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Multi-Way Conventional loudspeakers with crossovers

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Old 10th December 2012, 11:07 AM   #11
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Though I think people got it, conceptually, the 10" might be consider a Subwoofer, the point I was making was that it was not going to be a driver designated by the manufacturer as a "subwoofer", but rather a woofer.

This -

Dayton Audio DC250-8 10" Classic Woofer 295-315

not this -

Dayton Audio DCS255-4 10" Classic Subwoofer 4 Ohm 295-202

The Dayton woofer is 8 ohms, always a plus, and is rated down to 25hz, which means functionally I should be able to squeeze 30-something hz out of it.

I can except functionally that people consider it a subwoofer. Though most often a subwoofer has its own dedicated frequency range. Thought that depend, in a AV System, whether you have set the front speakers to Large or Small. In my case, I'm dealing with a Stereo system.

Attaches is a Image, crude as it may be, of the design concepts. I debate whether to make the Top Section of the 3.5-way a standard rectangular box, or whether to taper it like the Lower Section.

Again, this is all in the early planning stage. The idea is primarily built around the concept of a trapezoidal Shaped Low_Bass re-enforcing an 8" 3-way system.

Steve/bluewizard
Attached Images
File Type: jpg TrapTwr1.jpg (69.4 KB, 167 views)

Last edited by BlueWizard; 10th December 2012 at 11:27 AM.
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Old 10th December 2012, 11:32 AM   #12
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Curious?

Does this resemble any existing designs you might know of?

That way I could use those designs as a model for my system?

Steve/bluewizard
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Old 10th December 2012, 11:53 AM   #13
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Using the 2.5" x 2.5" grid on the drawing, we can arrive at the approximate dimensions. Though the practicalities of actually building them are very like to modify those dimensions.

Low Bass (trapezoid) -

15" wide on the bottom
10" wide on the top
17.5" high
?? depth unknown at this point...


3-Way (assume tapered box) -

10" wide at the bottom
5" wide at the top
22.5" high
?? depth not known at this time...


Complete system -

Overall height = 40"

I'm OK with 40" high. My current speakers are 44" including the Spikes.

As I thought about it, I think part of the goal of using an 8" and 10" is to somewhat approximate a 12" or 15" speaker while still keeping the bulk down.

Having grown up when dinosaurs roamed the earth, an 8" or even two 8" bass drivers still seem very small to me. Back in the day, you would be embarrassed to tell someone you had 8" speakers, though today that would be considered large.

So my mind was trying to conceive of a compromise between massive 12" and 15", yet still provide very solid bass, and while providing solid weighty bass, not compromise on the clarity of the Mids (especially) and Highs.

I generally find as the bass rises, the Midrange falls (in terms of quality and clarity).

Am I on the right track here, or have I completely fallen off the beam?

Steve/bluewizard
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Old 10th December 2012, 12:04 PM   #14
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You might consider the the 2nd large woofer to extend the low end of your system by letting it go down to say 30 hz in a larger cab and high up untill the baffle step frequency to compensate for the baffle step at say 400-500 Hz depending on baffle width (say 10"). The room gain can boost the low end by 3-6db and give overall flat freq response. The dayton 10" HF "subwoofer" can almost do 500 Hz and go down to the abyss in a smallish cab.

Last edited by soundaatma; 10th December 2012 at 12:07 PM.
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Old 10th December 2012, 04:29 PM   #15
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Ok Soundaatam, I got the last part of your post, but the first part baffled me (no pun). A good thought on the Dayton 10" sub, but I find most Subs are 4 ohms, and I'm not planning to use a Sub Plate amp on this. It, as it stands now, a purely passive speaker. Plus, I don't really feel I need Sub-Sonic capability. Like I said, if I can get a clean 30hz, I'm a happy camper, especially if that is 30hz at -3dB. My current commercial/consumer speakers are 28hz at -6db, so one assumes they are about 35hz at -3dB. They sound good, but I would like to go just a bit deeper than that. With 30hz@-3db, that would take me down to about 25hz at -6db. That would be plenty.

I suspect centered on the 10" bass driver, that narrowest workable cabinet width would be about 13"; 1.5" on each side of the Driver to allow for cabinet width and internal braces.

