# SQ sub & high xmax



## manowar_gub (Dec 18, 2012)

Hi!

Is I understand right that there can be high sensitive subs with xmax ~14mm? Searching for sub for playing flat-line from 30 hz @ 500 rms (ported of course) and find only heavyweight transmission like DD, SA...


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## qwertydude (Dec 22, 2008)

I would say the best sounding sub for SQ and efficiency, definitely the Image Dynamics IDQ line. 17mm Xmax and a healthy efficiency. SQ is very good too.

But my personal favorite is definitely my JBL P1224. 14mm Xmax and pretty efficient, maybe not as efficient as the ID and IDQ subs but it makes up for it with even better midrange response and ability to play very deep, 30 hz in a ported enclosure no problem.


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## SkizeR (Apr 19, 2011)

Fi Q

almost 3 cm of xmax. plays nice and clean. and can get loud and play low. i love mine.


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## fish (Jun 30, 2007)

I thought the ID Max had 23-24mm Xmax?

The JBL GTi series has around 20mm I believe.


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## manowar_gub (Dec 18, 2012)

Thanx, what's about Gladen SQX12 ?

p.s. mailing to Rus JBL distrib about p1224 - the answer was "JBL have stopped produce them"...


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## ou812 (Oct 25, 2008)

TC Sounds Epic 12" DVC Subwoofer 293-650


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## manowar_gub (Dec 18, 2012)

nice, is it correct to compare *TC Sounds Epic 12* and *Dayton Audio TIT320C-4 Titanic MkIII* ?


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## nellymerc (May 3, 2012)

I'm jumping into a convo that's way out of my league but that's how you learn I guess. What is considered high sensitivity and did you want the xmax higher or lower? My JBL sub sounds great to me. Punchy and loud. It's not just floppy bass it hits nice. Sensitivity 87db xmax 6mm


Sent from my iPad using Tapatalk


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## manowar_gub (Dec 18, 2012)

xmax ~14mm in priority, high sens is other target. my last driver vas dragster 126 high sens + xmax ~8mm, - of course it plays loud from 30hz but only from 200rms max, when I bring him 500rms it vas VC knock and high THD... that's why after modelling in JBL speakershop I understood it should be that driver I am looking for!


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## subwoofery (Nov 9, 2008)

high sensitivity subwoofer = bigger enclosure compared to a low efficiency one 

Kelvin


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## manowar_gub (Dec 18, 2012)

subwoofery said:


> high sensitivity subwoofer = bigger enclosure compared to a low efficiency one
> 
> Kelvin


agree! but it can be sub with *xmax 15mm + 83 db/1w/1m SPL* and *xmax 15mm + 86 db/1w/1m SPL*, last one will be louder twice, that's my idea for searching sub...

please write brands (or sites) that may be useful to me - just know only JBL, Dayton, Re Audio, TC Sounds...


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## manowar_gub (Dec 18, 2012)

ok, let's discard the SPL, is there subs with high xmax and mms <220g ? for example RE SRX 12D4 has 18mm - is it true? I think 18mm it is peak to peak, so real xmax is 8-9mm, isn't it?


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## Oscar (Jun 20, 2010)

manowar_gub said:


> agree! but it can be sub with *xmax 15mm + 83 db/1w/1m SPL* and *xmax 15mm + 86 db/1w/1m SPL*, last one will be louder twice, that's my idea for searching sub...
> 
> please write brands (or sites) that may be useful to me - just know only JBL, Dayton, Re Audio, TC Sounds...


sorry doesn't work like that. Sensitivity ratings are for mid-band response, and usually don't tell you much about the low-end.

There is no magic going on inside a speaker that can make it more efficient by 3dB and not suffer anywhere else in it's performance. It's all about compromise. To get that extra 3 dB, something has to give---Hoffmans Iron Law.

Like subwoofery said, to fully and truly utilize those extra 3 dB of mid-band sensitivity, it will normally require a larger cabinet. All of this was set in stone way back when Thiele-Small were developing their view of low-frequency loudspeakers and has been known for decades already.


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## manowar_gub (Dec 18, 2012)

2 *Oscar*
ok, searching subs, what's Thiele-Small u are looking for?


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## Oscar (Jun 20, 2010)

manowar_gub said:


> 2 *Oscar*
> ok, searching subs, what's Thiele-Small u are looking for?


if I had my preference I like low Qts (low 0.30s), medium Fs (mid 30s). Vas depends entirely on woofer size.

