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In Reply to: RE: Mellow Monsters... posted by freddyi on August 31, 2007 at 20:38:08
Fred
A 70 Hz cutoff is unlikey, the larger 12" MM's roll off about 80 Hz with EVM 15B's crammed in, the small horn mouth being the limiting factor. You're correct, 70 or 80 Hz of horn bass is better than 40 Hz worth of direct radiator bass. Tom Danley demo'd his latest Unity rig without the sub, and it did a very convincing job with his fireworks recording with response down to 70 Hz. The 8" MM's got left behind back in the day, wish I still had em to measure. Check your mail for an MM8 appetizer.
Paul
Follow Ups:
Remembering the 70s... A friend of mine built a couple of sets of Mellow Monsters. Used the Jensen K-950 driver. Wonderful sound.
The ultimate was the combination of the Mellow Monster with a repro of the Dean Cornerless Corner Horn with a set of Jensen drivers and 4 way crossover. The Deans had the 15 inch driver, the monsters had the Jensen mid horn and dome/horn tweeter embedded in the cabinet along with the K-950...
Stacked in the corners of his beach house at Port Hueneme, CA, we could listen to the equivalent of a live Doors or Beachboys concert while sitting on the beach about a hundred feet from the house. That clean concert level impact driven by a single Kenwood integrated amp and Teac real to real...
thanks Paul -can a good MM12 set of mouth and path tradeoffs be built in "not much more" than 10 cubic foot bulk? FWIW Emience has competent 12" and Martin has one of their cast frame 12"coax w. 80oz slug for low cost
here's what I could pull from the email - thers a coupld of dimensions I couldn;'t read and it would hard to get them w/o destroying a magazine
how far off is MM8 from Olson's RCA 8" BLH? its snall - and I like 1-sheet wonders including one K loaded with 18
what are those three dimensions blurred on the left?
which 8" today might MM8 like?
Perspective view and parts locator
Beveled parts
Top View
Side View
Marking lines
Views and DimensionsBill Of Materials
Theory (part) And View
Assembly A
Assembly B
Assembly C&D
Cut Layout
I've got an old photocopy of the Mellow Monster plans, from the mid-1970's when I was in the Physics and Astronomy Explorer Post sponsored by the University of Arkansas at Little Rock. We built a pair of the 8" cabinets and installed some cheap Radio Shack Woofers (along with a Crossover, a metal Radio Shack Mid-Horn and metal Radio Shack Horn-Tweeter mounted in the mouth). The systems were amazingly efficient - we took them to the High School I was attending at the time, set them up outdoors, connected a Pioneer SX-750 (50W/Channel) Receiver, and they were audible more than 430 yards away up a hill, through some woods, and in an adjacent neighborhood at a friend's house. I think they're now in one of the Physics Lecture Halls at UALR.
The dimensions on the left side of that drawing are:
1-1/4"
20-1/8"
23-5/8"
Hope this helps!
Take Care,
David Baldock
Fred
Thanks for posting the enhanced pics, I did the scans in a hurry as I just got back in town. The smeared dimensions are (from top to bottom): 1 1/4"; 20 1/8"; 23 5/8". The resemblence to Olson's 8" RCA BLH is quite obvious, though Olson is not mentioned by the author of the article (Roald E. Dybvig, who was living in Minn. circa 1962)., probably because Olson's patent was issued just 22 years before this. The MM8 is indeed a member of the One Sheet Wonder Club, with just 4 sticks left over from a 4 X 8 sheet. This cab is a bit low for a coax, as it would need to be tilted back to aim the mids on an axis to the ears at the listening position. This is no problem in itself, but you could easily make the cab taller, and thereby make the horn mouth bigger, which would result in more bass extension. But it would'nt be a 1 sheet wonder anymore. Another idea would be to make the bottom plate hinged at the rear, so it could remain paralell to the floor as the cab is tilted back. You could then add some "skirts" to the sides to fill in the gap between the sides and bottom plate. The article shows the finished speaker on short legs, with a 60's mom standing next to it (Mrs. Dybvig?).
