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Forum topic by lumberjoe posted 472 days ago 1174 views 0 times favorited 11 replies Add to Favorites Watch
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lumberjoe

2829 posts in 847 days


472 days ago

I’m currently in the process of making my own sort of “wave radio”. It’s going to be a complete enclosure that I can play music through. I already have the design done (transmission line) and I have the amp. I have 2 infinity 6” subs i am going to downfire out of a sub-enclosure inside the “box” and exit through a ported tube. I need help choosing the other components.

The Amp I have is a 2.1 channel so the subs are already all set on the .1 (which is crossed over a bit and I am installing low pass filters in-line). I am looking for the other components. I will likely order from parts express, but I could use some guidance.

I want to keep the mid-ranges at 4”. I am considering the Dayton RS100-8’s. I am stuck for tweeters and crossovers though. I’d like to get ribbons, but they are all fairly large. The unit is 10” tall, 10” deep, and 14” long. Since it’s MDF (and a LOT of it), it’s considerably heavy so I don’t want to go much bigger. I am not looking for cheap, I am looking for small though. Any suggestions? and if you can recommend a better mid-range, that would be awesome too.

-- www.etsy.com/shop/KandJWoodCrafts


11 replies so far

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Airspeed

413 posts in 501 days


#1 posted 472 days ago

You’ll like the RS drivers, I used them in many of my speakers. I wouldn’t even bother with ribbons, take a look at some the tweets made by TangBand, they have some nice little drivers! I haven’t built any speakers in a year so I don’t know exactly what Parts Express is selling right now, check the forum there, there are several small boom box type projects there that may help out! Here’s the type of speakers I build,

Here’s one of the crossovers,

-- http://smg.photobucket.com/albums/v655/aaronhero/

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lumberjoe

2829 posts in 847 days


#2 posted 472 days ago

Nice rig! Those remind me slightly of B&W Nautilus series. I’ll check out those tweeters. Any suggestions/advice on crossovers? I’d rather not build my own if I don’t have to.

-- www.etsy.com/shop/KandJWoodCrafts

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kdc68

1942 posts in 875 days


#3 posted 472 days ago

Airspeed....those speakers are real real nice…wow

lumberjoe...sorry nothing to contribute to your forum question other than drooling over Airspeeds speaker photo

-- Measure "at least" twice and cut once

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knotscott

5369 posts in 1974 days


#4 posted 471 days ago

Joe – Crossover design is a real art, and to be optimum it’s always proprietary to a given set of drivers. It’s also subjective. Like saw blades, good quality components are almost always better than cheap generics…especially caps, so don’t hesitate to get some good poly caps. Air core inductors with heavy guage wire tend to sound better than cheap little iron core with skinny wire….the litz wire chokes are expecially nice. Use decent heavy gauge oxygen free wire that’s specifically made for sound….Monster is the big name, but the name doesn’t do the work, so you can buy other names with the same construction and get the same result for less money.

The crossover point, and the crossover slope really should be determined by which components you’re trying to blend. 1st order (6db per octave) crossovers are simpler to build and have fewer components to interfere with sound, but they also provide the least amount of roll off and protection to the tweeter. There are also 2nd order (12db/octave), 3rd order, and a 4th order, each with a progressively steeper slope, and each more complicated than the previous, with no guarantee of being “better”. I spent months and years optimizing certain combinations before the internet existed. The easiest approach is to borrow driver and crossover combinations from a proven existing design, unless you want the “experience” of doing it from scratch.

Place the tweeter in as close proximity to the mid driver as possible….optimally, you want the center points of the tweeter and mid to be no farther apart than the physical size of the wavelength of the crossover point. ie: 1000hz has a wavelength of ~ 12”.... a 2000 hz crossover wavelength is 6”, and so on. If you choose a 2000 hz crossover point for the tweeter and mid, the centers of those drives should be within 6” of each other to avoid notable phase shift….it’s a tight fit, but worth doing. Lowering the crossover allows them to be a littler farther apart, but puts more strain on the tweeter, which is where steeper crossover slopes can help, and where the tweeter selection gets important. Some tweeters can handle lower frequencies better than others (not to be confused with sounding better, but a blown or straining tweeter don’t sound good at all!) Don’t be discourage if the immediate results aren’t stellar…the caps can take several hours to burn in and sound right, and getting the balance just right can take some adjustment of the tweeter output and crossover point, which of course changes several of the crossover values a little. Note that “Airspeed” places his inductors apart from each other, and at 90° to each other to reduce interference. Running separate inputs with separate wire from the bass driver and mid/tweeter drivers to your amps is another audible improvement trick that you do pretty easily for low cost. There are entire books on this stuff, so this is just the tip of the iceberg, and a couple of quick key points. Your audio components, room, and music selection will all effect what sounds best to you, but ultimately, you get to choose what suits you!

