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-   -   The HALF-WAY House ...er...Speaker (http://www.diyaudio.com/forums/multi-way/225307-half-way-house-er-speaker.html)

BlueWizard 9th December 2012 09:41 AM

The HALF-WAY House ...er...Speaker
 
At this point I'm looking for some philosophical advise.

This has to do with the underlying philosophy of Half-Way system, as in 2.5-way, 3.5-way speakers.

Here is a hypothetical speaker that I am thinking of building.

Start with an 8" 3-way bookshelf speaker. Then under that in a separate box put a 10" bass driver. Now, I'm trying to create a 3.5-way system, not a 4-way. And the 10" driver is a standard woofer, not a subwoofer. The whole setup will be driven by a single stereo amp.

In all the Half-Way designs I see, the Half-way speaker is always the same size as the woofer, if not the same speaker. But is that necessary?

For example, since the main speakers has an 8" bass driver, the half-way systems I see would compliment that with another 8" bass driver, but why? Why not 8"+10" or 8"+12".

Now admittedly this potential speaker build is intended to be on the bass heavy side, though reasonably so. I still want a clear balanced speakers, just with a trace more dominant bass.

So, I'm looking for an overview of Half-Way systems and the logic to choosing specific speakers, and how ridged is that? I see what is commonly done, but why is it commonly done that way?

Steve/bluewizard

Melo theory 9th December 2012 03:40 PM

You can use any driver you want as long as the impedance is still high enough when halved.
In fact it would be wiser to use a different driver with less sensitivity because never do we need a full 6db of baffle step compensation, unless used outside.

picowallspeaker 9th December 2012 04:31 PM

It's quite common to see bunch of drivers stacked on the baffle.
Something such WMTMW or woofer woofer woofer :p
Also to use multiple subs which is not a philosophy but a way
to take control of room modes ( as they are 'activated' by different located sources ).
Such a design you describe exists , it can be done with common woofers such as Dayton classic 10" woofer,one in a separate box at the bottom and one at the top. The central unit should carry no bigger cone than a 5" :o:rolleyes:
as it's supposed to work over 2-300 Hz.

BlueWizard 9th December 2012 04:58 PM

The Center Unit, by that you mean the midrange?

The Key here is that the 10" in a separate cabinet will not match (in terms of size) the 8" woofer in the upper cabinet.

Using Dayton Classic as an example. The Classic 8" has a Sensitivity of 88dB. The Classic 10" have a Sensitivity of 89dB, and based on Dayton specs, the 10" has a 62% larger surface area.

In the 3-way section, keep in mind the plan is all in my mind at this point, I'm thinking of something in the traditional 700hz/5khz or 800hz/5khz range. Though given the midrange I plan to use 500/4000hz is possible too. Then cross the 10" at something like 150hz (give or take).

I realize anything can be done. But I'm interested in the general design philosophy around Half-Way designs. It occurred to me after I posted, that some Half-Way design are a way to compensate for Baffle Step. Below the Baffle Step, the volume drops -3dB, and adding a second identical bass driver boosts the bass by +3dB. So, you have smooth bass to much deeper values.

When the time comes, I will give some consideration to Baffle Step in choosing my low bass crossover frequency. But in the early stages, I'm simply concerned about the repercussions of implementing the Half-Way with a low-bass driver that is 62% larger than the main Mid-Bass driver.

I'm looking for a bit of extra bass, but not droning dance club bass, I still want clarity top to bottom, within my budget, but with a hint of extra bass.

Plus I feel the 10" will go deeper than the 8". I would like to take it down to at least 30hz. In this case I can skimp slightly on the size of the 8" cabinet and lose a small degree of bass, then make up for that with a substantially larger 10" cabinet.

Right now my thoughts are either Dayton Classic or Dayton Reference, depending on the actual budget. 10" low-bass, 8" mid-bass, 3" or 4" full range for the Midrange, and one of many standard 1" tweeters.

But at this point, I'm concerned as to why all Half-Way systems I see all use the same size Low-Bass and Mid-Bass, and what the negative (and Positive) repercussions are of implementing a Half-Way system with an 8" and a 10"?

Steve/bluewizard

6L6 9th December 2012 05:12 PM

Quote:

Originally Posted by BlueWizard (Post 3277521)
Then cross the 10" at something like 150hz (give or take).

Plus I feel the 10" will go deeper than the 8". I would like to take it down to at least 30hz.

And to clarify, you are planning on running the 8" with no high-pass? I.E., from it's low-end roll-off to the woofer/midrange xover?

With a 150hz cross on the 10", you are describing a subwoofer.

Melo theory 9th December 2012 05:15 PM

Quote:

The Key here is that the 10" in a separate cabinet will not match (in terms of size) the 8" woofer in the upper cabinet.
The size is not important. The impedance is.