I've never heard the Emmie 8" coax, but their stuff looks good. Some of the Fostex stuff looks and sounds good for this application, especially a 2 way with one of the Fostex alnico tweeters on top. The MM12 checks in at less than 10 cu ft of bulk. Either the 8" or 12" MM's can be easily modified for larger drivers, I crammed EVM 15B's into my MM12's., though you would reach the point of diminishing returns (and space) sooner with the MM8. This is an easy cabinet to build, just a big box with some shelves inside, with the top "W" manifold being the only critical part. Areas for fine tuning would be the space behind the driver (making this smaller would raise the crossover point between the horn and direct radiator, which seems consistant at around 180 Hz between Olson's measurements and what I have seen with mine), and the size of the holes connecting the W manifold to the bottom S bend of the horn (making these smaller would attenuate the horn output).
Allright Mr. Questions, I've got one for you. If you put a MM8 in a room, steped outside and closed the door, and then cut a big K slot in the door, would the bass go lower? You'd need a "Stepford wife" to put up with this nonsense of course ; )
Paul
MORE QUESTIONS - how does one make MM12 at ~10 cubic foot or so? - got "plan"?does this top view of MM8 look correct? - anything missing? whats that number scrawled at the downfeed point?
that 3/4" throat gap don't look to scale
Hawkeye Fred
The MM12 cab measures out as 36" tall, 27" wide, and 15 1/2" deep, or 3' by 2.25' by 1.46', which comes out to 9.86 cu. ft. You posted the dimensional drgs. on this august forum a while back. I have full size plans for the top manifold (top down view), but I don't see this as all that necessary. If the miter cuts are'nt that accurate, you could "shlockmeister" the gaps tight with wood putty or silicone rubber, as this won't be visable inside the cab anyway.
You don't miss anything! The horn throat size should be 1 3/4", and not 3/4" as in the labeling of the drg. If you cut all the parts out as directed, you would run into this discrepency. Though it may seem obvious to us, a newby might be confused as to which is correct. In this case it's the scale drawing which is correct. While we're at it, the cleats pictured are scaled as 3/4" in the pic, but they are labeled as being 1". The "number" scrawled at the down feed point is just an ink smear from the printer of the magazine (!). Your hi-res scan makes it actually look like something. There's also some pencil jottings of no particular importance by my dad (which may show up in the gray scale scan of the e-mail, used so the photos would look viewable) along with some sweat stains too. Building horns is hard work!
Paul
(using your scan) - 10CF for MM12 = perfect size and should get some real horn sound. Do 12" MM that size play good solid clean jazz drumkit?I'm used to the dainty & infamous Karlson and only horns setup right now are K-horn) --sawdust and Elmers for my square joints which are like miter.
my drive burnt out and lost MM12 - have to look at it again
Freddy
Freddy
I thought that was a rhetorical question (or a test of my math skills) ; ) Here's the MM12 drg again (hope it does'nt get chopped off). The bass is quite solid and tight. From author Dybvig's comments from '62: "This type of enclosure gives the necessary bass reinforcement, and it does so 'musically'--its sound or timbre isn't 'boomy' like some bass-reflex enclosures or 'mushy' like some infinite-baffle types". I think he's too kind to the dynamiclly challenged direct radiator crowd, I would substitute "most" for "some" here.
Paul
Just running some sims (no resemblance reality) I am thinking
this horn is way too short, mouth and throat way too small.
Consequences seem to be large variance in response just above
the design cutoff frequency. Is this true in real life, and
if so, does it present any problem? Or does it just one of
those "sounds right, who cares what the measurements say"
kind of things...
K
I don't see the horn length as a particular problem (so by default it becomes an opportunity). The horn path is about 8 ft, and this should support 1/2 wave (max efficiency) performance to 70 Hz, and 1/4 wave performance to 35 Hz. The horn throat has to be constricted in this application because it's a horn/direct radiator hybrid. If the horn throat was sized for maximum effiency (using Keele's formula for instance) the horn output would overpower the direct radiator. The mouth size is the most limiting factor in this design, just making it a bit bigger will give lower bass extension. Back in the early 90's I tipped mine back and kludged together a bigger mouth with some boards and duct tape, with the result that bass performance was extended as measured by my primitive BSR RTA (a True Audio Confession! The exact numbers have to be taken with a grain of salt, but the trend has been verified later by better test eqpt. and techniques).
