# Boston SPG-555



## npdang (Jul 29, 2005)

A big thank you to Werewolf for donating the sub!

This sub is surprisingly light for it's size, and well constructed. The cone is both sturdy and lightweight. The voice coil assembly is easy to remove and replace; in case you were to ever damage the voice coil, replacement takes less than 5 minutes. There are also small venting holes under the spider and on the back of the motor. Interestingly, the large voice coil is wound on what looks like a Kapton former and attached to a metal piece with holes drilled through. 

Performance wise, you see a typical parabolic bl curve that's heavily offset nearly a cm in the forward direction. Le curve shows that no shorting ring is used. Suspension looks like quite a bit of throw, but again offset. This test barely taxed the limits of the suspension. Unfortunately I wasn't able to test the limits of the driver further; as you can see the driver temperature exhibited an increasing change up to 150 K at about 350w of power. This was the safety limit of the test. Both the motor and coil were quite warm to the touch. This was a first for me, as I find most subs do not exhibit this drastic change of temperature so quickly. Given the t/s parameters of the driver, the large voice coil and replacement system, as well as the very long throw I'd take a guess and say that this driver was designed for high output spl, albeit the cooling is subpar to other drivers that I've tested. Although the driver is well "sinked" with cooling fins, it appears that airflow maybe a bit restricted with only small holes along the bottom for venting and no direct exposure to air for the voice coil.

Some pics, including one of my Seas neos inside the voice coil.


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## Guest (Apr 6, 2007)

Very interesting! I would agree ... the measurements do indeed suggest SPL usage, rather than low-distortion SQ applications. It's a good thing that the coil is easily replaced, since it seems that Boston kinda dropped the ball on thermal management


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## SQ_Bronco (Jul 31, 2005)

npdang said:


> Performance wise, you see a typical parabolic bl curve that's heavily offset nearly half an inch in the forward direction. Le curve shows that no shorting ring is used. Suspension looks like quite a bit of throw, but again offset. This test barely taxed the limits of the suspension.


Would you mind going into a bit more detail as to how you know these things, from looking at the charts you've shown? Esp re: comment #2- is it the slope of the inductance curve (line?) that tells you that there is no shorting ring, or something else? I would have had no clue how to interpret this data if you hadn't already indicated that it was "not optimal", and i bet a lot of the people who read this site are in a similar situation. It's really nice to see actual data on this stuff though. It'll be great to see how the different subs compare once you get a good sample size set up.

I like how the voice coil is completely separate from the suspension--pretty good design, from a mechanical standpoint. Not sure i could think of a better way to do it;are there any other subs that do something similar?


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## backwoods (Feb 22, 2006)

Am I wrong in assuming this looks like it might be a great IB driver for a more spl oriented application?

My impression is that I would be able to get more out of the suspension, without having to worry AS MUCH about the thermal limits.

Obviously, I'm not as well lurnt at reading these as well as you guys.


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## MIAaron (May 10, 2005)

As long as you're cool with an Fs of 35hz.


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## npdang (Jul 29, 2005)

Typically, I find an fs of 35hz too low for IB applications in a car. For a flat response in most mid-sized sedans, you'd be aiming for around 60 to 70hz. But for spl applications 35hz should be more than adequate.


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## backwoods (Feb 22, 2006)

even higher then I expected...so not too surprised..


but you do have a point dang..


this would be going in my mustang, so sq won't be a main priority. The pipes are kinda loud.


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## npdang (Jul 29, 2005)

There is a sticky in this forum called "read me first" that may help explain how to evaluate the performance of a driver with Klippel measurements, although it does not explain how to evaluate the root causes of those measurements.

From experience, I know that certain designs and motor geometries yield certain results. The Klippel paper on "Diagnosis and Remedy of Nonlinearities in Electrodynamical Transducers" at http://www.klippel.de/pubs/aes2000/klippel paper 109.htm is also an excellent guide in understanding why the curves look the way they do, and the the resulting effects of those causes.

