[chadh]

I currently run Omega Super 3 XRS speakers (4.5" single drivers) with a 5w/channel SET amp (Music Reference EM7).  I talked to Roger Modjeski the other day, and am hoping to have him build a pre-amp/active crossover for me that will let me add a pair of subwoofers into my system.  The plan would be to crossover at around 100Hz, with a 24dB/octave low pass filter for the subs and a yet to be determined high pass filter for the mains.

As I said, the crossover would all be taken care of within the pre-amp unit, so all I'd need to add would be a pair of subs and two channels of amplification. 

I'm not all that fussed about getting any particular frequency with -3dB.  My concern is mainly with taking the low frequency load off the 4.5" drivers and fleshing out the bottom end a bit.  I'm envisioning using small, sealed subs that will keep up with the Omega speakers.

I'm also looking to keep costs down!  As a result, I'm considering the possibility of DIMyself subs.  I'm looking for recommendations for drivers.  10" (or even 8") options are likely candidates.  I'm also looking for recommendations for amplifiers.  I'm imagining a pre-used, solid state stereo amp of around 100 - 150w.

Feel free to suggest different directions as well.

Thanks.

Chad

[strider]

Having done something quite similar recently, I'm expecting that you'll enjoy the results of taking the lower frequency load off of the 4.5" single drivers.

I built an active Linwitz Riley crossover from a kit, which sends everything above 120hz to my diy Fonken monitors (with 4.5" Fe127e drivers) and below 120hz to a "Fonkenwoof" which is comprised of two 7 inch woofers mounted in a side firing push-push configuration in an approx. 1 cubic foot ported enclosure for each channel. I bought the drivers from Planet 10 and Dave Dlugos, who also provided the plans for the Fonkenwoofs and answered my neophyte questions.

The Fonkenwoofs are still breaking in, but so far I'm quite happy. The Trends class T integrated ran out of steam at about 12 o'clock on the volume knob when it was running full range. Now that it doesn't have to worry about the low end it retains it's clarity at a much higher level. The single drivers are much happier now that they don't have that frequncy range to reproduce as well, and it's nice to have that tactile bass that the 'Woofs provide. Very clean and tight. I'm using a Rotel RB980bx rated at 240 watts into 4 ohms (I think) to drive them. Still have to play around with how much stuffing in the cabinets.

The woofers I used are Easttech, which are recycled from another enclosure I believe. If I had the budget, I'd be looking at the CSS SD7.

[chadh]

Many thanks for the comments.

The CSS SDX7 does look like a pretty sweet alternative.  But what do you think you gave up by using the Easttech drivers?

Chad

[opnly bafld]

I would recommend 2 of ACIs Rage 12" drivers ($39 ea. if still available) in a +/- 1.5 cuft sealed isobaric cabinet, should get you down to low 30s and sound pretty tight.

Lin

[strider]

Many thanks for the comments.

The CSS SDX7 does look like a pretty sweet alternative.  But what do you think you gave up by using the Easttech drivers?

Chad

The Easttech's can't handle much power, definitely would have more low end extension with the SDX7's, maybe a bit more refined? I think the Easttech's were OEM drivers that were recycled out of an enclosure for a more run of the mill brand, maybe Monsoon? Doesn't have the audiophile cachet, for all it's worth....  I enjoy them nonetheless.

I think the SDX7's are quite flexible in terms of what enclosure they're happy in, too.

Ben

[chadh]

I would recommend 2 of ACIs Rage 12" drivers ($39 ea. if still available) in a +/- 1.5 cuft sealed isobaric cabinet, should get you down to low 30s and sound pretty tight.

Lin

I didn't see the Rage drivers on the site.  But that doesn't mean they're not there.

I did ask Mike about the SV10 driver (a 10" driver that is used in the Force subwoofer).  Mike suggested about a 1.5 cu. ft. box for these too.  This reminds me, I need to contact him for details!

Chad

[chadh]

I was checking out the CSS-SDX7 6.5" driver, and found the following CSS document describing sealed cabinets for this driver:

http://www.creativesound.ca/pdf/SDX7-sealed-pass1.pdf

From this, it looks like I could get Q = 0.5 from a 0.75 cu. ft. box.  But, from the frequency response charts, I'd be -3dB at around 68Hz and -10dB at around 32Hz.  Does this seem way too little bass output to be bothered about?  Or would it represent such a huge increase from what I'm used to that I'd never know I was missing anything between 30 and 70 Hz?

In general, I'm trying to gauge the tradeoff I'm facing between finding a low frequency driver that can keep up nicely with my Omegas (making me favor a smaller driver) and augmenting the bass output of my system (making me favor a larger driver).

Chad

[Tyson]

I've heard a bunch of subs (commercial and DIY), and there are only 2 that impressed me with music - the VMPS subs with the woven carbon fiber woofers, which were particularly good at texture and clarity.  The others were the Rythmik subs using servo control technology.  Both can be bought as kits.

[strider]

In general, I'm trying to gauge the tradeoff I'm facing between finding a low frequency driver that can keep up nicely with my Omegas (making me favor a smaller driver) and augmenting the bass output of my system (making me favor a larger driver).