Response variances above bass cut-off (ripple) in your sim (Hornresp?) could be due to the driver you are specifying. An overdamped M.I. driver like the EVM 12L should minimize effects like this with the "motor braking" effect it has. How important this is is hard to say, as it's easy to hide stuff like this in the bass.
Paul
Nah, I just used some online thingimabopper... Ishtek?
And the parameters I sim'd were EV10M and Eminence
DeltaPro 12. Both drivers I own...I have no idea how accurate any sim is, nor how much a
folded horn without corner reflectors might vary from it.I am only posing a question, not questioning anyone's
expertise cept my own. I havn't actually built anything
but plain vented cabinets with Bassbox5.0 pro. Please
don't get me to lying bout no horns.But soon maybe I can start lying about Karlsons...
K
We're just kicking around ideas here. The EVM 10 M should have no problems driving either of these designs. I've not seen any note-worthy ripple at the bottom end of my EVM 15B loaded MM 12 FWIW. Basic sims don't seem to be able account for the muffler effect of the top W manifold in designs of this type, however the upper limit of response out of the horn seems consistant at somewhere just below 200 Hz. Many of the Lowther type BLH's seem to show similar results. Adding corner reflectors to the manifold may get you some high freq. extension, but my feeling is that the crossover point between the direct radiator and horn should be as low as practical, as there will be some ripple at this point which will be less audible at lower frequencies. I once added some diagonal reflectors to the lower S bend of my MM12, and to my amazement found no difference in the freq. response from the horn. So reflectors in these designs may be counter productive (in the W) or unecessary (in the S) IMHO.
Paul
if U got chamber volume, throat area, path length, mouth area and estimation of airspace total (~6CF for MM8) I can crank a few drivers though AJ-Horn but onnly one of its curves will probably fit the airspace.
Karlson have "reverbration" - this is real good for some recordings and not so good for others - I don't think K15 had much problem with trax from Alan Parson's "Sound Check" (supposely unsweetened) - with C15CX nice on drums, sax, vocals and machine gun.
whats your sim's input and output look like? I might not be able to equal hornresp with AJ-Horn --- does cowboy engineering allow things which current simulators say are not good? - I almost bet some things come up "good" on simulator which will suck in real life
Freddy
Bruce Edgar has recounted the story of a bass horn he designed which had a resonance near the bottom end. Siming it in Hornresp did not show this resonance. He solved the problem by elevating the horn off the floor a bit. He later asked David McBean whether this resonance could be accomodated for in the sim, and was told it could'nt with a simple sim like Hornresp. The sim should be a point of departure, with some cowboy engineering expected to follow.
BTW correction time. I mentioned that the MM12 rolled off around 80 Hz. Actually it's the EVM 15B in free air which rolls off at 80 Hz, and for some reason this stuck in my mind. The stock MM12 cab, with EVM15B installed, goes down to 60 Hz from my recently viewed 90's notes . So your estimate of 70 Hz for the MM8 is entirely realistic. Sorry to doubt ya! Blame it on my 1947 Bionic Computer's analogue memory.
Here's the other MM12 drg in pennance
Paul
hey Paul - a strong and room filling 60 ain't shabby. Regarding dimsnenions on MM12 (and MM8), is the drawing of the manifold close enough to scale to derive the baffle panel lengths?
how do you think MM12 would compete with the popular ~8 cubic foot BLH seen for various Fostex? - (those simulate to ~42Hz)
here's a preview of what I have from your MM posts - would you have any MM12 dims for the manifold to help fill in things?
a Karlson @7.73 CF is probably F3 around 60 or a bit lower half-space and will play pretty damned loud without a lot of cone movement.
