Romy the Cat wrote:

Guys, I am not looking or care about the design specifics but rather looking for some fresh idea and inspirations that would make me to think further. You see, if I shut down Macondo and measure just ULF channels then I have just little bump at minus 6-8dB around 23Hz-33Hz and it is it. For this I pay with two large woofer tower, amps, crossovers, cables etc…   too much mess and complexity for such a small benefit.  I know, I know. I understand that produce this “bump” at 25Hz with relatively low distortions there is no other ways then to go for large and expensive solutions. Still, I always feel that smart and elegant and better than expensive and I would like to find a smarter way to get my bump.

Among all interesting alternative ideas that I have there is one that makes me to think a bit out of shoe box. Of cause I could try that propeller woofer that has so much publicity a few years back. It is small and it reportedly gives low bass.

http://www.rotarywoofer.com/

it is $25K per woofer and I need two, it is absolutely not know to me sound and I have null ability to product how that thing might sound. So, unless the propeller woofer people have some kind of framework that would let people like me to do my home trail I think what they do will be more like internet freak show instead of being a practical and viable solution. I also concern that being located in the same focal location with the rest of speakers the rotary woofer might be too mechanically noisy. I do not mention that my Koshka would for sure object if in the middle of her room I install two cat-chopping machines…

Ok, returning back to my out of shoe box idea. What I would like to have idly would be a properly sounding Sunfire True Subwoofer Junior.

http://www.sunfire.com/productdetail.asp?id=10

This thing is a beauty itself. It is 11 by 11 inch small, it is has own amp inside and has own signal-sensing switch the turn itself on, it able to produce stunning acoustic pressure that can literally bring house down. This is a dream come thought for my placation. There is a small problem with this Sunfire prettiness, the same problem that is very common to anything that Bob Carver ever touched – this True Subwoofer sound like shit. I would not call that crap the this True Subwoofer out as bass but it rather it is some kind of generic pressurization of air and this pressurization has very little relevancy to what is being played.

It is not the point however. No one willing to employ the Bob Carver title fart machines but the idea to get all the bass that I need for my 25Hz bump from one small driver and one sq foot of spare I find is very elegant. The question is: how to do it? How to fuck up to rules of physics and to accomplish what I need to accomplish?

The high exertion of the small driver doe not bother be in my specific application. I need to care just one octave at my 25Hz bump, so all normal problem associated with high exertion are not applicable in there.  The problem with one sq foot ULF section, high power and high exertion is that when woofer is pushing or pulling there is not enough buffered space inside the enclosure, so the compressed air in the back of the sq foot ULF produce tremendous amount of distortions. Ok, but how about if we somehow change the rule of the game and insert inside of this small ULF section some kind of equivalent of Black Hole. Now as the woofer compress the air inside of enclosure the Black Hole would instantly and infinitely to consume that pressure, converting my one sq foot ULF section into infinite baffle. The problem with Black Hole is that when a driver goes out then in order to be infinite baffle the Black Hole shall give instant birth to infinite matter, to become sort of equivalent  of Supernova.

Two much fantasy? Not necessarily.  Let to think in very practical trims. I need some kind of solution that would consume and produce air in my hypothetic one sq foot ULF section. I can’t consume or produce matter but for sure I can transfer it. A friend of mine what I was dumpling all of it to him suggested me convert pressure to temperature. He suggested that if the speaker inside would be partially filled with some kind of liquid or gas that can change temperature from pressure than I might accomplish what I am looking for. I do not think that liquid would do it as it has not fast enough transfer function between pressure and temperature. Pretend that a sealed speaker is filled with gas that that has very fast transfer function and the signal besides driving the woofer power also a circuit that dispatch electrons or ions into the gas (remember a vacuum tube?). The gas has ability to change density, or temperature, or anything after being exposed to ionization. So, what we do is to figure out the delay time the driver need to get momentum and shoot electrons/ions into the gas behind the woofer, assuring that the woofer in falling into collapsed space behind it. As woofer need to go back we reverse polarity on our speaker cathode and suddenly the space behind the woofer behind begin to build pressure (along with drop of temperature for instance). I think we are very far here from Black Holes and Supernovas and with popper engineering support something like this might be experimented with…

oxric wrote:

If it were me and I had that basement that could be made use of, I would seek to achieve what you have done with your mid-bass horns in the loft. I know that you considered and dismissed the tapped horn idea some time ago but it would cost very little for you to experiment with it as opposed to the dual rotary woofers or home-made black hole solutions. If the results are to your liking then, you might consider doing what I will do long term when I have a room with adjoining space either in the form of a basement or loft space (provided I like the results that can be obtained from a tapped horn). I would have the mouth of the tapped horn coming up through the floor at the appropriate point and hide most of the tapped horn itself in the basement. The top part of the tapped horn would be a coffee table or side table and neither you nor your guests would even know that it is there.

