Regarding ULF and Mid bass - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 41 Old 04-23-2019, 01:42 AM - Thread Starter
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Regarding ULF and Mid bass

I understand what chest punch is, I understand what ultra Low Bass is and the difference in how it sounds. But what I don't understand is when people say they are missing mid bass and for example a VBSS will give you more mid bass oomph than a UM18 is that people tend to aim for a flat response, which, as I understand it, only depends on the lower frequencies rolling off, sooner or later and sometimes a room curve is added to detect more bass in the Ultra low region, so I guess what I'm asking is how can a flat response from a Dayton UM18, sound different to a flat response from a PA460 if all bass is omnidirectional and sounds the same?
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post #2 of 41 Old 04-23-2019, 09:32 AM
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There are other factors that contribute to the sound of a particular combination other than flat response, like inductance variation with stroke, or power compression for starters. Comparing two cabinets against each other, if one has a large spike in impedance in the 'meat' of the bass region, the actual power the coil will have to dissipate is less than one with a lower impedance.

Ask your doctor if DIY is right for you. Side effects of DIY may include anxiety, elevated blood pressure, lightheadedness, rapid heartbeat, skeletal muscle flaccidity, euphoria, psychological dependence, insomnia, confusion, blurred vision, implusivity, uncontrolled or repeated movements.
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post #3 of 41 Old 04-23-2019, 06:41 PM
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Moving-mass and BL over the first 5mm's is very important for efficient mid-bass.
Also, the PA-460 likely has more cone-area because the surround is smaller and thinner and lighter.
The coil is smaller and lighter.

That's why the UM is ~88db/w/m and the PA is ~98db/w/m.

Higher mass means that it is slower to start and slower to stop, like a 18-wheeler vs a Lambo.

Sinewaves and sweeps aren't a good representation of impulse response.

I think you would find that if REW used an actual impulse for the IR chart the result would be a lot different than the derived value it currently calculates.

Ignoring test tones. Music and Movies aren't sinewaves nor sweeps. It's somewhere of in-between the two extremes. It's not an impulse but not a sweep either. It's variable-frequency and variable-amplitude, one doesn't know either until it arrives and the cone is asked to reproduce it.

The acceleration and velocity values of the cone during music are variable.
Imagine an Indy 500 race where the goal isn't to cross the line first but rather to start and stop and re-start and re-stop as accurately as possible (best tracking), regardless of the asked magnitude of the acceleration or duration, and the driver not knowing what instruction comes next, or when.
Full blast into Drive and full blast into Breaking and Reverse. The 18-wheeler is at a massive disadvantage.

This is easily demonstrable by waving your arm. Now increase the excursion to 3ft while maintaining the same speed, and then increase the speed 10x while maintaining the same excursion (or NOT reducing the excursion). Nearly impossible for a human. Too much mass and not enough dilithium crystals captain!!!


^ The cone may be asked, multiple times, to switch directions back and forth, before even crossing the resting-position, on any given side, at any given time!
It's being asked to play multiple different frequencies, at multiple different amplitudes, all at once, and without "coloring outside the lines" in real-time (and without knowing what comes next, at any given moment!)

It's amazing that it can achieve only 1% distortion under those conditions, or even 10% THD!!!
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post #4 of 41 Old 04-23-2019, 08:55 PM
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Quote:
Originally Posted by BassThatHz View Post
Moving-mass and BL over the first 5mm's is very important for efficient mid-bass.

Also, the PA-460 likely has more cone-area because the surround is smaller and thinner and lighter.

The coil is smaller and lighter.



That's why the UM is ~88db/w/m and the PA is ~98db/w/m.



Higher mass means that it is slower to start and slower to stop, like a 18-wheeler vs a Lambo.



Sinewaves and sweeps aren't a good representation of impulse response.



I think you would find that if REW used an actual impulse for the IR chart the result would be a lot different than the derived value it currently calculates.



