Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

[fjhuerta]

So, here's the deal....

Some time ago (5 years), I built a speaker using the Seas CA21 (later the P21), a Neo8, and a Neo3 - in a box.

http://www.htguide.com/forum/showthread.php4?t=26798

I love the way it sounds, and up until lately, it was the speaker I liked the most. But I just fixed my ZDT project, using what I've been able to learn from all of you ( ) regarding an uniform power response, and I definitely like them quite a bit more than the Neo based speaker now.

So, it's time to unscrew the old Neos and build something new!

The Neo3 doesn't have a back cup anymore (I built a bigger chamber for it), and the Neo8 is a dipolar driver OOTB. So they are both ready to rock.

I read on the other thread that a pair of RS225s on an H frame may be enough for the low end. Frankly, I'm not going for an SPL record here, but I desperately want to try a dipole / OB.

So I guess this is the ticket. 2xRS225s, Neo8, Neo3. Hybrid design - using the MiniDSP for EQ and the x-over between the RS's and the Neo8 / Neo3, an d a passive network between those two.

It could work. I used the Neo8 down to 800 Hz, L-R 4th order. I'm not sure I'd take it any lower free air. The RS225's can get to 800 Hz, 4th order. The MiniDSP can filter out all the resonances. I already found out 2.8 KHz between the Neos works pretty well.

Unfortunately, I don't have a clue about how to do an OB. It should be simpler than a box, but simulations all tell me it really isn't. My biggest concern is the bass - what's an H frame? I have a clue, but that's not enough. How can I design it?

How wide should I build the baffle?

What can I expect out of it?

Any help will be greatly appreciated... for sure!

[natehansen66]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

I have 4-way dipoles, using a Neo3 and I've got a pair of Neo8's on their way :D

In a nutshell, a wider baffle will be easier to design a passive xo for the Neo's, but the tradeoff there is irregular off axis dispersion.

Narrow baffle gives you a better off axis dipole response (30 deg -1db, 45 -3db, 60 -6db as defined by Linkwitz), but in most cases requires eq, don't know if a passive approach would work. Depends on baffle size.

Have you ever used the Edge? Simulates driver response for a given baffle size, good to model before you dive in and start cutting: http://www.tolvan.com/edge/
I'm not sure how you'd model those planar drivers but I know its been done, maybe use the size between the outer slots as the driver and define your baffle size.

I don't use any baffle at all! I hang the upper 3-way drivers from wires, and use a shallow u-frame with a pro 15" below 300hz. This requires a lot of eq, but gives a very nice polar response. I've used baffles and I've come to prefer none at all....to each his own.

As far as the 8's go for bass I wouldn't be happy with it. Even with h-frames or similar those are small drivers to try to get decent spl from down low (without box loading), unless you were bringing a sub in around 80hz or so........The roll-off would require eq and I don't know how well 8" woofers would handle it. I doubt it would be as effortless and clean sounding as larger drivers. I'm pretty happy with my 15's, they're eq'd flat down to about 40. Any lower and distortion rears its head. If i had the room I'd add a second set of 15's in h-frames.........

OTOH at low volume the 8"s might be ok.

[Deward Hastings]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

Piece of cake . . . there are no critical dimensions. A pair of RS225 on a baffle 12-14 inches wide should get you down to 80 Hz. easy enough . . . neither of the neos need baffles at all (or just enough to hold them in place), and they'll work better that way (look at John K's "Note" for an example). The passive crossover should work between the neos, and LR4 is fine for the cross to the RS225s. You *will* need to cross them to a subwoofer (use LR4 for that, too) for decent bottom end, but any small box[es] will do, at least for a start, and what works best below 80-100 Hz depends a lot on your room (I like dipole down to 40-50 Hz., but people argue about that).

You *will* need some boost followed by the 4th order cutoff on the bottom, the boost to correct for dipole cancellation, the cutoff to prevent overexcursion and blend with the sub. And you will find yourself doing various voicing "corrections", including some HF roll-off, to get everything sounding right . . . but the miniDSP will make that easy.

It's about time you actually tried it ;) :D

[Pete Basel]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

Have you seen this?:

http://www.linkwitzlab.com/models.htm#A1

[Pete Schumacher]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

Piece of cake . . . there are no critical dimensions. A pair of RS225 on a baffle 12-14 inches wide should get you down to 80 Hz. easy enough . . . neither of the neos need baffles at all (or just enough to hold them in place), and they'll work better that way (look at John K's "Note" for an example). The passive crossover should work between the neos, and LR4 is fine for the cross to the RS225s. You *will* need to cross them to a subwoofer (use LR4 for that, too) for decent bottom end, but any small box[es] will do, at least for a start, and what works best below 80-100 Hz depends a lot on your room (I like dipole down to 40-50 Hz., but people argue about that).

You *will* need some boost followed by the 4th order cutoff on the bottom, the boost to correct for dipole cancellation, the cutoff to prevent overexcursion and blend with the sub. And you will find yourself doing various voicing "corrections", including some HF roll-off, to get everything sounding right . . . but the miniDSP will make that easy.

It's about time you actually tried it ;) :D

Boost? Boost is not necessary, if you instead "cut" the mids and highs to meet the low-passed RS225s. Nothing wrong with taking a passive approach a-la Martin King.