This is the explanation (taken from the above link) for why the inductance is higher on the forward movement than on the rearward stroke for a driver with no shorting ring.

"The inductance of the voice coil describes the total magnetic flux generated by the voice coil current. If the driver is not equipped with additional means for reducing this flux the inductance varies in a characteristic way with the displacement x. As shown in Fig. 9 the air path and the magnetic resistance for negative displacement x1 is much smaller than for positive displacement x2 resulting in a higher flux and inductance."


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## HCCA (Apr 6, 2007)

I believe AVI is using one of these in his vehicle. He is powering it with one Arc Audio 2300SE. From what he told me, it is one of the finest SQ subs you can buy at any price. As for questions of will this play in IB, why? It is designed to play in a 1cft sealed enclosure, and sound great doing it. It's not THAT hard to make a sealed box. Whatever the measurements show, it really always comes down to a listening test. This sub's design is really not that different from the Critical Mass Ultimate series sub. And, those subs were reviewed to be phenominal SQ subs, too.....if you don't mind the price tag. http://criticalmassaudio.com/catalog/index.php?act=viewCat&catId=12


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## npdang (Jul 29, 2005)

Personally, I think measurements go hand in hand with subjective experience. 

Don't get me wrong... I'm not trying to tell anyone what to think or hear. If you heard the sub and you think it sounds great and you could care less about measurements then that's all that matters.

However, in my book and my humble opinion, a driver that measures this way with high peak-peak excursion and relatively higher distortion and a q of over .7 is not optimized for SQ or small box use.


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## JAG (May 6, 2006)

npdang said:


> Personally, I think measurements go hand in hand with subjective experience.
> 
> Don't get me wrong... I'm not trying to tell anyone what to think or hear. If you heard the sub and you think it sounds great and you could care less about measurements then that's all that matters.
> 
> However, in my book and my humble opinion, a driver that measures this way with high peak-peak excursion and relatively higher distortion and a q of over .7 is not optimized for SQ or small box use.


Did you listen to it in a car ? I'd try it before I knocked it Nguyen. It sounds nothing short of amazing in my car , and i'm a SQ fanatic


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## npdang (Jul 29, 2005)

I don't doubt it sounds amazing in your car, but I bet it has more to do with your skill as an installer and tuning than anything else


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## FoxPro5 (Feb 14, 2006)

npdang said:


> I don't doubt it sounds amazing in your car, but I bet it has more to do with your skill as an installer and tuning than anything else


What other subs have you tested that didn't show stellar testing numbers, yet received very positive user feeback. I mean, in scientific terms, what's the generalizability to the real world environment. Again, with subs only...not other drivers. 

I think it's great that we have a blend of the "science types" and the "tuner types" on this forum. I like to hear both sides. Now if we could just get along......


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## npdang (Jul 29, 2005)

Honestly I think it does correlate pretty well if you're drawing the right conclusions about the data.

Things such as:

1. Distortion performance could be improved
2. Thermal performance is a bit subpar as compared to other driver's I've tested
3. An overdamped alignment in a small box isn't achievable

Now, none of that necessarily says that the driver can't sound good or be used for sound quality purposes. There are obviously many more factors that influence whether a sub sounds good, albeit Imho not so many as say a midrange or tweeter.


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## Genxx (Mar 18, 2007)

This is very interesting. I assumed that after reading reviews that this would be one of the greatest SQ subs ever released, if not the best. Scince then I have seen reviews go both ways proving npdang's test and then others following AVI that this is one of the very best ever. However, I would still agree that alot of it is the ability of the installer/tuner and the acoustics of the vehicle. I am sure we have all heard atleast one sub in multiple installs and some were very impressive and others did not even sound like the same speaker. So I vote a combination of testing data and installer/tunning ability often meet in the middle to accomplish the perfect sound reproduction, as close as we can get it atleast.IMO

The ultimate testing tool is always the users ear, as we are all different.IMO

Now if I could just have npdang, Chad, AVI and others send me a learn by osmosis book I should be set.