Ignoring test tones. Music and Movies aren't sinewaves nor sweeps. It's somewhere of in-between the two extremes. It's not an impulse but not a sweep either. It's variable-frequency and variable-amplitude, one doesn't know either until it arrives and the cone is asked to reproduce it.



The acceleration and velocity values of the cone during music are variable.

Imagine an Indy 500 race where the goal isn't to cross the line first but rather to start and stop and re-start and re-stop as accurately as possible (best tracking), regardless of the asked magnitude of the acceleration or duration, and the driver not knowing what instruction comes next, or when.

Full blast into Drive and full blast into Breaking and Reverse. The 18-wheeler is at a massive disadvantage.



This is easily demonstrable by waving your arm. Now increase the excursion to 3ft while maintaining the same speed, and then increase the speed 10x while maintaining the same excursion (or NOT reducing the excursion). Nearly impossible for a human. Too much mass and not enough dilithium crystals captain!!!





^ The cone may be asked, multiple times, to switch directions back and forth, before even crossing the resting-position, on any given side, at any given time!

It's being asked to play multiple different frequencies, at multiple different amplitudes, all at once, and without "coloring outside the lines" in real-time (and without knowing what comes next, at any given moment!)



It's amazing that it can achieve only 1% distortion under those conditions, or even 10% THD!!!
Are you of the opinion that it's best to have different subs (drivers) for different purposes within the same setup? Take me for example. I have four Fi Car Audio IB3 18 drivers up front. As you know IBs are accurate with very low distortion, especially for large drivers. They also do ULF very well but they can only take so much power so you need a lot more drivers to reach reference levels. For whatever reason, despite having low distortion and being accurate, they stink at midbass. I don't know what it is but there is something about an IB alignment that lacks midbass. To supplement that problem I have four sealed 12" drivers as NFS directly behind my main seated position. That has helped massively with tactile sensation. Do you think I would benefit from also having some PA-460 drivers up front? My LCR are HTM-12's. I'm thinking a house curve for the LCR + subs would be a good start, then supplement if that isn't enough.

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post #5 of 41 Old 04-24-2019, 06:37 AM
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I think a very confusing element of the midbass discussions is the difference between spl and tactile response.

Very few folks dont have enough midbass spl. look at a graph its there. what is almost always under discussion is the tactile attribute of midbass.

BTH explains very well some of the differences in drivers. the room, the setup and the choice of speakers determines both the spl and the tactile.

i could be wrong but think in 99% of cases a reference to lack of mid bass is actually a lack of midbass tactile feel. its an incredibly important difference to highlight as the solutions to a lack of spl and a lack of tactile are different.
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post #6 of 41 Old 04-24-2019, 06:41 AM
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Quote:
Originally Posted by krholmberg View Post
Are you of the opinion that it's best to have different subs (drivers) for different purposes within the same setup? Take me for example. I have four Fi Car Audio IB3 18 drivers up front. As you know IBs are accurate with very low distortion, especially for large drivers. They also do ULF very well but they can only take so much power so you need a lot more drivers to reach reference levels. For whatever reason, despite having low distortion and being accurate, they stink at midbass. I don't know what it is but there is something about an IB alignment that lacks midbass. To supplement that problem I have four sealed 12" drivers as NFS directly behind my main seated position. That has helped massively with tactile sensation. Do you think I would benefit from also having some PA-460 drivers up front? My LCR are HTM-12's. I'm thinking a house curve for the LCR + subs would be a good start, then supplement if that isn't enough.

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My own experience is that adding the pa460s up front would add some tactile feel because you are increasing the number of cones and surface area used in that frequency range. It would not be more impactful than the NF but would feel more realistic, it would add a farfield tactile element that imo is great.
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post #7 of 41 Old 04-24-2019, 06:45 AM
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Quote:
Originally Posted by gentlemaniac View Post
I understand what chest punch is, I understand what ultra Low Bass is and the difference in how it sounds. But what I don't understand is when people say they are missing mid bass and for example a VBSS will give you more mid bass oomph than a UM18 is that people tend to aim for a flat response, which, as I understand it, only depends on the lower frequencies rolling off, sooner or later and sometimes a room curve is added to detect more bass in the Ultra low region, so I guess what I'm asking is how can a flat response from a Dayton UM18, sound different to a flat response from a PA460 if all bass is omnidirectional and sounds the same?
when eng399 found tbe legacy drivers on buyout, it answered your question for me.
they are high end high inductance drivers designed to have very impactful bass.

