Which subwoofer?

@bdp24 

Thanks again. You are right I was misunderstanding what the models implied. I totally get the F12 since mine are F12-like in heavy DIY sealed boxes. I thought the F12G were paper cone and open baffle (like Danny's designs), but I see on Rythmik's site they are sealed. So let me rephrase and provide perspective for what I was saying:

I though he ran F12 up to 40Hz, xo to OB subs (his Kit 4 or 5) from 40 to say 180Hz, and then xo to another driver. I guess my thinking was biased by the way I set up my system. And I know another user who runs multichannel stereo and used F12s (to 50Hz) in such a fashion with F8s above (frequency-wise) to 175Hz and JBL M2 above, so I though Danny was doing this but on OBs. 

I totally understand why he does it the way you describe it too: below 40Hz he gets 4 sources playing (F12s and OBs) so a DBA. Worth noting Earl Geddes argues for 3 or 4 subs and says the 3rd and 4th subs don't need to be as powerful, which in Danny's case would be the OBs below 40Hz. Then Danny gets OB bass with servos from 40Hz to whatever he xo, and let a regular driver take it from there. Makes a lot of sense and would demand a redesign of my system because those F12Gs would replace my dipole 18" but would not reach as high and the smaller surface (2x12" vs 1x18") I guess would be perceivable. In my prior iteration I had 2x10" in the midbass and the move to 1x18" was a significant step up in impact of bass while also having dipole texture (of course an 18" in a box would have more impact than it in dipole). Maybe I need the 3x12" GR Research :-)

Good food for thought!

BTW: do you place your OB subs close to the side walls? In my case I would need to, maybe 4 or 8" from the side walls in the front corners, 2 or 3 feet away from front wall...not ideal distance to front wall, but space constraints. I wonder if being close to the side walls would further detract from them.

You really need several subs in any system no matter what the room size.   It is just a matter of which sub you decide on getting.    I have a lot of experience with many different subs in my listening area which is a very complex room to fill properly.  The area is not your more common rectangular room with a flat ceiling;  I have around 14K cubic feet of space with an 18 foot vaulted ceiling in the main section with overhead balconies, stairs and a cantilevered overhead room in the rear section adjacent to the main entrance which open.  There is a lot of glass on the eastern wall, mostly stone on the western wall with natural wood on both the north and south wall areas where the stairs are located going up to the cantilevered balconies and room.

After several years of testing multiple combinations of speakers and subs, I have this place really dialed in to the point it sounds like a concert hall.  I have about 7000 watts of power between my two mono block main amps and the various other subs strategically placed for wall location and spacing/phasing.   My brother who is a professional video producer and audio engineer said the system sounds the closest to anything he has ever heard to a real live concert (he has worked with a number of major national rock bands).   The key to this system is twofold:  great subs and great placement of the speakers with proper phasing.  Of course the main speakers are the most important part too.   

After extensive testing and trials, I settled in on a pair of Bryston Model T main speakers which have triple 8 inch woofers, dual 5.25 inch mids, and dual titanium tweeters and they are set up with the fully active input system, but I am not running the fully active electronics, instead I am using the super heavy duty passive PX-1 massive external crossovers and each speaker gets 2300 watts from a mono block amp.   

For subs, I have used a number of products (several of which have been spoken of in this thread) and I'd skip over all of them as I have found the Axiom Audio subs to be the best of the lot by a long margin.  First of all, they have the best drivers which are indestructible and their power supplies are all massive linear supplies with monster toroid wound transformers.  They do not use switching power supplies as every other sub I tried uses.  The dynamic head room is hands down way out over the others which makes for the cleanest, pure tight bass I have experienced.  These subs are what makes low end musical!  Every other sub I tested sounds like bottom of the lake muddy low visibility.   If you do not want to "hear" your low end, that is know where your subs are in the room, but wish to have just balanced, clear, full range music, you owe it to yourself to try these subs out.

My most beautiful sub by far of the lot is my Bryston Model T sub with its triple 8 inch drivers and an 800 watt linear amp.  This thing just sings with beautiful low mid range bass, it is built by Axiom Audio (Axiom and Bryston are the same company).  It has a gorgeous black ash real wood cabinet with incredible internal bracing, there are no resonances at all.... it was not inexpensive though, $5600 and unfortunately they no longer make this sub.

For you particular room, I'd look at the Axiom EP500 which is a fabulous 12 inch single driver sub and a 500 watt linear power supply (do not be misled by power ratings on subs as most rate their power with a switching supply which lacks the clean dynamic power you will be getting with low end music and a linear supply with a ton of capacitors and it will do a far nicer job).  I have one in the room and I just love it!   I also have the EP800 with dual 12 inch drivers.   All of the subs have the same amp design, just with slightly different power output based on the sub, but the exact same full range phasing controls which are a must for setting up and balancing the sound based on the room and speaker placement.

My advice due to extensive experimentation in a difficult area to properly fill with balanced sound is to go look over the subs offered by Axiom as this is their direct to consumer side vs. sold through full service dealers which is Bryston.  The Bryston speakers are the flagship items and will cost you twice as much (and the build quality reflects it), but the Axiom is priced very well for anyone looking to keep things within the reality zone and its also very top notch build quality.   Its all built in Canada, no made in China stuff here!   