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## DS-21 (Apr 16, 2005)

Genxx said:


> This is very interesting. I assumed that after reading reviews that this would be one of the greatest SQ subs ever released, if not the best.


Why? Basically there was one person (who happens to be a dealer for it) hyping it. If I may be so bold, the test results panned out basically as expected...


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## Genxx (Mar 18, 2007)

DS-21 said:


> Why? Basically there was one person (who happens to be a dealer for it) hyping it. If I may be so bold, the test results panned out basically as expected...


*Hyping answer*-I had friends that own shops and installers that I know that where hyping it. They hyped it to know end. Then there are threads everywhere saying this is the end all be all. It was just like when the W7 hit the market and all the reviews started coming out. People who never ran JL where dropping the money and trying to reserve theirs.

*Test results answer*-I assumed that from what I had heard that this sub we be a huge surprise but the data has not supported that(unless I am reading the graphs wrong/which could be the case), from what I have seen. You are right it turned out basically as expected. I guess I should not assume so much until the data comes out and in car user reviews start popping up. I just guess I just figured it would have some crazy super flat response, play super low, high and do it effortlessly, mabey I am asking for to much huh. Wouldn't be the first time. 

I think I just bought into all the hype. I was always skeptical about the W7 because it was so different and had ran JL for years prior. Now I regard the W7 as one of the best and I would run it without any questions asked.

BTW-No I have not got the chance to hear one yet and I might Sh** my pants if was truely awsome. If someone wants to give me one I will try it out though, don't think that is going to happen though.


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## JAG (May 6, 2006)

Genxx said:


> *Hyping answer*-I had friends that own shops and installers that I know that where hyping it. They hyped it to know end. Then there are threads everywhere saying this is the end all be all. It was just like when the W7 hit the market and all the reviews started coming out. People who never ran JL where dropping the money and trying to reserve theirs.
> 
> *Test results answer*-I assumed that from what I had heard that this sub we be a huge surprise but the data has not supported that(unless I am reading the graphs wrong/which could be the case), from what I have seen. You are right it turned out basically as expected. I guess I should not assume so much until the data comes out and in car user reviews start popping up. I just guess I just figured it would have some crazy super flat response, play super low, high and do it effortlessly, mabey I am asking for to much huh. Wouldn't be the first time.
> 
> ...


Well ... I'm sure Nguyen's tests have proved this sub has some issues with it's design .... I'm also sure those tests may well point to issues that should effect the sound , however all I can say is that my sub bass is nothing short of incredible sounding ....


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## Genxx (Mar 18, 2007)

I know when I am in over my head on this. So I will say I have not heard one so I can only look at data to really judge. AVI I know you have one and love it. I respect you and Nguyen's opinions. I can only state my opinion as my knowledge base is not to even 1/2 the guys on here, at least I think so. I was just trying to answer the questions asked and how I interpreted the data. Will I change my tune or would my tune be different had I heard one maybe so. I am trying to listen to one in a car but they are hard to find to listen to where I am.


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## newtitan (Mar 7, 2005)

may I ask a quick one to AVI (box size??) im plotting this in bass box pro, and im getting 2.61 cu ft, no damping, Q=0.707, F3=37.48


seesm large, what volume are you using? the manual state 1 cu ft, while using the Boston amp Q adjusment function?

just considering a 12" woofer subjective test of my own, so may buy one, but not if if needs a box that big lol


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## JAG (May 6, 2006)

newtitan said:


> may I ask a quick one to AVI (box size??) im plotting this in bass box pro, and im getting 2.61 cu ft, no damping, Q=0.707, F3=37.48
> 
> 
> seesm large, what volume are you using? the manual state 1 cu ft, while using the Boston amp Q adjusment function?
> ...


