Dayton Amps/Subs 20% off, IB15 $96

[jjdche]

Just a heads up, Parts Express is having a 20% off sale on alot of subwoofer realted items.

[severianb]

Nice find. That's like $25 off the normal price... adds up if your buying multiples.

[jgsabato]

Thanks for the tip. Drove up to PE today and picked up a couple of Dayton 15 DVC's.

Now that I have the 4 drivers, time to start testing where to put the manifold outlet.

[dewardh]

This looks to be a great deal on what I would regard as potentially excellent IB drivers. But do note that those are both very high compliance drivers. The 15 DVC Vas is 277 liters and the IB15 Vas is a whopping 311 liters. The 12 inch NHT 1259, with a Vas of 238 liters, is regularly denounced here as having a too-high-compliance suspension for IB use.

While I don't agree that high compliance is bad, and in fact believe that very high compliance is actually a good thing in an IB driver (and Dayton seems to agree), it is important to note that when using high compliance drivers it is, even more than usual, necessary to protect against over excursion with a peak limiter and steep high pass filter. If you plan to use the Behringer digital filter all is taken care of, since it is by nature a peak limiter (if amplifier gain is correctly set) and a sharp cutoff high pass (rumble) filter is easy to set. I'd put the -3db point at or slightly below Fs.

[jgsabato]

I do plan on using a filter with my IB. I chose the DVC's because they have very similar TS parameters of the original Tempests (which I have 2 of) and will be using them in a manifold together.

I modeled 4 Tempests and @ 20 Hz, it takes about 110W each to reach full linear excursion with an ouput level of 114 db.

I already have a filter that has a corner frequency of 15 Hz with an 18 db / octave slope, so I will start with that and with one of my current amplifiers which will not massively overpower the drivers.

[zbigb]

Modeling the drivers with anticipated input gives a more complete picture than any single T/S parameter.

While the VAS is related to the suspension stiffness (through driver area and air compression) Cms is the force exerted by the mechanical suspension of the speaker and is a direct measurement of its stiffness/acoustic compliance regardless of size. This measurement tells us how many millimeters the suspension will compress with 1 Newton (0.224 pounds of force) applied. (How many Fig Newtons is that? )

Hear is a comparison of a few drivers:

...................................................Cms (mm/N)
AV15.............................................0.145
SoundSplinter RL-P15 DVC4...............0.179
Adire Tempest 15D4 ........................0.247
Titanic MIII....................................0.291
Dayton 15"DVC................................0.307
Dayton IB15....................................0.33
Adire Brahma B15-D2........................0.345
Titanic MII......................................0.36
Stryke IB 15....................................0.455
NHT 1259........................................0.740
Dayton Titanic 1200..........................0.942

The Dayton DVC is very close to the Dayton IB.

All other T/S parameters being equal, a driver with high compliance (soft suspension) will flex out to it full Xmax with less watts than one with a stiff suspension, regardless of its maximum electrical watt rating. This generally means more distortion for the same driven watts.

Compliance can be a reliable "first indicator" of how the driver will work without an "air spring" to support it and modeling the speaker provides a fairly complete picture. However; one driver can have much better linearity than another through the extended range of its Xmax. If there was a standard for Xmax vs. linearity the picture could be more complete.

Seems to me that sharing experiences on this forum is the best thing going for selecting good IB drivers.

[ThomasW]

zbigb

Thank for posting that comparison, you saved me a ton of typing...

[severianb]

What do you guys think of this plan:

8 of these (IB15s) in a manifold, wired in series, 4 to a side, producing a 2ohm load per side.

Power this with a Behringer EP1500 in stereo mode which puts out 700watts rms at 2ohms in stereo.

I'm thinking that for about $1000, this would be able to handle even War of the Worlds at reference volumes in my 1700 cu. ft. room... although it's doubtful *I* could.

Now to convince the wife, who thinks my 12" Sony sub is plenty. Silly woman. ;D

[ThomasW]

I wouldn't use a 2 ohm load, but other that that it sounds like a plan.

