Adding a powered sub to my system.

[TommyC]

Hi all. I am thinking about adding a sub to my system (listed in my sig). This is purely a 2 channel music system. I have a couple of questions.

1. Do I just get a powered sub that will accept speaker output from the Speaker 2 section of my H/K?

2. Is there one (or more) that you guys think will be the best for use with my system? Not really looking for a lot of punch as much as just expanding the range of my system a bit in the low end.

3. Can I do this for a reasonable amount of $$$? Yes, I realize that "reasonable" is very subjective, I just don't wanna spend several times the cost of my whole system on a sub.

Thanks!!

[DrWho]

Does the volume control on your HK730 control the preamp output in the back? At least I think the HK 730 amps are of the oldschool variety where they have a preamp out bridged directly over to the input for the amp on the back (any little u-shaped connectors?). If it does, then you can get any powered sub and slip in a y-adapter to send the signal to your subwoofer. Otherwise, your best bet would be to wire the amp outputs into the speaker level in's on the subwoofer. The "B" connectors would be a good way to do this (keep in mind that the B speakers are actually just outputs wired in parallel...aka, you could connect your subwoofer to your speakers in parallel and it would electrically be the same thing).

In your budget what do you consider reasonable as far as price and is DIY an option? (aka throw out some numbers) Also, what kind of music do you listen to and how loud will it be? And how low do you need to go? (I'm kinda hoping your music style will help in this regard).

I think one of your absolute best options would be to go with the THX Ultra2 dual subwoofer setup, but that might be a bit on the pricey side. I do however like the idea of a dual subwoofer setup, especially considering you're a 2-channel type of guy. Stereo bass does make a difference and the way you will be connecting your setup would makes this an easy thing to accomplish.

If you went DIY, I would suggest building a subwoofer to act as a "speaker stand" for your heresies, which would give you about 5 cubic feet per side (more than enough for a decent subwoofer). Something like the DAYTON ST385-8 15" SERIES II WOOFER would cost you about $90 each, give you 114dB of max output with a -3dB point of 26Hz. (two woofers would yield a max of 117dB which puts you right up there with your heresies max). You'd need about 500 watts per channel into 8 ohms to achieve this though (so a hefty 2 channel amp would be needed if going for stereo bass...) a single subwoofer amp rated at 500 watts into 4 ohms (250 into 8 ohms) would be more reasonable if you went with mono bass. (looking at a total cost here of around $600 fully finished).

[TommyC]

Yes, the H/K730 Has preamp outs that are controlled by the volume control.

DIY is an option, just keep in mind that I have never built anything to speak of. I have some possibilities as far as getting help, though.

Right now my budget is nonexistant due to being on limited duty and having lost all my overtime, but when things return to normal I would consider spending up to $750 or so before I would start to wonder if I were exceeding the value to my system.

I listen to pretty much everything from traditional opera to gothic metal. No Country & Western, but pretty much everything else. I notice the lack of lower octaves mostly on opera and classical, I guess.

I am a bit intrigued by the "building two and using them as stands for the Heresys" idea. That would be perfect for my space limited situation.

Thanks for the help!

[Zen Traveler]

It looks like the trip to Jeff's got the juices flowing. Good luck on the upgrade.

[TommyC]

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On 8/8/2005 5:47:02 PM tkdamerica wrote:

It looks like the trip to Jeff's got the juices flowing.

Good luck on the upgrade.

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It made me realize the limitations of my system! I am not a big fan of loud booming bass, but the ability to reproduce sounds at the very low octaves really enhances the music more than I had remembered!

[DrWho]

Wow, I think you're going to be in for a treat with the gothic metal too...I don't think I have any gothic stuff that doesn't consistantly have 30Hz material.

Since you're tight with money, you might want to hunt down someone you know that works in building houses or someone that knows someone that builds houses. They have so much extra scrap would and if you go the veneering route, you won't have to worry about the crappy look either.

If you go DIY, would it be possible to go with larger cabinets? say 6-8 cubic feet (like if you make the cabinet deeper and extend behind the heresy)? There would be a lot more drivers (costing about the same) available in that price category.

A good non-DIY route would be the Sub-12 which is a very nice not at all boomy subwoofer (that digs pretty well too). Retail is $500 from bestbuy...you could probably get two of them with your budget if you went the ebay route, though I think you would find one at least satisfactory.

[TommyC]

My stepson said the same thing. I guess I didn't know what I was missing since I have never heard any Gothic Metal on a system that can go that low.

My younger brother has offered to build the cabinets for me if I get him some plans. He is a lifelong woodworker and a Perfectionist, so I know that end is in good hands! He has several sheets of 3/4" and he thinks some 1" MDF. Suitable? If so, he said he can veneer it to match my Heresys pretty closely.

I could go deeper than the Heresys, but would like to be the same width or only slightly wider. The heresys are 13 1/4" deep and sit 11" from the wall. I can pull them out some, but not a whole lot. Any suggestions as to plans? I wouldn't know where to even begin designing something, so something proven or done by someone who knows what they are doing would be best for me.

