Relative Size of Drivers = how many of these to equal one of those?

BlueWizard

Distinguished Member
"...you do known that if you knock the xover of a mid down from 4k you don have to move the lfe point as well..."

First LFE is not the correct term. Precision of language matters (The Giver).

Next, I am well aware that the Mid/High can be move independently of the Low/Mid, which I can only assume you intended to say. But it can only be moved within a reasonable window. That reasonable window is roughly 3 octaves.

Those 3 octaves are frequently adjusted to better work with the realities of existing drivers, but if you have to deviate too far, you've got the wrong drivers.

Those 3 octaves are frequently adjusted to more conform to a unique design concept. But, 3 octaves is the starting point.

With an 800hz Low/Mid, a person could theoretically cross anywhere from 3000hz t0 7000hz. But I'll bet dollars to donuts, that in a vast majority of cases, the cross is going to be at 5000hz a majority of the time, because a full 3 octaves above 800hz is unrealistically high at 6400hz.

Let's look at some existing crossovers -

Generic 1 - 3-way = 800hz/5000hz
Generic 2 - 3-way = 800hz/4500hz
Dayton XO3W-375/3k = 375hz/3000hz
Eminence PXB3:5KO = 500hz/5000hz
Dayton XO3W-700/5.6K = 700hz/5600hz
Dayton XO3W-500/5k = 500hz/5000hz
Eminence PXB3:3K5 = 500hz/3500hz
Dayton XO3W-625/5k = 626hz/5000hz

Peavey 3DF1.2K/2.5K = 1200hz/2500hz (this is a special PA crossover)
Peavey ECS-3X = 500hz/2500hz (again, a special PA crossover)
PRV Audio 3DF400/1800 = 400hz/1800hz (also a PA crossover)

With the exception of the PA crossovers, we see something of a clear pattern.

Even the narrowest one, the Eminence PXB3:3K5 is just 500hz short of a full 3 octaves.

So, yes you can move the Mid/High independent of the Low/Mid, but only within a reasonable limits.

Steve/bluewizard
 
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Matyam

Active Member
We are talking about a single speaker (or pair of speakers), consequently there is no LFE, there is only that speaker and how it performs. We are talking about the design and construction of that speaker, not how to integrates it into a larger more complex system.

Now reasonably the system you put the speaker in will have some influence on the design. But as it stands, this is a stand alone speaker.

Both Low/Mid and Mid/High have to be in a reasonable working range for the drivers selected. Given that the Mids are 4", that leaves 3000hz or 4000hz on the high end. On the low end, the choices seem to be 350hz and 500hz. I explained the reason, and the advantages and disadvantages of both choices. While it is not locked in stone, the Midrange typically covers 3 octaves. But again, there is flexibility in that.

Three octave ups from 350hz is actually 2800hz. Three octaves up from 500hz is 4000hz. The 350hz crossover puts alot more strain on the Midrange drivers, because they cover the peak power band in the 250hz to 500hz range. Crossing at a higher 500hz, raise the Midrange right the the edge of its best functional range. All round it is a very fine balancing act.

As I said, the 3 octave Mid is not etched in stone, but it is very common. Though in a 3-way design, there is a limit to how low the tweeter can functionally go. It has to be over rated. By that I mean if it is functional down to 1500hz, then you really need to cross it in the range of 2500hz or higher to minimize excursion and to increase power handling.

Generally it is 3 octaves on the Bottom, 3 octaves in the Mid, and 4 octaves on the high end. But again, a lot of flexibility. Typically drivers do not work out on those boundaries, so you make do with the drivers in the range they do work in.

Steve/bluewizard

I posed for several years, though only casually in my mind.

The original concept was on the left of the two designs I posted. The idea was a 3.5-way design with the 10" and the 8" running in parallel at more or less below 200hz. Then from 200hz and above the 8" 3-way would take over. However, there were complications in that design, since I broke tradition and had two different sized speakers in the 0.5-way aspect.

So, I decided to make it a plain 3-way with the 10" driver as the single bass speaker. Next was the issue with crossovers. I originally thought that a 800hz/5000hz would work. But, I'm using 4" Midrange drivers, and at 5000hz, the start to Beam. That is, the field of sound begins to narrow, which creates a conflict in the smooth transition from a beaming Midrange to a non-beaming tweeter. If I force the crossovers down to 500hz/4000hz, I'm right on the edge of where the Midrange starts to beam, so that is probably a workable solution.

