the HouseWrecker. 11hz Twin CVX-15 Tapped Horn - Page 5 - AVS Forum
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post #121 of 420 Old 04-20-2011, 07:25 AM
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Originally Posted by yelnatsch517 View Post

So you're saying in a dream setup one would have a horn for the bass and a rotary sub for the ULF? How large of a room would be required for a horn to be clean to 5Hz? Also, what about the time delay of such a horn? The acoustic pressure wave would take a noticeable time to propagate through the horn and out into the room, would it not? Also, the larger the horn, the more distortion gets picked up before exiting the mouth, does it not?

The dream setup has that rotary sub and then multiple high end band pass designs placed around the room. That will create the more then enough output but more importantly the best in room response.

Horns are great for output priorities but hard to use when someone actually wants the best in room bass response

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post #122 of 420 Old 04-20-2011, 09:03 AM
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Originally Posted by penngray View Post

The dream setup has that rotary sub and then multiple high end band pass designs placed around the room. That will create the more then enough output but more importantly the best in room response.

Horns are great for output priorities but hard to use when someone actually wants the best in room bass response

With modern drivers and amps and the size of rooms we're talking about for home theater it seems there's little rational reason to use a horn. However, having said that, I'd love to build some full room height hyperbolic corner horns on each side of a stage some day. Use the natural corners of the room and then the horn body itself would almost look like a pillar. Like I said, there's no real reason I can think of to do that, but it would be cool (in a HT geek sense) since it would be near impossible to tell where the bass was coming from.
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post #123 of 420 Old 04-20-2011, 09:56 AM
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Originally Posted by scientest View Post

With modern drivers and amps and the size of rooms we're talking about for home theater it seems there's little rational reason to use a horn.

Of course there is: cost / bang for the buck.
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post #124 of 420 Old 04-20-2011, 09:58 AM
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Originally Posted by Brad Horstkotte View Post

Of course there is: cost / bang for the buck.

Well, if you want flat response across the room, I don't see how a horn is going to do it at any better cost than several other solutions?
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post #125 of 420 Old 04-20-2011, 01:43 PM - Thread Starter
 
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My two cents on a couple things….

Here’s a simplistic explanation of what a horn does: A correctly designed horn does two things. First it focuses the sound into a tighter beam. Second the compression chamber better matches the acoustic impedance of the diaphragm to the air around it (down to the cutoff frequency of the horn – where it begins to “unload”). BOTH things increase the load on the drivers diaphragm (thus requiring stronger motors to move the diaphragm a given distance – or more electrical energy to do the same) – and increase the SPL inside of the coverage pattern of the device.

To the first, a horn acts as a kind of a wave guide and does the same thing to the sound that a flashlight’s reflector does - it directs and focuses the sound coming from the transducer. Let’s say you have a light – that measures 10 foot-lambert’s in open air at 1 meter, with the light radiating in every direction spherically 360 dgs around it (equivalent to an Anechoic environment). Now take that same light, and set it down on a perfect mirror (half space). At 1 meter distance, you’ll read double the brightness or 200 foot lamberts (double free space). Add another wall and set the light at the juncture of the two walls - (quarter space) you double its output again (four times free space ). 400 foot lamberts. Add another wall to create a corner with a point and put the light down at the apex of that corner – (8 times the intensity of free space) 800 foot lamberts. And so on..

The tighter you focus that light the brighter that single light source is inside of its coverage pattern, but less area the light covers and the higher the intensity is in front of the beam. Similar to using a Mag Light and spreading the beam super wide vs. its tightest focal point. The tighter the acoustic beam – the larger the increase in SPL measured inside of its pattern.

The next thing a horn does is operate as an acoustic impedance transformer. Ordinarily – the radiation resistance of the driver is insignificant relative to the air it is pushing around (the air – a gaseous medium with quasi viscous properties) it is difficult for a little tiny cone to “grab” that air and control very well. Think of a Fan, or the impeller of a boat, or propeller to an airplane. As the fan blades spin, turbulent air peels off the outside edges and the blades efficacy is compromised. Same with an impeller or propeller. If you wrap a duct around those blades (any group of them) – the air or water cannot so easily shear and tumble off the edges – the now focused fluid or gas moves at a much higher velocity out the back side of the blades – while they turn at the same speed, though the load on the driving motor has increased. Decrease the size of the orifice the fluid/gas is exiting through (compress it), and again you increase the velocity of that medium on exit (and load on the drive unit)..

