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AHall

1802 sub port experiment

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On ‎3‎/‎31‎/‎2019 at 10:45 PM, AHall said:

This is the current response at the listening position.

 

Your measured response looks great. 

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I think I have determined that the 1802 has the capability to go nice and low with dsp. I also think that by boosting the bottom some to gain that flat response and low extension you are limiting the overall output of the sub. Information under 20hz gets sent to the subwoofer and can cause it to bottom out at moderate listening levels. Levels where the 1802 is barely warming up at say 25hz. Even though the graph looks good on paper I think not using the suggested high pass filter will limit the total spl greatly. 

 

Currently I am enjoying the extra low end extension and it will go far above reference levels, but if you want the total advertised spl I think it is best to have it roll off. 

 

My plan is to use only the 1802 for music purposes and build several large displacement 18s or a couple 24s at the back of the room to assist in ultra low LFE for movies. I think large sealed subs would be better for this duty than asking the 1802 to do something it wasn’t designed for. 

 

Anyone care to add some input on this or correct my thinking? 

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While you'd certainly be leaving auditorium-filling output on the table, you could likely close off all the ports to provide adequate excursion limitation and adjust the e.q./level as necessary.  I know I'd try that first before introducing more hardware.

 

Weren't the ports mounted on a removable circle the size of another driver?  I'd try doubling up drivers next if the first trial above fell short.

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17 hours ago, glens said:

While you'd certainly be leaving auditorium-filling output on the table, you could likely close off all the ports to provide adequate excursion limitation and adjust the e.q./level as necessary.  I know I'd try that first before introducing more hardware.

 

Weren't the ports mounted on a removable circle the size of another driver?  I'd try doubling up drivers next if the first trial above fell short.

 

There has been talk of adding a second driver. Could be worth a shot and fun to experiment with. Going from a ported to sealed cabinet might present an issue if the factory driver is ideal to be used in a sealed application with the size of box. I don’t know enough about the matter. Maybe a sub driver guru could chime in. For example with the cab size I wonder if a couple ultimax 18’s would be more ideal in the sealed unit than buying a second k-473. Which appears to be an eminence driver. 

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No guru claims here, but general experience is that ported enclosures provide zero excursion hindrance beyond that of the driver's suspension itself.  In your case the volume of the enclosure may be significant enough that closing off all the ports will add insufficient hindrance for just the one driver, but it must still offer some.  Beyond your time, the cost to experiment with closing all the ports would be insignificant at worst.

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On 4/1/2019 at 12:45 AM, AHall said:

Current update. Redid some eq. This is the current response at the listening position. Added a bit of a house curve into the peq. Still using 2 ports closed. I haven’t noticed any negative results as of yet. 

 

 

The curve looks like my curve on a Tapped Horn, but with a slightly smaller box and a 15" MTX driver with 1" Xmax. I can see where an 18" on a full horn would be a thing of beauty with gut rattling bass. Looks to me like you are doing a good tweak, especially considering your wall recess!

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3 hours ago, AHall said:

ideal in the sealed unit than buying a second k-473. Which appears to be an eminence driver. 

I would bet on it.

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On 4/12/2019 at 2:43 PM, AHall said:

I think I have determined that the 1802 has the capability to go nice and low with dsp. I also think that by boosting the bottom some to gain that flat response and low extension you are limiting the overall output of the sub. Information under 20hz gets sent to the subwoofer and can cause it to bottom out at moderate listening levels. Levels where the 1802 is barely warming up at say 25hz. Even though the graph looks good on paper I think not using the suggested high pass filter will limit the total spl greatly. 

 

Currently I am enjoying the extra low end extension and it will go far above reference levels, but if you want the total advertised spl I think it is best to have it roll off. 

 

My plan is to use only the 1802 for music purposes and build several large displacement 18s or a couple 24s at the back of the room to assist in ultra low LFE for movies. I think large sealed subs would be better for this duty than asking the 1802 to do something it wasn’t designed for. 

 

Anyone care to add some input on this or correct my thinking? 

I'm doing the same thing you are talking about. I designed a new "Super Tapped Horn" that will outperform a Danley DTS-10 with a smaller footprint (because of killer drivers), standing up to 6 ft. tall at the rear center wall. It should get to 14 Hz.. Since my Crossovers to LFE are 40 Hz., it's just an effective "air pump," LOL. Just put new tires on my trailer, so I can go buy the additional lumber this weekend! I can already use parts from the 2 I designed and not built, choosing to do one larger rather than 2 smaller subs. Got BASS??

