Axiom Home Page Forums General Discussion Home Theater Do I need 2 channels to run 2 subs?

I am going to go to a dual sub setup in my new theater. I was just told that adding a "Y" adapter is all I need to do as the subs are self powered. Is there any benefit to upgrading the receiver to a multi channel sub output or is this "Y" adapter just as good?

The advantage of multi-output (on some receivers) is the ability to set level and distance independently. If you have two subs placed at very different distance from your mains, it might be worth it, at lest in the long run. How much is it necessary right now (or even ever), I don't know, but I guess it depends a lot on positionning and if the subs are from different models or brands.
Subs experts are bound to join in soon on this topic!

A Y adapter will suffice, you have to set up the subs so that they are both calibrated to the same level or slightly lower than the speakers, as the dual subs have more over all output, about 3db for subs in different places within the room and if co-located about 6db more. Once you have them calibated, you can run Audyysey and it should help smooth things out even more.

Having a receiver that has dual sub outputs AND is capable of adjusting each subs output independently is obviously more advantagous as the receiver will make the required adjustments for you on each sub, but not all receivers have this ability yet.

The others pretty much summed things up. If you can find a receiver that has multiple Sub Preouts, that have independent settings good luck and pull out the $$$$$. The last time I looked, only the top of the line Denon's and a few other had independant multiple sub out jacks and would allow you to set each sub seperately.

I have found that if you calibrate each sub, one by one, then turn them both on you will get good results. Distance (delay) is always fun, especially when one sub has a DSP chip.

Total tangent, but speaking of DSP chips, do you think Axiom will ever offer speakers with their own amps and DSP chips? It just seems that if they're using a DSP to flatten the frequency response of their subs as much as possible, they'd be tempted to do the same with their other speakers. I know other manufacturers offer powered speakers, but who out there is actually using DSPs for something other than their subwoofers? Just curious.

The DSP depends upon knowing how the speaker is going to behave, shaping the output of the amp to take that predicted behavior and make the actual response flat. The problem is that much above 100 Hz, and there becomes too many variables, happening too fast, that it's impossible to flatten the response of the speaker with the same level of accuracy which is possible with a much slower moving target.

If you think about it, the room correction software in modern receivers is attempting to accomplish the same thing--with the added variable of room response thrown in. You see what a mixed bag that is.

Additional: Although I would love to see Axiom make affordable mono-block amps targeted at their own speakers. Maybe with a mounting system to which directly attach them in a safe and secure manor. So you run a power cord and an RCA or XLR connection over to each one.

I didn't think the DSP chip was meant to 'flatten' bass response, I thought the whole idea was to keep the amp from distorting... or is that the same thing?

I always thought it was more of a safety feature from damaging the speaker than it was a tool to help its actual musical performance.

Impossible for how many more years? How fast does the processing power of DSPs increase, and how much processing power is needed to take care of the audible range? Those would be interesting figures to know. And as far as room correction software goes, you'd think that SOMEONE out there offering multi-thousand dollar equipment would be able to include enough processing power. I keep dreaming, anyway.

That sounds like a nice idea, and affordable would be appreciated. I managed to spring for the A1400-8 at the preorder price, but if I want to try out the newer sound modes at some point with the extra channels, it would be nice to mate it with another Axiom amp that uses the same technology. I'd love to have an A1400-2 for my mains, but it's hard to justify the price.

I think it accomplishes both. From the EP800 product page:



It sounds like it definitely works at keeping the output even at every frequency.

Wow, well I read that sentence dozens of times, but only that time did I read it the way you interpreted it. That changes my whole outlook on the EP800, I always thought the DSP chip made sure that the speaker never flexed beyond it's capabilities no matter how much juice was feeding it. But now that I realize it's more of a system to keep bass response 'flat', then I guess that doesn't mean I can't push it beyond it's physical limits then eh?

So all those times it sounded like it was 'bottoming out', I figured there was no way I could bottom out a speaker with a DSP running things. Turns out, I probably was bottoming the thing out all along. That's going to take a few minutes to sink in.

Maybe it was your 80's set to large.

Aaron, there aren't any receivers that actually have two separate sub channels. There's one channel which may send the same source material through two outputs. As was said, in most units the two outputs aren't separately adjustable for different level and distance, although a few of the most expensive ones do have that feature. So yes, unless you get a unit with separate adjustments(which may or may not be needed)a "Y" arrangement is all that's needed.

Setting your mains to 'large' will cause subwoofers to bottom out? Is that right? What causes that in a LFE+Mains configuration? I didn't think that setting affected what was sent to the subwoofer, just that it also sent the low frequencies to the mains as well. That was my understanding of the way it worked.

If for some reason LFE+Mains sends extra frequencies to the subwoofer, causing it to bottom out, then perhaps there's our answer. But I don't understand how it would do that?

Micah, there're three different situations: if the mains are set "small" their low bass goes only to the sub; if the mains are set "large" they alone play their low bass; if the mains are set "large" and the sub is set "LFE plus mains" both the mains and the sub play the low bass in the mains channel.

I don't know what a dsp chip would do for a speaker. I suppose you could use it to further smooth response, but if you wanted to spend more $ on electronics for signal processing I think it would make more sense to go to active crossovers so that you can tweek the speakers to play flat in your room.

