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I built a sub a couple of years ago and while it sounds great for HT stuff, it's practically not even there for music. The box is roughly 1.6 cu-ft (2 cu-ft minus speaker, amp, and bracing) and is stuffed with poly-fill. My driver is a Dayton RSS315HF-4 and my amp is the Dayton 250 W plate amp. My stereo is a relatively new Yamaha 5.1 HD receiver. I have a choice of using either LFE inputs or speaker-level inputs for the sub.
First I tried the speaker-level inputs, wiring the sub in series with my mains. Again, sounded great for HT, not much going for music. I tried fiddling with the crossover frequency and the gain and I could get some very low frequency boom (~30-40Hz), but nothing like I was expecting at usual low-end musical frequencies (45-70Hz). Since my mains are Dynacos which play well down into the mid-50s, having weak, muddled bass was a step down from what I was used to.
Next I tried hooking it up to my stereo's LFE output and setting it to decode 2-channel stereo as 5.1. Sounded about the same. I tried setting my mains to "small" thinking maybe the stereo was only sending the lowest of the lows - virtually no difference.
I don't mean to complain because for movies, the sub will knock pictures off the wall. It's just that I thought adding a sub, especially a big 400Wmax 12" sub, would really make the low end of my music come alive and it just doesn't. On most songs that are boomy on my dinky car stereo, I can barely tell it's there.
So after the very long winded introduction, what could I be doing wrong or am I just expecting my sub to do something it won't?

To determine if anything's wrong you need to measure the in-room response. You could spend big bucks on an Omnimic, or get a USB mic and freeware, or just use an SPL meter and hand plot response using a test CD or downloaded sine wave generator as a source. Once you've determined if something's broken you can proceed on fixing it.

I was planning on doing that this weekend, but I haven't gotten around to it yet. Something about a sick wife and a sick car keep getting in the way of tinkering with my speakers. However, would you agree that I should be getting some serious, noticeable "boom" when listening to music? In other words, regardless of how my sub is performing, am I at least expecting something that it SHOULD be capable of doing?

Does that plate amp have an adjustable crossover by any chance? Maybe it's set to lowpass at 40 or 50hz or something? Similarly, is there a lowpass xover point in the receiver settings?

Maybe i'm misunderstanding, but it sounds kinda like a settings issue?

"Filled with Polyfill" leads me to believe it's a sealed sub? If it was ported i might also think maybe you just have a giant hump in your box's response at lower home-theatre-special-effects region, then a flatter response in the musical range. I think that can happen with ported designs, but i don't remember if that is possible with sealed. Bill's advice about measuring equipment would sort this out.

Good luck.

You should be using the LFE output of your AVR and then the first thing I would do is check your Yamaha 5.1 HD receiver manual for a setting in the SUB/LFE output section that is a "PLUS" setting - ie that setting will allow the sub output to work with any input settings not just when using your BD player.

Most modern AVRs have a "PLUS" or similar setting to allow the sub(s) to be used with the mains for music/gaming,etc but if not enabled in your settings you won't here anything much from the sub from your music/gaming inputs if this function isn't enabled in the AVR.

Try running test tones? That will make it blatantly obvious what's going on. Maybe the variable crossover on the amplifier is messed up, try setting it in the middle, it may be wired in reverse or something silly like that, causing the highest crossover to be the lowest, etc.

I'll be po'ed if that's it, but you could be right based on what I'm seeing. You should be using the LFE output of your AVR and then the first thing I would do is check your Yamaha 5.1 HD receiver manual for a setting in the SUB/LFE output section that is a "PLUS" setting - ie that setting will allow the sub output to work with any input settings not just when using your BD player. I'll check this when I get home.

Thanks for the suggestions, guys.

Try turning off the main speakers using a Speaker A/B/Off button, for e.g., or just pulling the wires. See if your sub is doing anything at all.

Are your inputs different depending on music and movies? In other words, are you using a "CD" input and "BD/DVD" input or something? My receiver remembers decoder configuration per input, so I can have the audio input on 2-channel while the TV/Sat input is on auto format decode (5.1) with Pro Logic II upmix from 2.0. My receiver also has a display with "SW", "L", "C", "R", "SL", "SR" etc... They light up when they're active for whatever decoding mode is enabled. (Just L and R for stereo; L, R, and SW for 2.1, etc..)

This is all really basic stuff and you might be well beyond this by now, but it doesn't hurt to check. :-)

prophecy in the news

Tuesday, March 5, 2013

Re: Sub not acting right (I think) - Techtalk Speaker Building, Audio ...

Sub not acting right (I think)

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