Design for small musical sub or fix old sub?

[fvoelling]

Well, I'm still looking for some decent sound in my home office. Since my desk is up against the wall, I'm either stuck with a) computer speakers, b) headphones, or c) smaller wall-mounted monitors.

Forget a), I'm using b) now, but it's not an all day solution, and for c) I've bought some PE drivers for a Modula MT but haven't seen a design for a bookshelf/wall-mounted version.

Since I've always liked the sound of planar speakers, I decided to buy the wall-mountable Magnepans (they're only $300/pr). Catch is, they only go down to 100hz, so a sub is almost a must.

Do you know of any designs for a smaller (ideally 12" cube, max 18" cube), "musical" sub that will go up to 100hz or more to complement the Maggies?

Alternatively, I have an older 8" M&K VX-7 sub, kind of looks like the one shown here:

http://cgi.ebay.com/M-K-Miller-Kreisel-VX-7-Powered-Subwoofer_W0QQitemZ9706456928QQcategoryZ3275QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Mine still has the foam (rubber?) surround, but it's almost completely detached from the inner part (clothes?) of the driver, like the glue failed. Is this something that can be re-glued (super glue?), or do I need to replace the entire driver? Would I be better off to replace the driver with a better one anyway, and if so, how would I know what type (impedance, single/dual vc, etc) to replace it with (any good suggestions)?

Thx,
Frank

[ThomasW]

I thought I read that the MMG-W only go down to 120Hz? Maybe that was something else.

Obviously you can get the M&K refoamed, I don't have a clue how well it will work for you needs.

The HO version of the PE RS315 is designed to work in a small box. It's probably your best choice if you want something to play higher frequencies than a standard sub, and work in a small box

[Jack Gilvey]

I'd bet even the 10" version would be nice with those Magnepans, and allow an even smaller box. The RSS265HF looks cool in ~0.75ft^3 with 250 watts. I think a 100-120Hz crossover would be no problem.

[Brian Bunge]

If you want really small, I've got the 10" HO version in a 13" external box made of 3/4" MDF and a 1.5" baffle. It works pretty well, IMHO.

[fvoelling]

Thanks for the suggestions! Given my relatively small room (15x13) and low volume listening levels, I'd think that the 10" should suffice. However, I'm a bit puzzled by the differences between the "high output" (HO) and "high fidelity" (HF) versions of the PE drivers.

Here are the relevant specs:

                    RSS265HO-4       RSS265HF-4      
Power Handling      600W RMS         350W RMS
Freq. Range         24-600 Hz        22-1,000 Hz 
Vas                 1.2 cft          2.12 cft
Qms                 4.2              2.8
Qes                 .36              .45
Qts                 .33              .39
XMax                12mm             14mm 
Sealed Volume       .3               .82
Price               $96.00           $119.80

My beginner's understanding of these parameters would have expected the "high fidelity" version to have a lower XMax and Qts, but the exact opposite is the case!?

Which one will sound better for music? The HF because it requires less amp power for a given volume level (less distortion), or the HO because of its lower Qts (tighter bass)?

I interpret the value for the sealed volume as the recommended (minimum?) interior space of the enclosure - is that correct (that would be a mighty small box for the HO version)?

Thx,
Frank

[ThomasW]

The HO versions have much higher power handling and work in a smaller box.

In a perfect world the HO versions would have the higher Xmax and lower Fs but Hoffman's Iron law dictates how these things work.

[fvoelling]

Thx, Thomas! Does that also mean that I need a more powerful amp for the HO? Again, I'm not looking for high volume levels, just controlled bass output that seemlessly integrates with the MMG W (I double-checked, they are 100Hz-16kHz). If the HF version does a better job of this, I don't mind the bigger box.

Of course, PE has the HO version on special right now, but if it requires a bigger amp, that savings will be offset by the amp's higher cost.

[ThomasW]

What amp do you have? In this day and age power is cheap.

[fvoelling]

The plate amp in my old M&K is only 100W, probably not enough for either driver.

What if I were to buy the PE 250W plate amp (300-794)? Would that be enough for the HO version, and which one (HO/HF) would likely sound better with it (and the MMG Ws)?

[ThomasW]

That amp is probably custom matched to the woofer. This means EQ and other tricks specific to that driver. So you should factor a new amp into the budget.

I'd be tempted to use one of the larger plate amps. A better long term investment is a fan cooled prosound amp if you can live with the noise of the cooling fan.

[fvoelling]

Well, I've got a Nady 1100 on order from PE (if they ever get them back in stock), but that one's already reserved for my IB :T !

This setup is for my office, and I'm already going nuts over the PC's fan noise, so a pro-amp is definitely out. Besides, I'd be totally lost with the integration issues, separate crossover, etc, that's entailed with an external amp, so a plate amp with integrated crossover is my best bet.

I'm all for future-proofing, but my volume levels are really low in my office, and this thing will sit right under my desk (assuming it will fit ) in front of me, so a 10" subwoofer with a 250W or 300W amp should suffice.

What's your take on the digital BASH plate amps, and how important is a continuously variable phase in my situation?

Thx,
Frank

[Brian Bunge]

I'm using the 300W unit with my RS10"HO. I think it's a really nice amp and don't miss not having continously adjustable phase. It's definitely not a deal breaker for me.

[fvoelling]

Just got the parts from PE today, decided on the RSS265HO-4 10" driver and a 250W sub plate amp (PE 300-794).

If I had more time, I'd try to build a furniture-grade enclosure, but the trial period for my Maggies is limited and various spring projects like a 16x24 shed are keeping me busy already. So, at least short term, I'd like to build a box for it FAST (no finishing). I have tools like TS, router, sanders, and so forth, and a couple sheets of 3/4" MDF floating around.

Measuring the parts, they should fit into a 13" (outside dimensions) cube (like Brian's). Is it as simple as slapping together a cube like that, double up on the walls for a total thickness of 1.5", mount the driver and the amp, stuff the white filler from my old sub into the box, hook things up, and I'm in business?

And since this will sit underneath my desk on a carpet, I bought spiked feet for it. Could I mount the driver in a down-firing configuration (so I don't bump into it accidentally), or would it sound better firing forward?

Thx,
Frank

[ThomasW]

You don't need double wall for a small box 10". Double the front baffle and use window bracing with 3/4 material for the rest of the box.

I wouldn't downfire into carpet..

[Brian Bunge]

My 13" cube is 3/4" material except for the 1.5" thick baffle. There's also a single brace in there. It's very sturdy.

[fvoelling]

Thanks, I'll build mine the same way, firing forward. That means using some kind of metal grill, would this work or do I have to go to the 12" version to be able to mount it:

10" bar grill

Also, should the brace be centered front to back - I remember reading that the driver should have at least 3" of free space behind it, which would put the brace at 8" from the front outside edge and 4.25" from the back outside edge?

A couple of drawings (wish Yahoo didn't compress so much):

Cut Sheet

Top View

Frank

[ThomasW]

Looks fine, have fun..... :T

[Brian Bunge]

I'm lazy when it comes to subwoofer enclosures and bracing, so I don't bother doing window braces. Instead, I just cut a roughly 8" diameter hole in the brace, leaving a couple of inches thickness all the way around. It might not be as sturdy as doing multiple smaller holes, but it was quicker. Besides, I wore myself slap out cutting all those damn holes in the braces for my big towers.

[steve nn]

It might not be as sturdy as doing multiple smaller holes, but it was quicker. Besides, I wore myself slap out cutting all those damn holes in the braces for my big towers.

On the bright side a guy could always do a extra brace, but it seems as though the window style is plenty sufficient as long as it's anchored well.