4 way speakers

I was working on this project during last summer. It was an experiment, where I tried to make a speaker with very simple crossover. Lower frequencies were filtered out with capacitors and higher frequencies were filtered with foam of varied thickness. The benefits of this design are low cost(no expensive inductors) and flat impedance (easy load for an amplifier).
This speaker still needs a separate powered subwoofer, because lower woofer is in bandpass enclosure and it's frequency response drops sharply at around 100hz.
I don't have photos of finished speakers yet.

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Car Audio

I've been playing with different car audio setups for a few years. Here is where I am at now.
For tweeters I use modified  Aurasound NSW2 drivers (cone is slit and coated with damping spray and rear chamber is staffed with foam)  attached to small horns. they cover ~1khz-15khz
For midbass I use modified Dayton Audio PA165-8.
Subwoofer is 15in driver from diycable.com (very nice sub)

Foam acts as lowpass filter and provides smooth high frequencies roll off.

I use a single inductor for woofer's crossover. if you use metal drivers, notch filter has to be implemented, foam won't filter out metallic resonances.

This is frequency response(red) at driver's sitting position. It looks like high frequencies are recessed too much, in reality tonal balance is just right.

nearfield measurements of woofer and tweeter (system is playing pink noise)

frequency response on tweeter axis, mic is 8in away

So, my conclusion is that car system needs to be calibrated on tweeter axis, no matter where tweeter is installed. If I tried to achieve flat frequency response at drivers position, sound would be very bright and unnatural.

Of course there are still some problems in my install, particularly that hump at ~300hz

boombox, ghetto blaster

Here is my new project with drivers mentioned in previous post.
I used amp6 for woofers and t-amp for tweeters. Crossovers are passive (I didn't have time to design and build active ones). Crossover point is at around 1khz. Woofers' 7khz resonance is about 30db down, which is apparently not low enough, because at high volume sound becomes "crisp" It should be tested with higher power amp, because that sound could be caused by clipping amplifier. Anyway, it plays loud and sounds quite good for a boombox.
For power supply I use 10 rechargeable AA batteries.

Sunflower is not part of the boombox, it's just sitting behind.
Back of the boombox looks exactly the same as front(tweeter and two woofers)
Calculated frequency response.

Update, August 2013
I've tried to listen to this speaker through my UCD180 amplifier for a few days.
And I came to conclusion that notch filter must be used with metal woofers.
That spike you see around 7khz, 35db down is a big problem. It is not immediately apparent, but over time it develops into an unpleasant listening experience. If you are building speakers with metal drivers based on someone else's designs, I suggest you choose only those crossovers  that use notch filters.

aluminum woofers' cone treatment experiment

These modifications were done a few years ago. I'm just reusing these dayton DA175-8 woofers for a new boombox project. Cones were slit an covered with automotive damping spray. Small copper caps are glued on top of pole pieces.

Blue line in the graph below shows modified woofer's FR, measured on axis(in box).

Yellow line is FR measured with thick foam placed in front of the woofer.

Manufacturers' supplied FR

I was doing these modifications to reduce resonance above 5khz. As you can see resonance is still there. Unfortunately aluminum cones do not benefit from this kind of modifications.

Neo8 planar transducer in a waveguide

I just found photos of my unfinished project. Neo8 in a waveguide.
Animated  .gif picture illustrates effect of an acoustic filter (foam).
I don't remember FR's measuring distance.



At this time I don't have facilities to construct any real loudspeakers, so I'm just sketching some designs.

It's a fun party loudspeaker, with cupholders ), built-in amp, horns, 6.5" mids and 15" sub on the bottom.
"Party buddy"

Big 2 way DIY loudspeakers with waveguide

This project went from simple testing of vifa xt25 tweeter in 12in parts-express waveguide to finished loudspeaker.
I think most pictures here are self explanatory. One thing to note, this peerless SLS 830669 in it's stock form will not sound good with this crossover. It's cone starts to resonate around 700hz, and it is very audible. Cone treatments that I've applied, significantly reduced this resonance and it's audibility.

Dust caps are removed, top layer (polypropylene?) peeled from cones. Then cones are slit and coated with damping spray. Copper ring (from home depot plumbing supply) glued onto pole piece.

Red impedance curve is before and green curve is after cone treatments.

Preliminary crossover

Speaker is converted from open baffle to sealed. 12in cardboard tube ( for concrete) was glued to the baffle.

Final crossover.

I use these speakers for home theater. They can play loud with great speech intelligibility.

Until recently my main home speakers were ones with scanspeak drivers,

documented below. In process of moving I packed scanspeaks and carried out 

of the basement these speakers and placed them in place of scanspeaks.

Connected them to my favorite HarmanKardon amplifier and was surprised with much

improved dynamics over scanspeaks. Unfortunately I have to part with these speakers due to their size. In terms of sound quality, these may be the best speakers I've built, although I have not compared them directly to my 3 ways.

 

3 way loudspeakers

These are my first 3way speakers. They went through several crossover iterations, the chosen crossover sounds best, obviously :)
Parts used:
0.75 parts-express cabinet (sealed),
tweeter - Usher 9930-20
mid - CSS FR125(early model)
woofer - seas H511







Rear chamber for mid driver is made out several layers of duct tape.











Final crossover, and calculated frequency response.

Two way loudspeakers with waveguide

For these speakers I used Seas 27TDFC/TV tweeters, Scan-speak 18S/8531G woofers, 1cft parts-express cabinets and 6.5in MCM waveguide.



These are my main speakers, they have very non fatiguing sound. I can listen to them entire day without getting tired. I use separate amps for tweeters and woofers. I slightly lowered tweeter's amp gain, so if I used single amp, I'd use a bit larger resistor in series with tweeters.



Crossover

Line array speaker project

These are parts-express buyout drivers. 69c per pair. Part number 309-160  I actually had to tear apart 52 pairs of speakers to pull these drivers out (not all of them are in the picture) :)














Drivers are glued back to back, then hung on a piece of rope, then wired in parallel/series configuration for 5 Ohm. They are configured as dipole (front - push, rear- pull) There is total of 48 drivers per side.


















8in away on axis frequency response (FR) and harmonic distortion.













Correction circuit












12ft away on axis array FR








FR of two arrays with correction circuit and OB woofers together, at listening position, about 12ft away.




For a little less than a hundred dollars in parts and shipping, I've made a not bad sounding exotic speaker system :)
Here is my subjective impression of the sound from these speakers. While you are sitting or standing in one spot, sound is very similar to a standard speaker, maybe with a little bit of a full range flavour, just as all full rangers these drivers are forced to play in their resonant region. The big difference from other speakers begins to reveal itself, when you start moving. There is an impression of sound "glued" in space, does not matter where you move, sound remains exactly the same. Tone and loudness do not change.