The duct has increased the mechanical impedance of the fan/impeller/propeller. To spin the same speed – because the device is moving more fluid / gas per sweep – the ‘Load’ on the driving motor is significantly increased. Decreasing the size of the ducts exhaust – also increases the impedance / load on the driving device and velocity of the exiting medium.

This is the same type of thing the compression chamber does in a Horn. It increases the acoustic impedance of the driving element – bringing it to a much closer match to the air around it. This increased “grip” on the air – improves the acoustic coupling of the diaphragm – and increase the SPL it generates for a given movement. While at the same time – increasing the force required to move the diaphragm a given distance.

This was most easily demonstrated to me one day – when I grabbed the huge exponential 400hz midrange horn at Klipsch and tried talking through it. My voice was Massively increased in SPL – but the force required to make said voice was incredible. It was physically hard for me to make a sound through the horn. Till that point – I couldn’t fully comprehend exactly what it was that a horn does.

Two reasons bass horns can sound better than point source drivers:

1. The Spl increase brought about by the above lead to a significant reduction in distortion at a given SPL, provided the driving element has the strength to handle the increased load. The reason is simple – motors are one of the two components that generate distortion in a transducer – to quote Paul W. Klipsh’s words to me directly “If the cone Moves – the speaker Distorts, period. Increase its movement – increase its distortion. Anything you can do to reduce its travel for a given SPL will yield an immediate reduction in distortion components.”.

2. Dynamic Range. This is a distortion (dynamic compression) component RARELY talked about by the audio industry to the end consumer – and to me it is arguably the most important distortion component to address. Ever go to a fantastic concert – with exceptional sound – and drive home wishing you could have the dynamics of that system in your living room? Ever go to a HiFi store and hear a system that is purportedly ultra flat in f/r – but come away thinking the system sounded dull/lifeless/un-impressive? There is a Reason for that.

Something I have found in my own research into LF that may be almost counter intuitive to a consumer – but is true. The human ear responds more directly to increases in dynamic range – than to high Q deviations in frequency response. High dynamics will lend more of a sense of “realism” to sounds being reproduced than an uber flat on axis f/r, provided the object with the rough f/r follows the general trend of the flatter speaker.

The human ear is relatively insensitive to minor high Q deviations in amplitude – especially troughs, it roughly correlates to f/r smoothing of between 1/6’th and 1/3d octave (this is part of the reason most mfrs published material shows 1/3 oct smoothing).. If the highly dynamic systems 1/3 smoothed response is akin to that uber flat speakers response – a 20dB headroom system will sound tremendously more realistic than that Uber Flat 5dB or 10dB system. ( an XXdB headroom means the enumerated SPL capability broad band above the reference listening level. IOW if I choose 100dB for my “reference” level – my system will require 120dB broadband capability to be called a “20dB system.)

Regarding the “time delay” involved to propagate the signal from a Bass horn.
The speed of sound is 340m/s so to change it into yards the conversion rate of a meter to a yard is 1.0936133 so you would get 371.829 yrds/s and then you would use the conversion 3 ft=1 yard.
So sound travels 1115.486ft/s
So then you would use a basic physics equation of V=X/T
V=Velocity
X=Distance
T=Time
You're trying to find time so rearrange the equation T=X/V
T=3ft/1115.486ft/s
T=2.69 milliseconds

The length of this horn is approximately 6.096 meters – so a sound exiting the horn is delayed approximately 16.3982milliseconds. This does not account for the phase lead generated by the horns increased acoustic impedance match to air relative to a free air point source transducer at the corner frequency. In the 2 decades I’ve been studying and researching acoustics – including literally hundreds of AB and ABX test of various things, I’ve come to the conclusion – that regarding low frequency time delay – the human ear is as insensitive to errors in time as it is to the actual frequency.

Remember that at 4khz – an un damaged ear can hear 1dB spl – or literally molecules oscilating back and forth the distance of that molecules electron orbit (!) IOW colliding into each other. Correspondingly at those frequencies it is also the most sensitive to timing errors – between 1 and 4khz, the human ear can detect time errors as low as 2ms (1khz) and 1.4milliseconds at 4khz. 500hz the ear can detect 3.2ms deviations. At 20hz, it takes the average human ear over 70dB spl to cross the threshold of hearing. And at 16, about 100dB spl. Your ears are increasingly less sensitive as you drop (and increase) in frequency.

