The "designing the perfect subwoofer driver" thread... (1 Viewer)

[Dustin B]

Are you assuming a straight out doubling of power for the dual driver spl numbers?

If so I'd very much like to see a little bit larger than 3ft^2 box in order to gain back some effiency. Needing two RMX1450 or M1400 amps ups the cost very quickly. $500 on drivers and $800 on amps adds up fast.

 

[Carl_Berg]

I found all this really interesting, all the way up until...
Dan Wiggin's last input. 105 db anechoic at 20hz with 1400 watts. Now granted this is in 3 cu. ft - so pretty small. But if you are willing to go a tad larger say 5 cu ft. than why not do this.
Maelstrom:
"Capable of over 105 dB SPL anechoically at 20 Hz, Maelstrom can reach well beyond 115 dB SPL at 20 Hz, in-room, in a sealed box. No longer must the decision be vented for SPL, or sealed for tightness. Now you can have both with a single driver. And thanks to the low Q, such performance can be reached in a simple 22" cube."
Above directly out of Adire's Website (also what I built 2 of)
Not only this, it can be done with a mere fraction of watts.
I just got done building 2 of these, I can stack them in a corner or move them individually about.
I can absolutely shake the living daylights out of my house with 10 and 12.5 Hz sine or warble tones off the Stryke test CD.(makes my 10 month old daughter cry... :frowning: even when she is way way far away...
I do not have any EQ supplied... yet...
Not only that - about the same cost as what is being talked about here except can be driven by adire's 250 watt plate amp almost to x max anyway for cheap.
I have mine driven by at this moment a parasound 2003a (300 watts or so 4 ohm) and they absolutely rock. Q ~.6, stuffed with currently 5lbs of polyfill each.
I just couldn't help but laugh when it got to this far. Am I missing something? Am I off my rocker here. Granted 3 cu. ft. is considerably smaller, the F3 is lower and you could EQ it more to flatten it out, but the end result is 105 anechoic at 20 hz. Which you get with a Maelstrom, without EQ but with the trade off of larger size.
Now this is my first project, and I would consider myself a newbie, but this almost seems addressed already.
Please help inform me...
C.

 

[Dustin B]

Good point Carl.

11 ft^3, $600 for drivers, plus $300 for amp

vs

6 ft^3, $500-$600 for drivers, plus $800+ for amps

If it results in the same SPL capability I know which way I would be going.

 

[Brian Bunge]

Well, I might be able to handle 5ft^3 sealed but it would have to be 4ft^3 plus a buttload of stuffing to get there. I'm really quite happier with the size of 3ft^3 though. Like I said before, I'm really looking at an endtable style sub. I like real wood finishes as opposed to tall columns with fabric on them in my living room. Just too contemporary for my tastes. I don't mind dropping a grand on a K2 either as I know any fan noise would drive me nuts. I returned a Denon 3300 because the damn thing was clicking all the time! Didn't sound very good anyway, but that's another thread! I'd get a Samson amp since I hear the fan is usually very quiet if they could handle a 4-ohm load.

I am interested in hearing what Dan and Jack have to say about all this.

Brian

 

[Carl_Berg]

Hi Brian,

I did what you are talking about, not sono tube style (not that their's anything wrong with that). I also have a TN1220 so been there done that, now trying to get rid of that... However I built these as stereo Bass enhance subs for my lex. Still leaves me with an eventual need of a LFE sub. I could easily see doing a Tube-zilla aka thomasW style but from what was just stated as output with kilowatt+ amps, I don't see that as being the answer yet. I hope to be proven wrong. ( I can set my subs up like this as it is anyway - stacked, drivers counter acting each other and drivers facing each other even).

Any way you cut it, I personally prefer sealed. Way easy to build, good transient reponse, good room interaction to yield flat output over usable range, low group delay, ease of achieving low to mid Q (I prefer ~.55-.65 give or take), no port compression or noise, simplicity, low cost, no passive radiator tuning to get right, - which I probably won't or won't have patience too, no passive radiator expense, and lastly when bottom mounted you don't see a driver, port, or passive radiator. (personally I like to see the driver but I have a little one that I just know will get big enough soon to think pushing a dustcap flat is "cool". Let alone my wife likes the effect of subwoofin just not the look. (wish I could do an IB just no area to use as an enclosure). Maybe if I sealed off the babies room and used that as the enclosure... nah, never mind...

Anyhow my subs are a tad larger than 22x22 (mine are 22x23.5)with 5 inch legs.

End table, sure works for me. As long as I don't mind anything I put on it dancing off it. (actually don't know if this would happen or not. These things are pretty dead as well as weigh about 100 lbs a pop).

Again, just my thoughts. If we could get a 15" in 3 cu ft, and yield 110db anechoic with 1.5KW than yeah, tube zilla here I come. Till then I'll wait - I'm in no big rush.

C.

 

[Jack Gilvey]

Well, here what I come up with for the proposed 15" driver compared to Maelstrom.

