First speaker project - Audio Nirvana 15" - diyAudio
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Old 29th July 2009, 08:11 PM   #1
tuckers is offline tuckers  United States
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Default First speaker project - Audio Nirvana 15"

So can a 15" driver really do it all?

Well, I have gotten intrigued by the single drivers made by Common Sense Audio. I just ordered the 15" pair after some correspondence with the owner.

Driver Specs

I figured that I would try them out in a rough open baffle from his designs. It will be easy and inexpensive to build. If I like what I hear, I'll figure out what box to build later.

Since he has a good return guarantee, I feel good about trying it out as a first project.

I currently have a Horning Hybrid speaker with a modified Lowther driver running without crossover and a paper tweeter on the highs. So I am very familiar with full range or at least very wide range. I have heard many of the full range speakers at various shows in the last five years. My favorite of those are the Maxxhorns.

I definitely have my doubts about the intermodulation distortion (it that's the right term) that can happen with bass frequencies playing from the same driver as highs.

I know that many of the single driver systems - Lowthers, Fostex, Feastrex etc. can sound rough when pushed with complex music.

I have heard the Feastrex three times. I thought they sounded ok, but they didn't do so well with complex music or volume.

What I expect to figure out with the open baffle is if I am hearing these kind of problems including garbling, roughness on peaks, coherence, treble smoothness etc. At least down to the 60hz or so that an open baffle can do.

Any suggestions or ideas about these drivers?
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Old 30th July 2009, 03:52 PM   #2
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Short answer is no, a 15in driver can't do it all, especially when built to a price. Don't get me wrong, $400 is not loose change down the back of the sofa, and the AN drivers are usually reasonable for what they are, but you're not going to get Altec / Olson levels of engineering quality. Still, I suspect it'll do a lot of things ~good enough for a lot of people, and you've got a heck of a lot of driver there for the money.

Re general useage, Q on the larger ANs seems to be somewhat higher than claimed, if user measurements of the 12in units is anything to go by. That's not necessarily a bad thing if you're using them on baffles; they'll go a bit lower before rolling off. Linear excursion isn't huge, so dynamic headroom will be limited, albeit less so than the smaller units will be. Given that a BR even approaching optimal would be of epic proportions, a baffle is probably the best way to use them -you might feel like low passing them & partnering with a suitable 15in woofer at some point.

As for distortion, getting a cone as large as this to cover such a wide BW isn't easy -you can see some of the consequences on the impedance plot, which shows the cone breakup modes. Up side, you'll probably suffer a bit less elsewhere due to the size of the cone & the reduced excursion relative to smaller units. YMMV as ever of course. You might find these beasts better at rock etc. than some of the smaller drivers, although very complex material might not be so good. Keep us posted on your experiences.
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Old 30th July 2009, 08:15 PM   #3
tuckers is offline tuckers  United States
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Can you tell me the models of Altec and Olsens you are referring too (and are they full range)? I been recommended the Altec BiFlex's by someone recently.

I have liked a lot of the vintage Altec systems I have heard, but none of them were the full range drivers.

Help me out here. My understanding of Q is that it's a measurement of how stiff the driver is at excursion, or how compliant it is? I know that Q can be adjusted electrically in subwoofers.

I don't know what BR stands for but as I understand it, it is the volume of a speaker enclosure.

I was wondering if there are any tweaks to increase the BR (is this correct) of an enclosure? I remember reading about KEF using something like powdered carbon in their small speakers to mimic a larger volume enclosure.
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Old 30th July 2009, 10:40 PM   #4
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For the main part I was thinking of Olson's 15in unit (you're not likely to run across one in a hurry), and some of Altec's coax drivers, esp. the 604.

Driver Qts = (Qe*Qm)/(Qe+Qm). It's a mathematical construct essentially expressing the total damping (electrical and mechanical) of a drive unit at resonance. A low Qt indicates a driver with a very high degree of self damping; a high Q driver conversely is less well (even under) damped at resonance.

BR = Bass Reflex (or vented box).

I can't speak for KEF, but generally speaking, not really -not something that'd make a significant difference to the cabinet volumes we'd be talking of here at any rate.
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Old 30th July 2009, 11:02 PM   #5
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On my mobile disco I use an 18 inch bass unit for the lows and a 4 by 10 inch cabinet for the mids and highs.
This gives excellent results.
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Old 31st July 2009, 04:36 AM   #6
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Oy! BR= Bass Reflex. Now I feel dumb!

The 5.6 enclosure that Common Sense recommends doesn't seem that huge, especially next to my big Hornings! I could do bigger.

What would a bigger enclosure do for the sound, besides allow for lower bass. What would it do for the other performance characteristics? Higher efficiency?
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Old 31st July 2009, 06:40 AM   #7
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Quote:
Originally posted by tuckers
The 5.6 enclosure that Common Sense recommends doesn't seem that huge, especially next to my big Hornings! I could do bigger.

What would a bigger enclosure do for the sound, besides allow for lower bass. What would it do for the other performance characteristics? Higher efficiency?
I think Scott is talking about something significantly dwarfing a 5.8 ft^3 box.

What you don't get with the big box is a big bump at the bottom.

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Old 31st July 2009, 08:21 AM   #8
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Quite. 5.6 cubic feet isn't enough. For a vented box, this thing needs the kind of cabinet that'd make the 5.6 look like a standmount.

OTOH, the 13.6 wouldn't be a bad option as a sealed box; Qtc of about 0.78, F3 around 40Hz.
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Old 31st July 2009, 11:49 PM   #9
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'I know that many of the single driver systems - Lowthers, Fostex, Feastrex etc. can sound rough when pushed with complex music.'

This is and has been my primary complaint about paper FR drivers. But after ALOT of thought and ALOT of listening, I decided they are still superior to complex crossovers, polymer cones, and waterfall plots that look like Ayer's Rock. But pick your poison. I haven't heard Feastrex. Fostex is good at low volume. I can't recommend Lowther to anyone. AN is the best I've heard so far.
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Old 2nd August 2009, 03:41 AM   #10
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I prefer active crossovers or better no crossovers at all I agree that the limitations of full rangers might be preferable to the mucking up complex crossovers and multiple drivers can do.

I am beginning to understand the physics of the driver in the cabinet better thanks to this forum!

So the stiffer or higher Q driver needs a larger box because more air volume will allow the driver to have more excursion and reach to lower hertz and also lower the resonance of the box?

What about a passive radiator as opposed to vents or sealed? I know many sealed speakers and subs use them to play lower. How about in this application?

Also, I have seen the threads about stuffing speakers with various materials. Including experiments with Pearlite. This can allow greater air adsorption.

Pearlite Thread

Theoretically would a gas that compressed easier than air be the ultimate fill?
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