PPSL means Push Pull Slot Loading, one woofer moving in the opposite direction to the other one, one pushes one pulls.
Depending on the physical orientation you can wire them differently to achieve the same thing.
To reduce width usually the magnet of one driver is made to fit in towards the cone of the other driver with the slot in the middle.
1/4 Wavelength CTC will allow the drivers to radiate as one sound source, the further away from that you get the more lobing will occur due to interference patterns emerging.
Slot loading will change the output of the drivers and depending on the size of the slot will change the compression ratio.
I think Ro808 is referring to the fact that for 1w the Axi on a big horn is going to be very efficient around 108dB, to get that kind of sensitivity out of woofers is going to need a lot of them.
Early on you set some very high spl goals, that will need a lot of woofing to get there. If you relax those and pad down the axi, there is really no issue.
Depending on the physical orientation you can wire them differently to achieve the same thing.
To reduce width usually the magnet of one driver is made to fit in towards the cone of the other driver with the slot in the middle.
1/4 Wavelength CTC will allow the drivers to radiate as one sound source, the further away from that you get the more lobing will occur due to interference patterns emerging.
Slot loading will change the output of the drivers and depending on the size of the slot will change the compression ratio.
I think Ro808 is referring to the fact that for 1w the Axi on a big horn is going to be very efficient around 108dB, to get that kind of sensitivity out of woofers is going to need a lot of them.
Early on you set some very high spl goals, that will need a lot of woofing to get there. If you relax those and pad down the axi, there is really no issue.
- Thats how I seen it done and it won't fit. There are benefits to being able to get the drivers closer together even though I sacrifice the linear suspension hack, I gain a higher amount of dampening on the face of the drivers. The benefit of having both drivers on the output plane without have to increase my box height to above 36" is much welcome too lol.To reduce width usually the magnet of one driver is made to fit in towards the cone of the other driver with the slot in the middle.
So even at 200hz lobing occurs, it would be practically 15+20" from top of horn to the bottom of the 15"...and we haven't factored in the range above the 200hz XO that still mattersthe further away from that you get the more lobing will occur due to interference patterns emerging.
Are there benefits to a compression ratio? Being a 4th order bandpass, slot loading a sealed box or a front loaded horn with driver in a sealed chamber, same diff, with a line length of 2.54cm, doesn't do much of anything to the FR....I don't even benefit from mention worthy dampening...I think I should increase the length to inside of the cone maybe? Still thats not adding enough to much the resonance into a trouble are IF I cross over are 200hz...this is in reference to what I described above, the 6 inch wide slot.will change the compression ratio.
Can't I control the sensitivity of the horn and driver? The sensitivity throws off the dynamic response to transients and large increases in source signal or we can just say source signal in general...the gain control and EQ is not enough to match the drivers is what you guys are trying to tell me?Axi on a big horn is going to be very efficient around 108dB, to get that kind of sensitivity out of woofers
I have horn resp to model loudness potential...I'm not sure the confusion? I'm personally confused about why sensitivity of the driver needs to match. I think I know why, but it'd be nice to hear the text book answer.Early on you set some very high spl goals, that will need a lot of woofing to get there. If you relax those and pad down the axi, there is really no issue.
Just to make sure we are in agreement to what one channel looks like axi2050+td15m+18h++18h+
After eqing the response flat you think I'll have a 108 sens? Even with manly reductive eqing only?
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I hope I explained myself clearly on the polar issue with CTC...If you used xdir to plot out every single active radiating plane distance point, from bottom of the woofer to the top of the horns output, to the highest part of the woofer vs the lowest part of the horn....sum all those together and youd get the whole picture right?
This makes sens because in Xdir theres no settings for driver size.
So CTC is a general rule but not the end of the story.
This makes sens because in Xdir theres no settings for driver size.
So CTC is a general rule but not the end of the story.
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In most cases you'll need to attenuate a horn + comp. driver to match the output of the other (usually lower freq.) channels. You might want to attenuate the freqs below the point where the Axi starts to drop. This way you'll probably end up with around 100dB, which is still very respectabele.
However, a lot depends on the type of horn: CD or Salmon family.
However, a lot depends on the type of horn: CD or Salmon family.
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For a (nearly) fullrange 2 way - or 3 way if a coaxial is used - MEH, I was contemplating a solution using 2 x 15" woofers with very low Qts (0.17) that are backloaded, or otherwise vented. For people who don't need, or can't have sub bass (eg due to neighbours), such a system might be of interest.
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I am personally not sold on the benefits of Push Pull slot loading, I can understand the desire in some circumstances to get vibration reduction from opposing drivers though. The 18" driver you have is not really designed as a very low frequency subwoofer.
Is there a reason why you are looking at PPSL?
When you start to get into the transition region in a room directivity is likely to be a mess, if you are crossing above 500Hz then keeping the CTC within 1/4wl or close to it shouldn't be too hard.