A basic Vd comparison gives a large edge to the 15" driver. Maelstrom displaces just over 3 liters, while the 15" has a Vd of (750cm^2 Sd x 70mm P-P Xmax) 5.3 liters, a not inconsiderable advantage which would seem to indicate the 15" is capable of a good deal more output regardless of box size or power input considerations.

Also, if I understand XBL2 correctly, the 15" is likely to remain more linear and lower in distortion than the Maelstrom as they approach their maxima.

A quick 'n dirty Unibox with each driver in Qtc =~.7 cabs shows the 15" to have a far lower F3/Fc (by almost an octave,49Hz vs. 27Hz). In larger cabs, the Fc will go down but F3 will go up.

Output is dependent on linear excursion, and so is more-or-less independant of box size, so I just noted the SPL at 20Hz when the driver reached Xmax. The Maelstrom reached 104dB at Xmax, and the 15" driver produced 109-110db (I had to extrapolate a bit as Unibox only measures up to 30mm) at Xmax, both anechoic. The 15" driver took lots more power to reach these levels, approx 1500w in 3ft^3. As I noted, I think the 15" will be much cleaner at and approaching these levels.

Anyway, that's what I get...I hope I got all the numbers right.

 

[Jeff Rosz]

thanks to brian and jack for the links. the spreadsheet really makes it easy. gotta love op amps. one of man's 3 greatest inventions. jack, a circuit board for a kit would be pretty easy to design and parts would be cheap. the hard part is getting the component values as close to off-the-shelf values as possible with as little gang soldering as possible. gimmie about a week and i'll have a circuit board. if you want all the elements (buffer,subsonic,var gain) you see on the spreadsheet, a bit longer.
btw, silkscreen is the white lettering you see on almost every cicuit board. but that can be done in copper with an etch resist pen or written directly on the circuit board after its etched with a fine magic marker. but really, dont sweat the little stuff.
lates

 

[Hank Frankenberg]

This baby just got too expensive, as Carl pointed out. Dan, please don't go for absolute smallest sealed enclosure application - that requires too many power amp dollars.

Jeff, I'm a solder-slinger from way back. If you've got a PCB layout program, I may be able to get a PCB shop to make a batch of boards. I could commit to buying the PCB's if I could get enough committments from folks to buy assembled boards from me. That leave the enclosure, power supply (wall wart?), RCA jacks, etc though.

 

[Brian Bunge]

that requires too many power amp dollars.

Dan,
Don't listen to Hank! I want the 3ft^3 enclosure with the 1400W+ amp! Hank's happy with his Tempest so we don't need his input on this!
Brian

 

[Jeff Rosz]

cool hank,

sounds like a plan. gotta love austin, tx. the circuit board capitol of the world. we need a new thread so we dont clutter up jack and dan's new driver thread.

gotta go to work now

lates

jeff "gotta love me" roszkowski

 

[Carl_Berg]

Hi Jack,

Interesting observations, was this model using the specs in dans note? If so why the discrepency of output vs. what dan had projected. Can you give more details? Also without having to redo your model - what size cabinet was used for each?

Also a Q of .7 I would presume to be not what the majority of people looking to do a sealed enclosure would be shooting for. Especially when you still will be applying EQ.Or are you looking at bringing this down with a LT?

Also yes the displacement difference is not at all trivial -but obviously witht he huge tradeoff of efficincy. Any idea Dan what the efficiency of the proposed 15 would be???

Also the Maelstrom was designed for greater linearity than Tempest or Shiva as I understand it. Although not XBL2 technology (not that I know of anyway). It would be interesting to see a BL curve comparison of Maelstrom vs. Tempest. It would also be interesting to hear from Dan on his thoughts of the Maelstrom at it's outer limits and how linear it does or does not stay - Can you provide some further info here Dan?

Please understand, I am not disagreeing with your findings. In fact, I again would love to see this beast come to be a reality. I like my Maelstrom subs, but did not build them to be the end all of subwoofin. More as musical tight subs.

Where some of my confusion comes in is Dan himself stated the 105 DB figure for a sealed enclosure with 1400 watts in a 3 cu ft. enclosure - it is unclear to me if this is with 4.2db of a LT or not.??

Anyhow, please understand I am not disagreeing - fact is you know WAY more about this than I but I feel the model you created is based on a premise that in my mind isn't what people looking for strong output in a sealed enclosures are aiming for (.7Q). Now granted a LT can bring that down to pretty much whatever you want. Is this the part I missed?

Anyhow, very interesting thread, and participants. I personally really appreciate this forum, I have learned a ton, and the input from all of you "more learned" folks is really great, and appreciated!!

C.

