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

[6thplanet]

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

Actually that big spike looks a lot like an H frame resonance. Did you simulate this? You can't run an H frame up very high unless you want to notch the H frame resonance - or just live with it.

EDIT - actually, the smaller bump at 300 hz is probably the H frame resonance, it's hard to tell how deep they are.

That sqiggle went away in my larger room downstairs. The dip around 300 is where the gap from the xover points sum (200 & 500) utilizing the h frame hump gain.

[Deward Hastings]

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

Isn't the Neo8 the driver Dennis Murphy used OB for his Philharmonic series? I've read only good reviews of them....

It's also what the OP has . . .

Seems to be a lot of effort here to tell the OP that he can't, or he shouldn't, or he should do it "their way" (so they can use the result as an example of how dipoles don't really work any better than ported boxes . . . sound worse, actually). It certainly is possible to "design" a not-very-good dipole speaker (and there are *lots* of ideas out there for how to do it). It is also demonstrably possible to design very good sounding dipole loudspeakers that compromise nothing significant while gaining the advantage of the dipole radiation pattern (and the "out-of-box" experience). I've suggested a way that demonstrably works, working within the boundries of what the OP has, and wants.

I'd love to hear *working examples* of some of the other ideas (I've tried some of them myself, and wasn't impressed) . . . and I've owned Maggies (MGII and MG3a), so I'm not completely averse to great big things in the living room (I'd rather not, though). One of the challenges of dipoles is producing something small enough to live with while still sounding good. It can, and has, been done . . .

[diy speaker guy]

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

Seems to be a lot of effort here to tell the OP that he can't, or he shouldn't, or he should do it "their way" (so they can use the result as an example of how dipoles don't really work any better than ported boxes . . . sound worse, actually).

Not true at all. I've shown pretty clearly how to use MJK's passive method. This method balances fs, qts and baffle size to make things easy to work with. And I'm not suggesting the OP should do things "my way" just suggesting that "Pete's way" is extremely costly, with no benefit over "my" method. And there's no reason this method can't produce outstanding results, MJK style passive OB's win awards at shows dominated by sealed and ported boxes.

If the OP wants to go active with dsp that's an option but it's expensive. The upside is that the only limit is driver displacement, otherwise you can use whatever driver you like on whatever baffle size you like.

One of the challenges of dipoles is producing something small enough to live with while still sounding good. It can, and has, been done . . .

... and I just showed how to do it. Passively. It can be done actively too but that's a whole other ballgame, much more expensive.

[diy speaker guy]

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

That sqiggle went away in my larger room downstairs. The dip around 300 is where the gap from the xover points sum (200 & 500) utilizing the h frame hump gain.

Gottcha. So the upper limit is 300 hz, and even then the H frame bump is causing problems (needing to be attenuated).

[Deward Hastings]

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

Why pay big money for a big magnet and then pay more big money to basically defeat that big magnet with big crossover components? It makes no sense unless you are going active crossover with dsp.

Well yes, I agree with that . . . but unless you’re designing to pricepoint rather than to optimizing performance there’s no reason *not* to go active.

I have no experience with those particular drivers but there's absolutely no reason they shouldn't work just fine.

Well . . . I see a couple reasons, but that’s beyond the scope of this discussion.

With a low crossover point, a truncated array isn't going to be much of a problem, in fact at only 30 inches tall

Not *much* of a problem . . . oh? . . . a 30 inch “source” at 800 Hz. is not *much* of a problem?

it won't act as much of an array at all at the frequencies it will be playing

Well that’s true anyway.

How is that different than any other driver? If you push a driver hard distortion will increase, there's no driver immune to that.

Well . . . the RS225 (and a pair at that) are larger, with greater excursion, and with appropriate electric crossover are protected against driving to their excursion limit (even at substantial SPL). Seems a bit different to me . . .

