Contemplating my next speaker design, what do you think?

[dlneubec]

Because of severely reduced funds these days, I'm contepmplating a project using drivers I already have on the shelf, but also drivers that are still available. I have a quad of RS180-8’s from my Mentor omni project that I can reuse. They are beat up a bit, but still useable.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-364

I picked up a pair of Morel MDM55 mid domes when they were on the DOTD a while back and think they would work quite well here.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=287-020

I also have a pair of Seas 22TAFCG tweeters from one of my first projects that can be recycled. This is an extremely clean small metal dome tweeter that should be great above 3khz.
http://www.madisound.com/catalog/product_info.php?products_id=1601

An alternative to the 22TAFG are a pair of RS28AS-4’s from my Mentor omni project that are gathering dust. Driver costs by today’s prices is a little over $400 for the pair and with crossovers should come in under $600/pair.

Paul Kittinger is working out a tapered TL for the RS180-8’s in a 56 liter (gross) cabinet with an F3 of around 37hz. The baffle is sloped at 10º to get in the ballpark of time alignment to a listening position of about 12’. The speaker is 9.5” wide and only about 41” tall, so it is rather diminutive for a floor standing 3-way. The main woofer box is deeper, about 20”, to get the additional volume. The MT baffle has 1.5” chamfers that taper out by the time it joins the main woofer box. Attached is a rendered concept of the speaker.

Just looking at the manufacturers data (no measurements taken at this time) I’m anticipating crossovers points in the 800-900hz and 3000-3500hz range. I would like to use lower order slopes were possible. Sensitivity should be in the mid to upper 80’s.

The project is nameless at this juncture.

What do you all think?

[Jed K.]

That should be a nice combo. I'm a big fan of all those drivers. Also, why not utilize the space behind the midrange for the RS180s? It looks a bit bulky from the side.

[dlneubec]

Hi Jed,

As you might have guessed, this was a concept that was originally targeted at an open backed mid design (dipole or open tube), but finances cancelled out that idea for now, so I just adapted that concept. I was actually going for a sort of short powerful look, but one with a small footprint from the front.

Below was the original open backed tube concept that I adapted this design from.

[Jed K.]

Interesting indeed. The tube transmission line concept reminds me of what Jim Salk is using in that new "HT4" speaker.

Using the MDM55 and the open back baffle styling is more function following form... so from an aesthetic standpoint of creating a stocky or athletic looking speaker, I think it works. It's just not my taste. It probably doesn't matter much though because the speaker will be viewed from the front most of the time anyway. The front looks great.

[maynardg]

Lower order slopes may mean a bit of stress on the MDM55's. They sound sweeter if you can avoid it.

[dlneubec]

Thank for the tip Manard. You certainly handled the MDM55 very well!

[brianpowers27]

Have you considered choosing xo slopes that would fit with a Dueland setup? I imagine that can be accomplished with your existing parts. John Marsh has a nice little writeup over at HTguide on this.

Only trouble is the AC alignment. I am guessing that it is relatively close as currently designed but I imagine you may need to align it as closely as possible. Also, will the second rs180 be a .5?

[Paul Carmody]

Well, the driver combo certainly sounds like a winner. My only complaint about the RS180 in a 3-way is that it just doesn't quite dig as deep as an 8" driver, no matter how I try.
I like the look of the cabinet (I had a few designs sketched up with very similar shape.), although the top baffle is too similar to your last speaker. What else can you come up with for the top? Some sort of inlay?

[Pete Schumacher ®]

Have you considered choosing xo slopes that would fit with a Dueland setup? I imagine that can be accomplished with your existing parts. John Marsh has a nice little writeup over at HTguide on this.

Only trouble is the AC alignment. I am guessing that it is relatively close as currently designed but I imagine you may need to align it as closely as possible. Also, will the second rs180 be a .5?

We used the Duelund topology in Paul K's Centilana. The MDM55 could easily handle that, especially with 800Hz on the low end.

The nice part about a Duelund over a straight second order is that the slopes move to 4th order as part of the design, and as such can be modified to meet small changes to acoustic centers. 2500Hz is a better target for the upper end though, allowing for more leeway in the AC. Another advantage is that the Duelund sums the mid with the woofer and tweeter overlap in-phase but down in amplitude. You take two 4th order slopes, woofer and tweeter, and sum them so that the crossover point is 12dB down from reference. The "knee region" is quite overdamped from your standard LR4, and looks more like LR2 over a small range. You then add the mid, in-phase with the woofer-tweeter region. The mid runs nearly 6dB below reference at the woofer/tweeter XO point, and fills in the midrange region. This allows for a very smooooooth power response. You can also get away with a much less sensitive mid.

[martyh]

Mr. Kittinger has ben a busy guy lately as he just designed a cabinet for Dirk and me. We're building a mass loaded, tapered quarter wave cabinet designed by Paul for a Tang Band W5-1685 and a Vifa XT25SC90. Dirk is designing the crossover and with any luck we'll have it for Iowa.

