Official Rythmik Audio Subwoofer thread - Page 6

I don't think so.

Improving on sound quality is never a bad thing.

Knowing thet the crossover is not defeatable, explain to me the best way to set the crossover and other settings to the D-15SE. I have THX Ultra reciever and Klipsch THX Ultra2 speakers. I want the best blend for my speakers utilizing the THX reccomended spec of 80Hz. My room is approx 2100 cu ft.

Would an HSU ULS-15 be a better choice for THX speakers?

Thanks.

Brian:

Could the new 600W amp be used to drive two of the older DS1500 drivers? I was thinking of a dual opposed box with a single amp, like an Epik Empire or Seaton Submersive.

Can't stress Brian's phase comments enough.

You don't have to get phase perfect, but at some point it can turn the normally tight sounding sub into something that sounds a bit flabby. I think this is because bass notes often have harmonics that reach very high in frequency, so if your sub is not playing in concert with your mains, things fall apart.

All good reading, but can u give me the initial settings for vented THX speakers?

Similar question here. For a submersive-like design with Rythmik drivers should I use two 370 amps?

David, for the crossover, I believe you simply set the crossover slope switch to EXT 12 and turn the crossover knob to the maximum. Not sure if that second step is necessary.

Flat upper extension on a sub? Hmmm... I have always found the problem to be with directionality as the frequency gets much north of 50 - 100 Hz. In controlled test years ago it was easy to localize a sub at around 100 - 120 Hz, almost impossible at 50 Hz, in between a gray area. With satellites crossing over around 80 - 100 Hz, there was enough energy in the upper bass to me that I felt dual subs were needed. My main speakers go low enough that isn't an issue, but I like the idea of duals for various other reasons. YMMV.

Given the slight power difference (less than a nightlight), auto-on only matters to me if it's needed to control turn-on transients (thumps). Not a problem I have seen in the past decade or two, at least for anything I have tried. My old vintage (ARC SP-3) tube preamp does need some warm-up time, however, if you don't want to lose an amp, and/or maybe a speaker. Trust me on this... As it stands, the limiter sounds like a good idea to me. I doubt it will have any audible impact in the subwoofer range (higher, yes), and it sounds like an idea that will save a lot of speakers and EARS! Hearing damage is not a good thing.

I would be glad to post what I hear (which of course may not be anything like what you hear) from an A-B with the limiter on and off once my new subs arrive. For equipment I am using Magnepan MG-IIIa's driven by an emotiva XPA-3 for my mains, from a Sony ES3400 receiver, and with an Infinity center (driven by the emotiva) and Mirage surrounds (driven by the Sony). However, by this weekend I should have the new subs plus a new center and surrounds from Magnepan so it will be quite an experience. My first major system upgrades in years.

New toys! - Don

p.s. Not sure how ground loops snuck into Brian's reply to me. I have many years' experience doing live sound and sound installs though little recently (not my day job) and ground loops can be terrible things. Despite the "quick fix" they often provide, a cheater is my last resort for many reasons, not the least of which is that they can be dangerous. Besides the obvious shock potential, my neck of the woods is very dry (CO front range) and static is a big problem. I want the ESD going to a good ground, not inside my components...

I will throw another out there. Have pre-made enclosures for sale so people can mix and match, like me who wants a F12G but in the downward firing box design you show on your website.



I have run stereo subs for years (Velodyne ULD-12s). There is a definite benefit to stereo subs. I think it is two fold, first it helps flatten out room peaks and nodes, second, it preserves out of phase bass information in a recording that would otherwise be summed out in a mono subwoofer.

In regards to a subwoofer having flat upper extension, this is very important in my book. Assuming a 12db octave crossover at 80 hz, the subwoofer is only down 12 db's at 160hz. Any nonlinearity in that range could easily effect the sound.

How much would a dual 15"/H600 servo amp kit cost?

We agree! That's why I made the comment about satellites in my post. However, I cross over around 40 Hz, so an octave away at 80 Hz the sound is about half loudness (more than 10 dB down) as you say (with a second-order LPF; my previous system used 3rd-order so 18dB/octave) and relatively non-localized. At 80 Hz crossover, I would not be happy without dual subs -- too much energy left up where it can be heard and localized. With my current mains, I can cross over low enough to minimize the issue (though I still ordered two subs).

