Ultra II Subs

[DrWho]

The number is 1-800-KLIPSCH - it's probably your best bet for the shielding question. I think nobody has answered because nobody knows the answer for sure.

For what it's worth, the curved slot port in the Ultra2 subs was a compromise to make it suitable for flush-mounting. Passive Radiators are always better than ports, but much more expensive. Despite the cost advantages, ports are still used because they become less compromised the higher you tune them. There isn't much research available in the public domain regarding PR's, but I know Klipsch did a ton of research in the mid 80's (thus the Forte, Chorus, Quartet, KG, etc... lineups). If I were to draw a line, it seems 30Hz is about the turning point where the extra cost of PR's becomes worthwhile - but it depends mostly on the size of the enclosure.

The reason for using more passives than actives is because the passives need to displace more air than the active driver (they're operating at lower frequencies). The general rule of thumb is to have double the displacement available.

[colterphoto1]

I don't know if you could physically mount bucking magnets inside the THX sub bin. There is already quite an enormous magnet in there. Unless someone in Tech Support already knows the answer, we'd have to check engineering drawings or disassemble and measure to see if it would feasible.

M

[tidmack]

Tom,

Here's a very "non-engineer" point of view. The more I read about the Ultras, the more I realize I haven't even come close to their max output. I have them in a 20X13 living room with a 10 foot long window, hallway on one end, and entrance to the kitchen on the other, hardwood floors throughout, and 8 foot ceilings. Hardly a perfect room, but I have an absolutely crazy amount of bass. I run my ultras with a pair of LaScalas and use them mainly for music and only watch movies in two channel.

What impresses me most about these subs is their ability to reproduce bass notes accurately and at levels that match the volume of the LaScalas. . .many here have said they keep up with Heritage well and I agree. Even at 104 ish dB's (watching meters on the Mac), the subs keep up effortlessly. To me this is a ridiculous volume and I only do it to see if I can. Last night, I watched Neko Case's Austin City Limits DVD and fell in love with her and my speakers all over again. The upright bass could've been in my living room. You can literally hear Tom strumming the instrument, yet the lower notes shook my pants. Incredible.

If explosions are your thing, the Ultras do these well too. I recently watched King Kong and my walls shook a few times. When I say shook, I mean it. The explosions, stomping, other effect. . .will hit you dead square in the chest and leave you wondering who threw the punch.

At the end of the day, I'm completely satisfied. I listen loud, but not outrageously loud. I've never heard the Ultras fart, burp, or make other weird noises. I think it might be impossible to blow them. Really.

NOTE: Take everything I say with a grain of salt because I haven't heard other subs at this price point. As others have said, there may be better choices for the money, but I am completely satisfied with the Ultras. . .

Jeff

[kramskoi]

In a small room I'd probably go with a sealed system too []

Btw, what is an LLT alignment?

first of all...i apologize if i come off a little confrontational...not my intention...i'm still a baby with all this stuff...while i do think that sealed is a potent performer in small rooms, it would'nt necessarily be the best way to go in larger rooms...here the LLT is perhaps the best option, although it will also require multiple drivers and substantially larger cabinetry...this becomes more feasible with the larger space involved...if you can get your wife or s.o. to accept these monster sized enclosures, you can give sealed enclosures a real run for their money...

That said, this design will naturally fall outside the mainstream for output and extension.

LLT subs are usually tuned between 12-16 Hz, with enclosure sizes of about 250-300 liters per driver...so you can see that using multiple drivers really chews up real estate.

The design is run without highpass filtering so this requires amp limiting the driver(s) for infrasonic protection...this is one of the drawbacks to the system, but if you use enough drivers it becomes less of a problem. Care must still be taken with infrasonic material though.

Over the audible range, it supposedly mimics the characteristics of a sealed enclosure but, because of the abnormally low tuning, it allows you to extend lower than a comparable sealed unit. Group delay is quite high at the lowered tuning point, but falls to inaudibility in the muscial range so it is nothing to worry about...in theory of course.

In summary, it is supposed to mimic the sealed box in the audible range and extend the Fb of the system to a lower level than normal vented or sealed designs...and you keep massive midbass output with the multiple drivers. A best of both worlds solution for all.

This design is not without drawbacks though, as i mentioned in previous posts...markedly reduced midbass output, distortion limited output below Fb, size, port velocity (audibility), elevated 20-30 Hz distortion and possible bottoming above Fb, cabinet colorations and port resonance issues...although if carefully designed, a lot of these concerns can be marginalized...it is a sound theory and has been put into practice by various DIY'ers like me...and with good results. Granted we have'nt seen one tested head to head, those who've built them swear by the output and musicality.