i had 2 ultimax 18s in large ported cabinets. i added 2 legacys in moderate size cabs. the add was incredible, very punchy feel that was not there before. i believe its exactly what BTH and michael hurd said.
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post #8 of 41 Old 04-24-2019, 09:00 AM - Thread Starter
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Thanks for all the replies, very informative stuff and good to know
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post #9 of 41 Old 04-24-2019, 11:30 AM
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Quote:
Originally Posted by BassThatHz View Post
Higher mass means that it is slower to start and slower to stop, like a 18-wheeler vs a Lambo.

Incorrect, and debunked in texts and by audio engineers many times over the years.

The apt comparison is a 100 HP motorcycle vs. a 1000 HP Lambo.

Other things being equal, especially Q, the only difference is efficiency; a heavier cone with a suitable motor will accelerate just as fast as a lighter cone, it will just take more power.

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post #10 of 41 Old 04-24-2019, 01:17 PM
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I like the car analogies.

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post #11 of 41 Old 04-24-2019, 05:11 PM
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Quote:
Originally Posted by noah katz View Post
Incorrect, and debunked in texts and by audio engineers many times over the years.



The apt comparison is a 100 HP motorcycle vs. a 1000 HP Lambo.



Other things being equal, especially Q, the only difference is efficiency; a heavier cone with a suitable motor will accelerate just as fast as a lighter cone, it will just take more power.
This.

To create a specific frequency the cone has to move at a specific speed. Therefore the only way to create said frequency is to move at the required rate. The driver either can or can't do that.

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post #12 of 41 Old 04-24-2019, 06:04 PM
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Originally Posted by frenchfries View Post
To create a specific frequency the cone has to move at a specific speed. Therefore the only way to create said frequency is to move at the required rate. The driver either can or can't do that.
That's not 100% correct.

To have a specific frequency the cone has to cycle at that rate.
Given an amount of excursion, THAT... will determine the cone-speed required.

Even more precisely...
For a given cone-mass and electromagnetic field strength and suspension stiffness and box volume and tuning (and a bunch of other T/S values and box-model formulas), THAT will determine the amount of watts to reach a particular excursion... and thus cone-speed, regardless of the particular frequency being targeted.

At least... I think I said that all correctly No?
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post #13 of 41 Old 04-24-2019, 06:15 PM
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Originally Posted by krholmberg View Post
As you know IBs are accurate with very low distortion, they stink at midbass.
That can be fixed with EQ (up to a point), as long as there is head room in the amp and coil for power-handling (heat) and excursion head room.

BUT...
If you do that, you will no longer have a flat FR. (But it will be louder mid-bass from the IB. )

That is because of the lack of box rise, and the reduced power-handling to avoid bottoming out on low frequencies.

Additionally, due to the power being spread across more/deeper frequencies at least... vs a HPF'ed ported or horned box, that is! The same cannot be said against sealed because sealed boxes are often not HPF'ed (generally).
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post #14 of 41 Old 04-24-2019, 06:43 PM
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Originally Posted by krholmberg View Post
Are you of the opinion that it's best to have different subs (drivers) for different purposes within the same setup?
Yes.
As you approach 0hz, for a given cone-area, it requires increasing amounts of excursion.
Excursion is generally not the wheel house of PA drivers.

For mid-bass it's all about efficiency, power handling, and lots of motors and coils to keep things cool when the excursion is near-zero, and cone-area.

Throwing more drivers at the problem is always better than throwing more watts at the problem, that's because doubling cone-area nets 3db and no additional heat or distortion, doubling power is also 3db but causes nothing but heat and distortion and bottoming and mechanical noise.