That is my 5 cents worth :)

@lewinskih01;By jove, I think you have it! 18" woofers have gained favour amongst OB enthusiasts because of their higher max-SPL characteristics in comparison to smaller woofers (and 15" for the same reason). Open baffle woofer design results in lower output relative to sealed and ported---using the same basic woofer (the woofer in the OB Sub is the same as that used in the F12, only electrically optimized for OB usage.), a characteristic cited against them by opponents of OB subs.

That criticism is justified and fair, but there is a solution, one employed by both Rythmik’s Brian Ding in the OB/Dipole Sub, and by Siegfried Linkwitz in his excellent OB/dipole loudspeakers: a dipole cancellation compensation circuit, which provides electronic boosting of the signal sent the woofer(s) at 6dB/octave below 100Hz. Problem solved! Or at least mitigated: even with that circuit, an OB does not produce as much output as a sealed or ported, fed the same amount of amplifier power. You can’t have it all! To get a slight increase in SPL, the 3-woofer OB Sub is offered. And one can of course stack multiple OB subs, using a separate plate amp for each OB Sub H-frame and it’s woofers.

Speaking of subs with 18" woofers: did you notice Rythmik now offers 18" sealed and ported models? Wow! The 15" models already produce a lot of max SPL, I can’t imagine the 18". And with servo-feedback!

Does your friend with the F8’s realize he owns collector items? Brian Ding discontinued the model (and no longer has the 8" woofer manufactured for him), which was popular for mid-bass use. A lot of audiophiles think smaller woofer = "faster" bass, but Ding insists his 12", 15", and 18" woofers are just as fast as the 8". What makes a sub sound "fast" is how quickly the driver stops and returns to "rest" after the signal stops; the Rythmik servo-feedback design provides stop-on-a-dime woofer control and sound quality.

As for OB sub-to-sidewall distance: Rejoice! Due to dipole cancellation on either side of the OB Sub frame (inherent in open baffle design, as described and explained in my earlier post), you may place the OB Sub right against the wall if you wish. Or lay it on the floor---there is no output on either side of the OB frame! As long as the sub fires down the length of the room, you’re good.

As for OB Sub to front wall (behind the Sub, not the listening position) distance: as with all dipoles, a minimum of 3’ is required, more encouraged. Of course, you may try different distances to optimize direct-to-reflected phase correlation and loudspeaker/sub blending, but the continuously-variable phase control (0-180 degrees phase rotation, creating 0-to-16ms delay) makes that unnecessary. But remember: a phase control can only delay the signal, not send it back in time. ;-)

Hello kenrus,

   




     I think mike_in_nc gave you very good advice: the key is good integration with your main speakers, a pair of subs will perform much better than a single sub (smoother, faster bass, easier to integrate and provide better bass dynamics) and it's best to buy subs that offer a free in-home trial period and full refunds if you're not satisfied. I agree with this completely.
     I also agree with mattchristian that a pair of the SVS SB-1000 sealed subs are a very good choice.  You'd need to buy a pair of these subs used, however, since SVS recently discontinued this model.  I don't know your budget and goals, but if you're looking for the best bargain, I think a used pair of the older SB-1000 subs in good condition would be your best option.           
     If you prefer to buy new with a 5 yr warranty, I'd suggest checking out a pair of the SVS SB-1000 Pro subs for $499/each, or a $50 discount if you buy 2, at $950/pair. These are a newer refreshed and updated version of the discontinued SB-1000 model at the same price.  These are also very compact (roughly a 13" cube), have a 12" woofer and have a rated bass extension down to the audible limit of 20 Hz. They offer free shipping, a free 45 day in-home trial period and a full refund if you're not completely satisfied.
     If your budget is a bit higher and your goal is state of the art bass performance that will make your room seem larger, I'd suggest you consider the Audio Kinesis Swarm or Debra 4-sub distributed bass array (DBA) system for about $3,000:
https://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system
     Just a few useful things for sub installation and setup I've learned through research and experience over the years:

Two subs will perform and sound about twice as good as a single sub  and four subs will perform and sound about twice as good as two subs in virtually any room.

Humans are unable to localize (discern exactly where a sound is coming from)  with bass sounds at frequencies below about 80 Hz and are progressively better at localizing sounds as their frequencies rise above about 80 Hz.

It's very important that each sub is positioned optimally in the room, and in relation to the designated listening position, for best performance. I suggest you google and use the "sub crawl" method for easiest and optimal positioning.  

Once the subs are optimally positioned in the room, the Volume, Crossover Frequency and Phase controls need to be optimally set on each of the SVS subs or once for all 4 subs, on the supplied amp/control unit, for the Audio Kinesis DBA system.

Best wishes,
Tim

I use two HSU ULS-15 MkII subs in addition to a Revel Ultima Sub 15 all are sealed.
The  ULS15 is the only sealed sub that HSU sells and is very nice for the money.

We`re in the process of setting up two brand new SVS SB1000 Pro`s that are being used along with a sealed down firing DIY Rythmik sub that has the GR 12" driver in it for my daughter and her husband in a nicely done basement stereo room.

Plenty of power and the phone app is really nice to have ! Just sit in the listening spot and dial it all in...pretty cool