Midbass Diameter - How to Decide?

[LineArray]

Hi,

what is the english term for a (small) woofer with
midrange capability ?

The german term would be "Tiefmitteltöner".
Would translate like "Midwoofer" ?
Don't know.

Cheers

 

[BHTX]

what is the english term for a (small) woofer with
midrange capability ?

I dunno about anyone else, but I've just always called them "mid-woofers".

 

[tinitus]

Ofcourse the driver in question is a midwoofer, and not a midbass ... silly silly
midbass can only be used to describe the frequency range ... unless you call it midbass driver

seems we have just had a minor problem in understanding english
Ofcourse I have all along been thinking of a "midwoofer" and have had no problem in understanding what Jim was asking about
maybe its a "benefit" that comes from not being "english"

Still, just a silly battle of words

 

[LineSource]

Explain to me why you would not ask your speaker engineers for a midrange that sonically excels over the vocal range of 80-1,100 Hz (E2 to C6) plus some upper margin for 2nd harmonic… say steep LR8 at 80Hz and LR4 at 1,500Hz..

Linkwitz selected an 8” midrange to cover 140-1,400 using LR4 in his well reviewed 3-way Orion dipole. Speakers like the Seas 8” Exotic with 10grams Mms cover this range with 93 db/watt SPL. Lambda is looking at a 10” midrange with 95db/watt and 20grams Mms for 8mm Xmax. New materials. New cone shapes. New motors. New opportunities.

Explain to me why you would not ask your speaker engineers for a 1” dome tweeter with Fs=400Hz, 95db/watt SPL and 1.5mm Xmax..

http://en.wikipedia.org/wiki/Voice_frequency
Fundamental frequency
The voiced speech of a typical adult male will have a fundamental frequency of from 85 to 155 Hz, and that of a typical adult female from 165 to 255 Hz[1][2].

http://en.wikipedia.org/wiki/Vocal_range
In terms of frequency, human voices are roughly in the range of 80 Hz to 1100 Hz (that is, E2 to C6) for normal male and female voices together.

A soprano is a singer with a voice range (using scientific pitch notation, where middle C = C4) from approximately (C4) to "high A" (A5) in choral music, or to "soprano C" (C6, two octaves above middle C) or higher in operatic music.

 

[tinitus]

You may not even need a tweeter...welll, maybe a supertweeter

Double 5" fullrange in 1.5way with maybe a supertweet

http://www.tb-speaker.com/detail/1208_03/w5-1611sa.htm

http://www.madisound.com/catalog/product_info.php?cPath=45_229_270_324&products_id=1179

 

[Artmaster]

hi all! in my opinion any time, any new loudspeaker project should be individual. i don't believe almost for any rules.
my mind, mine listening look-and-feeling not the same like other.
that's why you have to match combination of drivers for new loudspeaker yourself.
an ideal woofer + ideal mid + the best of the world tweeter - not the fact will satisfy you. of course - better component - better result, but any time is different. and everybody is different - so suggection couldn't help for success.
sometimes I have to throw away, discard some of my project, lucky time - I got acceptable result, but some - was perfect wish you get success at first attempt.

 

[tinitus]

that's why you have to match combination of drivers for new loudspeaker yourself.

Basicly we agree, but it may not be so easy if you lack any experience or even basic knowledge about whats available out there, or even whats at all possible

The one I suggested steers through some evident problems in speaker design, making a succes more realistic

 

[J.R.Freeman]

Thank you to everyone who made a constructive contribution.

Tinitus, to answer your question: this is a theoretical discussion. What I am interested in here, is fact and opinion relating to driver diameter. So you don't have to worry about system constraints like subwoofer efficiency and the like!

So my question, restated is: Considering only driver diameter, in the realm of home audio midbass drivers suitable for 2 way designs, what diameter or range of diameters is optimal? For the purposes of our discussion the midbass range will mean bass to upper mid-range.

So far, it sounds as though most of us feel this range is 5" to 7". I would have included 8, but it sounds as though 8 is difficult to crossover at the high end. I would have excluded 5 inches but perhaps they are worth a second look!

