Table Tuba build!!

[digital_chris]

Alright, that makes sense. Now, is there any way I can test to see if there are any unwanted frequencies coming out of my sub?

[Bill Fitzmaurice]

see if there are any unwanted frequencies coming out of my sub?

I think that's obvious with the problems you've been having. I'd go back to the 60Hz crossover.

[digital_chris]

So, what you're saying out of all this is that if I had absolutely no tones above 80hz or so coming out of my sub, I should not be able to locate the bass regardless of placement?

[SeisTres]

So, what you're saying out of all this is that if I had absolutely no tones above 80hz or so coming out of my sub, I should not be able to locate the bass regardless of placement?

pretty much.

[Bill Fitzmaurice]

So, what you're saying out of all this is that if I had absolutely no tones above 80hz or so coming out of my sub, I should not be able to locate the bass regardless of placement?

That's why they're called non-directional frequencies.

[matt996]

Regarding the access cover, is it possible that you're getting some sort of distortion harmonics from the open rear chamber when you're driving it really hard? These would normally get filtered out by the horn folds, but could be free to exit the back chamber -- and your floor appears to be hard and reflective... maybe you could temporarily clamp a cover onto it just to see if that helps.

On another note when my TT drivers arrived last week I hooked up my Foster amp and was playing some tones to check for any problems. Even when I set the cutoff freq to 80 Hz on the plate amp, I could still hear higher frequency content getting through the plate amp's filter when tried a full range music signal. I was expecting that I should only hear the "muddy" LF content, but I could still make out guitars and vocals etc. Given the sensitivity of the horn, maybe you need go the REW+DSP1124 or miniDSP route to really dial in your bass filters once and for all. Even if you can't solve your problem, a proper parametric EQ and steep filters can't hurt.

[digital_chris]

Given the sensitivity of the horn, maybe you need go the REW+DSP1124 or miniDSP route to really dial in your bass filters once and for all. Even if you can't solve your problem, a proper parametric EQ and steep filters can't hurt.

I'm quite new to this kind of tuning. I kind of know where to start but still quite a bit unsure. I do have a Macbook Pro along with an R-Shack meter, am I on the right track here?

Would I be able to record what's coming out of the horn with REW and my meter and then do a graph similiar to the waterfall graphs people do for LF content so I can see what frequencies are coming out of the sub?

Sorry for being the new guy with this, I haven't read to much into calibration yet.

[Bill Fitzmaurice]

Another good reason to measure response is to be sure you aren't simple running the sub too hot. Many newbies do just that, thinking that they should really hear the sub all the time. With most sources if you're aware that you have a sub it's too loud. It should only be obvious that you have a sub by its absence when you turn it off, or by its presence with high LFE content in movies.

[digital_chris]

If I take decibel readings with the current settings, I get the same volume output from the sub as I do with the mains. Could I still be running my sub too hot? It does seem like it's louder than it should be sometimes but why if the output is the same as the fronts?

Another note. Once I setup my speakers with Audyssey, I had to turn my amp volume almost all the way off so that Audyssey would set my subwoofer level to 0db or neutral. Would it make any difference if I turned the gain on the sub amp up and the receivers subwoofer level down?

[NCDaveD]

Chris, I set up Audyssey on my Onkyo per the directions listed on the AVS forum which amounted to setting my Dayton 240amp gain at about 25 to 30%. When I checked the numbers in Onkyo Setup, it had set the LFE channel to -12db. I did a lot of experimenting with both Dayton amp gain and Onkyo Speaker Setup Level Settings of the LFE channel and ended up with my Dayton amp gain around 30% and Audyssey LFE Level Setting at -7.5db. Crossover frequency on Onkyo amp is 80Hz and on Dayton amp is a hair under 25% of knob rotation (not sure what frequency that equates to).

Changing the LFE Level Setting in Audyssey .5db at a time makes very subtle changes. Changing the amp settings on the Dayton makes HUGE changes....at least it did for me. It was VERY easy for me to get the LFE channel for the TT too hot.

I did add the FMOD 30hz highpass filters, but agree w/what others have said in that the frequency rolloff is not steep enough to catch ALL the sub30hz signal. On some movies, I do get some heavy distortion when they hit me with heavy sub30hz content.

NCDaveD

[matt996]

Would I be able to record what's coming out of the horn with REW and my meter and then do a graph similiar to the waterfall graphs people do for LF content so I can see what frequencies are coming out of the sub?

I'm pretty sure that REW does exactly this, after you connect your SPL meter to your laptop's line-in and go through the calibration. Keep in mind the Radio Shack meter itself does not have a flat response down in the bass frequencies, so you have to compensate for the meter to correctly set your sub's level.

There is a Mac version of REW, and I believe the only thing you won't be able to do from the Mac is have it automatically set the filters for you on the FBD- you'll have to enter them manually... I'm no expert myself having not even built my sub yet, so this is just from my own reading on the topic. I'm sure other folks here have far more knowledge on this.

Lots more info here:
http://www.hometheatershack.com/forums/ ... -read.html

[digital_chris]

Thank you guys for all of your help, In the near future I will try to set up REW and see what this amp is letting by, but. for now, I added a 30hz FMOD I had lying around and lowered the sub level in the AVR to -12db which translated to around 10db actual. All in all, the bass isn't as strong for obvious reasond and I am loosing some low end shake, but it's more tolerable.

I will keep this updated with any progress I come across

[digital_chris]

Figured I'd give a little update as I did a little playing around...

I decided to test-move the sub to the front of the room, mouth aiming at the front left corner, turned up the LFE output level a few db in the receiver to get the 75 db at my listening position and WHAT A DIFFERENCE that has made! I haven't re-ran Audessey yet but the bass is MUCH stronger and doesn't sound like it's coming from the rear corner of the room, pretty much what I want... The bad part? I can't keep it there, go figure..

Now, this tells me that it's all because of my current room acoustics that the sub "stinks" in the rear corner? What a bummer...

Well, that's about it, if you guys have any suggestions, I'll be glad to hear them

[digital_chris]

I still don't freakin' understand.... how come I can clearly tell that my sub is in the corner, ESPECIALLY during music. What am I doing or not doing that is causing this?

[Gregory East]

Rattling wall maybe?