RCA-Fan is kinda like Olson's "acoustic-son" so I'd like to see his views of these (once) fairly well-known designs.
I didn't initially mean to take out some of the sentimental stuff when cleaning up a couple of the scans - just a cheapass and trying to get something which would print w/o a lot of ink.
Freddy
Mellow Monster 12 - general view
Mellow Monster 12 top view
Mellow Monster side and top views
*********************
Mellow Monster 8 - general view
Mellow Monster 8 top view
Mellow Monster 8 side view
Mellow Monster 8 sheet layout
Mellow Monster 8 baffles
On another forum Ivo showed me the Schamcks and is running one with an Eminence Kappa 12 and seems to like results
Schmacks PLANS
Ivo's comments and input needed to sim with hornresp
karlsonkab wrote:
would Schmacks like the following specs? ("some" fun in Karlson 12)
"Freddy, Hornresp will show. S1= 400 cm^2, L1= 285 cm, Exponential 30Hz. Then calculate mouth with wizard. Then finally add 19 L compression chamber and you are set. Good luck!"
Freddy
The W manifold baffle lengths are not really critical as long as they follow the general proportions of the drgs. The height of these baffles is quite critical however, because if one or more is too tall of short, the top plate will not fit or seal correctly. Looking at the two designs together, it's obvious that the author took some pains to maintain an expansion as much as possible by placing the baffles at differing angles to each other in MM8. In MM12 this seems to be abandoned. In fact Olson made no attempt to provide for an actual expansion in the 1940 patent, and used baffles in the manifold which were perpendicular to each other, providing a geodesic approximation of the exponential horn expansion.
MM12 vs. Fostex BLH? A tough call as I've only heard one of the Fostex BLH's, the one offered as a kit by Madisound (forgot the model #). The horn mouth looked a little small on the Fostex, but they sounded good. They were pushing a lot of power through them (PP K88 amp?) with the volume control at 3-4 o'clock. I would expect the MM12 to have more bottom end, with the Fostex having the edge in baffle step control with their narrow vertical profile. It would be interesting to hear them back to back.
As to dims of the baffles, proper use of a bevel guage and protractor used for saw set up, plus liberal applications of Swedish putty (sawdust mixed with Elmer's glue), should get you through any problems there. It's not like it has to look good inside unless you make the cabs out of clear plastic.
I've never heard a Karlson. One lone cab sans driver used to show up at a former yearly record sale here for $20. I'd buy it in a second now just to hear what all the fuss is about. From your comments and measurements here they certainly seem like contenders in the present context.
I'd like to hear RCA Fan's take on all this MM mania.
Your scans make the drgs look new! The mouse chews are gone from scan 1. Even the above ones with the sentimental stuff look better than life! I'm gonna retire the original mag to a plastic bag and use yours from now on. I don't quite get the 'ole man's pencil note about panel 8, it looks like 31 1/2". I'll have to ask him.
I think these designs have received more scrutiny here than ever before!
Paul
If its sitting on the floor, and there is no pressurized chamber
requiring a seal, why does it need a full bottom plate? Perhaps
there is enough wood here to get the tilt and/or height you are
looking for and still cut everything from one 4x8 sheet.
K
Yes, you could eliminate the bottom plate and then use the lumber to raise the cab up higher, however you then open up some other cans of worms (aka opportunities ala Nelson Pass). You would need to get a decent seal between the horn mouth and the floor, which could take the form of carpet, wood or concrete, or some combination of these, adding a wild card into th application. In addition to this, you would be eliminting some panel dampening. The large rear panel is the most likely to "sing", and leaving off the bottom plate increases this. You may wind up adding the bottom plate later on as a tweak. These are not insurmountable opportunities though. Looking at the cutting guide, there is still some opportunity for wood conservation. The first cut (which splits the 4 X 8 sheet) between panel 7 and 8, could be ended at less than the half way point which could make this area big enough for one of the skirts. More wood is availabe from the area where the 8'" baffle in pictured, enough for the other skirt. This keeps the whole thing in Fred's O.S.W. club. Whether this is important or not is up to the builder.
Paul
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