Speaker Choice and Room Acoustics

**cjd** · 14 April 2005, 16:20 Thursday

If you are going with a sub, flat 40Hz extension should be more than adequate for a nice 60Hz crossover to the sub.

I haven't heard the Extremis so I really can't comment on that at all. The box they used is pretty significantly deep though.

I can say that for my own HT I am considering a 3-way setup with a smattering of various RS combos (RS28A/RS125 for tweet and mid, and probably a pair of RS180's for the CC and a single RS270 for the mains though maybe a pair of 180's, and who knows what for surrounds - maybe RS150 based though). Of course, there are plenty of excellent options out there with sooo many possible ways of combining.

In many respects a 3-way is probably not needed. I am considering that direction as well.

Also, dipole is probably less suited to front stage use though for surround it continues to have some pretty big benefits in certain situations. It really depends - the less well controlled your room, the more you may find some gains from dipole. Given the power requirements of HT, you'll be wanting monopole on the bass end though. I'm not convinced the things that make dipole so sweet are a gain in a HT.

My thoughts, at any rate.

C

**ThomasW** · 14 April 2005, 16:39 Thursday

The Avro's look intereting, but are also very large. The ExMotion 04 speakers also look interesting

Arvo's are roughly 8" taller 2" wider. And will play a hell of a lot louder with lower distortion. The ExMotion 04 speakers are a mixed bag, IMO any design should be all dipole or all monopole. That design only has a dipole mid. And I don't think it has enough midrange radiating area for HT. Might be fine for a small music only room

leaving them as just drywall affect my choice of traditional "box" speakers vs. open baffle diploes?

Not really. You will probably want to add acoustical room treatments to fine tune the performance after things are up and running

Viewing this project as essentially equal in cost to the Modula MTM, which would be preferred for a dedicated theater?

The Modula is a better choice.

do you guys have any future plans for high quality 2-way or 3-way speakers using expensive/exotic drivers?

What you see on the forum is it. We're sort of burning out creating new designs. Also what's already posted couldn't be improved upon unless there was a revolution in raw driver design

**Evil Twin** · 14 April 2005, 17:09 Thursday

Originally posted by ThomasW

What you see on the forum is it. We're sort of burning out creating new designs. Also what's already posted couldn't be improved upon unless there was a revolution in raw driver design

There is another.... the Saint-Saens... full dipole line array

... but not for the faint of heart or pocket book. If you have something less than an imperial budget to back up your dreams, you would do well to follow the completion of the Arvo Part (for music or HT in a room with space to spare) or the Modula MTMs/Cheap Trick upgrade. (incl. RS270 bass cabinet).

Really, for effortless dynamics and deeper bass (assuming full range without a sub), take a look at CJD's three way project. Just remember that to extract the best performance and minimal coloration from a monopole type system, you need room placement that isn't very different from typical dipole recommendations - look at Avalon's and George Cardas' recommendations.

Cardas Speaker Placement Guide

Attached Files

cardas-roomsetup.pdf (478.5 KB, 98 views)

**Captain Cojo** · 14 April 2005, 18:18 Thursday

Jon, am I blind? Where is the link for the RS 270 bass bin? Crossover tweeks? :??

**JonMarsh** · 14 April 2005, 20:40 Thursday

Originally posted by Captain Cojo

Jon, am I blind? Where is the link for the RS 270 bass bin? Crossover tweeks? :??

That's not posted yet, becuase it's another crossover and update; Brian Bunge and I were discussing this, and Chris joined the fun and sort of took over the three way development, and he and Brian split off in a slightly different direction, and I did the same, moving towards just an update of my X1 upper modules and crossovers, and doing a new bass cabinet.. I'm still doing an update but it will be using my X1 klone cabinets with new midwoofers (the new Peerless if they measure as I hope on distortion) and a cabinet with dual RS270s sealed.

Ya know, we have at times a little bit of a problem on the Mission Possible DIY forum, - it's reputed the two main moderators are a bit lax about stifling off topic discussion on various threads (to whit, this example...) and as a result there are some detailed discussions on some topics buried away in threads otherwise titled... the only way to find them is the search engine.

I'm surprised Lex doesn't get a real moderator in here some day, and clean up this mess...

:W

Till then, just use the search engine.

Also, the way it's gone, CJD and Brian are persuing RS150's now instead of the RS180's I envisioned (a little better dispersion, probably, in the upper mids), but it's a close call- both start to get into some energy storage issues, albeit mild ones, around 1.8 kHz, so I'd rather see a lower crossover. Which is why the Modula IV-1 is at 1400 Hz. And I like the greater Sd and Xmax of the RS180, plus I favor a lower crossover point- try to get most of the vocal range off the "bass guitar" driver. My original X1's had a 175 Hz nominal crossover- actually about the same as the Arvo. I like how that voices with program material.

