Passive Sub - Build or Buy?

[hydroman]

Heres the thing, when i finally have my H/K AVR635 reciever - i won't need my NAD amp. So i plan to use it to power a sub. (I plan to keep the pre-amp to use as a pre amp (only) for the future turntable)

I find very few passive subs out there (vast majority are powered).

The plan is to buy a 12" driver and built a sealed enclosure (simple) and use a passive crossover - with a variable capacitor to tune it.

Once i select a driver i will determine the amount of interior volume.

Comments? Suggestions?

[Mr Peabody]

First, build or buy, unless the driver you pick comes with specific box specs, or the specs obtained somewhere, I vote buy. There is a lot to a speaker cabinet design and matching it to a driver, it's best left to those with the expertise. If your sub is for HT only and you use LFE out, you shouldn't need a crossover in the box. Even for music many of the receivers have bass management that would negate having to deal with a crossover, that's a plus for he DIY.

Personally, I'd buy a powered sub and use your NAD somewhere else. Today's powered subs are loaded with features you won't be able to take advantage of, like auto on/off, phase switch, some even have servo control and equalization.

[cjpremierfour]

You can find many 12" Subwoofer drivers at places like Partsexpress, Madisound, Adire Audio and Meniscus. You may want to determine the Output wattage of your NAD amp and what ohm rating it will handle. You may find it best to run a dual voice coil subwoofer or even (2) 12" subwoofers for a stereo mode.
Just an example from Partsexpress. They sell a 12" Dayton Dual Voice coil ( Dual 8 ohm ) subwoofer DVC310-88.-$110.00 / Dayton DVC310 Passive Radiator -$65.00

It all depends on what you are wanting, your budget, how large you can build you box and your wattage from your Nad amp.

You may want to check these out:
Peerless extra long stroke 12" -$196.00 also needs the Passive Radiator 12"XLS 425g-$106.00
MAD 1259 formerly NHT 1259 12" -$150.00
Adire Audio's Tumult 12" D2/D4 is a super woofer that need lots of power-$650.00
Dayton High Fidelity/ High Output/ Titanic Mk3 line-$130.00 to $160.00
Meniscus 12" Sealed Box Subwoofer SW1284-$150.00 (** can't find much on this woofer but Meniscus calls it the best 12" sub on the Planet??? )
Dayton Quatro QT305-4 high SPL for low to mid wattage amps -$75.00

I have had good experience with both Peerless and Dayton subs, for the money you really can't beat Dayton, it's just a great company.
Hope this gets you started,
Good Luck

[Dusty Chalk]

Buy -- unless you have experience making inert subwoofer boxes.

[SlumpBuster]

Mr. Peabody makes a compelling argument. While the HK is a nice receiver, that Nad amp is a beast. I would still use the Nad to power the Acoustic Energy speakers and get a powered sub.

My recs on subs include: Parts Express Dayton Titanic, SVS, and HSU.

[kelsci]

I did an experiment for awhile along this avenue. I have a NAD 3040PE integrated amp that has pre-outs and power amp. inputs in the rear. I had two 10inch radio shack 50 or 60 watt dual voice coil subwoofers that I got cheap many years ago on a closeout. I put these subs into two Marantz Imperial 6G cabinets. I was using the sub-output of a Sherwood 6095R with speakers set to small. The receiver does the bass management needed for passive sub operation which is described perfectly by MR. PEABODY. I adjusted the sub-out volume control until I felt I had hit a level of blend.

At first, I hooked up the NAD to each of the voice coils one of of the subs. Each voice coil was 4 ohms, easy for the NAD to handle. I just did not like the sound feed. So I hooked up the NAD to each speaker cabinet so in essence I had two subs going. This did work very well to an extent. Of course, every time you have to turn on the receiver, you must turn on the NAD, sort of a pain in the ass. I thought that in the end I needed more power, a more passive subwoofer dedicated cabinet, and better passive subwoofers to make this worthwhile. The reason why I say this I will describe now.

My brother gave me his Klipsch SW-10-2.. Although I lost the use of two subs, this one sub gave me a more theater like bass response on movies and a good enough performance on music. I found it easier to blend with the controls on the subs rear from the position I had that sub in. So I give thumbs up to a separate powered sub over the passive system and agree with Mr. Peabody on this matter.

You might want to try E-bay and type in the search column Passive Subwoofer. If I were to use a NAD 2200 power amp, I might want to consider using a Optimus passive subwoofer that is downfiring. They appear on occassion on E-bay. You would hook up the left-right speaker outputs of the 2200 to the left-right speaker inputs of this particular sub.

I do not recall if the 2200 bridges. If it does, I believe you have to use an 8 ohm impedance speaker and as such you would have to use a 8 ohm passive subwoofer. I would be sure that 8 ohm passive raw subs are available before getting the appropriate cabinet needed for the sub.

[JeffKnob]

I would definitely go with a DIY passive subwoofer. There is much more bang for your buck that way. You already have a great amp with your NAD. I have a passive subwoofer setup right now. I doubt I will ever buy a powered subwoofer made by some company. I can get 110db at 20hz without room gain. It is closer to 120db at 50hz with no room gain. Not too bad for a $150 driver and 2 $90 passive radiators.

[Florian]

I would definitely go with a DIY passive subwoofer. There is much more bang for your buck that way. You already have a great amp with your NAD. I have a passive subwoofer setup right now. I doubt I will ever buy a powered subwoofer made by some company. I can get 110db at 20hz without room gain. It is closer to 120db at 50hz with no room gain. Not too bad for a $150 driver and 2 $90 passive radiators.

I would be interested in the dimensions, throw ability of the driver, amplifiers, crossover and measurement data if you please. What did you use for RTA device and at what distance was it measured.

