Whaddaya mean: "long throw"?

[Rich-n-Texas]

The sub that I got with my Logitech Z-5500 computer speakers is indicated as a Long Throw sub. I have an idea of what this means (the obvious?), but how is it acheived? Due to the fact that I may have the dreaded LFE dead spot right in front of my listening area to deal with, the possibility of supplementing my HT setup with this speaker, that hopefully I can modify to allow line-level input, exists. The B & W sub is in the most practical spot in the room and moving it somewhere else isn't feasible.:idea:

[markw]

Speakers work by moving air. This is done by a cone moving in and out. The distance it travels from the top of it's travel to the bottom is called the "excursion".

To move a certain amount of air, you have two choices:

1) You can have a large diameter cone moving in and out over a small distance, or with a small excursion or
2) You have a smaller diameter cone moving in and out over a greater distance, or a greater excursion.

Generally, the former is the preferred method because it will produce less distortion and generally requires less power, but can be very large. The second method does have the benefit of generally being smaller but require much more power but, since watts are cheap, is a very do-able method nowadays and there are many fine examples.

When a speaker is described as "long throw", it's referring to a woofer usingt the second method to produce bass.

Now, what this has to do with your positioning issues, I have no idea. Sorry...

[GMichael]

It means, "go deep!"

[Rich-n-Texas]

Yer a funny guy GM. A funny guy indeed.

Now... BACK ON TOPIC!!!

[GMichael]

Thanks, but it means the cone goes deep. Deep inside your enclosure. Then it goes farther out than a non-long-throw-driver will.

[pixelthis]

Bass is omnidirectional, you cant tell where it comes from, so no such "bass hole" exists
except in your fertile imagination.
Try blindfolding yourself (no peeking!) and have a friend relocate your sub and try to find it without going by the vibrations, this usually kills any mythological prattle about "directional" bass.
And you are thinking about incorporating a computer speaker into your HT system?
Ever heard about the "weakest link"?
Comp speakers and car speakers sound okay in their enviroment, but next to serious
speakers their deficencies start to sprout.
Trust me, this is a BAD idea:(

[Rich-n-Texas]

Bass is omnidirectional, you cant tell where it comes from, so no such "bass hole" exists
except in your fertile imagination.
Try blindfolding yourself (no peeking!) and have a friend relocate your sub and try to find it without going by the vibrations, this usually kills any mythological prattle about "directional" bass.
And you are thinking about incorporating a computer speaker into your HT system?
Ever heard about the "weakest link"?
Comp speakers and car speakers sound okay in their enviroment, but next to serious
speakers their deficencies start to sprout.
Trust me, this is a BAD idea:(
I think George Lucas would disagree with you...



Standing waves: A direct result of a room's dimensions and the wavelengths of low-frequency sound waves, standing waves make the bass sound thin in one place and bloated in another. They can't be eliminated, but they can be tamed, usually by moving the subwoofer to another spot or adding another subwoofer.
But to put it in my own words...



After taking measurements of my living room and finding the room's center, I stood there with an SPL meter, and with all speakers placed where I wanted them I played the test disk while looking at the meter. No response during the LFE test. When I moved to a corner of the room, the meter responded.

Some of the folks here at AR have already pointed out that deficiency in my setup. Again, I don't want to move the sub and I've tried to pivot it where it sits but nothing changed. While my 5.1 rig connected to my computer served me well, I now have a nice big room for my multi-channel needs, and since my PC's got problems that'll probably require another MB, chances are I won't be listening to iTunes or playing video games on it anymore. The next rig will be incorporated into my HT system. I won't know if I even can use that sub until I've checked it's specs anyway, so that's really just a shot in the dark. I'll tell you what though, that Logitech long throw active sub's got some serious punch!

[markw]

For all intents and purposes, the low bass from your sub is omnidirectional and pivioting it will not really do anything.

Sorry to say, but as far as those pesky room nodes go, they are boundary dependant and, unless you can reposition the walls, floor and ceiling, the only way to deal with them is to move the sub to another position.

By replacing that sub with another of similar output, you will get the same results.

Bass absorbers can help to some degree but remember, these are most effective after the sub is positioned as optimally as possible. They are band-aids and you're dealing with a gaping chest wound.

[Rich-n-Texas]

For all intents and purposes, the low bass from your sub is omnidirectional and pivioting it will not really do anything.
I understand the low frequencies, just by their nature hide themselves from human hearing.


Sorry to say, but as far as those pesky room nodes go, they are boundary dependant and, unless you can reposition the walls, floor and ceiling, the only way to deal with them is to move the sub to another position.
Hmmm... Well, I do have a hole in the ceiling I have to deal with... :ihih:


By replacing that sub with another of similar output, you will get the same results.