Jorge wrote:

In that room we have 3 different bass solutons working toghether,  2 ten inch pro woofers per side from 140 hz down to fs cutoff (around 45 hz) sealed enclosures, and a pair of 15" servo controlled subwoofers one per side  taking it from 50 hz.  And well the tapped horns, that add a nice punch to it all. The big problem with this setup is time aligning everything, or finding the correct phase for all the bass drivers: If something is not perfectly in sync,  the woofers start fighting each other and you get a real mess!  We found out once that by lowering the volume of one channel we got more bass output!!!  Something was clearly wrong!

Jorge wrote:

I need to care just one octave at my 25Hz bump, I have tried the same solution in a big room, the thing is that we not only got output at 25 hz, but a lot also at 50 hz! There was no way surgically cut it to what we needed and the result was it messed everything up.

This is very interesting question. I do not know a lot of people with whom I might collaborate it as very few run ULF channels. Most of time people run just bass channels. It is my experience that whenever audio people talk or think about the lowest bass then they are talking in reality about 40-60Hz. The ULF in sub 25Hz is not well known. It is not the most of the acoustic systems are not able to handle it but rather about that fact the if it is not ULF then the sub 25Hz is not being delivered properly in listening position.

Anyhow, I looking at the debate about ULF that took place at this site: big driver, small drivers, open baffle, ULF DSET and etc, etc, etc I am asking myself question: how  good ULF need to be? The question is simple but the answer is not. If I shut down Macondo and run only ULF channels at FULL power then I have some kind of sound that not truly sound at all. It is 3 and 4 order at 20Hz – there is so little significant information in there! Sure the impact of the ULF is very meaningful but I wonder if in place of my ULF would be 10 times worse sections but still in proper configuration then would they do the job?

A local audio guy just replaced his woofer towers with some kind of pair of JL Audio Fathom F 113 active subwoofers and he reports that he like the result better. Since he use 50Hz horn I presume that he crosses somewhere at 35-40Hz region. I was not a big fan of his former lower bass but I did not associate it with his hardware but rather with setup factors. I did not hear his new bass solution but he put his Fathoms in time-align position – only this got to make difference to my ears.  The point I am trying to make is that we all know that those little fart-machine do not work for bass as audio people know it, means 40-60Hz. However, can those fart machines be more interesting at 20hz?

I keep thinking about it not because I am frustrated with my ULF. My ULF channels perform very well and I am perfectly comfortable with their sound. I am not comfortable with the amount of efforts it takes to accomplish it and I wonder if considering my very 20Hz crossover point I can go away with much less demanding solution. I for sure will not settle with less interesting sound from my ULF but the biggest question is if the fart-machine ULF at 20Hz will be less interesting. I do not have an answer to this question.

In the end I do not mind to try. If some of your have a pair or very good fart-machines then I would like to too offer my listening room and my current setup for an experiment to study how well fart-machines can do in ULF setting. So, bring them in and let see how at all work. I would be in particularly interested in older model of a British REL Reference series…

I am usually not a big fun of somebody refer to eBay Items and I myself do it very seldom. Still, here I am as I think it is an interesting deal for someone. There is a guy out there that is damping a few of Aura RS-8.1 bass modules.

http://www.ebay.com/itm/310366786386?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

http://www.goodsoundclub.com/pdf/AuraSub_1808.pdf

They are Aura 1808 drivers in already built-in, accurate and nice looking enclosures. The price I think is reasonable for the pair of the boxes and since they are in crates then it will be assurance that they will be delivered in pristine shape. The guy will ship, I spoke with him. Use tracking freight service and ship on pallets if you go for it.

What I find is interesting in that that for $1.5K somebody will have right out of shelf, ready to go ULF channels with very good drivers. Do not think that you will be able to run them to 100Hz. Well, sure you will be able to but if you like THAT sound then you is a deaf Moron. This configuration is not for bass generally but for sub 30Hz bass. Also, they are ported, so do not do fantasize about midbass from those woofers.