The new variable for me is HT's LFE channel, which apparently includes content to 120 Hz in the sub channel. One of the reasons I decided to run two subs; I'm still debating whether to hook them up in parallel with the mains (creating extra-full-range mains and telling the AVR "no sub") or in parallel from the LFE output (opinions welcome, though probably should be in another thread). I hope to try both.

I was asked regarding the higher-power amps (shouldn't have, as a newbie and unknown voice here, but one was curious why I didn't wait). In my relatively small room I don't need the extra output, especially with two subs, and damping factor (speaker control, the -- or at least my -- other reason for bigger amps) is a non-issue with a servo loop. It takes twice the power to generate a 3 dB loudness increase, just noticeable to most of us listening to musical (or movie) source material. Twice as loud, 10 dB, 10x the power. However, the ratio of average to peak power in music is around 17 dB, or about 50x in power, so it does pay to have some overhead in your amps. But, the difference between 370 W and 600 W is not all that great in the real world, where your average power might be just a few watts. And with servo subs in relatively small boxes, great gobs of power should not be required (let the rebuttals begin).

All of which is a nice rationalization for simple impatience -- I couldn't wait to get my new system set up!

Just read that phase document Brian referenced off of his page. Going to have to read it again and get my brain wrapped around it a little better before my F-15 (600w) gets here - next week hopefully.

What would the output be for this combo compared to a single 15 or single 12? What size enclosure would be required? Would the drivers be black or silver?

Just got my F12 today. Looks awesome. My question is, I don't know how to connect the LFE output from my Onkyo 805 to the L/R inputs on the F12. Should I just get a Y splitter and connect to L/R or just put the LFE into one of the inputs?

Yes either way would be perfectly fine, just remember to adjust the gain control on the sub appropriately (so the Onkyo's calibration level ends up around in the -5dB to 5dB range)... And congratulations on your purchase of a great sub.

I would like to read your ideas on phase coherence, but the link above seems to not work for me.

Try this one: http://www.rythmikaudio.com/phase1.html

Thanks Sanjay. Now, is there any way to download that as a PDF (or whatever) for a clean print-out? Maybe I'm blind, but I only saw the three-page online version...

This is vital now that I have my subs sitting on the floor ready to go! - Don

OK, so I read the article, and it makes a lot of sense. The concept that the phase must align around the crossover to prevent cancellation (and thus a dip in response) is clear (aligning multiple drivers in a speaker, or PA system, is something I am familiar with). However, is there a chart somewhere that we can find the phase of our speaker, assuming we can't get it from the manufacturer (mine are fairly old though still nice)? Otherwise, it seems to me we still have to adjust and listen (or measure) to optimize the phase (delay) control. I suppose the easiest way might be with test tones around the crossover frequency and an SPL meter? Just adjust the phase for maximum output?

Curious - Don

Thanks Brian -- I'm off to pick up a new SPL meter this morning. My cheap old hand-held spectrum analyzer isn't the right tool for this, and the company I work for now does not have audio test gear (when your sub goes up into the GHz range, I can test it! ).

I think the most important thing with group delay is that it's as flat as possible, but yeah if it's pretty far off between sub and mains I can see where there'll be problems. Especially if the sub lags the mains -- hard to reverse time! I like the idea of playing with the distance settings, though my new receiver (Pioneer SC-27, two weeks away) should balance things across frequency.

In response to your first answer last (follow that? not sure I did...) my mains are planar bipolars -- Magnepan MG-IIIa's -- so phasing gets a little complicated. The good news is that they are very linear speakers (good impulse response); the bad news is that the room's influence is huge on the wavefront at the listening position due to the reflected waves. To further complicate things, there's an inversion (180 deg shift) in the system to the mains (not sure where it's at, just that the AVR's cal routine caught it).

Excellent point on the microphones -- I have a nice (and pricey!) earthworks measurement mic, but as I recall you are right that only an amplitude calibration curve is provided, no phase data. OTOH, you'd need to calibrate the system through the pre and whatever anyway, for amplitude and phase, so having just the mic amplitude response is not perfect.

One final question/comment for you or whomever: Do you suggest spikes under the subs? My media room is in the basement so has concrete under the carpet, but there's a fairly new (thick) carpet and pad on top. I realize the weight of the sub will flatten it down, just curious. I never would have believe Doppler effects matter for audio speakers, but some listening and measurements convinced me otherwise many years ago.

Thanks much -- the new subs get turned on today! - Don