I subscribe to the theory my friend and a figure in our industry John Murphy does with regards to timing error's perceptibility at LF. Extrapolating Blauert and Law’s threshold of detection for “hearing” timing error’s to cycles at a given frequency – (their data covers 500hz/1khz/2khz/4khz and 8khz) it looks like we become sensitive to changes in timing of around 1 full cycle under the most controlled listening environment and using the most challenging material (clicks and pops).

Here is John’s opinion on the audibility of delay in the bass range. “My" current opinion would go something like this: "One cycle or so of delay in the bass range is probably just audible under controlled listening conditions (headphones) and with the most challenging program material (clicks and pops). Under less well controlled listening conditions and with less difficult program material the audibility thresholds are somewhat higher."

So – let’s look at 10hz, 20hz, and 40hz (the range my sub will be used under.. even though Lil-Mike has pulled out the almost impossible and designed an almost 3 octave tapped bass horn in theHouseWrecker!) and see how long one cycle is.

1 period at 10hz is 113 feet. (!!!) Expressed in milliseconds – that would be analogous to 101 milliseconds (!!!)

1 period at 20hz is 56.5 feet. (!!) Expressed in milliseconds – that would be analogous to 50.6 milliseconds (!!)

1 period at 40hz is 28.25 feet. (!) Expressed in milliseconds – that would be analogous to 25.3 milliseconds (!)

Keep in mind – these models use an infinitely ridged wall for the horn – the actual deviations will be smoothed. My experience also tells me (from ABX testing) that Most Consumers under normal listening conditions cannot tell there is a significant timing error with as much as 3 times those numbers below ~~ 60/80hz. So.. looking at theHouseWrecker’s model we have……

101ms delay at 11hz. (Just under what the potential barely detectable threshold of a trained ear under controlled conditions and with program material specifically designed to highlight timing errors.) My experience is that the human ear can’t detect even 4x that much delay at this frequency – it is very insensitive to this deep LF.

22ms delay at 20hz. Less than half of the best possible threshold.

23ms at 40. Right under the best likely potential threshold for detection.

I can use double those numbers and be quite happy.

Regarding “distortion increasing as the line length increases":100% False. Increase the compression to a degree the velocity is so high at the reproduced levels in the throat – distortion will increase. Use too small a mouth, or folded turns with tight restrictions in the high velocity area (end of line), distortion will increase. Etc..

The designs Lil-Mike and I work up have a TON of energy put into them to reduce the acoustic reactance as much as possible, and match the load to the transducers being used. (for instance theHouseWrecker has significantly less acoustic reactance than the DTS10. It presents a very easy load to the driver face) – and ensure adequate expansion and mouth size relative to the driving element and expected F/R and SPL to be reproduced.
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post #126 of 420 Old 04-20-2011, 01:58 PM - Thread Starter
 
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If you guys don't mind - I would like to keep the majority of the conversation under this thread specific to theHouseWrecker. Lets try not to follow "the best/ideal/this or that", "what is and isn't practical for XYZ's room", "well IB's or 'Name your thing' are better", "horns are or aren't practical" etc.

We would like the final thread is easily digestible to those looking specifically for information regarding this project. In my application - this particular subwoofer is a fantastic addition and aside from construction - is an EXTREMELY practical solution for a ULF.

It was designed specifically for me to meet my needs, and for my space constraints and listening environment. Once finished this room will have 8 sealed 10" subs each powered by ~~ 500 watts across the front stage, 2 rear 12" subs with ~~ 1kw per, all covering bass.

theHouseWrecker will be called on as a true subwoofer covering roughly 11hz through ~~ 40-80 - depending on final measurements and in room tweaking.
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post #127 of 420 Old 04-20-2011, 02:13 PM
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Quote:


The designs Lil-Mike and I work up have a TON of energy put into them to reduce the acoustic impedance as much as possible, and match the load to the transducers being used. (for instance theHouseWrecker has 1/3 the acoustic impedance of the DTS10. It presents a very easy load to the driver face) – and ensure adequate expansion and mouth size relative to the driving element and expected F/R and SPL to be reproduced.

That is pretty impressive.

