Table Tuba build!!

[SeisTres]

Nevermind, I thought you were using the LP on the plate amp, but the signal is already set up for sub duty, so it's all good.

[Bill Fitzmaurice]

I don't understand how the crossover on the amp makes any difference when set above 80, and if set below 80, won't that cancel out the AVR crossover point?

It will cascade the LP filters. When the slope of either alone is insufficient, the slope of both together is sufficient. And since you're getting directional cues from the sub then obviously the slope of the receiver filter is insufficient.

[Tom Smit]

Your build is inspirational!
For the table top, did you build the cab and then add the top. Or, is the top actually an oversized panel?

[BoostFab]

Your build is inspirational!
For the table top, did you build the cab and then add the top. Or, is the top actually an oversized panel?

from the look of his pictures, he built the TT out of mdf, and add the wood to outer shell that makes up a table.

[digital_chris]

Your build is inspirational!
For the table top, did you build the cab and then add the top. Or, is the top actually an oversized panel?

Boost has it correct, I basically built a box around a box. And to answer the next questions, yes, it is VERY VERY heavy, lol. Thank you for the nice words

I don't understand how the crossover on the amp makes any difference when set above 80, and if set below 80, won't that cancel out the AVR crossover point?

It will cascade the LP filters. When the slope of either alone is insufficient, the slope of both together is sufficient. And since you're getting directional cues from the sub then obviously the slope of the receiver filter is insufficient.

I am sorry for being so ignorant (I am still learning), but I guess I still don't understand slope all that well. Are you saying that the crossover in the receiver is not sufficiently separating my mains from my sub at 80 hz therefor sending signals lower than 80 hz to my mains and signals higher than 80 hz to my sub? To correct that, for the sub anyway, set my sub amp at 80 hz to make sure I am not getting unwanted signals to the sub?

[Tom Smit]

Yes, you've got it more or less figured out. The cross-over point has a slope, but, the slope might be too gentle (eg. 12db/octave). When that happens, the sounds below the slope are still audible. So, if the signal goes through another cross-over,ie your sub amp, the slope becomes steeper...as a total. The higher the number of db/octave, the more cliff-like the slope becomes.

[SeisTres]

I tried 12db slope, 16db and 24db (did not have 48db) slopes for sub duty and I found that 12db/octave was not acceptable even in a home setting. However, 18db was ok, and 24 works really well. And yes, the High pass and low pass filters just "tame" the response after a certain value; they don't stop all signal after the frequency. So in this case, bigger is better to keep the sub from being annoying in the upper range.

[digital_chris]

What do you mean when you say you tried those different slopes?

[digital_chris]

I hope everyone had a great holiday!

So, I ran audyssey for the last time (I think) and this time it set my mains and sub gain to neutral (around 0 +- 1/2 db) after lowering the gain knob on my Foster amp to 1/8 of full power (WOW). It set my crossover point to 60hz which I then changed to 80hz. I also turned my amp's low pass filter to 80hz as well and I think I will leave it there. Since then, I have played a few movies that have decent LFE and I am pretty happy with the sound. Some LFE is more noticeable to be on the right side of the room (side the sub is located) and it doesn't help that I KNOW the sub is there and listen for localization but I notice it's not as spread out as much as I hoped for, but I guess it's just the sub location and lack of noise absorption in certain areas.

The other night though, I played 3 movies that have some decent LFE (Transformers on DVD and The Fourth Kind as well as SALT on Blu-Ray) and I notice that the bass on the lossless tracks seems to be less localizable and I am happy with that but as for Transformers, most of the good LFE is less "spread out".

Is there a reason why the lossless LFE is more, idk, uniform I guess?

[SeisTres]

What do you mean when you say you tried those different slopes?

When I built my sla's, I used my Driverack to determine the frequency of the filters I would order and I also tried the different slopes while I was at it.

[digital_chris]

I'm still a little confused on how you tried different slopes, but setting the potentiometer at different spots inside the amp?

[Tom Smit]

Take a looky-through on this site http://www.the12volt.com/caraudio/cross.asp#lp to learn about calculators, slopes, etc.

[digital_chris]

Thanks for the link Tom, good reading material

[SeisTres]

I'm still a little confused on how you tried different slopes, but setting the potentiometer at different spots inside the amp?

the crossover slopes and the potentiometer are not related topics.

I tried out different slopes with my dbx driverack pa and my crown xls's powering the sub and tops. You can choose different slopes with it.

The only thing that the potentiometer is shape the curve of the amp like the ones in the documents provided.

[digital_chris]

Ok, thanks for clarifying