Quote:

Below the Baffle Step, the volume drops -3dB, and adding a second identical bass driver boosts the bass by +3dB. So, you have smooth bass to much deeper values.
No, amplitude drops 6db with no boundaries. In room it doesn't. Probably more like 3db. Adding a second woofer and putting a capacitor on it will double sensitivity of that woofer plus the other woofer producing the same signal, that's 6db.

Quote:

When the time comes, I will give some consideration to Baffle Step in choosing my low bass crossover frequency. But in the early stages, I'm simply concerned about the repercussions of implementing the Half-Way with a low-bass driver that is 62% larger than the main Mid-Bass driver.
You are going to have way too much bass, when you consider the added sensitivity of the larger driver, the extra 3db and room gain.

Quote:

I'm looking for a bit of extra bass, but not droning dance club bass, I still want clarity top to bottom, but with a hint of extra bass.
The best thing to do is find a larger driver with about 3db less sensitivity.

Quote:

But at this point, I'm concerned as to why all Half-Way systems I see all use the same size Low-Bass and Mid-Bass, and what the negative (and Positive) repercussions are of implementing a Half-Way system with an 8" and a 10"?
Probably to keep the baffle thin.

picowallspeaker 9th December 2012 05:25 PM

Indeed, I was thinking of a 'central unit' composed by mid-high efficiency
drivers, around 95 dB. A Motorola piezo tweeter might come into the mix.
Also an active crossover between the units to enhance headroom from the
amplifiers.

6L6 9th December 2012 05:29 PM

Quote:

Originally Posted by BlueWizard (Post 3277521)
But at this point, I'm concerned as to why all Half-Way systems I see all use the same size Low-Bass and Mid-Bass, and what the negative (and Positive) repercussions are of implementing a Half-Way system with an 8" and a 10"?


Answering this question specifically -

A. They can use the same driver for the BSC woofer, and that saves money.

B. With a row of say, 6" drivers, the baffle can be kept narrow. Wide speakers don't sell.

C. There are some designs with a bigger BSC woofer, but they are usually side-firing.


Like this - http://www.productwiki.com/upload/im...ega_cmx_28.jpg

BlueWizard 9th December 2012 09:57 PM

Quote:

Originally Posted by 6L6 (Post 3277535)
And to clarify, you are planning on running the 8" with no high-pass? I.E., from it's low-end roll-off to the woofer/midrange xover?

With a 150hz cross on the 10", you are describing a subwoofer.

High Pass? No, the upper box is a standard 3-way. The 8" goes from zero to 500hz, the midrange goes from 500 to 4000hz, and the tweeter goes from 4000 to infinity (OK, not infinity, 20khz).

The 10" will run in parallel with the 8" up to about 150hz, making it a Half-Way since it doesn't have its own frequency range.

All the drivers will be passive, no active amps or crossovers.

When I said the 10" would not be a subwoofer, what I meant was not a driver classified as a subwoofer driver. Rather a standard woofer. You can functionally classify it any way you want, but the driver I buy will be a woofer.

Configuring the speaker this way probably means the system will be 4 ohms between 30hz and 150hz, but I think I can live with that. Though I might be able to use a Dual Voice Coil driver for a total of 16 ohms, which would mean a final impedance of 5.3 ohms which is some help.


An alternate configuration, would be an MTM upper section, covering midrange and tweeter, then just use a single 10" bass driver in a separate box.

If I use two 4" full range speakers for Midrange (4 ohms wired in series), I should still be able to cross relatively low. Perhaps 500hz/4khz. Though, I could cross even lower as the Full Range 4" go down to 100hz.

In my mind, I see the upper section as a somewhat standard rectangular box, but I envision the bottom section in the shape of a trapezoid; Wide at the bottom with perhaps room for front ports, and tapering as it rises to meet the Upper Section. Though I don't imagine it could be tapered enough to match the size of the upper section.

I prefer the 3.5-way over the 3-way, but perhaps the Half-Way aspect in this situation is too complicated. Still, when the time comes, 3.5-way is going to be high on the list.

Thanks for the responses so far. I realize my questions are somewhat vague, but I need to start somewhere.

Steve/bluewizard

PeteMcK 10th December 2012 12:24 AM

re: "that some Half-Way design are a way to compensate for Baffle Step' - all .5 way designs are, so the xover freq to the .5 way driver should be the baffle step freq

re"Then cross the 10" at something like 150hz " - that's turning it into a 3 way + sub system , unless you have a very wide baffle... (or are just a bass freak...;))

re:"why all Half-Way systems I see all use the same size Low-Bass and Mid-Bass" - it's just easier to match sensitivity & xovers that way, but you can use different drivers...


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