I see many speaker mfs position their ports near the floor for best room integration as they say.
However, acousticans often says that placing a vent or driver near a boundary gives a gain boost and you excites room resonances maximally, which more often is a bad thing as they say.
So what is really the best location?
In my mind, a small monitor with limited low freq output could benifit by a vent location near the floor to gain some boost, but a big loudspeaker with lots of low freq output, with the vent near the floor, has the potential to give an overblown bass response?
However, acousticans often says that placing a vent or driver near a boundary gives a gain boost and you excites room resonances maximally, which more often is a bad thing as they say.
So what is really the best location?
In my mind, a small monitor with limited low freq output could benifit by a vent location near the floor to gain some boost, but a big loudspeaker with lots of low freq output, with the vent near the floor, has the potential to give an overblown bass response?
Why don't you measure it?
Small speaker on stand vs small speaker on floor.
Then compare bass responce at listening position.
Small speaker on stand vs small speaker on floor.
Then compare bass responce at listening position.
Possibly because he, like me, does not have the equipment and sees no reason to spend £/$ 100s to find an answer, that clearly you already know, but are unwilling to impart...
1 I don't know the answer, because I don't know his room and speakers.
2 investing in proper tools will save you money in the long run.
just what i meant, mfrs often choose vents near the floor, is this really any good or is just a hype?
IMO
Port placement near floor has to be optimised according to the box tuning and driver's abilities.
It's a handy technique to extend the response down half an octave or so *if done well*. My sense is that it's best used in cases where the room modes are benign to begin with (which means room remains the most important thing anyway), and the box/driver combination does not excite those modes.
The few times I've tried it it seems to work well. A front-facing port near the floor can be used to prevent some floor bounce associated with two-way speakers with a high-mounted midbass driver. Also reduces midrange leakage a bit without requiring a rear-facing port (which has its own issues). However am unsure if it actually helps the bass response.
A downfiring port is the toughest nut to crack and will *not* sound good everywhere. I've built an example of each, both with very different driver combinations and design goals, and both have worked out quite well.
Previously my attempts with downfiring subs and ports were less than successful because I was trying to push for unachievable results. Once I began tuning the box higher, I had better outcomes.
Port placement near floor has to be optimised according to the box tuning and driver's abilities.
It's a handy technique to extend the response down half an octave or so *if done well*. My sense is that it's best used in cases where the room modes are benign to begin with (which means room remains the most important thing anyway), and the box/driver combination does not excite those modes.
The few times I've tried it it seems to work well. A front-facing port near the floor can be used to prevent some floor bounce associated with two-way speakers with a high-mounted midbass driver. Also reduces midrange leakage a bit without requiring a rear-facing port (which has its own issues). However am unsure if it actually helps the bass response.
A downfiring port is the toughest nut to crack and will *not* sound good everywhere. I've built an example of each, both with very different driver combinations and design goals, and both have worked out quite well.
Previously my attempts with downfiring subs and ports were less than successful because I was trying to push for unachievable results. Once I began tuning the box higher, I had better outcomes.
Interesting! It sounds correct that if the tuning freq of the down firing vent is below floor/ceiling standing wave resonance then there will be no excitation. a down firing woofer however, that has a wider bandwidth, will excite this resonance. This woofer will benefit from being lifted up from the floor for minimum excitation.
Do keep in mind that if the speaker in question is a floorstander (likely) with a vent at the bottom and the driver near the other end, you likely have an ML-TL not a bass reflex.
dave
dave
What is the difference? Will the low freq response differ much? Will the impedance response look any difference to a bass reflex?
That charge that he knows the answer but is unwilling to impart.... is not supported by the available information. Could you share how you got that....?
A bass relex needs to has approximately “cube” dimension ratios. As one dimension grows wrt the others it transitions into a transmission line (mass loaded by the testricted vent (aka port)). The transmission line can go lower as it takes advantag eof the quarter-wave resonance. A port choosen using a BR modeling program will be wrong.
dave
Any tall and relatively skinny bass reflex should be modeled as a MLTL as the long axis will produce strong mid-bass ripples that color the sound. At very least you will need to use more stuffing to damp the pipe resonances.
I've never had any difficulty with downfiring ports working as designed, nor had any particular problems with them. It's my go-to default arrangement.
for those floor standing models i have seen, it is quite common with half wavelength resonance, around 150hz for a 1.1 meter tall enclosures, i do not think i have ever seen resonances half of that.
To have a half-wave resonance the box/pipe would need to be sealed or open at both ends. If it has a hole in it, it can only be a quarter-wave resonator.
dave
dave
I do not understand, please look at stereophiles latest spendor review, is there quarter wave resonces seen in impedance and near field plots?
Spendor A7 loudspeaker Measurements | Stereophile.com
Spendor A7 loudspeaker Measurements | Stereophile.com
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