# Midranges and Midbasses in Sub-Optimum Boxes



## Patrick Bateman (Sep 11, 2006)

I had someone email me about an offhand comment I made in another thread, so here's some elaboration on that. If anyone out there is obsessing over WinISD, here are some thoughts on midranges and midbasses in sub-optimum boxes.
















In one of my cars I had the B&C 8NDL51 in an enclosure that's just barely big enough to contain the basket, and in another setup I had a JBL 400GTI in an enclosure that's small enough to fit in my palm.

If you model these in WinISD, they look like sh t. There's a big bump in the upper midbass.

There's some simple reasons why this doesn't sound like sh t in the car, along with a more complex reason.

First, the simple reasons why this works:


Putting a woofer in a box that's too small raises the F3 to 150, or even 200hz. But that's *anechoic.* In a car, cabin gain buys you another octave of response, sometimes even more.
Theoretically, a sealed box with a QTC of 0.7 has the best transient response. If I'm not mistaken, that theory is based on *frequency response*. IE, it has *nothing* to do with box size. The transient response is good because the response is flat, not because of any magical feature of a QTC of 0.7.
If you put a woofer in the car with a QTC of 0.7, the response goes to hell, because cabin gain exaggerates the low end. *In other words, the optimum sealed box is only optimum if it's measured outside. In the car, it's boomy.*
Putting your speakers in your doors is dopey. Your doors are filled with leaks. If you want your doors to play down to even FIFTY hertz, you need a baffle that's SIXTY EIGHT inches across. *With no leaks anywhere.* Even the smallest leak will wreck your low frequency response, and *doors are leaky.* If you insist on putting woofers in your doors, put them in an enclosure, and *put the enclosure in the door.*
A small sealed box reduces excursion on your woofers. It must be airtight. For instance, I was doing some distortion testing on the B&C woofers pictured above, and fed them with enough power that you could hear them from HALF A MILE AWAY. Seriously, it's kind of amazing how much power a woofer can handle in a proper enclosure, and a car door *is not a proper enclosure.* If you guys are disappointed in how much power your midbasses can handle, or you keep blowing woofers, consider putting them in a proper enclosure.

Last but not least, there's a complex reason why I like very small boxes. When a woofer is located near a reflector, it creates a notch at one-quarter wavelength. The reflector could be anything - the floor, the firewall, the windshield, etc... For instance, if you put a woofer in your door and the floor is seven inches away, you'll get a measurable notch at 482hz. _(13500inches per second / 482hz / 4) = 7"._

Because of this, a woofer in a small sealed box opens up some locations that wouldn't be practical otherwise. For instance, I could have hacked up my doors to fit that 8" woofer, but by putting it in a very small sealed box, I could mount it against the firewall, and enjoy higher power handling and higher efficiency in the midbass frequencies.

To make a long story short:

Don't obsess over QTC. The advice you'll find in loudspeaker textbooks is based on anechoic measurements, and in the car, reflections and cabin gain change *everything*.
I see guys putting re-donkulous woofers in their doors, when it's often possible to get a MUCH lower F3 using a smaller woofer _in a proper enclosure_
A very small sealed box will often play lower and deeper than a large woofer in a leaky enclosure like a door.
Any leaky enclosure "unloads" at a certain frequency. Whether it's a vented box, a door, or an open baffle. They *all* unload. If you have a lot of power on tap, and a woofer that's built to handle it, a small sealed box is very attractive. If you *don't* have a lot of power on tap, or are thermally limited, I have some solutions to that too  But that's another thread named "Space: The Final Frontier."


