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Multi-Way Conventional loudspeakers with crossovers

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Old 11th December 2012, 03:06 AM   #21
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Quote:
Originally Posted by BlueWizard View Post
2.5-Way design? Indispensable? Can you expand on that?.


Steve/bluewizard
I apologise for the misunderstanding and thought your plan was a 2.5 way.
A 3 way with the woofer crossed to the mid at the baffle step will obviate the need for the extra 0.5. Can't figure out how an extra woofer will help, unless you want to extend the low end as low as possible by adding a subwoofer driver, crossed at about 80-100 Hz to your "woofer".
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Old 11th December 2012, 04:11 AM   #22
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This was really common in early Japanese speakers.
Some of the early Japanese units even had the .5 woofer sharing the same space as the main woofer
I have built a couple like that, where I wanted more bass, using the biggest cheap coil I could find (9.6mH ) on an 8R driver in a separate box under the tower, I have also experimented using 2*8R woofers in parallel with a 4R woofer in series and the 9.5mH coil in between the sets of drivers.
Whether it is 3dB or 6dB the extra bass was needed in these instances and really made the music substantial.
It works best I think in situations where the main woofer is a little bass shy and has a higher Fs ( over 40/60) but the main advantage I see is not having to pad down the other drivers to match the falling response of the woofer.
I wouldn't put a 3.5way speaker in a corner tho and if bringing the speaker out into the room I would put the .5 driver on the rear face.
There are some of us who prefer certain types of music with "In Ya Face BASS"
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Old 11th December 2012, 10:55 AM   #23
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I'm pretty sure the Wharfedale Diamond 9.6 are 3.5-way, but since I have them, when I get time, I can verify that by running some test tones. Four-way speakers are actually pretty rare, not non-existant, but rare. And the 4-ways that do exist are most often Tweeter/Super-Tweeter, rather than Low-Bass, Mid-Bass.

I understand the concept of the weaker driver setting the limits for the system. But I'm not quite sure how this is solved with a separate Low-Bass amp. Likely, with a separate amp, I would have to turn the 10" down to level match the 8".

The Dayton Classic 8" (for illustration) -

60w RMS / 120w peak
8 ohms
29hz to 3khz
88dB / 1W / 1m
Sd (relative) = 1.0
Sd = 211.2 cm²

Dayton Classic 10" -

70w RMS / 140w peak
8 ohms
25hz to 2.5khz
89dB/ 1w / 1m
Sd(r) = 1.63 (Meaning 63% more Sd than the 8")
Sd = 343.1 cm²

I don't see the gap between them as that great.

One alternative, would be to built the top section 3-way, then in a separate larger box, add another second 8" in a similar configuration to the original drawing on the Left. The larger box should allow the second 8" to go down as low as it is capable of going. But, I still like the idea of using the 10". But at the same time, I'm more than willing to learn that despite looking cool, it may not be a realistically functional idea.

But, if it is potentially functional, I'd like to know that too.

I'm also well aware that I can do anything I want, and yes, when I play music, I will hear music. But after spending all the time and money, I'd like the music to actually sound good; at least sound in reasonable proportion to the quality of components I used.

This is one of those ideas that pops into your head, and you just can't get rid of it. I still think it is a cool concept, but I also confess, I've never seen anything like it.

Other than the XTZ speakers I linked to -

http://www.xtzsound.eu/product-asset...ain/prod_6.jpg

The upper section is a stand alone bookshelf speaker. The lower section is a passive 8 ohm 10" (Seas) long throw bass driver. I don't think I need cabinets quite that big though.

Does anyone know of any designs that is even remotely similar to this concept?

Steve/bluewizard

Last edited by BlueWizard; 11th December 2012 at 11:02 AM.
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Old 11th December 2012, 11:08 AM   #24
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Also, this design influence my design concept -

Parts Express - Speaker Projects - Millennuim III by Mark Phillips

This is not a Half-Way system, the bass drivers in the lower cabinet are in parallel full time.

Again, a lot of influences came into play in arriving at this design concept, and obviously I have a lot to learn about speaker design. But, we all have to start somewhere.

Thanks for all the feedback.

Steve/bluewizard

Last edited by BlueWizard; 11th December 2012 at 11:12 AM.
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Old 11th December 2012, 11:40 AM   #25
sreten is offline sreten  United Kingdom
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Hi,

The 0.5 way principle really comes into its own for 2.5 ways and
3.5 ways with a relatively high x/o point for the midrange driver.