No no, not replace, add another one. Connect from the Line Out, (or Link Out?) of the B&W sub to a modified Line In jack on the Logitech sub and then place that smaller sub somewhere behind the seating area.


Bass absorbers can help to some degree but remember, these are most effective after the sub is positioned as optimally as possible. They are band-aids and you're dealing with a gaping chest wound.

I'm about to post some preliminary pictures of my room in the Photo Gallery and you'll see why I'm fighting the prospect of moving the sub.

[kexodusc]

Long throw just refers to the excursion capabilities of the woofer. Honestly, it's usually just used as yet another crappy marketing term, like RMS power, MOSFET amps, etc...nothing special. What is "long-throw" exactly? 5mm? 10mm? 30mm?

FWIW, I'm of the opinion most woofers with really "long-throw" sound like crap due to terrible transient response and weak motor control. There are a few exceptions, but you're gonna pay for them. If space allows it's often cheaper and better to just add another woofer than to add excursion. I've seen some 5mm excursion subs call themselves long-throw. :rolleyes:

Just my opinion.

[Rich-n-Texas]

Thanks Kex for your directness in answering my questions. My main intention for adding this other sub isn't for the fact that it's long throw (guessing I put too much emphasis on this term), but just because I have a second sub that's about 1/4th the size of the B&W to potentialy work with.

I do watch a lot of TV and I use my receiver for the audio because the local OTA channels broadcast in hi-def and include multi-channel audio, but my main focus for my system is music, including concert videos and such. I like a LOT of bass (not boomy bass though), so two sub's... I could get along with just fine. :thumbsup:

[E-Stat]

For all intents and purposes, the low bass from your sub is omnidirectional and pivioting it will not really do anything.
I looked at data concerning his Logitech Z-5500s and find that the satellites use 3" drivers. If memory serves, bass is omnidirectional below 80 hz. While the Logitech site doesn't mention the crossover frequency, I think it's a safe bet that the sub operates way above 80 hz to match the tiny mains.

I would think that this sub, like the unit with my computer speakers, is directional in its operation.

rw

[basite]

I'll tell you what though, that Logitech long throw active sub's got some serious punch!


you're looking at it the wrong way: the logitech doesn't have that much clean punch, my creative soundworks pc soundsystem ( a $400 pc soundsystem, that is) disorts so much in the lows that it gives you the impression that there is alot of bass.
that is what happens with you too your sub's lowests freqencies are like 10% disorted (no joke).
secondly, those things aren't made to fill an entire room...

otherwise, experiment, experiment, and eventually blow the logitech sub...
it has to be said though, the logitech will provide you some mid-bass, and will create an 'oomph' sound when you set it up together with the B&W...
why don't you just buy or build a really big sub, (or a second one)?

anyways, let us know...

Keep them spinning,
Bert.

[Rich-n-Texas]

Here's a clickable thumbnail of the sub's location. Pay particular attention to that 60's vintage Akai M9 reel-to-reel with the "Original Crossfield recording heads". :biggrin5:

http://i115.photobucket.com/albums/n286/rich3fan/Home%20Theater%20photos/th_RFrontandsubposition2.jpg (http://i115.photobucket.com/albums/n286/rich3fan/Home%20Theater%20photos/RFrontandsubposition2.jpg)

And here's an ants-eye view (just b/c I'm using Photobucket's IMG features for the first time):
http://i115.photobucket.com/albums/n286/rich3fan/Home%20Theater%20photos/th_subantseyeview.jpg (http://i115.photobucket.com/albums/n286/rich3fan/Home%20Theater%20photos/subantseyeview.jpg)

I'll put the other pictures in the gallery soon so you'll have a better idea of why I don't want to move it. Suffice it to say, the sub's completely out of the way where it sits now.

[topspeed]

You might want to try this Behringer Feedback Destroyer (http://www.parts-express.com/pe/pshowdetl.cfm?Partnumber=248-656). It's a reasonably inexpensive way to help smooth out room response, although I don't know if it will be able to alleviate the node your sitting in. Room acoustics are what they are.

Read this thread from Doc Greene, our former sub guru.
http://forums.audioreview.com/showthread.php?t=2461&highlight=richard+greene

[Rich-n-Texas]

I read "Doc's" informative post, but it raised more questions in my head. For instance, when he says room modes can be excited, does that mean other frequencies can break the standing waves? B&W says in their literature of the time that their patented technology of employing Kevlar cones in their lines will reduce standing waves. Is that really true? And if so, could it be my reciever isn't doing a good job of exploiting this capability? In the pictures I've posted in the Gallery you can see that, although my room measures about 18' x 18.5', the left front is pointing towards the living room from essentially the area by the front door (forget what that space is called), so I don't know what "axial room mode" that puts my setup in...