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I really have no desire to mess with Roy’s handy work. Especially since the 1802 has been designed and tested with dual sealed, single driver with vent, and passive radiators. The current vented design is the one that tested best and made it into production. The exception to this in my mind is the original purpose was to dig low with extreme output for huge rooms or open space, cinema and concert. It wasn’t designed to dig ultra low for a home theater. So I don’t mind “optimizing” it to be more ideal in the situation I’m using it for. If dual sealed will go lower and still have awesome output while maintaining full critical listening fidelity I’d be even more happy. I fear I could introduce unwanted distortion to the system by using different drivers or changing things too much. 

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It started out with 2 drivers, the performance was much nicer with one, also a drone was next, the exact words were it got shredded to pieces. It sounds like(from asking) the best change was to block a port or 2. Other options were tried with less success, way before it became a product, the number of ports was to get maximum performance and output to do a certain job, fewer ports by blocking them is what is recommended for more depth with a slight reduction in overall output, but in a home that's not a problem I would think.

 

I'm just repeating what I was told, and I think I got it right since it's the same thing with the 1502. There are a couple of ports blocked on mine but it was a prototype and was done while tuning, it started out with more ports and tuned by blocking a couple of them off until they were happy. I was told I could block more if I wanted to go lower but have done nothing but may try it one day? I was told the difference in the 1502 to the 1802 was 2-3 db, since I'm nowhere around the limit (I guess) it makes no difference to me.

 

Be back in a few days, going to work on the museum, it's tough we have to listen to some Kp 600 and an 1802 as we work. 

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12 hours ago, dtel said:

It started out with 2 drivers, the performance was much nicer with one, also a drone was next, the exact words were it got shredded to pieces. It sounds like(from asking) the best change was to block a port or 2. Other options were tried with less success, way before it became a product, the number of ports was to get maximum performance and output to do a certain job, fewer ports by blocking them is what is recommended for more depth with a slight reduction in overall output, but in a home that's not a problem I would think.

 

I'm just repeating what I was told, and I think I got it right since it's the same thing with the 1502. There are a couple of ports blocked on mine but it was a prototype and was done while tuning, it started out with more ports and tuned by blocking a couple of them off until they were happy. I was told I could block more if I wanted to go lower but have done nothing but may try it one day? I was told the difference in the 1502 to the 1802 was 2-3 db, since I'm nowhere around the limit (I guess) it makes no difference to me.

 

Be back in a few days, going to work on the museum, it's tough we have to listen to some Kp 600 and an 1802 as we work. 

 

I’ve heard this. I always wondered specifically what “better” means when referring to the performance of a single vs dual driver configuration. Was it better distortion, output, low response, tight sound, general fidelity, etc? Maybe something else that separated them so much? 

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17 minutes ago, AHall said:

Maybe something else that separated them so much? 

 

Beyond manufacturing costs vs. MSRP?

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On 4/12/2019 at 1:43 PM, AHall said:

I think I have determined that the 1802 has the capability to go nice and low with dsp. I also think that by boosting the bottom some to gain that flat response and low extension you are limiting the overall output of the sub. Information under 20hz gets sent to the subwoofer and can cause it to bottom out at moderate listening levels. Levels where the 1802 is barely warming up at say 25hz. Even though the graph looks good on paper I think not using the suggested high pass filter will limit the total spl greatly. 

 

Currently I am enjoying the extra low end extension and it will go far above reference levels, but if you want the total advertised spl I think it is best to have it roll off. 

 

My plan is to use only the 1802 for music purposes and build several large displacement 18s or a couple 24s at the back of the room to assist in ultra low LFE for movies. I think large sealed subs would be better for this duty than asking the 1802 to do something it wasn’t designed for. 

 

Anyone care to add some input on this or correct my thinking? 

thats interesting....since the 1802 was developed for cinema use for......wait for it.....movies.  i have never seen a sealed sub used in cinema.  wonder why?

 

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1 hour ago, Chief bonehead said:

thats interesting....since the 1802 was developed for cinema use for......wait for it.....movies.  i have never seen a sealed sub used in cinema.  wonder why?

 

 

Sealed subs work better in small rooms because they take advantage of cabin gain to fill in the lower octave.

 

Cinema's or movie theaters are too large to take advantage of any cabin gain thus making them a poor choice.

 

 

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1 hour ago, Chief bonehead said:

thats interesting....since the 1802 was developed for cinema use for......wait for it.....movies.  i have never seen a sealed sub used in cinema.  wonder why?

 

Ah like you mean with it's ANEMIC low end response from a LF roll off that happen too  high up where we don't want it, is that why? LOL.

