To get a reasonable match between the 6.5 and waveguide I needed to put a bit of a downslope to the on axis, this gave a nice in room slope and smooth on axis and listening window but not flat. There is a bit of diffraction between 7 and 10K where I dipped the on axis to reduce a power response increase. The crossover is at 2K which funnily enough is the same as Purifi chose for their SPK16. If it is lower which the waveguide can easily do there is a massive DI bump from there being too much directivity in the combination. A smaller waveguide could possibly allow a lower crossover or the current one needs a bigger woofer or maybe a cardioid woofer to stop the DI increase in the woofer.
In this version there is a phase offset to flatten the DI and make all the slopes smoother. I have a phase aligned version that doesn't look much worse, hard to know if one would sound really any different to the other.
I think the overall speaker looks reasonable and it has a preference rating of 8.7 with the Vituix standard options.
As these are not my own measurements I can't speak to what they might sound like. Still some way from being in a position to listen myself.
Of course the downslope could be taken out and it would make the normalized polar look prettier but it would then likely be brighter and it would cause the inroom to curve as the woofer has a natural downsloping rising DI where the waveguide is inherently flatter until 10K.
I wonder what the SPK16 looks like in a CTA2034 plot as I have only seen the polar depiction.
In this version there is a phase offset to flatten the DI and make all the slopes smoother. I have a phase aligned version that doesn't look much worse, hard to know if one would sound really any different to the other.
I think the overall speaker looks reasonable and it has a preference rating of 8.7 with the Vituix standard options.
As these are not my own measurements I can't speak to what they might sound like. Still some way from being in a position to listen myself.
Of course the downslope could be taken out and it would make the normalized polar look prettier but it would then likely be brighter and it would cause the inroom to curve as the woofer has a natural downsloping rising DI where the waveguide is inherently flatter until 10K.
I wonder what the SPK16 looks like in a CTA2034 plot as I have only seen the polar depiction.
Nice results @fluid .
What will be your listening-distance ?
Reason asking is that my understanding of the predicted in-room response that is is ment for "far" listening, so 2 to 4 meters. And this is what my situation is, so my room curve applied in active filtering is based on the pir's of midrange and tweeter. It is the best result ,audibly that is, so far.
What will be your listening-distance ?
Reason asking is that my understanding of the predicted in-room response that is is ment for "far" listening, so 2 to 4 meters. And this is what my situation is, so my room curve applied in active filtering is based on the pir's of midrange and tweeter. It is the best result ,audibly that is, so far.
I'm not 100% sure where these might end up but normally I would be about 2.5 to 3m away. I don't view something with this wide directivity to be best suited to listen to close up hence the choice to favour the in room slope over the on axis being flat in the preliminary crossover variations. With other speakers at that sort of distance I have found a measured in room of -1dB/oct to be a good place to start for overall tonality.
The DI of the tweeter waveguide is a nearly constant 5 dB from 1.1k to 9.5k. That is really impressive.
That is interesting. In my Purifi-waveguide project, I also found that the best CTA-2034 performance required a phase offset of about 45 degrees between the two drivers. I was able to get a plot of sound power, PIR, and DI that was nearly perfect. But in extended listening, I preferred the phase matched version, even though the DI and PIR curves were a little more lumpy.
j.
I agree with you Jim. Maybe Troels and his many stepped baffles are the best way, for passive versions at least.
32mm roundover on these, largest I could fit in my table.
I have a miniDSP 2x4HD I hope to utilize to try and do some listening but might be a while getting everything into the listening room.
32mm roundover on these, largest I could fit in my table.
I have a miniDSP 2x4HD I hope to utilize to try and do some listening but might be a while getting everything into the listening room.
