Midbass Diameter - How to Decide?

[J.R.Freeman]

Good morning all,

With the myriad of midbass drivers available, deciding upon one can be difficult. One critical decision (perhaps the first in the search-refining process) concerns driver diameter. What are some of the pros and cons to the various sizes? Are some diameters regarded as ideal for midbasses? Please feel free to jump in with opinions!

I'm something of a novice but I understand that application dictates to some extent hardware choice. So our theoretical driver pick needs some constraints. Let's say I want to build a 2 way system, we'll say with an F3 of about 55 Hz. It could be either sealed or vented (to make things more complicated)! The system will see a mid-sized living room at most, and will need to play at moderate volumes. So we don't need 120 dB @ 55 Hz or anything crazy like that. So just a good all around system with an emphasis on accuracy.

Now, from what I can tell, a smaller midbass of say 5 inches, would have an easier time reaching the upper end, allowing for a higher crossover point. So if we can cross over at say 3 KHz or higher, the crossover point is less audible. Also, would not the lower Mms of the smaller driver help with transient response? Unfortunately our F3 of 55 would be harder to hit, and would likely need a vented alignment.

Comparatively, a 8 inch driver would have much less trouble with that F3, and might be able to do it with a sealed enclosure. But added Mms I should think would mean worse transient response, even though sealed enclosures tend to favor transients. We wouldn't be able to cross over as high either. On the plus I have found mid range often sounds more natural through a wider driver, with less beaming.

Who can offer some factual insight to supplement my ramblings? I used to think the best bet was a larger midbass, but now I'm not so sure. I wanted to stay away from vented enclosures for the transient response of a sealed, but if a smaller driver can react more quickly, it stands to have a superior transient character even with the vent, which would also allow it to hit a lower F3 than it otherwise would be able to. With so many diameters, how does one pick?

Jim

 

[bzfcocon]

On the plus I have found mid range often sounds more natural through a wider driver, with less beaming.

I'm not sure what you mean with the statement above: a wider driver (I assume you mean a larger diameter) will have MORE beaming than a smaller one - it's one of the reasons you would want to cross over lower.

Overall, the choice depends of the tweeter or whatever you plan to use with that woofer: lower crossover points means you need capable(and more expensive) tweeters. It's a trade-off you should pick.

 

[Bill Fuss]

A good source of reference material would be Mr Krutke's zaphaudio website. Tons of info, read it all.

Bill

 

[J.R.Freeman]

Re: Re: Midbass Diameter - How to Decide?

I'm not sure what you mean with the statement above: a wider driver (I assume you mean a larger diameter) will have MORE beaming than a smaller one - it's one of the reasons you would want to cross over lower.

Ahh, perhaps I am using the term incorrectly. This is all subjective, of course, but I have found that smaller drivers to 'squawk' in the upper mid-range, and are noticeably directional (is that not 'beaming'?).

And to Bill Fuss - thanks for the reference. I will give it a read!

 

[Conrad Hoffman]

There are many ways to skin a cat. I've had little success with larger drivers, and very much success with the Dynaudio 17W75 (been a while- I think that's the right number), the 5" mid-bass, combined with a 1" dome tweeter like the Morels. That combination still likes a 4th order crossover for best results. It also needs bass cabinets or a sub to sound really good. I've had a few two way systems, but they never really satisfied me. The old Genesis went with a reduced size mid-bass, combined with a large passive radiator. That worked quite well. There are also the KEF "Q" speakers for home theater that use a 4 or 5" driver and perform well. IMO, the days of 2-way systems with large drivers have pretty much ended, and for good reason. BTW, I've also drifted to open back enclosures and think they have a much more natural sound quality.

 

[myhrrhleine]

Use the smallest diameter possible.
This is dictated by the lowest frequency sound desired and the loudest volume desired.

 

[tinitus]

6" i a good size that does it all, but I am not saying that any 6" will do

 

[BHTX]

I just received my 3 factory buyout "SoundTech" Eminence Delta Pro-12A's for $66 each (usually like $110+ or something).

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=299-500
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-510

..12" midbass for the win.
Planning on using them in a 3-way, probably with the DDS waveguide and BMS CD, with a 15" pro woofer highpassed 2nd order (for 4th order roll off) at 40Hz, at which point a few massive 18" TL's will take over. Crossover points will probably be about 40Hz, 200Hz, and 1500Hz, 4th order acoustic.

edit:
J.R.Freeman, I completely understand what you're referring to when you mention smaller mid drivers tending to "squawk".
I'm hoping that won't be a problem with my new project.

 

[J.R.Freeman]

Wow BHTX, that will be quite the system! Those look like nice 12's for sure.

Regarding the diameter debate, there are still a lot of questions. myhrrhleine said to use the smallest possible constrained by Fs and max SPL. But what advantage would a smaller driver have? Higher crossover point?

Mr. Hoffman I agree with your statement that they are many ways to get things done, and certainly there are a few answers to the midbass application. 5" seems small to me, but I bet what it can cover of the low range is nice and tight.