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## Mless5 (Aug 21, 2006)

Patrick Bateman said:


> "Space: The Final Frontier."
> [/list]


 open all ears


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## gitmobass (Nov 7, 2009)

This thread is very interesting, makes me glad I'm making actual pods in my doors


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## lycan (Dec 20, 2009)

a few comments :

- Qtc=0.707 is often considered ideal, for two reasons : the frequency response is "maximally flat", and this alignment also gives you the _lowest_ -3dB frequency (therefore, the widest power bandwidth) for a sealed enclosure. Turns out the transient response is also _not bad_ ... but this value of Qtc is _not_ chosen for optimal transient response. Optimal transient response is often associated with Qtc=0.5

- small leaks do _not_ materially effect the response of a driver in a sealed enclosure. It's pretty easy to model 

- an enclosure that's "too small" does improve power handling, no question. But the "hump" in the frequency response (and resultant transient overshoot & ringing) may ... or may NOT ... be "improved" by cabin gain.


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## Patrick Bateman (Sep 11, 2006)

lycan said:


> a few comments :
> 
> - Qtc=0.707 is often considered ideal, for two reasons : the frequency response is "maximally flat", and this alignment also gives you the _lowest_ -3dB frequency (therefore, the widest power bandwidth) for a sealed enclosure. Turns out the transient response is also _not bad_ ... but this value of Qtc is _not_ chosen for optimal transient response. Optimal transient response is often associated with Qtc=0.5
> 
> ...



If I'm not mistaken, the transient response is related to the frequency response, not the QTC. I'm not 100% sure on that, and I'm too lazy to research it.

In other words, a sealed box with a Q of 0.5 will have superior transient response than the same woofer in a sealed box with a Q of 1.0 but *only if it's measured anechoically.*

By this logic, we should be focused on the power response of the loudspeaker in the room/car, not the predicted frequency response.

If that makes sense, then the goals of the enclosure change. Instead of aiming for flat frequency response in WinISD, you're aiming for flat frequency response in the car. And there are a few ways to approach that.


Put a large woofer in a small sealed box. Your F3 will be higher than in a larger box, but your power handling will go up too. Then let cabin gain augment the low end. If cabin gain isn't sufficient, use EQ. (It's easier to EQ a small sealed box than a large box, because distortion rises with excursion, and a small sealed box has lower excursion.)
*OR* use a larger box, and use EQ to *reduce* the low end. Same destination as above, just going about it a different way. Instead of boosting the low end via cabin gain and EQ, we're cutting it via EQ. The large box will have higher excursion, but it won't need as much power to get to the same F3.
*OR*Meet me halfway. Use a smaller woofer than you normally would, but one with extraordinarily high power handling. While the small woofer will need more power than the large woofer to get to the same target, if you can control excursion and distortion, you will be only limited by power handling. 

I'm certain some people are scratching their heads when they see me using a mix of sturdy prosound drivers, along with fragile and cheap computer speakers. The reason for this is EBP. (Efficiency Bandwidth Product.) Most car audio midbasses have an EBP that sacrifices efficiency for extension. Computer speakers typically have an EBP that's in the same range as a prosound driver. You wouldn't want to use just one - it would go "pop." But an array of them counters their low power handling.

Just some thoughts. I've tried all three, each has it's advantages.


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## lycan (Dec 20, 2009)

Patrick Bateman said:


> If I'm not mistaken, the transient response is related to the frequency response, not the QTC. I'm not 100% sure on that, and I'm too lazy to research it.
> 
> In other words, a sealed box with a Q of 0.5 will have superior transient response than the same woofer in a sealed box with a Q of 1.0 but *only if it's measured anechoically.*
> 
> ...


A second-order system, like a driver in a sealed box, is completely defined by two parameters : Qtc, and Fc. And actually, Fc is nothing but a scaling factor. So Qtc completely defines the frequency response "shape" (except for the scaling provided by Fc), and therefore also completely defines the transient response overshoot & ringing. Frequency response & transient response are inseparable ... tell me one, and i'll tell you the other  And Qtc defines them both (except for scaling), for a second-order system.

I do agree that cabin gain will change things, compared to anechoic. But cabin gain really "starts" at maybe 80Hz, extending downward, at about 12dB per octave as frequency decreases. So it's going to have very little impact on midbass, and almost none on midrange ... in either time or frequency domains.