~Jon

**Bent** · 14 April 2005, 20:52 Thursday

Jon, quick one here, as that's the second time today you mentioned energy storage...
is that just simply one of Newton's laws, "an object in motion tends to stay in motion and not behave like the ideal mid-woofer anymore"?

I'm sure that's what he he mant...

**Brian Bunge** · 14 April 2005, 21:42 Thursday

Jon,

I think your day job is causing you to hallucinate.

I never stated, or even considered, going with the 150's instead of the 180's. In fact, I have four of the 180's and four of the 270's sitting at my dad's shop just waiting for funds to become available to purchase the RS28's.

Now when the time comes I may go with Chris' idea of using the RS28/150 combo with dual 180's for the center channel but that's a ways away. As it is now, I'm not exactly sure where I'll be living in a few months so I don't even know if I'm going to have room for these big freakin' towers. Either way, I've got the MDF all cut (except for bracing) and waiting for me to find time to do cabinet assembly.

**Mark K** · 14 April 2005, 22:13 Thursday

Originally posted by Bent

Jon, quick one here, as that's the second time today you mentioned energy storage...
is that just simply one of Newton's laws, "an object in motion tends to stay in motion and not behave like the ideal mid-woofer anymore"?

I'm sure that's what he he mant...

Think of energy storage this way. All drivers are mechanical devices. They have mass. They have springs. (Now, it's not just the cone and surrounds-it gets more complex. When a cone breaks up, that to, can be thought of as a bunch of masses and springs, at least conceptually)

Anyway, these mass/spring devices can store energy in the form of resonances. That is, generally speaking, energy storage = resonance. You can see this on a waterfall or on the etc plots. And, in the case of a single loudspeaker unit, on a resolute FR curve.

Why is energy storage important? Because energy storage problems lead to distorted transients. If you want undistorted transients then you must have low energy storage/a flat FR. As an aside, there's all this nonsense on the net on "fast drivers" and what constitutes good transient performance, but the answer lies in low energy storage/a flat FR, period. TS, actual cone material, design, ribbons, blah, blah...are all somewhat secondary and less relevant.

That's a bit of a nutshell view. I keep meaning to write a primer on linear distortion, like my one on nonlinear distortion, but it just keeps getting put off.

**JonMarsh** · 14 April 2005, 22:30 Thursday

Originally posted by Brian Bunge

Jon,

I think your day job is causing you to hallucinate.

I never stated, or even considered, going with the 150's instead of the 180's. In fact, I have four of the 180's and four of the 270's sitting at my dad's shop just waiting for funds to become available to purchase the RS28's.

Now when the time comes I may go with Chris' idea of using the RS28/150 combo with dual 180's for the center channel but that's a ways away. As it is now, I'm not exactly sure where I'll be living in a few months so I don't even know if I'm going to have room for these big freakin' towers. Either way, I've got the MDF all cut (except for bracing) and waiting for me to find time to do cabinet assembly.

I think you're right; I KNOW my day job is making me bonkers.

Thanks for getting me straightend out... at least for today!

There's so much going on around at the guide, too, that between it and work it's starting to feel like drinking from a fire hose. I think my confusion arose from the collaboration you and Chris were doing, and not keeping your interests separate.

Let me know when you're closer to sorting out cutting wood and building crossovers, I'd like to work those ideas along the lines of what I have in mind (especially since you've got the RS180's) and see if it appeals to you...

I reviewed your original thread this evening- just a quick refresher...

I hope you can get back to these sooner that it sounds like you think you can... waiting is heck...

~Jon

**cjd** · 15 April 2005, 09:22 Friday

Jon: I have two three-ways cooking with different folks considering them.

RS270/RS180/RS28A (WWMTM) and RS225/RS150/??? (27TDFC or RS28A, WWMT)

No one has expressed much interest in the RS180/RS125/?? WWMT/WTMW (except Brian mentioning the CC). :P

I also have a MTM design posted (two actually, one with the shielded RS28A) with the RS150 and RS28A on my existing MTM page. ~1700 crossover now (should *really* help with off-axis for CC use) The shielded version has very little BSC since I suspect it'll usually be packed into a space where not much is needed.

C

**ThomasW** · 15 April 2005, 09:33 Friday

There is another.... the Saint-Saens... full dipole line array

This isn't a new design, we've been discussing aspects of this for YEARS! :wink:

**Eric S** · 15 April 2005, 10:15 Friday

Thanks for the input! I've not looked at the Avro Part project for a little while. Seems that it is progressing. I like the SS9800 tweeter and am curious to see how the RS28a compares...