The last alternative was to drop down to 350hz/3000hz which put the Midrange in its best workable rang. But this has an additional complication, there tends to be a peak in the power distribution of music in the 250hz to 500hz range, centered on 355hz. If that range is running at 10 watts, the range just below it is running at 4 watts, and the range just above it is running at about 2 watts. So he see the peak power demand in this range is very high relative to the rest of the frequency spectrum.

Which leads to the concern that if I cross below 500hz, then I am putting that peak power demand on the Midrange speaker which are far less able to handle it compared to the bass driver.

Yada-yada, blah-blah-blah - what this adds up to is .... IT'S COMPLICATED.

I think as it stands now, I will use the Dayton Reference Aluminium 10" Bass driver. TWO 4-ohms 4" Dayton Reference Aluminium Full Range drivers, and a matching Dayton Silk Dome Tweeter, though I have decided specifically which one yet. I will cross at 500hz/4000hz, even though a few people have claimed that, for some undermined reason, 4khz is not the ideal place to cross Mid-to-High.

Then you need to download some software that will let you run simulations on a give speaker. Mine is complicated by the fact that my design is trapziodal, though I can calculate the equivalent in a rectangular cabinet. There are free version of Software out there.

Enter these parameters into the Software for the the specific speaker you are using. In this case it is the Dayton RS270-8 -

Thiele-Small Parameters
  • Resonant Frequency (Fs)27 Hz
  • Resonant Frequency (Fs)27 Hz
  • DC Resistance (Re)6.84 ohms
  • Voice Coil Inductance (Le)0.93 mH
  • Mechanical Q (Qms)2.08
  • Electromagnetic Q (Qes)0.61
  • Total Q (Qts)0.47
  • Compliance Equivalent Volume (Vas)3.4 ft.³
  • Mechanical Compliance of Suspension (Cms)0.57 mm/N
  • BL Product (BL)10.3 Tm
  • Diaphragm Mass Inc. Airload (Mms)35.8g
  • Maximum Linear Excursion (Xmax)6.6 mm
  • Surface Area of Cone (Sd)346.4 cm²
As it turns out, the site I am getting this information from has used a program called BassBox 6 Pro to determine the ideal cabinet sizes -

  • Sealed Volume ... 1.38 ft.³
  • Sealed F3.... 49 Hz
  • Vented Volume ... 4.5 ft.³
  • Vented F3 ... 25.6 Hz (F3 means -3dB response)
Which brings up a problem I mentioned before. A Sealed Cabinet can be small, but you limit the bass out put. In this case, it is limited to 49hz.

A vented cabinet can go super deep, down to 25.6hz, but it is a 4.5 Cubic Foot cabinet. (127.5 liters)

Just for reference, the speaker in the following photo, which I built in about 1985 are about 2.5 cubic feet (28"H x 17.5"W x 13"D). For the ideal size of the above driver, the cabinets about need to be nearly TWICE that big.

myspeaker-sm-jpg.85193


So, the purpose of the simulation is to find a compromise on the bass cabinet size that can give you a bass response close to what you want in a cabinet size you can reasonably tolerate.

If the lower bass cabinet in my original design is 24 inches deep, then the cabinet volume becomes 3.2 ft². Though you have to subtract the volume of the 10" bass driver.

Then we have to consider the output of the speakers. The 10" put out 87dB, unfortunately the Midrange only put out 84.2dB. That is less than ideal, but I might still be able to work with it. The Tang Band W4-1052D-4 4" midrange puts out 87dB, but it cost more money and has a lower power rating.

So, my point in telling you all this, even though it doesn't directly answer you question, is to establish that DIY Speaker Design is complicated.

As I said, I have been pondering the design I posted for years. Though since I can't afford to build it, I'm in no hurry. Constantly trying to refine it. Constantly trying to work out fine details of the design should I ever be in a position to actually build it.

So, let me say this -

Yada-Yada-Yada, Blah-Blah-Blah
... designing speakers is complicated.