Makes a lot of sense in this design : Zaph|Audio - ZDT3.5

For a narrow MTM atop a pyramidal bass unit, making the MTM effectively
a 0.5 way in the midrange can make a lot of sense for some drivers.

rgds, sreten.
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Old 11th December 2012, 11:57 AM   #26
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"For a narrow MTM atop a pyramidal bass unit, making the MTM effectively
a 0.5 way in the midrange can make a lot of sense for some drivers."


Could you clarify that. It sounds like you are saying make the MTM a 2.5-way, and let the Lower Pyramid cabinet be a straight up "W" bass driver.

It seems, if I understood the first part of your statement correctly, I've been somewhat going in the oppossite direction. I've been trying to make the Mid-Bass/Mid-Range crossover as low as possible, and I hear you saying (if I understand correctly) that I should have been looking at higher Mid-Bass/Mid-Range crossovers.

I'll read the ZAPH article and see what it has to say.

Again, thanks to all who are taking the time to respond.

Steve/bluewizard
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Old 11th December 2012, 01:07 PM   #27
sreten is offline sreten  United Kingdom
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Hi,

True. If your looking at a low mid x/o point, two drivers and 0.5
way on the bass makes little sense compared to other options.

It makes more sense to 2.5 way a 2 way MTM top arrangement,
if the MTM is very narrow with a high BS transition frequency.
(And the drivers suit the full 6dB BSC of the 0.5 way arrangement)

A Speaker project

Is again another way of looking at the multiway problem,
the basses act as a 0.5 way mid driver for the midbass.

I can't say what is the best arrangement, depends on the drivers,
the type of design and what falls into place. Sometimes deciding
on incorporating an approach limits your effective / wise options.

rgds, sreten.
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Old 11th December 2012, 02:53 PM   #28
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I was planning to use one or two Dayton Reference 3" or 4" full range; depending on which project. Because they are full range they can pretty much support any crossover point without restriction ... above 100hz that is.

I guess because they can go so low, I was fixated on a low crossover. '

Using my drawing on the RIGHT, the MTM, with a W in a separate box. The baffle width for 4" speakers seems to be about 7.5 inches. That may not be right in practice, but it serves as an illustration for now. That equals a 608hz Baffle Step Frequency.

Using the formula F3 = 380/Wb.

Certainly the 10" bass driver will have no trouble going up to 600hz. But do I let the Mid go down as far as they can (80hz rated), or do I treat the system as a 3-way. I guess with a 10" bass driver, the 4" really don't add that much, so I might as well treat is as a 3-way. Tentatively with crossovers at 600 and using the 3-octave guideline, 4800hz. Though I notice the virtually no one adheres to the 3-octive midrange rigidly.

With a roughly +4khz Mid/High crossover, I should have a vast selection of tweeters to choose from.

As this discussion compels me to ponder the potential problems, as has been mentioned there is an in room boost to the bass. But with the 10" relatively close to the floor, can I count on a floor boundary boost? And with all that boost, can two 4" Mid driver in Series keep up? I suppose rather than 2x 4ohm in series, I could use to 8 ohm in parallel, but one of my other design objectives was to create a speaker as close to 8 ohms as possible. But I can probably get by with 4 ohms in the Midrange.

Logically, I should probably start with the (W)MTM. Once I have the lower bass box, I can try various configurations of that bass box with existing full range speakers just to see if there is someway to make it work. If I can reasonably find a framework in which it works, I can then go ahead and build the 8" 3-way.

The problem is, I'm obsessed with the original 3.5-way design because I think it would make a very cool looking speaker with the tapered boxes. But, am I willing to trade "looks cool" for "sounds good". I don't think that is a trade off I can make. But, if I can think of a way to make it sound good, then I'm certainly willing to give it a try.

Again, thanks to all who replied. Even though I'm starting to see the folly of the design, I still want it to work.

Thanks again.

Steve/bluewizard
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Old 11th December 2012, 11:07 PM   #29
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And as I said Steve I see no folly in the question and I also like the "Look" of the tapered box although I've not built one. I think the baffle will be wider than that because you will need to offset the drivers a little. My usual suggestion is to make a cheap box , built it and listen I wish I took my own advice
This is one of my 3.5Way speakers

Mirror image pair | Flickr - Photo Sharing!

This is the unit with the 2 woofers in parallel and the ~9mH coil in between the sealed 10 inch and the OB 8s
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Old 11th December 2012, 11:22 PM   #30
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by BlueWizard View Post
The problem is, I'm obsessed with the original 3.5-way design because I
think it would make a very cool looking speaker with the tapered boxes.
Steve/bluewizard
The driver arrangement could be made to work if you know what you are doing,
(modelling), with BSC aspects to the slopes of all the three bottom drivers,
and thus the relative senstivities of all three chosen drivers, its complicated.

Chuck in boundary reinforcement and its gets even more complicated.

rgds, sreten.
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