There are always exceptions though. My JBL W10GTs have Qts in the 0.60 range, yet they sound awesome ported.


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## darrenforeal (Jan 14, 2011)

I might as well chime in because I have a question. How high can the IDQv3. 12inch play effectively and well? 100hz?

I know some subs are better on the high end of freq but I can't find much on the IDQ12. Also, what size sealed enclosure would be ideal for the IDQ12 in playing 20hz to 100hz?


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## subwoofery (Nov 9, 2008)

manowar_gub said:


> ok, let's discard the SPL, is there subs with high xmax and mms <220g ? for example RE SRX 12D4 has 18mm - is it true? I think 18mm it is peak to peak, so real xmax is 8-9mm, isn't it?


There's a few subs with a relatively low Mms and high Xmax (>15mm) 
IDmax 
Arc Flatlyne 
Boston G5 
JBL W12Gti 

I'm sure there's a few others but Mms shouldn't be the only spec you need to look for... 

Kelvin


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## manowar_gub (Dec 18, 2012)

thank, try to searching its TC, only 1 question: can SPL graphics of JBL in car be like this sheet? i think it depends not only sedan/hatch/unver type of car, but and place/direction of driver and place/direction of microphone, isn't it?


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## Bayboy (Dec 29, 2010)

High xmax numbers are good for sealed boxes, but when it comes to ported it creates a problem somewhat by requiring very long or labyrinth ports to keep vent velocity to a minimum tolerance. I would not focus so hard on xmax numbers unless you are willing to deal with the consequences in a ported box.


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## Oliver (Jun 25, 2007)

http://www.diymobileaudio.com/forum...er-specs/122971-sundown-sa-8-v-2-klippel.html

You can't go wrong with this guys stuff, lots of videos on youtube.

Sundownz


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## Ricci (Sep 30, 2008)

If you want to identify which raw sub drivers have higher actual efficiency which has more to do with conversion of electrical power into output and a lighter load on the amplifier (Not sensitivity which as previously mentioned is measured up outside of the range a typical sub is operated to begin with and does not tell you anything about the load presented to the amp.) you need to look at Bl^2/RE and compare similar SD. Inductance effects and an impedance curve. Unfortunately the last two are rarely provided by MFG's. the impedance curve in combination with other specifications, provides absolutely vital information about inductance, efficiency, response shape and helps with confirming that simulations are accurate. They are rarely provided with car audio market drivers though.


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## ZAKOH (Nov 26, 2010)

Peerless XXLS and its Scanspeaker Discovery clone are known to have excellent sensitivity. According to Klippel results on this web site and user reviews, they're very good SQ subwoofer. They are indeed the kind that require a biggish sealed box (the 12" model will be happy in 1.4-1.5cubes, perhaps with polyfull). These won't handle more than 300watts without going over xmax, but due to high sensitivity, at this point they will be sounding as loud as an average car-fi sub on 500watts or so. xmax is at 13 mm according to Klippel test on this web site. I don't think 13 vs 14mm will make a huge audible difference. The only downside is the big box requirement and that they can't be wired for 2ohm (the later would be great for powering them with a mono output on a weak 5-channel amp).


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## BuickGN (May 29, 2009)

I'm thoroughly happy with my AE IB15s. 91db 1w1m efficiency and a 152g Mms. 19mm xmax, 25mm xmech. Each one gets 250w off of a JL900/5 and it gets loud and low nearly flat from 20hz out well past 200hz and will play past 3khz. Most people can't believe what they will do off of such low power and its nice because I don't have to upgrade the charging system and I have no light dimming. The catch is they need a very large box, I run them infinite baffle to keep my trunk space. They also weigh only 17lbs if that's a concern.


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## yong_ly07 (Jan 12, 2009)

Well, wasn't DD originally a sq sub until all the spl guys started to use them for spl purposes? I can't see why DD would go wrong other than others criticizing that you have a spl sub when your intentional purpose is sq.


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## manowar_gub (Dec 18, 2012)

2 BuickGN
Can u share videos? and what's price should be paid...

2 yong_ly07
big mms...


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## Fricasseekid (Apr 19, 2011)

@ $170 each these 15s seem to have a lot of bang for the buck. 

http://stereointegrity.com/index.php?id=60

And stereo integrity is known for making great SQ subs.