[DrWho]

no need for apologies (but I too apologize if I came across confrontational). Engineering should be devoid of emotion, but that doesn't mean we shouldn't play nice. I must confess that I enjoy these discussions.

Ultimately, I think it all comes back down to picking the compromises. If one makes an educated decision trying to cater to the specific application, then that's all that matters. The annoying part is that most hobbyists generally don't get to build a million different designs and choose for themselves the compromise chains that they prefer. In that regard I seriously envy the loudspeaker engineers that get to play with this stuff everyday.

[Raider]

FWIW, to me as a third party, neither of you came across aqs confrontational. Rather, you just engaged in debate, in the true sense of the word: " a formal discussion on a particular topic in which opposing arguments are put forward". I was impressed by the obvious mutual respect -and openmindedness- displayed, which is why I commended you earlier.

Would that more participants in forums these days could more constructively debate as you have done.

[mas]

"I don't know if you could physically mount bucking magnets inside the THX sub bin. There is already quite an enormous magnet in there. Unless someone in Tech Support already knows the answer, we'd have to check engineering drawings or disassemble and measure to see if it would feasible. "

Michael,

On that note I have wondered if a sufficiently large piece of conductive sheeting that was grounded to a common ground point (i.e.- the concept of a star ground or a common bond - thus eliminating differentials in ground point potential) - such as a thin piece of sheet metal, or even conductive screen that could be sewn between two sheets of cloth, or - for more fragile mesh - sandwiched between 2 sheets of inexpensive luan, with a cord(wire) for attachment to a common ground, could be placed between items such as a TV and a non-insulated speaker - thus forming a simple truncated Faraday cage 'surface'.

Does that description make sense?

It is one of those ideas that I have simply not had sufficient need nor opportunity to try for verification, but I suspect that it would provide quite adequate effective shielding in all but the most extreme situations. And it would be very cheap and easy to verify.

[DrWho]

I don't think Farday Cages work at DC??? Doesn't the skin-depth approach infinity as you lower the frequency (and keep everything else constant)?

Skin Depth for a good conductor = 1/SQRT(pi x f x u x o)

(u = greek mu, and o = conductivity)

[mas]

It works great for electrostatic discharge up to and including lightning (think of your car), and I can't think of a more powerful DC source than that.

Besides, and alternative method of shielding cabinets is to line the cabinet with conductive material and to ground it...we're not talking about a really radically different method - just an easier application.

Mesh :

http://www.twpinc.com/twp/jsp/product.jsp?type=11&gclid=CL-vheOM9IcCFQrXSgod6DsefQ

NASA RFI Shielding Design Guide - since the site won't let me attach the PDF; download this!:

http://www.twpinc.com/twp/jsp/productTypeText/popup/rfi/19970036055_1997067804.pdf

While I have had experience working with such materials for insulating Data Centers and RF/Microwave HeadEnds, but I have not played with the small applications. A simple case of the cobbler whose kids go barefoot or the car mechanic whose own cars don't run! [] Hey, where else does one have the option to say stuff it when you are told to jump - even if its yourself!? [][8-)]

Oh, in a completely separate tangent connected by electrostatic discharge from a most unexpected source, be SURE to watch the new NOVA where the TRUE cause of the Hindenburg disaster is identified - and hydrogen had nothing to do with it!!! Fascinating!

[DrWho]

I'll go bug my prof about your idea since we're talking about shielding in class right now. If he thinks it'll work I'll go ahead and purchase some of that mesh crap and test it for myself. I've got tons of subs and speakers laying around that I'd like to get closer to the TV so it's definetly worht the effort (heresy center channel anyone?).

[Tobby]

Saw that piece on the Hindenberg last night. Very interesing. Evidently powdered aluminum and iron oxide combined does not make a good coating for a Zeplin skin. I did some experimenting today and moved my Revel b15 next to my old crt rp tv and wow. Not good. The magnet caused the colors to bend and seperate. It started at about three feet to thirty inches away and increased as I moved the sub closer. It did not mattter if the sub was powered up or not. White credits. for instance, had a red duplicate that moved in the direction of the sub as I moved it around. So I took Doc's advise and called Klipsch tech support. Very good experience talking with them. I got straight through and the guy was very helpful. Should have got his mame. Here is some of the information he gave me.

1.Crt tvs are especially suceptible to unshielded speakers and most all subs are unshielded (if not all). DLPs in most cases won't be effected and Plasmas will not be effected. To find out about a particular tv call the maufactuers tech support.

2. Very few subs(if any) are shielded. I believe he said it is impractical because of the size of the magnet and the space in the enclosure any magnetic shielding would take up.

3. Something as simple as an ungrounded cookie sheet has been know to effectivly shield smaller speakers and something larger would probably work on a sub. According to him shields do not need to be grounded.

