Simple sub design

[Bennett Prescott]

Re: Simple sub design

It's no coincidence that this big bump is at a typical (electrical) crossover frequency between subs and tops. If you're going to push the level on the subs for a rising system response al low frequencies, you probably should be thinking about underlapping the low and sub passbands to reduce buildup at the crossover.

I think you will find that underlapping crossover points for the sub and mains bandpasses, especially with the usual 6-12dB increase in sub gain over the mains, will result is far too many consequences in today's predominantly aux-fed-sub PAs. It also makes timing kind of a pain in the ass. If you think about it, to underlap the crossovers you have to set your sub LPF at something like 50Hz, and your mains HPF at something like 120Hz. Sure, they sum nicely when playing together, but now every source you don't put in the subs sounds super thin. You're also going to have frequency domain interaction between the sub protective HPF and system integration LPF, resulting in reduced level and increased drive requirements... not helpful on a subsystem that is already restricted to maybe 1.5 octaves of bandwidth.

Personally I prefer to significantly overlap the sub and mains crossovers, so the mains are running down to maybe 40 or 50Hz and the subs get knocked out an octave higher. Timing is much easier, transients are preserved, and a little EQ boost to the very lowest end of the sub response makes the summed systems have a nice rising slope into the LF.

 

[Chuck Simon]

Re: Simple sub design

If you work with bass players that use a 5 string bass-then you need to go flat to 31Hz (the open B on the 5 string).

If your system can't do that-then you are able to reproduce what the musicians are playing.

just something to consider---------------------------

If that were true than almost every bass amp made would be inadequate for the job! How many bass amps/cabs can you name that go flat to 31Hz?

 

[Caleb Dueck]

I wouldn't use bass guitar amps/cabs as proof that full low frequency isn't needed. Rather, that true low frequency has been so hard to reproduce for so long, that most don't know what they are missing.

We have a few installed systems that can play fairly deep (Danley DBH in multiples or DBH-LC), 30Hz or under. Ask them if there is a difference, and if they are willing to go back to "average" bass!

 

[John Halliburton]

Re: Simple sub design

If that were true than almost every bass amp made would be inadequate for the job! How many bass amps/cabs can you name that go flat to 31Hz?

Many moons ago at Intersonics, Tom and I helped a coworker build a new bass rig. He had a Peavy cabinet with dual 10" and an 18" under.

Tom laid out a bandpass design that we implemented with a passive radiator in front of the 18". Got a full octave lower than the original. Then we loaded the dual 10" into a waveguide with a 90 degree horizontal pattern.

I went to one of his first gigs out with it-he played in a GD jam band. Four and five string basses. Good sized club.

The band were a bit overwhelmed, and he had to dial it back quite a bit.

Fun, but the upshot was definitely in line with Chuck's and other's observations here in this thread.

As for overlapping or underlapping in system alignment-I've been closer to Bennett's camp-my tops will easily go down to 60--70hz, but I tend to crossover to my subs around 90hz, but not with an aux fed layout anymore, it's been processed together on Proteas, and I'll just introduce parametric notches for the "Death to 100hz" or similar problems.

Best regards,

John

 

[Jamie chappa]

Re: Simple sub design

This is way to wide open of a question. And some of the replies are already projecting their needs into the answers.
You need to give us way more to go on, and do way more thought yourself.
So what are some of the priorities?

Size. Footprint. Does the cabinet need to be used to stack other things on it? Or are the mid highs on sticks?
If you are stacking, how tall does it need to be? Does it need a certain footprint for safety? Will it have a cup for a pole?
How will all of this interact with your material? EG, are you using 4x8 sheets? Or 5x5? Or do you have some pieces around you need to work in?
Do you need to meet a certain size for transportation? Truck pack? Trailer pack? Minivan pack?

To all these questions above, Art Welter (one responder to this thread) had an awesome system that was designed to pack in a van, stack to a good height for audience clearance, and be made out of materials that would not have a lot of waste when cutting them out. I have no idea how low it went, (I'm guessing his answer provides clues), but to me the other things were just as important, and very impressive in the implementation.

The first thing my calculator tossed out was 8 cubic feet, one 6" port, 4.33"
The eminence below is 6 cubic feet, four 3" ports, 6.54".

Where do these fit into your priorities?

Regards, Jack

Thank you for the help so far. I know I was asking a lot with not a lot of info to go on.
Size is not high on my list. When I bought my trailer I made sure it was bigger than I needed. They will need to be stacked. I have ten total drivers, The idea was to be modular. My needs size wise very week to week. There is not a need for a cup. M/H will be stacked on top. As for sheet size I was going to look into baltic birch not really sure what is available near me.
Ok now given the info I have gotten from this thread how have I not fried all of my drivers yet. I'm not doubting anyone's answers, I know that numbers don't lie. Week after week I pump way more than I should be through them. So is it the box i'm using. I know if the amp is rated for 1600 its peak but still wouldn't that still be to much. It was mentioned that these drivers are not suited for my needs. What should i be looking for in a new driver. Is it just a larger xmax or are there other parameters that I should be looking for.
Is there a decent online source where I can learn more. I can do a general search but ya never know what is accurate.