Also, doubling the cones can help reduce power requirements for lower SPL's, and thus... even less distortion; orders of magnitude better in fact!

Quote:
Originally Posted by RoboAVS View Post
i could be wrong but think in 99% of cases a reference to lack of mid bass is actually a lack of midbass tactile feel. its an incredibly important difference to highlight as the solutions to a lack of spl and a lack of tactile are different.
Yes SPL and tactility are different things.

There are two causes of tactility: SPL and vibs, and possibly wind if your body is near the port, and hyper nearfield it could also be excessive particle-displacement.

For SPL-tactility that requires a fairly high amount, generally north of 100db, or even north of 125db (between 40-300hz AT THE SEATS!)
Basically you are vibrating your bones and body-fat via SPL.

Vibs comes from mechanical coupling with the moving-mass of the box/cone via the floor, plus any additional resonances induced in objects in your room (windows, dishes, seating, etc)

If you have a dual-opposed alignment, then there will be no mechanical coupling as the Newtonian forces are cancelled by the opposing forces. Leaving only rigid-body/structural resonances for vibs/tactility via spl ONLY.
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post #15 of 41 Old 04-24-2019, 07:15 PM
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Not sure mechanical coupling of the enclosure to floor is the only means of generating floor motion. Its a large diaphragm after all and perhaps there is enough force generated by the boundary pressure changes to induce some motion (edit - just reread your post... perhaps that's what you meant in that last sentence?).

Lots of people here believe particle velocity is responsible for a large part of the perceived differences in nearfield and farfield sub placement. Maybe there is something to that.

All that being said, saying IB sucks at midbass is missing the big picture. IB's are almost always a far field installation, drivers are typically chosen specifically for their large excursion and ability to produce the single digits, and they are often crossed at 80Hz or lower. If someone didn't care about the ULF, chances are they wouldn't bother with an IB (not that there aren't other benefits).

But if one was so inclined, you could surely place a horde of PA460 or any other driver of choosing in a nearfield IB, cross at 120Hz, and pound your chest as well as any other solution.
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post #16 of 41 Old 04-24-2019, 07:27 PM
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Once you get driver specifically for freq ranges, only then will you get the midbass AND ULF.
Big subs for ULF, pro style/horn etc for 40-50hz and up, thats the way to do it. Once I did that, I feel my sub chase ended.
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Originally Posted by N8DOGG View Post
Once you get driver specifically for freq ranges, only then will you get the midbass AND ULF.

Big subs for ULF, pro style/horn etc for 40-50hz and up, thats the way to do it. Once I did that, I feel my sub chase ended.
Going back to my setup, I have 4 Fi Car Audio IB3 18" drivers in an IB alignment. I also have 4 Infinity 1262 subs for nearfield duty. Lastly, my LCR are DIYSG HTM-12's (which were designed with midbass in mind). The IBs obviously do ULF well. The 1262's really helped midbass tactility. I'm thinking a nice house curve between the LCR and IB subs should fill out try front of the theater nicely. Unfortunately my receiver doesn't allow for a house curve but I'm waiting for the RMC-1 to become reliable and have Dirac enabled (hopefully that's not a pipe dream).

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post #18 of 41 Old 04-24-2019, 08:47 PM
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Quote:
Originally Posted by Bigus View Post
Not sure mechanical coupling of the enclosure to floor is the only means of generating floor motion. Its a large diaphragm after all and perhaps there is enough force generated by the boundary pressure changes to induce some motion

Definitely.

A few years back someone here was bedeviled by a huge 15 Hz suckout.

Turned out his floor was acting as a diaphragm absorber.
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post #19 of 41 Old 04-25-2019, 06:22 PM
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Quote:
Originally Posted by Bigus View Post
Not sure mechanical coupling of the enclosure to floor is the only means of generating floor motion. Its a large diaphragm after all and perhaps there is enough force generated by the boundary pressure changes to induce some motion (edit - just reread your post... perhaps that's what you meant in that last sentence?).
It was meant to be inclusive of that yes. The other case I suppose would be subwoofers hanging off of springs or cables or 8inches worth of isolation pads.