Good luck, and enjoy!

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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lumberjoe

2829 posts in 847 days


#5 posted 471 days ago

Woah! Thanks for that info! This is exactly why I kind of wanted to get off the rack cross overs instead of building my own. I really don’t have the knowledge to make a decent crossover.

This is what I am considering.

I was planning on keeping the components in close proximity, but I really appreciate the “rule” you outlined above. I knew the basics, just not the detail and supporting info. In fact I think I may have even placed them a bit closer than the recommended. I will likely use the 2k crossover, unless someone convinces me I should use a 2.5k

I am a little frustrated because I had a really nice set of small speakers I wanted to canabalize for this project. They are infinity and had the EMIT R (radial ribbon) tweeters. I have some high end speakers in my study now (Bowers and Wilkens), but to my ears anyway, the highs those EMIT-R tweeters produced were amazing and a work of art.

The problem is I only have ONE!!! I think I may have chucked the other accidentally when I was indiscriminately tossing stuff in the dumpster a few months ago.

-- www.etsy.com/shop/KandJWoodCrafts

View knotscott's profile

knotscott

5369 posts in 1974 days


#6 posted 471 days ago

Those crossovers could work depending on the drivers you choose.

The tweeter should be 8 ohms for the crossover to actually occur at 2 Khz as intended. If the impedance changes, so does the crossover point. The tweeter should have a resonant frequency (Fs) of no less than an octave below the crossover point, so an 8 ohm tweeter with an Fs of less than 1 Khz would be best….Fs of 850hz or lower would be even better. Being that it’s a 2nd order crossover with a slope of 12db per octave, it’ll cause a phase shift of 180°….you’re likely to find that the speaker will sound best with the tweeter leads reversed to offset that phase shift (positive wire goes to negative lead and vice-versa), but try it both ways and decide for yourself. It looks like the crossover gives an option of 4ohm or 8 ohm speakers for the midbass driver.

The next challenge is to match the output sensitivity of the tweeter with the mid speaker. Usually tweeters have a slightly higher output than mids and woofers, so it’s not uncommon to put a 1 to 3 ohm resistor directly in series with the tweeter to bring it’s output down to match the mid. However, that increases the overall impedance that the tweeter presents to the crossover, so it changes the actual crossover point a little. Now to contradict myself a little….an 8 ohm tweeter isn’t really 8 ohms…that’s a nominal number (sort of like amp draw on a motor). The actual DC resistance of an 8 ohm tweeter is likely to be something like 6.5 ohms, so adding a 1.5 ohm resistor to bring the tweeter output down a little bit can actually put the overall resistance right about where you want it at 8 ohms.

Another complication is to consider what the mid driver is doing above the crossover point…..take a look at some response curves if you can. If the response of your intended mid is flat beyond an octave above the crossover point, all’s well…. but most aren’t. If the natural response of the driver rolls off near the crossover point, it actually combines with effects of the crossover, and results in a steeper slope than you have planned for…..not the end of the world, but it can leave an audible whole in the mid’s output near the crossover point, which is a fairly critical frequency range that your ears are very sensitive to. Fixing it is tough if you don’t know how to adjust your crossover componentd, so it’d probably be best to get a mid driver that has a flat response into the 4khz range or higher. All you’re really trying to do is prevent surprises and get the drivers to do what you expect.

Once that obstacle is dealt with, there’s that little issue of an 8 ohm mid driver not really being 8 ohms….an 8 ohm mid is also likely to have a DC resistance in the range of 6.5 ohms (could me higher, could be lower, etc…they’re all different, but the figures I’m using are common numbers), and is likely to climb much higher as the frequencies go higher, meaning the crossover point won’t be constant, so the speaker won’t do what its supposed to. That’s actually fairly easy to deal with, and worth the minimal effort and cost. There’s a simple circuit known as a Zobel network that helps set the drivers impedance at a constant resistance. It consists of a resistor and a capacitor in series with each other that are calculated to be active at roughly the crossover frequency (2 Khz). It gets placed right across the positive and negative leads of the driver either at the crossover board or on the driver (doesn’t really matter, it’s just a parallel connection across those leads). The values of the Zobel can vary depending the driver it’s intended for and the operating range, but using an 8 ohm resistor and roughly a 15 Mfd cap is a reasonable guestimate. If you order that crossover, add 2 resistors and 2 caps to the order. You can read up on how to calculate it more precisely once you’ve chosen your mids.

