Axiom Home Page Forums General Discussion Technical Questions two way multiple sub system

I was wondering if a two way sub system could give the best of everything below 80Hz. Here is what I mean: let a big sub with a 15 or 18 inch driver handle the stuff from 40 or 50Hz and below and let a small sub with an 8 inch driver handle the stuff from 40 or 50Hz to 80Hz. My reasoning for this is that the larger drivers can dig low down in extension and have a lot of impact, which is a nice feature for movies. But, the subs with larger drivers can sound sloppy and flabby in the 40 to 80 Hz region. But a well designed 8 inch sub can be about as quick and nimble as a sub can get in this 40 to 80Hz region and even lower in extension. The main problem with such a small driver is that it won't have much impact with lower frequency stuff.

A good example of subs that I was thinking of is two Hsu ULS15's and two Axiom ep400's or two Velodyne MiniVee's. Put the Hsu's at the midpoint's of two walls facing each other and the two 8 inch subs at the midpoint of the other two walls facing one another.

With this set up it seems like you would have a flat frequency response, in the bass region, at every seat. The bass would dig down low with a lot of impact, when necessary, and yet be very musical.

What do you guys think? I'm just brainstorming here.

A pair of M80s is as good as a pair of EP400's, IMO, and during my brief time with the Ep400 I found its sound became lost when the EP600 was playing. I am not sure if adjusting the crossover on the 600 would have helped the 400 become more pronounced by keeping the 600 out of the range the 400 would be playing, hmmmmm, interesting............

You should read this article on subwoofer myths before proceeding. There are many discussions on many audio forums discussing the "musicality" of subwoofers especially those of a smaller driver being "faster" and "tighter" and larger drivers being more "sloppy" and "flabby". This article will explain many of these misconceptions.

The sections titled #3 Subwoofers are fast / slow, #4 Ported boxes don’t sound as good as sealed, #5 Subwoofers care what they play, #8 Smaller drivers sound better than bigger drivers you might find very informative.

http://www.audiopulse.com/know-how/subwoofer-driver-guide/myths-about-subwoofers/

Another question one might ask is with such an arrangement with different subs capable of significantly different bass extension capabilities, is where do you set the volume levels? Obviously, regardless of size, they have to be balanced. You may run in to a problem with the small subs on some movies that have very loud and low bass extension that they just can't handle and overdrive them while the bigger subs handle this same bass quite easily. For me, on the surface and in this instance for the goal of obtaining a flat frequency response throughout your room, this would seem to defeat the very purpose you are trying to achieve.

I, personally, have never been a fan of these small subs anyway so my opinion tends to be skewed on the subject. I would go with four similarly capable subs or if there are budgetary constraints, replace the two small subs with one larger one along the lines you described for a total of three.

I have four subs all with at least 12 inch drivers and they handle music beautifully.

With M80's doing the bass duties below 80Hz you run into the problem of best placement for bass versus placing the M80's as the main speakers. If you have the ep400 you don't have this problem. With two ep400's placed at the midpoints of the walls facing each other the bass would be uniformly flat in every seat.

What I meant, but didn't say what that the little subs would have a low pass filter of say 40Hz and a high pass filter of 80Hz. The sub with a large driver would have a high pass filter of 40Hz.

Earl Geddes is a big proponent of this setup, but for different reasons. He feels you get the best bass response by exiting as many of the room modes as possible, so he has one larger driver to handle the sub 50Hz stuff, runs his mains full range with a natural roll off (12db per octave) around 50Hz and then supplements with 2 or 3 subs covering the 50Hz - 150/200Hz region using high efficiency drivers in a bandpass config.

The trouble with using multiple subs in different frequency ranges is that they can be difficult to integrate. Realistically, a couple of good subs with larger drivers placed properly will get you good clean bass with decent headroom for dynamics.

