Bought a Depth !!

[jtwrace]

JonFo,

I wounder if you have overlooked the crossover vs. filter discussion in the ML manual. Nevertheless, they strongly advise against setting the lo and hi filter settings too close to one another. Below is a graph of sub and main speaker performance with a speaker that gives up at 56Hz.

I am far from being done tweaking, and after seeing this graph, you'll say, "Why don't you simply set the hi pass filter to 40 Hz to match your Sequel IIs performance ?" -- My answer: Because it sounds better to my ear this way.

Here is the graphical representation of what happens when the low and hi pass filters are set to 40 and 70 respectively:


From page 10 in the Depth manual:

VanDaRo,

With all respect, JonFo is probably the best DIY tweaker on this site. As far as I know. He has the most experience and his system shows it. Personally, I would embrace his offer to help as the graph that you show needs a lot of help. Also, what are you using for software? I use this (I think JonFo does as well) http://www.hometheatershack.com/roomeq/. Yes, it is a free download.


Good Luck!

 

[VanDaRo]

Of course, you are absolutely correct. JonFo is an enormous resource here and if I came off as disrespectful, I apologize. It was, in no way, the intended result of my comments. In fact, I posted the graphs (both MLs and mine) as a way to extract commentary and advice from the very likes of yourself and JonFo.

Again... My apologies.

Next step: Turn down the sub volume to bring the response curves closer to the 80dB reference line.

~VDR

 

[MOON]

Anyone using an aftermarket powercord to your sub instead of the stock ML pc. If you did , what changes came about?

 

[JonFo]

Of course, you are absolutely correct. JonFo is an enormous resource here and if I came off as disrespectful, I apologize. It was, in no way, the intended result of my comments. In fact, I posted the graphs (both MLs and mine) as a way to extract commentary and advice from the very likes of yourself and JonFo.

Again... My apologies.

Next step: Turn down the sub volume to bring the response curves closer to the 80dB reference line.

~VDR

VDR, no worries. I sure did not feel insulted.

Everyone is free to disagree or ignore my comments, I’m just another hobbyist like everyone else. Maybe a bit more compulsive than most, but still, it's a hobby


As for you next steps, I agree, turn down the sub, as it looks like you are over-energizing some serious room modes.

This is clear to me from your graph (nice job BTW- that's one of the best hand-drawn graphs I've seen posted in a while) that you have two major room modes.

One is a peak centered at 31Hz, right in line with the predicted axial mode for your room dimension (18'x21'x9') and surprise surprise, the other is right at 63Hz, the other major predicted axial mode.

Your large dips are also room modes, in this case also axial nodes, somewhat influenced by the tangential room modes.
For more fun, visit: http://www.mcsquared.com/modecalc.htm

These room modes are why I keep harping on the need for EQ in the bass. The ideal is to treat the room to the point of where it’s largely not needed, but even in my highly-treated room, I still use three or four bands of parametric EQ for the sub.

If the room is underdamped (as yours seems to be), then you must have EQ to tame those peaks. No fixing the nulls though, for that, you have to go the treatments route.

Playing a bit with sub placement and setting will let you minimize the impacts of these room-induced anomalies, but they will still be there in fairly dominant fashion.

Now that you have a meter, just download REW and spend an hour or two learning it, it will save you tons of time down the road. It also lets you actually ‘see’ what’s going on in the room and tune correctly.

 

[VanDaRo]

JonFo -- The sub has been turned down, speaker positions improved, and the collected data is showing that I'm making progress. And the system is sounding better too !! I'll draw another graph if I don't have REW humming along by then. Anyway......The room modes are still there albeit less pronounced.

I joined up with the Home Theater Shack and grabbed their software on my laptop. Before I install it and start messing around, I'll need to cruise over to Radio Shack and get a double-male 1/8" jack cable.

Good news -- the wife and kids are going to Grandmas for the long weekend, leaving me lots of free time to play with the HiFi, watch movies, and slurp some suds. I haven't cranked up any Dream Theater in quite a while....

~VDR

 

[Rich]

I’m just another hobbyist like everyone else. Maybe a bit more compulsive than most, but still, it's a hobby

And JonFo wins the award for understatement of the year.

 

[VanDaRo]

Okay --

So I've made a little progress, but you can clearly see the primary, secondary and tertiary standing waves that are being created in the room. The crazy thing is: The system sounds pretty darn good regardless of the sine-wave / comb filtering pattern of the low frequency graph provided below.

So what's next ?? Will trapping the corners help ??

BTW, I also turned off the high pass filter for the latest gauntlet of tests...

 

[JasonR]

Were this my system, I'd focus on the massive null at 45 or 50 Hz. In the first example, it's right in the middle of your underlapped crossover frequencies. In the second example, it's above your lowpass, and perhaps below the LF response limitations of your main speakers. I wouldn't think that would be the case for the Sequel IIs, but it's not impossible.

I'd say the next step is to make the same measurements with just the Sequel IIs and then just the Depth. Ultimately you'll want to bring together two somewhat similar response curves that meet at a similar frequency (Hz) where they're both a few dB (3d to be exact) down from the baseline.

Anyway... fix the problem at or near your crossover frequency first, and then move on from there. And experiment with phase and subwoofer location. See what phase and location combination gives you a response (with the subwoofer alone) that will most easily blend with your speakers. And THEN try to bring those together and analyze the whole thing.

Finally - trust your ear. If you get a setup that sounds good, go with it. I'm not a big fan of the Radio Shack meter, but I believe there are some graphs online that show where the meter is off at certain frequencies and by about how much, so it may be helpful to look at that. If you can borrow a better tool like a true RTA (Audio Control SA-3050/3051/etc), that might be a more useful guide... but it still doesn't beat your ears.

- Jason

 

[VanDaRo]

Took your advice, Jason. But instead of changing everything just yet, went ahead and graphed the measurements for 0, 180, and 270 degrees of phase.

WOW. What a difference that little knob makes. 180 and 270 gave response curves just as wild or wilder than the 90 degree curve above. But 0 degrees took out the intensity of the peaks and valleys as well as provided a richer curve at the lower limits.

Since the 0 degree curve looks so much better than the rest, I went ahead and ran through some critical listening at that setting. After about an hour of jazz, rock and orchestral music, all I can say is: Gentlemen, I think we're getting somewhere.

Only change since the frequency response test was that I tweaked the sub volume from 4 to 4.2.

Check it out. Commentary strongly encouraged.