[JoshK]

I know, I know, send money.  But I have long been thinking, "wouldn't it be super cool if...."    So I had to share.  My idea for an RM50 using the same cabinet as the RM40, so that costs are maintained and shared across.  The baffle would just be different.  



5 mid panels, 8 or so FSTs side by side and the two 10s at the bottom.  The mids and FSTs would then be at ear level both sitting and standing.  It would be more line-array-ish.  No more ceiling bounce and midbass driver would be closer in near field.

[azryan]

The cost of the ribbons would probably totally imbalance the value/cost of the end result.
Also you'd get a lot of combing with the large space between driven area of the ribbons. Maybe if the ribbons could be placed a lot closer together -like a custom cropped top/bottom face plate.

Also, hardly more line array-ish than current designs. The only thing here is making that top octave act like a line, and the problems that crop up from doing that.

[Marbles]

Josh, the FST's are a lot more effecient than the midrange/woofers and need to be padded down with just one.  By adding additional ones, they would just have to be padded down that much more.

[JoshK]

Josh, the FST's are a lot more effecient than the midrange/woofers and need to be padded down with just one.  By adding additional ones, they would just have to be padded down that much more.

Not really as ribbons don't couple the way that domes do so you don't get an efficiency gain with an array of ribbons.

[JoshK]

The cost of the ribbons would probably totally imbalance the value/cost of the end result.
Also you'd get a lot of combing with the large space between driven area of the ribbons. Maybe if the ribbons could be placed a lot closer together -like a custom cropped top/bottom face plate.

Also, hardly more line array-ish than current designs. The only thing here is making that top octave act like a line, and the problems that crop up from doing that.

I didn't get specific but I was assuming that you would put the tweets as close together as possible.  You can take a look at creativesound.ca for pictures of the available faceplates and some are rectangular for this reason.  Of course, I think the JPS 5" ribbon would probably be a cool candidate in this case.  

Also how would it not be more line array since it would be from 200hz on up?

[azryan]

"-Not really as ribbons don't couple the way that domes do so you don't get an efficiency gain with an array of ribbons.-"

Depends on how you wire it. Both the ribbons and neos in the end have to be padded down to match the lowest output which is the woofer section.

An optimal revision IMO would be level matched drivers on all sections so no padding needed. That woofer section wolud be the tricky part to get it up as high as the rest.

"-I didn't get specific but I was assuming that you would put the tweets as close together as possible. You can take a look at creativesound.ca for pictures of the available faceplates and some are rectangular for this reason. Of course, I think the JPS 5" ribbon would probably be a cool candidate in this case.-"

Yeah, as close as possible. ow close is possible really is the key though. Those longer 5" ribbons would be a better choice it seems but you need a real tight gap to stop combing below 20kHz.

If the driver has a peak to counter the combing that works (which is how the Neo 8's in mine work).

"-Also how would it not be more line array since it would be from 200hz on up?-"

Since there is no current version of a VMPS RM-50 I was thinking the RM/X with it's line of neo panels. That how I meant only the top octave and a half would become a line in your version.

I'm not sure if you can call the Neo section in the 40's a true line. It's complicated -based on length of the line in relation to specific freq. it's playing.

[JoshK]

I see your point Ryan.  I just think it would be worth thinking about if no more.

I did read somewhere in a paper on line arrays how ribbon tweeters, because of their dipersion patterns, aren't very prone to combing.  Or that is wasn't a big deal if you were seated relatively near field.  I don't know for sure myself.

As far as what you said about the l-pad, it's going off topic, but it is my thread so I guess it doesn't matter, and I wanted to mention this.  As you may now know, I am soon to move into a house that I purchased.  I don't intend to move around in the near future like I had for the last few years.  So I intend to do something I have been thinking about for some time.  After a few months of having my system set up in my house, and when everything is really dialed in as I would want it, I am going to measure the L-pad's values and replace them with high quality resistors.  

I am not going to remove the L-pads, just unhook them, so if I ever move again or need to change something I can hook them back up and start over.  While I am in there, I am going to delete the toggles, like some of the dealers do now.    I also thought about moving the xo outside the speaker but I am not sure I will or not.  I will have to think it over.   I did think of a great way of doing it though, for VMPS owners or for Alphas/Other large speaker owners.