I'm also glad to hear that there is a center channel planned! Like I said, I'm in no rush as there are still many, many project to finish before I start building speakers - so I have no problem waiting on the final specs for the Avro Part and matching center channel.

Eric

**Eric S** · 15 April 2005, 10:22 Friday

Originally posted by Evil Twin

Really, for effortless dynamics and deeper bass (assuming full range without a sub), take a look at CJD's three way project.

BTW, where can I find CJD's three way? I took a quick look around, but didn't find it...

Eric

**cjd** · 15 April 2005, 10:51 Friday

Originally posted by Eric S

BTW, where can I find CJD's three way? I took a quick look around, but didn't find it...

Eric

Which one? 270/180 or 225/150 (or 180/125 which isn't posted here - yet)

**Eric S** · 15 April 2005, 12:21 Friday

Duh :roll: The thread was started by Brian - I was looking for one started by Chris... Thanks, cjd!

**Brian Bunge** · 15 April 2005, 18:24 Friday

Jon,

As I said, I've got the basic cabinet panels cut. I just need to decide if I want to use 3/4" MDF for bracing or if I want to buy a couple of 2x5 sheets of 3/4" BB at $30 a pop. I'll probably end up going with the MDF...WAY cheaper!

All the materials are at my dad's shop (along with a couple of big table saws, 3-4 routers, drill presses, radial arm saw, etc) so I'll probably start assembling the cabinets in the next few weeks. So if you've got any ideas you want to run by me feel free to do so now. You can pm me if you want or post in my Dayton RS 3-way thread for everyone's benefit.

**Brian Bunge** · 18 April 2005, 18:26 Monday

Jon,

I just wanted to bump this up in case you missed my last post.

**JonMarsh** · 23 April 2005, 10:40 Saturday

What I wanted to do Brian was take a spin at the crossover for your design also, just to see how practical it might be using an approach more like Wilson Audio as regards the crossover frequency- which I prefer for reasons of voicing and instrumental seperation. The challenge might be maintaining an acceptable impedance as well as acceptable cost.

Unfortunately, I'm working mostly on company stuff this weekend, and reading and responding to posts and emails just in my "meals" breaks. Had a sit down with my boss Friday and he even admits they're way overscheduling me, partly because our other two apps engineers don't have the right mix of experience and background to handle some of the things that have popped up on their own (yeah, there just "kids" in their 30's). So I'm overbooked on my own stuff, and mentoring/co-authoring on other projects. Never a dull moment...

There's going to be a lot of "airplane" time in May, so I may have some free time for crossover tweakazoiding then.

~Jon

**Brian Bunge** · 23 April 2005, 10:49 Saturday

Jon,

That's what I figured you were talking about. Like I said, these are going to take me awhile so just get to it when you can. I really want to get the cabinets done and have the drivers measured in the cabinets before I finalize any XO stuff anyway so that gives you and Chris plenty of time to play around with them.

One thing I thought about doing to cut down on veneer costs is to simply veneer the sides and top and have the baffle and back painted gloss black like Pete did on those Avalanche subs. I think they might look pretty classy that way. I will have to find a local shop (or maybe a vocational school that'll do it for just the cost of the paint) that can do that kind of work. Or maybe Pete could do it for me?!

I wonder what shipping costs would be for that...

**JonMarsh** · 23 April 2005, 10:53 Saturday

That's a pretty reasonable idea, re the veneering and finishing. The backs of my M8ta will be black, not veneered.

What woods are you considering for veneering? If I wasn't a little tired of walnut (did WAY too much of that in the 70s), I'd just do my M8ta's in that, becuase it's so easy to get good veneer at pretty modest prices, including paper backed and solid. The veneer for one side wall in Rosewood costs more than doing the whole things in Walnut (I actually have the walnut on hand, too- silly me).

Pete does do great work- I don't have anywhere to work were I could do something that nice with paint.

**Saurav** · 23 April 2005, 12:10 Saturday

I'm glad you started this thread, because I need a lot of the same advice. Just got set up in the new place, and my stereo is now in a space that's 1/4 the size of the old room. However, I now have a 'music room' (it was in the living room before), so I can think about room treatments. I would really appreciate some advice on moving a system to a smaller room. The room is also almost a square, which will be a problem too. Anyway, the two main questions in my mind right now are:

* Dipoles and room placement and wall distance. The image that Evil Twin posted helps, and I'll read that article. My room isn't that rectangular though. Right now I have the speakers on the slightly longer wall, because that gives me more symmetrical walls on both sides (otherwise one speaker would have a window on the side and the other would have a closet). But in general, what should I be trying to do? The imaging/soundstage is too diffuse right now, which is probably because the reflected sound is going everywhere and is arriving too close in time to the direct sound, since the speakers are much closer to the walls. Will absorption/diffusion help? Behind and to the sides?