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## Fricasseekid (Apr 19, 2011)

manowar_gub said:


> Hi!
> 
> Is I understand right that there can be high sensitive subs with xmax ~14mm? Searching for sub for playing flat-line from 30 hz @ 500 rms (ported of course) and find only heavyweight transmission like DD, SA...


Here's what I don't understand. From the jump this thread seems to equate sensitivity and SQ in a subwoofer. Are there not great SQ subs with very low sensitivity such as the dayton HO? 

What's the connection I'm missing here?


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## manowar_gub (Dec 18, 2012)

all high-sens subs are low xmax that's why they can't play low freq from 500rms and VC start to knock... I found a good one - epic 12 - but delivery was 140$ of 193$ price, too much... 

so I am looking for Gladen SQX12 which has 14 xmax, 167 mms and 88 spl/1w/1m @ 266$


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## BuickGN (May 29, 2009)

manowar_gub said:


> 2 BuickGN
> Can u share videos? and what's price should be paid...
> 
> 2 yong_ly07
> big mms...


I don't have any videos. I might be able to dig some pictures up. Install took a few hours (IB). They are sensitive and do have good excursion, 19mm xmax and 25mm xmech. While not a super xmax sub they have better than average excursion while being way more sensitive than normal with the large enclosure requirements being the only downside if you can't go IB. Several forum members have heard them and can attest to how loud and low they get off of very little power. 

I'm always trying different things and right now I have them low passed at 130hz now that I have the eq to tame them in he upper frequencies and they sound great. You can have your cake and eat it too if you have the space. 

The pair cost me $333 delivered to my door. Price has since gone up, I think they to for $199 each now which is still a bargain considering the efficiency, output, inductance, low moving mass, and overall sq. its doubtful you're going to come close in bang for the buck to these subs.

For the parameters you're looking for those Gladdens aren't even close. 91db efficiency, 825cm^2 cone area, 19mm xmax, 152g mms, $199; and one of the best sq subs on the planet.


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## Oliver (Jun 25, 2007)

Elevation audio SQX 12

Should work fine for you http://www.youtube.com/watch?v=peLMCY1YFs4


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## BuickGN (May 29, 2009)

If you're looking for an sq sub with great xmax, look at the 12W7 with 28mm xmax or the 13W7 with 32mm xmax and nearly 5" of total excursion. These are some of my favorite sq subs and they get loud, much louder per watt than the 86db spec would have you believe. They're a great sq sub with twice the excursion of the average sub.


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## kustomkaraudio (Jun 20, 2009)

BuickGN said:


> If you're looking for an sq sub with great xmax, look at the 12W7 with 28mm xmax or the 13W7 with 32mm xmax and nearly 5" of total excursion. These are some of my favorite sq subs and they get loud, much louder per watt than the 86db spec would have you believe. They're a great sq sub with twice the excursion of the average sub.


X2 !!!!!!!!!!!


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## Fricasseekid (Apr 19, 2011)

manowar_gub said:


> all high-sens subs are low xmax that's why they can't play low freq from 500rms and VC start to knock... I found a good one - epic 12 - but delivery was 140$ of 193$ price, too much...
> 
> so I am looking for Gladen SQX12 which has 14 xmax, 167 mms and 88 spl/1w/1m @ 266$


I still don't get it. The consensus here seems to be that all good SQ subs must have high sensitivity, lightweights cones, and therefore are low excursion? 

Explain to me why many home theater gurus advocate that you can add weight to a speaker cone in order to lower fs and increase sound quality? 

Plus wouldn't the speaker I posted above be an exception to much of what has been said here? It has an 87.4db sensitivity (about .5db less than the one you posted), an Xmax of 23.5, and an Mms of a whopping 309 g. It may be the most displacement you can buy for the money and is supposed to be a fantastic SQ sub. I have not heard a single bad thing about stereo integrity. 

So what am I missing here?


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## BuickGN (May 29, 2009)

Some people believe the Bl to Mms ratio is important for sq. I'm personally undecided. I can say that my favorite sq subs happen to have light cones but that might be coincidence. Some say distortion is good. Some say inductance is important. My two favorite subs are the IB15 and 13W7 which are very different subs except for a very light cone (for a car sub) IB15 and a pretty light mms W7/6. 

I can say that the IB15 will play midbass and midrange like no other which is probably a function of the Le over the low mms but who knows. I can trick people into thinking I have rear fill with some coaxials back there. The detail is very surprising. The reason I bring it up is I wonder if it has any impact on detail on the upper subwoofer range.


