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Multi-Way Conventional loudspeakers with crossovers

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Old 6th January 2013, 11:38 PM   #11
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Using a valve amplifier and over driving it will warm the sound up.

If you don't want the expense of valves then look up soft limiters as they make a similar sound to an over driven valve amp.
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Old 7th January 2013, 03:48 AM   #12
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Quote:
Originally Posted by soundwavesteve View Post
I appreciate the effort GM, but my intention IS to have that upper bass hump in the response. But you did verify that this speaker does have an upper bass hump!
You're welcome! Understood, it's a sim I did for myself, I posted it to show the blue trace to confirm. At least a century of testing tells us that a ~1.4 Qt is the upper limit for acceptable 'warmth' and even then this is down in the bass where our hearing acuity is pretty bad, so am curious if this one works for you in the mid-bass thru the lower mids without mass quantities of stuffing.

GM
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Old 7th January 2013, 07:49 AM   #13
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Quote:
Originally Posted by soundwavesteve View Post

Yes Pico, I am doing a tweeter, but just a regular one....a Dayton ND20 rear-mount. I am probably going to do a band-pass on the tweeter, between 3.5Khz on the low side and maybe 8 or 10Khz on the upper. This way I can roll off the upper treble and it won't be harsh when I crank it with the power tools going. Also, with a 2nd order crossover of 3Khz on the woofer, I'll also end up with a notch in the response around 3-3.5Khz - this area typically sounds bright to me, so this will also help with keeping the sound smooth when I turn it up.

I did think about a paper cone tweeter, but I like how that Dayton looks flush mounted. I am also going to bottom mount the goldwood so it looks flush.
So, you've just described what a WG does naturally without any electrical notch : it forces the membrane ( of the tw) to couple to the air in the cavity
or boundaries of the WG ( maybe Geddes would...) depending on the geometry and, for low frq. cut-off, on the diameter of it, which is related to
the freq. to be reproduced. So it raises the sensibility ( it adds gain) of the driver, thus combined with directivity control, on the lower range ( the highs
remain unchanged), which is good when pairing with a big woofer ( 8" is gigantic) for many reasons (no: only one sensitivity matching).
Using new style fullrange (such little multimedia speakers) as a mid tweeter
sligthly puts the power acceptance a little higher, so no worries about crakles and fuzzs that may suddendly destroy ...domes.
I'm not pursuing anything, just to make you notice that there are some solutions.
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Old 7th January 2013, 04:22 PM   #14
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GM - Yea, we'll see. I never built a speaker that intentionally sounded very warm. I'll have to check the Qtc when I get home - if I recall, in the .2 cu/ft box I was planning on it was 1.85!!! I'll double check to see if in increase in box size makes a noticeable difference in the Qtc value.

Pico - I didn't know that a WG acted as a natural bandpass filter......I'll remember that for future projects! :-)
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Old 7th January 2013, 06:05 PM   #15
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All boxes, even an OB, is an acoustical band-pass filter.

FWIW, back in the bad ol' days we used electronics, drivers ripped from old radios, TVs, consoles, which typically were very high Q systems, so that they would perform good enough in the heavily vented cabs of the tube era, so for individual shop speakers we would use milk crates or similar open containers that we wrapped with cloth or similar to protect them from dust, insects, occasionally vacuuming them off to allow them to 'breathe'.

For small workbench systems, small, leaky cardboard boxes lightly stuffed with fiberglass insulation worked well enough for AM and even early FM. Kleenex tissue boxes were popular for one particular size oval driver since the cutout seemed like it was designed for it.