Does anyone know of, or have a link to, information regarding this dilemma?

Jim

 

[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.

Also, I take some exception to the general use of the term 'midbass', though I think it is being used correctly here. To me, and I could be wrong, 'midbass' means Midrange and Bass. I recently read a thread where someone wanted 'midbass' speakers that were large, went exceptionally low, and were loud. I thought to myself, he doesn't want midbass, he wants bass speakers. Sorry, just rambling.

I think, and again -generally, speakers 8" or smaller are the only speakers capable of midbass. There are probably rare exceptions, but anything 10" and above, is pretty much a straight bass speaker.

That said, I would also agree with Tinitus, that speakers in the 5" to ~6" range probably give the best results. There are many commercial speakers in this range that have clear clean mids and solid bass. So, I think this puts you in the sweet spot; large enough for good bass, small enough for good midrange.

But, as others have hinted, there are so many variables that it is almost impossible to nail down to a perfect range or size of speaker. But, I still stick to my philosophy of picking the biggest speaker that will do the job within a user's selected design parameters.

Yes, I know ...rambling...rambling.

Steve/bluewizard

 

[Conrad Hoffman]

AFAIK, "midbass" refers to a midrange speaker with a bit more bass capability than is traditional, maybe a bit longer throw and higher power capability. Those Dynaudio units I mentioned are only about 5" on the cone, but have a 3" voice coil that can soak up a lot of watts. The trick, as always, is to get enough overlap in driver response such that a reasonable crossover is possible. My experience is that few drivers larger than 8" can successfully mate up with most common dome tweeters. The old Large Advent's claim to fame was that they managed to stretch the response of a relatively large woofer up to meet an equally down-stretched tweeter. IMO, everybody who's serious about their listening eventually reaches the conclusion that, though a 2-way can be very good, a well designed 3-way (or more) will beat it on bass extension, vocal quality and probably efficiency. I'm talking traditional boxes here, not electrostatics, Maggies, or groups of drivers like the old Bose. Also IMO, a small set of speakers with a subwoofer qualifies as another 3-way or more system.

 

[tinitus]

Long time ago I made a 2way fore a friend, with a very nice 8" Seas and a Thiel tweeter, and it sounded quite nice fore a number of years
Now suddenly he doesnt think the mids are clean enough
well, thats the price you pay fore using such a big mid
Though today I may be able to do better using a notch and so on, but its tricky to get absolutely right...possible, but not easy
But certainly, the right 8" can produce quite "musical" sound, not superclean, but nice

 

[Brett]

Define midbass first would be a good idea.

 

[tinitus]

In this case I understand it as a standard hifi driver that does the deepest possible bass from around 40hz up to the high mids around 2.5khz

 

[lineup]

if we are talking midrange drivers, we are into 3-way systems, right?

In such case I will go for a 4 or 5 inch driver .. woofer
But with one important reservation:
Very low FS, frequency resonance

--------------------------------------------------------------------------
so
1. relatively small diameter, max 5" (100-125 mm)

2. woofer (not tweeter or dometweeter)

3. low FS .. above 100 Hertz is out of my question

4. high efficiency, sensitivity (I look only for SPL 92 dB or more)

5. robust and topclass mechancial construction = heavy, >= 1 kg (not less than 2 pounds!)
---------------------------------------------------------------------------

When following my very tough criteria there are basically only 2 (two) Brands that comes into my play:

1. Focal ... world's best drivers for hi-fi audio
expensive! but worth every penny

2. Audax ... very good midrange drivers with high efficiency
a bot lower in price, but Audax top line is always something extra

Lineup Audio Speakers forum - members only can read our stuff!

 

[tinitus]

if we are talking midrange drivers, we are into 3-way systems, right?

[/B]

He clearly says 2way in his very first post

Fore using a 10" or even 12" midbass, why not consider Gedlees Summa kit, which has the benefit of a compression driver going as low as 1Khz

 

[tpsorin]

Single 5" will not give you enough bass in large room. I would not use 5" in rooms bigger than 25sqm. you will probably need a subwoofer

For a large room 2way, I would recommend 2x6.5", 2x7". Or you can try 2x5" transmission line.

 

[The golden mean]

if we are talking midrange drivers, we are into 3-way systems, right?

In such case I will go for a 4 or 5 inch driver .. woofer
But with one important reservation:
Very low FS, frequency resonance

When following my very tough criteria there are basically only 2 (two) Brands that comes into my play:

1. Focal ... world's best drivers for hi-fi audio
expensive! but worth every penny

2. Audax ... very good midrange drivers with high efficiency
a bot lower in price, but Audax top line is always something extra

Lineup Audio Speakers forum - members only can read our stuff!

Sorry,
Focal don´t sell drivers to the public except for car audio. Of course some drivers for this destination can be used at home.

Audax, they have been into problems and possibly manufacturing of some drivers are kept running by some employees. It has been some notes about this in the German magazine Klang+Ton.