Go ahead, ask me if I have any idea what a 'mass loaded, tapered quarter wave' line is and what it does....

Gotta love the guys on this board!

[Froste]

Dan, I like the design and the use of "on hand" drivers. Looks like a cross betwween the BassLines & the ZDT3.5. I would like to see how a TL does with the 180s, I'm with Paul on the low bass of the RS180s, In my FCZ3.5s I could never get below about 38hz, but I was going to use them with Subs so all worked out well. Also on your slope of 10 degrees, when I did the math for my FCT3.8s (Flames), the slope should have been 10-12 degrees, however when I used a plum-bob to line up the drivers, a 5.5 degree angle is what I ended up using.

I do think these drivers should make a very nice sound. Luck.

Ed

[marvin]

Dan,

I don't know why I should make a suggestion about aesthetic design to you. You have always managed to make unusual designs look great!

Anyway, I like the front view, but could the side profile be improved by putting a "knee" just below the woofers to transition the front baffle to vertical? Then also make the rear panel vertical to parallel that lower front baffle "shin" and perhaps cover or eliminate that base extension on the rear?

Maybe that's too conventional for you

Marvin

[Pete Schumacher ®]

Hi Jed,

As you might have guessed, this was a concept that was originally targeted at an open backed mid design (dipole or open tube), but finances cancelled out that idea for now, so I just adapted that concept. I was actually going for a sort of short powerful look, but one with a small footprint from the front.

Below was the original open backed tube concept that I adapted this design from.

You do have a knack for flair, I'll say that!

How about running that RS180 Omni Style? Below 800Hz, its heading to omni territory anyway. Mount that small TM baffle above the woofer like you did in the HOSS.

Just a thought.

I'm sure it's going to sound great, as your efforts usually do.

[ttan98]

Dan,

Except for the tweeter you may like to consider building a open baffle throughout, ie the woofer mounted in either U or H frame. use twin 12" or 15" woofer to give you the bass response.BTW Nelson seems to get good results from Eminence Beta 12 in or 15 in on OB.

You will find the open baffle bass is very different to transmission line bass, it depends on your taste of course..

cheers.

[Mayhem13]

Personally, I'd like to see someone tackle a 'Walsh' type system and Dan would be just the man to pull it off! But Alas, none of your in stock drivers have an open enough basket. Oh well......i could only hope! I just ordered a pair of Peerless 8" HDS woofers to give it a try and was gonna start pulling your shirt once i had them in hand. I hope i can still count on you once this gets underway anyways.

[Pete Schumacher ®]

Dan,

Except for the tweeter you may like to consider building a open baffle throughout, ie the woofer mounted in either U or H frame. use twin 12" or 15" woofer to give you the bass response.BTW Nelson seems to get good results from Eminence Beta 12 in or 15 in on OB.

You will find the open baffle bass is very different to transmission line bass, it depends on your taste of course..

cheers.

Nice suggestion, but Dan only has budget for drivers on hand, the RS180s, MDM55 and a choice of small, but very good, tweeters.

Dan's done a couple of open baffle designs. Check out his thread on the BASSLINES for his latest effort. Nice, high sensitivity design too, something you'd like.

[Pete Schumacher ®]

Personally, I'd like to see someone tackle a 'Walsh' type system and Dan would be just the man to pull it off! But Alas, none of your in stock drivers have an open enough basket. Oh well......i could only hope! I just ordered a pair of Peerless 8" HDS woofers to give it a try and was gonna start pulling your shirt once i had them in hand. I hope i can still count on you once this gets underway anyways.

Doing a walsh is much more involved than simply inverting a regular cone woofer. The principle is different than a conventional dynamic driver.

If I recall correctly, the walsh motor causes a wavefront to propogate from the top of the cone to the bottom. The speed of sound in the diaphragm and its angle allow the sound emitted at the top of the driver and the bottom to leave in phase across the spectrum, for a cylindrical emission pattern.

Nice woofers!!!

[dlneubec]

Guys,

A Duelund alignment is a possibility, but I'm not sure that I see the Morel as a filler driver, or that the RS180/22tafg are the ideal drivers to anchor each end. I believe I've seen the MDM55 used from around 700 up to 5000hz or so successfully, so it seems counterintuitive to reduce its bandwith and contribution by making it a filler. We also know that the RS180 is limited on the top end and the 22tafg on the low end, so I'm not sure about doing a design where these two are only 12db down at their crossover points.

Do you disagree?

[dlneubec]

Personally, I'd like to see someone tackle a 'Walsh' type system and Dan would be just the man to pull it off! But Alas, none of your in stock drivers have an open enough basket. Oh well......i could only hope! I just ordered a pair of Peerless 8" HDS woofers to give it a try and was gonna start pulling your shirt once i had them in hand. I hope i can still count on you once this gets underway anyways.

I'll help in any way I can!

[dlneubec]

You know Paul, I start each design saying I to myself "I'm going to keep this one simpler and easier to build" and I always have ended up with something more complex.

I must resist the temptation this time!