First Order Crossovers: Pros and Cons

A previous post asked whether preserving the waveform was more important than other aspects of speaker design (I am guessing that other aspects are flat frequency response, radiation pattern, and input impedance curve, dynamics and ability to handle high SPLs).

This led me to wonder whether the real catalyst for the increasing number of 1st order designs is that the newer generation of drivers is allowing speaker designers to offer 1st order designs, without having to make great sacrifices elsewhere. I remember reading an interview with Jon Bau of Spica fame where he said he would have liked a stronger bass response from the Angelus, and would have liked a design to handle higher SPL but that drivers to achieve that and also achieve his other design goals were not available at the time within his price constraints.

Looking at the drivers on the green mountain speakers, the Morel HF unit and the Aurasound LF unit I did a little research on the units and found that they appear to offer very high performance for relatively little money. The Morel tweeter is able to reproduce relatively low frequencies, and the aurasound woofer has a very lightweight, but quite rigid cone, allowing it to produce quite high frequencies before it breaks up. These low(ish) cost wideband, high sensitivity drivers are the enabler for a first order 2 way design. Perhaps they just didn't exist 10 years ago, and perhaps that is why 1st order designs have become more popular of late.

That's not to take away from the skills of designers like Roy, but it does seem that he has some great raw materials to work with now that Jon Bau and others may not previously have had access to.

I'm not convinced that amplifiers have made great strides in the last 20 years, but I am convinced that speaker technology has.

I haven't noticed a huge difference in sound on my GMA speakers between the sweet spot and the standing position. There is SOME difference, but I would not say it was a big difference.

Good thread and great technical contributions from Roy and Karl.

Good points also brought up by Seandtaylor99 i.e. parts quality has improved in terms of speaker technology, but how well that has been implimented in most designs may be another story. Just getting some of the basics right in older designs places them miles ahead of newer designs using higher quality parts in many cases. It is too bad that some of the "speaker industry giants" aren't around now to take advantage of the better quality drivers that are available to use now.

Sean's comments about "vintage" electronics is also true i.e. i've often said that older products with updated componentry can many times outperform newer products for a LOT less money. Sean
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I hear what you are saying about xovers, Roy.
But the fact remains that in there own pass bands tweeter and woofer are
working 90deg apart. If I now want to replay say a large cymbal with a fundamental at 440Hz and strong harmonics all the way beyond our hearing range (in our case past the xover point) it still means the fundamental will be 90deg out of phase with (some of) its harmonics.
I don't really care what vectors do as I don't hear vectors but I hear phasing.
We all do since, with the exception stereo recordings, all our spatial information derives from phase differences. You can test that next time you have a bad headcold that cloggs up one ear: Listen to your stereo and its like mono, go outside and you can easily tell where a noise comes from. This also works with a small ball of cotton wool, if you haven't got a cold handy.
But anyway, what I understand as phase coherent means that the entire output is in phase ideally independent of listening position.
The only speakers capable of this are full-range, single driver designs.
But Tannoy makes an acceptable(to me) compromise. Seperate drivers on a vertical line are just one step too far for me.

Still can't accept your time/phase 'explanations' it goes against everything I have ever learned and would directly contradict my two relevant college lecturers, my Professor at the Technical University Berlin ,
Guy R. Fountain ( Founder Tannoy)
Peter Walker ( Founder, Quad)
Peter Voigt ( Lowther )
and pretty much everybody else I know who's worked with AC current and/or acoustics. I don't think your lone voice is enough for me to budge on that one.Again lets look at sinewaves and lets only regard 3 points (max., null point and minimum)of it curve for the moment: to be time coherent 2 sine waves need only to start at the same moment, they could start at any of our 3 points: max and falling; min and rising; nullpoint either rising or falling.
Thus we have 4 ways in which our two sine waves can be in time.
To be in phase our 2 waves have not only start at the same moment but also the same point. There are now 3 ways in which our 2 waves are in time but not in phase.

You mention some distortion regarding my Tannoys, fair enough they distort. So do all speakers, but of course total distortion is very easily measured and mine measure up thus: for 90dB SPL, 50Hz-20kHz less than 1%;for 110dB less than 3%. How do yours do?

The thing with your test tones is quite amusing since you should be using pink noise or white noise to measure for phase coherence. Its not difficult to find a driver thats in phase with itself and one single tone from another but that does not make it phase coherent.

I'm sure you could hear the comb-filtering going on if you'd honestly compare to speakers which do not exhibit this particular problem.
I can and, compared to some people, my hearing isn't that good.
Its the comb filter effect thats (partially) responsible for the sweet spot ie the sweet spot is the area where the comb filtering is at its minimum. With speakers that emulate the point-source ideal (planars,Tannoy DC's and full-range drivers) this is much less pronounced although fr-drivers teend to produce their own version of the sweet spot due to beaming.

Some great points from Golix and i agree with some of the points that he's making here too. This is the reason that i love my modified Ohm F's, warts and all, and why i've said what i have about them. You've got one driver that is both phase and time coherent, covering the entire audible range with great bass weight and a phenomenally spacious radiation pattern. Other than that, and as i've mentioned before, any other attempt at loudspeaker design becomes extremely complex with multitudes of trade-off's involved. Juggling the trade-off's boils down to the personal preferences of the design engineer and the individual buying / listening to the speakers. As such, it is a no-win argument, just a discussion of various beliefs and preferences. There is only one way to achieve specific levels of performance, and at this time, even that approach has limitations. Sean
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