There are several speaker design sites that have build and tested speakers, and published them as proven design. If this is your first speaker built, it is far far better to copy an existing design, than to try to create on from scratch. The custom design can be from simply bookshelf to elaborate much woofer designs.

For example, here is a speaker designed and built by a hobbyist in the UK -

View attachment 508560
So, again, best work with a proven design, of which many many designs are posted in various Audio Forums.

Sorry for rambling.

Steve/bluiewizard[/QUOTE]
Indeed the more I read the more complex It get but ignorance is bliss.So my monkey coffins 36x18x18 are my set point at moment as i cannot go higher than 36" because of projector screen .Now looking at various high end speakers that are built rectangle simply speaking these are just boxes on top of boxes ie wilson audio, now artemis signature using a more triangular box could it not give me the greater imprint on floor to give the same sort of box size as my cerwin vegas for the bass response i have now with a seperate pod for mid range and treble perhaps a la my kef iq 5se , all very simplistic i know but is this feasible ?
 

TB303

Active Member
Hello blueWizard, thanks for the fascinating info.
Can you help a math-challanged fellow?

I'm trying to compare the bass area of two speakers - the B&W CM10s2 (3x6.5" drivers) vs the Martin Logan Electromotion (1x8" driver). Would 3 drivers be counted as 1 drivers 3?
 

TomScrut

Well-known Member
Hello blueWizard, thanks for the fascinating info.
Can you help a math-challanged fellow?

I'm trying to compare the bass area of two speakers - the B&W CM10s2 (3x6.5" drivers) vs the Martin Logan Electromotion (1x8" driver). Would 3 drivers be counted as 1 drivers 3?
There isn't a lot of point in comparing the area anyway, just look up the bass outputs in the speaker specs? This comparison is probably only useful when DIYing where all other constants are equal such as volume and ports etc. Just look at how much more bass response (and less EQ needed) when comparing two sub's with identical drivers but one is ported, such as the SVS PB13 Ultra vs SB13 Ultra. The PB13 wins on output even though the SB13 actually has internal EQ in an attempt to boost the bottom few hz. Not that the SB is a slouch, I have two sat in front of me [emoji1]
 

BlueWizard

Distinguished Member
There isn't a lot of point in comparing the area anyway, just look up the bass outputs in the speaker specs? This comparison is probably only useful when DIYing ...

What is "bass outputs"? You have Frequency Response and general Sensitivity, neither tells you how a speaker sounds. Neither tells you how much air will be moved or how much bass output there will be.

When comparing speakers, how much bigger is a 6.5" (165mm) bass driver than a 5" (130mm) driver. While it doesn't seem intuitive, the 6.5" is TWICE as big as the 5". When buying speakers that is worth knowing.

2x8" are roughly equal to 3x6.5". When comparing speakers that is worth knowing.

If you are considering 2x6.5" and 2x8" speakers, how much bigger is the 2x8" than the 2x6.5", that might be worth knowing. Answer: the 2x8" are about 70% larger. That's might be an aid in helping you make your decision.

The same can be applied to Subwoofers. How much bigger is a 12" than a 10". Answer: about 53% larger.

The provided information tells you want it tells you, but no more than that.

Steve/bluewizard
 
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TomScrut

Well-known Member
What is "bass outputs"? You have Frequency Response and general Sensitivity, neither tells you how a speaker sounds. Neither tells you how much air will be moved or how much bass output there will be.

When comparing speakers, how much bigger is a 6.5" (165mm) bass driver than a 5" (130mm) driver. While it doesn't seem intuitive, the 6.5" is TWICE as big as the 5". When buying speakers that is worth knowing.

2x8" are roughly equal to 3x6.5". When comparing speakers that is worth knowing.

If you are considering 2x6.5" and 2x8" speakers, how much bigger is the 2x8" than the 2x6.5", that might be worth knowing. Answer: the 2x8" are about 70% larger. That's might be an aid in helping you make your decision.

The same can be applied to Subwoofers. How much bigger is a 12" than a 10". Answer: about 53% larger.

The provided information tells you want it tells you, but no more than that.

Steve/bluewizard
In the same way as looking at the figures doesn't tell you how a speaker sounds, working out the bass area doesn't either. But at least looking at figures shows how low it actually goes.

The only real judge is by using ones ears.
 

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