[Todd Willhoit]

I am moving forward on a much-delayed servo sub build and I have some questions I suspect the collective wisdom here can answer.

1. Has anyone mounted the driver down-firing?  If so, are there any drawbacks, flooring type issues, and so on?  It seems that down-firing would provide some level of protection against "curious fingers" but I don't know if it creates other issues.

2. What are the pros/cons of a compact, single-box solution with the amp integral to the enclosure v. having the amp in its own box?  For the latter, are there limitations as to how far the amp can be from the cabinet.  I don't remember that the amp or driver came with any type of binding posts.  What do you use?

Todd

[mlundy57]

Todd,

Are you talking about an open baffle or a sealed box application?

Mike

[JLM]

Todd,

Down firing does restrict air flow (like having a port too close to the wall but even more so), so that would have to be taken into consideration in the design, including the length of the spikes (some even add a solid platform underneath to ensure the right distance and material is underneath).

Having the amp in a separate cabinet does help avoid microphonic vibrations, but frankly this is a rather minor consideration for amps designed for such service as evidenced by all the active subwoofers and professional speakers in the world. 

Regarding concerns over length of speaker wire, just follow general guidelines (8 ohm load = 16 gauge 20ft, 14 gauge 35 ft, 12 gauge 60 ft and half those lengths for 4 ohm loads).

[mcgsxr]

Danny can chime in around how length of speaker cable should be managed with a servo sub vs a standard sub.  I run a traditional sub with outboard amp in my media closet, and about 30 feet of 12g wire to my 8ohm load.  I recall that servo subs react differently to longer speaker wire.

I am unclear if servo and downward firing matters (other than the good advice offered by JLM).  I have run one of my DIY subs downfiring in a previous home.  I simply used hockey pucks to space the sub off the carpet.  I did not notice any change in frequency response but did not measure either.  I currently use that one forward facing today in my family room.

[Danny Richie]

I am moving forward on a much-delayed servo sub build and I have some questions I suspect the collective wisdom here can answer.

1. Has anyone mounted the driver down-firing?  If so, are there any drawbacks, flooring type issues, and so on?  It seems that down-firing would provide some level of protection against "curious fingers" but I don't know if it creates other issues.

Down firing them changes the loading on the driver. This is not something that the servo subs need.

2. What are the pros/cons of a compact, single-box solution with the amp integral to the enclosure v. having the amp in its own box?  For the latter, are there limitations as to how far the amp can be from the cabinet.  I don't remember that the amp or driver came with any type of binding posts.  What do you use?

The servo system is not typical of an amp powering a woofer. There is a feedback loop that compares cone movement to the input signal. So additional lengths of wire create a delay. We recommend not adding additional wire to the amp. Mount the amp so that it remains close to the woofer.

[walkern]

I own one of Danny's Servo subs, and I mounted both the amp and the driver on the back of the cabinet.  This allowed me to keep the driver a bit further away from curious fingers since the sub is placed only a couple of inches away from the wall behind it, and keep the cabinet narrow (although it is a little taller to make sure there is the correct amount of interior volume). Bouncing the sound immediately off the wall behind the sub actually seems to even out the response in my room ( I sit near the center of the room, and there are some cancellation points there). 

[jparkhur]

I have done both and find that down firing them is a little less output or course and muffled.  I mounted them forward and sideways and they have significantly better output.  I prefer forward mounting and amp in back, but my application I currently use fires them sideways.  I adjust the output some to accommodate for listening preferences. 


JP

[Todd Willhoit]

Thanks guys.  This is a sandbox build so, without cabinet modifications, the amp can only go in the end opposite the driver.  A single enclosure solution is attractive if only due to the fact that there is less stuff lying around on the floor.  That, and I would need to get tube connectors or other "GR Research Approved" binding posts for an external amp

Realistically, has anyone been able to hear the difference between an inboard and outboard amp?

[Danny Richie]

Thanks guys.  This is a sandbox build so, without cabinet modifications, the amp can only go in the end opposite the driver.  A single enclosure solution is attractive if only due to the fact that there is less stuff lying around on the floor.  That, and I would need to get tube connectors or other "GR Research Approved" binding posts for an external amp

Realistically, has anyone been able to hear the difference between an inboard and outboard amp?

You can mount the amp externally so long as you keep the leads short. It will sound the same either way, in or out.

[gregfisk]

For little ones it seems like the easiest solution is to put on a grill. I don't think this effect the sub in any way and then you don't have to do anything special.

[mlundy57]

Todd,

If you wanted to maintain the internal volume you could build the sandbox so the outer sides, top and bottom extended past the back panel D enough to create a cavity for mounting the amp.

To maintain the structural integrity of the main box I would use two rear panel D's so the back of the driver enclosure remained 1-1/2" thick. You will need to drill a hole through both panel D's for the wires. The hole will have to be sealed once the wires are run through.

The sides, top and bottom would extend past the second panel D at least 4" since the A370PEQ(3) amp has a 4" depth. Then attach the rear panel E and cut out the opening for the amp.

If losing some internal volume is not a big deal you could just cut the amp opening through panels D & E. Then you wouldn't have to worry about sealing the wire hole.

Mike