In an active system there is no need to have the sensitivities match, you can drive the different sections with whatever power they require. In a passive it helps to avoid dissipating power in resistors.
There are enough designs and information available on MEH to allow anybody with a table saw or tracksaw to build one. They certainly offer a lot of advantages, a big waveguide built into an enclosure with a 15" driver below also seems to be a simple and high quality way to go also.
Is there a reason why you are looking at PPSL?
When you start to get into the transition region in a room directivity is likely to be a mess, if you are crossing above 500Hz then keeping the CTC within 1/4wl or close to it shouldn't be too hard.
In an active system there is no need to have the sensitivities match, you can drive the different sections with whatever power they require. In a passive it helps to avoid dissipating power in resistors.
There are enough designs and information available on MEH to allow anybody with a table saw or tracksaw to build one. They certainly offer a lot of advantages, a big waveguide built into an enclosure with a 15" driver below also seems to be a simple and high quality way to go also.
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[QUOTE]I'm super happy with it. I had four 12 inch subs and they are unhooked and I need to sell them. This dynamics of this thing is really good. There is an explosion in "Valkyrie" that shows it off really well. The explosion must be like 30 db higher than the dialog and it handles it with no distortion that I can tell. Sounds liken a real explosion.The 18" driver you have is not really designed as a very low frequency subwoofer.
The big thing for me was the music . I mentioned before how I felt like I got a speaker upgrade and that feeling remains. I didn't realize before how much subs affected the sound of your speakers above the crossover. The sub 20 Hz stuff that I'm missing isn't very noticeable.
Its a big box though. 8 cubes is a Large Marge. I haven't finished it yet as I have almost no time. The driver is expensive although not as much as the 2242h. While the missing sub-sonic isnt noticable most of the time, I DO miss it. The cannon shots in Master and Commander, for example, used to make my couch feel like it became liquid. I dont really get that now.
I never planned for this to be a complete replacement though. If Kevin ever gets the 21s going, Id like to use one to cover the lower freqs, maybe hand off to the TD at 25 or 30 Hz. If I could just have one sub though, Id stick with this one for the sound quality I get for the biggest percentage of my listening.
I scanned around a little and It doesn't look like any one else has taken the plunge on one of these.
Anybody local is welcome to stop by for a listen.[/QUOTE]
First Look - TD-18H+ - Page 3 - AVS Forum | Home Theater Discussions And Reviews
Considering the application, music studio subwoofer, I think 2 on each side is perfect.
Its a way to put their output on the same plane, is the main reason. Otherwise I would have one face me and one face the floor. To stack them is too tall. Front firing is the most accurate.Is there a reason why you are looking at PPSL?
I feel confident that I can get 300hz out of these 2 Jbl horns (2386 or 2380a)....Docali and Don K's horn will be my only bet for any lower
I am aware that horns that beam in HF are also more sens/efficient on axis in the upper range.
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I have no intention of arguing with you, to me a subwoofer is primarily working in the 60Hz down frequency range and if the driver does not have much output below 30Hz then it is not designed as a subwoofer. That does not in any way make it a bad driver or something that should not be used in a high quality system.
Most music has very little content below 30Hz but an increasing amount has some really significant sub 30Hz content whether by design or ommission it is not always easy to know. If you intend to master music it seems important to have some ability in the system to recreate these frequencies.
My old Orion system had a 6dB low cut filter at 30Hz to avoid LFE from throwing the woofers beyond their stops. When listening to music on a lot of older classic stuff the position made no difference to the sound. I have a lot of tracks in my collection now that it would have.
When I run sweeps on my line arrays I have to make sure I start them at 10Hz otherwise they excite a massive 5Hz resonance in my walls which is quite disconcerting.
Now I have the ability to hear or feel these frequencies it certainly adds something that I would not want to be without. This is also something Floyd Toole has written about his own personal system that comes from him using a number of sealed subwoofers, that he enjoys finding tracks that have this sort of low bass.
Most music has very little content below 30Hz but an increasing amount has some really significant sub 30Hz content whether by design or ommission it is not always easy to know. If you intend to master music it seems important to have some ability in the system to recreate these frequencies.
My old Orion system had a 6dB low cut filter at 30Hz to avoid LFE from throwing the woofers beyond their stops. When listening to music on a lot of older classic stuff the position made no difference to the sound. I have a lot of tracks in my collection now that it would have.
When I run sweeps on my line arrays I have to make sure I start them at 10Hz otherwise they excite a massive 5Hz resonance in my walls which is quite disconcerting.
Now I have the ability to hear or feel these frequencies it certainly adds something that I would not want to be without. This is also something Floyd Toole has written about his own personal system that comes from him using a number of sealed subwoofers, that he enjoys finding tracks that have this sort of low bass.
