WHile technically mass-loaded by the damping in the line, it it just an aperiodically damped TL. If heavily tapered one has less issues with harmonics (they move up so are easier to damp), and shorter so often easier to put into the box.
Bill Perkins in his PR-2 paper shows that transient reaponse in an aperiodic enclsoure is very good.
https://www.pearl-hifi.com/03_Prod_Serv/PR2/PR2_Content.html
dave
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Sure. If you don’t use an electric highpass. The Q=0.5 becomes moot when you’re crossing at 250Hz. And the Q changes likely because the high pass section has an impedance too, actually.
You mean in the passband of the high pass, rigth ? Or just because with a mid phase/impedance is impacted by the seam with the low pass of the botom driver ?
I mean that the summing of both high pass functions (the electro-acoustic one from the driver in the enclosure and the electric one from the crossover) together form the highpass function. In 90% of the cases the electro-acoustic function is underlying and in such a way that virtually any topology up to high Q values can be used without noticeable consequences. Of course the electric part has to be executed well enough for that.
Even when you take the driver and enclosure natural high pass function into the equation, you'll see that rather higher Q's than lowish ones help in finding the right tuning. Take the QB3-tuning: that nééds a relative high Q of about 1 just to get the filter slope correct.
Even when you take the driver and enclosure natural high pass function into the equation, you'll see that rather higher Q's than lowish ones help in finding the right tuning. Take the QB3-tuning: that nééds a relative high Q of about 1 just to get the filter slope correct.
In my case the 250hz x-over is active and the 3k is passive. Am I better using a larger enclosure to get the QTC down or would it be better to leave it where it is?
I'd say: make it even smaller and reduce internal cavity resonances you'd have to dampen otherwise (since an enclosure that is too small for standing waves won't show them). Qtc is only of use for fc-regions. 250Hz is about 2 octaves above. Do you really think Qtc would matter?
I'm still quite new to this and on the steep part of the learning curve.
I was under the impression that with a sealed enclosure, the volume of the box also determined the compliancy of the air inside, ie a smaller box would provide a stiffer spring against the movement of the drive unit. The main issue being that there is a happy medium between too little or too much "spring" when trying to get the best transient response. Does this only apply to lower frequencies? Have I got completely the wrong idea about this?
I was under the impression that with a sealed enclosure, the volume of the box also determined the compliancy of the air inside, ie a smaller box would provide a stiffer spring against the movement of the drive unit. The main issue being that there is a happy medium between too little or too much "spring" when trying to get the best transient response. Does this only apply to lower frequencies? Have I got completely the wrong idea about this?
The 2nd order roll-off of a sealed box can be used as the HP filter, but in practise this is rarely seen. Often becaus eit is lower than the designer wants to go.
Much more often we see the 2nd order roll-off at the top (in a well controlled driver) is used as a LP.
dave
Much more often we see the 2nd order roll-off at the top (in a well controlled driver) is used as a LP.
dave
In general that spring is relevant up to about 2 x fc. Above that frequency the radiation impedance of the air directly near the cone begins to dominate the ‘counterpressure’ that the cone experiences when moving. The cone doesn’t ‘see‘ the volume of the box as a load or a spring any more. So forget about Qtc in these situations.
But what about the low half part of the baffle step ? Could be used as a part of a filter slope ? Is it a usual slope like -6 dB octave ? If the woofer has a very low fs as some modern one, perhaps adding a cap could make a second order(ish) medium high pass around the low of the bafle step bellow the Schroeder frequency of the room (so more forgiving for the ears?) ?
Many here gave up and went to open baffle mid, lol ! But the life, cabinets are hard for midranges !🙂
Bafflestep is a different issue. I have never had any speakers that required addiitonal “EQ” to deal with this.
I do think the need for bafflestep is often over emphasized. EQing the on-axis to be flat (if it isn’t already) will also raise the room response an equal amount above where it should be. One has to be cautious, but then again it seems many like too much bass. Of the hundreds of loudspeakers we have built only one ever had an BS EQ. And that was later fixed by swapping in FA22 for the $10 blue & yellow specials that needed EQ.
dave
I do think the need for bafflestep is often over emphasized. EQing the on-axis to be flat (if it isn’t already) will also raise the room response an equal amount above where it should be. One has to be cautious, but then again it seems many like too much bass. Of the hundreds of loudspeakers we have built only one ever had an BS EQ. And that was later fixed by swapping in FA22 for the $10 blue & yellow specials that needed EQ.
dave