I still would love to have plans for my own build but I know what you posted already.

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post #128 of 420 Old 04-20-2011, 02:21 PM - Thread Starter
 
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Originally Posted by scientest View Post

Well, if you want flat response across the room, I don't see how a horn is going to do it at any better cost than several other solutions?

scientest - this particular location, and throat exit were designed specific to my needs. After exhaustive measurement – the opening location proved to be far and away the FLATTEST measured position in room for a sub - and said throat exit only takes up a footprint of 16" x 36" in room – and is complimented by a brace of additional woofers for regular bass. .

Cost to me to build = some glue, some screws, a few sheets of Auraco, some 2x4's, a lot of elbow grease, two 15" drivers well suited to this horn and time. Less than the rest of the woofers in the system cost.

For less than $500 - I have a ULF in the making capable of LF output never heard of from a pair of 15" woofers in traditional enclosures at these frequencies with this little amplification.
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post #129 of 420 Old 04-20-2011, 02:39 PM
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Originally Posted by dB-Kicker View Post

scientest - this particular location, throat exit were designed specific to my needs. After exhaustive measurement - the opening location proved to be far and away the FLATTEST measured position in room for a sub -The throat exit takes up less than a footprint at 16" x 36" in room - and is complimented by a brace of additional woofers for regular bass. .

I guess that is the key here, you're using this only for a pretty narrow range of frequencies and it's not the only sub in the room. I'm sure you've mentioned it, but what's the highest frequency you're going to reproduce with this? If you could manage to keep the shortest 1/2 wavelength under the longest dimension of the room then it really wouldn't matter where you positioned the thing since you could never have any standing waves.... So assuming that's not the case, when you way "FLATTEST", is that for all listening positions or ...???
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post #130 of 420 Old 04-20-2011, 02:52 PM
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Quote:
Originally Posted by penngray View Post

That is pretty impressive.

I still would love to have plans for my own build but I know what you posted already.

The throat, mouth, and transition have all been updated. I'll post up what I have later this evening. It is now a set of sketchup files, but at least now everything is a component and all of the assemblies have been exploded so that it is possible for dB to pull dimensions.

This is pretty much specific to dB's room and setup. He had the foresight to measure the room and make sure the room's transfer function was going to work with the cabinet rather than against it.
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post #131 of 420 Old 04-20-2011, 03:14 PM - Thread Starter
 
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Originally Posted by scientest View Post

So assuming that's not the case, when you way "FLATTEST", is that for all listening positions or ...???

Yes. They are all within 1dB of eachother from 10hz through 40. Upper cuttoff will be determined once it is built, measured, and fine tuned with the other woofers in room.
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post #132 of 420 Old 04-20-2011, 06:43 PM
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Originally Posted by dB-Kicker View Post


The designs Lil-Mike and I work up have a TON of energy put into them to reduce the acoustic impedance as much as possible, and match the load to the transducers being used. (for instance theHouseWrecker has 1/3 the acoustic impedance of the DTS10. It presents a very easy load to the driver face)....

Everything I've read about horns says that *maximizing* acoustic impedance is the goal, as that's what allows mechanical energy of the cone to be converted to acoustic energy.

Also I'm afraid your analogy to airflow is incorrect, as that's fluid mechanics, not waves.

Noah
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post #133 of 420 Old 04-20-2011, 06:48 PM
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Quote:
Originally Posted by noah katz View Post

Everything I've read about horns says that *maximizing* acoustic impedance is the goal, as that's what allows mechanical energy of the cone to be converted to acoustic energy.

Acoustic reactance is what I work to minimize. Mis-matched acoustic reactance is what makes the bad things happen.
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post #134 of 420 Old 04-20-2011, 07:10 PM
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ah, so maximize acoustic resistance and minimize mass and spring reactance?

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post #135 of 420 Old 04-20-2011, 07:17 PM - Thread Starter
 
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Quote:
Originally Posted by noah katz View Post

Everything I've read about horns says that *maximizing* acoustic impedance is the goal, as that's what allows mechanical energy of the cone to be converted to acoustic energy.

Also I'm afraid your analogy to airflow is incorrect, as that's fluid mechanics, not waves.

Noah - end of a long day of catching up after having stomach flu for 3 days straight and almost no sleep. You are correct. Edited my post to reflect..