Reflections are an issue, sure. But if you _start_ with an enclosure that gives a rather bad transient response anechoic (resulting from a Qtc that's too high, for example) ... it's hard to imagine that reflections are going to _help_


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## Patrick Bateman (Sep 11, 2006)

lycan said:


> I do agree that cabin gain will change things, compared to anechoic. But cabin gain really "starts" at maybe 80Hz, extending downward, at about 12dB per octave as frequency decreases. So it's going to have very little impact on midbass, and almost none on midrange ... in either time or frequency domains.
> 
> Reflections are an issue, sure. But if you _start_ with an enclosure that gives a rather bad transient response anechoic (resulting from a Qtc that's too high, for example) ... it's hard to imagine that reflections are going to _help_


In my measurements, I've found that cabin gain actually begins about an octave earlier - around 150hz. I was going to try and mathematically prove my point, but I got lost at The Sabine Equation.

If anyone is brave enough to do the math, you need to figure out the Schroeder Frequency of your car, and to do that, you need to solve the Sabine Equation first. Have fun!

Reverberation - Wikipedia, the free encyclopedia

Room Acoustics

Schroeder frequency










Here's Wehmeyer's measurement of various cars, from JBL. In the graph, you'll clearly notice cabin gain kicking in at 80hz. But if you go an octave higher, you'll also notice a "plateau" in the response, from 80 to 160hz. From 160 hz and up, the response curve is about 6-10db lower.

I've noticed this in my own measurements - a midbass that measures flat on my driveway (as close to anechoic as I can get) "sees" some gain from 160hz and down.

My "hunch" is that this is due to the dimensions of the car. The cabin of my car is 107" long, and 56" tall. When sound hits a reflector it creates a dip if it's out of phase, and a peak if it's in-phase. So when the speaker emits a wavelength that's 428" long we get a dip due to the reflected energy from the rear windshield, and the same applies from the side door when the frequency is 224" long. (To make this even more maddening, it's dependent on where the mic is located!!!)

Here's a table that lists the peaks and the dips, based on the dimensions of my car, and assuming the woofers are pushed right up against the firewall.


At 107", you get a dip at 32 hz and a peak at 64 hz.
At 56", you get a dip at 60 hz and a peak at 120 hz.

Looking at Andy's graphs, we see a modest dip at 35hz, and a pronounced dip at 70hz. The equation predicts a dip at 32, and both a peak *and* and a dip around 60hz. I believe the discrepancy is because the doors are closer than the rear windshield, therefore they reflect energy more efficiently.

Anyways, this is way too much typing for such a gorgeous day! The bottom line is that I see augmentation in the bass from 80-160hz. Is it cabin gain? I'm not 110% sure. But it's there.


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## wiseman454 (Nov 30, 2009)

Thanks.


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## lycan (Dec 20, 2009)

Patrick, the 80Hz number I tossed out was just a "rule-of-thumb" average, based on a variety of interior dimensions. So, no real disagreement on your data! 

I just want to caution against something that's all too pervasive in our hobby, and that's the notion that somehow all the math & theories "go out the window" in the car environment. We've all heard comments like : "That might be fine in a lab, or an anechoic chamber ... but none of it applies in a car!" 

The TRUTH is ... the engineering ANALYSIS is ... that the car environment simply adds another transfer function, or EQ, in the signal processing chain. It certainly can't be ignored, but neither does it "negate" any acoustic theories or models.

Case in point : put a midrange driver in a _very_ small enclosure, such that the resultant Qtc is >> 1. Measured in an anechoic chamber, absent of reflections, and you'll see a transient response with a significant overshoot and ringing (the manifestation in the frequency domain will be a significant "hump" in the high-pass frequency response). What happens when you put this little enclosure in a car? Is the anechoic response "negated", or just "modified" by another transfer function in cascade? Of course, the answer is the latter. I like to model reflections with first-order image theory ... place "virtual" image drivers where you "see" reflections (outside the car), then remove the reflective boundaries. So the car interior, in this case, can be modeled as a 3-D _array_ of midrange drivers, each operating in enclosures that are too small, with no reflective boundaries anywhere in sight. Does the anechoic response still "matter"? Sure it does! We've only complicated the anechoic response by building a 3-D array of identical drivers .... doesn't mean the anechoic no longer "matters", we've just added another layer ON TOP : namely, the acoustic response of a small, reflective environment.