[hipcheck]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

I just want to ask, what size room do you have? and how far from the wall will the rear of your dipole sit, and how far to the wall behind you? I would look at this if I was you. You *might* find problems with the Neo8. I would look into foam and stuffing behind the rear of the Neo8 in a small chamber. I would do a damped Uframe type build for the RS225. I did this once with 2x DCX crossovers. I never nailed it down, and sold all the drivers. I never made it past raw mdf. It was fun though.

I think the problem was the rooms I wanted to use did not work well for Dipole speakers. Dipoles are not for every room. And frankly dipoles are just another flavor of speaker. I enjoy a variety.

If this was your first build what you plan would be amazing and you would have a hard time beating it. Active, multi amped, dipole, etc. However, if your a hard core tweaker this system would drive you crazy. I found mine the drive you crazy speaker system. I spent too much time trying everything I could on this system.

Steve

[LouC]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

I experimented with this very combination of drivers with a passive crossover. Never personally liked the NEO8 running open baffle (at least as a single). The rear chamber sounded better to me. Doesn't mean it can't be done, but I didn't think it was worth it.

I know somebody did an MTM style Neo8/Neo3/Neo8 and was pretty happy with it. I'm not sure if there's enough in 800-1500hz range to make it work effectively with just one.

My experiments are detailed here: http://www.lonesaguaro.com/speakers/Neo83/Neo8Neo3.html

Maybe it'll save you some time/effort.

[Deward Hastings]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

Boost? Boost is not necessary,

Incorrect. Boost will be necessary with RS225 on a "narrow" baffle to compensate for dipole cancellation. Putting them on a wide baffle to avoid that is a poor design choice that leads to other, worse, problems. The cross to the planars has nothing to do with it.

[Pete Schumacher]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

Incorrect. Boost will be necessary with RS225 on a "narrow" baffle to compensate for dipole cancellation. Putting them on a wide baffle to avoid that is a poor design choice that leads to other, worse, problems. The cross to the planars has nothing to do with it.

With all due respect Deward, hogwash.

Passive LP can accommodate all the EQ needed to flatten the response to meet the mid and tweeter, even on a narrow baffle.

[Face]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

There's more than one way to skin a cat...although the passive approach may require some large parts.

[diy speaker guy]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

My biggest concern is the bass - what's an H frame? I have a clue, but that's not enough. How can I design it?

An H frame is not a flat baffle, it's got open ended chambers on both end. The open ended chambers have a depth of a few inches and that depth causes a severe peak in response. That peak is going to happen fairly low in frequency so an H frame might not be the best bet for a 3 way with a fairly high crossover point. Both John K and MJK have free software to model H frames.

How wide should I build the baffle?

What can I expect out of it?

Assuming you want a flat baffle, it's pretty easy to model. MJK's flat baffle simulator is not free but John K's is. And I can model it for you if you want.

The design depends on your goals. Remember this thread from yesterday? http://techtalk.parts-express.com/sh...d.php?t=230936 He only showed response down to 100 hz, since he's not using it any lower than that. He used 2 Dayton DA270 on a 18 x 43 inch baffle. A simulation looks like this.



It doesn't hit xmax until below 40 hz (so it will go considerably louder than shown assuming it's protected below 100 hz). He hit his goals, he wanted it loud but didn't need anything below 100 hz. But that's a HUGE baffle for a speaker that still needs a sub.

Unless your 8 inch drivers have a vastly higher q than than the DA270, your response on a similar sized baffle will look something like the sim above.

On the other hand, if you choose your bass drivers wisely (high q) you can use a much smaller baffle (8 inch wide) to hit the same 100 hz or you can use the same 18 inch wide baffle to get fullrange performance down to 30 hz, all with a simple passive crossover. But in both cases you trade some spl (either for a slimmer baffle or lower response).

The good news is that drivers suitable for passively crossed small baffle OB bass are generally much less expensive than the drivers you want to use.

[cjd]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

I've been playing with the BG parts and have switched to the Neo10 in place of the Neo8. It just works better all around, by far.

As for the RS225... not even on my radar Too small, not enough sensitivity. I'll run dipole to ~40Hz if I ever get this done, but I don't have a space in which to use the results so am in no rush.

C

[Deward Hastings]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

Passive LP can accommodate all the EQ needed to flatten the response to meet the mid and tweeter,

Again . . . it has nothing to do with the mid and tweeter.

[Pete Schumacher]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

Again . . . it has nothing to do with the mid and tweeter.

I know that Deward, but the response can be shaped with passive components, depending on where you want the low frequency cutoff to occur.

You can boost with an amp, or you can cut with a crossover . . .

Just ran a sim . . . 7mH and 125uF with the RS225-8 (x2) on a 10" wide baffle will produce F3 at 70Hz and 700Hz, very smoothly.

Granted, the sensitivity is low (~75dB, hooda thunkit) but the components are not ridiculous and the response is very nice.

[diy speaker guy]

Re: Instead of hijacking the OB thread... how does a 2xRS225, Neo8, Neo3 OB sound?

... the response can be shaped with passive components...

You proved your point but it's expensive trying to force a low q driver to do something it doesn't want to do.

You can get better sensitivity (less amp needed) with cheaper (high q) drivers, which in turn will lead to a less expensive crossover.