Critique my sub plans

[eyekode]

The goals for my project are not too aggressive:
100 db @ 20hz and accurate
relatively flat in-room response
< 500 watts from the wall
small footprint
inexpensive
room to grow

I don't get to listen loud very often (many small children in my house . So I don't need high spl. But I do like accurate sound. Also my listening/viewing area is width constrained but I really like the room layout so I don't want to change it.

The room is rather large (19x18x9 1/2 ceilings with a large open hallway walls are sheetrock, floor is over garage). So I don't think I will get huge room gain.

I am constrained to 500w from the wall because I have one 15 amp circuit and already have a 50" plasma (up to 400w peak) a reciever (up to 700w from the wall peak), 3 computers (up to 800w from the wall), various other small electronics. The only saving grace is that while watching/listening 2 of the computers are typically not loaded. I am probably drastically overestimating the current draw here because I have had everything running at the same time _and_ a vacuum cleaner and I did not flip the breaker.

Due to room layout the best place for the sub(s) will be beside the entertainment center as speaker stands for my Cryolite DIY speakers.

So my current plan is:

Build 2 16.5x16.5x21 boxes (finished height will be 24").
Use one Dayton RSS390HF-4 driver in a sealed alignment ( the box works out to be ~2.5 ft^2).
Build a Linkwitz transform circuit. I figure it will steal 8db of headroom.

Using WinISD it looks like I will need ~125watts to get to 100db (assuming 3db room gain at 20Hz).

I will amp it with a Rotel amp that I have lying around.

If I need more SPL I figure I can:
Add another RSS390HF-4 to the other enclosure (will add 3db gain)
Increase amp to 500w (6db gain)


So if needed this setup can grow to 109db at 20hz.

Cost projection:
RSS390HF-4 170
Box materials 130
Linkwitz xform 50 (built myself using breadboard and Elliot's nice webpage)
Total: 350

Add eq? Behringer BFD 100

Cost to add second driver? 170

Cost to increase amp? Behringer EP2400 280 (might not be able to do this due to wall power constraints)

Full final cost: 900

I like this plan cause it should sound good and allow me to build it incrementally from a cost perspective.

What do you think? This is the first time I have built a sub. But I can do electronics and I have also built Lou's Cryolite bookshelf speakers.

Am I missing something? Is there a better way to achieve my goals?
Thanks!
Salem

[eyekode]

Taking another look at the speaker choice, it might be a better idea for me to go with a RSS315HF-4. Only issue is if I have enough Sd * Xmax for my goal... time to do more math.

[SLAYER]

Hi eyekode, welcome to the shack.
seems like a good sub build to me.
i myself will build my next sub as main stands, although im shooting for 7cubic or so
tuned @20 hertz .
and am wondering if it would be a issue for you to do a bigger box as it would allow you more head room and use less power to achieve what you want , im sure other more experienced users will chime in.

ps: not sure if you know this but parts express has a 240 watt dayton plate amp @ $130.00

[eyekode]

SLAYER wrote:

Hi eyekode, welcome to the shack.
seems like a good sub build to me.
i myself will build my next sub as main stands, although im shooting for 7cubic or so
tuned @20 hertz .
and am wondering if it would be a issue for you to do a bigger box as it would allow you more head room and use less power to achieve what you want , im sure other more experienced users will chime in.

ps: not sure if you know this but parts express has a 240 watt dayton plate amp @ $130.00

7 cubes is much closer to what these drivers like. But I don't see how I could make stands that big. I don't want them much wider then 17". The wall I have my HT setup against is only wide enough for my entertainment center (67") and 2x17" wide stands. And that is pushing it cause it almost obstructs a door! And for speaker stands 24" high is what I need. Leaving clearance for a down-firing sub that gives me 21" high. So ignoring the thickness of the material and the volume of the driver that would mean 58" deep for 7 cubes! If I didn't have a width restriction I could do ~30x30x21. But that is really a strange shape.