I'm not suggesting this is perfect

And again, I agree with that . . . nothing is . . . but also does it even begin to serve the goal of the OP? In my experience individual small amps appropriately matched to the driver coupled with active (line level) crossover is conceptually and practically simple, inherently flexible (with digital crossovers) and easy to work with. Response adjustments/corrections can be dialed in at will. For initial (or one-off) designs it’s unbeatable. If, once the design is locked, you’re willing to make the compromises entailed, you can try to implement it “passively” for a price-point design.

Afterthought (and just my “opinion”, in case anyone wants to take me to task for presenting my “opinion” as “fact”) . . . I think that in general using mechanical resonance (box or driver) to augment frequency response is a bad idea. Necessary, perhaps, for “pricepoint” designs, but still a bad idea. Wherever possible the mechanical system should be optimally damped.

[diy speaker guy]

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

Well . . . the RS225 (and a pair at that) are larger, with greater excursion, and with appropriate electric crossover are protected against driving to their excursion limit (even at substantial SPL). Seems a bit different to me . . .

Yes, true, but we don't know how loud it needs to be so this may be a moot point. Besides, you can get about 32 of the 6 inch GRS drivers for the price of 4 RS225, guess which option has more displacement.

... does it even begin to serve the goal of the OP?

I don't know, we don't have enough info. All we know is that he expressed interest in using a few clearly defined products, but he also stated he doesn't know much about OB design. There's 2 main schools of though here (active and passive) and variations on each, no need to get locked into something without understanding the available options.

The main argument against passive OB has been that it requires a large baffle. I've shown this is not the case. (Pete did too, but his approach is expensive.)

Afterthought (and just my “opinion”, in case anyone wants to take me to task for presenting my “opinion” as “fact”) . . . I think that in general using mechanical resonance (box or driver) to augment frequency response is a bad idea. Necessary, perhaps, for “pricepoint” designs, but still a bad idea. Wherever possible the mechanical system should be optimally damped.

That's a valid opinion, but MJK and others would seem to disagree. After all, without resonance there is no sound... period. All drivers have resonance whether you use it to your advantage or not. I don't see any disadvantage to high q drivers in this type of design, they have exactly the quality (q) of resonance that is needed and extra motor strength is not necessary.

I agree that a fully active, dsp'ed system with the best drivers you can afford can't be beat but that game has a hefty pricetag. On the other hand, you can get your feet wet for about $40 (including bass drivers and their low pass crossover) as I've shown. That may or may not be an interesting avenue for the OP (or anyone else).

[Deward Hastings]

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

Yes, true, but we don't know how loud it needs to be so this may be a moot point.

. . .

I don't know, we don't have enough info.

I have "unfair" (although perhaps not entirely pertinent) advantage here in that I've followed and discussed this and similar design questions with the OP in several threads on this board and others over the last several years, and I'm commenting in that context.

[Pete Schumacher]

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

Not true at all. I've shown pretty clearly how to use MJK's passive method. This method balances fs, qts and baffle size to make things easy to work with. And I'm not suggesting the OP should do things "my way" just suggesting that "Pete's way" is extremely costly, with no benefit over "my" method. And there's no reason this method can't produce outstanding results, MJK style passive OB's win awards at shows dominated by sealed and ported boxes.

Seriously? You call $35 for a pair of LP crossovers "extremely costly?"

Yes, $35 for a pair of 18ga iron core and a pair of 125uF NPE. That's it.

[Deward Hastings]

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

All drivers have resonance whether you use it to your advantage or not.

I don't believe that one can "use it to your advantage" without other, significant, compromise (although some others do indeed find those compromises acceptable). I'd rather keep all driver resonances out of the passband . . . whatever such resonance adds was not, after all, in the original signal . . .

[Pete Schumacher]

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

I don't believe that one can "use it to your advantage" without other, significant, compromise (although some others do indeed find those compromises acceptable). I'd rather keep all driver resonances out of the passband . . . whatever such resonance adds was not, after all, in the original signal . . .