 

[David Morison]

Re: Simple sub design

Ok now given the info I have gotten from this thread how have I not fried all of my drivers yet. I'm not doubting anyone's answers, I know that numbers don't lie. Week after week I pump way more than I should be through them. So is it the box i'm using. I know if the amp is rated for 1600 its peak but still wouldn't that still be to much.

There’s a couple of things that would contribute to the survival of the drivers in your case. (NB - some generalisations to follow, caveat lector etc...)

Firstly is the nature of musical signals compared to power test signals. Music tends to spend quite a lot of the time with less signal present than the peaks – if you think of what’s getting sent to your bins (given you said you don’t do EDM etc), the part that may occasionally get up to tickle the clip lights will probably be the kick drum. That will only have peaks a few times a second, each one a lot less than a second long, so the total energy being delivered to the drivers, when averaged out over the length of a gig (or even a single chorus of one song), is probably still within the rating of the driver. The power rating of the driver will on the other hand have been derived using a signal that has its average level closer to the peak level, and the drivers will have survived that for typically at least two hours solid, to get their power rating.


That may make you wonder where the lower power figures mentioned upthread have come from, if the drivers can actually handle all that power. Those power figures are not based on the thermal limit of the driver (how much heat it can withstand), but rather a measure of how much of that you can use before the drivers stop moving in as linear a manner as they should. That means distortion may increase and the drivers will not necessarily keep up with the dynamics of the signal, but they won’t necessarily fall apart right there.


Lastly, the box they’re in may be helping somewhat – for a vented box, the smaller it is and the higher its tuning frequency, the more it will suppress the over excursion of the driver (within the passband at least), albeit high tuning frequencies do allow more excursion immediately below the tuning frequency.

HTH,
David.

 

[Art Welter]

Re: Simple sub design

It was mentioned that these drivers are not suited for my needs. What should i be looking for in a new driver. Is it just a larger xmax or are there other parameters that I should be looking for.
Is there a decent online source where I can learn more. I can do a general search but ya never know what is accurate.

Jamie,

Josh Ricci's Data Bass website is a great resource for comparative output of a number of different designs.
Doing some research in to Thiele-Small parameters will get you started in general searches.
Fs, Vas are important TS parameters for whether a speaker will work in a particular box, but Xmax determines how much air it can move.
When it comes to producing lots of low frequency, there is no replacement for displacement. Xmax is one way tavel of a speaker in it's linear range.
Speakers can't put out much more level (other than distortion) once they reach Xmax, because as the voice coil starts going out of the magnetic field, more power does not results in more output.

When Xmax is doubled, a speaker is capable of 6 dB more output. More Xmax requires longer magnet structures and voice coils, costing more $$.
Your speakers have only 4.8mm Xmax, there are 18" with Xmax of 15 mm or more, one of them (given enough power) can put out as much as three of yours.

Cabinets also make a big difference, horn designs can add 3 to 10 dB more output from a speaker, so one (larger) cabinet using a high Xmax driver could put out as much as six to twelve bass reflex cabinets using the speakers you use.

These threads will give you some information about different enclosures and speakers:
Tapped Horn Vs. Bass Reflex Case Study - diyAudio

Keystone Sub Using 18,15,&12 Inch Speakers - diyAudio

Art

 

[Jamie chappa]

Re: Simple sub design

So I have been reading like crazy. I think I have a beginners grasp on things, which I know can be dangerous. I took the B&C design and input the dimensions ( including all braces and ports) for volume. Tuned it to 36hz. Input all my drivers parameters. Is it really that simple, now just build it. I thinking I'm missing a step or an important detail. I used bass box pro is there a way to put it up for someone to proof it. Thanks everyone for the help these sites are so valuable to people trying to learn. It's a good thing you guys are patient.

 

[Jamie chappa]

Re: Simple sub design

Also what determines where I set my hp on the crossover.

 

[Ivan Beaver]

Re: Simple sub design

Also what determines where I set my hp on the crossover.

That depends. For one thing what is the natural low end response of the cabinet?

Also it depends on how hard you drive the cabinet. If you push it hard-depending on the particular tuning used-you may want to raise the HP filter.

It is not an easy simple answer.

 

[Jamie chappa]

Re: Simple sub design

That depends. For one thing what is the natural low end response of the cabinet?

Also it depends on how hard you drive the cabinet. If you push it hard-depending on the particular tuning used-you may want to raise the HP filter.

It is not an easy simple answer.

It never is haha. If I take I pic of the response will that help. As for how hard I push it I would say fairly hard for its rating. Keep in mind only kick bass and 1 floor tom get fed to it.

 

[Bennett Prescott]

Re: Simple sub design

Also what determines where I set my hp on the crossover.

Jamie,

All things being equal, you cannot go wrong by setting your HP at the box tuning frequency. You can determine that frequency by doing an impedance sweep, or sticking your mic in the port and measuring its output. You will want to put an EQ bump at that frequency to compensate for the HPF rolloff, but a 2nd order filter will equalize excursion below that point.