Armed with this line of reasoning, it would be the rare coincidence indeed that anechoic overshoot & ringing would actually be _helped_ by arraying a multitude of identical drivers (as a model of the vehicle's interior).

So my real point is this : First, model the driver in a chosen enclosure in an anechoic chamber, absent cabin gain or reflections. Then, _add_ the car's transfer function (cabin gain in the bass, reflections in the midrange, etc.) to the anechoic response, to determine how the driver-plus-enclosure will behave in its intended environment. BOTH steps are essential  and _no_ environment is beyond the scrutiny of acoustic analysis.


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## cvjoint (Mar 10, 2006)

Yikes, those small enclosures surely make me cringe. I've used no less than 3 eight inch mids in the car in a rather small sealed enclosure with disastrous results. The gain that results from a small box is to be avoided at all costs, it is not in fact musical nor does the car environment provide any sort of remedy for it. 

In my situation the original driver Seas W22 crossed 200hz and up had major ringing and overshoot as mentioned by lycan. I was looking at 9db gain starting at 250hz and going down way past my xover point. Initially I thought it was enclosure flex. I tried any sort of patch work that I could find:
-dynamat on the interior of the box
-some 3lb of clay per box
-various deflex pads
-changed the mid for B&C, and Scan Speak 21

In the end the only thing that worked was buying a mid that did not require lots of airspace. The 15M sounded like a winner after that. 

You can EQ that out to have a flat FR but that does nothing to approach the real problem. This is a way to common with kick panels and it's very noticeable. Your argument may hold for too large of a box. In that case EQ. will surely work to flatten the FR and there will be no box gain artifact. With a very low Q EQ. CUTS may be needed. This is the best of situations as you don't want to EQ. boost the FR too much. In fact very many good tuners only do cuts. It's not worth reaching the dynamic limits of your gear. I would also not rely on EQ. to make anything work to begin with. You want to start with as good of a setup as you can without needing band aids from the get co. The car environment is bad as it is. 

As previously mentioned door leaks are not big of a problem as you may think. I've seen several techniques that can solve the leak problem, nor are these impacting response that much. I've had no problem getting my door midbasses to play flat to 30hz.


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## Patrick Bateman (Sep 11, 2006)

cvjoint said:


> Yikes, those small enclosures surely make me cringe. I've used no less than 3 eight inch mids in the car in a rather small sealed enclosure with disastrous results. The gain that results from a small box is to be avoided at all costs, it is not in fact musical nor does the car environment provide any sort of remedy for it.
> 
> In my situation the original driver Seas W22 crossed 200hz and up had major ringing and overshoot as mentioned by lycan. I was looking at 9db gain starting at 250hz and going down way past my xover point. Initially I thought it was enclosure flex. I tried any sort of patch work that I could find:
> -dynamat on the interior of the box
> ...


I probably should have mentioned that using an uber-small enclosure doesn't work so hot if the QTS of your driver is high, the VAS is high or both :O








Here's the simulated response of your W22 versus my 8NDL51 in a very small sealed box. (one tenth of a cubic foot, basically big enough to contain the woofer and no more.)

With the prosound drivers that I tend to use, the woofer has less than 1db of peaking. With the Seas, which has a much higher VAS, we see close to 6dB of peaking at 150hz 


You can see this in the sims above. The orange line is a 2.8liter sealed box. The enclosure with the massive peak is the Seas W22.


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## cvjoint (Mar 10, 2006)

you are right in that the Seas was a lot nastier but that only reinforces the argument for building the proper enclosure. My kick is 7 liters, when you model it it doesn't look so bad. I even thought the resonance wasn't there for a while but some experienced tuners picked it up fast. I started playing with proper sized boxes and the difference was night and day. IMO stay away from ANY kink behavior, it's a prerequisite for good sound.


