amps are next on the list to explore. I also took apart my JE land 2A3 and plan to build the RH84 v1 ....fun ahead.

take care,
Jeff
 

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here is the speaker completed. 3 coats poly wipe with sanding between 2 and 3.
with ports, lining and in living room, bass comes alive for sure. they sound very nice. some times a little forward ( i think that's the term). might play with eq or dsp to see if its worth tweaking. plays great on jazz, vocals, ambient and opera.

fun easy project. easy box and no fuss speakers. get'em while they are still on sale :)

nest to all Jef
 

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btw- hooked the speakers up to an lm1875 amp and the bass was waaaay better than SMSL d-class amp....I think chip amps are next on the list to explore. -------------
take care,
Jeff

I've never considered putting a 6.5" FR driver in such a "small" box. Thanks for opening my mind.

BTW, I use a SMSL D class amp to drive woofers in my WAF set up. I'd like to know which m1875 amp did you hear a marked difference in?? Cheers!
 
It's also closer to being a 5 3/4in driver rather than a 6 /12in if we key off Sd rather than basket diameter.

As Dave says, Fs, Vas & [effective] Q are what determine box volume rather than the driver size per se. The 11MS is a relatively flexible unit, but as far as conventional vented box loading is concerned, it doesn't require an especially large enclosure.
 
Great that you have them finished and are enjoying them. What sort of amp are you using to drive them? I ask because with my solid-state amp they were good but with my valve amp they are excellent (greater output impedance, running in class AB), in fact I'm currently constructing a new valve amp, pure class A, that may suit them even better. We will see.