Obviously if the floor is concrete at ground-level there won't be much of that force either, because: too much inertia and too low of a resonant frequency.

Quote:
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Lots of people here believe particle velocity is responsible for a large part of the perceived differences in nearfield and farfield sub placement. Maybe there is something to that.
I don't fully understand the relationship between pressure and particle velocity.
Pressure I'd like to think I have a good grasp on, it is the localized density of the air particles, now obviously those particles have to move for the sound wave to flow through space but my understanding was that that was always at a constant velocity based on the temperature and viscosity of the substance (air, in this case.)

I believe there might be two aspects to sound. That localized density and also the surface-area of the wavefront that is being displaced. I think of it like this: imagine a single 8" sub vs 24 24's, both are playing at say 90db. The 24 24's are going to be shifting a MUCH "larger area" of air particles even though the SPL and displacement is equal in both cases. The sound is more of a Z-axis planar-wave than a spherically expanding point-source.
Larger systems have that "something" about them, and IMO that is exactly it (or a small part of it at-least).
It's not displacement and it's not SPL. It's more like wavefront-area... if that makes any sense?

Sound can travel through solid objects like drywall, or metal. The particle-velocity will be near-zero in that case, even though the sound-pressure might be super-duper HIGH;
the energy is coupled through the structure rigidly at very high propagation velocity but that is completely unrelated to the particle-velocity or the pressure-magnitude.
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Regarding ULF and Mid bass

Quote:
Originally Posted by BassThatHz View Post

I believe there might be two aspects to sound. That localized density and also the surface-area of the wavefront that is being displaced. I think of it like this: imagine a single 8" sub vs 24 24's, both are playing at say 90db. The 24 24's are going to be shifting a MUCH "larger area" of air particles even though the SPL and displacement is equal in both cases. The sound is more of a Z-axis planar-wave than a spherically expanding point-source.

Larger systems have that "something" about them, and IMO that is exactly it (or a small part of it at-least).

It's not displacement and it's not SPL. It's more like wavefront-area... if that makes any sense?

Sounds like what you’re explaining is also why a double bass array smooths in-room response. Here’s a good graphic of what I believe you were explaining:

Source: https://en.m.wikipedia.org/wiki/Double_bass_array
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post #21 of 41 Old 04-25-2019, 07:44 PM
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There is a localized particle velocity that is coupled to compression and rarefaction in propogation of a pressure wavefront.

There can also be mass flow particle velocity with no or little or even steady state pressure change that therefore has a very low associated sound volume. Think airflow from a fan, or air motion at the edge of a subwoofer cone/frame in frespace (subject to dipole cancellation). SPL associated with both of these is low, but there is tangible particle flow.

Near a large subwoofer (or port) perhaps there is mass particle flow greater than necessary to support the SPL generated. A localized phenomenon that dissipates quickly as wavefront propogates. Maybe. I believe that is one of the proposed mechanism of nearfield tactility.
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post #22 of 41 Old 04-25-2019, 08:20 PM
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Quote:
Originally Posted by Bigus View Post
There is a localized particle velocity that is coupled to compression and rarefaction in propogation of a pressure wavefront.



There can also be mass flow particle velocity with no or little or even steady state pressure change that therefore has a very low associated sound volume. Think airflow from a fan, or air motion at the edge of a subwoofer cone/frame in frespace (subject to dipole cancellation). SPL associated with both of these is low, but there is tangible particle flow.



Near a large subwoofer (or port) perhaps there is mass particle flow greater than necessary to support the SPL generated. A localized phenomenon that dissipates quickly as wavefront propogates. Maybe. I believe that is one of the proposed mechanism of nearfield tactility.
What drivers do you like?

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post #23 of 41 Old 04-25-2019, 08:36 PM
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Quote:
Originally Posted by krholmberg View Post
What drivers do you like?