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## T3mpest (Dec 25, 2005)

What about a ported midbass in a car? Could this be be done in a kickpanel with decent results, assuming you know where your major peaks in midbass are in the vehicle and tune around them? The midbasses I'm getting ready to install is a set of BMS 8n515's and they need very small enclosures, even ported. To the tune of <.2cubes net. The only issue i can see is that getting the port to the outside of the kick would be hard. If I build the kick to run across my floor I can easily put the port toward the center of each floor near the firewall, (I got room behind and in between the pedals) but i don't know if that would drag my stage inwards.


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## GibTG (Mar 11, 2010)

Sorry this question isn't related to the meat of the argument, but the original post made me think about it...

What about if your door speakers are only playing down to 150 Hz? How significant are leaks then?


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## Patrick Bateman (Sep 11, 2006)

T3mpest said:


> What about a ported midbass in a car? Could this be be done in a kickpanel with decent results, assuming you know where your major peaks in midbass are in the vehicle and tune around them? The midbasses I'm getting ready to install is a set of BMS 8n515's and they need very small enclosures, even ported. To the tune of <.2cubes net. The only issue i can see is that getting the port to the outside of the kick would be hard. If I build the kick to run across my floor I can easily put the port toward the center of each floor near the firewall, (I got room behind and in between the pedals) but i don't know if that would drag my stage inwards.


I really like the idea of using a ported midbass in a car, provided you can measure the impedance curve. Personally I'm using a WT3, and it's such a useful tool, I've actually bought it twice. You can't easily rely on the predicted port length because there are a lot of variables that will affect the tuning frequency. (It's not easy to predict what the volume of a kick panel is, and the smallest leak will wreck the helmholtz resonance. The location of the port's exit can make it "seem" longer than it really is also.)

I'd actually argue that porting a midbass makes more sense than porting a sub, since the range from 80-160hz is one of the most difficult to produce with authority. And if you can't produce 80hz with authority, the transition to your sub will be problematic.


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## 94VG30DE (Nov 28, 2007)

< has ported midbasses in his car  

No time to dig into this thread here at work, but what I've seen so far I'm liking, and it's encouraging me to do what I have been thinking about for a few weeks now: I think I'm going to try multiple drivers in a ported box that is 'too small'. Once I get time in a few weeks, we will see how it goes. I'm going to try to take measurements before and after.


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## Hernan (Jul 9, 2006)

I'm doing kickpanels for my midbasses and midranges. The first prototype works AWESOME! I just take a spare Seas CA18rnx that I have hanging around and It sounds as good or better than my home towers:



Measured at home with sweep HP80, LP 600.
Orange: Vifa 7 woofer at an AudioPro tower.
Blue: Seas 7 woofer at a fiberglass kickpanel.
The lines below show 3er HD.

At the car the driver sounds very very good. I always hate this driver playing at the door. Now I'm thinking on getting one more...


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## Hernan (Jul 9, 2006)

I have another comment to add.

I have two rear satelites, drivers are Auras NS3 and the enclosures are very small (plastic glasses deadnead with lots of NHMC=HEAVY).
They take insane amounts of power, I run them in series from a bridged channel, [email protected] aprox. (they were abuse so many times in 3 years that I can't believe that they are still working like new.)


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## BowDown (Sep 24, 2009)

I'm curoius.. how would my TB 5.25" Sub work in a small sealed? How small would you suggest going to try this out?

Specifications: Power Handling: 40 watts RMS/80 watts max *VCdia: 1-1/4" *Impedance: 4 ohms *Re: 3.6 ohms *Frequency range: 45-1,500 Hz *Fs: 45 Hz *SPL: 82 dB 2.83V/1m *Vas: 0.24 cu.ft. *Qms: 2.68 *Qes: 0.61 *Qts: 0.49 *Xmax 9.25 mm *Dimensions: Overall diameter 6-1/8", Cutout diameter 4-3/4", Depth 3-1/8".