Here is a reference guide to fall back on.

http://www.audioholics.com/tweaks/get-good-bass/subwoofer-connection-guide

That is how I understood it too work as well. So how does playing the M80's in a large configuration cause the EP800 to bottom out though? If they aren't recieving any more or less than if the M80's were set to small, then I'm not quite getting something?

Thanks btw John.

I believe what Randy is suggesting is that your M80s were bottoming out not your subwoofer.

While not exactly cheap at $1400 and up, my Onkyo 3007 has separate adjustments for each subwoofer pre-out. Both distance and level can be set manually. I also believe but don’t know for sure that it calculates separate Audyssey curves for each. At least on the initial setup it pings both of them separately. AFAIK the 1007 also does this at about $1200 and up. They are however both processing the same signal as stated above.

I imagine Denon’s less expensive models will also be doing this soon if not already.

The advantage this give me is being able to now change the trim settings on my Buttkicker w/o getting my Butt up and walking over to the amp which when it to five times to get it right would kick my lazy Butt.

$1400 for the 3007!!!! .........you suck!!!! It is ~$2600 up here, same goes for the Denon 4310

I bet the best I could do on Boxing day (our Black Friday) would be $1900-2000.

Ahhh... well if you're right about that, then all I have to say is this.... negative. I ruled that possibility out almost immediatelly. I disconnected every speaker except the EP800 and ran the 'Cave' scene among other extreme LFE movie sequences and the EP800 was 100% the culprit. And let me also say that I've never heard the M80's bottom out. I can't speak for how well they perform with a reciever pushing them because when I had the Denon hooked up to them I never went past zero on the volume knob, because they started to sound strained.

But I can say that with the Emotiva supplying the full 400 watts that they're rated to handle, I can not bottom them out. And I've pushed them, trust me. Those things are the real poop!

So explain to me why some products cost so much up there compared to here? You’re not really all that more socialist than we are.

Based on your descriptions of what you were hearing I didn’t think it was your problem. Randy just doesn’t like it when we run our M80s large, or w/really low crossovers.

Not enough competition to keep the price down. You can only buy the 3007 around Calgary from a couple of places in the retail market or go with some of the HT companies and get charged even more!

Oh Dean, have you been hitting the garlic again?




Lol

Knoblauch wird durch die Luftwaffe verboten.

Well at least that kind is. 7 years 2 months and (runs out of fingers) 14 days, not that I’m counting. With my luck, by then the lefties will have brought us national healthcare and the righties will use it as an excuse test everyone. I can’t count the number of times I’ve warned my lefty friends to be careful what they wish for.

Garlic related (the real kind), I freaked out a cashier at the grocery store the other day when I bought over a kilo of garlic. She looked at me quizzically so I looked around as if to check who was watching, then leaned forward and said “Vampires! Avondale’s crawling with them.” I love freaking people out.

I just remembered one pre/pro which has separate sub-woofer outputs. Its feature-set is a little dated now, but the Theta Digital, Casablanca III can have up to 12 outputs, mapped from any number of input channels, with individually set crossover points. So you could take the left input and send >80 Hz to one output, and then the <80 Hz also of the left input to a separate out. It can have front/rear subs, or left/right very easily.

That is one seriously cool piece of equipment.

You sound like me talking to Eric.

Yes, I am a pretty cool piece of equipment!

I've been called a Tool.


Is that the same thing??

Me foo!

I have some equipment that's pretty cool to play with!

Yeah, but I play with my equipment more.

Back in the day I was trying to figure out how to come up with $12k, because I thought I needed a Theta Digital setup. This was before HDMI was a required technology. I was so close to buying their $3500 DVD player, but at the last minute I found they didn't design it, but it was instead a Pioneer with some upgraded components. So I ended up saving $2500 and buying the region-free modded player I still have in my sig.

Theta has still held a fascination to me. They skirt the line between snake oil, and making use of every possible minuscule audio improving technology. They'll talk about Litz wire, skin effect, and fully differential designs in one breath, but tell customers to not use aftermarket power cables (unless they are UL rated and can safely deliver 15 amps), or conditioners because they more than likely will current-limit.

They were actually bought by ATI at one point. Here's a quick blog post which sums up their situation as of February 2009: http://pqltd.blogspot.com/2009/02/rip-theta-digital.html Unfortunately, nothing had changed by the July update, and still nothing has changed today. They're promising a Blu-ray player for Q4 2009 (that's now), which has a feature set, and back panel which looks suspiciously like the Oppo BDP-83. And their HDMI input to their pre/pro is still being held off until Q1 2010.

While a one-box receiver setup is one way to go, I'm not sure if it would be better or cheaper than a separate subwoofer EQ system like the SMS-1 or that newfangled SVS thing, or even a BFD.

One thing about the Y-adapter scenario is that it will drop the voltage sent to each subwoofer, which may or may not be an issue relative to auto-power-on-sensing.

In the last few years, the integration of the consumer electronics industry has been quite profound. In addition to buying Theta Digital and essentially shutting it down, if you weren't already aware, for quite some time now ATI has been making most of the power amps for "Outlaw". It makes you wonder what their marketing plan is since I don't see their own product available to any degree and even when it was it was highly overpriced.