Boomy = A large peek around 60htz. May not have much lower exstention.
Muddy = Clomplete crap. Sounds terrible at all frequencies.



Mike's got it.

Boomy correlates a lot of bass as actual good bass. This is naturally not true. The old adage "Bass, bass, all over the place" comes to mind. Muddy simply means everything is blending together. There is no definition, no clean delineation between notes or start and stop.



let me add my 2 cents:

Boomy= alot of echo bass bouncing throughout the room along all feq
Muddy=dull un-define lacking tightness, They way most tuner cars sound, all boom.

Your sub should hit like a heart beat, not linger on or echo. Boominess can be results of room surfaces (hard floors/walls) and placement. Muddy is more of a poor sub driver/crossover setting itself, not able to give a tight response.

You should only really hear the sub when the action calls for it not during the normal dialog. Your sub is always working in a support role until its called upon to bring that chest pounding, window shaking, seat rumble effect. Then just soon as it hits it should jump back in its support role as if you never knew it was there.

Thanks all for this input from the muddy vs boomy thread. Actually I think I've experienced both at least once. I was listening to a DVD-A and during one heavily bassed passage, I heard what seemed and felt like a loud vibration throughout the room. Mostly though it seems like I hear muddiness (i.e. no clear punch in the chest sensation).

This past weekend I moved the sub to two other locations: about 4' to the left, which put it on the fireplace about 10" above the floor, and which also put it about 36" away from the right front speaker, but nothing changed. Then I moved it about 3' to the right from its original location, but that also made no difference. I need to do some more experimenting, and even though it's not likely to help, get my new furniture into the room then watch some DVD movies with a good multi-channel mix. Doc Greene included a website for a test CD... linkwitzlabs.com so I'm wondering if I should include this option in my tests.

BTW, I was able to verify this null with the Simpson model 899 Impluse Sound Level meter. After setting the mains and surrounds to give me 70dB near the center of the room, (-8dB setting at the receiver's volume control) I had to set the level of the sub to +7db at the receiver (mid-way at the sub's amp), to get close to +70, and this level was 4dB higher than the right front about 5' away from it.

BTW2, how does Dynamic Range Compression factor into this equation?

Anyway, thank you again for your continued support. :thumbsup:
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[kexodusc]

I read "Doc's" informative post, but it raised more questions in my head. For instance, when he says room modes can be excited, does that mean other frequencies can break the standing waves?
Break the wave? Umm, no not really, but I guess more waves could change the apparent effect of the standing waves? Superposition of two waves can create them depending on their direction, I think that's what you're wondering about...


B&W says in their literature of the time that their patented technology of employing Kevlar cones in their lines will reduce standing waves. Is that really true? And if so, could it be my reciever isn't doing a good job of exploiting this capability?


When you say "Kevlar" cones in their lines...you mean transmission lines? What models does B&W have that are honest T-lines? Geez, I haven't paid attention to B&W for years. Kevlar is just a tough driver material that will reduce distortion, and I suppose could help reduce standing waves inside the cabinet or down the transmission line, but we're talking about your room not the speaker itself. The driver material isn't going to do much to prevent standing waves in your room, that's a function of the law of physics, and the dimensions of your room vs the frequency of sound you're playing.
Your receiver has nothing to do with standing waves or exploiting that ability...




BTW, I was able to verify this null with the Simpson model 899 Impluse Sound Level meter. After setting the mains and surrounds to give me 70dB near the center of the room, (-8dB setting at the receiver's volume control) I had to set the level of the sub to +7db at the receiver (mid-way at the sub's amp), to get close to +70, and this level was 4dB higher than the right front about 5' away from it.


Bass waves are far more fussy than the rest of the spectrum as you're coming to learn. As Topspeed mentioned, parametric equalization from a unit such as the Behringer Feedback Destroyer can help "smooth" the response of your subwoofer. In my room, I got peaks and dips more than +/- 12 dB before EQ'ing. That's not uncommon, but it sure contributes to some excess boom, at times...For less than $100, I cannot think of many pieces of equipment that contribute so much to sound quality.