BTW, this isn't car audio, so you aren't going to need or want 1400 watts when you have 8 drivers acoustically coupled together

[dewardh]

zbigb:

You wrote: "All other T/S parameters being equal, a driver with high compliance (soft suspension) will flex out to it full Xmax with less watts than one with a stiff suspension, regardless of its maximum electrical watt rating. This generally means more distortion for the same driven watts."

So . . . the high compliance driver will convert more of the electrical input to moving the cone (making sound) and less to merely flexing (pushing against) the suspension. How does that result in "more distortion for the same driven watts"? More to the point, perhaps, what about distortion at the same acoustic output (cone displacement) . . . where one amp is pushing air and the other is pushing air and flexing a (non-linear) stiff suspension?

A ribbon driver, for example has very,very,very high compliance, but that is usually regarded as a positive (except for fragility), not associated with increased distortion. If the drive motor is itself linear then avoiding the non-linearities of a stiff suspension would seem to be a *good* thing . . .

I had hoped to be able to "share experience" in a month or two, but my new woofer drivers (Peerless) are backordered, which will delay finishing the main speakers, and now it seems the Behringer crossover/equalizer I'd intended to use is backordered for several months as well. As for measuring distortion, that's difficult at best, and I have seen exactly *no* distortion measurements here or anywhere else for any of the drivers you list when used in IB "enclosures". It's hard enough to find distortion figures for those drivers when used in the (relatively) small boxes they were *all* originally designed for. I don't find even a standard methodology . . . where would one measure a manifold's distortion, for example? One meter from the mouth?

Most IB discussions which I read (and subwoofer discussions in general, for that matter) don't even discuss group delay and phase integration with the main speakers (and the resulting amplitude irregularities from cancellation) . . . it's mostly "rattled the windows" and "knocked a vase off the shelf". In that regard, at least, this board is better than most . . .

dewardh

[dewardh]

severianb:

I think you mean in parallel, not in series . . . (which is a good thing . . . wiring drivers in series reduces amplifier damping, with negative effect). Although four nominal "8 ohm" drivers in parallel does result in a nominal 2 ohm load the actual impedance will be higher close to resonance, and probably not fall to an actual 2 ohms in the "subwoofer range". Still, the amplifier will in all probability be current limited and may not produce its full rated power into the load.

Not that you'll need it to . . . with 8 15" drivers in 1700 cu. ft. you'll be hearing "turn it down" a lot more than "turn it up" <g> . . .

[zbigb]

dewardh,

"So . . . the high compliance driver will convert more of the electrical input to moving the cone (making sound) and less to merely flexing (pushing against) the suspension"

More sound with less watts, yes. But Making more sound is not the same as making less distortion. Distortion can occur at low or high sound levels.


"How does that result in "more distortion for the same driven watts?"

More distortion is just generated because the driver is working in the non-linear region of the voice coil position a greater amount the of time, farther away from center position.

"avoiding the non-linearities of a stiff suspension would seem to be a *good* thing . . "

Avoiding the non-linearities is a good thing,... but suspension linearity is not related to stiffness. Non-linearity in suspension is introduced when the suspension runs out of travel.

"A ribbon driver"

Does a ribbon driver have a voice coil?

[ThomasW]

A ribbon driver, for example has very,very,very high compliance, but that is usually regarded as a positive (except for fragility), not associated with increased distortion.

The operation of a ribbon drive element is fundamentally different from a cone based driver. So you're making an apples vs oranges comparison and you know that.

It's fact (from Ken Kantor) that running the 1259 without benefit of the air spring results in higher distortion, since the suspension depends on the 'air-spring' to maintain linear operation of the cone.

So here's how things are going to move forward.

You're going to stop hijacking threads with comparison between 1259's.

You build your IB and enjoy it's operation.

If you hijack another thread, your membership will be terminated.

This thread is now locked