Resistive vent, can I model this is Horn Resp....
So sealed seems straight forward....big box, put some stuffing in...done
Restive vent, it would be nice to model it first.
So sealed, resistive vent, and a basic full stuffed TL are applicable it sounds like. Sometimes I wonder if I should just take my MLTL design and stuff it full length and increase density until impedance drops enough....I've read information saying that if the stuffing material density gets too high, it can be a bad thing...it could be misinformation....HornResp won't let you use the "calculate" function and keep fill material in the equation so I cannot monitor the effects of dampening material on the pressure, backside, of the diaphragm....the more fill material, the higher internal operating pressure but to what degree....can't say.
So sealed seems straight forward....big box, put some stuffing in...done
Restive vent, it would be nice to model it first.
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We now return to regularly scheduled programming. 🙂
We now return to regularly scheduled programming. 🙂
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Re high levels of damping, no, not misinformation, it's a perfectly correct law of mechanical engineering. If you increase packing density sufficiently, it will eventually transition to behaving like a solid mass.
You can model a resistive vent in regular box modelling software by adjusting the port frictional losses.
Re high levels of damping, no, not misinformation, it's a perfectly correct law of mechanical engineering. If you increase packing density sufficiently, it will eventually transition to behaving like a solid mass.
You can model a resistive vent in regular box modelling software by adjusting the port frictional losses.
Neutral - 3a: not decided or pronounced as to characteristics
tone- musical or vocal sound with reference to its pitch, quality, and strength.
My post wasn't helpful, put it this way.. Some of that rear energy is part of the resonance. Say you have a woofer with a Q of 0.3 and you put it in a box to make it 0.7 If you somehow eliminate the effects at the rear of the cone the Q goes back down to 0.3
If you truly have an ML-TL that was properly designed, you should not have to use stuffing beyond the first half of the line's length, or a stuffing density higher than 1 lb/ft3. If you stuff beyond the first half of the line, there will be more and more of a detrimental effect on bass response, and if you continue, especially if you stuff all of the line, you will completely eliminate any contribution from the port to providing bass response. If you have a negatively tapered TL, stuffing in the first 2/3 of the line is usually optimum, and stuffing beyond that will have the same detrimental effects on bass response.
Paul
Paul
That is very interesting! I'm ok with low Q but eventually there has got to be point where it becomes too much...without being able to monitor how adding fill effects pressure behind the woofer in modeling....you cannot say that your modeled TL is going to sound good if you chose a combination of stuffing density, length and CSA that lowered Q to the point of detriment. I'm scared to model anything over 100 density lol. I also theorized that if I kept my eye on driver only output that I am probably fine...a severly dampened system is going to start to loose output in the driver only spec...I believe...could be wrong about that too...sounds good...
So the sealed box or resistive vent seems like the choice for me, resonance cannot be had without penalty of decay so who wants it anyway. How isn't the resistive vent going to have output and added decay? if its just another vented alignment?....maybe I've cornered my self into the large sealed alignment?......I dunno, I still want to model one....I don't know if Horn resp allows me to control the "port frictional losses"
...it seems like the dampening feature would do the trick but I haven't modeled anything that made sense to me.
Nothing is without sacrifice....I'll take low group delay and low decay over higher bass sensitivity.
Allow me to be more on point. A closed box, a simple bevaving device, box like in shape not elongated making it acoustically small at these lower frequencies.
There is only one mode of propagation for the rear wave around the frequencies of resonance, to pressurise the box. The result manifests itself as seen in a pressure measurement. There is no hidden action, colouration etc., what you see is what you get. In other words, no need to eliminate it, just to adjust it where you want.
Throwing a hand grenade, is there any real objection to the quality of bass from an aperiodic type enclosure?
That's the first time anyone has told me that, but I like it, it makes sense to me....so why use an aperiodic vent if there's nothing to gain? From what I've read, an aperiodic vent increases sound quality, and reduces, resonant ringing in the box....aka pressure. This resonate ringing at tuning, changes the tonality of hte signal being transferred. If that doesn't really happen then aperiodic is pointless.
If your aim is an aperiodic box. The length of the line makes aperiodic easier IMO.
dave
Depends what you are trying to gain. An aperiodic box (aperiodic vents are sorta minimalist band-aids IMO, use them when you have too, but if you are starting from scratch) does some things that are useful sometimes.
I have mentioned a real benefit in the above post, if you have a highish Q driver it can help tame them, and in a midTL it makes a passive XO easier.
dave
What Dave said. It isn't pointless.
For a start it depends how you define 'sound quality' since this is a purely subjective phrase without definition that varies from person to person.
A resistive (usually incorrectly described as an 'aperiodic') vent simply bleeds off some internal pressure. The most common use is when the desired size of sealed enclosure produces a higher system Q (Qtc) than you wish. By bleeding off some pressure via a resistive vent, the effective system Q is lowered toward whatever the target might happen to be.*
Sometimes they are also used to reduce the impedance peak at resonance, most often for midrange drivers since it makes crossover design easier, but generally an aperiodic TL is a more practical and effective means of achieving this.
*It will eventually unload at 24db/octave, but usually at a very low frequency & level.
There are two ways this can be interpreted. It may sound as though resonant ringing is something to be avoided. In fact it is nothing more than a dramatic way of saying a lower Q like you get with a larger box.
@planet10 & @Scottmoose
Hopefully soonish I will have an answer to two questions. I have been planning to put my HPM-100 woofers into 2 cu.ft. upright boxes with 20 sq.in. aperiodic vents. I'll be doing the measure, stuff, measure, stuff ritual. Above them will be Econowave horns.
I want to find out if this will give me reasonably low, very tight bass.
I am also curious how this enclosure will affect the midrange.
This will be driven by a Nakamichi PA-5 amp via a passive crossover.
If it is promising, I have another PA-5 so I can go to an active crossover.
As usual it is all about trade offs. In the case of bass response, it is size vs Fc, Qtc and volume. To get volume while minimizing dynamic compression requires big drivers so the TL would be massive.
In the midrange, it's about avoiding coloration.
I think it's kind of interesting that Wilson uses a kind of aperiodic loading for their midranges. So far my experiments in the same sort of thing are sounding quite good.
Hopefully soonish I will have an answer to two questions. I have been planning to put my HPM-100 woofers into 2 cu.ft. upright boxes with 20 sq.in. aperiodic vents. I'll be doing the measure, stuff, measure, stuff ritual. Above them will be Econowave horns.
I want to find out if this will give me reasonably low, very tight bass.
I am also curious how this enclosure will affect the midrange.
This will be driven by a Nakamichi PA-5 amp via a passive crossover.
If it is promising, I have another PA-5 so I can go to an active crossover.
As usual it is all about trade offs. In the case of bass response, it is size vs Fc, Qtc and volume. To get volume while minimizing dynamic compression requires big drivers so the TL would be massive.
In the midrange, it's about avoiding coloration.
I think it's kind of interesting that Wilson uses a kind of aperiodic loading for their midranges. So far my experiments in the same sort of thing are sounding quite good.
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