4. For information on shielding go to lessemf.com. They have information on and products for shielding.

I apologise to him, tech support, if I am inaccurate in my understanding of anything he said.

Tom

[Tobby]

I just visited the lessemf.com web site and they provide three methonds for shielding speakers.

[Tobby]

I just visited the lessemf.com web site and they provide three methonds for shielding speakers.

1. A two layered shielding material applied directly to the magnet inside the speaker.

2. A magnetic shielding foil applied between the speaker and display devise. This can be applied in multiple layers if needed.

3. A shielding enclosure.

The magnetic shielding foil sounds like the best bet for my situation if it turns out I need any shielding at all. It may be that the lcos or possible dlp purchase that I intend to make will not be troubled by the big magnets. I think I'll give sony and samsung tech support a call tomorrow.

Tom

[mas]

Tom,

That is what we have been referring to...

Adding/retrofitting a bucking magnet to the speaker magnet is not a practical solution on a large woofer - especially in a finished design.

You can also try to line the enclosure with conductive film, but that is more difficult then simply placing the conductive surface between the two units.

All that is needed is a conductive surface sufficiently large to 'block' the B-field from the speaker magnet.

Don't make this too complicated. Oh, and it does not require a solid material to block the magnetic ( field - a mesh screen is sufficient and presents a flexible alternative.

If appearance is not critical, a large piece of sheet aluminum from Home Depot can be used as a tray 'shield'...

[Tobby]

Tom,

That is what we have been referring to...

Adding/retrofitting a bucking magnet to the speaker magnet is not a practical solution on a large woofer - especially in a finished design.

You can also try to line the enclosure with conductive film, but that is more difficult then simply placing the conductive surface between the two units.

All that is needed is a conductive surface sufficiently large to 'block' the B-field from the speaker magnet.

Don't make this too complicated. Oh, and it does not require a solid material to block the magnetic ( field - a mesh screen is sufficient and presents a flexible alternative.

If appearance is not critical, a large piece of sheet aluminum from Home Depot can be used as a tray 'shield'...

Mas

What's complicated? I was simply passing along some information that may be of help to anyone with real word magnetic shielding issues. For my part, my questions in this area have been answered. Thanks for the help. By the way, aluminum's permeability is too low to make a good shielding material.

Tom

[Tobby]

I appreciate your point of view. That kind of talk really makes me anxious to get the ultras in. After I get everything set up I'll let you give you my impression which you can take with a grain of salt also.

Tom

[Tobby]

Tom,

Here's a very "non-engineer" point of view. The more I read about the Ultras, the more I realize I haven't even come close to their max output. I have them in a 20X13 living room with a 10 foot long window, hallway on one end, and entrance to the kitchen on the other, hardwood floors throughout, and 8 foot ceilings. Hardly a perfect room, but I have an absolutely crazy amount of bass. I run my ultras with a pair of LaScalas and use them mainly for music and only watch movies in two channel.

What impresses me most about these subs is their ability to reproduce bass notes accurately and at levels that match the volume of the LaScalas. . .many here have said they keep up with Heritage well and I agree. Even at 104 ish dB's (watching meters on the Mac), the subs keep up effortlessly. To me this is a ridiculous volume and I only do it to see if I can. Last night, I watched Neko Case's Austin City Limits DVD and fell in love with her and my speakers all over again. The upright bass could've been in my living room. You can literally hear Tom strumming the instrument, yet the lower notes shook my pants. Incredible.

If explosions are your thing, the Ultras do these well too. I recently watched King Kong and my walls shook a few times. When I say shook, I mean it. The explosions, stomping, other effect. . .will hit you dead square in the chest and leave you wondering who threw the punch.

At the end of the day, I'm completely satisfied. I listen loud, but not outrageously loud. I've never heard the Ultras fart, burp, or make other weird noises. I think it might be impossible to blow them. Really.

NOTE: Take everything I say with a grain of salt because I haven't heard other subs at this price point. As others have said, there may be better choices for the money, but I am completely satisfied with the Ultras. . .

Jeff

Jeff

I appreciate your point of view. That kind of talk really makes me anxious to get the ultras in. After I get everything set up I'll let you give you my impression which you can take with a grain of salt also.

Tom

Wouldn't it be nice if you could delete you own posting mistakes.

[joncro55]

Another great source to find some of the mesh is:

http://www.bwire.com/index.htm

Fast and cheap shipping, as well as a large inventory of mesh in stock and ready to ship ASAP.

I used them last year, and the guy I talked to on the phone was really helpful when it came to identifying exactly what size mesh and what type of metal would be best for what I was using this for.

[CECAA850]

Yet another 4 year old post trudged to the top.

[TheEAR]

Weee lets bring 50 year old threads! WEEEEEE