Is it possible to cover the whole spectrum, high SPL, low distortion with a 2-way?

I just finished my experiments with all-pass filtering using in ear monitors. This experience and my previous knowledge about filters and ringing are helping to grasp what @gedlee painstakingly told myself and maybe others about frequency response. Its one of those things that is very simple, so for no good reason it doesn't stick. It reminds me of my job at work, where things are pretty simple yet we complicate them for no good reason.

A smooth frequency response is the most important thing because whether an electro acoustical or mechanical acoustical filter, they operate generally the same. Smoothness might be described with Q once the relation to peak and low/high pass filters are seen. Relate the sensitivity response as another filter. Large and/or sharp changes in response create higher levels of group delay and ringing.

Source Signal, EQ, the Driver, Baffle, Waveguides, etc all apart of a system. Like the F of woofer changes once it joins an enclosure, a filter up stream, as in the response of the source becomes apart of the equalization down stream of the source, including mechanical acoustic impacts of driver, waveguide, baffle, etc. The resulting response is what matters, with a Premise of accurate reproduction of the source. The room is at the end of the chain, and I guess you could argue listening position and eventually your ears and the psychoanalysis, if wanting to go to the nth degree. Speaking nominally, the response had from the loudspeaker system plus room needs to be smooth and devoid of sharp changes.

Experimenting with the worst parts of my spectrum, I used an outside measurement, which are about 15ms at 167hz and about -10db from the fundamental level. I used an all pass centered on that frequency with a Q of 8.81 to achieve the same group delay, according to Vituixcad. I used a high pass to experiment with 167hz being -10db. I could hear the difference. The attack time wasn't what was making a difference that I could tell, it was the ringing. It was a similar event to reverb that had a fundamental resonance centered on the particular frequency. I am very interested to try this with the horn. With the high pass, it was just faintly discernable in vocals of J Cole, rapping. bypassed it the vocal as every so slightly dryer in the area of focus. Then the song has a transition to another part where there is a very punchy kick drum taking lead... this is more like an impulse response, and I can hear the Hf of kick drum ringing clearly how ever subtle the change is I can hear it distinctly.

If you look at the FR, it is not, smooth, nor a final voicing. I just set this up quickly to test headroom at that moment. A better voicing should create a better result and there's also the question of accuracy of my testing to what will happen with the loudspeaker. I have been doing critical listening for some time now and these changes very subtle. If I am going for utmost accuracy I still must consider addressing these issues.
The GD at the trouble area is 10ms in raw response, and with equalizer apo set to match that GD, everything is fine. The change is barely noticeable using tone burst of rectangular windowing, as in virtually non existent. In the measurement below is a minimum phase 48db/octave LF high pass at about 180hz. I think that is just more reason to think that I can do better with better voicing, but I won't be certain what needs to be done until I have the horn up and running again.

All and all a very informing experiment.

Last edited:
Tonight I did some more modelling. In horn resp I can ballpark the drivers characteristics but not the horn response. Horns/waveguides do not change the nature of excursion. It looks like large horns do help to curve excursion below cutoff more so than a pure waveguide but that is neither here nor there in the face of a high pass used for crossing above the F of a waveguide. Because of this, I should be able to use horn resp to ballpark excursion. I loaded up the raw response into VituixCad, and created a voicing. then I loaded the filters into Hornresp, in particular the ones near the roll off of the horn, that mattered most for this exercise. From there I could adjust voltage in vituixcad to achieve certain spl, and then try it out in hornresp to see where it might take me, excursion wise. 1db increments the graph, looks like the XO point is at about ~212hz. This isn't much different than what I've achieved with the rough voicing so far, which is probably about 215hz -6db.



Respectively this is what would be potentially asked of each horn for 115db and 110db peaks. From what I've seen 15db headroom is about standard over average and 95db average was the max safe average for something like an hour. This may explain why I have not had an issue with thd as the excursion is about 0.6mm during transients listening at 95db average, which is loud enough for me. As a system, things will keep transient excursion near half xmax and that is desirable.
@gedlee I think I've finally come over to the dark side. Maybe.... I want to have at least one source going into the XO not in a vent. One Idea I have is to do opposing walls, one driver in front one in back, that will retain the force cancellation. These speakers were meant to be put in a corner, though I did not put in specific design aspects directly for that, if I put the second driver in the back, it would help smooth FR being closer to the boundary. Playing with the Rew room sim, there isn't a huge difference between time aligned and natural response of two woofers in a corner, separated by about ~3 feet all the way to 300hz. @weltersys You commented that the sound would be more dispersed. Being that sound is emanating from a corner, this might not be a bad thing, its still centralized to a corner, with the horn. Comparable would be another sub behind the listening position. I think in this config I have to be mindful of how high I run the rear woofer, more mindful than I would with the 2nd woofer in bipolar sub idea.

I am leaning towards the bipole configuration, it seems to leave some more options open. Either way, the woofers would be out of the slot.


@IamJF I'll have to go back and read the article, but I do remember the woofers being on the floor. Its possible that for the simulation ceiling is left out?
Last edited:
  • Like
Reactions: 1 user
diyAudio Moderator
Joined 2008
Paid Member
The temporal performance would be better this way as well?
If you want to have them produce a result together, then they need to reference each other as a system. Don't worry that each driver has a different distance from the listener as long as they perform as one source, and you know the limitations of that source.
  • Like
Reactions: 1 user
Yes. Doesn't phase include GD?
Can we start from the top?
I envision, a woofer, front and back, that is time aligned and phase/gd aligned to the listeners position from 20hz to 300hz, given that it sounds to my liking. What I find questionable is the area above where the two drivers coupled, ie ~100hz. The enclosures will be in corners so I view the rear woofer plus wall, as a sort of folded horn. 300hz will be pretty buried in slope looking at a 24 and 48 db/oct filter. I know this approach I am describing will result in a more disperse sound, but it is possible that with everything aligned in the time domain, that it won't be a very significant change.

Solo main

Faux bipole



Independent woofer placed behind listener.


You can vary the FR with the position of the rear sub but, the Bipolar sim has a better FR in particular through near the top of the intended register, hence my curiosity. Not the best sim of bipolar but it is in the ball park. Look at the Vituix sim

Single front woofer

Bipolar with time alignment

It seems I should be able to improve the FR with a corner loaded bipole, is what I am getting at. Corner loaded bipole vs independent quad stereo sub placement... with the independent woofers, I am still limited to about 120hz for the low pass, correct? If still choosing to run this higher, the FR is not as refined as the Bipole. With the Bipole I can still chose to be limited to 120hz on the rear woofer, but benefit from coupling from about 100hz down plus the potential to improve FR up to 300hz if I like the sound of it running that high. I cannot simulate it, but with time alignment and phase/gd aligned the bipole response might be really good at the listening position
Last edited:
I am talking about a stereo system but in particular a bipolar woofer section under the horn. One woofer in front, second woofer in the rear. 300hz and lower if acceptable, from both woofers. Below are examples of where 300hz could land.

If I were to go the independent positioned woofer route, I would like to keep it symmetrical. The second redundant woofer would be placed behind the listener. This option is sorta straightforward. The bipole in a corner presents a better route to have all woofers running to a 200hz xo point. I pointed out 300hz because in my experience using a 48db/oct filter on the horn, up to 300hz needed to be covered to support the horn through the crossband.
Last edited: