A good tweeter to match 5" SB Acoustics Magnesium Woofers

[xmax]

Some will never learn. When I get done with these Monitors I am doing for the Grammy award winning recording
engineer for "Rock Record of the Year" (Grammys) last year. I will take some more time with this silly test. I have mounds
of test equipment I have not dug out yet.

[xmax]

And to be clear I am aware he would have tweaked the filter for the addition of the resistor,
but perhaps not enough. I have all the parts to build this speaker and intend on doing it
although I was hoping I did not need to go to these extremes for you guys to get it.

[dcibel]

Why would you build such a crappy speaker?

[xmax]

Maybe It's not crappy and I'm a crazy person, this will be the only way to tell for sure.

Also perhaps I should be volume matching since that is what will be happening essentially.
Then with the mic a few inches from the tweeter and nothing else within 3ft you can say
it's a reflection problem...

[johnnyrichards]

Touching on this again, above is the reason I sometimes favour the "first to third" order crossover function (basically a very overdamped third) that I've posted about numerous times. Also why I favour a slight on axis system dip near tweeter roll off knee (recall being berated here on this forum at length for that one). Exact opposite of the speaker under discussion here.

FWIW, I'm not the only one with the opinion that bump at the low end of the tweeter usually (again I haven't heard this speaker) sounds overly aggressive in that range once room contribution is factored in . George Short from North Creek etc (as I've posted quite a few times) came to the same conclusion as I about overdamped 3rds and used those and "gfiandy" over at diyaudio is a commercial loudspeaker system designer (speakers for Arcam and others) and also advocates for the on axis dip, only achievable with a soft high pass knee:
http://www.diyaudio.com/forums/multi...ml#post5306291

I do the same thing, although I sometimes refer to it as a "BBC dip". Flat on-axis on so many of my design attempts sounded poor, when I finally disciplined myself to take off-axis measurements, I figured out why.

[hongrn]

xmax, you should really post the build on this forum, especially the crossover work. I don't know about the rest of you, but I need to learn from the best.

[dcibel]

I do the same thing, although I sometimes refer to it as a "BBC dip". Flat on-axis on so many of my design attempts sounded poor, when I finally disciplined myself to take off-axis measurements, I figured out why.

IMO that is essentially what the "BBC dip" was correcting, as well back in the day when it was being used you would often see higher distortion in this frequency range due to the midwoofer breakup, contributing as well to the "energy" present in these frequencies, so the effect was two-fold.

The tweeter dispersion "mushroom" became very clear to me on my first serious design - an 8" 2-way. Flat response on axis sounded a bit too shouty to me, added a couple dB drop just above the crossover frequency to compensate for the wide tweeter directivity here made a huge difference.

I am still surprised that you don't see more tweeters with waveguide faceplates available, even in very high end tweeters they still are built on a flat plate. Even a small waveguide like you see in Seas DXT, Morel CAT378, or Wavecor TW030WA11/12 can make a difference to that directivity pattern around the crossover frequency, with added benefit of avoiding the baffle diffraction and improving low end distortion. The testing available online at AudioXpress for the Wavecor mentioned are a perfect example of the diffraction benefit. I am also of the opinion that a waveguide tweeter making for a more "constant directivity" speaker has a much greater chance of creating the same sound tone in different rooms, since there is greater forward facing energy, less off-axis energy, so the room being "live" or "dead" has a lesser effect on the overall sound at the listener.

[dlr]

I don't disagree with most of what you've said, but there is a lot related to taste that enters into it and there is no one answer to all driver combinations. I'm probably much closer to your position on this, but I don't do first/third, though I have experimented some and found that BW1 can be a good option with the right drivers. My preference has mostly been for LR2 and depending on the tweeter used, introduce a slight droop from around 1-3KHz. Long ago we had a discussion back at Madisound I think related to this. Jeff was involved in that and I think that his analysis was probably correct and it's related to your thoughts here. It wasn't about any XO peaking at the tweeter low end or not, but with the use of LR2 primarily. That relates to power response which of course is primarily about polar He pointed out that LR2 provides a broader power response dip. I usually add a small dip in 1-3Khz area that I think recesses the vocalists just a bit for "soundstage" if you want to call it that. It's just more pleasant and natural sounding to me, I hate a forward presentation.

You've probably done more real research into the off-axis and room influence than most here, so I really can't go into that detail, but in general I think that my preferences probably align with yours just from my own experiments.

WRT to the low vs high Fc, I do take issue with one part of that. The driver combination really controls which way to go. My current main system is a 3-way dipole, with the tweeter (monopole) front hemisphere polar response similar to that of a full dipole. My goal was to get a front hemisphere horizontal response operating primarily in dipole mode with the tweeter integration matching and with a smooth off-axis integration, no tweeter bloom. That is a problem and I agree with you on that. I went about it in an entirely different manner and could not have done this easily in the past.

First I fully treated the baffle for tweeter diffraction. That's always first after creating a box/baffle (baffle only here, no box) as I'm sure you know. That was key, but the other factor was the Ultimate Equalizer (UE) from Bohdan (SoundEasy creator). I had started using SoundEasy earlier to audition designs before building a crossover. It was my primary use as I still measure with LAUD. This provided a unique ability to audition literally dozens of designs in a single evening. What I realized made this unique is that if you use accurate driver SPL measurements (no impedance required) and set any design target on-axis, then no matter what XO you target, the on-axis will always be that target. The DSP in it guarantees it. From this point on I knew that I could completely dispense with on-axis measurements! When I realized this and confirmed it for multiple cases, I started measuring horizontal polars.