I started with the 1cu ft box , but found that it needed too much EQing without using the Q-tune on the Boston amps .... So I went with 1.5 cu ft , and have had great results. 2.6 sounds awfully big to me ...


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## DS-21 (Apr 16, 2005)

Genxx said:


> *Hyping answer*-I had friends that own shops and installers that I know that where hyping it. They hyped it to know end. Then there are threads everywhere saying this is the end all be all.


As a general rule, people who own shops and professional installers (especially if they're heavily into the competition scene) _usually haven't heard anything really good._ That's because the mainstream car-fi industry (with a few exceptions such as the JBL WGTi series) produces very little that's designed or built to the standards of the stuff available to DIY hobbyists, though they pay much more for substandard gear with gaudy-ass cosmetics...

The smarter boutique brands tend to take commonly-available hobbyist kit and mark it up into the stratosphere. Some people are too young to remember when USD was hawking NHT 1259's available to anyone for $150 + shipping for $350 or so, but in more recent memory companies such as Genesis and Xetec took the excellent Peerless XLS and asked their buyers to pay about 2.5x the going rate for the privilege of a dustcap with their logo screened onto it...


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## Guest (Apr 9, 2007)

I swear I've come to a conclusion about box size recommendations from manufacturers ... maybe consider this an addendum to what DS-21 just posted (i'm really on uncomfortable ground here, by the way, as i find myself in agreement with _way_ too many of his posts lately  ).

I submit that box size recommendations from manufacturers have absolutely nothing to do with Qtc, or sound quality at all. They are purely based on power handling requirements. Smaller boxes mean the sub handles more power, period. And that's the basis for the recommendation. Because as we all know ... "powerful subs" sell 

Never mind that power handling is meaningless without efficiency. Never mind that getting the job done with _less_ power is _not_ a bad thing. And, never even think about explaining concepts like Qtc, frequency response, cabin gain, or Hoffman's Iron Law. The only thing that matters is posting high power numbers, and minimizing warranty returns from blown subs.

:end rant:


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## bdubs767 (Apr 4, 2006)

werewolf said:


> I swear I've come to a conclusion about box size recommendations from manufacturers ... maybe consider this an addendum to what DS-21 just posted (i'm really on uncomfortable ground here, by the way, as i find myself in agreement with _way_ too many of his posts lately  ).
> 
> I submit that box size recommendations from manufacturers have absolutely nothing to do with Qtc, or sound quality at all. They are purely based on power handling requirements. Smaller boxes mean the sub handles more power, period. And that's the basis for the recommendation. Because as we all know ... "powerful subs" sell
> 
> ...


And people wonder why we move away from speakers designed for car audio world...


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## Genxx (Mar 18, 2007)

DS-21 said:


> As a general rule, people who own shops and professional installers *(especially if they're heavily into the competition scene) usually haven't heard anything really good*_._ That's because the mainstream car-fi industry (with a few exceptions such as the JBL WGTi series) produces very little that's designed or built to the standards of the stuff available to DIY hobbyists, though they pay much more for substandard gear with gaudy-ass cosmetics...
> 
> The smarter boutique brands tend to take commonly-available hobbyist kit and mark it up into the stratosphere. Some people are too young to remember when USD was hawking NHT 1259's available to anyone for $150 + shipping for $350 or so, but in more recent memory companies such as Genesis and Xetec took the excellent Peerless XLS and asked their buyers to pay about 2.5x the going rate for the privilege of a dustcap with their logo screened onto it...


Your first statement-*This statement is way to general*. One of my buddies this would apply to, the other hell no, not even close. The highlighted statement is complete crap. I competed in the past, will compete again and know a lot of others that do and we have actually heard a lot of these brands, if you will(for most its not our first rodeo). Some of the same guys that compete by home stuff to which uses many other brands, we actually read forums. *Not DIY experts I give you that*.

Second statement-*I agree this happens*. Sames as Alpine with some there Type X and F1 stuff and there are others doing it.