I agree it would be better to have more volume. But I think I can reach my goals with the smaller sub with a linkwitz transform and I just don't have the space.

But maybe I should forget about down-firing and that will let me increase the volume a little. I wonder if facing the driver backward would be a big deal? I was trying to keep the drivers out of sight (thus down-firing). I _know_ my 3 little monkeys would love to poke holes in huge drivers!

Thanks for the feedback!

[imbeaujp]

Hello, I just completed a similar project : 2 subs 16.5 x 16.5 x16.5 with peerless XXLS 12 drivers and passive radiators.

You can see the building tread HERE

The sound is verry nice, precise, not boomy. I got a BFD to equalize but in my actual room, i do not need any EQ after some speaker placement.

You can see the measuring thread HERE

Good luck !

JP

[eyekode]

imbeaujp wrote:

Hello, I just completed a similar project : 2 subs 16.5 x 16.5 x16.5 with peerless XXLS 12 drivers and passive radiators.

You can see the building tread HERE

The sound is verry nice, precise, not boomy. I got a BFD to equalize but in my actual room, i do not need any EQ after some speaker placement.

You can see the measuring thread HERE

Good luck !

JP

Wow, that looks good! The price is a little high for me but the size of the enclosures is amazingly small. Your room must really be helping you down low. What spl can you reach @20Hz?

[brent_s]

IMO, the 390-HO would be a better option than the HF for a 2.5 ft^3 box. No driver benefits from down firing, some just suffer less than others...the 390s are in the suffer more category. The 315-HF is also a valid option in that size box.

You might also check with John at AESpeakers to see if he has any more of the 15.1 closeouts left. 23mm Xmax for $125. One of our members is happily using these in 3 ft^3 sealed.

If ported is an option, I'd suggest the RS315-HO tuned to 21ish Hz via a port or the PE 15" DVC based passiver radiator in 2.5 ft^3 net. The PR should allow the overall box to be a bit smaller with less gross volume consumed by the port. With the PR, 125 watts gets you 101.5 - 105 dB from 20-100hz ground plane...no L-T required.

Unless you've already measured, I think you'll find more than 3dB of room gain at 20hz. Don't forget boundary gain as well; it's a theoretical +6dB per boundary across the entire passband. In my room, I'm getting 7-10dB of gain at 20hz measured versus the WinISD models.

For major power on the cheap, contact Jack here. While supplies last, but you won't find 500 watts for less. He's a member here as well.

-Brent

[imbeaujp]

eyekode wrote:

What spl can you reach @20Hz?

Hello, it is around 96db with a sine wave at 20hz and mesured the RadioShack SPL model 4050 (with 5.56 db correction) at listening position. I think that I could pump up my amp a little more...

Anyway it is fairly enough !

My room is verry large as you can see in the pictures, and I think you will get better results in a smaller room.

JP

[eyekode]

brent_s wrote:

IMO, the 390-HO would be a better option than the HF for a 2.5 ft^3 box. No driver benefits from down firing, some just suffer less than others...the 390s are in the suffer more category. The 315-HF is also a valid option in that size box.

You might also check with John at AESpeakers to see if he has any more of the 15.1 closeouts left. 23mm Xmax for $125. One of our members is happily using these in 3 ft^3 sealed.

If ported is an option, I'd suggest the RS315-HO tuned to 21ish Hz via a port or the PE 15" DVC based passiver radiator in 2.5 ft^3 net. The PR should allow the overall box to be a bit smaller with less gross volume consumed by the port. With the PR, 125 watts gets you 101.5 - 105 dB from 20-100hz ground plane...no L-T required.

Unless you've already measured, I think you'll find more than 3dB of room gain at 20hz. Don't forget boundary gain as well; it's a theoretical +6dB per boundary across the entire passband. In my room, I'm getting 7-10dB of gain at 20hz measured versus the WinISD models.