All in all thank you for your contributions. Line Array and Blue Wizzard, than you for your extensive posts - there is a lot I can learn from both of you! It seems there is no single answer to this discussion but it is interesting. It has influenced my thoughts on optimal diameter range already! Mmm a 6" Seas Excel would be beautiful, now if I were only rich

Jim

 

[tinitus]

Ahh, yes ok!

There is no general rule to driver size, its very much related to the specific driver and design...you can make a 2way with a 15" if you want
But looking at hifi drivers a 5" will make a fine little 2 or 2.5way fore low level listening
Using a sub...if you can use active highpass as well it will take more power
2ways with 5" is sonically rated among the very best and famous fore the difficult "dissappearing act"
A 6" will still have good midrange, and a bit more lowend and take more power, better sensitivity and so on...it always seems like a good compromise
8-10"...lets just say its possible, but we are approaching PRO drivers

PRO drivers is a different ballgame...apart from the big drivers there are several intersting smaller drivers...Zaph has just tested a couple of them

Very much is related to your SPL requirements

 

[GM]

TBH, I don't think an abstract definition will help, one needs to look at actual drivers to find which combine both the high freq characteristics AND bass characterisics desired.....usually it's a matter of compromise to get both, or an impetus to develop more complex systems....

Gees, you guys are 'killing' me here! You wanted a definition, I gave you some to choose from since like so many things in audio there's no real consensus other than 'it depends'. The charts are only meant as a guideline to define a speaker system's Fb range (or at least that's what they use to mean), i.e. a woofer system = 20-40 Hz Fb, mid-bass = 40-80 Hz, etc.. I mean have you ever read/heard someone describe a woofer by its useable HF response? Obviously, if a driver is meant to be tuned in whatever range, its description should reflects it so while a 15" driver may have a 20 Hz Fs, if its specs are tailored for a 40-80 Hz tuning, then it's technically a mid-bass driver, not a woofer. Unfortunately, marketing of an ever increasing choice of both consumer speakers and components has abused this simple system to the point of absurdity outside the prosound community, so we wind up with threads like this one.

Anyway, JRF's ~55 Hz system F3 falls in the mid-bass and how much ~flat BW it needs to reproduce is a function of the desired off axis response/XO slope, ergo for example if you only want to use its ~180 deg (point source) BW or beaming at ~90 deg at the XO point is acceptable, then a 15" either needs around a ~330-345 Hz or ~900-1200 Hz BW depending on the driver's effective diameter/diaphragm profile. How much you back off these numbers to find the XO point for a given slope will depend on whether you want to use just an electrical XO or an electro-acoustical one.

Obviously, there's other key design considerations, so while the theoretically perfect audio reproducer would be an infinitely small point source from DC-light (big bang?), making the smallest driver with specs to meet the desired F3 to get the widest practical useable BW is the goal, it must also be able to meet the desired peak SPL at low distortion, ergo it either has to have the Xmax and power handling to reach it at low thermal distortion or an acoustically large enough radiator requiring little Xmax/power.

Then there's the issue of where to put the XOs and how steep is acceptable and since there's both technical and perceived individual hearing differences involved in choosing them it seems reasonable to me to determine these first, then work your way backwards/forwards to find the rest of the system's specs based on well proven engineering principles rather than starting with the bottom driver and working your way up, which is rife with pitfalls as this thread depressingly highlights.

Me, I'm not much into compromise for a given app, so want the XOs outside my acute hearing BW, ergo 'big'/'medium'/'small' rules my cone/dome design sizing choices, which de facto resolves most of a multi-way design's worst 'pitfalls' and if I want just a two way, then 'big'/horn loaded 'small' driver.

As always though, YMMV and do where proponents of small two ways XO'd in our acute hearing BW and/or WAF abused congregate, so I'll get off my well worn 'soapbox' now (and probably none too soon for some).

Hmm, maybe I should change my "loud is........." signature to "Postcards from the Edge".......