Nick, your premise about the bigger sub sounding "sloppy" higher up compared with a smaller sub doesn't really have factual support. As the info linked by Dr. Horse indicates, subs operate at very low frequencies which are inherently "slow". Forget about those frequencies being "quick", "tight", "musical" or similar qualities. Set your sub for a crossover around 60Hz and listen to some bass-heavy music with the other speakers disconnected to get an idea of what the bass alone really sounds like. Any "quickness" in the sound from a bass instrument is due to the upper harmonics which the speakers, not the sub, play.

Once this little surge exercise is done or I get enough time during it, Sean and I are already planning a subwoofer GTG so we can check out Charles’ AS-EQ1 on two identical and two dissimilar subs at the same time. Should be simple enough to just to reconfigure settings and test out your idea on his two small subs doing the midbass and my EP500 handling the low bass.

If there is anything specific you would like us to try let us know.

Cheers,
Dean

This isn't factual support. But, many people around here have mentioned how when they run their m80's or m60's as large speakers with the sub off that the bass just seems quicker, tighter and more well defined. Many of those guys have Axiom subs. Granted, running no sub will not have as much low end extension as running a sub.

There are even some reviewers that always run their systems sub-less and mention the reason that they do this is for more musical well defined bass.

I'm more of a movie guy, in my home theater system. So I'm not going to run sub-less, even with a good set of tower speakers. I know that there is plenty of mis-information floating around, just look at the audiophile esoteric crowd on nearly anything audio related. I'm just trying to understand what is going on here.

Most likely due to the fact the lower notes overshadow the higher frequencies, making it harder to hear the mid - upper bass range, especially if the room is sucking out some midbass etc. all the while emphasizing a lower range.


For the samre reason I noted above.

This can be perceived for a variety of reasons and it has nothing to do with the smaller bass drivers being tighter and more well defined.

1) A poorly designed subwoofer.
2) A well designed subwoofer that is not properly calibrated or running "hot".
3) Improper crossover integration between the subwoofer and the main speakers when set to small.
4) Placement issues. Some have found this "boomy", "flabby" characteristic to occur from corner loading a sub for example.

Here is another article on this topic that you might find interesting as well. It is from Alan Lofft of Axiom audio.

http://www.axiomaudio.com/tightbass.html

Wow, there has been a lot of good information from all to help me clear this up. Alan's article hit the nail on the head with this issue and I am completely convinced. The first link was also very good, but quite technical. The "flabby", "loose" bass myth is almost as bad as the need for ultra expensive cables (speaker cable, HDMI, etc.) myth. It seems that to choose the correct sub you just have to narrow it down to good sub companies like: Axiom, Hsu, Outlaw, SVS, etc. Once you settle on the brand just make sure that you choose one (or preferably two) large enough to fill your listening area. That's it.

Jay hit the nail on the head for why I’ve preferred my M80s alone for music just look at the before curve:

http://www.axiomaudio.com/boards/ubbthreads.php?ubb=showflat&Number=307389&fpart=1

Even though the curve for the M80s is going to be no better, w/o the big low bass hump overpowering everything else the M80 come out sounding “tighter” and “clearer.” It’s also why I’ve often run my M80s using “double bass” or “LFE + Mains” to get some smoothing from having multiple bass sources even though they are not optimally placed for that purpose.

I'll wager that at least half of those that find the bass from their mains 'quicker' do so because someeone told them they should.

The other half probably benefit from in room placement of the mains giving them better upper bass than wherever they put the sub.

The other reason one might have 'slow' bass from a sub is if the driver is marginal and has been optimized for bottom end performance at the sacrifice of upper end dynamics.

I have modeled a 10" driver where I could get good output down to 17Hz, but the trade off was that the driver started to roll off noticably above 80 Hz. Changing the tuning so that the low end roll off was at 25Hz restored the top end.

On the other hand, if you use a monster driver like the Exodos Mal-X 18 you have enough excursion for sub 15Hz performance, but have enough power handling and a well enough designed driver that you do not loose anything at the top end.