Perhaps someone can translate this into English? I can´t read French but I guess the headline says "The site isn´t available right now" Correct?

Audax

 

[myhrrhleine]

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 perfomance, why largest?

 

[J.R.Freeman]

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 assumes that it would also cover the bass range as well.

Also, I take some exception to the general use of the term 'midbass', though I think it is being used correctly here. To me, and I could be wrong, 'midbass' means Midrange and Bass. I recently read a thread where someone wanted 'midbass' speakers that were large, went exceptionally low, and were loud. I thought to myself, he doesn't want midbass, he wants bass speakers. Sorry, just rambling.

I think, and again -generally, speakers 8" or smaller are the only speakers capable of midbass. There are probably rare exceptions, but anything 10" and above, is pretty much a straight bass speaker.

That said, I would also agree with Tinitus, that speakers in the 5" to ~6" range probably give the best results. There are many commercial speakers in this range that have clear clean mids and solid bass. So, I think this puts you in the sweet spot; large enough for good bass, small enough for good midrange.

But, as others have hinted, there are so many variables that it is almost impossible to nail down to a perfect range or size of speaker. But, I still stick to my philosophy of picking the biggest speaker that will do the job within a user's selected design parameters.

Yes, I know ...rambling...rambling.

Steve/bluewizard

Thank you for the comment Blue Wizard - that wasn't rambling at all, I found it informative! I agree, the term 'midbass' is used too quickly sometimes. I might be off, but what I mean is a small woofer (or big midrange!) which would make for a nice 2 way, reaching down to 50 Hz or so, and being able to cross-over at 2 KHz or more. Your concept of largest driver possible is an interesting take on the problem. I share this point of view to some extent, as I've always liked 2 ways with 8" drivers. However, while considering designs for a 2 way studio monitor, the question of midbass diameter was to be revisited.

You mentioned 5" ~ 6" range. I have decided to give 6" drivers a second look, to get a feel for what is affordable in this range. My feeling is that on average, a 6" driver would perform better in the upper midrange, but give up some low end performance when compared to a similar 8" driver.

But this makes me wonder - is this generalization founded in fact? Will a smaller driver perform better in the upper midrange section (ie better distortion numbers, smoother response)? Or, is the truth in the data sheet? For example, say I have 2 drivers which are very similar in build. Same cone material, the 8 shall have more motor structure but more Mms so they'll balance and have the same Qts (in a perfect world!). We'll say the 8 can comfortable cover up to 2.5 Khz, and the 6 can do up to 3.5. Now I ask you, at 2 Khz, which will play the tone more accurately? I suppose what I am getting at is, generally, will a smaller driver cover upper-midrange material better than a larger, even if the larger is still within that range?

Hehe now I'm rambling!

AFAIK, "midbass" refers to a midrange speaker with a bit more bass capability than is traditional, maybe a bit longer throw and higher power capability. Those Dynaudio units I mentioned are only about 5" on the cone, but have a 3" voice coil that can soak up a lot of watts. The trick, as always, is to get enough overlap in driver response such that a reasonable crossover is possible. My experience is that few drivers larger than 8" can successfully mate up with most common dome tweeters. The old Large Advent's claim to fame was that they managed to stretch the response of a relatively large woofer up to meet an equally down-stretched tweeter. IMO, everybody who's serious about their listening eventually reaches the conclusion that, though a 2-way can be very good, a well designed 3-way (or more) will beat it on bass extension, vocal quality and probably efficiency. I'm talking traditional boxes here, not electrostatics, Maggies, or groups of drivers like the old Bose. Also IMO, a small set of speakers with a subwoofer qualifies as another 3-way or more system.

Hi Mr. Hoffman, I see what you're getting at about 'stretching' a driver's response. You've almost talked me into a 3-way system! But it makes me wonder which is the lesser evil: more crossover points of a 3 way, more bandwidth demand per driver of a 2 way? The system I am considering will use a subwoofer, starting from around 55 Hz down. So like you said, it is something of a 3 way system. But for the scope of this thread, I am concerned with the most accurate way to cover the range of 50 Hz or so on up. So nothing sub-sonic.

You do bring up an interesting point though, of keeping more drivers well within their range as opposed to less drivers reaching to hold hands at the finger-tips around the crossover point. But my feeling is a 2 way system for the 'mains' would probably yield the lowest coloration. However your influence may inspire me to reduce the size of my 'midbass' to something more of a midrange in size. Along with what Blue Wizard said, a 6" should be able to cover the middle band well.

***

Thank you to the rest who had something to add - I have read everything, but I am a slow typer, and it is dinner time . Quickly though, to Tinitus thank you for the suggestions but a 10" or greater 'midbass' (or woofer at this point) would conjure crossover tom-foolery beyond my 4th order (at best) mind! Tpsorin, your suggestion of multiple drivers to address SPL limitations sparks another interesting line of debate - which is better many small drivers, or few large? But in this context I am interested in the comparison of the performance of single drivers.

Jim