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## Fricasseekid (Apr 19, 2011)

So if I may paraphrase...

Modern technology has made way for much stronger motors, thus enabling subs to be equipped with much heavier cones and much higher Xmax without sacrificing sound quality? 



I had read somewhere that reproduction if frequencies below fs becomes only a function if how much air a speaker can move and nothing else. Does that play in at all here?


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## ErinH (Feb 14, 2007)

I believe inductance limiting methods is probably the most important aspect in regards to sound quality. Subs play multiple tones and the inductance through excursion will affect midband frequencies even above the low pass filter. You can't do anything about it unless you're limiting excursion and thereby crippling the intended use of a subwoofer itself. Though, this is a reason why the argument of multiple subs is often brought up. You limit excursion in one but achieve desired SPL by using multiples. Of course, with more manufacturers realizing this, it seems most subs implement faraday technology to reduce inductance over excursion and current.


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## BuickGN (May 29, 2009)

bikinpunk said:


> I believe inductance limiting methods is probably the most important aspect in regards to sound quality. Subs play multiple tones and the inductance through excursion will affect midband frequencies even above the low pass filter. You can't do anything about it unless you're limiting excursion and thereby crippling the intended use of a subwoofer itself. Though, this is a reason why the argument of multiple subs is often brought up. You limit excursion in one but achieve desired SPL by using multiples. Of course, with more manufacturers realizing this, it seems most subs implement faraday technology to reduce inductance over excursion and current.


I would be very interested in your opinion or observations of your IB15s compared to a "regular" sub in reference to the very low inductance. Mine seem to have less of a "change" in sound from low volume to high volume. I don't know of a better way to describe it other than the bass sounds the same as you turn the volume up, only louder. Maybe it's the lack of a box or maybe it's the inductance.

Have you ever run them full range just for the heck of it? If you haven't, it's quite an eye opener. 

Back to inductance I know you hate how the E430 midrange does not use a shorting ring but would you say my higher than the usual highpass (400-1,000hz depending on the mood) and less than 1mm of excursion would help with the inductance "issue" a bit?

I'm trying some "funky" stuff with the crossovers to where the only speakers with any visible excursion are the subs which luckily happen to be the ones with inductance taken care of.

Last, if I end up buying the JL 13W7s, are you still Klippel testing? I would like to see what happens with inductance as they push the full 32mm xmax.


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## manowar_gub (Dec 18, 2012)

I am listen for my Dragster 126.1 with low mms, high BL and high sens, listen for JL 12W6 - nothing unexpecting, only high price I founded, listen for DD512 - too smooth bass... high MMS are good for very slow sins (20 fluctuation per 1 sec is ok, but when you're started 50 fluc, there is no amazing BL to control them, and driver begin to smooth freq lines like this graphics below)...

as much BL we have @ low MMS, then better driver will play source. 

p.s. any opinions about IB15? I think good one...


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## ErinH (Feb 14, 2007)

BuickGN said:


> I would be very interested in your opinion or observations of your IB15s compared to a "regular" sub in reference to the very low inductance. Mine seem to have less of a "change" in sound from low volume to high volume. I don't know of a better way to describe it other than the bass sounds the same as you turn the volume up, only louder. Maybe it's the lack of a box or maybe it's the inductance.


I can't tell you why I like the AE IB15's so much. I just do. My only real issue isn't with them as much as it is the environment they're installed in. 



BuickGN said:


> Have you ever run them full range just for the heck of it? If you haven't, it's quite an eye opener.


I have a couple times. I could never get past the issues that propagated in the trunk (ie: standing waves) because it always had that 'pull to the back' sound. Drove me nuts. I do know plenty of people who use the same subs or a variation (ie: dipole 12/15, ae ob15, etc) in front of them in the home and love them crossed above 500hz. Personally, the giant null created in response off-axis keeps me from wanting to ever cross too high.



BuickGN said:


> Back to inductance I know you hate how the E430 midrange does not use a shorting ring but would you say my higher than the usual highpass (400-1,000hz depending on the mood) and less than 1mm of excursion would help with the inductance "issue" a bit?


It may. I try to view these things as what most people will do with them and then consider the extreme points. For a $800 driver, I can't believe they didn't use a shorting ring. Even if the intended application was to cross above the point it makes a difference. To me it's just future proofing and making the best possible speaker you can. 