If you have 40Hz-60Hz horn then you might play with Aura RS-8.1 bass modules and it is possible that it will do very well, crossing them at let say 30-35Hz and to have pain-free and none expensive implementation. I do not know how good the boxes constructed, I do not know if the ports are re-tunable, in fact I do not know anything about them but frankly if I had space for them than I would try them myself. All investment that needs to be done is to replacement the red front grill with black fabric and it is under $10. I do not want to use this configuration in my room – 22” wide it too wide for me, otherwise I would bite it.

Anyhow, whoever is interested – it is all your. Since the guy has a lot of them he might be flexible in price and if you can pick them up than I am sure he will be more accommodating. If you get them then post how you employ them and how they sound.

Paul S wrote:

In the Christmas Spirit, a couple of notes in passing: 1) These units might need a LOT of power to make ULF in those cases... B) "Conventions in Vegas" re: pro speakers = "Little  Old Lady From Pasadena" re: used cars.

noviygera wrote:

I thought I'd let you know that I ordered four of those Aura subs. Thanks for the advice, if I receive them (I hope so), I will install them into my new listening room. This will take a while because I still have a few months away from completing the construction and moving in, but as soon as this happens I will post my findings. My expectations are not set too high, as I was initially planning on building vertical arrays with eight 12" vifa NE bass drivers per side but the ready made Aura solution seemed more practical. We'll see...

Yep, it is interesting how you find them. I need to warn you however, that most frequently people who follow my advise in audio do end up with disappointments as they foolishly feel that following somebody’s path eliminates a need for them to spend own efforts. Anyhow, for all intended purposes I think you got a very good deal.  I pay for my Auras $500-$700 each and it was 10 years back. You got your for $1400, including the boxes and shipping crates – not bad at all. In addition it is my observation that the drivers installed in enclosure are generally in better shape then those that lived non-mounted.

When you get the speaker you would wan to rotate then 180 degree and to break them in a little. Put the speaker face to face, let say 3-4 inch apart, wire then in opposite phase, and driver write noise through then for a few days. Do not overcook them and do not get too loud, user moderate volume. This will softer the suspension for 5-15Hz.

You will need to fine a right power amp to drive them. The power amp type that I use for my ULF I would not user for your Auras, particularly if you have more or less large room at LF. You would need a high current amp able to deal with reverse current and with impedance dive that will coming from that very strong motor when the cabinet port hit its resonance. Also, please, do acknowledge my experience about the crossover – it is very important.  If you remember I did not like at all the harmonics of my bass when I went line level with my SS driving my ULF. I did like the result and it is what I use now when I put a tube crossover into the game. So, the conclusion that I made for a long time ago is that SS can’t drive bass – it has shape but it has no taste or smell. In my case I used the 2-tubes 12AX7 crossover to override with own distortions the tonal impotence of my SS bass amp. The best would be of cause to has a good tube DSET with ultra low output impedance to drive your Auras but good lack to find 250-400W DSET.

Do not even attempt to use them over 35-40Hz. They will work but they will sound not good. Those drivers are 30Hz solution with sharp filter and it is where they need to be used. You might experiment with closing the port.  Aura must be used in sealed box and the ported solution is not good no matter what. For the sealed box you will need 12 cub feet and up. I heard contradictory comments about it and I do not have my own opinion about it. If I did it I would go with 18-20 cub feet but do not hold me labile.

Romy the Cat wrote:

fiogf49gjkf0dI am observing an interesting and surprising fact – I am begging to like my active Marchand crossover. I did a number of modifications to it and it looks like the parts are broken-in now – it does sound very pleasant for my ULF. I feel it is a bit too soft then I would like to have in my final version and I will go for line-level passive what my second B2 will be fixed but this slightly tweaked Marchand today showed off some spectacular result.   I had today a VERY interesting Erotica’s funeral march, played with so much complexity that I thought that Marchand will lose it. To my surprise the Marchand show off very extravagant ULF sound. The slight of softness of Marchand tubes combined with very idiosyncratic bass of old Brunswick orchestra made some spectacular sounds, truly addictive… Who knows, if to spend some attention to this active crossover, perhaps to put better tubes in then it might be a nice devise to use all time. The way how delicate it opens notes is still in my head…. The Cat