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## 94VG30DE (Nov 28, 2007)

BowDown said:


> I'm curoius.. how would my TB 5.25" Sub work in a small sealed? How small would you suggest going to try this out?
> 
> Specifications: Power Handling: 40 watts RMS/80 watts max *VCdia: 1-1/4" *Impedance: 4 ohms *Re: 3.6 ohms *Frequency range: 45-1,500 Hz *Fs: 45 Hz *SPL: 82 dB 2.83V/1m *Vas: 0.24 cu.ft. *Qms: 2.68 *Qes: 0.61 *Qts: 0.49 *Xmax 9.25 mm *Dimensions: Overall diameter 6-1/8", Cutout diameter 4-3/4", Depth 3-1/8".


is that this: Tang Band W5-1138SM 5-1/4" Neodymium Subwoofer | subwoofer 5-1/4" subwoofer neodynium subwoofer tangband tb speakers tangband-22008 | Parts-Express.com 

If so, excellent question. I was thinking of putting one of those in about 0.06 cubic feet


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## BowDown (Sep 24, 2009)

94VG30DE said:


> is that this: Tang Band W5-1138SM 5-1/4" Neodymium Subwoofer | subwoofer 5-1/4" subwoofer neodynium subwoofer tangband tb speakers tangband-22008 | Parts-Express.com
> 
> If so, excellent question. I was thinking of putting one of those in about 0.06 cubic feet


That's the one. They sound great in my car doors w/sound deadening & speaker tweaker pads. I did a little EQ'ing on them to fill in some dips around 300-400hz.. but overall very happy with them in their current state.


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## wiseman454 (Nov 30, 2009)

Has anyone ever tried a line array midrange set-up?. I just saw a thread on this TB driver TB W2-803SM. You could get four on each side in a vertical array in the kicks or the pillars depending on your ride. The efficiency and power handling seems right on with 4 per side. 
I modelled a tiny ported enclosure just for fun. It came out to only .039 cf !!! The f3 was 159hz.
The port was tiny and short and a basically was a box of only 3x3x10 inches outside dimensions. Any thoughts


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## chithead (Mar 19, 2008)

This fascinates me greatly... 

Although the qts is rather high for the Rainbow Germanium components I am using (0.81) . . . according to WinISD, a 3.295 liter enclosure is 6db higher at 150hz than when run IB, but starts to fall off right at 100hz. A 5.56 liter enclosure would only be 4db higher at 150hz, but stays higher than IB down to 75hz. 

Looks like its time to break out the sonotubes for some experimentation.


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## katodevin (Feb 14, 2008)

Very very interesting. If I'm not mistaken, if I am following you correctly Patrick, these exodus anarchys would be a prime candidate.

Super high power handling and high excursion. Modeled them up in a 2 liter enclosure, and it seems like they have ~ a 1.6db "spike" at 150hz. Not bad at all. Am I following you correctly? 

* Fs = 45.8HZ
* Qes = 0.48
* Qms = 6.37
* Qts = 0.44
* Vas = 9.61L
* Sd = 131cm^2
* Xmax = 12.5 mm one-way
* Re = 6.4 Ohms
* Le = 0.84 mH
* BL = 10.79 N/A


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## spmpdr (Nov 5, 2009)

BowDown said:


> That's the one. They sound great in my car doors w/sound deadening & speaker tweaker pads. I did a little EQ'ing on them to fill in some dips around 300-400hz.. but overall very happy with them in their current state.


Do you run those TB's IB all the way up to 400-hz?Ive always wanted to get a set to try as mid bass but have hesitated because of them being a subwoofer.Do they sound good playing up that high?


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## BowDown (Sep 24, 2009)

spmpdr said:


> Do you run those TB's IB all the way up to 400-hz?Ive always wanted to get a set to try as mid bass but have hesitated because of them being a subwoofer.Do they sound good playing up that high?


Ya I take them from 63hz to 500hz @ 18db. They sound great. I had to EQ up some of the 400-500hz range to correct a drop in my RTA reading, but outside of that they are very good speakers for that range.