* Right now only my midrange is dipole. I've been thinking of trying a dipole woofer for a while now. Will a smaller room and being closer to the walls make that easier or more difficult? The room is about 10'x11', so I shouldn't have too much trouble getting some bass, right? I left my big subwoofer in the garage, there's no way it's fitting in here.

I'm wondering if I can get this to sound better than it did in the old place. If I can take care of the reflections, that should clean up the sound somewhat. Also, I wonder how 'making speakers disappear' is affected by moving to a smaller space. Does being closer to the speakers help or does it make it worse? I wonder if I could turn this into an almost-nearfield setup where the room's signature would be felt much less than before. But nearfield dipoles... will that work?

That was quite a ramble

Thanks,
Saurav

**PMazz** · 23 April 2005, 13:45 Saturday

Originally posted by Brian Bunge

Jon,

That's what I figured you were talking about. Like I said, these are going to take me awhile so just get to it when you can. I really want to get the cabinets done and have the drivers measured in the cabinets before I finalize any XO stuff anyway so that gives you and Chris plenty of time to play around with them.

One thing I thought about doing to cut down on veneer costs is to simply veneer the sides and top and have the baffle and back painted gloss black like Pete did on those Avalanche subs. I think they might look pretty classy that way. I will have to find a local shop (or maybe a vocational school that'll do it for just the cost of the paint) that can do that kind of work. Or maybe Pete could do it for me?!

I wonder what shipping costs would be for that...

Maybe if you make the front and back like they do with the baffles on the PE cabinets? Maybe a rabetted baffle that could just be glued in?

I just did 2 sets of Corian baffles for a friend and shipped them. Black is a piece of cake compared to them

.

Either that or do a road trip up here. I'm always looking for another excuse to barbeque and drink beer :B

Pete

**Brian Bunge** · 23 April 2005, 21:13 Saturday

Pete,

Actually, the baffles and backs will be made of a 1" MDF outer layer and a 3/4" MDF inner layer. The inner layer will be inset into the sides, top and bottom and the outer layer will be outset. I will most likely have a 1/8" relief sort of like all the North Creek Music cabinet plans show. I was planning on doing this so that I could veneer the rest of the cabinet before adding the baffles and backs. So basically it'd be the same concept as the PE baffles, just with no screw holes in the baffles.

**PMazz** · 24 April 2005, 05:31 Sunday

Originally posted by Brian Bunge

Pete,

Actually, the baffles and backs will be made of a 1" MDF outer layer and a 3/4" MDF inner layer. The inner layer will be inset into the sides, top and bottom and the outer layer will be outset. I will most likely have a 1/8" relief sort of like all the North Creek Music cabinet plans show. I was planning on doing this so that I could veneer the rest of the cabinet before adding the baffles and backs. So basically it'd be the same concept as the PE baffles, just with no screw holes in the baffles.

Sounds like a plan. I always wanted to do something similar but never seemed to work it in to a design. If you could ship them before adding the 3/4" behind them, it would help with weight obviously. Either that or ship in 2 seperate packages. I still have some black left from the subs.

Pete

**Brian Bunge** · 24 April 2005, 10:32 Sunday

Pete,

I just ordered the RS tweeters and it'll probably be a few weeks before I can get the cabinets built. I'm trying to decide if I want the baffles and backs to have rounded corners or 45 degree chamfers on the vertical and top edges. I imagine that's something that'll be determined near the last minute. Although, I've never had a cabinet with chamfered edges so I might go that route. Oh, and I'll have base plates that I'll want to paint the same way as well if that's not a problem.

**Eric S** · 27 April 2005, 08:25 Wednesday

Saurav,
I was originally planning on covering 100% of the wall space with sound treatment, as Jerry did in the link in my first post. But after reading through some of the materials on ThomasW's web page about DIY sound absorbing panels, I may just make a few panels and try that first.

In Jerry's theater, the darker panels on the bottom are made from fabric covered fiberglass for bass absorbtion, while the lighter colored panels on the top are fabric covered polyester for higher-frequency sound diffusion.

Perhaps I'll just try a few of the fiberglass/polyester panels placed at various points in the room. I won't have any feedback for quite some time as the room is not even completed yet and progress is slow right now...

**Saurav** · 27 April 2005, 09:59 Wednesday

Thanks. I'll probably start with something like that too. If you get to it before I do, please post pictures. One of the links with pictures says that it's a 10'x12' room, which is almost exactly my size, so I'll probably start with copying his stuff, at least for shapes/sizes. I don't think I can fit even a single 4'x8' panel in this room

Speaker Choice and Room Acoustics

Speaker Choice and Room Acoustics

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