For major power on the cheap, contact Jack here. While supplies last, but you won't find 500 watts for less. He's a member here as well.

-Brent

Brent,
Thanks for the info! Those are a bunch of options. I really don't want to go any bigger. I haven't thought much about a passive radiator though. I guess I would be concerned with stored energy. Just from the physics of it wouldn't a radiator "ring" and to some degree attempt to drive the driver... almost like intermodulation?

I know down-firing isn't the best. Do you think it would matter if I faced the driver backward? I have 3.5 kids. The old one is 4.5. So I _know_ if I expose a 15" drum one of them is going to bang it .

About the room gain it was just a guess. Not even an educated one . I just
figured that the size of my room is relatively large...

I modeled a 315-HF ported. But to get a 3db at 20Hz required 4 cubic feet. I haven't modeled the HO, I will give that a shot.

It sounds like you are really against doing an LT. It seemed to me to be the best for a small enclosure considering room gain. The sealed enclosure has such a shallow slope.

I had not heard of the AESpeakers deal. I will do some searches. How can I contact John?

Thanks again!

[eyekode]

eyekode wrote:

I had not heard of the AESpeakers deal. I will do some searches. How can I contact John?

Nevermind, google showed me the way: http://www.aespeakers.com/phpbb2/vie...9bd4692b0c42f8

[eyekode]

Ok, after running some numbers I think I understand Vas a little better . I had been using WinISD and I switched to WinISD Pro. Much improved. Somehow I had missed how high the Vas is with the HF drivers.

Although I would prefer the smaller size and volume requirements of the 12", it would leave me really not much headroom at 20Hz. Going for the 390HO would leave tons of room for improvement. And it would let me shrink the volume a little bit.

So, revised plan:
390HO in 2.3 cubes. 3db of eq + 6db of room gain should get me pretty flat out to 20Hz. And it looks like 180w is sufficient to fully use the Xmax. And if the 6db of room gain is right then I only need 22.5w to reach my 100db target. That sounds too low though... WinISD Pro is showing 180w to reach 103db @20Hz. If I am assuming 6db room gain, then it would be 109db. And 1/8th of the power brings it down to 100db. But that is only 180/8 = 22.5w. Anyone care to sanity check my math?

I also revised my box plans. Down-firing just has too many compromises. I will go front firing with a grill.

Thanks again for everyone's feedback!

[brent_s]

I haven't thought much about a passive radiator though. I guess I would be concerned with stored energy. Just from the physics of it wouldn't a radiator "ring" and to some degree attempt to drive the driver... almost like intermodulation?

PR's are considered bass reflex alignments, just like a traditional port. Output drops off a bit faster below tuning than a traditional ported box of the same volume and tuning. No worries about port noise. More expensive to build, but the most space efficient way to tune a small cabinet to a low frequency.

Do you think it would matter if I faced the driver backward?

It would be no different than downfiring, all things being equal (distance to wall/floor and crossover frequency). Maybe slight variations if your floor is carpeted, etc. Forward with a grill should be the gold standard.

It sounds like you are really against doing an LT. It seemed to me to be the best for a small enclosure considering room gain. The sealed enclosure has such a shallow slope.

Nothing personal against LTs, or any other alignment. I just like to try to find "natural" solutions that will accomplish my design goals. For instance, I don't like to count on enclosure stuffing to allow me to build a smaller than optimum sealed box, either. Just personal preference, KISS principle, whatever you want to call it.

So, revised plan:
390HO in 2.3 cubes. 3db of eq + 6db of room gain should get me pretty flat out to 20Hz. And it looks like 180w is sufficient to fully use the Xmax. And if the 6db of room gain is right then I only need 22.5w to reach my 100db target. That sounds too low though... WinISD Pro is showing 180w to reach 103db @20Hz. If I am assuming 6db room gain, then it would be 109db. And 1/8th of the power brings it down to 100db. But that is only 180/8 = 22.5w. Anyone care to sanity check my math?

