Predicting pressure inaction pathways and acoustic coupling.

[ciaonzo 5,000+ posts]

You fimilar with a wave guide ported alignment? The length of the port is 1/4 of the frequency the systems resonates at.

I dabble. There was a commercial product (believe it or not) that utilized a version of that. They were using small aluminum cone drivers, like 5.25" & 6", to make these oddly loaded hybrid subwoofers. It was like a transmission line and a vented enclosure hybrid. But not like the MLTQW versions you may be thinking of. But they basically loaded the cone over the entire passband so that the thermal limit of the driver was truly the limit. Excursion was never an issue.

 

[LosIsATool 5,000+ posts]

https://www.pioneerelectronics.com/PUSA/Car/Subwoofers/Powered+Subwoofer/TS-WX70DA

 

[ciaonzo 5,000+ posts]

How the Bose Wave Radio makes Big Sound

Took me forever to remember what the brand was. --> TBI Audio Systems - About the Sound
At one time they were pretty transparent about the alignment but they're pretty guarded about it now. You'd have to look up the patent.

Check out the review page as well. These tiny things stay color free and present quite a pressure wave. --> http://tbisound.com/dsp_press.asp

 

[Papermaker85 5,000+ posts]

https://www.pioneerelectronics.com/PUSA/Car/Subwoofers/Powered+Subwoofer/TS-WX70DA

I was experimenting back in the late 1990s. the 10s pounded it sound similar to a transmission line. the fell off fast up top but i had them in a big *** box for tens i wanted stupid lowend.. its tricky but the output is downright amazing because of the phase correction.. granted is only really coupling at a few frequencies properly it can be peaky unless you go really small on box volume

 

[Papermaker85 5,000+ posts]

I dabble. There was a commercial product (believe it or not) that utilized a version of that. They were using small aluminum cone drivers, like 5.25" & 6", to make these oddly loaded hybrid subwoofers. It was like a transmission line and a vented enclosure hybrid. But not like the MLTQW versions you may be thinking of. But they basically loaded the cone over the entire passband so that the thermal limit of the driver was truly the limit. Excursion was never an issue.

loading generally causes havoc on impedance. i can imagine its a highly reactive load..

 

[Papermaker85 5,000+ posts]

At 45Hz you're pretty much dealing with the energy balance in a constant pressure wave expansion or compression process ("pressure is constant throughout the system rule") more than you are the quarterwave theory.
1130ft/sec @ 45Hz = 25 foot wavelength (6.3 foot quarter wavelength).

Now, if you want to build a friggin' giant horn that results in the entire vehicle space being the mouth of that horn, you might be on to to something. You could just build a slowly unraveling ultra-long horn that ends up being the "wall" of your build. Open it up and show people that you have a single high efficiency 15" running off of 800w, loading a tiny compression chamber. You could teach the young ones.

FIY I agree with this statement hence i want to make a "guide" of sorts. After the first show I'm going to lay glass down on the trunk floor and make the maze . //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

right or wrong it will be another learning experience

 

[hispls 5,000+ posts]

I dabble. There was a commercial product (believe it or not) that utilized a version of that. They were using small aluminum cone drivers, like 5.25" & 6", to make these oddly loaded hybrid subwoofers. It was like a transmission line and a vented enclosure hybrid. But not like the MLTQW versions you may be thinking of. But they basically loaded the cone over the entire passband so that the thermal limit of the driver was truly the limit. Excursion was never an issue.

There's a reason people use horns in stadiums and concert halls (they're efficient and loud). There's also a reason people don't use them in cars (they're huge and touchy to get right).

I heard a station wagon that ran just a couple modest 10s that flared out of a horn at the B pillar... essentially took up the space of a b-pillar wall. Loud and good sound but seemed like a lot of work and materials.

Getting loud is almost never about theory, it's about trial and error.

 

[Papermaker85 5,000+ posts]

There's a reason people use horns in stadiums and concert halls (they're efficient and loud). There's also a reason people don't use them in cars (they're huge and touchy to get right).
I heard a station wagon that ran just a couple modest 10s that flared out of a horn at the B pillar... essentially took up the space of a b-pillar wall. Loud and good sound but seemed like a lot of work and materials.

Getting loud is almost never about theory, it's about trial and error.

i agree just loading the woofer dropped impedance and i gained .5...

 

[Papermaker85 5,000+ posts]

There's a reason people use horns in stadiums and concert halls (they're efficient and loud). There's also a reason people don't use them in cars (they're huge and touchy to get right).
I heard a station wagon that ran just a couple modest 10s that flared out of a horn at the B pillar... essentially took up the space of a b-pillar wall. Loud and good sound but seemed like a lot of work and materials.

Getting loud is almost never about theory, it's about trial and error.

i agree just loading the woofer dropped impedance and i gained .5...

 

[ciaonzo 5,000+ posts]

loading generally causes havoc on impedance. i can imagine its a highly reactive load..