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Old 7th January 2013, 10:02 PM   #16
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LOL - kleenex box speakers!!!
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Old 7th January 2013, 10:08 PM   #17
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I think that the passive vibrations of the cabinet, if not built out of dead sounding mdf can add warmth to music like a guitar body. Also horn loaded cabinets can have additional resonances that give character to sound. A speaker with lots of character is the Cornu spiral horn. Made of very thin panel or foam core, it definitely colors sound but for the better.
Foam Core Board Speaker Enclosures?
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Old 7th January 2013, 10:45 PM   #18
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The trouble with thin wall enclosures is that they will resonate frequency selectively. Seems like a crap shoot to me. A better approach based on my experience is to build the box out of MDF, but put a passive radiator made out of a driver in it. By shorting the terminals on the driver that is acting as a passive radiator, you can to some extent tune the mechanism. I put two 8 inch speakers in a box about the size of an AR4x (10 x 19 x9 internal?), and put an 8 ohm resistor across the terminals of the secondary 8 inch, and it sounded very good and warm, without audible ringing at bass frequencies. As for the tweeter, I'd rec. going with a conventional tweeter that goes to at least 15kHZ, and using the treble control to roll off the high end above 10-12kHZ if you actually want to. The tweeter you mentioned, the ND20 (?) is one I like and use, and it's resonance is at around 4kHZ, so shouldn't be used below about 6kHZ in my opinion. I bring it in at 7kHZ with a one pole crossover cap. Zaph tested it and claims it's ruler flat from 5kHZ to beyond 20kHZ. Often the bigger issue is the off axis response that will have a big jump at the crossover frequency, where the woofer has gotten rather directional, and then a small diameter tweeter comes in with it's much wider dispersion.

Open baffle speakers have intentional coloration that many people like, but they have to be placed at least 3 feet from any walls to be a plus.

Tube amps sound warmer because of soft clipping, 2nd harmonic distortion, weak damping (1+ ohm source impedance allowing the woofer to ring a bit), and according to Bob Carver the speaker simultaneously acts as a microphone, picking up the acoustic signature or the listening room, and coupling that into the negative feedback path of the amplifier, which then amplifies that on top of the program source. With power tools running, this may not be a good thing.

Bottom Line: Tone controls and perhaps the passive radiator is my suggestion.

If the speaker is going to be a 2 way, and you're using that ND20 tweeter (3/4 inch dome), the woofer should be small diameter (6 inch or less) so the off axis response at the crossover point doesn't cause harshness (big step up in the off axis upper midrange freqs.). A 6 inch woof with an 8 inch woof acting as a passive radiator with shorted or resistor across its coil could be good.
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Old 10th January 2013, 11:56 PM   #19
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I made my first prototypes this week and have been listening to it for a couple of days....but its not quite what I am hoping for. First, as expected there isn't anything you could call bass. It's got a 7db hump around 150Hz-200Hz, but instead of 'warm' sounding, its sounds....um.....exaggerated - like it's resonating. Second, as mentioned in my other posts, I tried creating a bandpass filter on the tweeter to roll off the upper treble, but it sounds....grainy...like sandpaper tweeter domes. I'm thinking I maybe used too cheap of parts on my tweeter...or I just did it wrong...or my soldering is weak/dirty....

I am wondering if I need to go back to the drawing board? Since I have no idea what freq's make for a warm, rich sounding speaker....perhaps my choice of 150-200Hz is wrong?
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Old 11th January 2013, 01:18 AM   #20
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Quote:
Originally Posted by soundwavesteve View Post

I am wondering if I need to go back to the drawing board? Since I have no idea what freq's make for a warm, rich sounding speaker....perhaps my choice of 150-200Hz is wrong?
A 7 dB hump at 150-200 sounds like mud to me, and even worse in the usual 8 foot ceiling rooms.

I like my shop speakers to be as flat as possible above about 100 Hz, as I wear deadphones a good amount of the time (they mellow out the top end), and have a "loudness contour" lifting the subs response from 20Hz to about 100 Hz.

My little Sony receiver (from a dump in Alice Springs, Oz, took about 2 months on a slow boat to make it to the USA) has a 5 band EQ, then the 12 volt car sub crossover has a low boost (sometimes engaged).

Having 8 small 2 way speakers and four subs spread out around the shop allows the speakers to play over the level of the loudest tools with only a few watts. They are a motley crew ranging from Radio Shack cones to ancient Acoustic Research midrange, at least 10 different types of transducers, 34 count total. I only actually paid for a few of the drivers, most were curb rescues ;^).

At any rate, I'd advise going for a flat response, and EQ to taste, you can pick up EQs for cheap and insert them in the tape monitor of any old receiver.

Have fun, use hearing protection...

Cheers,

Art
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