WinISD seems to calculate SPL/Excursion etc. by adjusting the specified "system input power" by the amount of boost added by your LT, but there's nothing to indicate how much power the driver is then receiving in the model. Apparently, the assumption is made that your amp can deliver the additional power needed above the input power specified...this might even be in the Help file, but I haven't looked. Regardless of EQ, SPL is a function of cone travel and cone travel is a function of input power. So, with a bit of playing with EQ/No-EQ models, you can determine how much power is actually needed from your amp.

My WinISD Pro v.50a7 model of the 390HO in 2.3 ft^3 sealed with no EQ has a Qtc of .661. With 180watts at 20hz, SPL is 97.06 dB at 1m and excursion is 8.4mm. Excursion limited power is 365 watts. If I use 180 watts as the input power with 3dB of boost at 20hz (PEQ 20hz/+3dB/Q=.1), WinISD will then show 100.06dB/11.9mm at 20hz since +3dB requires 2x power. I think you're assuming WinISD is including the +3dB in your 180 watt input when it's really just the baseline that the boost is then applied to.

-Brent

[brent_s]

2nd post to avoid making that last post even longer.

You might also want to take a look at Rythmik Audio's kits. The 12" works in 2 ft^3 sealed and the 15" will go as small as 3 ft^3. A pair will exceed your budget just a bit, but Brian's essentially done the heavy lifting for you in providing EQ and amplifier power tuned specifically for the driver. Ilkka tested a DS12 kit earlier this year. Take note that his measurements are at 2m, not the 1m default of WinISD simulations.

Standard disclaimer: I (nor the Shack, that I know of) have no affiliation with Rythmik Audio. I've simply read good things about their products from customers and they do seem to be a good compact solution based on Ilkka's testing.

-Brent

[eyekode]

brent_s wrote:

My WinISD Pro v.50a7 model of the 390HO in 2.3 ft^3 sealed with no EQ has a Qtc of .661. With 180watts at 20hz, SPL is 97.06 dB at 1m and excursion is 8.4mm. Excursion limited power is 365 watts. If I use 180 watts as the input power with 3dB of boost at 20hz (PEQ 20hz/+3dB/Q=.1), WinISD will then show 100.06dB/11.9mm at 20hz since +3dB requires 2x power. I think you're assuming WinISD is including the +3dB in your 180 watt input when it's really just the baseline that the boost is then applied to.

-Brent

Brent,
Your numbers sound closer to correct to me. I was not adding room gain or any filter in WinISD. But looking at my numbers they are a full 6db higher then yours. Maybe I messed up the parameter entry for the 390HO. I am getting a qtc of .657. I am guessing I have Sd wrong. I have the diameter as 380mm. Maybe your number is taking into account for the surround? But I guess that isn't enough of a difference to really matter... I am running the same version of WinISD.

[eyekode]

brent_s wrote:

2nd post to avoid making that last post even longer.

You might also want to take a look at Rythmik Audio's kits. The 12" works in 2 ft^3 sealed and the 15" will go as small as 3 ft^3. A pair will exceed your budget just a bit, but Brian's essentially done the heavy lifting for you in providing EQ and amplifier power tuned specifically for the driver. Ilkka tested a DS12 kit earlier this year. Take note that his measurements are at 2m, not the 1m default of WinISD simulations.

Standard disclaimer: I (nor the Shack, that I know of) have no affiliation with Rythmik Audio. I've simply read good things about their products from customers and they do seem to be a good compact solution based on Ilkka's testing.

-Brent

I had seen these subs. They are what got me thinking about an LT. One thing I like about doing it myself is I can spread the expense out incrementally. For example I can first build just the sub. I already have an amp I can use. If it is sufficient, then I can stop there. Otherwise I can add some eq. And if that fails I can add an LT circuit. I say I want 100db at 20Hz... but I don't really know what that feels like . So being able to do it incrementally is a big benefit for me.