Here’s a Zobel network schematic:

Here’s a typical impedance curve. The black/blue is the impedance curve (note how it rises with the frequency) ...the black/red shows how the Zobel flattens the impedance across the whole frequency range, which helps your crossover work as expected:

I know this gets a little technical, but read through it and digest it at your own pace. It’s just a few of the things that make a huge difference between a speaker that “works”, and one that sounds amazing, so it’s worth doing a good job of some of the basics IMO.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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Airspeed

413 posts in 501 days


#7 posted 471 days ago

Knottscott, holy cat cheese! I hope that’s not all coming out of your head spontaneously! You must have a great functioning brain if so! Great advice by the way, how long have you been building crossovers? I began about 7-8 years ago and I’m sure you’ve forgotten more than I remember! Do you have any speaks and crossovers you could share? I’d love to see what you’ve built, I can imagine they sound great! I get great compliments on mine but most people don’t really know what a great pair of real speakers sound like anymore, it seems they all have garbage like Bose in their living rooms and think that’s the top of the line when in reality they are crap. I used to build and sell mine but its getting harder to sell real speakers these days, it’s sad that the general public doesn’t listen to music the way they used to, most of their music comes out of an iPhone or iPod and is pushed through a cheap pair of headphones.

-- http://smg.photobucket.com/albums/v655/aaronhero/

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knotscott

5369 posts in 1974 days


#8 posted 471 days ago

I started working for Merlin in 1985, and started building my own speakers in 1987. I sold many pairs between then and the mid to late 1990’s. It’s funny, once I finally went all out and built a pair that I loved and was content with, the incentive to keep building more for other people disappeared. Just as well, as my family needs were gaining on me quickly, and I didn’t have much of a marketing plan to further the business anyway. I still have that pair of speakers shown in my projects here. They look rather plain next to yours, but I’m still happy with them.

I agree with you about what the masses get exposed to these days. Phones, audio equipment, cameras, etc., are all geared more toward convenience and technology, but aren’t nearly as good at the simple basics of what they’re supposed to do.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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Airspeed

413 posts in 501 days


#9 posted 471 days ago

Very nice knotscott! Those look pretty nice to me! I still listen to mine all the time, well anytime the wife is out, I play them a little loud for her taste! I’m driving mine with a three Carver M500t amps bridged and another one driving my rears for the sonic holagraphy in my Carver C4000 preamp. I have eight M500t’s just in case! My mains are biamped, I configured the crossovers so I could either run them with one amp, biamped with the internal crossover or run them with an external xover and bypass the internal all together. Had a friend engrave some 1/2” aluminum plate for the input and the adj L pads. I haven’t built a pair in awhile but think about it once in awhile.

-- http://smg.photobucket.com/albums/v655/aaronhero/

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MrRon

2716 posts in 1842 days


#10 posted 471 days ago

I haven’t kept up with speaker design for a long time now. My experience with speakers was with heavy 12” and 15” drivers and horn mids and tweeters, in large horn, infinite baffle or bass reflex enclosures. I can’t see how 6” drivers can reproduce pipe organ lows, down in the 30HZ range, which was what we would strive for. I can see where you might be able to reproduce a 35HZ note with a high quality driver, but there wouldn’t be much in the way of decibels. Am I way far behind?

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Holbs

510 posts in 628 days


#11 posted 471 days ago

ahh…loudspeaker building. i remember 20 years ago being in the military (when infinity kappa 5’s came out), i wanted to get into building speakers, big time. while doing some military TDY in germany, there was a german audio place that did not hold back on speaker construction. some speakers, where the size of VW bugs. it gave me incentive to build my own! until i bought ‘loudspeaker design cookbook’ and read just how much of a science it was, the electronic knowledge needed, and of course putting the structure together. i even went so far to purchase 4 drivers from DynAudio (denmark?).
i should look into building “impressively” massive speakers, since they are rare in today’s world of dinky plastic book shelf speakers.

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