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For what application? There is no best driver, just better and perhaps best drivers for a price point and specific use.

Midbass only? Or midbass and sub? Budget? Size constraints? Location? Listening habits?
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post #24 of 41 Old 04-25-2019, 09:51 PM
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Quote:
Originally Posted by BassThatHz View Post
Pressure I'd like to think I have a good grasp on, it is the localized density of the air particles, now obviously those particles have to move for the sound wave to flow through space but my understanding was that that was always at a constant velocity based on the temperature and viscosity of the substance (air, in this case.)

The wave travels at constant velocity; the particles (molecules) move back and forth.

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post #25 of 41 Old 04-26-2019, 03:07 AM
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I think what is often confused with particle acceleration is people assume the driver is throwing particles all over the room. Where it is actually how fast the particles compress and decompress. This also explains the benefits of being sea level.


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post #26 of 41 Old 04-26-2019, 05:10 AM
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Quote:
Originally Posted by N8DOGG View Post
Once you get driver specifically for freq ranges, only then will you get the midbass AND ULF.
Big subs for ULF, pro style/horn etc for 40-50hz and up, thats the way to do it. Once I did that, I feel my sub chase ended.
Im wanting to do similar using 4 subs for 10-40 and 4 MBM for 50-100 or higher. What type of crossover slope is recommended? Any other setup suggestions/tips?
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post #27 of 41 Old 04-26-2019, 08:28 AM
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For what application? There is no best driver, just better and perhaps best drivers for a price point and specific use.



Midbass only? Or midbass and sub? Budget? Size constraints? Location? Listening habits?
Please see post 17 for my setup. This was more of an open ended question. The post I quoted has a lot of theoretical discussion that is fascinating but esoteric. I was trying to bring a practical recommendation out of your post. What I'm most interested in is a midbass woofer that can go between ported LCRs and sealed ULF subs (in my case the LCR are DIYSG HTM-12's, the NFS are 4 x Infinity 1262 and the ULF subs are 4 x Fi Car Audio IB3 18's in an IB alignment). The woofers would augment the midbass in an open loft that has essentially no room gain or pressurization. Since my LCR have the potential to put out decent midbass, the woofers I might be potentially be interested in could either be crossed over between the LCR and IB subs or run parallel to the LCR in the mid-range frequencies. Use is mostly movies, TV and not serious music listening.

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post #28 of 41 Old 04-26-2019, 09:16 AM
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Integrating in a narrow band between/overlapping ported mains and sealed subs is going to be challenging.

My first kneejerk is to plug the HTM12 ports, measure everything you have, and then go from there. The 12's nearfield should be more than enough for most everyone given 4x18 IB and very capable HTM 12 mains. Can't help but wonder if there is a current integration issue.

If you have to add something (and at this point I'm assuming you'd want a nice house bump in response from 50-150Hz) I'd look for a couple or few prosound 18‘s or 21's that are comfortable in sealed enclosures. You'd get more output in ported of course, but further amplify integration headaches.

Budget?
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post #29 of 41 Old 04-26-2019, 05:30 PM
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post #30 of 41 Old 04-26-2019, 07:18 PM
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Quote:
Originally Posted by Bigus View Post
Integrating in a narrow band between/overlapping ported mains and sealed subs is going to be challenging.



My first kneejerk is to plug the HTM12 ports, measure everything you have, and then go from there. The 12's nearfield should be more than enough for most everyone given 4x18 IB and very capable HTM 12 mains. Can't help but wonder if there is a current integration issue.



If you have to add something (and at this point I'm assuming you'd want a nice house bump in response from 50-150Hz) I'd look for a couple or few prosound 18‘s or 21's that are comfortable in sealed enclosures. You'd get more output in ported of course, but further amplify integration headaches.



Budget?
I think the problem is twofold... 1. integration (as you mentioned) and, 2. an open concept house that allows no room gain or pressurization. The former will be addressed when I get a new pre-pro that is highly customizable. If that doesn't work, then I'll have to address the latter point by adding more drivers.

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