why am I getting weak sub output?

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Need some help here fellas. Am doing trial run of just completed DIY sub: 122L box (original design for 15 inch original tempest) with 15 in dvc dayton driver, using 240W dayton plate amp. Hooked up receiver via sub preout to plate amp low level input. I hear and feel some bass but have to turn the plate amp gain all the way up to have a so-so bass thump (though it is tight). Checked the box--no leaks. Think the amp to driver connection is right: positive to positive of each "red" coil and negative to each "black" coil (parallel wiring). Changing the plate amp crossover does nothing (note my receiver does have low pass filter as does plate amp but I have heard keeping the plate amp's crossover turned all the way up to 160Hz should solve any problems. I have not tried my receiver's automatic MCACC set up for surround sound--could this have an effect?
Any ideas why I'm getting basically low volume would be greatly appreciated
M
 
Is the cone moving at all? What is your idea of "weak?"

My guess is that there isn't enough gain. So you need to trace through the signal chain and find all the possibilities, starting with the CD or DVD - does it have bass? Then moving to the receiver, check all the settings including sub volume. Disable bass management or check crossover point. If none of this works then try driving the plate amp from "speaker level" or "high level" outputs.
 
Thanks for the quick replies
1. My receiver is set up for surround sound-but I notice the same weak sub output with 2 channel use, so maybe my receiver allows sub output with 2 channel (pioneer 1014)
2. The cone is moving a little but not a great deal. "weak" meaning my 8 inch fostex are putting out more bass than my 15 in. sub. But I do have several settings that might be affecting output including:
A. I have front speakers on large setting (vs small)
B. I do have "yes" on sub output line vs "no"
So those are good ideas to check next. I did call Parts Express tech help and was told that the vast majority of poor sub output is due to the settings on the receivers nowadays; also said that the 240 W plate amp should "rock" the room on that particular driver. He recommended set the front speakers to "small" and not use the automatic set up feature.

M
 
Setting your fronts to large and your processor to 2 channel will send no bass to the sub.

The 'usual' way to integrate a sub into a surround setup is to set all speakers to small, with the crossover on the receiver set to ~80Hz. This will redirect the low bass from all speakers to your sub.

Cheers,

Rob.
 
With your current setup, only the LFE track will be sent to the sub when present. You should either set the mains to small (recommended, why run these drivers fullrange?), or you could set sub to the 'pls' setting (thats what its called on my pioneer, may be different on yours) which sends bass both to the mains AND the sub.
 
This site has so many helpful members...thanks again.
One reason I set the front speakers to "large" is based on some literature I got on bass management from the polk community. I'll find the exact download if anyones interested. It stated that setting the fronts to large (IF your fronts can produce decent bass that is) while using the sub allows better integration among speakers--presumably b/c you're getting some bass notes dispersed around the room. But alas for me that didn't work and I'll try the recommendations. Will let you know--thanks again
M
 
Mark, do you realise you sent 3 identical posts?

Setting speakers to small may help with small vented speakers in particular in protecting them, but may not provide the integration you want. If it's only a first order rolloff, then that's not likely to cross to the subs correctly.

I tend to think that you won't get it right unless you use something more powerful such as an active crossover properly designed for the speakers in mind.

Based on what you have said, its clearly not getting enough gain. Have you got it to work yet? I suggest again using speaker outputs - if nothing else works, then that should. But try the other suggestions first.
 
I have to agree that most HT speakers are best set to small and let the sub do the low stuff.

You still haven't mentioned anything about subwoofer level adjustments in the Receiver. There should be a setting with adjustments in dB for all the speakers as well as the sub. This is normally done with the test tone. Some Receivers have another LFE adjustment as well as this.

Check also that you don't have dynamic range compression on to suit late night listening or some other option.

Get the manual out and have a good read.

You don't say what you are using as a source and how it's connected. If it's a DVD with on board processing, then bass management is done within the player with 5.1 coming into the Receiver via RCA leads.

I use a PE 250W amp and it's got plenty of grunt in conjuction with Peerless 10"XLS.
 