I am the last person to criticise you for how long anything might take lol
Isn’t this simply because popular crossover topologies we use these days don’t have a sound power curve that is in line with the SPL curve? Remember the 3d order Butterworth topology…
Not by hand now and I would need to dive deep. But it’s not so hard to comprehend. Most of our beloved topologies steer on equal phase in the transition range. On axis that delivers an SPL of +6dB. Not so off axis. The sound power addition stops at +3dB (assuming comparable sound source behavior). Leaving you with a SPW dip when equalized flat on axis. But creating a deliberate phase ‘mismatch’ the on-axis SPL easily drops, bringing it closer to the SPW with some fiddling. Whether passive or active doesn’t matter by the way.
Yeah, the classic BW3 filter naturally creates a 90 degree (or 270 degree) phase shift between the high pass driver and the low pass driver. Both on-axis and sound power will sum flat, in theory...
I do not really understand where the desire for equal phase behavior of drivers in the transition region stems from. Like your ears would notice the difference… and how would they do that?
I suppose SP fails when destructive interference occurs in certain directivity/phase dependent locations - thats where energy disappears and it will never appear again - hence, the total power output vs frequency diverges form the on axis FR.
//
Vertical measurements were made and included in the previous Vituix scrennshots even if the directivity plot wasn't shown.
Well for higher frequencies thr alteration of the sound enveloppe perhaps? A topic mr Griesinger has touched upon.
My small experience on auditibility of phase, not something absolute truth, just something I've observed and could be true or wrong conclusion. Experiment yourself to find out whether you can hear changes in phase, or time.
- try easy test with active system if someone has such thing freely adjustable: add delay to your tweeter, like 3ms, anything silly but less than 10ms or so, where it becomes distinct separate sound. If you listen other side of the room, where room reflections are loud compared to direct sound, there is very little if no difference at all. I was adjusting the delay live and almost nothing happened until the tweeter became clearly separate sound at 10ms or so. I would notice some frequency response dip but "quality of sound" would stay the same regardless of "phase match at xo". I like to associate this to the Griesinger stuff that listened otherside of the room it's just noise for brain, brain isn't focusing to the sound at all and perception is just that, a mush, no matter the phase of the speaker because room reflections mix up the phase information regardless.
- repeat the delay test listening at close proximity, where direct sound is loud compared to room reflections and there is some audible difference beyond the simple frequency response change. One might hear this in elevation of sound for example, but it's likely about listening skill whether one can detect it or not, I mean it doesn't seem to be something immediately obvious and even quite severe phase mismatch could go unnoticed very easily as long as it's static, when nobody is tweaking it while you listen. Tweaking ought to make it more readily audible, you'd likely detect something is changing. Perhaps directivity and room acoustics matter also, crossover frequency, how audible this is.
- most distinct difference that seems to follow with all this phase and time stuff is in tangible feel of sound, which either is there or not. It's not the sound as such, a speaker can have flat frequency response and sound good and fine, but be kind of lame at the same time, without impact. It's almost not something that your ear picks, but what your other senses pick. Get everything right, including this phase and timing, and the sound seems to get this tangible feel to it.
- Also, if one counts in brains ability to focus on a sound is based on preserving original harmonics, Griesinger stuff, then nice small excess group delay and phase matching and listening height and all that relates to it might matter, at least in some cases where xo is at some important bandwidth that matters for brain ability to focus on the direct sound, and listening distance is short enough room reflections ain't ruining it anyway.
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"Otherside of the room" , HiFiNewsandRecordReview many many years ago did a blind review of several loudspeakers, and one attendant could predict 100% which loudspeaker when being in the hallway next to the listening room. But in the room not so! If Toole mentions a listener learns the room, the phase etc is not so mixed up for the listener as the microphone based recording would suggest. There is still a direct sound!
My experience is that when phase (time) and SPL are linear, even outside of the listening area the sounds do not fall apart into mush, up to into the garden.
A major improvement over the previous speaker config, which was passive and had a polarity of bass flipped.
My experience is that when phase (time) and SPL are linear, even outside of the listening area the sounds do not fall apart into mush, up to into the garden.
A major improvement over the previous speaker config, which was passive and had a polarity of bass flipped.