[maxwalrath]

I'm very curious to hear how that turns out Josh. I know it's a while away, but definitely let everyone know how that works out.

[Rory B.]

I think you could get away with two FST's or four spiral ribbons beside four ribbon mids, atop the two woofers. It would be like a tandem RM2 but with the line array design in mirror-imaged pairs with the tweeters inside and the mids outside. The tweeter line is not as long as the midrange line but is positioned at ear level. Dual 12" woofers, not the 10" woofers used (i think) in the RM40. The upper one is graphite and the bottom one is a WCF Megawoofer. 12" Slot-Loaded Passive Radiator (still can't figure out how it works) at the bottom, as always. (Though I remember seeing some earlier implementations with the slot-loaded radiator up at the top of the cabinet.)

We could build a prototype using Bohlender-Graebner panels but they don't extend deep enough and even then, we still wouldn't know how to do the slot-loaded passive radiator ( ). The 3.5-way design is intriguing though.

[James Romeyn]

[quote="JoshK Not really as ribbons don't couple the way that domes do so you don't get an efficiency gain with an array of ribbons.[/quote]

Above is true but only when the ribbons are open back dipolar, not closed back monopoles like Brian's.

Generally there seem to be some good goals here.  My idea: 2 to 4 6.5s allow higher 280Hz XO to mids ala RM30, much better coupling to the mids, site them on the front somewhere, but who knows where.  A side-firing 12Megawoofer (like the X) gets deeper bass than the 10s, by far.  4 or 5 mids in a straight line, on the front.  A line of 5-8 spiral tweeters next to the mids.  The HET is really overkill in multiples & as posted above would require too large a pad, & the spirals sound darn good anyway.

[JoshK]

Jim,
care to support that?  everything that I have read about the theory of line arrays would suggest otherwise.  I am not saying you are wrong but the evidence looks like it does.  Ribbon tweeters are usually closed back dipoles, the research paper used an example with a closed back ribbon tweeter.

[azryan]

JoshK,

"-As far as what you said about the l-pad, it's going off topic, but it is my thread so I guess it doesn't matter,-"

huh? I didn't say anything about L-pads in this thread. I mentioned padding down drivers which L-pads are 'part' of, but I wasn't going off topic? Maybe I mistake what you were writing.

Anyway...

"-I did read somewhere in a paper on line arrays how ribbon tweeters, because of their dipersion patterns, aren't very prone to combing.-"

Guess it's more a matter of the specific ribbons in question and a matter of plain fact what they end up doing rather than being 'prone' to do this or that.

Like jim mentioning a line of the spiral tweeters.... As they are now they have a large faceplate I think which would put them very very far apart from eachother (part of why I liked seeing a single ribbon replace the dual spiral design).

There's no reason that a diff. faceplate couldn't be made that let the driven area get a lot closer though.
That'd be a LOT of spirals though to make a line of any reasonable length.

Also the greater the distance the more the line will blend together so how well it works depends on your seat distance and 'nearfield' on a line source goes a lot farther than on a point source.

"-Ribbon tweeters are usually closed back dipoles,-"

'True' ribbons being pure Alum. need a transformer to up their Imp. and that trans. and side mounted magnets just creates the end result being a monopole driver. The ribbons themselves don't actually need to be monopole though.
The super narrow, super long Maggie ribbon is an open dipole.

IMO, the best solution here (I didn't say 'perfect') would be a matching ~3/4" tweeter planar. Size and SPL matched so you could easily fit the same number of treble planars to midrange planars which would allow any length line you wanted, leaving only the bass section as the 'tricky' part.


Rory,

"-I think you could get away with two FST's or four spiral ribbons beside four ribbon mids, atop the two woofers.-"

If you're not trying to make a line of ribbons there's no reason not to just use a single ribbon... 'cept maybe power handling, but since it's only doing the highest freq. taking so little power I wouldn't consider that a vaild reason for adding more upper treble planars.

[Enrico]

Maybe Josh's idea would solve the problem of the very limited vertical dispersion of the highest octaves. This annoys me from time to time with my 626s.

[Rory B.]