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16 hours ago, jason str said:

 

Sealed subs work better in small rooms because they take advantage of cabin gain to fill in the lower octave.

 

Cinema's or movie theaters are too large to take advantage of any cabin gain thus making them a poor choice.

 

 

so the laws of physics change.....

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7 minutes ago, Chief bonehead said:

so the laws of physics change.....

 

They do not.

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Perhaps it might be instructive to discuss pressure zone acoustics instead of guessing what it really means.  The following was taken from this link: https://www.acousticfields.com/room-pressure-zones/

 

Quote

Pressure Zones

The pressure zone of a room is defined as that pressure area that exists below the frequency of the lowest room mode. This pressure zone is dependent upon the room’s dimensions. The room’s dimensions will tell us what our lowest resonant frequency is going to be. Anything below that frequency we are entering the pressure zone.

 

Pressure Zone Pressure

The move into the pressure zone is a gradual slope within the frequency response of the room. The rate of this transition depends on the strength of the resonance. Inside our room’s pressure zones, waves of energy do not exist. The energy in the room is raised or lowered through the diaphragmatic action of the speaker driver. There are points of pressure maximum and pressure minimums within these pressure zones.

 

Look Below 100 Cycles

If the room is considered acoustically a small room, then we need to look at 100 cycles as the frequency where our pressure zones can be considered acoustically useful. The longest dimension in our control rooms should be at a half wavelength of the designed for lowest frequency we need to hear clearly without room resonance distortion. If we use 20 cycles as our designed for lowest frequency, then half a wavelength would be 28′. With this dimension, we would have no speaker response within the pressure zone...

 

If I read this correctly, in order for most listening rooms to be considered to be operating in the "pressure zone" using subwoofers having response up to 80 Hz, the room would need to be small enough to be in the pressure zone at subwoofer frequencies.  That would mean to me that the maximal room dimension would be on the order of 12-14 feet in order to be operating in the pressure zone at ~40 Hz and below. 

 

So perhaps--you're both right...just at different assumptions of room size and frequency band of interest.  In larger-sized listening rooms, there really isn't a pressure zone--say 30-40 feet long (mine is 40 feet long, so I don't deal with pressure zone, but I do have to deal with sitting inside the nearfield of the horn-loaded subwoofers--much less than 2 wavelengths).

 

Chris

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23 hours ago, Chief bonehead said:

thats interesting....since the 1802 was developed for cinema use for......wait for it.....movies.  i have never seen a sealed sub used in cinema.  wonder why?

 

 Am I incorrect in my thinking? Trying to get an 1802 to play full spl below what it was designed to do? Why not roll it off at 22-25hz and let sealed subs cover that last 10hz?

 

If there is a way to achieve what I’m looking to do with only the 1802 I’m all for it. I just didn’t want to create a bunch of distortion by boosting its bottom. Or damage the driver with ultra low freq effects. 

 

Edit for clarity -

 

My suggestion was to use only the 1802 for music due to the seamless blending with the jubes. The sealed subs would not be playing here as I believe they would dirty up the SQ by not being low distortion horns. 

 

And for movie duty I would still be using the 1802 in full force, but using the xilica to do a 24db or 48db high pass filter. The second xlr output on my anthem pre/pro would be feeding sealed subs. All subs would work together until 25hz where the 1802 would roll off and the sealed subs would continue to output down to 15hz or lower. 

 

 

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2 hours ago, Chris A said:

Perhaps it might be instructive to discuss pressure zone acoustics instead of guessing what it really means.  The following was taken from this link: https://www.acousticfields.com/room-pressure-zones/

 

 

If I read this correctly, in order for most listening rooms to be considered to be operating in the "pressure zone" using subwoofers having response up to 80 Hz, the room would need to be small enough to be in the pressure zone at subwoofer frequencies.  That would mean to me that the maximal room dimension would be on the order of 12-14 feet in order to be operating in the pressure zone at ~40 Hz and below. 

 

So perhaps--you're both right...just at different assumptions of room size and frequency band of interest.  In larger-sized listening rooms, there really isn't a pressure zone--say 30-40 feet long (mine is 40 feet long, so I don't deal with pressure zone, but I do have to deal with sitting inside the nearfield of the horn-loaded subwoofers--much less than 2 wavelengths).

 

Chris

 

This is still way over my head. Especially with my odd shaped room, half walls, and open floor concept. 

 

I am glad to have a more in depth discussion on this. I’m all ears on trying to improve the current performance and sound quality I already have.  I’m sure there is a lot of optimizing in tuning and treatment left on the table. I just have to learn how to achieve it. 

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