BuickGN said:


> Last, if I end up buying the JL 13W7s, are you still Klippel testing? I would like to see what happens with inductance as they push the full 32mm xmax.


We'll see. I've got a good 'in' with JL so if I wanted to go that route I think it might be easier to deal with them directly in this regard. But, keep me in mind.


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## ErinH (Feb 14, 2007)

for a subwoofer, I think a shorting ring is absolutely important. after all, it is often the most limiting factor when considering linear excursion. and given the intended operation of a subwoofer, it's going to be an issue.


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## Patrick Bateman (Sep 11, 2006)

manowar_gub said:


> Hi!
> 
> Is I understand right that there can be high sensitive subs with xmax ~14mm? Searching for sub for playing flat-line from 30 hz @ 500 rms (ported of course) and find only heavyweight transmission like DD, SA...


Subwoofer sensitivity is almost completely meaningless.

Cajunner and Subwoofery posted some good responses on this subject.

The reason that subwoofer sensitivity is meaningless is because *the output of your subwoofer is ONLY limited by displacement when you satisfy two requirements:*
1) you have enough power
2) your sub can handle that power

If you can tackle these two things, then you're good-to-go. *This is why the guys winning SPL contests are doing it with low efficiency but sturdy subs, like the Sundown SA-8.*



If you want a driver to play loud AND sound good while doing it, look for one with a flat BL curve. Flattening the curve insures that the sub will sound the same at high volume and at low. The JL W7s, Alpine Type Rs, and Exodus Audio Anarchy subs have flat BL curves.

Adire Audio used to sell a lot of subs that adhered to this philosophy, and you can still find some of them on Ebay. Pioneer and Orion used to sell some subs with flat BL curves a few years back, not sure if they're still using the technology. The Diyma subs and the Peerless XLS subs have a variation on it too.


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## Patrick Bateman (Sep 11, 2006)

BuickGN said:


> Some people believe the Bl to Mms ratio is important for sq. I'm personally undecided. I can say that my favorite sq subs happen to have light cones but that might be coincidence. Some say distortion is good. Some say inductance is important. My two favorite subs are the IB15 and 13W7 which are very different subs except for a very light cone (for a car sub) IB15 and a pretty light mms W7/6.
> 
> I can say that the IB15 will play midbass and midrange like no other which is probably a function of the Le over the low mms but who knows. I can trick people into thinking I have rear fill with some coaxials back there. The detail is very surprising. The reason I bring it up is I wonder if it has any impact on detail on the upper subwoofer range.


Here's my .02 on the 'light cones versus heavy cones' thing:

I've *also* noticed that woofers with light cones tend to sound good. But I don't think the good sound is due to the woofer being 'faster' or something like that. I think it's because woofers with light cones tend to have light *everything.* IE, if you make the cone lighter, you can make the motor smaller, because there's less mass to move. And when you make the motor smaller, you'll often notice that they designer opted for a smaller voice coil. And *thats* what's causing the improvement in sound quality.

IE, I believe that a lot of the good sounding light-coned speakers tend to have small motors and small voice coils, *which happen to have low inductance.*

So in the case of light coned speakers, it's not the CONE that makes it sound better, *it's the low inductance.*


Now if you took that same tiny motor, and you slapped a big heavy aluminum cone on it, you'd get ultra high QTS, and one-note bass. It would sound like crap because the 'Q' is too high.

Due to this, most woofers with heavy cones often have big motors to get the 'QTS' down to a reasonable level. And since they're already adding mass to the motor, they tend to bump up the diameter of the voice coil.

So you end up with a big heavy motor, high power handling, a heavy cone, *and lots and lots of inductance.*

And it's the high inductance that causes the problem.

IMHO, that's why inductance and xmax are the two parameters I really look for, and it's kind of amazing how many speakers fail this test. It's also a bit of a bummer that companies that recognized how important this is (Adire Audio) never had much luck licensing their technology to the big manufacturers. (Pioneer, DEI Holdings, etc)



This is long and rambling I'll admit, but it basically boils down to this:

1) If you don't have a lot of power, you might consider a woofer with low xmax and low inductance. An example of this philosophy are the home audio guys who use tube amps and high sensitivity, low xmax, low inductance woofers like Fostex, Lowther, PHL, etc.

2) If you DO have a lot of power, pick a driver with a flat BL curve, a voice coil and suspension that can handle a lot of abuse, and the lowest inductance you can find. Ignore the sensitivity spec. Pay close attention to displacement.