Thanks in advance

Florian

PS: I suggest "buy"....look into a used Velodyne HGS or new DD Series with room adaption.

[N. Abstentia]

I vote for buying a nice active sub and using your reciever as a preamp. Your NAD amp will destroy the amp in that H/K reciever.

[Rock789]

I will agree with the few in this thread and say build it...
if nothing else, it is fun!

I have built a couple subs, and plan to build another in a month or so along with some beginner towers... (we will see how far I get in a month with work...lol)

how much do you want to spend and how much do you want to do from scratch?
Parts express has sub cab's if you don't have the time or equipment to build on your own...

goodluck with whatever you decide...
btw, if you decide to purchase a powered sub... check out the titanic kits at partsexpress...

Kex has tons of diy info, I am sure he will chime in here soon...

[Feanor]

Heres the thing, when i finally have my H/K AVR635 reciever - i won't need my NAD amp. So i plan to use it to power a sub. (I plan to keep the pre-amp to use as a pre amp (only) for the future turntable)

I find very few passive subs out there (vast majority are powered).

The plan is to buy a 12" driver and built a sealed enclosure (simple) and use a passive crossover - with a variable capacitor to tune it.

Once i select a driver i will determine the amount of interior volume.

Comments? Suggestions?

hydroman,

First, I assume you expedt drive your NAD amp from the 'Sub' or 'LFE' preamp of your receiver. Assuming so, is you NAD bridgable to mono? If not, you have to decide whether you are going to use only one channel or both. In the latter case you can use a 'Y' connector from the sub-out to drive both channels, then you will need a dual voice coil driver for the sub in order to utilize both channels from the NAD.

Of course, there are plenty of free box design programs that you can use to design your box. A sealed box design is much less critical as to exact size than a ported box, so sealed box is good idea for the new builder -- I'd do that since I'm not highly experienced myself.

For my own needs, I'd probably go with a Dayton (Parts Express) Reference High Fidelity driver. But note that this isn't dual coil ...
http://www.partsexpress.com/pe/pshow...number=295-464

[JeffKnob]

I would be interested in the dimensions, throw ability of the driver, amplifiers, crossover and measurement data if you please. What did you use for RTA device and at what distance was it measured.

Thanks in advance

Florian

PS: I suggest "buy"....look into a used Velodyne HGS or new DD Series with room adaption.

My sub was modeled in WinISD by myself and Pete Schumacher at diysubwoofers.org. With room gain Pete expects I could get 116db at 20hz including room gain . I also have a BFD to level out any of the issues with the room.

The plans for this subwoofer were are also designed by Adire Audio, who manufactured the driver and passives.

Here are the specs for the driver and passives.

Tempest Classic 15"
Overall Dia.: 15-3/16"
Cutout: 13-15/16"
Front Mount Height: 3/4"
Mount Depth: 6-13/16"
Displacement: 5 liters

Specs taken with voice coils in parallel.
Re 3.5 ohms
Le 2.9 mH
Qms 6.7
Mms 195 grams
Qes .40
Cms 0.374 mm/N
Qts .39
Fs 18.8 Hz
Sd 779 cm^2
Vas 317 liters
BL 14.2 N/A
Xmax 16.4 mm one way
EBP 47
SPL 89.1 dB @ 1W/1m
VC Dia. 2-1/2"
Power Rating 750W total


Two PR15 Passives

Nominal Size15"
External Diameter 15.25"
Cutout Diameter 14"
SD 824 cm^2
Moving Mass 285 grams (max: 1500 grams)
Rms 3.5 N*s/m
Fp 8.2 Hz
Qms 5.39
Vap 1187 liters
Cms 1.25 mm/N
Rms 2.87 kg/s
Xmax 31mm one way
Vd 5.1 liters (total)

Text from the plans. There are diagrams as well in the pdf.

3.2 SBB4 Design
The SBB4 design for Tempest (Q=0.707) is a traditional Super Boom Box 4th order. This alignment provides the flattest bandwidth extension, without any peaks
in the response. This alignment is arguably the most popular of all Passive Radiator alignments, because it promises extended bass response (down to the 20 Hz
range) with good transient response (less than 23 ms of group delay at 20 Hz). While not having the extreme-low group delay “tight sound” of the other Passive
Radiator designs, it does have considerable midbass punch and output, making it well suited for home theater applications
The SBB4 design is a net 194L cabinet, tuned to 18.8 Hz. It is stuffed with 64 ounces of polyfill. It’s external dimensions are 30.25” tall, 24” wide, and 24”
deep. This includes the height from 4” tall legs. It is tuned with a pair of our PR-15 passive radiators, each loaded with 483 grams of mass. The Tempest is
bottom mounted, downfiring. The passive radiators are mounted on the sides, out-firing. Braces are used to stiffen the cabinet, and keep the widest panel span to
a very good 10.75” or less. Recommended building materials are void free plywood (such as marine ply, apple ply, or baltic birch), MDF, and particleboard, in
that order.

[hydroman]

WoW! What great info! I came to the right place...

Okay - the NAD is bridgeable and puts out AFAIK ~500W Bridged Mono (Stable into 4 Ohms (IIRC))

The NAD over-powered the Aegis speakers - the H/K should match them better - letting me fill the room in big bass (that the Aegis falls down on...)

I chose a sealed box knowing it is ever so much more tricky to do the ported enclosures.

Good ideas for the drivers. I think after considering all the great input - i will go for DIY downward firing sub - using the sub output from the reciever (and let it 'auto set up' with it first - and tweak as needed). I might use a preffab cabinet if cheap enough (less than $100).

The Jeffknob solution looks mighty do-able.

Yeah! A good project - on the budget...

[AmpItUP]

I agree with Mr. Peabody, buy instead of build.

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