As to the width at the 8" speaker, the drawing shows 10" but again, probably more like 11". Again 3/4" for the wood on the side, and 3/4" for the internal braces. That's not etched in stone, there can be some overlap between the 8" and 10" driver and the internal bracing. That's just something to fasten the fronts to.

The Dayton Classic 8" requires a 7.21 inch (183mm) opening and the Dayton Classic 10" requires a 9.22" (234mm) opening. As long as I have internal clearance for those, I should be fine.

I'm under the impression that the Baffle Step is related to the width of the cabinet in the area of the Bass driver. And one assume a narrower cabinet is a higher Step Frequency. Though I don't know how to calculate that.

If I assume this formula is correct -

f3 = 380 / WB (where WB is the baffle width in feet)

The F3 for an 11" cabinet width is 380/ 0.9167 = 415hz

Which to some extent blows my design concept. Especially if I am using the various crossover frequencies I suggested. If I use 500hz/4000hz, I might just as well run both speakers in parallel up to 500hz.

If I run the same calculation on the 10" driver, I get a step frequency of 350hz. Again, unless I'm misunderstanding, that somewhat blows my design concept.

Still, I do like the design concept, I'm just now at a loss of how to correctly implement it?

I guess, it we assume the numbers are right, then the WMTM would be workable. Use crossovers of 400hz to the two 4" full range, and a Mid to High crossover of about 3200hz.

It seems I need to give this a lot more thought.

Steve/bluewizard
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Old 10th December 2012, 06:15 PM   #16
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May I ask why the 2.5 way is indispensable....a FAST design with a 3-4" FR driver(like the fountek 88EX or so many other ones) allows a low crossover around 300Hz where no BSC is needed as frequencies are omnidirectional. And you can have a more simple design with so fewer passive components.
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Old 10th December 2012, 07:33 PM   #17
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2.5-Way design? Indispensable? Can you expand on that?.

Again, I'm working within a design concept, and the concept is based on a vision of the speakers I would like to see. But what looks good in my mind or my fantasies, doesn't necessarily work in reality. And that's partly what I'm trying to resolve.

That would be the speakers on the left in the graphic I included -

Click the image to open in full size.

That just seems a cool looking speaker. But cool does not = practical.

The speakers on the Right, still looks cool and is more practical, but it is more of a 3-way design than a 2.5-way.

The goal is good bass weight without drone. Clear clean midrange, which is important to me. I think Clear Midrange is best achieved by isolating the Midrange to a midrange speaker, hence a 3-way.

Upon looking at a variety of drivers, I find it hard to get a good blend between the low and the high in a 2-way system. If I want low-bass, then I lose midrange, and struggle to find tweeters that go low enough. If I sacrifice bass, I can gain in the midrange and better match the tweeters, but, of course, I lose bass.

This is especially true when using larger bass drivers. I could probably make this work easily if I were willing to accept 5" to 6.5" bass drivers. But in my mind, an 8" bass driver is small. Which is why I have selected a 10". I would like to have a 12" bass driver, and I do have 12" 3-way DIY, but they are big and bulky, and they weigh 50 pounds each.

So, I'm trying to come up with a concept that look cool, and sounds good. Something other than common as toast tower speaker. So, in my imagination, I came up with the 3.5-way design. Which in the ideal configuration would consist of a lower trapezoidal-ish cabinet plus and upper tapered trapezoidal-ish cabinet.

Even in my crude drawing, you have to admit it looks kind of cool.

But how to make it work.

Let me use this example to illlustrate a design concept. The link below is to the Wharfedale Diamond 9.6 (I have a pair) -

Product - Products - Wharfedale Hi-Fi

Twin 8" bass drivers (truncated frames) in a 3.5-way configuration. The cabinet width is 8.25", very skinny. Yet the crossovers are at 150hz between the upper and lower bass drivers. 1khz crosses the mid-bass to the 2" dome midrange, then the Midrange to tweeter crosses over at 6khz.

The Low-Bass (Half-Way) and the Mid-Bass are the same size, both with truncated frames, but they are not identical drivers.

Click the image to open in full size.

