Sealed enclosure power handling characteristics

Hi Russ:

I have my speaks high passed at 80 Hz with a 12 dB/octave filter rate and this past Friday I powered off my sub and ran a reverse sweep on each surround channel with the Avia calibration DVD.

I was frankly astounded at how loud and how deep the surround channels are still "allowed" to play whan set to Small and high passed at 80. While the AVR was clearly (and correctly) ramping down the volume as the frequency dropped, I still had significant output from the mains, center, and 1000 surrounds well into the 40 Hz region and believe it or not - I still registered 63 dB at 25 Hz from the 800's before they signed off completely!

Not that I ever had any doubts - but for anyone that does, running on Small at 80 really does still give all the surround speaks a really good bass workout and IMO is ideal for HT and if you have a good sub and it is between the mains, it is nearly impossible to localize - the "masking" effect you refer to is clearly intentional and works extremely well.

I honestly know of no speaker in "our" collective price range that can do "Large" justice for HT, and even if it could, what about the center and surrounds? They - almost by design - need to be high passed in order not to lose the deepest bass in those channels.

I will say that there is not one sub level setting that works well for HT and music and typically the sub level is lower for music and it blends all the much better and is even harder to localize. I will concede to a 60 Hz filter point for a strictly and rigorous music application where the sub is not located between the mains.

You might want to ask HBomb of his impression of 2 channel with his dual subs - he uses an 80 Hz filter point and he has challenged 2 channel purists to locate the subs and they cannot. In addition, all of them to a person have walked away slack jawed at the depth and breadth of his soundstage.

It is entirely possible that localization of a subwoofer could very well be from harmonic distortion, as the second harmonic of 80 Hz is 160 and easily localized. I'm not saying your sub in particular suffers from audible THD at 80 Hz, only that it could be a cause of localization in some instances.

As for the rest of this thread, I'm not sure what I can contribute or make of it. WinISD is as good as any other shareware out there, but there is no substitute for actually building and exhaustively testing literally dozens of protoypes before settling on a final design. This is something I have not done, and I prefer to take advantage of someone else's sweat equity and growing pains for my main sub. Just look at what happened to Burdette's first attempt at a sono-sub - it literally shook itself apart and he is currently redesigning almost every major aspect of its build and construction, as well as eliminating the amp shelf since it buzzed badly. This is no reflection on him per se - his experiences are quite common in the DIY sub community for first timers.

If I was looking for quality bass and deep extension on the cheap, a passive SVS 20-39CS or 16-46CS would be tops on my list for under 5 bills - you just can't buy a proven better bass value anywhere and you avoid the pitfalls of first time DIY.

Regards,

Doc

Here is the FR of my sub - the FR with one port plugged is what you can expect from the 16-46 enclosure.

RS - if you want help designing the volume or venting requirements for that driver, just give me the T/S parameters for it and what you want it to do, and I'll see if I can churn out some recommendations.

Doc

Is this for just a sub or are the woofs part of a full range unit - I can't seem to determine it from the thread.

Also, what are your goals for FR, extension, and SPL capability?

Doc

Both drivers are well suited to a sealed alignment, since the Qt is 0.65 (10") and 0.55 (8").

If you want to hit an honest 30 Hz, I would select the 10" since it has an Fs of 25 Hz, and the 8" has an Fs of 30 Hz. Both should hit fairly low, but the 10" will do it better.

The Xmax is a very paltry 4.25 mm one way for each driver, and I doubt highly a pair of 10" will hit 110 dB down in the 30-35 Hz range. You can tell by looking at the depth of the basket that this is a very low excursion driver.

Sealed enclosures are not known for being powerhouses to begin with, and they need a long Xmax and a very strong VC/motor assembly to hit hard down to 30 Hz because the sealed enclosure loads the driver and fights it as it approaches Fs and/or the tuning point. Power compression (i.e., VC/motor heat-up and associated SPL loss) becomes a real problem with sealed subs at high volumes.

If you are really looking for 110 dB at 30 Hz, you might consider a more powerful driver like the Adire Shiva which has a much higher XMax and has been successfully employed in sealed alignments.

If you are dead set on the Morel, then I would advise twin 10" per box if you want a shot at those SPLs at 30 Hz, and even then it might be a stretch. Those woofers will quite simply bottom out very quickly at lower frequencies and high volumes.

Doc

Originally posted by rs159 I'd rather have the sound of a sealed box than the boom factor of a vented or bandpass design.

Wilson, Dynaudio, B&W, Aerial, HSU, SVS, REL - ALL vented. No one accuses them of being boomy. A vented alignment is harder to perfect, certainly, but done properly, it can sound as good as a sealed enclosure.

Many people think sealed is more musical because they seem to "start and stop on a dime", and in theory they do have a slight edge over a vented design in terms of transient response and group delay.

But of far more subjective importance is the fact that truly deep bass quite simply takes longer to decay in a room - it's the nature of the beast. And some poeple mistakenly perceive this as being "slow" because a sealed design rarely reaches below 30 Hz with authority and appears to be much "quicker" in comparison.

I will also admit that my sealed large Advents have great bass and are flat to 31 Hz and are terrific for most music. I would be perfectly happy with a sealed design for music, but not for HT, where SPL AND extension AND good sound are all required at the same time. For this, vented or PRs rule the roost.

Doc