 

[Art Welter]

Re: Simple sub design

I took the B&C design and input the dimensions ( including all braces and ports) for volume. Tuned it to 36hz. Input all my drivers parameters. Is it really that simple, now just build it. I thinking I'm missing a step or an important detail. I used bass box pro is there a way to put it up for someone to proof it.

Bass reflex are fairly simple, and a fairly wide range of alignments are workable.

Post up your sims, including the excursion chart at full power and the port velocity and the TS parameters for the speaker you are using.
If you can't figure out how to do a screen capture, shoot photos and attach them.

As you should be able to see in your sims, excursion is at minimum at Fb, but goes up rapidly below.
The HP filter should be set a few Hz below Fb to keep the excursion below Xmax at the power levels you anticipate using.

After building your first cabinet, you should check that the tuning is indeed what it was calculated as.
The most accurate way to check is by putting a dot on the cone, and watching excursion as you sweep a sine wave tone around the calculated Fb. If Fb is lower than you designed for, the port can be cut shorter to raise Fb.

Since it is difficult to add port length, I always prefer to make the port a bit longer than the design simulation and cut it back.

Art

 

[Jeff Babcock]

Re: Simple sub design

After building your first cabinet, you should check that the tuning is indeed what it was calculated as.


Art

+1000, because it probably won't be.

 

[Jamie chappa]

Re: Simple sub design

This is what I have at 1600 watts that is what the amp is rated at. As for watching the excursion you just run the sweep watch for cone to move very little than start to increase is that correct. Thanks again for the assistance.

 

[Art Welter]

Re: Simple sub design

This is what I have at 1600 watts that is what the amp is rated at. As for watching the excursion you just run the sweep watch for cone to move very little than start to increase is that correct. Thanks again for the assistance.

Yes, 10-15 volts should probably be enough to see the cone move.
The excursion (roughly) will follow the displacement curve you posted.

Your sim is at a power level that would destroy the cone, well beyond Xlim.
It is above Xmax throughout the entire pass band, only above 100 Hz can it take 1600 watts without exceeding Xmax.

The speaker will just fart above it's excursion limit of 4.8 mm, which will be reached with around 200 watts. Any more power than that won't make the speaker louder, just noisier.
Also, the sims are not accurate above Xmax.

To repeat what I mentioned in post #27, one high Xmax driver could put out as much as six to twelve bass reflex cabinets using the Omega 18.

Art

 

[Jamie chappa]

Re: Simple sub design

Yes, 10-15 volts should probably be enough to see the cone move.
The excursion (roughly) will follow the displacement curve you posted.

Your sim is at a power level that would destroy the cone, well beyond Xlim.
It is above Xmax throughout the entire pass band, only above 100 Hz can it take 1600 watts without exceeding Xmax.

The speaker will just fart above it's excursion limit of 4.8 mm, which will be reached with around 200 watts. Any more power than that won't make the speaker louder, just noisier.
Also, the sims are not accurate above Xmax.

To repeat what I mentioned in post #27, one high Xmax driver could put out as much as six to twelve bass reflex cabinets using the Omega 18.

Art

so either I start over with new drivers or I step up and call lets say danley for new subs. I guess that is my best two options

 

[Jack Arnott]

Re: Simple sub design

so either I start over with new drivers or I step up and call lets say danley for new subs. I guess that is my best two options

I thought you were already using these drivers, with success and wanted to step down to singles. No shame in that, if they are doing more than what you need already.
Just be aware of what they are capable of.

Since it is difficult to add port length, I always prefer to make the port a bit longer than the design simulation and cut it back.

This is a juicy tidbit here, Jamie.
Don't fix your ports, so you can make adjustments on your trial boxes.
Don't worry about rattles, this is just for tuning purposes.

 

[Jamie chappa]

Re: Simple sub design

I am already using them yes. The things I wanted out of making single boxes was versitility and maybe a little boost in quality. I have found out that the used boxes I bought are basically using the wrong drivers. At the time I didn't know any better. Hell I didn't know better until today. I was at a tipping point of expanding anyway I was hoping by making my own boxes with the drivers I had I would save money. So I guess the idea of buying two good boxes versus carting in six bad ones and having ok sound. I choose two good ones. I have always daydreamed about owning a couple th 118. From what I'm hearing I will probably be more than ok with two of them. It seems like a smart purchase.

 

[Tim McCulloch]

Re: Simple sub design

We own no Danley products and we're not a dealer... Having heard the original TH115 and the revised model (different woofer), I believe that the TH118 will give you more performance than you're used to. You'll initially be surprised and think "wow, there's not a lot of subbage here" because you're probably used to hearing 20% (or far more) distortion and much of that is above the electrical crossover frequency. Want less 250hZ? Take a cut at 80Hz.... (been there, done that).

Try to get a listening demo at the very least. Once you get used to hearing undistorted low bass you'll wonder why the rest of the world accepts distortion.