# WHen and why to enclose a mid range



## preston (Dec 10, 2007)

I've got lots of room on my pillars/dash and was curious about sealing up the enclosure for a mid-range. Obviously because of the package difficulties this is usually not done. But I was watching a PSSOUND video where he built a 1.2 liter enclosure for some 4" mids (and in another video, used the same mids in the pillar with no enclosure). 

I assumed this was to support lower frequencies such as if you wanted to run that 4" down below 150Hz. But I was modelling some midranges in WinISD and honestly I couldn't really see the pattern. My thought was that either it increases SPL or improves cone excursions. Using hte T/S specs some of the midranges ended up with really small enclosuers like .02 ft3 for a Q of .707.

Whenever these types of midrange drivers are used in bookshelf home audio, they are always enclosed obvioulsy albeit ported. And these enclosures are usually more like 2-3 liters (more like .1 ft3 rather than .02 ft3)

So what do we accomplish if we seal up our mids that I am somehow not seeing in WinISD ? This is all in the context of staying above 100 Hz. I've been running my dash mids between 180 and 250 and I prefer the sound at 180 which is fine at lower volumes but I can hear distortion when I turn it up. 

So when and why would I endeavor to enclose a mid range and would I still look for a Q of .707 when building the enclosure ? Does .02 ft3 even make sense ? Most of these mids have a VAS around 2-3 liters, which is more like .07 to .1 cu ft. 

I feel like I am making a mistake when modelling these as I usually only model subs, but trying to understand if sealing the midrange (or even building a ported enclosure just for fun) has any benefits. 

(whether there are any benefits to running my mids that low is a different question, yeah I know we can't theoretically localize < 300 Hz, but for some reason I feel like the stage and upper base tonality sounds better when I run them lower. I have Legatia L8's in very well prepared doors)


----------



## GEM592 (Jun 19, 2015)

I think sealing an (upper) midrange is a great way to improve output, power handling, and usable bandwidth. Highly underrated. 

What will typically happen is your enclosure will be too small to get full potential bandwidth (even for that little driver), but you will get better output than you otherwise would have down toward the lower midrange, without losing high end performance. 

So, whether you want to do this or not is highly dependent on your install, what is below the midranges, etc.


----------



## preston (Dec 10, 2007)

Any thoughts on how I would model this in WinISD and understand it ? I mean I know how to model it, I'm just not really seeing the increased output, bandwidth, or lessened cone excursion in my results unless I model it ported.
I guess that would be kind of hard to explain over the internet, maybe I just need to drill down into the graphs more but in the few minutes I spent on it I couldn't see any improvement on the screen from putting boxes of varying size around these things. I was using an legatia L4 (designed for IB), a scanspeak 12M, a Seas Excel coaxial and the BMS coaxial that ErinH is using, all 4.5" - 5" midranges. I dont' know about the BMS but the Seas and the Scanspeak have application notes for building a home audio speaker box (ported) of 2-3 liters.


----------



## GEM592 (Jun 19, 2015)

If this is for Hybrid Legatia L8s, I might advise you against sealing due to low ROI. You pretty much never want to seal a woofer of this size in a car - you practically can't get the enclosure big enough to beat the benefits of good door treatment.

I thought you were considering sealing high frequency midranges, sorry for any confusion.


----------



## GEM592 (Jun 19, 2015)

The larger the midrange is, the harder it will be to practically seal and be worth the trouble over a reasonable door install/treatment. Even in the 4 or 5 inch range, it becomes difficult. Just about any enclosure will be too small to give reasonable extension.

But, to stay on point you might want to consider even smaller (say 3 inch) options, which often can be practically sealed, possibly leading to better overall performance, depending on practical considerations of the vehicle and other equipment.


----------



## preston (Dec 10, 2007)

My impression is that 1-2 liter enclosures would be appropriate for most 4" mid ranges, which is only 122 ci. That should be pretty achievable in a larger dash pod. 

What I don't understand is why WinISD calculates an enclosure of .001 liters for a Q of .7x and an FS of 183. I know that can't be right becuase the VAS on these drivers is more like 2-3 literes and the recommended ported box for one of them is 2.3 liters. I expect the proper enclosure to be in that 1-2 liter range and yet when model that it acts like IB, and doesn't really affect the curve until it gets super tiny and then only mildly. I feel like I must have some parameter entered wrong but I'm reasonably familiar with the tool and the specs.


