ME Geithain (Active loudspeaker) have been selling active studio monitors with a cardioid bass response for a number of years now. The woofers they use range from 200-400mm (8" to 16)".
Good distortion figures too: The two big ones stay under 0.3% at 100 and 96dB respectively as far as I can tell.
Good distortion figures too: The two big ones stay under 0.3% at 100 and 96dB respectively as far as I can tell.
That is not the point. Yes, you can make a cardioid, but a cardioid is not narrow enough and you can't get any narrower than cardioid with that technique. My designs are 6 dB down at +-45 degrees. That is not possible at 500 Hz with any technique that I know of short of a gigantic woofer. At 500 Hz, your two plots are nearly the same. That's my point.
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As far as I know SEAS will do custom designs to rather small quantity orders. If the same is true for some other manufactures then it wouldn't be that impractical.
Thanks for pointing out the obvious. Of course they are hypothetical the drivers don't exist. But if one wanted them to, I figure that they could.
The latest lot of coax drivers are significantly better than previous offerings but using any of them for your speakers was not the point. Of course you'd never go that route. The point was that if it can be made to work in 6-8" drivers, then presumably it could be made to work in 12-15" ones and I don't see why it would need to use standard dome tweeters either.
I am not discarding the principle, but it doesn't solve the problem.
What we need is a good way to get high directivity in a smallish package in the 400 - 800 Hz region. Your cardioid doesn't do that - nothing that I know of does. Below 400 Hz I don't actually care what the directivity is as this is too close to the modal region where the room dominates regardless of the directivity and we just aren't very sensitive to LF reflections.
You seem to be enamored with the principle but to me its a solution in search of a problem.
As long as there is no new tooling involved. If new tooling is required guess who has to pay for that.
Actually that is exactly the point as I was asked if I had looked at coax. I have, doesn't work very well, so I moved on.
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My point was directed towards - have you tried a good one, as in principle of the concept. IE SEAS new coax giving you what you want, but only down to around 2.5kHz. Going bigger of course giving you that down much lower.
Okay, so you have to pay for expensive tooling on drivers that are bigger than around 10". Wouldn't hurt to try seeing what you could accomplish with a 10" version.
The point is that if audio nirvana would occur if you could get excellent 12 and 15" coax units, such as the SEAS 6.5" version, but bigger, that it would be worth doing. This isn't going to be a completely cost free endeavour. There are lots of hifi manufactures that set up tooling for their own ideals on perfect sound reproduction.
Okay, so you have to pay for expensive tooling on drivers that are bigger than around 10". Wouldn't hurt to try seeing what you could accomplish with a 10" version.
The point is that if audio nirvana would occur if you could get excellent 12 and 15" coax units, such as the SEAS 6.5" version, but bigger, that it would be worth doing. This isn't going to be a completely cost free endeavour. There are lots of hifi manufactures that set up tooling for their own ideals on perfect sound reproduction.
Based on my experience, I have zero confidence that would work well enough.
Depends on the definition of the problem.
The cardioid principle can be helpful if you want to achieve constant directivity on a small footprint. If you combine a waveguide and a conventional box speaker in a 2-way, you always get a step in directivity. That will happen if directivities are not well matched at the crossover point, but it will usually also happen because of baffle-step. A well tuned cardioid box smoothly transitions from directivity at low frequencies caused by interference between the back-wave and front-ave, to directivity as a result of diffraction at higher frequencies.
In my opinion a uni-directional speaker like this has several advantages over more conventional alternatives:
- Relatively high directivity, and thus a relatively strong direct sound (which I think is beneficial in most rooms)
- Small size
- Can be placed close to the rear wall, without detrimental effects on the sound
In the modal range, I don't really care about directivity much, although dipoles and cardioids may have some advantages over monopoles. However, if constant directivity and a smooth power response are required in the transition region, remains open for debate. Reflections with frequencies between approximately 100 hz and 1000 hertz are known to contribute to envelopment. Single reflections may also cause comb filtering, which can cause coloration, especially in the lower hundreds. Therefore I am of the opinion that maintaining unidirectionality down into the transition region is beneficial.
If you are able to place you speakers well away from boundaries, most of this probably doesn't matter much, though. But then again, who is in the position to build a room around their sound system? Not me, unfortunately.
Why do you want higher directivity specifically in that region?
I googled for some measurements of the Summa and found this:
Is that sudden step in directivity between 200 hz en 800 hz a measurement artefact? The measurements I've done on similarly sized speakers always showed some directivity even below 100 hz, but also directivity increased more gradually.
I don't think the results below 700 hz are meager. The radiation towards the rear-wall is diminished quite a bit in comparison to an ordinary box. Just have a look at the plots I posted on the previous page.
You do lose some efficiency. A resistance box resembles a true cardioid. A true cardioid has 6 dB's more output than a dipole with the same distance between front and back of the driver (Linkwitz calls it the dipole distance, D).