I once returned a second-hand 450w PA amp as faulty and only later discovered when I bought my new Behringer 2400w beast that the cables had some loose in one of my subs! :xeye: :smash:

Moral of the story: check your wiring, that everything is firmly connected and that VCs are correctly wired - both of them! Not that I think this is what it is, but its something to check. I felt like a twit when I found this out! :xeye:
 
From what I've gathered so far, since you mentioned using the MCACC feature, I take it you have a Pioneer (Elite) receiver. As you may know, MCACC does not adjust any kind of equalization for the LFE channel, only the output level.

From what you're saying, it sounds to me like you DO have the Dayton sub's voice coils wired wrong internally. I would double check the wiring and make sure you have them properly wired in parallel in phase.
 
I was going to suggest double checking the wiring on the sub too Chops. I've wired speakers with the polarity wrong before and sat there thinking wheres the bass when the cones are going crazy:D


The other thing to check is the speaker level settings - if the receiver has boosted the mains 10 / 12dB then maybe the sub out isn't giving enough level.

To check that the sub and amp are working properly you can set mains to large and conect the main L or R preout to the sub. If theres still no bass then the amp/driver needs more checking. If it works its something in the receiver settings.

Also make sure the dvd player is set to output digital (sometimes called bitstream) and that the recever indicates its playing dolby digital / dts too. (and that the digital out is connected to the receiver too)


Rob.
 
I'm getting some decent bass now! Took the advice of all who recommended using the high level inputs and parallel wired the sub from the front speakers. Still shocking to me that just this change would work--why in the world do we have a sub preout line? I'll tell you the bass mgmt on the pioneer 1014 (it's not the Elite model) is not straight forward and I suspect many "home theater" receivers are similar. I tried all the variations mentioned on these posts but nothing really worked until I just didn't use the preout. However, I did not try adjusting the other speakers around the sub. I do think I'll be able to tweek the sub output by decreasing the other speakers' dB. Of course, I'm (also the wife) getting kind of tired of running the wires through the living room. Appreciate all the good feedback I got from everyone here. Happy Holidays!
Mark
 
Hey all,

This is some really great information. I had the same trouble on a Yahama reciever I bought years ago. It was easy to get into the sub out "volume" level but not much signal. Maybe the preamp is not happy. I did, however apply a car stereo sub crossover between the reciever and my amp, and it helped but not so good. I, like the other guy, later found out that it took a large signal to drive a Crown CE1000. I later built an amp but haven't had the chance to test it with the Yamaha reciever. I know it has a pretty sensetive input because it tests great on the bench, with normal input devices. All the info about setting the fronts to large and small settings is very interesting and helpful, so, thanks for discussing it!!! :D

Best wishes,

Chris
 
Pinkmouse--Thought it would be too shocking to go straight to just one post after somehow repeating the post 3x. Really, believe me, I'm not trying to emphasize my posts :)

Diode--absolutely this is a great website. Have found many helpful people and got the encouragement to DIY all my speakers. Now might venture into the SI t-amp arena a bit. You would think hifi manufacturers scout these posts b/c we certainly pick up on the problems in equipment --whether the hardware or just the "user unfriendliness".

Rob and the rest of the gang--the movies are sounding great; actually better with movies than with some music; perhaps b/c movies contain a higher average of "deep" tones (depending on what you listen to). However, I have a 5.1 system set up and will be building two more speakers to try the "THX" feature on my receiver and am not sure how that will work. Do you know if using the THX feature that the sub should be linked via the sub preout? Of course, THX can certainly be overrated. Just want to see if I can hear any difference (boy that's using a lot of senses).

Mark
 
In a previous life, when electronics was still developed here in the US, I worked with electrical engineers and the management staff. NO! they don't look on things like this site as they don't see any flaws in their design. Once they make a "final" decision, on anything, it is set in stone. The corperate attitude really SUCKS in this way, because so many great ideas could come back from the customers, and great products could come out, but the bad attitude of the engineers and management prevent this. With today's digital technology, all that would have to be done is new code written.... big deal, right? Well again, with the attitudes involved, it IS a huge, big deal. Quite sad in my honest opinion but that's the lay of the land, I guess. I still tinker with electronics but have since changed careers to aircraft mechanic. It's a cool field too! Glad you got it all ironed out!

Chris
 
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