Thanks for all the help.

[TommyC]

OK, first lesson... Don't get the woodworker involved until you are ready to go or he will drive you crazy emailing you plans he has found online and asking questions! I can already see that he is hoping for something really complicated to challenge his skills! I on the other hand am looking for something that fits in my small room and sounds good with my system!

[DrWho]

Well I wouldn't mind designing them for you if you trusted me to do that for you. I actually love designing stuff so it would be no biggy (in fact, I already have a few ideas drawn up for your sub) . I'd even be able to teach you some stuff I've picked up along the way as well.

1) I still need to know how loud you want to listen to.

2) How high off the floor do you want your tweeters to be?

3) I don't think you'll need all of those 11" behind the heresy, but would an 11" square shaped box fit, or is it 11" from the back of the heresy to the corner?

4) Will there be any furniture or stuff in the near vicinity of the speaker? (If so, I'll have to force it to be front-firing/front-ported).

There are a few other subwoofer freaks on the forum too that have built their own subs. Maybe they'll chime in and present some different viewpoints. I bet everyone of us would design very different systems, simply because we choose to compromise in different ways (though I bet the end results would all be very similar). The reason I'm asking you a bunch of questions is because I'm trying to figure out which compromises you'll find more important (ie, things like: is low end extension more important than maximum SPL?) It seems like we have the same tastes, so I'm tempted to design something that I would be satisfied with in your situation (I've got heresies and I've heard the HK so I'm familiar with your equipment too).

[TommyC]

Sounds great to me! I would appreciate all the help I can get!

1) How loud varies between "not very" when the wife is home to "Annoying the Neighbors" when she is not home. I would like something that can handle relatively low volume levels I guess, since that is what I am stuck with Most of the time. By that I mean loud enough to just strain a normal conversation. My room is on the second floor if that matters.

2) 40" to 42" would be perfect, but a little lower will work, too. 42" puts them right at ear level when seated in my favorite chair.

3) The Heresys are 11" out from the back and 12" in from the side wall and toed slightly inwards.

4) The gear rack is centered between the speakers. There is 25.5" between the rack and the speaker on either side. There is nothing in front of them.

Thanks again!

[TommyC]

My brother sent me a plan for some 6th order bandpass monstrosity that is the size of a small chest of drawers! He sounded like he is gonna build it even though it is way to big for what I want. He just thinks the woodworking involved will be interesting!

[DrWho]

Ok, let me know what you think of this:

2 x Dayton ST385-8 15" Series II ($88.95) = $177.90

6 x Precision Port 3" Flared Port Tube Kit ($12.25) = $73.50

Total = $251.40 + Tax + Shipping ( so under $350)

Then add on material costs and an amplifier.

Then have your bro build two cabinets, each should be 24" tall, 18" wide, and 20" deep. Preferably this would be the internal dimensions (so tack on an extra inch or so for the outside). I know this is a little wider than your heresy, but I think it would look better than trying to match the exact same width all the way up. If you wanted to go 15.5" side, then make it 24" deep. (basically, you can choose any dimensions as long as the cabinet is 5 cubic feet internal volume).

Now just install the 15" driver on the front baffle and install the 3" ports below the driver. It's a very tight fit so your bro will have to build this rather well. I would suggest doubling up on the wood for the front baffle (glue two pieces of the same size together) so as to reinforce the face that the driver will be mounted to. You'll also want to install cross-bracing as you see fit...at least one horizontal support, a vertical support, and a lot of bracing along the back panel.

One thing to note, which I love building into these speakers is that you can plug up one of the ports and change the tuning from roughly 25Hz down to 21Hz, which gives you some flexibility with your particular room. The 25Hz is of course more linear, but the 21Hz tuning drops off sooner but slower...depending on your room gain, you might even find the 20Hz tuning to be more linear (and the 25Hz tuning to be a bit peaky). There might be some issues with port noise at louder volumes because the air velocity in the ports will be right at 21 m/s (or 26 m/s with the lower tuning). The goal is to be below 20ms, but we're real close.

Here some pics showing the max SPL for ONE Cabinet (add 3 dB when you have both running). You'll need about 300 watts per channel to achieve these levels cleanly:

(light blue = 25Hz tuning, dark blue = 21Hz tuning)

[DrWho]

as far as amplification goes, I would look into this:

Amp350 (240 watts) ($170)

And install one in each cabinet (which will cost $340 total, yikes).

Your only other option is to look into a prosound amp, but then you will also need a crossover (which will cost you about $400 total).

If you're willing to give up true stereo bass, then you might look into purchasing just one plate amp and running the other subwoofer in parallel. (The amp350 will put out 380 watts into 4 ohms, which would be doable).

