Axiom Home Page Forums General Discussion Stereo selecting a stereo sub with my M80's

Well, I’ve had my M80’s for about two weeks now, and for the most part, I'm pretty happy with them. I'm quite certain that for $1100, I can't find anything that sounds as good as these speakers do.

I could use some educating from y’all regarding sub woofers. I am not an audiophile or anything remotely close to it. I’m learning from scratch here, so please bear with my ignorance. I posted this question at Audioholics, but didn't get much help there. I'm beginning to think the audience over there is bored with my questions.

I’m driving the speakers with a Harmon Kardon 7200 in stereo mode only. I have them set up on the ‘second zone’ with independent remote, which is actually the 6 and 7th channels for the surround back. The speakers sound great with plenty of base, mids and highs, and will play louder than I can stand. But at lower volumes, something just seems to be lacking. I can’t resist the urge to turn up the volume, which is counter productive to conversations when I have guests over. I was trying to avoid using a sub due to the room lay out, but now I’m thinking that a sub would help fill the room with some light background sound when I have parties where folks actually want to communicate with each other. I started a string here a few weeks ago that has my room specifics.

I am looking for suggestions / input in regards to running a stereo sub woofer in this space with the M80’s. I don’t know squat about subs, what types there are, how they are hooked up, powered, where to put them, etc…. Some specific questions I have are, do I need a separate amp to run one under the multi room function through the pre-outs, or can I still use the surround back amps to power the speakers and a sub woofer both? It would seem a shame to not be able to take advantage of the HK’s power. Do some subs sound better with music than HT? Does size really matter? Any input would be appreciated.

……..mike

Hello mdrew,

The urge to turn up the M80s is natural because of a characteristic of human hearing. At low volume our ears are quite insensitive to deep bass frequencies, an effect scientifically documented in the Fletcher-Munson curves. Anyway, for some years many receivers and preamps included a "loudness" control, separate from the volume control, which compensated for this trait of human hearing. You would pre-set the volume to your usual loud level, then turn down the loudness control, which automatically increased bass boost the more you turned it down to compensate for our insensitivity to bass at low listening levels. Some Yamaha gear may still include a Loudness control. You can compensate easily by simply boosting the bass to your M80ti's on your H/K 7200 at low volume.

No, you don't need an extra amplifier to run a sub. Virtually all subs are "active" and contain their own built-in power amp. You would connect your Zone 2 speaker cables to the speaker level inputs on the sub, which extract the deep bass, then pass on the signals with a second set of cables to your M80ti's. But the same phenomenon still operates. At low volume, you will want to turn up the sub volume to compensate for your hearing of deep bass.

Yes, physics always dictates sub limits: the larger the box and the driver diameter (they go hand in hand), the deeper the bass frequencies and the greater the output. The larger the room, the bigger the sub you need. It's a pressure pump and does not care where you sit. It must pressurize the room volume it "sees", so larger rooms need a larger sub (or two).

This explanation overlooks many aspects of sub design, but the basics are covered.

Regards,

Thanks Alan. That’s some interesting reading. So, from what you tell me, even with a sub I’ll still feel the urge to crank up the volume. But what do you think about my idea of adding a sub in this room? Will it help fill the room at the lower volume levels?

Unfortunately, in the mult-room configuration, the receiver does nothing more than pass the stereo signal through to the speakers. I can not manipulate the bass and treble controls, or balance either. The only think I can change is the volume. I can’t use any of the H/K’s surround processes either. I’m pretty disappointed about that. If I would have known, I most likely would have bought something different.

Who makes a good, less than $1000 sub that would match up with the 80’s? One big enough for this room? Are the Axiom subs any good? Are there any other nifty electronic gizmos out that would give me some control over the bass/treble signals between the receiver and speakers? What about round vrs box, any difference?

Well, I'll start with the obvious. In that price range SVS makes good cylinder subs, and equally good box subs.

So does HSU like the VTF-3 MKII

There are other good subs including the Axiom subs. These are the places to start looking.

mdrew, check out the SVS or the HSU... They do have some kick butt bass. I must warn you though the auto on function does not really work good at low level. You have to turn the gain of the sub pretty high before it will kick on at low level. With the gain set at high, the bass becomes overpowering. You just have to experiment with it. With my experience I always turned the volume loud enough to wake up the sub then I turned the volume down to the desired low level listening.

Actually the best bet is to get a Radio Shack SPL meter and calibrate your speakers... I'm pretty sure there will be more knowledgeable people other than Alan that will chime in to assist you. Good luck!

I have an SVS 20-39 PC+ and with the gain on the sub approximately 1/3 of the way up, the setting on the receiver at -2 (rcvr goes to +10) and the auto on switch on AUTO, I have bass regardless of the volume level.

It is right in a walkway to my bedroom and so I usually put a hand on it as I pass by just to feel it work...even when the volume is very low, it is still is doing its job...supplying impressive bass.

WhatFurrer

A good choice for a sub for music would be the Outlaw LFM-1. You can get a pair of them for $999 not including shipping.

Wid posted a link in this thread a few days ago to a nice write up on using a pair of subs for stereo.

I have an LFM-1 and it produces nice tight bass. Wish I had the cash at the time I bought it to have gone for the pair.

WhatFurrer, it's probably just my setup. I remember not having any problem with the Paradigm sub and Pioneer receiver. SVS even suggested to use both input which I did and it didn't help. I still like my SVS though...:)

Hello Mdrew,

Hope you are well. Instead of hooking speaker cables up to the new sub, use the pre-outs that the H/K 7200 has for the channels for the Zone 2. Always cleaner to use the pre-outs.

As far as tone controls you could stick a good equalizer in-line with the sub. That only solves the bass control though. To get treble control would be harder, you would have to hook a 2 channel amp to the line outs of the subwoofer, then hook your speakers to the new amp. All tone control would utilize the EQ and would be passed along to the mains through the subs line-outs via the new 2 channel amp. Probably a heck of a lot cheaper to get a 2 channel amp and pre-amp on ebay, than this elaborate work around though, hehe.

If you just want bass control, and can live without treble control, try to get a subwoofer with a built in parametric EQ. Lot less equipment to buy with this option. The SVS PC-Ultra has built in parametric EQ, it is $1,149 + shipping, and they don't get much better.

Later,

TonyM

TonyM,

I hope you are indeed well! Thanks for the other suggestion to Mdrew, about using the pre-outs for the 2nd zone. (My face is red.) I have an H/K as well but I don't use the Zone 2, nor have I looked at the back panel lately. Good alternative, although I don't like the idea of running long coax lines with low-level signals to other rooms.

And yes, I agree with you on it being simpler to just get a separate amp/receiver on ebay for the second room. I often suggest that to customers who get all fired up about doing whole-house multi-room installations . . ..

By the way, Mdrew, according to a syndicated A/V columnist who loved our Axiom M22ti's, M2i's and M80s, he reported to me that the cheapo Panasonic digital receiver ($200?) will drive our 4-ohm M80ti's with no hassles. I'm dubious, I've never heard the Panasonic, and I'm not endorsing it, but he says it works just fine with the M80s.

Regards,