----------



## Focused4door (Aug 15, 2015)

I use this order for entering driver paramaters:
Red Spade Audio: WinISD - entering new driver data

Often times it is a units issue if it is way off.

Double check the parameters that would be calculated to verify against the manufacturers T/S parameters.


----------



## GEM592 (Jun 19, 2015)

preston said:


> My impression is that 1-2 liter enclosures would be appropriate for most 4" mid ranges, which is only 122 ci. That should be pretty achievable in a larger dash pod.
> 
> What I don't understand is why WinISD calculates an enclosure of .001 liters for a Q of .7x and an FS of 183. I know that can't be right becuase the VAS on these drivers is more like 2-3 literes and the recommended ported box for one of them is 2.3 liters. I expect the proper enclosure to be in that 1-2 liter range and yet when model that it acts like IB, and doesn't really affect the curve until it gets super tiny and then only mildly. I feel like I must have some parameter entered wrong but I'm reasonably familiar with the tool and the specs.


Yep something is wrong. I don't use WinISD at all, so probably can't help too much. For a 4 to 5 inch midrange I agree 1-2 liters is reasonable, and if you can fit it and construct it properly (no air leaks, tight as possible) you will probably have a good time if you have some tuning and patience.


----------



## eststang (Nov 28, 2010)

Preston,

I do not know either what to look for in WinISD graphs for midranges, but some (most?) reputable manufacturers give their specific recommendations for their midrange drivers enclosures. For example HAT Legatia SE manual says theirs are designed for IB (https://hybrid-audio.com/files/manuals/06_LegatiaSE-Components-Manual.pdf page 6). OTOH Audiofrogs GB25 is optimized for sealed enclosure as small as 0.2 liters (https://www.audiofrog.com/gb25-2-12-63-mm-audiophile-grade-automotive-loudspeaker/) etc.


----------



## LBaudio (Jan 9, 2009)

I had some really good results putting midbass drivers in ported enclosures, in a few occasions even in sealed enclosures. But there were some installs and drivers that didnt perform well under such conditions, mainly due to too high QTC.

enclosing mids is usually not necessary - since you dont need to control that 2-3 mm of excursion, and in many cases enclosure might colour the sound and make it dull, me personally prefer back vented midranges.
Also forcing mids to play under 250-300 Hz is not good, why not use larger midbass drivers to cover that freq. area - you will get stronger output, a lot less distortion, and better power handling


----------



## Bayboy (Dec 29, 2010)

Modeling is only going to tell you so much..... response, excursion, and a few other things. Enclosing a mid or midbass isn't a bad idea, but it often turns out bad by using the wrong drivers. If the driver is designed to be ran IB, then run it so. If you desire enclosed, choose a driver that is maximized by such. Some drivers can cross the streams, but you'll need to do your homework to see which will and to what advantage.

I will lend a clue on one area most have a problem with. Most are concerned with the relative roll-off point, but underestimate the response below F3 and especially in a car. Yes, IB has more efficiency down low, but the advantage of enclosed is negating the associated rattles of door IB. The sealed response below F3 isn't a bricked one, so take that into account. 


The same holds true for a small mid.... give the same attention like you do subs. 


Sent from my SM-G955U using Tapatalk


----------



## preston (Dec 10, 2007)

Good thoughts guys.
First off I'm fully up to speed on some drivers being optimized for IB so no worries there but I've been moving into the raw/catalog driver world where things aren't so clear cut. I was using some other online box calculators and cruising through recommended box sizes on parts-express and it seems to be true that the math gives tiny box sizes for these mids (like .024 cu ft /0.5 liters for a 4-5"). Although the parts-express specs specifically say they're calculated using software so they are getting the same results I am, that's not necessarily some manufacturer suggested box size. 

There is this from Audio Frog for the 4" GB40 "the GB40 is optimized for an infinite baffle application or an enclosure of at least 1 liter."
And interstingly enough I modeled this and the suggested sealed box size was 4.5 liters (0.154 in3) ! Whereas the Scanspeak 12M it suggested 0.5 liter. That's a big difference for 2 speakers fairly close in size. 

