Straight up comparison REL T7 subwoofer vs Sunfire SDS 12 woofer. Preferences or opinions?

Don't swap, daisy chain them together using the variable controlled Sunfire as the master using the low level RCA outputs on your preamp.  

A crawl test is worth the effort. Inexpensive custom length cables from Blue Jeans or Monoprice.  

stereoisomer

As above, a REL is precise, richer and improved sound-stage. The Sunfire is a close 2nd runner-up. If placement is a preference, go with the Sunfire. It is a bargain and not picky with placement.

Happy Listening!

For what it's worth, I just, um, "subbed" out a used Sunfire junior, which I'd thought was pretty good, for a new REL T9x, and it is night and day.  Using with gen 1 Raidho monitors and a Roksan amp.  The REL has completely changed the quality of the sound.  Richer, more precise, much better sound stage and virtually no boominess.  (The remaining boom will be fixed with some isolation feet.) I, too, was skeptical about whether investing $$$ in the REL would be worth it.  There's just no comparison to what admittedly was a pretty budget but still good Sunfire.

http://pointillistic.com/vmps-audio/subwoofers.htm

You see that slot on the bottom of that column. There is a 15" high excursion passive radiator in there. You adjust the columns Q with putty pinching a fingernail at a time. Very accurate way to mechanically tune to your room, your amp, your cables, your ears.. To bad the company shut down in 2012. The Ideas didn’t

He was getting away from selling that type of open slot (RELs too) on all his subs..

He use front firing slot loaded with a bottom plate on all his floor standing speakers from the 70s on..

Regards

If the driver fires downward against an attached bottom, that bottom is a butt plate.
A better idea is measure the slot height and width, just like REL does and attach a 3/4-2" bottom that distance from the bottom of the sub cabinet. "Slot load" the passive radiator. It can be open front, back, or side, but not DOWN.

THEN you decouple the butt plate or slot from the floor with Springs, Pods, or Air ride. But you NEVER EVER couple anything to a domicile structure.

Think of the Bay Bridge, How much steal would it take to span the bay with just steel, from terminal to terminal all the way across the bay, how THICK would it have to be?

Now think of the springs (cables) they used to suspend the road structure? Remember what part of the bridge that failed during the earthquake? The ridged top deck failed and FELL on the suspended structure below it. SPRINGS? You cannot make some things strong enough on a planet that vibrates. The bolts sheered, they broke bolts in half that were as big as my arm. The springs held..

BUT I suppose you can keep trying.

To heavy of a spring and not enough mass "Galloping Gertie"

Regards

Thank you for your thoughtful and intelligent reply. This is exactly what I was looking for.

I have a Sunfire sds8 and a Rel T7x. I don’t think you’ll see too much of an improvement. IMO the better quality Rel’s start at the S series (or previous R series).  My T7x still breaking in but notice quite a difference between it and the R328, S5, and S5SHO’s that I have. I’d just stick with the Sunfire (I’ve always been impressed with my little sds8)

oldheavymec

What is decoupling in your mind? Thanks

And what is a butt plate?

Well, thanks for questioning my sanity while only mildly insulting me. I guess I'll go spend $45,000 for a subwoofer. Would that cover it? Jesus. Once upon a time Audiogon was a nice place to visit.

I agree with both. I prefer front firing or servo controlled subs.

No, swapping out will not make much difference. You will still have just one sub, with one set of lumpy bass modes. What will make a big difference is adding instead of swapping. More subs will be much better. Put them in different locations, both close to the walls but different distances from corners. Huge improvement.

Neither one, they both have a downward firing driver, without a butt plate or slot loaded.

In other words you CAN'T decouple the sub.. The absolute worst design for stereo playback. The whole house will vibrate.. It makes the floor, walls and ceiling act like a passive driver BUT completely out of time with the actual sub drivers.

NO downward firing anything. I call them Jackhammer Subs. 1970s-80s Tech.

If you know about BASS their site will really leave you with your eyes rolling. Dummest CRAP I've ever read as a mechanic anyways.. ZERO idea about destructive harmonics and decoupling anything from what I read..

When anyone recomends spikes for speakers, I KNOW they don't know what their talking about.. All they see is my dust..

Happy hunting BUT look somewhere else.. :-)

Regards