I definitely think that the woofers should be stepped up to 12" drivers. Four 6.5" drivers (in their own separate enclosure to prevent nasty interactions i.e. megawoofers go "thump" and hyper-extend the suspension of the 6.5's) could be used in the place of the graphite 12" woofer but then we can't do the cool 0.5-way Megawoofer like the RM40 has. The 6.5" drivers idea would allow there to be a less directional midbass, but aren't the mid-ribbons pretty directional to begin with? The only advantage to doing the four 6.5's would be that the crossover to the ribbon mid panels would sound more consistent and the 12" graphite woofer could be changed to a megawoofer to match the other 12" woofer (the result being that the bass loading would be more consistent). This with the 6.5" woofers could be an RM60, and the RM50 could just have the graphite 12" woofer with the Megawoofer, omitting the 6.5" drivers.

Which leads me to another question (to quote Herbert Simpson): How much does this monstrosity cost?  

Advertising slogan: "You thought the RM-40 was big? You haven't seen anything yet...Introducing the VMPS RM50 and RM60."

[JoshK]

Ryan,

I was replying to your comment about padding (specificially the L-pad portion) and I myself was taking it off topic, not saying you were.

I intended my concept speaker to use the FST, not the spirals.  I agree it would be difficult to use the spirals for many reasons.  

When I was talking about many/most ribbon tweeters being closed back, I didn't mean to say closed back dipoles, I meant to say closed back....I just mistyped.  

I think Jim meant something else when I re-read his post, and I think he misunderstood what I was getting at.  

I realize that the woofers are the drag on the sensitivity, and I personally am thinking of resolving this with active biamping and relating the input sensitivity of the amps to account for the difference.  We'll see if it can be done.  I just like the challenge.  This would do away with padding down the mids/tweets to the woofer level but it wouldn't do away with padding down the tweets to the mids level.

[Marbles]

Josh,

The parts cost would add $3000 to a pair of 40's.  In addition the cabinets would cost more because of more labor needed to cut the tweeter holes.

Wouldn't it cost about the same as an Elixir when everything is said and done?

Now if we could work to reduce the price of an Elixir....
Say start with a taller Rm-30 .....

[JoshK]

Well I guess I am just going to have to build it myself then.    Not to bash the RM/X, as the one time I heard it it was pretty damn good, but I just really don't like the idea of a point source tweeter with a line source midrange.  Particularly because evertime you change the relative height and seating position you are going to get a different time alignment between the two.  This might explain why some have commented on how hard it is to set up.

[azryan]

With the sealed neo/ribbon sections the cabinets are really just TALL subwoofer cabinets. A two piece cabinet version of the X would be totally conventional to build, not costing anywhere near the claimed cost of the current design, have the same exact driver layout and funtion of cut away baffle on the neo section and be fully veneerable rather than having to just be gloss black (which I personally wouldn't own from any company for not fitting with the look of my HT room).

I drew up the design several months ago, but god forbid anyone take me seriously right? I've shown it to people and no one could think of a reason why it couldn't work.
I could actually be a kit too IMO which I think Brian has said here that you couldn't build an X kit 'cuz of the cabinet that a DIY'er couldn't build.

Josh,

"-I realize that the woofers are the drag on the sensitivity, and I personally am thinking of resolving this with active biamping and relating the input sensitivity of the amps to account for the difference. We'll see if it can be done.-"

Sure it could be done. If you try it I'm sure you can do it. If you used a digital x-over you could do away with the internal x-over all together even and set the gain diff. for each section so NO padding at all. Just take 6 matching amp channels.
They could be of the same design but much lower powered ones for the neos and ribbons.

Rember too... the Neos play all of the midrange AND most of the treble/tweeter range. The ribbons are hardly 'tweeter' IMO in the conventional sense where they'd cover a third of the audible range or so in a typical speaker.
I tend to just say neos and ribbons instead of mids and tweeters 'cuz of this big diff.
Just babbling though.

[JoshK]

yeah I realize that....actually, you are partially reading my mind.  I'd love to make a tall array of Neo's flanked by a tall array of Fountek JP2.0 Ribbons (5") with a seperate towers for midbass/bass drivers.  If I can ever find out how to get my hands on a lot of the Neo drivers that might just be what I will do.

[Rory B.]

And...stepping up to 12" woofers from 10" woofers...?