My own experience is that a speaker would sound like crap in a tiny box (< 1 liter) 

As an experiment if I built new pods I might make them ~1 liter and sealed, but will leave myself a location to open the pod up and vent it down into the dash or a-pillar and see for myself what happens. 

Gotta admit it would be an interesting experience to try and build a ported pod on the dash and run it down. Whenever you see an expensive book shelf speaker using small drivers its a vented design and they run them down to 90 hz. I guess we never do that in car audio because we have so much bass available anyway. Its interesting how the home audio guys almost never use bi-amping or active control above the subwoofer level, and prefer to put hundreds of hours into optimized passive x-overs.


----------



## GEM592 (Jun 19, 2015)

Focal 3krx3 3 inch mid comes with the recommendation sealed, 0.3 liters and it works. Even smaller helps, you get less low end is all. So very smallish enclosures are definitely possible.


----------



## Bayboy (Dec 29, 2010)

"Fully up to speed on some drivers being optimized for IB", then there should no confusion with raw drivers regardless of implementation. 

Sent from my SM-G955U using Tapatalk


----------



## Nirvana (Sep 18, 2009)

I'll throw some comments out from a speaker-builder perspective. Car audio imposes constraints that just don't allow for all possible practices.

A midrange is operated in a passband that is usually a good 2-3 octaves above Fs. In these situations, the enclosure doesn't really impact the performance of the driver. However, housing the midrange in a too-small enclosure can introduce low frequency peaking which may very well be audible even if it is outside of the passband.

Enclosure size can be used to control driver roll-off and also the driver impedance. For an active configuration, this is less interesting to optimize.

You could go full open baffle where the mid operates as a dipole, but this is just not feasible in a car environment. Alternatively, the most significant function of a midrange enclosure is control of the back wave. Effective solutions make use of a shaped transmission line and strategic damping. This too is difficult to achieve in a car environment. However, that space behind the A-pillar trim could be properly damped to dissipate the back wave.

That AudioFrog GB25 is a sub 3" midrange with an Fs twice what larger midranges, including the GB40 typically have.


----------



## preston (Dec 10, 2007)

Bayboy said:


> "Fully up to speed on some drivers being optimized for IB", then there should no confusion with raw drivers regardless of implementation.
> 
> Sent from my SM-G955U using Tapatalk


Not exactly sure what you are getting at, I just meant I know that a lot of car audio midranges are marketed as IB and 90% of people install them that way.

I guess the only thing I'm confused about is the huge difference in enclosure sizes as everytime I've seen a sealed mid they use at least 1 liter of airspace and its strange to me that the models recommend such tiny airspaces for most of the mids I am looking at and that I'm not seeing any obvious improvement in the model for doing so.


----------



## Bayboy (Dec 29, 2010)

preston said:


> Not exactly sure what you are getting at, I just meant I know that a lot of car audio midranges are marketed as IB and 90% of people install them that way.
> 
> I guess the only thing I'm confused about is the huge difference in enclosure sizes as everytime I've seen a sealed mid they use at least 1 liter of airspace and its strange to me that the models recommend such tiny airspaces for most of the mids I am looking at and that I'm not seeing any obvious improvement in the model for doing so.


If you're referring to Partsexpress recommendations, consider that they're using Bass Box Pro and are targeting home audio where someone might be trying to use the full extension in response. In a car, we mostly don't. In fact, most small widebands are at a disadvantage since the Fs is much lower than where we cross them, yet xmax is quite low also. IE... not quite as good as a true midrange. However, if I was to enclose one, I'd look for one that will take advantage of being enclosed. Perhaps the SB wideband with its longer throw and mid Q. 

Sent from my SM-G955U using Tapatalk


----------



## tonny (Dec 4, 2010)

If you need a closed box for a midrange depends on different things... The application in the car it self and the room you have te instal the speakers, off course it also depends on the speaker what it likes, and what the rest off the instal does. 