So to stay on subject at some point I will here this Boston in a car properly set-up and we will see if AVI is 100% correct.*IMO * I however like my ARC sub for now but that it subject to change at anytime.


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## cvjoint (Mar 10, 2006)

Genxx said:


> Some of the same guys that compete by home stuff to which uses many other brands, we actually read forums.


...and DS-21 was desperately smoking pack after pack trying to figure this one out...


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## newtitan (Mar 7, 2005)

AVI said:


> I started with the 1cu ft box , but found that it needed too much EQing without using the Q-tune on the Boston amps .... So I went with 1.5 cu ft , and have had great results. 2.6 sounds awfully big to me ...


check the screen capture

does this look right to you?? im confused and curious 

maybe I entered something wrong


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## npdang (Jul 29, 2005)

F3 is a bit low in that large of a box for car use, although if you're looking for a maximally flat response that would be the correct size.


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## Genxx (Mar 18, 2007)

cvjoint said:


> ...and DS-21 was desperately smoking pack after pack trying to figure this one out...



I am pretty sure DS-21 is really going to let me have it now. Its ok though because I respect DS-21, he has alot of knowledge. But I have got him going on me now. So I am going to stop and quit placing possible aggrivating statements in there before everyone starts chewing me up. 

I still want to hear a SPG-555 set-up properly in a vehicle.

*Some of the same guys that compete by home stuff to which uses many other brands, we actually read forums*. What I meant buy this is that I am not taking an Alpine Coxial and trying to make a home speaker out of it. I personally buy stuff from places like madisound and other places. I take what I learn from sites(DIY) and try to teach myself through reading, applications. Some guys who compete actually try but there are some who compete that you can't tell anything. But its not like I could fit lets say a big Martin Logan in my car or that it would even sound the same. This will be a bold statement-Alot of car speaker companies steal/take/borrow/buy speaker designs from the home audio world.


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## HCCA (Apr 6, 2007)

Well, my system won't go in until August, but I'm getting an SPG-555. If everyone can wait until then, I'll post my personal review.


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## Rbsarve (Aug 26, 2005)

In a normal sized car, we have had great results SQ-wise using boxes with a Qb of about 0.85 for drivers with an Fb below 45 Hz. That usually results in a very nice blend with the cabin related transfer function.

I suspect that is what AVI is seeing...


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## zfactor (Oct 19, 2005)

so i have a customer looking for a great sql driver.. how well does this driver do when pushed with rap and hip hop pretty damn hard when he wants it really loud.. now im thinking a pair here of these.. what do you think


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## DS-21 (Apr 16, 2005)

Genxx;115546[B said:


> Some of the same guys that compete by home stuff to which uses many other brands, we actually read forums[/B].


If one competes with quality gear one is at an immediate political disadvantage because car audio competition is really only about two things: selling car audio-marketed product, and giving talented professional installers an outlet to relieve the tedium of a day full of "deck-and-fours."



> But its not like I could fit lets say a big Martin Logan in my car or that it would even sound the same.


I'm not sure what that has to do with knowing the difference between a fundamentally excellent 12" subwoofer driver (say, a Peerless XLS or a TC Sounds TC1000) and a fundamentally ****ty 12" subwoofer driver (pretty much everything marketed to car-fi). Why? Because for the most part they've no experience with the real thing. Only with the bechromed turd.



> This will be a bold statement-Alot of car speaker companies steal/take/borrow/buy speaker designs from the home audio world.


For one thing, I'm pretty sure I covered that by mentioning instances such as USD overpricing an NHT 1259 and Genesis/Xetec selling Peerless XLS's for well above what one can get them for from Madisound, etc.

For another, it runs both ways. JL Audio seems to have started a trendlet for 13" subwoofer drivers, for instance. Now SVS is doing one. I pointed that out some short-sleeve-button-down-and-polyester-tie car dealer type on the AVS forum, and he proved quite unable to read simple written English...