How do you think it is more accurate to have a speaker facing you or facing the floor when it is radiating omindirectionally?Its a way to put their output on the same plane, is the main reason. Otherwise I would have one face me and one face the floor. To stack them is too tall. Front firing is the most accurate.
This driver has more output at 30hz than a Dayton Ultimax18.
Heres excursion at 100db 30hz in a 380 lt sealed box.
The shorter path from driver to ear.
Heres excursion at 100db 30hz in a 380 lt sealed box.
How do you think it is more accurate to have a speaker facing you or facing the floor when it is radiating omindirectionally?
The shorter path from driver to ear.
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That graph illustrates exactly my point. The difference between the horizontal lines is much greater on the TD18 it wants to thump out midbass and above, you can flatten the response out by EQ'ing the higher frequencies and you end up with a response that looks a lot like the Ultimax as is. The Ultimax is designed to be a subwoofer the TD18 is not. But in a sealed box with a lot of power or a lot of box and some EQ you can end up at the same place if the volume displacement is there. So the TD18 is flexible it can do both things, the Ultimax not so much.This driver has more output at 30hz than a Dayton Ultimax18.
Very low frequency reproduction comes from a sealed box with enough volume displacement to get to your desired SPL. That is either cone area excursion or a combination of the two.
For these sorts of comparisons I like to use Jeff Bagby's Woofer Designer spreadsheet as it has a linkwitz transform option. That allows an apples to apples comparison of drivers when EQ'd to the same target and Q. It shows how much box or how much power is needed to get to the displacement limit. Maybe Hornresp can do the same with the active filters I have never really tried.
Are you joking now I really can't tell.The shorter path from driver to ear.
Do you think there are some disadvantages to facing them in the slot? And no joke, If I have a secondary redundant driver whos output I can merge into one....thats a no brainer? or do I have....no brains XD
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Do you think there are some disadvantages to facing them in the slot? And no joke, If I have a secondary redundant driver whos output I can merge into one....thats a no brainer? or do I have....no brains XD
Ime, the big advantage of opposed sub drivers is the very large drop in cabinet vibration. This is of course for either push-push or push-pull.
I did not measure any significant difference in THD between push-push and push-pull, so I'm not in the crowd that thinks THD is reduced by push-pull.
I do hear more coil vent noise with push-pull, where one driver's coil is in the slot.
So imo, push push is the way to go, especially since the td18th+ has a phase plug that may be a problem clearance wise for push-pull.
Because the width of the slot will determine how high in frequency the sub can be used, where width equals about 1/4 WL. Given the td18+'s rather tall 12" height, you'll probably have to rear mount the drivers and have external access plates. IOW, you can't fit them in thru the slot which would need to be over 13" wide, and need xover at / below 250Hz.
Also be aware the slot will provide a strong resonant boost underneath the width cutoff that will have to be EQ'ed out.
Honestly I think cabinet vibration reduction is the only real advantage....but it is a huge advantage imo.
I have to agree with Fluid that the td18+ is more of a mid-bass driver than a sub driver, and it's really sub drivers that benefit so greatly from opposed force cancellation..
So, I dunno about push-push here....not sure it's worth the effort.
The 18h+ is whatever you can get it to....and it plays to 30hz just fine. I bet you think the TD15H is the better "SUB" woofer?
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The 18h+ is whatever you can get it to....and it plays to 30hz just fine. I bet you think the TD15H is the better woofer?
I think that the point was it(18H+) is not a sub woofer. Reproduction of 30 Hz is not sub woofer bass territory it is bass.
Open baffle designs have shown that the drivers be mounted close to with no issues. Heck the formula for the OBSL is 1/4 length of diaphragm width equals slot width...I'm also just about 1/2 length and the testimony in PPSL thread on the subwoofer forums have testimony of various designs within these ratio with no issue....I feel an approximation of the effect can be modeled by halving the csa.
argueing semantics sub woofer xover for THX is 120hz. Wiki says sub-bass is 60hz and under...who really cares? I'm going to use the 18h+ to cover ~65hz-30hz and its going to be a good thing. Not worried about the title.Reproduction of 30 Hz is not sub woofer bass territory it is bass.
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Moray probably refers to the fact that 30-something Hz is within reach of (low) woofers and even some mid-woofers. You'll need subwoofer drivers to go below 30Hz.
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Earlier in this thread, the subject of (woofer) intermodulation distortion was discussed.
A French guy thoroughly tested a bunch of 10" woofers, mostly typical hi-fi drivers, and included IMD.
It's interesting to learn (though not surprising) the most expensive and overall best performing woofer
scored worst wrt IMD, notably with the double sine 30Hz + 500Hz.
A French guy thoroughly tested a bunch of 10" woofers, mostly typical hi-fi drivers, and included IMD.
It's interesting to learn (though not surprising) the most expensive and overall best performing woofer
scored worst wrt IMD, notably with the double sine 30Hz + 500Hz.
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