 

[Randy G]

I find it somewhat unfortunate that most of you folks don't appear to be in the least bit inspired by the design goals of people like Bob Carver or David Hall(velodyne). Although the performance characteristics of their respective subwoofers might not live up to the demands of those on THIS forum, one must acknowledge that at least THOSE manufacturers have recognized that small subwoofer size is something appreciated by a MAJORITY of audio enthusiasts.
To me, THAT should be the challenge; to improve on those types of designs to the point where they APPROACH the performance levels that a majority of audio enthusiasts would consider satisfactory. Personally, I don't know what those levels are. I hear numbers bandied about like 115dbl at 20 hz anechoic that seem plain old silly to me as far as realistic for small subwoofers. It bums me out that so many of you are willing to give up box size in order to "get your numbers", when the real challenge is to shrink the box and improve upon amplifier technology. Sunfire and Velo have done it pretty successfully, but can't somebody else do it better? The Velo HGS-12 that I'll probably be purchasing is a little under 1.5 ft^3 in interior volume and puts out around 95-100 dbs of in-room response. Would I like better performance from this cube? You betcha! But I'd love for Velo to improve upon the driver and amp technology to get me there. And I also wouldn't mind paying a bit less for it as well. THAT should be the design goal for competitors.
This is all just my opinion and I'm now unfolding my flame-retardant underwear.

 

[AjayM]

I find it somewhat unfortunate that most of you folks don't appear to be in the least bit inspired by the design goals of people like Bob Carver

I'd love to be able to do something like what is going on with the Sunfire subs, actually could get close right now with one of the Blueprint subs. Anybody see the new Sunfire Jr review on Secrets page? The thing is 9 inches cubed, has a 7" driver and is getting good response down to 25Hz. Not an SPL monster obviously, but 9"x9"x9"?!

Andrew

 

[Brian Bunge]

What is missing for the designs such as what Randy is talking about is a readily available (to DIY) Class D plate amp with 1200W and what is probably a huge amount of built-in EQ, limiters, etc.

Give me the Blueprint 1203 in a 18" external cube with an HS500 amp and a BFD (or LT) any day of the week over one of the Velodyne subs. This design will best the Velo and still be cheaper. Part of what Randy forgets sometimes is that we can't all get the same kinds of discounts for equipment as he does. If I could just talk him into an endtable style sub with a furniture quality finish where you wouldn't even see the driver...

Besides, Mr. Carver probably has someone reading this thread, ready to sue Dan and the rest of us if we even mention something like his little Sunfire sub (that I was never impressed with anyway!)!

Brian

 

[Dan M~]

Good stuff from all of you.

Just some comments.

1. What is the most desired cabinet size?? Then design a driver/amp combo that will work within that "hard" constraint.

2. What can be done to effectivly reduce the volume requirement? Stuffing, etc... Isobaric?? (See 3)

3. If you were to design a driver for an isobaric design, how would the parameters be optimized?

4. What hasn't been tried?

Looking forward to your insight,

-Dan M

 

[Vince Bray]

I hear numbers bandied about like 115dbl at 20 hz anechoic that seem plain old silly to me as far as realistic for small subwoofers

I don't see why it is unrealistic. It depends on your approach. As I mentioned, the 15.2 already provides close to 115db/20hz performance in a 22" cubed box. What I thought this thread was about was doing it in a smaller box, or hitting 120db or so in the same size box. It can be done...

It is impossible to get 115/20 out of a sealed sub, very small, with low amp power ( and 1.5kw is low for these requirements, try it in uni and lets talk ). Look at Carver, the subs can't hit 115db and they have 2600+ watts of power. I'd be interested to hear of any alignment that can hit 110db at 20hz with just 1.5kw in.

There are already designs around that satisfy almost every want we've expressed, except doing it in a smaller box, which is largely about huge xmax. If you want it squeaky clean and insist on sealed, realize that means gobs of amp power, and much more than *just* 1.5kw. If you are ok with PRs, you can use alot less amp and get the output. I think PRs are much cheaper than kilowatts.

 

[Jack Gilvey]

Hi Carl,

If you are ok with PRs, you can use alot less amp and get the output. I think PRs are much cheaper than kilowatts.

Yeah, in certain situations that's the way to go, I think.

 

[Anthony_Gomez]

I'd be interested to hear of any alignment that can hit 110db at 20hz with just 1.5kw in.

That is easy.

BPD1503 in a 85L enclosure (can easily go larger, be we are looking at 3ft^3) can actually hit 110db anochaic with ony 750 watts...so the HS500 from adire with 720watts into 4ohms could do it for you=)

 

[Jack Gilvey]

Hi Jeff,

jack, a circuit board for a kit would be pretty easy to design and parts would be cheap. the hard part is getting the component values as close to off-the-shelf values as possible with as little gang soldering as possible. gimmie about a week and i'll have a circuit board. if you want all the elements (buffer,subsonic,var gain) you see on the spreadsheet, a bit longer.

Cool! Can't wait to see what you come up with. From what I understand, getting exact values is the tough part as you say, and it looks like they give the closest standard value combos in the spreadsheet.

As far as I'm concerned, a unity gain "black box" mono RCA in and out is all I'd want. No real need for level control in this stage, or an infrasonic filter (if I recall correctly, Sigfried Linkwitz himself recommends against them as they change the very shape of the rolloff we're trying to create with the circuit in the first place...gotta watch that excursion ,though).

Is there a way to make it "modular", so that values may be changed without de-soldering/soldering?

 

[Vince Bray]

we tend to deal in facts

Bingo.