My system includes a 5" midrange and 1" woofer. Exceptional midrange, the single most important driver IMO, and a good, but not exceptional tweeter, one that I expected to have better front directionality, the DXT. But I found that it's not nearly as directional as I expected, so any tweeter would probably be fairly close in polar response.

Here's my experience with M/T crossovers on this pair which I would expect to work on similar small midwoofer 2-ways. I fully expected to go with about 2.5KHz LR2. I thought that higher Fc with broad overlap would provide the best polar response integration. I quickly found that to be entirely the opposite. There were significant off-axis integration problems. I did not have to consider any tweeter transfer functions because the UE created whatever filter was required to achieve the on-axis target. I spent several hours measuring dozens of designs off-axis. I went out to 60 degrees initially, but decided that only 45 degrees was necessary because the changes were consistent with other angles. In the end I designed the system XO strictly at 45 degrees.

High Fc with broad overlap had the most off-axis irregularities. The final XO that I now use was LR8 @1200Hz. Everything higher Fc and/or lower order was progressively worse, which completely surprised me, but it was the measurements that proved it to me. I'm sure that the tweeter transfer function to achieve that must require peaking and the equivalent of a Linkwitz Transform to extend it flat, but that's what I use and I've never heard any stress in the system at my typical listening levels or even short term testing. The tweeter might fail due to heat stress if I ran it too long, but I don't stress my ears for any length of time anyway. But I couldn't find any other crossover that didn't have off-axis flare and it was higher with high Fc. I never did consider trying a higher Fc, then altering it for tweeter flare. I wanted the best on-axis direct response and good polars.

Measurements are without the woofer, due to the 250Hz Fc and my basement with a low ceiling, so limited time response. Besides, at 250Hz, integration isn't as difficult for W/M. I was interested primarily in the M/T. Ignore anything below 500Hz. The woofer would have filled that in.

These are direct first, then normalized to the on-axis in the other. Keep in mind that this is LR8 @1200Hz.




These next two are also limited to 500-5000Hz to cover the mid/tweeter integration.



dlr

p.s. I could not have designed it in this manor if there was any significant tweeter diffraction influencing axes differently. It was the controlled diffraction that gave good on-axis response that was maintained in the off-axis as well and provided consistent results no matter the crossover used.

[dlr]

Even a small waveguide like you see in Seas DXT, Morel CAT378, or Wavecor TW030WA11/12 can make a difference to that directivity pattern around the crossover frequency, with added benefit of avoiding the baffle diffraction and improving low end distortion.

That's what I hoped for with the DXT, but it didn't prove to be nearly as impervious to diffraction as one would think.

dlr

[xmax]

I should have noted my last 2 designs (and current) use a Volt 3" soft dome, it of course allows higher and "softer"
filter alignments for the tweeter, the off axis of the big dome is much different. So listening to a tweeter with this
type of filter verses the small 2 way is like apples to oranges. That said my most popular design (like at 3rd Man)
uses a 6" and compact SB tweeter so I'm not completely alien to the concept. I think it is a combination of polar,
response and other factors.

[ryanbouma]

I agree on the lack of waveguide dome tweeters. Ive been looking for years. There was a time on this forum when people were very skeptical. Not sure why. I could see many drawbacks. But thankfully people are coming around to the idea. I have been meaning to try the wavecor for a long time and it'll be on my next order. Sent from my SGH-I337M using Tapatalk

[xmax]

The way I deal with some of these issues. This helps avoid a BBC dip on axis.

[xmax]

Please explain this ratio and poi nt me in the direction where I can read about it. I am not sure how you do this since every tweeter os different and the cross over points are infinite with all the different roll offs. Maybe there is a generic rule ?

When I find one of the articles I like on the subject I will share it with you, Since I also design audio electronics I deal with filters with everything
from power supplies (I have sold about a million dollars worth) to EQ's to line level filters (I use them in my speaker systems too).
The names Butterworth, Bessel, Chebyshev etc are named for their things like transfer function, Q, and transient attributes among other reasons.

If I was new to this and looked at the PE TT forum I would think LR or Butterworth only refers to the dB down at Fc and phase characteristics.
I personally feel cap and coil ratios are more important.

[dcibel]

The way I deal with some of these issues. This helps avoid a BBC dip on axis.

Ah, this must be the "anti-waveguide". Absorption instead of reflection.

[dcibel]

When I find one of the articles I like on the subject I will share it with you, Since I also design audio electronics I deal with filters with everything
from power supplies (I have sold about a million dollars worth) to EQ's to line level filters (I use them in my speaker systems too).
The names Butterworth, Bessel, Chebyshev etc are named for their things like transfer function, Q, and transient attributes among other reasons.

If I was new to this and looked at the PE TT forum I would think LR or Butterworth only refers to the dB down at Fc and phase characteristics.
I personally feel cap and coil ratios are more important.

I see now, you looked at the PETT forum and thought "here's a bunch of idiots that don't know what they're doing" and thought you'd join the party!

Of course, the filter type defines the transfer function, phase characteristics are defined by the transfer function so you can't have one without the other. However for acoustic design, the strict electrical definition of butterworth, L-R, etc can be thrown out, since we are not designing an electrical filter but an acoustic filter, and the filter is applied to both a non-linear electrical device, and a non-linear acoustic output, and multiple acoustic sources (each driver radiating from different points in space), so the cap/coil ratios are whatever they need to be to achieve the intended frequency and phase correlation at the acoustic end, whether 2nd order, 4th order, etc, it is defined by a combination of the electrical and acoustic characteristics.