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## spmpdr (Nov 5, 2009)

BowDown said:


> Ya I take them from 63hz to 500hz @ 18db. They sound great. I had to EQ up some of the 400-500hz range to correct a drop in my RTA reading, but outside of that they are very good speakers for that range.


Nice man thanks for the info ,i might have to try a pair!!


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## katodevin (Feb 14, 2008)

So I gave this a shot with a pair of exodus anarchys in small boxes (2 liters each).

Yes, they did get much more punchy, but they got really boomy. I dropped down my eq ~ 150hz to try and help, but wasn't able to tune it out with any reasonable amount of eq'ing.

Patrick, do you have any other suggestions on tuning for this? I like the snappiness, but they sounded really artificial otherwise.

Thanks.


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## Oliver (Jun 25, 2007)

Patrick Bateman said:


> *A very small sealed box will often play lower and deeper than a large woofer in a leaky enclosure like a door.*
> 
> [/list]


*complete and utter, BS !*

*Umm ... no, not EVER ^^^*

Try mounting your speakers in an infinite baffle configuration or an aperiodic enclosure---these will play lower with more authority in the lowest ranges of the speakers ability.

A small box will lift the whole range of frequencies a driver can play [ NO LOWS ]

Cabin gain for several subwoofers >>>


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## 14642 (May 19, 2008)

One thing has to be made perfectly clear here and that is that cabin gain does NOT affect the behavior of the driver materially. It's easiest to think of it as fixed EQ that requires no additional excursion or power. 

Lycan is right. Qtc does define transient response for a woofer in a sealed box in an anechoic environment (minimum phase system). For a woofer in a sealed box in a car, it still defines the transient response of the speaker and enclosure, but it no longer defines the response of the entire system, because it's no longer minimum phase. In a car there are many radiators (vibrating panels) and many reflections. 

The driver Qts and system Qtc (and all Thiele and Small parameters) only define the behavior of the system at and slightly above rolloff. They have nothing to do with midband response shape. Snappy, punchy midbass depends on flat response between 1k and 4k. If you don't believe me, listen to your favorite midbass track on a pair of headphones through a 100Hz low pass filter. Then try 200 Hz. There's no snap or punch down there. 

Finally, if you really want your midbass drivers to handle lots of power, use an electronic high pass filter. Tiny sealed boxes eliminate low frequency response, since they minimize excursion; degraade transient response (the audibility of this is questionable, especially once you've EQed). They do REQUIRE more power at low frequencies.

So, is handling more power the objective or is making more sound the objective?


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## Oliver (Jun 25, 2007)

Andy Wehmeyer said:


> *Tiny sealed boxes eliminate low frequency response*, since they minimize excursion; degraade transient response (the audibility of this is questionable, especially once you've EQed). They do REQUIRE more power at low frequencies.
> 
> So, is handling more power the objective or is making more sound the objective?


*Thanks Andy !*


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## jbowers (May 3, 2009)

Andy Wehmeyer said:


> Snappy, punchy midbass depends on flat response between 1k and 4k.


That information may be one of the most significant bits of knowledge I've gotten from this place.


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## katodevin (Feb 14, 2008)

Andy Wehmeyer said:


> Tiny sealed boxes eliminate low frequency response, since they minimize excursion; degraade transient response (the audibility of this is questionable, especially once you've EQed). They do REQUIRE more power at low frequencies.
> 
> So, is handling more power the objective or is making more sound the objective?


Hi Andy,

Thank you for the clarity. I guess this is one of the cases where "if something sounds too good to be true..."

I was mainly looking for more "snap" out of my midbasses in a 3-way setup. I suppose that making the sealed box so tiny, it may have shifted the freq response of my mids towards your quoted 1k-4k necessary for "snap". I'll continue experimenting with NOT tiny boxes, with a focus on that freq range.

Appreciate the feedback all.


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## dch828 (Jun 6, 2010)

Andy Wehmeyer said:


> Snappy, punchy midbass depends on flat response between 1k and 4k.


That's right about where a snare drum sits. There is some crispness around 2-5k and of course some bass information down lower.