Like a dipole a cardioid falls off with 6 dB's per octave toward the lower frequencies. Therefore, you do need a subwoofer. But then again, if you want good bass there is no way around either large speakers or subwoofers (and I'd take the latter every time). Here's are the on-axis responses of the same two configurations, the closed box and the cardioid. Not too bad, is it? In practice you get quite decent output down to about 100 hz.
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And by that you mean it simply isn't big enough, or that there are other problems?
You do have other loudspeakers in the line up besides the larger models, both an 8 and 10". Surely a properly designed coaxial 10" would beat your current 10". I am assuming here that the cone and then cabinet transition with the coax would provide you with a similar amount of directivity control that the wave-guide on it's own would offer.
Or are you saying that your smaller designs don't 'work well enough' either and that they are simply there to appeal to folk who want some directivity control, but can't have a larger speaker?
I am not saying that the wave-guide/cone of the coax would be as good as your custom wave-guide in every way, just that it would be pretty close and that having the coincident design would offer other benefits that would outweigh what the coax can't do vs your wave-guide.
I don't sell an 8 and 10" any longer, haven't for awhile. But when I tested the 10" coax it was not even close to the Nathan 10" - I mean not even close.
You keep saying "properly designed coaxial" like I don't know what I am doing
I thought I defined it pretty well.
I want high directivity above 700 Hz to avoid early room reflections which degrade imaging. I get spaciousness from the later reflections.
That's an ancient plot. Look at the NS-15 at the site below (NS-15). The transition in directivity is very smooth going from 0 dB to about 6 dB (I think that the scale is wrong and this should really be 12 dB) at 1 kHz and nearly rock flat above that. Please show me another speaker that has directivity control this good.
I could get the DI to go to 6 dB (3 dB on that plot) at the low frequencies with a cardioid, but then I would loose about 6 dB in efficiency. That would not be a good trade off IMO. I know you have your beliefs and I have mine and they are different, but the data that you sent me for your speakers was not as good as the NS-15, cardioid or no cardioid.
So expand upon why you find a coax not properly designed. I am under the impression that if one sets out to actually put the design emphasis more heavily on the performance of tweeter and the wave-guide effects created by the cone, that you would no longer find it 'unacceptable'.
By properly designed, I am meaning that the cone geometry, the surround, the throat where the high frequency device meets the cone and the way in which the basket interacts with the cabinet, would give you a wave-guide effect similar to one of your properly designed wave-guides.
Then you'd have a well designed cone, such as that of the AE TD series to cross it too.
Yes, this would require you to design the surround, cone and throat geometry whilst working with a driver manufacturer to meet your criteria and yes it would probably be pretty expensive, But I cannot see why this approach wouldn't work. If it did then you'd have all the benefits of CD plus the benefits of a coincident driver.
TAD, Pioneer and KEF have all gone this route more recently with their top line products. Such as the TAD Compact Reference CR1 and the KEF blade. No they don't control their directivity down low enough compared to what you'd find acceptable, but I don't see why they couldn't if they actually wanted to make them far far bigger.
By the way Earl, if you google 'Geddes loudspeaker'
Loudspeakers
Is the website you get taken to.
If this isn't up to date, perhaps shut it down.
Loudspeakers
Is the website you get taken to.
If this isn't up to date, perhaps shut it down.
I think our goals aren't all that different, although I believe I am more forgiving of early horizontal reflections, as long as they are not too early and strong. Also I am more concerned with size and ease of placement, while you care more about having a huge dynamic range.
I agree your waveguides perform very well. Unfortunately your application won't run on my current computer. The only one on which it ever ran was an old Windows XP desktop, which I no longer have.
A 15" pro midwoofer like the B&C you're using has dynamic headroom in spades. Your speakers could lose 15 dB's of efficiency in the low midrange and they would still have more headroom than most high end hifi speakers. In my opinion this is a non-issue.
You are referring to the measurement of this speaker. That was the first of its kind I built. The latest versions perform much better. See the plots of an 8" version on the previous page. Your waveguide obviously performs much better than the Selenium-Dayton combo I used, which has a rough response and beams quite a bit.
I am not all that familiar with those products. I do not doubt that one could, given a lot of resources, build a good coax. I am not convinced that the tradeoffs, and there are always trade offs, are good ones. I have found a solution that works well, and I have tried many other solutions, including coax. The one that I use works best for what I am looking for.
I am in the process of shutting it down and my link below no longer points there. But it takes a while for Google to catch up. And it takes awhile to transition a website. One does not just setup one and drop the other all in one day - or at least I was not comfortable with that approach. The old site is broken, but it is still where Gedlee.com points to and until I transfer the Domain Server it has to stay like that (very old Name registrar.) My E-mail still goes through the old site and I need to sort out changing that without a glitch.
But this is precisely the problem. In a small room the horizontal reflections are always "too early and strong" unless you have a narrow enough directivity to avoid the near walls. Cardioid is not narrow enough to do this.
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