I am organizing to build.
i think i will change the XT1464 to XR1496 while keeping the same crossover filter
i think i will change the XT1464 to XR1496 while keeping the same crossover filter
The non-parallel sides will help minimise dimensional resonance effects.
Enclosure shapes like this were very popular back in the early days because they fitted neatly into a corner.
And, yes, many were bass reflex designs.
Enclosure shapes like this were very popular back in the early days because they fitted neatly into a corner.
And, yes, many were bass reflex designs.
Actually, the trapezoidal box shape is popular in professional PA (sound reinforcement) loudspeakers, because of easy horizontal stacking for providing greater horizontal coverage. Not useful with only one pair of loudspeakers, or in home.
In general, the shape of the internal space in a bass reflex enclosure makes little difference in low frequency performance. If the design calls for a 60 liter box with a 3 inch circular vent that is 8 inches long, it really does not matter how the 60 liters is shaped: Box, cube, sphere, pyramid, or trapezoidal polyhedron. The exception would be a very long thin pipe-like structure, which has a somewhat different response model called "mass loaded transmission line"...
A commonly used shape where it does make a difference is when one dimension becomes significantly larger than the other 2 a BR transforms into an ML-TL and has to be modeled and tuned differently.
dave
It hasn't yet been show that there is such a problem (in this case). Such walls may make a change, it doesn't automatically improve matters.
I was quoting from 'An Introduction to Loudspeakers and Enclosure Design' by V. Capel, first published in 1988 and revised in 1991.
I guess the information must be out of date!
Oh well... 😀
I guess the information must be out of date!
Oh well... 😀
For an opposing view, the best speaker I've heard in this flyover state, Peavey SP2-(2004) has a trapezoidal box. To quote the spec sheet "The SP 2 has a trapezoidal-shaped enclosure, which reduces the buildup of standing waves inside the enclosure to minimize mid-bass and mid-range coloration."
If sound has speed of 880 ft/sec, and a bass box is 2' wide, then a standing wave could occur at 440 hz. this is right in the middle of voice frequencies.
My definition of "best" involves auditing Steinway grand piano CD's, at all piano keys. I've heard grand pianos live and know what they should sound like. Plus a test to ensure straight bass drum hits don't scoop because of a long path for the sound. (Klipschhorn?).(I haven't heard a Klipschhorn since 1978 and the store was playing jazz, trumpet string bass snare, which is not difficult source material IMHO).
If sound has speed of 880 ft/sec, and a bass box is 2' wide, then a standing wave could occur at 440 hz. this is right in the middle of voice frequencies.
My definition of "best" involves auditing Steinway grand piano CD's, at all piano keys. I've heard grand pianos live and know what they should sound like. Plus a test to ensure straight bass drum hits don't scoop because of a long path for the sound. (Klipschhorn?).(I haven't heard a Klipschhorn since 1978 and the store was playing jazz, trumpet string bass snare, which is not difficult source material IMHO).
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@ Galu
It's hard to tell without context, but some information from that era is indeed misleading or incorrect. The acid test for me is whether it leads the designer to the real issue, or needlessly into a tailspin of audiophile rules and myths.
It's hard to tell without context, but some information from that era is indeed misleading or incorrect. The acid test for me is whether it leads the designer to the real issue, or needlessly into a tailspin of audiophile rules and myths.
What's the frequency range? Are you talking a sub, or a low-mid?
If a sub, a trap box is worthless, completely counterproductive.
For a bass-reflex, you want almost invariably, as much volume vs box size, as you can get...ala a modified cube for the task at hand.
If for 100Hz up, then yes, a trap can definitely help.
Both for the ability to array, and to move/spread around internal resonances etc..
The context was air resonances that are a function of the three enclosure dimensions.
It went on to talk about Golden Ratio as applied to both loudspeaker enclosures and listening rooms.
I'm not trying to cause an argument here. This is the type of information I grew up with. We may well have moved on in our knowledge of enclosure design!
I agree.
But you can reduce that effect alot if you put the vent(s) close to the driver.
The golden ratio is a good example from the book. It has some reasonable usage today, but at other times represents a more narrow view of modal behaviour.
I'd have thought we were from a similar era. I had my introductions to a crossover in the mid '70s.. of course I didn't know then what I do now 🙂
I'd have thought we were from a similar era. I had my introductions to a crossover in the mid '70s.. of course I didn't know then what I do now 🙂
I was running a successful mobile disco in the second half of the 70s.
I employed full range 12" drivers and 12" drivers supplemented by Goodmans mid/high horns with crossovers already built in.
My knowledge of crossovers at that time was scant (still is!), but I did build my own disco mixer and lighting displays!
Happy days!
I employed full range 12" drivers and 12" drivers supplemented by Goodmans mid/high horns with crossovers already built in.
My knowledge of crossovers at that time was scant (still is!), but I did build my own disco mixer and lighting displays!
Happy days!
The 2 non-parallel walls have to have a considerable angle to signicantly reduce side-to-side standing waves, but you still have 2 pair of parallel sides, in the case of the illustration, the one with the most significant standing wave is the lnest one, top-to-bottom.
The ideal shape would depend on the goals, could be different on the inside than the outside and will change (at least in scale) depending on the frequency.
Everything is a compromise. The outside edges of your box are not ideal, for instance, wrt diffraction.
dave