Thanks for posting the link to that test. It is very well done. It is the first time I have seen thd charts for subs. So honestly I don't even know if they are "good". I will look around for some comparisons.

Thanks again for the sanity check on my math and all the good links!
Salem

[brent_s]

I'm using an Sd of 804.2 cm^2, which it looks like I got by using the D=320mm from the exported Clio measurements on PE's page for the 390HO.

Either the BFD or FBQ (can't remember which) can mimic an LT if the filters are configured correctly, so there's another possibility for your incremental build plan.

If you want to take a drive down to the Port City, I could demo 100dB@20hz for you. We usually watch movies at -13 to Reference Level, unless they're recorded "hot" (not a lot of dynamic range), then we turn them down a bit because that much SPL gets fatigueing after a while. That level is good for in room peaks of 95ish dB, all channels on, according to the Radio Shack analog SPL meter...or about the same as your typical gasoline push mower. It's still enough SPL for the bass tremors to make downstairs wall hung artwork vibrate 30-40' from the sub's location. And the sub's in a dedicated theater room which is just a 24x16x9 FROG which was finished after the main house so even the common wall to the main house is fully insulated, including an exterior grade door.

My living room system actually has subs similar to what you're proposing. I'm running a pair of NHT1259's sealed in 2.8 ft^3 each. These are '94 vintage original NHT, not Madisound's clones, back when Ken Kantor/NHT was releasing some of their own QA'd stock to the DIY community via a couple of distributors. My theater sub is a PE DVC15 in 5.9 ft^3 net, tuned to 17hz. If you look at a WinISD model of either the NHT1259 or DVC15, you'll see they're -10/-7 respectively at 20hz. However, with room gain, they both measured flat at 20hz using REW in the theater room. I haven't measured the 1259s in the living room, which is a much larger and acousticly reflective space. With a 100dB test sweep, the DVC15 measures essentially flat down to 10hz.

-Brent

[eyekode]

I'm using an Sd of 804.2 cm^2, which it looks like I got by using the D=320mm from the exported Clio measurements on PE's page for the 390HO.

Oh baud... how did I get 380? Maybe that is for some 18" I was playing with...

If you want to take a drive down to the Port City, I could demo 100dB@20hz for you. We usually watch movies at -13 to Reference Level, unless they're recorded "hot" (not a lot of dynamic range), then we turn them down a bit because that much SPL gets fatigueing after a while. That level is good for in room peaks of 95ish dB, all channels on, according to the Radio Shack analog SPL meter...or about the same as your typical gasoline push mower. It's still enough SPL for the bass tremors to make downstairs wall hung artwork vibrate 30-40' from the sub's location. And the sub's in a dedicated theater room which is just a 24x16x9 FROG which was finished after the main house so even the common wall to the main house is fully insulated, including an exterior grade door.

Woah, you are just down the road .

My living room system actually has subs similar to what you're proposing. I'm running a pair of NHT1259's sealed in 2.8 ft^3 each. These are '94 vintage original NHT, not Madisound's clones, back when Ken Kantor/NHT was releasing some of their own QA'd stock to the DIY community via a couple of distributors. My theater sub is a PE DVC15 in 5.9 ft^3 net, tuned to 17hz. If you look at a WinISD model of either the NHT1259 or DVC15, you'll see they're -10/-7 respectively at 20hz. However, with room gain, they both measured flat at 20hz using REW in the theater room. I haven't measured the 1259s in the living room, which is a much larger and acousticly reflective space. With a 100dB test sweep, the DVC15 measures essentially flat down to 10hz.

Thanks, that is really useful info. Room gain is hard to estimate so it is nice to see some real numbers.

Thanks again!

[brent_s]

eyekode wrote:

Woah, you are just down the road .

Kinda why I made the offer.