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## 14642 (May 19, 2008)

dch828 said:


> That's right about where a snare drum sits. There is some crispness around 2-5k and of course some bass information down lower.


Right. You can't remove your midbass drivers, but adding bigger ones with more power won't get you the snap. This is why this whole arguement about beaming and off-axis response vs. on axis response is so important. Since we hear the power response in a car, it's important that this frequency range, which is where the tweter meets the mid, is contained in the on- and off-axis response. You can only get that if you use your drivers within their piston range, apply some directivity correction to the bottom of the tweeter (waveguide), cross the tweeter low or you use a 3-way.

The best track I've ever found for getting this right is the theme from Seinfeld.


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## 94VG30DE (Nov 28, 2007)

Andy Wehmeyer said:


> The best track I've ever found for getting this right is the theme from Seinfeld.


I don't know why I didn't think of that sooner, but you are definitely right. That punchy bass is difficult to find in most modern music, so it's tough to find source material that makes it easy to pick out those types of problems. The Seinfeld theme nails it. Thanks for that


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## Hernan (Jul 9, 2006)

I went from door to kicks with both midbasses and midranges.
Some things are better but others worst.
Kicks are more solid and rattles are gone.
The problems are, frecuency response is peaky, low end extention is lost.
The car is small and the enclosures have around 6-7 liters.

Is there any way to lower the QTC of the kicks. Venting inside the frame or outside are not an option. 
Venting or using aperiodic membranes?

Drivers are Mpyres 6,5.

Thanks!


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## ErinH (Feb 14, 2007)

stuff the crap out of the enclosure with polyfill will decrease qts.

I've managed to take my kicks from 0.5 all the way down to 0.25 qts by adding a friggin' ton of polyfill. It wasn't 'loose'... it was stuffed to the max, almost as if I were putting something of significant volume to lessen the airspace. Or, on the flip side, you can simply take something of volume and put it inside the kicks (ie: some people will use bricks to put inside an enclosure when trying to find the proper enclosure size needed).

I am curious, however, why you would want to lessen qts. Do you know the qts of the speakers _in the enclosure_ or are you just guessing? In my case, I needed to raise qts and once I did, things were better. Lost it at the cost of efficiency but no big deal because I had extra power on tap that I wasn't using.


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## Hernan (Jul 9, 2006)

bikinpunk said:


> stuff the crap out of the enclosure with polyfill will decrease qts.
> 
> I've managed to take my kicks from 0.5 all the way down to 0.25 qts by adding a friggin' ton of polyfill. It wasn't 'loose'... it was stuffed to the max, almost as if I were putting something of significant volume to lessen the airspace. Or, on the flip side, you can simply take something of volume and put it inside the kicks (ie: some people will use bricks to put inside an enclosure when trying to find the proper enclosure size needed).
> 
> I am curious, however, why you would want to lessen qts. Do you know the qts of the speakers _in the enclosure_ or are you just guessing? In my case, I needed to raise qts and once I did, things were better. Lost it at the cost of efficiency but no big deal because I had extra power on tap that I wasn't using.


The enclosures has polyfill but not that much.

I want to lower the QTC of the system to flatten the response. 
I'm not guessing, It sounds peaky, asking for more air.
It sounds like a too small sealed box.


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## ErinH (Feb 14, 2007)

without going ap, I really don't know how you're going to give the enclosure more air. 
Maybe try to build the baffle out to give the driver more space? 

My above reply was based on AP, and I didn't catch that you didn't have an ap enclosure. I was just thinking you did. So, the above probably wouldn't work for you as it had me.


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## Hernan (Jul 9, 2006)

bikinpunk said:


> without going ap, I really don't know how you're going to give the enclosure more air.
> Maybe try to build the baffle out to give the driver more space?
> 
> My above reply was based on AP, and I didn't catch that you didn't have an ap enclosure. I was just thinking you did. So, the above probably wouldn't work for you as it had me.


Where are you venting, outside the vehicle, frame or just carpet?


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