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## Genxx (Mar 18, 2007)

DS-21-Thanks I was just waiting for you to get me good. I bow you win. Thanks for not flaming to bad. I try but my level of knowledge of DIY is only at mabey a 3 and yours is at let say 8.75-10.0. But I am learning from reading and trying new things and even when you flame me I learn something.

Thanks Genxx


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## 00poop6x (Jan 20, 2007)

Old thread, I know. But I'm going to have to agree with AVI, give it a listen, please.

Perhaps Boston Acoustics tends to engineer their mobile audio products to sound good in a car--or they're lucky.

Been listening to one for quite some time now.


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## bbfoto (Aug 28, 2005)

Which Coil do you have in the sub? 4-Ohm or 2-Ohm?


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## 00poop6x (Jan 20, 2007)

bbfoto said:


> Which Coil do you have in the sub? 4-Ohm or 2-Ohm?


2-Ohm


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## DT053 (Mar 23, 2007)

Was there something wrong with the speaker before testing... had something been sitting on the cone before testing? 
Meaning, I doubt the voice coil was offset 7 or 8mm on purpose. Looking at the BL symmetry graph, does it show a straight line of offset for the VC to be in the center of the flux field, or is it a curved line? I suspect it's pretty much a straight line.

I suppose BA could have offset the VC for verious sound quality reasons, but I doubt it for this type of driver.

Thanks
DT


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## TiEcs (Sep 3, 2008)

Can someone advice me where to get the passive radiator SPG-TR?
In Europe it isn't available yet.
I contacted Crutchfield, but they don't sell it.


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## 00poop6x (Jan 20, 2007)

TiEcs said:


> Can someone advice me where to get the passive radiator SPG-TR?
> In Europe it isn't available yet.
> I contacted Crutchfield, but they don't sell it.


Contact Boston Acoustics


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## TiEcs (Sep 3, 2008)

00poop6x said:


> Contact Boston Acoustics



I did, about one week ago. And guess???
They didn't answer


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## 00poop6x (Jan 20, 2007)

TiEcs said:


> I did, about one week ago. And guess???
> They didn't answer


They didn't answer their phone????

Hmmm... let me see what's going on.


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## TiEcs (Sep 3, 2008)

00poop6x said:


> They didn't answer their phone????
> 
> Hmmm... let me see what's going on.


I contected them by mail


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## lgas37 (Sep 27, 2008)

looks awsome


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## Shod (Oct 6, 2008)

I am new to this site and seen this blog about the spg555 and I have to say this sub is one the the best that I have ever bought. I actually have two of them 2ohm in a 1.2cuft sealed box made out of 1'' baltic birch powered off of an older cadence A7 each sub is getting around 675 per and I am getting am excellent response from them for sq and spl. You can tell that they want to play loud and they diffently can but they still give you that sq that you want. And as far as the radiator goes it has not been released yet.


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## xtremeDAN (May 28, 2009)

iv put a few of these in and it was for a customer who wanted more bass the sq. the 1 cubic foot sq box they list does not sound very good when hooked up to a sound board but im guessing that had a lot more to with the tuning and lack of a good amp and power supply. not to mention a rattleing suspended ceiling. But in the right ported box they can get loud in a car.


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## scotty89 (Apr 7, 2011)

OK... so this wasn't quite what I was expecting when I entered this thread. I was hoping for praise, like everywhere else I looked.

What size box should I be aiming for in a SQ setup @ the rated 1000wrms (w/o this Q setting that BA amps apparently have?)?

1 cubic foot? 1.5, 2.0? Am I wasting my time?


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## EricP72 (Mar 23, 2008)

I have mine in a sealed 1.3 cubic box. I'm using a Hertz ep1d amp and out is decent, but I don't like it. I don't get the impact that I'm looking for. I will try adding some wood inside to make the air space smaller. Mine is 2ohms


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