GM

 

[KBK]

Midbass driver.

That means 'bridging the gap', ie, doing both. Mid and bass.

The best, as a single midbass driver system, tends to happen at about 6.5"-7" maximum, which tends to mean a cone size of about 6" diameter, maximum. Stiffness, directivity, and bass output tend to be the least compromised, as a usable PAIR, at about that size driver.

If one goes MTM, one has the possibility of going a bit smaller, to about a 4" mid-bass driver, but generally not bigger than the 7" driver, or not really any smaller than the 4" driver.

 

[J.R.Freeman]

Unfortunately, marketing of an ever increasing choice of both consumer speakers and components has abused this simple system to the point of absurdity outside the prosound community, so we wind up with threads like this one.

We're not talking about 'pro'-sound. The topic is midbass drivers suitable for home audio, 2 way systems, with modest SPL limits. The main question is: which diameters of such drivers are best suited for this range? For the cleanest, most accurate sound possible through this range in such an application, which diameters are best?

I agree, there are many more variables to consider, but this was supposed to be a general, theoretical debate to hear some opinions / facts on the matter. I think what we 'wind up with' in 'threads like this one' has less to do with marketing, and more with reactionary hostilities which server only to plunge the point well into the noise floor.

Though I don't agree that a 15" driver is a midbass (in the home audio realm), I found this interesting:

making the smallest driver with specs to meet the desired F3 to get the widest practical useable BW is the goal,

This gets to the heart of the matter, I feel. So, in a home audio 2 way midbass application, would the smallest driver possible for the required F3 be the goal? Usually a smaller driver will have higher extension, allowing for a higher crossover point. Now, my experience tells me that usually a smaller driver has better transient response performance, but is this just a function of Mms vs motor structure? If a larger driver has the same Qts, does it stand a chance in matching the transient response of the smaller?

 

[J.R.Freeman]

Midbass driver.

That means 'bridging the gap', ie, doing both. Mid and bass.

The best, as a single midbass driver system, tends to happen at about 6.5"-7" maximum, which tends to mean a cone size of about 6" diameter, maximum. Stiffness, directivity, and bass output tend to be the least compromised, as a usable PAIR, at about that size driver.

If one goes MTM, one has the possibility of going a bit smaller, to about a 4" mid-bass driver, but generally not bigger than the 7" driver, or not really any smaller than the 4" driver.

Well said! This certainly reflects what the market is tending toward these days. Interesting take on the smaller-than-ideal MTM setup. I wonder which system would be more accurate - one larger or 2 smaller? (generally of course)

 

[myhrrhleine]

Originally posted by BlueWizard
I would take the opposite approach to what Myhrrhleine said, though the difference in our approaches is more philosophical than literal.

I would go for the largest speaker I could find that would still give me the high range I needed. Of course, this assume that it would also cover the bass range as well.



why?
given otherwise identical performance, why largest?

I live by the philosophy that to get Big Sound, you have to move Big Air, and to move Big Air, you need Big Speakers.

From my perspective, with a few exceptions, an 8" speaker is the smallest I would go, and more than likely, I would use at least two of them. But I am also not likely to use a Sub, so my speaker (hypothetically) would have to deliver decent bass on their own.

I mean, I think Tang Band and HiVi make 1", 2", and 3" full range speakers (more or less), but can they move enough air so I can hear the bass?

So, from the perspective of solid uncolored uncompromising bass, I would go for the largest possible speaker that would fit the design requirements. And logically, the design requirements would include decent midrange response.

Now I readily admit that, in general, the larger the speaker, the less likely you are to get the midrange you need, but, conversely, the smaller the speaker, the less likely you are to get the bass you need. Somewhere in all our searching, we hope to find a speaker that reaches a compromise between the two.

5", 5.25", 6", 6.5", and in some cases 7" speakers have fair bass and fair midrange, though logically, they might require some tweaks.

An 8" speaker that can truly and functionally run up in the 2khz to 3khz range is a rarity, and in speakers that I can afford, an extreme rarity.