It's the opposite. Loading the cone; As in the same way a vent loads the cone and minimizes cone motion = lessening the reactive behavior. This is even more observable with a transmission line. Measure the impedance magnitude in free-air, then compare that with the results of the driver loaded in the line. Very benign compared to free-air. Easier for the amplifier to control.

FIY I agree with this statement hence i want to make a "guide" of sorts. After the first show I'm going to lay glass down on the trunk floor and make the maze . //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gifright or wrong it will be another learning experience

But a guide of sorts would need to be very long at or below the wavelengths you're interested in. Thus, the reason I suggested the actual wavelength being supported by a coiled up horn. The line length would just need to be really long to make up for the lack of mouth area.

There's a reason people use horns in stadiums and concert halls (they're efficient and loud). There's also a reason people don't use them in cars (they're huge and touchy to get right).

I realize that, but you have to consider I was saying that mostly for effect because of what the OP was proposing. I was hoping the sarcasm would be fleshed out as the conversation went on.

 

[Papermaker85 5,000+ posts]

It's the opposite. Loading the cone; As in the same way a vent loads the cone and minimizes cone motion = lessening the reactive behavior. This is even more observable with a transmission line. Measure the impedance magnitude in free-air, then compare that with the results of the driver loaded in the line. Very benign compared to free-air. Easier for the amplifier to control.
But a guide of sorts would need to be very long at or below the wavelengths you're interested in. Thus, the reason I suggested the actual wavelength being supported by a coiled up horn. The line length would just need to be really long to make up for the lack of mouth area.

I realize that, but you have to consider I was saying that mostly for effect because of what the OP was proposing. I was hoping the sarcasm would be fleshed out as the conversation went on.

loading the cone causes increased a inductive load the opposite of resonance every parameter shifts MUCH more. its like adding weight to the cone just acoustically. therefor current goes up and so does inductance..

yes it lowers cone motion but its not because of resonance it's an air mass load created by the drive the a vacuum or lack there of so not only does it affect the outward stroke if affect the inward stroke to be loading and poorly unloading.

i understand what you are saying but the port has its own unique resonance and bandwidth as well as damping this is altering the woofers stiffness without creating another output. what i mean is the port act like another cone body and loading acts like a dampener.

im not going to argue ill take your word for it though.

 

[ciaonzo 5,000+ posts]

loading the cone causes increased a inductive load the opposite of resonance every parameter shifts MUCH more. its light adding weight to the cone just acoustical. there for current goes up and so does inductance..yes it lowers cone motion but its not because of resonance it's an air mass load created by the drive the a vacuum or lack there of so not only does it affect the outward stroke if affect the inward stroke to be loading and poorly unloading.

i understand what you are saying but the port has its own unique resonance and bandwidth as well as damping this is altering the woofers stiffness without creating another output. what i mean is the port act like another cone body and loading acts like a dampener.

im not going to argue ill take your word for it though.

No, I hear you. I was speaking in general terms for the benefit of others but you're right, the vent is a Helmholtz resonator. Adds mass at a center frequency with a certain Q. Do it wrong and you can get havoc and a nasty impedance profile. Do it properly and you can have a much less reactive load than simply allowing the driver to play free-air.
Transmission line, however, is a much wider mass loading scenario that will positively yield a very benign impedance profile.

That's all I was trying to get across in my point of comparison for a less reactive load for the amplifier to cope with. Bring down the impedance magnitude and you're lessening the capacitive and inductive phase angles on the system resonance. This is what is meant by a less reactive load. Inductance type distortion should improve as well since cone motion would be minimized, likely keeping the motor system in a range where it is not very asymmetrical.

 

[Papermaker85 5,000+ posts]

No, I hear you. I was speaking in general terms for the benefit of others but you're right, the vent is a Helmholtz resonator. Adds mass at a center frequency with a certain Q. Do it wrong and you can get havoc and a nasty impedance profile. Do it properly and you can have a much less reactive load than simply allowing the driver to play free-air.
Transmission line, however, is a much wider mass loading scenario that will positively yield a very benign impedance profile.

That's all I was trying to get across in my point of comparison for a less reactive load for the amplifier to cope with. Bring down the impedance magnitude and you're lessening the capacitive and inductive phase angles on the system resonance. This is what is meant by a less reactive load. Inductance type distortion should improve as well since cone motion would be minimized, likely keeping the motor system in a range where it is not very asymmetrical.

bows head. lol totally agree..

 

[Papermaker85 5,000+ posts]

Any ideas or suggestions?

 

[tymoto21 10+ year member]

i saw an extreme van YEARS ago online that had exactly that.

it was iirc a 15 in back and the guide was literally a big sine wave on the passenger side of the van and i think loaded into the kick. was like 10" x 10" and probably close to 20' long in total (went bottom to top to bottom)

iirc was around 170 supposedly.