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## Patrick Bateman (Sep 11, 2006)

BuickGN said:


> Some people believe the Bl to Mms ratio is important for sq. I'm personally undecided. I can say that my favorite sq subs happen to have light cones but that might be coincidence. Some say distortion is good. Some say inductance is important. My two favorite subs are the IB15 and 13W7 which are very different subs except for a very light cone (for a car sub) IB15 and a pretty light mms W7/6.


Art Welter at diyaudio did an interesting investigation of subwoofer distortion over at diyaudio:

Push Pull vs Normal Distortion Compared - diyAudio

His finding were similar to mine, which is that low subwoofer distortion *does* sound a bit 'odd.' I think we're so accustomed to distortion that when you take it away, it's not necessarily an improvement. Probably the first thing that I noticed with push-pull subs is that I *definitely* have a tendency to crank up the volume, easily 5-10dB louder than I would normally listen. I think the absence of second harmonic distortion makes the sub sound 'quieter', and so I crank up the volume to compensate.

This might also explain why some expensive subs are known to need a crapton of power. It's not just the lack of sensitivity, it's also the lack of distortion.

Distortion makes a speaker sound louder.


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## ErinH (Feb 14, 2007)

Patrick Bateman said:


> I think the absence of (omitted) distortion makes the sub sound 'quieter', and so I crank up the volume to compensate.


I actually have a very personal experience with this. I wouldn't say it's due solely to 2nd order so I omitted that, but I do believe that we've gotten so used to distortion than when a speaker doesn't exhibit higher levels of it, it's harder to tell it's getting louder. As if distortion is our defining characteristic of getting loud.

I noticed this most prevalently on an OB setup with a higher efficiency fullrange (tb w8-1772) with a Peerless XLS 12 (iirc). it sounded incredible. But it was almost dangerous to listen to because I kept turning it up to get louder and louder. I realized I was listening to much higher levels than I typically do and it still sound crystal clear. I've yet to have an experience like that with any other speaker system.

On that note, regarding the P-P design, I've wanted to test this myself but haven't yet come up with a way to reliably do this. Mainly because I'm limited to the microphone's SPL limitation which drives mic distance which affects the measured response due to the room.


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## Patrick Bateman (Sep 11, 2006)

bikinpunk said:


> I actually have a very personal experience with this. I wouldn't say it's due solely to 2nd order so I omitted that, but I do believe that we've gotten so used to distortion than when a speaker doesn't exhibit higher levels of it, it's harder to tell it's getting louder. As if distortion is our defining characteristic of getting loud.
> 
> I noticed this most prevalently on an OB setup with a higher efficiency fullrange (tb w8-1772) with a Peerless XLS 12 (iirc). it sounded incredible. But it was almost dangerous to listen to because I kept turning it up to get louder and louder. I realized I was listening to much higher levels than I typically do and it still sound crystal clear. I've yet to have an experience like that with any other speaker system.
> 
> On that note, regarding the P-P design, I've wanted to test this myself but haven't yet come up with a way to reliably do this. Mainly because I'm limited to the microphone's SPL limitation which drives mic distance which affects the measured response due to the room.


For nearly half a decade, my home reference speakers were Gedlee Summas, and it kinda ruined me for all other midbasses.

The midbass driver isn't terribly expensive, but it has SO MUCH displacement that it's output is just effortless. (B&C 15TBX100)

For anyone playing along at home, here's how the 15TBX100 stacks up against a well regarded car audio midbass. In the specs we see that the Focal has very very low inductance, which will make it sound better particularly at high frequency IMHO. But the B&C 15TBX100 just has crushing displacement, which gives it that 'effortless' quality that's so satisfying in the midbass. And though the 15TBX100 has inductance that's nearly eight times higher, it's *still* lower than 90% of the fifteens out there, and even lower than a lot of sixes and sevens that lack shorting rings.

driver: B&C 15TBX100 vs Focal 6 KRX 3
displacement (liters): *0.7695* vs 0.07315 <--- no that's not a typo, it has more than TEN times as much displacement
inductance (mh): 1.6 vs *0.2*
cost, per pair: *$598* vs $2000*

spec sheets here:

B&C SPEAKERS

http://www.focal.com/files/ft-165-krx3.pdf

* Focal is part of a component set that includes crossovers and tweeters


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## manowar_gub (Dec 18, 2012)

Is I understand right that as inductance lower then impedance better (not too high/low values) and amp will work well, control driver and achieve accurance sound?