*** Note to Mods. This is my image, I own it, so I feel justified in using this link.

Notice the Mid-Bass has a Bullet in the middle, the Low Bass has a smooth inverted dome.

I don't believe that a 8.25" wide baffle face yields a Baffle Step Frequency of 150hz. So, there is obviously something I'm missing. In fact, I calculate a Step Frequency of 536hz.

These are very smooth sounding speakers, some would say a bit laid back, but excellent for music. A bit lean in the Midrange for videos though.

So, obviously the Low-Bass driver is not correcting for Baffle Step.

My original model of the 3.5-way projected possible crossovers at 150hz, 500hz, and 4000hz.

I also admit that I was somewhat influenced by this speaker design -

99W10.17P

The image at the top keeps changing, if you wait long enough you will see an image of that large bass unit, with this speaker on top -

93.23 (93 WMT)

You an see another photo here, though it is a bit small -

http://shop.xtz.se/images/P_6073_2_338-170.jpg

So, from this came the concept of Trapezoidal speakers, with a modest sized speaker sitting on top of a large Bass Driver in a separate cabinet.

All this combined in my mind, got shaken and stirred, and out popped the concept shown in my drawing on the Left. I still think it is a cool concept, it is just a matter of working out the details.

Obviously there is something I'm missing though.

Steve/bluewizard

Last edited by BlueWizard; 10th December 2012 at 07:49 PM.
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Old 10th December 2012, 09:31 PM   #18
mdocod is offline mdocod  United States
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Hello Steve,

So far as I can tell, that warfdale speaker is a traditional 4-way, and does not implement a .5 way, and for good reason...

Typically speaking you do not want different drivers with different characteristics sharing the same frequency range, except very low frequency ranges where we can live with far higher levels of distortion and are often trying to flatten out in-room response. Your desired implementation of a 0.5 way is not a good use of expensive crossover parts or the drivers themselves...

If you ran the 10" up high enough to cover step loss, then you'd have 2 different drivers with different characteristics sharing the lower mid-range, a good recipe for added distortion. (keep in mind, you have different motors moving different piston sizes of different weights. The summation of the 2 different drivers through the mid-range will undoubtedly have a higher resulting distortion than either driver through the same range played independently).

Also, if you run the 8" and 10" in the same system (not amplified independently), then the system will always be dynamically limited to whichever driver is the holdup for a given frequency. For example... If the 8" runs out of respectable linearity at 60hz at 16V, but the 10" has headroom at 60hz up to say, 24V, then you are forced to run both at the 16V limit in this case because they are sharing the same source. This IMO, is not desirable situation to be in as the benefit of the larger low frequency driver can not be exploited, so why bother in the first place?

To sum up... a 0.5 way doesn't jive well with the aesthetic arrangements of drivers that you are after when all powered from the same amp (whether you low pass the 10" below 150hz or run it up to cover step loss, either approach is undesirable here). I think you should be after a traditional 3 way approach here (I'd skip on a 4-way unless you have a very specific reasoning for it). Pic your 10" based on what sort of trad-offs you can live with in terms of efficiency/extension/output and work from there.

How much clean amplification will you have available with that single stereo amp?

Regards,
Eric

Last edited by mdocod; 10th December 2012 at 09:39 PM.
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Old 10th December 2012, 09:51 PM   #19
sreten is offline sreten  United Kingdom
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Hi,

You can use different drivers for a 0.5 way arrangement but
you need to do careful modelling to make sure one driver is
not compromising the other. Usually you arrange the lower
0.5 unit to run out of juice before the driver running into the
midrange, this is the idea behind a vented lower, sealed upper.

Making the 0.5 way driver bigger is problematic without some
skillful manipulation of two different bass alignments in parallel.

rgds, sreten.
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Old 10th December 2012, 10:15 PM   #20
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re:"the idea behind a vented lower, sealed upper" this would be good if you don't need the whole 6dB BSC, & probably a bit cleaner than having both drivers in the same enclosure

re: "skillful manipulation of two different bass alignments" - Thorsens 'compound driver' method is good - :
http://community.fortunecity.ws/rive...d/dddllqd.html
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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