I think he's talking about the resonance around Fs Deward.

[diy speaker guy]

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

Seriously? You call $35 for a pair of LP crossovers "extremely costly?"

Yes, $35 for a pair of 18ga iron core and a pair of 125uF NPE. That's it.

When I said "extremely costly" I was commenting on the price of the drivers and the crossover, and referencing that to the cost of the design I showed.

But yes, that's a costly crossover, considering that with the design I've shown you can use 20 gauge inductors (or even less - it only has to take 20 watts) and the inductance values are much smaller as well. You could build my whole proposed idea (including the bass drivers and their lowpass filter) for ~ the same price as just the lowpass crossover on yours.

Small inductors like this are extremely inexpensive from q components (loudspeakers.ca) here in Canada. I'm not sure where else you can even get them, PE doesn't sell anything under 18 gauge.

So to recap, my entire design (the bass section) costs about $40 while yours is about $280. Yours will be louder, the drivers have more displacement, but otherwise they are comparable. (And remember, you can double up the drivers in mine for an extra $28 to make them more comparable.) And your design needs a much larger amp. So yeah, "extremely costly" sums it up well I think, at least when compared to mine.

EDIT - But to be fair, that was the whole point of my simulation, to show that it's possible (and easy) to do this very inexpensively.

[Deward Hastings]

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

I think he's talking about the resonance around Fs Deward.

Yes . . . and that's included in "all". It's my opinion that (except perhaps for subwoofers, which are outside the "music" passband anyway so "quality" doesn't matter) Fs (and the resulting roll-off) should be either outside the working passband or critically damped.

[JasonP]

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

Ok I just sat down and scanned this thread and here is what I can contribute.

In regards to these questions:

How wide should I build the baffle?
What can I expect out of it?

I can that for any given baffle 2x RS225 will be xmax limited to -3db from what my 2x DA270 are capable of once you get down under the Fequal point of a baffle. What does this mean exactly? Well if you play it loud and want linear, 2x RS225 can output 70Hz at 100db in an 18" baffle. That turns to 90 at 50 and 80 at 40 hz. Clearly operating them all the way down isn't going to work at any serious output level on such a baffle, YMMV.

Now all this talk about the Q of the speaker at resonance has made me go back and think hard about my own budding OB design. So I thought: man, what if I can get real low end extension with a higher Q driver at FS! Nope, as I see it, that is delusion. Here is what I mean, lets look at the output of a driver with various Qs at its resonance point:



I circled the output of the driver at Fs with given Qs: yellow is a .5, red is .6, green is .7, and magenta a 1.1 As we can see, Moving from say a Q of is +3 db at Fs and if we can move from .5 to 1.1 we would gain +6. Now lets just ignore that with a Q that high you may well hear the Q audibly. Even so, the dipole step of an 18" baffle at the FS of these drivers (just under 30 Hz) is -16db. That means that its -16db for a 1.1 Q, -19 for a .7, and -22 for a .5 Now I'm saying that every decibel doesn't matter, but clearly at this point the baffle step is dominating the driver's Q in determining actual output. I don't think you can justify the few db gains in what you'd lose from a high Q like 1.1, but we all have different agendas.

Regardless, that is my 2 cents on driver Q in the open baffle application.

[Deward Hastings]

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

So I thought: man, what if I can get real low end extension with a higher Q driver at FS! Nope, as I see it, that is delusion.

Correct. It gives the apparently "flatter" response curve, but maximum SPL is still excursion limited, which means in practice that you've "gained" bass extension (but not bass SPL) at the expense of lowering overall sensitivity and lowering available SPL overall (which is just what Pete did). Plus, of course, the "hear the Q" sound you mention . . .

[MSaturn]

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

what? that's like saying every high-Q driver has limited excursion or power handling. not true. EQ out that bump and you 'gain' low end extension.

key is, high Q and go active! woo