[shaizada]

Hey Guys,

I've got two deephemps along with Super 8's.  So far, I've been running the deephemps in the corners of the room behind the speakers.
I set them up with foam balls in the ports of the Super 8's and everything has been running great.

However, I was wondering if anyone has a setup where they leave the ports open on the main speakers and setup the deep hemp subs accordingly?  It would be a very different sound, but is it advisable to do so?

If so, what crossover settings do you have with the deephemp.

I run the deephemps off the amplifier, so through the high level inputs.

[DaveC113]

Yes, you could try running one sub on the front wall and one on the back wall, there's a lot of info on that in the bass forum from people who are more experienced with those setups than I am.

I prefer to keep the subs out of the corners and crossed over pretty low, about 50-60 Hz. If you have more than one it should be better to space them asymmetrically to help with canceling standing waves. I'm running the 4.5" XRS and a 10" sealed sub, I would like to upgrade to 2 or 3 subs eventually...

You might want to try posting in the bass forum or linking to this thread from there if rules allow...

[shaizada]

I just wanted to post an update here just in case others were looking for similar information.

For the Omega Deep Hemp Subwoofer, the frequency range on the subwoofer plate amp goes from 40 Hz to 180 Hz.  Looking at the actual knobs, you will see divisions on the plastic knob itself.  I counted them to be 17 steps (knob divisions) between 40 and 180 hz (min and max play).  That means each division is about 8.235 Hz.
[(180Hz - 40Hz)] / 17 = 8.235 Hz

In MY setup, this is where I am at now and am pretty happy with finally. 

- Super 8 Alnico ports plugged in with Nerf Balls.
- Phase set to normal for both Deep Hemp subwoofers
- Gain set to +2.5 divisions from the middle/midway of the gain knob
- Frequency knob set to 6.5 divisions from minimum (the 40 Hz Position).  That is 8.235 * 6.5 = 53.52 Hz Approx.  (Works right in with Dave's suggested freq. range).

PLEASE correct me if you find anything wrong or have other suggestions.  My goal was to have the most seamless sounding setup from the Full Range running of the Super 8 to the Deep Hemp subwoofers.

Thanks for reading! 

[doctorcilantro]

I have gone through 2 of these amps, as have others on DIY Audio.

Anyone getting any ground loop issues when connecting via speaker terminals? My system buzzes when powered down, but the loop goes away when I bring the amp online. But I have had other strange buzzing sounds at times so I am now experimenting with RCA connection to the plate amp, which solves the ground loop.

I think those settings look about to be what I am using.

Info from Dayton:

"The high level inputs on the SPA250 are specifically intended for use with an amplifier that does not have a low frequency line out (sub preamp output). The sub amp takes its signal from the speaker level inputs, left and right, through a high-resistance voltage divider circuit. It does combine the channels to mono, it will not "load" the tube amp at all being connected this way. If you connect your stereo speakers to the high level output on the SPA250, they will be high passed at about 150 Hz (bass rolled off). If you would prefer they run full range as usual, connect them directly to the tube amp. "

[DBC]

For what it's worth, my 2 cents on the subject.

Corner sub placement will take advantage of room reinforcement and provide maximum low frequency output but at the same time will likely over-excite certain frequencies resulting in a Boomy tendency. To overcome the Boomy tendency you have to lower the sub volume and or crossover frequency.

I prefer my twin subs out in the room where they are least likely to excite room surfaces and over-excite any narrow frequency range (actually use my subs as Monitor stands). I also use isolation platforms to isolate my downward firing subs from the floor (these made a big difference in improved Bass clarity in my system) Getting the subs out of the corners and placed on isolation platforms allowed me to increase sub volume and crossover setting while achieving much better Quality Bass and a much Flatter Low Frequency in room response.



On the subject of Ground Loops. If you have a buzz or hum using speaker level connections, it's likely because your sub (like mine) only has a 2 prong electrical socket at the plate amp. This means the plate amp is not connected to Earth Ground even if you use a 3-prong power cord. I resolved my Hum issue by using a Radio Shack test lead with alligator clips on each end. If you zoom in on the photo above you will see the Red test lead clipped to a toggle switch on the Sub's plate amp and the other end clipped to the case of the power conditioner which is grounded to earth ground. This allows any stray electrical noise at the plate amp to bleed harmlessly directly to earth ground. Without this Earth Ground stray electrical noise will flow via your speaker level connection back to your amp (which is connected to Earth Ground) thus the audible hum.

When you connect the sub via Low Level signal (interconnects) the hum is eliminated because any stray electrical noise at at the Sub's plate amp travels via the ground lead of the interconnect back to Earth Ground at the amplifier. I will let you decide if using your interconnect as an Earth Ground conductor improves or degrades the audio signal to your Sub. I've compared Speaker Level and Line Level connections in my system more than a few times. To my ear Speaker Level connections have always resulted in better Sub integration.

[doctorcilantro]

I too have noticed better integration from Speaker Level connections because I have always done it like that for years, and can already tell a difference. Things sound bloated. I have Zu unions.

I have noted the lack of ground on the DH, a little hum is ok on my setup, on any driver you have to be within a foot, it's the buzz the sucks.

but since the ground loop would resolve itself when my main amp was on, I never suspected the sub to the cause of what I hear intermittently, and louder ground loop type buzz that comes and goes at times. I chalked that up to DC offset, but more and more folks telling me that DC shouldn't actually manifest like that.

I have a ground wire like you describe for tethering things together when need be so ill bust it out. Things for the insight.

[DBC]

I've had a number of Subs over the years, all with some low level hum. Had come to accept the fact that some sub hum was normal. When I attached the Earth Ground lead as described my Twin HSU subs went Dead Silent. In my case this translated into a considerable improvement in Bass Quality. If you can get rid of the Hum you will be pleasantly surprised.

I realize that not all audio equipment handles Earth Ground in the exact same manner. But I would think in your case with some experimentation you can get rid of the hum.

[Canada Rob]

Thanks DBC, very useful information.

For what it's worth, a few years ago I had a very good phono stage but it had a bad hum over the speakers (no sub).  It was solved in a similar manner do what DBC describes.  After doing it, the system went dead silent as far as hum goes. 

[doctorcilantro]

I couldn't find my ground wire but I did find some heavy gauge wire I can use on one of the screws of the plate amp; for now I tested with a single RCA cable connected to Output, cut the cable and wired the neg. only to a single ground wire which kills the ground noise, when my system is powered down.

So far, when energized, the system has not exhibited the strange buzzing at random times.

When I get time I will pull the sub out and wire to the plate amp screw.

[doggie]

I found that without using the nerf balls I lost some coherence and impact although gained a bit of lower end "fullness" which was not well defined. I now use the nerf balls (without the plastic wrappers) and let my sub do the heavy lifting. This is general information as I have Super6 Alnico floorstanders and another brand of sub however I think the principle will apply.