The analogy is a comparison of something with a similar effect to demonstrate the notion of increased acoustic impedance. Not a direct comparison of fluid dynamics to sound waves. I'm not that dense

From Webster "a : resemblance in some particulars between things otherwise unlike : similarity b : comparison based on such resemblance"
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post #136 of 420 Old 04-20-2011, 07:23 PM - Thread Starter
 
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Quote:
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ah, so maximize acoustic resistance and minimize mass and spring reactance?

Yes.
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post #137 of 420 Old 04-29-2011, 06:42 PM - Thread Starter
 
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post #138 of 420 Old 04-30-2011, 06:41 AM
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Originally Posted by dB-Kicker View Post

My two cents on a couple things.

Fantastic post! The physicist in me loved it!!

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post #139 of 420 Old 06-16-2011, 03:23 AM
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Any updates on this thread?
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post #140 of 420 Old 08-14-2011, 11:16 PM
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What the hell is going on here? I know there have been many things in personal lives that have caused some delays, but you don't just start a thread and get us all excited then leave us high and dry!

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post #141 of 420 Old 08-17-2011, 03:56 PM - Thread Starter
 
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Well......

OK. Um - No Progress. But.... In the interim - I was asked to do the acoustic design for system which will be used in the truck leading the 10'th anniversary 9-11 Tribute memorial parade. The truck was commissioned by the tribute / memorial fund, and our GVT to Mickey Harris - a world renowned airbrush artist. John Meyers a good friend I work with who's done installs on about every auto/truck/pimp/steel my ride show was asked to do the install.. I asked our very own Lil-Mike if he'd be interested in collaborating - and he whole hardheartedly agreed. Poor guy jumped through some SERIOUS hoops for me / us.

Long and short of it - he designed an INSANE Quad 15 TH system flat to 25hz, that generated 135dB SPL 1m with only 4 15" drivers at 1kw per driver!!!!!!! Upon firing it up to demo at work - it was named The most Violent sub-woofer anyone there had ever heard outside of a competition SPL vehicle. Kudos MIKE!!!! It's being fired up in the truck tonight for the first time.

After hearing it while I was validating it - I thought to myself - I might not mind giving up some extension, for this kind of INSANE SPL and do twin subs which I can fire through wall joists - instead of having to rip half the wall out, and build headers / footers around the manifold.

Sooooo...... we're working on another potential design.... Just haven't made my mind up yet.... I'll try to attach pix of the 9-11 tribute sub......
LL
LL
LL
LL
LL
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post #142 of 420 Old 08-17-2011, 04:00 PM - Thread Starter
 
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More pix..

Listening to over 130dB in room - with less than 500 watts a driver modulating our voices, and "Pressurizing" our chests - was an EXPERIENCE. It sounded like an SPL vehicle - but this was in our HUGE listening room...

FYI I am FOREVER Sold on TH's, Especially Mikes!! With his permission we will post the models if ya'll are interested.

The sub was designed to fit in a standard full size truck bed between the wheel wells... And use about ALL that space
LL
LL
LL
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post #143 of 420 Old 08-17-2011, 05:08 PM
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Very cool stuff.
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post #144 of 420 Old 08-17-2011, 05:16 PM
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Quote:
Originally Posted by dB-Kicker View Post

Well......

OK. Um - No Progress. But.... In the interim - I was asked to do the acoustic design for system which will be used in the truck leading the 10'th anniversary 9-11 Tribute memorial parade. The truck was commissioned by the tribute / memorial fund, and our GVT to Mickey Harris - a world renowned airbrush artist. John Meyers a good friend I work with who's done installs on about every auto/truck/pimp/steel my ride show was asked to do the install.. I asked our very own Lil-Mike if he'd be interested in collaborating - and he whole hardheartedly agreed. Poor guy jumped through some SERIOUS hoops for me / us.

Long and short of it - he designed an INSANE Quad 15 TH system flat to 25hz, that generated 135dB SPL 1m with only 4 15" drivers at 1kw per driver!!!!!!! Upon firing it up to demo at work - it was named The most Violent sub-woofer anyone there had ever heard outside of a competition SPL vehicle. Kudos MIKE!!!! It's being fired up in the truck tonight for the first time.

After hearing it while I was validating it - I thought to myself - I might not mind giving up some extension, for this kind of INSANE SPL and do twin subs which I can fire through wall joists - instead of having to rip half the wall out, and build headers / footers around the manifold.