I think that this is why Axioms subs sound so good with music. Nothing is sacrificed in the upper bass to get more low end distortion.

If you are really curious about stuff like this, go over to avsforum.com and search the DIY speakers & subs forum for user Mark Seaton. He has made a number of excellent posts where he talks about sub desing and tradeoffs.

Yes, Doc; thanks for linking Alan's excellent article which covers these points very well. Ian's observation about how a sub crossed over higher might sound "tighter" simply because it was playing "tighter" higher frequencies was quite interesting.

He has a small company that makes Seaton Submersive subs that he designed right. Everybody talks about them and how great they are, but you can't find much info, like pictures, frequency response, etc. I know that they are supposed to have dual opposing 15" drivers in a box and that's about it.

IIRC, Seton was regarded as THE man for subs by those on av123 and I beleive he is/was helping Craig with some stuff at TCA.

Mark Seaton has cut ties with AV123 as well as TCA from what I understand. He doesn't develop any products for AV123 anymore and never developed anything for TCA. He has his own company of course which is pushing out product.

I knew I had read that Mark was going to be involved, look up the Sasquatch 18? thread...........

Never mind

http://www.tweakcityaudio.com/forum/showthread.php?t=71

I don't think that product even exists under the name Sasquatch. From what I understand he has no business relationships with AV123 nor TCA any longer. Mark Seaton has never developed a product for TCA that has been brought to market. He has developed the MFW-15 for AV123 and some other designs that were in progress that he has dropped from ever making it to market for AV123.

Whatever, the guy knows his stuff.

As wacked as threads get on AVS at times, some very knowledgeable people post there. Tom Danley did a lot of posting around tapped horn sub design. The guy behind TC Sounds also posts there at times as does Earl Geddes.

He might not have any relationship any longer (or ever from reading the rest of the thread)with TCA, but he was going to and his name was mentioned way back in the early days at TCA.

I wonder if the amp fiasco of the MFW forced him to cool his relationship with some in the business, not that the amp was his fault, but just the fact his name was so highly touted with that subs development and his name is his brand.

Remember, the owner and president of AV123 was indicted by grand jury and other matters that would make one want to cool business relationships.

I do remember and I would pull out from associating with that company as well, actually I did. I have stopped subscribing to email notifications from them.

Regardless of his present affiliations he was associated with them and with whom one associates with tell more about a person than anything else. That’s why you focus on a persons associations when doing background investigations. Caveat emptor!

Definitely. Can't argue with you there.

Sort of. Would you say everyone who ever chose to be associated with or do business with GM is a looser because GM lost its way and went bust? Not likely.

We all pick loosers sometimes. A number of people got sucked in by the owner of AV123 and it cost them all money. Its a small industry and Mr. Seaton is well regarded by those in it, at least the ones I know of.

Anyway, this is going way off topic. You can choose to ignore what Mr. Seaton writes, or not.

GM is a large corporation AV123 is a small company that was/is fronted by one man. Knowing the character of a group and an individual are very different things. So the comparison is invalid.



The issue about AV123 and it’s associates (Seaton, Craigsub, Ninja, Emo et. al.) for me isn’t that “we all pick loosers” but rather why people pick their associations. AV123 stank to high heaven for years. That people were either to naïve or willing for reasons of expedience to overlook it’s nature are salient if choosing to enter a business relationship with them. Those in the former category are IMO to naïve to run their own business effectively. Those in that latter are not to be trusted to do business with in the long run.

95% of all people can’t hide deceit which is why most professional poker players wear sunglass, hats etc. . . . Almost all people from an early age can pick up on these “tells.” Why people either don’t see them or choose to ignore them is very informative about a person in the situation in question. (note: I’m a trained interrogator, and very good at it). I really know about these things, which is why I give no quarter to deceitful people or those who associate with them.



None of the above invalidates Seaton’s knowledge or experience. To ignore him or others having specialized knowledge or experience simply because they have associated with AV123 is silly it simply means as I said above, “Caveat Emptor.”