So, even with all their complexities, I tend to favor big bass big box 3-way designs. But even then, it is difficult to find three speakers that can smoothly mate together.

Steve/bluewizard

thanx for your reply

 

[LineSource]

There is some recent interest in higher efficiency speakers with 95-98 db/watt SPL. The list of reaons for this trend includes:

1) lower distortion from reduced cone movement and often lower moving mass than lower efficiency driver designs
2) lower distortion from reduced thermal/magnetic flux compression. Even Zaph notes this is a large component on midrange speakers.
3) lower distortion on the high (10-20db) transients in some recordings...especially classical and techno
4) lower power amp distortion from the 4x to 8x lower power demands. Nasty sounding hard clipping in solid state amps is often mentioned.
5) the desire to use "sweet sounding" low power amps, both tube and Class-A solid state construction
6) the perceived ability of high efficiency speakers to produce superor low level music details ...lower moving mass, reduced cone movement, etc...
7) old time religion


Example:
A 90db/watt 5" midrange like the Tang Band with 3mm Xmax bottoms out at 100 db at 120Hz @1m, or 320Hz at 115 db @1m in a sealed box. If you factor in 10-20db for musical transient peaks, then the Xover frequency would need to be moved up to avoid distortion unless very low listening levels are always used.

A 95db/watt 8" (or 10") midrange with a curvelinear cone profile for good off-axis upper frequencies and 6-8mm Xmax would easily handle 120Hz at 115db @1m. You could use tube or low wattage Class-A solid state amps without clipping distortion. I favor this type of high'ish 95-98db/watt efficient speaker design with modest power Class-A bipolar amps.

 

[The golden mean]

Line source,

You make a mistake in your first point. Cone movement for a given diameter will be the same to achieve a given SPL both in the case of a low efficiency and a high efficiency driver. The difference is in the electrical power to achieve this movement.

3) Is questionable as it´s much up to the design and general quality of the drivers.

6) Not necessarily a lower mms of a high efficiency driver as the motor is of great importance. And then again "the cone movement".

Your comparison between a 5" and an 8" is not up to a "fair comparison". Comparing drivers with the same cone area (Sd) and Xmax but with different sensitivity would be more appropriate.

 

[LineSource]

Your comparison between a 5" and an 8" is not up to a "fair comparison". Comparing drivers with the same cone area (Sd) and Xmax but with different sensitivity would be more appropriate.

My goal was to compare a modern design high efficiency 8"-10" midrange like the Seas Exotic or future Lambda 8" and 10", to a modern design 5" midrange like the Tang Band. The comparisons made were 5" to 8", since the thread is about selecting between size X vs. size Y, and not the best choice in size Z. I also presented the argument for putting the 80-1,500Hz vocal range on one midrange speaker, which is nicely done with a 7-10" driver.


If you think that the 8" is unfairly superior to the 5" as a midrange, then you have made your choice! If not, you can make the argument why a 5" midrange is superior to a modern design 8" midrange.

 

[The golden mean]

For sure you made conclusions about how loud the compared drivers could play and then both the cone area as well as the xmax is of importance. No need to compare them in your way as the orginal post was about quality, not "how loud can I play".

A 5" mid range would not be used at full service at 120 hz either.

 

[BHTX]

Cone movement for a given diameter will be the same to achieve a given SPL both in the case of a low efficiency and a high efficiency driver.

Completely false.

 

[Artmaster]

a woofer system = 20-40 Hz Fb, mid-bass = 40-80 Hz, etc.. GM

that's right. a lot of exist combination, but I think most important HOW does it lounding, not "from and to". that's why I hate Pro drivers, I never use it for home listening. and I always choose lightweight, sensitive mid and depend of it Fs commit at least 1 octave higher.
we've to pay attention for another issue - voice range. it shouldn't be parted. otherwise human voice will be distorted. I think an ideal system ( ) woofer section should be till 80 Hz, midrange - from 80 Hz - but it's force me to plan mid prety big size- 6" and even 8". IMHO