Perhaps some others can chime in about other amp options that I'm unaware of. Both QSC and Crown amps are going to cost you about $300, and then you need a crossover. I was originally going to recommend the ICBM, but I had no idea that it cost $250! It's meant for surround sound anyway, but I'm sure there's gotta be other crossovers out there...I just don't know of any.

[Scp53]

i would recommend looking at the new amps from pe. they are digital bash amps and cost 150 for the 300watt and 240 for the 500watt. you also may want to consider the quatro subwoofers from pe. i have heard many good things about them on the pe forum. just a thought.

here is a pic of my atlas 15in diy subwoofer. very potent and clean. the biggest problem is its size and weight- 120+lbs and 24in cube. im sure your will look much better with a veneer. well, i gotta go!

cheers, scp53

[DrWho]

If you wanted to save some money (and go with a more traditional look), you could build a slot port instead of using the 3 flared port tubes. The dimensions would be 18" wide, 1.25" tall (must be exactly 1.25) and then 16" long. If your cabinet ends up a bit narrower (say 15" wide), you can still get away with a 1.25" tall and 16" long port (changes the tuning from 25 to 23). So basically, you can adjust the tuning of the cabinet by making the port narrower (adding strips of wood along the sides of the port). Flaring the ends also lowers the tuning a bit so you benefit from rounding out the front edges of the port (if you want a lower tuning).

Btw, I'm personally not a fan of Bash amps, but anyone is more than welcome to try them out for themeselves.

[TommyC]

My brother is already hard at work on the cabinets! He asked if you could be more specific on the internal bracing needed.

[formica]

Heresy need subwoofers, but given their high bass roll off and relatively low maximum output (versus LaScala/Khorns for example) they are easy to match to. I used a pair with a single sealed 12" for quite a few years with good results.

Some quick points (I'm a little to late is building has started, huh?

1) I see no problems building stereo subs, but a single one would be sufficient.

2) Although I normally prefer 15" drivers... I think a single high excursion 12" would have worked. Two 15"s will simply give you a little more headroom, but take up more room.

3) I'd would have leaned toward slot port as well to try to minimize the visual impact of the sub's face versus the Heresys. Or Simply use one larger (DIY) tube port.

4) I wouldn't bother using a pro amp given your power requirements. Plate amp will avoid the noisy fan and additional x-over.

5) Adire Audio ADA series amps look real nice but are pricey. For less money, Rythmik Audio has a good reputation in the DIY community. (the Rythmik 350 is under 160$ for 350W)

enjoy...

Rob

[sfogg]

One of the benefits of having seperate subwoofer(s) with 'monitor' speakers is that you gain the advantage of being able to place the 'monitors' in the best location for imaging and the subwoofers in the best location for bass response.

When you make subwoofers the stands for the monitors you loose that advantage and instead have to find a compromised position to balance imaging with bass response.

Shawn

[DrWho]

Those rhythmic audio amps look real nice...I kinda laugh when I read the manuals though because they recommend against using certain features that were built in - so why did they even put them on in the first place? lol

Btw, I did model a few 12" drivers but didn't come across anything worthwhile. I'm sure there are options available, but I just didn't find em. Was wondering if you had any in mind.

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On 8/11/2005 3:26:13 PM sfogg wrote:

When you make subwoofers the stands for the monitors you loose that advantage and instead have to find a compromised position to balance imaging with bass response.

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Well I don't see anyone complaining about the woofer being strapped into the cornwall In fact, I would even considering stripping all the parts out of the heresy and going with a beefier 15" woofer and keeping it a 3 way design instead of this proposed 4 way...though I'm not sure if there are any 15" woofers out there that can cleanly cover 20-800Hz (not to mention more expensive). Anyways, the corner is usually a good position for a sub so I don't think too much is being lost. Worst case scenario, put the heresies back on their old stands and move the subs around independantly.

but like all things DIY, it all comes down to what you're willing to compromise.

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On 8/11/2005 1:18:56 PM TommyC wrote:

My brother is already hard at work on the cabinets! He asked if you could be more specific on the internal bracing needed.

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The general idea behind crossbracing is to reduce the size of any free vibrating face. In other words, put cross pieces extending across the cabinet centered in the middle of the panels. I usually add the bracing after I've gotten the speaker built and then I see where the vibrations are. I forget who suggested it to me, but one great way to find vibrations is to sprinkle sand on the cabinet face. The sand will jump around which means that panel is vibrating enough to warrant a brace of some sort. You don't always have to put bracing extending across the interior of the cabinet. You can just add support to the side of a cabinet face by gluing a strip of wood to the side. The better you brace the cabinet, the better your bass response will be (less energy gets wasted exciting the box, thus there is more energy going out to your ears).

[TommyC]

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On 8/11/2005 3:21:25 PM formica wrote:

Some quick points (I'm a little to late is building has started, huh?

enjoy...

Rob

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Well, so far all he has done is work out the sizes of all the panels. He said he got sidetracked by a Honey-do project for the wife so my sub cabinets are on the back burner for a bit.