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## ErinH (Feb 14, 2007)

http://www.eighteensound.com/staticContent/technologies/products/18_Sound_DDR.pdf

Pay attention to #3.

Note that intermodulated distortion effects are primarily outside the passband of the subwoofer. While you may think it's a non-issue since you're crossing over before 100hz (for example), keep in mind the woofer is still moving through the gap and the high inductance is caused by this movement forward and backward. Using a LPF won't really do much to the excursion and therefore you still have these high(er) frequency distortion issues. IOW, a LPF won't stop intermodulated distortion caused by inductance issues from occurring.

One way to test for something like this is to turn off all the speakers and listen to your sub. Pat @ Red Rock suggested this to me and it was relevant there was certainly a contribution of distortion from the subwoofer itself even though it was Low Passed at 80hz. This is why inductance control is a very important factor when considering subwoofers.

Edit: If I get some free time this week, I'll try to emulate what I posted above as another example. With the Klippel SIM module I can simulate driver performance based off real measurements (used by many manufacturers to simulate performance to save on R&D costs) and then alter the inductance curves to provide a "with and without shorting ring" comparison as the above linked has done. If nothing else, it'll be a good exercise for me to use the SIM module.


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## Oscar (Jun 20, 2010)

manowar_gub said:


> Is I understand right that as inductance lower then impedance better (not too high/low values) and amp will work well, control driver and achieve accurance sound?


Low inductance (and variation) = good for SQ
Flat BL vs excursion curve= Great for SQ 
high BL²/Re = great for efficiency (not the same as sensitivity) _IFF_ you can build the box large enough to reap the benefits of that greater efficiency. Efficiency does not work on it's own just as a subwoofer sitting in free-air doesn't work at all---you ALWAYS need the enclosure component.

Usually drivers that a high(er) Vas for their cone size indicate they need a larger enclosure, but this is what helps sensitivity (_IF_ you're limited on power--in other words if you have very low power)...but you don't want too high that it ends up using a super flimsy spider that is gonna rip.

What it comes down to is this:

you need to be honest with everyone and yourself about how much power you are actually going to run in your vehicle. I don't just mean amplifier---is your car's electrical system prepared to handle high power amplifiers (if that is the route you're going)??


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## manowar_gub (Dec 18, 2012)

I think my amp can get 500 rms/4 ohm & 700/2 ohm @13.8V

so, SQ subs (subs who can play source signals too accurance) have 3 definitions:
1. BL to MMS ratio (as stronger magnet system can control cone, then better)
2. inductance - as lower then better (past signals make past magnet field withous remains of last magnet field)
3. flat impedance (amp don't overloads at high/low impedance)

true?


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## Ricci (Sep 30, 2008)

Oscar said:


> Low inductance (and variation) = good for SQ
> Flat BL vs excursion curve= Great for SQ
> high BL²/Re = great for efficiency (not the same as sensitivity) _IFF_ you can build the box large enough to reap the benefits of that greater efficiency. Efficiency does not work on it's own just as a subwoofer sitting in free-air doesn't work at all---you ALWAYS need the enclosure component.
> 
> Usually drivers that a high(er) Vas for their cone size indicate they need a larger enclosure, but this is what helps sensitivity (_IF_ you're limited on power--in other words if you have very low power)...but you don't want too high that it ends up using a super flimsy spider that is gonna rip)


I disagree with this somewhat. The efficiency differences between the raw drivers is always present in the system. Granted these differences often are not huge but they can be significant. A larger enclosure will increase deep bass efficiency but that is not what is being discussed and it will apply to both drivers equally such that any basic efficiency differences are maintained. When two drivers are directly compared in equivalent systems the efficiency difference will be there. Basic FR sensitivity is not a good way to compare efficiency differences. The impedance curve must also be considered along with the sensitivity measurement. The differences in system design, enclosure alignment and size, driver parameters and impedance magnitude with frequency make direct comparisons between systems difficult. In most cases one system or the other will have greatest efficiency over a different frequency range as well. 

Typical content (not test signals,sines, etc.) is broad bandwidth, time variant and complex. With these types of signals a more efficient driver will be able to extract more output when using the same amplifier assuming both drivers are in an identical system and are not being operated past their limits.

Obviously there are many other major factors when selecting a sub driver that need to be weighed (perhaps heavier) than driver efficiency but IMHO it is not irrelevant.


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