BTW2, how does Dynamic Range Compression factor into this equation?
Dynamic Range in simple terms is just the difference between the loudest and most quiet sounds. The wider the range the better. When you compress that range, you're moving the volumes of all things loud and quiet towards the average volume. So in Jurassic park, the kids whispering will sound as loud as T-Rex roaring - this isn't very realistic, but it's great in apartments late at night when you don't want the loud scenes to wake the neighbors, but still want to be able to hear the dialogue.

[Rich-n-Texas]

Break the wave? Umm, no not really, but I guess more waves could change the apparent effect of the standing waves? Superposition of two waves can create them depending on their direction, I think that's what you're wondering about...
This is what he says:


Room dimensions have nothing to do with how smoothly ("evenly") room modes
(standing waves) are excited.
What does he mean by that?


When you say "Kevlar" cones in their lines...you mean transmission lines? What models does B&W have that are honest T-lines? Geez, I haven't paid attention to B&W for years. Kevlar is just a tough driver material that will reduce distortion, and I suppose could help reduce standing waves inside the cabinet or down the transmission line, but we're talking about your room not the speaker itself. The driver material isn't going to do much to prevent standing waves in your room, that's a function of the law of physics, and the dimensions of your room vs the frequency of sound you're playing.
Your receiver has nothing to do with standing waves or exploiting that ability...

I meant product line. B&W used kevlar instead of paper in their Matrix and P6 series mid-range speakers. That can be seen in the pictures I posted. They have a yellow color.


Bass waves are far more fussy than the rest of the spectrum as you're coming to learn. As Topspeed mentioned, parametric equalization from a unit such as the Behringer Feedback Destroyer can help "smooth" the response of your subwoofer. In my room, I got peaks and dips more than +/- 12 dB before EQ'ing. That's not uncommon, but it sure contributes to some excess boom, at times...For less than $100, I cannot think of many pieces of equipment that contribute so much to sound quality.

I'll keep that piece in mind.


Dynamic Range in simple terms is just the difference between the loudest and most quiet sounds. The wider the range the better. When you compress that range, you're moving the volumes of all things loud and quiet towards the average volume. So in Jurassic park, the kids whispering will sound as loud as T-Rex roaring - this isn't very realistic, but it's great in apartments late at night when you don't want the loud scenes to wake the neighbors, but still want to be able to hear the dialogue.

I was reading about DRC in my receiver's manual. I understand what you're saying... I think I was assuming that by bringing louder sounds closer to average with softer sounds I could affect the LFE response. Bad assumption yes?

[kexodusc]

This is what he says:

What does he mean by that?


That the actual placement of the sub, intensity of the signal, and your listening position all contribute more to the effect of standing waves from the listener's perspective. He's not saying the room has no effect, but that it has effect on the center frequency, not the intensity of the standing waves. Ie, a 15 ft long room doesn't have bigger boom just because it's 15 ft long than say a 20 ft room.


I meant product line. B&W used kevlar instead of paper in their Matrix and P6 series mid-range speakers. That can be seen in the pictures I posted. They have a yellow color.
Yeah, I know all about them. Kevlar doesn't control or reduce the effect of standing waves in the room, at least not by any physics I'm aware of. I think B&W is referring to the standing waves created inside the cabinets themselves, but even then I'd question whether this statement was just more marketing spin than fact. I don't know for sure, but I'm skeptical at best.


I was reading about DRC in my receiver's manual. I understand what you're saying... I think I was assuming that by bringing louder sounds closer to average with softer sounds I could affect the LFE response. Bad assumption yes?
Yeah, it'll affect the signal, but any impact the room has will remain unaltered. The sum of the two might sound a bit different though.

When you breakdown the contributions of all factors to the sound you hear, you could simplify it down to 3 things that contribute to sound in reasonably equal proportions:
1) electronics & speakers
2) Room acoustics and their effect on the sound source
3) The listener's psychoacoustics and physical acoustics (I have a friend who's an audiologists who showed me a study that the shape of your ears can affect the sound quite a bit, for example). That gray lump between our ears has some role in this too.

We can most easily control the first one, the stuff we buy...

The second takes quite a bit more effort, learning, and a wife who doesn't mind a bunch of weird looking wall treatments in many cases. Manipulating speaker placement, using room treatment, etc, help us minimize the distortion of the original source. But you'll never, ever hear the perfect original signal at your listening position.

The third is fixed for each individual, but contributes to why some people think one speaker or receiver sounds better than another, why some people like "bright" sounding gear, and others warm sounding gear, etc...This probably contributes to most of the fights in the audio industry over #1 and #2.