Sooooo...... we're working on another potential design.... Just haven't made my mind up yet.... I'll try to attach pix of the 9-11 tribute sub......

At first I was excited to see this thread replied to, then extatic that you posted, then I read what 'lil did... I am extremely bummed, but just for a second. That was why i was asking "How would some wicked 25Hz tapped horns stack up to 6 soloX 18's ported tuned to 25Hz?"

But hey it's for a great cause so I'll get over it. Not saying you jacked my idea, I know better, jus sayin now I need to find a new daydream brainstorm. That was exactly what I have been working at and around for a couple months now. Even trying to learn Hornresp to see why the soloX 18 isn't as good a choice as the 15's.

Anyway, lookin forward to pics, vids, more results if you choose to share them.
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post #145 of 420 Old 08-17-2011, 05:21 PM
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Damn.....

When are you gonna go 'pro', Mike?

That is one serious looking creation. Is that MDF? Will it hold up to sustained 135dB???? Or will it be the first tapped horn to 'tap itself out'?

JSS
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post #146 of 420 Old 08-17-2011, 05:27 PM - Thread Starter
 
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Mike is a pro!

Yes the MDF will hold up just fine.

Won't be 'Sustained". Here's the FB blurb....

"215 Acoustic Watt 30hz tapped Horn Subwoofer which will be installed in the truck commissioned by the US government to Mickey Harris one of the world’s most renowned Airbrush artists. The truck will lead the 9-11 10'th anniversary parade with the President - then be permanently located on sight at Ground Zero in a memorial museum. Sub designers, dB in collaboration with TH and layout wizard Mighty Mike P., builders John M, dB, and Gene C… "

The truck will also be used for various government sanctioned promotional events.
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post #147 of 420 Old 08-17-2011, 05:30 PM
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One thing that I wondered when I looked at the pics is whether that is enough bracing. It looks very light to me. Wonder how it will hold up at full crank? Not trying to be a downer but my last "high pressure" tapped horn build has me thinking that we really might need to get a little beefier on these high output horns, since the output is often 6-10 db higher than a ported sub with correspondingly higher internal pressures. Either way. Very cool stuff for a good cause.
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post #148 of 420 Old 08-17-2011, 05:34 PM - Thread Starter
 
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It is more than enough bracing. The panels are dead at full chat. You forget - we create 170dB SPL competition vehicles....... I wasn't about to let this thing be sub par...
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post #149 of 420 Old 08-17-2011, 05:35 PM
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Quote:
Originally Posted by maxmercy View Post

Damn.....

When are you gonna go 'pro', Mike?

That is one serious looking creation. Is that MDF? Will it hold up to sustained 135dB???? Or will it be the first tapped horn to 'tap itself out'?

JSS

Pro??? Soon as I can find a way to make more at this than at my day job...

As far as holding up? The MDF will fail before the PL. It is a large box, pressures are not that high. As far as self-destructing tapped horns??? Todd and I have already taken care of that. There's a real reason I won't use 1/2" material with a 15" driver........
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post #150 of 420 Old 08-17-2011, 05:43 PM
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Quote:
Originally Posted by kryptonitewhite View Post

At first I was excited to see this thread replied to, then extatic that you posted, then I read what 'lil did... I am extremely bummed, but just for a second. That was why i was asking "How would some wicked 25Hz tapped horns stack up to 6 soloX 18's ported tuned to 25Hz?"

But hey it's for a great cause so I'll get over it. Not saying you jacked my idea, I know better, jus sayin now I need to find a new daydream brainstorm. That was exactly what I have been working at and around for a couple months now. Even trying to learn Hornresp to see why the soloX 18 isn't as good a choice as the 15's.

Anyway, lookin forward to pics, vids, more results if you choose to share them.

I remember what you asked. The concern I had (and still have) was simply that the "room" is not much larger than the "horn", so I doubt the complex enclosure would be worth the effort, it is easier to just brute-force it. We're working on a little test to validate (or invalidate) that concern. 600 watts, just a single 12. 7 Cubes. 30 Hz. We'll see what the SPL meter tells us regarding a tapped horn and cabin gain.

Remember - this is not ported into the cab of the truck, this is open to the world. I actually wanted to use 6 drivers initially, cause 6-packs and pickups kinda go together.
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