Normale a box only helps the driver arround the fs and we like to filter our midrange drivers well above the FS so the box would not do much good for that, or it must be a midrange that needs to play lower as it normally does trough the midbass or sub below it is not capable off playing high enough or so. 
The down side off a small closed box is that the driver can be to closed up and there is a lot off internal reflections that will effect the driver.... Normally I like to keep the midrange enclosures as open as possible so the driver has room to play in there is more benefit to me then the little extra lowend that my midbass plays much better.


----------



## preston (Dec 10, 2007)

tonny said:


> If you need a closed box for a midrange depends on different things... The application in the car it self and the room you have te instal the speakers, off course it also depends on the speaker what it likes, and what the rest off the instal does.
> 
> Normale a box only helps the driver arround the fs and we like to filter our midrange drivers well above the FS so the box would not do much good for that, or it must be a midrange that needs to play lower as it normally does trough the midbass or sub below it is not capable off playing high enough or so.
> The down side off a small closed box is that the driver can be to closed up and there is a lot off internal reflections that will effect the driver.... Normally I like to keep the midrange enclosures as open as possible so the driver has room to play in there is more benefit to me then the little extra lowend that my midbass plays much better.


Thanks, wording the explanation that way makes a lot of sense especially the part about internal reflections.


----------



## Patrick Bateman (Sep 11, 2006)

Andrew Jones is a well regarded designer. He's designed speakers for Kef, Tad, Pioneer, and now he works for Elac.










Back in the day, he did an interesting 'trick' with these Infinity PFRs. He basically put the midbasses in a ported enclosure that's way too small. This raises the F3 quite a bit, but also creates a big ol' peak in the midbass. In the measurement above, the midbass has a 6dB peak at 160Hz.

By doing this, it raised the output by about 6dB in the midbass. This would be equivalent to using four midbasses instead of one.

I can't see a lot of good reasons for using a QTC of 0.707. I don't exactly know why that became dogma.

I generally use undersized enclosures because it raises the output, increases the power handling, takes up less space. Sure, you lose some low frequency extension, but I have no need for a midbass to play 60hz, that's what subwoofers are for.


----------



## tonny (Dec 4, 2010)

Patrick Bateman said:


> Back in the day, he did an interesting 'trick' with these Infinity PFRs. He basically put the midbasses in a ported enclosure that's way too small. This raises the F3 quite a bit, but also creates a big ol' peak in the midbass. In the measurement above, the midbass has a 6dB peak at 160Hz.
> 
> By doing this, it raised the output by about 6dB in the midbass. This would be equivalent to using four midbasses instead of one.
> 
> ...


And by taking smaller enclosures you get more stored energy so a loss in the SQ... And with ported boxes more phase problems to connect the drivers to the rest off the drivers! And that just don't sound right for midranges and for midbasses to my opinion at least!


----------



## Patrick Bateman (Sep 11, 2006)

tonny said:


> And by taking smaller enclosures you get more stored energy so a loss in the SQ...


Citation please.



tonny said:


> And with ported boxes more phase problems to connect the drivers to the rest off the drivers! And that just don't sound right for midranges and for midbasses to my opinion at least!


People avoid ported midbasses because they expect there's going to be a phase problem: a ported box has 180 degrees of phase rotation.

Yet a 2nd order filter *also* has 180 degrees of phase rotation, and a 4th order has 360 degrees!

I definitely think phase is something that needs to be considered, but I'm far more concerned about phase shift in the midrange than phase shift at 150Hz.

I've generally found that the problems with ported boxes are caused by frequency response, not phase response.


----------



## Bayboy (Dec 29, 2010)

A midbass that plays flat all the way down to its bottom roll-off or crossover point might sound ideal in thought and on paper, but a quick look at most liked curves shows there should be a rise towards the bottom leading to the sub and the sub continues that further rise. Playing "flat" usually winds up in deep cuts in the 200hz area and above. Been there.. don't care for it. Looking at the graphs of some popular and successful drivers often shows at least a gentle rise starting in that area.

But that's getting off topic. The original posting was about actual midrange, not midbass. A higher Q enclosure isn't going to be that detrimental unless creating an unruly peak because most are crossed well above that point to begin with. Many enclose mids in the pillars without much of a con, but without forming a case by case basis, debating about which route is better becomes more like textbook recital chest thumping. 

Sent from my SM-G955U using Tapatalk


----------