Your receiver's Dynamic Range Control, and all those other settings are geared towards optimizing the sound you hear at your listneing position. They affect the sound that's generated out of the speakers. Once that sound is out of the speakers, its at the mercy of your room's acoustic environment, and your ears. The most those settings can do is compensate for any effect the room has on the sound (and maybe some sensitivities in your hearing). That's what an EQ does. If you have a bass peak 10 dB at 60 Hz, cutting the bass 10 dB at 60 Hz leads to net bass signal at 60 Hz at +/- 0 dB relative the main signal.

Some of us here ar.com have advocated that the room can make as big an impact on sound as all the stuff you buy - at the very least, it can reduce finer grade equipment to performing well below spec.

[Rich-n-Texas]

Very good. Your explanation puts things into terms I can understand. :thumbsup: Frankly I was overwhelmed by what Doc was saying. Too deep for me.

[bfalls]

I have a question concerning the phase switch available on most standalone subs. From what I've read the switch is used to match phase with the front speakers. If your listening position is in a null region for bass, wouldn't switching the phase 180 degrees put you in a peak region? This option probably isn't available on LogiTech multi-media speakers, but I'm talking in general. Isn't this one of the first steps when setting up a subwoofer.

[Rich-n-Texas]

I was going to bring that up because I thought the exact same thing. Well, I tried flipping the switch on the back of the B&W sub to 180 degrees, but it made no difference. Then I changed the setting at the receiver, still made no difference. Went back to the sub and flipped the switch back to zero.. no help, so I then changed the receiver back to make eveything as it was and continued on.

I went back to L.J.'s topic about his home theater and the acoustic panels that he put up. I'm going to try to find some Owen's 703 fiberglass panels and burlap this weekend and put my arts-n-crafts gloves on.

[kexodusc]

I was going to bring that up because I thought the exact same thing. Well, I tried flipping the switch on the back of the B&W sub to 180 degrees, but it made no difference. Then I changed the setting at the receiver, still made no difference. Went back to the sub and flipped the switch back to zero.. no help, so I then changed the receiver back to make eveything as it was and continued on.

I went back to L.J.'s topic about his home theater and the acoustic panels that he put up. I'm going to try to find some Owen's 703 fiberglass panels and burlap this weekend and put my arts-n-crafts gloves on.


The phase switches won't necessarily solve your problems with the nulls. Especially a 180 degree switch type, variable ones might help. I can't even say that a variable phase control would change the location of all the nulls in the room.

As for the OC703 fiberglass. It's good stuff, I'd suggest looking for a different brand though if you could. I used Ottawa Fiber after the first batch of OC 703. Most rigid fiberglass of equal density performs the same, in the case of Ottawa Fiber, it's an insignificant step up. But it's a lot cheaper, Owens Corning are often the most expensive.
Others have had good success with Knauf as well. There's others. Mineral wool might be a great cheap alternative to rigid fiberglass if you build frames for it.

[Rich-n-Texas]

Kex, will I be able to find this fiberglass you mention at the Home Depots of the world, or should I be looking at places like the one L.J. mentioned: atsacoustics. When I'm cutting, should I treat it with the same caution as I would fiberglass atic insulation? I understand that it's a rigid material but my concern is with the fiberglass sawdust produced when I'm cutting it. Thanks.

[kexodusc]

Kex, will I be able to find this fiberglass you mention at the Home Depots of the world, or should I be looking at places like the one L.J. mentioned: atsacoustics. When I'm cutting, should I treat it with the same caution as I would fiberglass atic insulation? I understand that it's a rigid material but my concern is with the fiberglass sawdust produced when I'm cutting it. Thanks.
Hmmm, I dunno about Home Depot, I didn't check there, I tried a few local building supply chains in my area and they all had to order it.

I called an a/c and heating distributor I found in my local yellow pages. After 2 or 3 a/c companies, I found someone who shipped me 300 sq ft worth of it for around $0.65 per square ft...I have a few bundles stacked in my basement now, but I'll use'em eventually.
Other people have found rates anywhere from $0.55 to $1.25 per foot. I think this is much cheaper than ATSA was. Sometimes you can get open bundles that are just taped back up . The panels come in fine. I even bought a few pieces with slightly banged up edges. Which was fine for me, I didn't build all my panels 2' X 4' in measurement anyway. To be fair I know a lot of people find ATSA to be the cheapest they can get - it's not the easiest stuff to find, but if you live in a big enough area with some industrial suppliers, you should be able to find one who'll sell you a small amount.
Took me about 10 minutes to save a couple of hundred bucks.

Just make sure it's 2 inches thick, rigid fiberglass of 3 lbs per cubic foot (pfc) density. Then you can find the absorption coefficient specs of the brand you're looking at and compare with OC 703, most are the same give or take 2% performance, and cheaper.