Chad

Therein lies the conundrum. When simmed, my set up should do into the mid 50's for a -3db mark, IIRC. In room, with the room gain, maybe high 40's. Not real impressive spec wise, but they sure integrate nicely with the single drivers. When I had an (admittedly cheap) sub in the mix, it sounded like two different speaker systems, one with clarity and great localization but not much weight and another with the bass presence but no finesse at all. Didn't work for me.

That being said, I'd love to build one of the servo subs (or maybe even two  ) to get some real low end grunt. Maybe run the Fonkenwoofs from 200 hz on down with the subs to fill in where they trail off......One day, maybe.

[opnly bafld]

I didn't see the Rage drivers on the site.  But that doesn't mean they're not there.

I did ask Mike about the SV10 driver (a 10" driver that is used in the Force subwoofer).  Mike suggested about a 1.5 cu. ft. box for these too.  This reminds me, I need to contact him for details!

Chad

http://www.audioc.com/specials1/springmisc.htm
Scroll to the bottom left of page.
Isobaric loading reduces box size by about half (3 cuft to 1.5) and the 12"s go @ 10hz lower than the 10"s (both sealed no eq).

Lin

[chadh]

I think I've decided against the 6.5" woofer.  Instead, right now, I'm almost ready to pull the trigger on a pair of the "Force" SV-10 drivers from ACI.  At 10", these probably won't go as deep as others.  But that's not the ultimate issue for me.  Mike assures me that the SV-10s in sealed boxes will be fast enough to keep up with the single-driver mains.  PLus, they are on sale for only $79 each!

Any other last minute suggestions that I should consider?

Chad

[doug s.]

hi chad,

i posted this before, in discussing subwoofing:

http://www.audiocircle.com/index.php?topic=68278.msg632284#msg632284

tho i suggested crossing over at 50-70hz, you could likely bump it up to 100hz w/o any issues.

doug s.

[chadh]

Doug,

Many thanks. 

The price for that unit looks pretty amazing.  But I'm a little worried about a few things for my application.  First, if I cross over at 100Hz, the powered sub will put another crossover in the system at 140Hz.  Second, I'm not really sure how decent the amp in that sub will be, nor what type of messy circuitry will be encountered.  Probably the most important issue, though, is that I've sort of set my heart on running sealed subs rather than ported ones. 

Perhaps I'm being silly, though.

I gather the fact that these are "servo subs" offers some significant benefit.  Maybe I shouldn't take this lightly.  Moreover, it's hard to imagine that I'd be able to fulfill the alternate plan for as little as $400.

Chad

[woodsyi]

Any other last minute suggestions that I should consider?

Chad

Get 4.

[doug s.]

Doug,

Many thanks. 

The price for that unit looks pretty amazing.  But I'm a little worried about a few things for my application.  First, if I cross over at 100Hz, the powered sub will put another crossover in the system at 140Hz.  Second, I'm not really sure how decent the amp in that sub will be, nor what type of messy circuitry will be encountered.  Probably the most important issue, though, is that I've sort of set my heart on running sealed subs rather than ported ones. 

Perhaps I'm being silly, though.

I gather the fact that these are "servo subs" offers some significant benefit.  Maybe I shouldn't take this lightly.  Moreover, it's hard to imagine that I'd be able to fulfill the alternate plan for as little as $400.

Chad

chad, as i said, i used the precurser yst305's, and they really are good.  setting their crossover at their highest point means they really are inwisible to the actual crossover being used; ideally, you would have that crossover set an octave lower, which would be 70hz.  tho i am certain there would be minimal (if any) issues if your crossover was set at 100.  and the main speakers won't see the sub's built-in x-over at all.  the yamaha's amp and servo are more than adequate for the low frequencies.  and, the sub has a switch for movies/music.  so you get a flatter response for music, and a bit of a boost if you have ht.

audiojerry, who used to hang here regularly, and has hi-end stuff, raved about the model below mine - the yst-sw205, which has only a single 8" driver, instead of two, like mine has.  you can read about it here:

http://www.audiocircle.com/index.php?topic=1948.0

http://www.audiocircle.com/index.php?topic=2402.msg19504#msg19504

doug s.

[doug s.]

Any other last minute suggestions that I should consider?

Chad

Get 4.

great idea - get four yammie subs, and stick the second pair near the room corners behind you, outta phase.   

doug s.

[rajacat]

Get the Rythmik servo OB sub kit with two drivers. It will be easier to construct a holder for the OB drivers than to build good sealed boxes plus IMO, they will be faster, have better resolution and go lower than the Force drivers. Later, if you want, you could add another pair for higher output.

-Roy

[chadh]

Thanks again for everyone's input.

OB subs will not really be an option, since there is absolutely no chance that these will be able to operate very far from a wall, nor is there any space to accommodate a baffle arrangement of any significant size.  On the other hand, a couple of 1.5 ft³ sealed boxes seem pretty easy to stash away reasonably close to the walls and the speakers.

For similar reasons, four subs will not really be an option for me any time soon; otherwise, I probably would have pounced on JDUBS's Swarm modules that were listed for sale recently.

Importantly, there seem to be various different schools of thought concerning bass reproduction.  I don't have enough experience with any of them to have formed a good opinion one way or another.  However, the description that usually accompanies a positive description of bass from sealed enclosures always strikes a chord with me: tight and tuneful bass, without necessarily being the last word in producing the lowest frequencies

What's the deal with "servo subs", anyway?    How do these differ from normal woofers, and does this necessarily translate into a benefit (relative to standard technology)?

Chad