# Factory Bose/DIY thoughts?



## sub_junkie (Apr 14, 2009)

I have the Bose 301 Series 2 bookshelf speakers, and they're actually pretty decent sounding. Here's a link to them.

http://www.retrevo.com/d/ds/progress?doc=430c16e0b76a17c0036114310fbbb18b&rk=0.26691274461336434

(you'll have to download the pdf for them...)

What I'm wondering is I'm lacking on bass from them, so what 8" woofers could I throw in their box, that would boost the base quite a bit? If needed, I could build another box for them, as the current one has some port noise around 30hz. I don't really care about these front speakers going that low, but it would be nice for when I do listening with no sub.

My apologies if this is in the wrong section, I didn't know if it should go in DIY projects or manufactured speakers.


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## GranteedEV (Aug 8, 2010)

I genuinely think this is going to be a waste of time and money. 


You can't just swap out the midwoofer, because that will require a new crossover.
Building a new box will change the diffraction and baffle step behaviour, so the crossover will need to be changed.

Of course, IMO those 301s don't actually sound as nice as you might think.

If you're willing to start from scratch or do an established design, I think you can build an outstanding speaker, though! An 8" woofer you could start with, would be the JBL 804. There is also an 8" alpine driver that will work nicely. The Dayton reference stuff, I think is meant to be used in multiples rather than a single, though it's also a great choice.

You would then need mids to blend to the driver.


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## sub_junkie (Apr 14, 2009)

GranteedEV said:


> I genuinely think this is going to be a waste of time and money.
> 
> You can't just swap out the midwoofer, because that will require a new crossover.
> Building a new box will change the diffraction and baffle step behaviour, so the crossover will need to be changed.
> ...


There's no speakers that could somewhat match the crossover ? 

And they definitely don't amazing by any means, but for being about 20 years old and sitting in a garage, they still sound fairly good. 

And I would absolutely love to build a new set of front towers, but I just can't afford it right now. Car insurance and college comes first ! Haha. 

What I would really like to do for my towers would be a MTM design, and a 10" subwoofer (sealed or ported) in both of them, just with the box sealed off between the MTM and sub. About how much do you think it would cost to do something like that ? Since there would be a sub in it, the midwoofers wouldn't have to have the best extension, but I would like the tweeter to be really clean and clear. I really like excellent mids and highs.

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## GranteedEV (Aug 8, 2010)

sub_junkie said:


> There's no speakers that could somewhat match the crossover ?


No, because the impedance and acoustic response are not going to match.

For example, for starters don't know what the rolloff of the midrange is. You need to match acoustic slopes to get proper summation.

Second there's a matter of complex impedance. The way a passive crossover works isn't just a function of frequency like with an active crossover (IE what a receiver will use).

The way inductors and capacitors interact with drivers in order to change their acoustic response, is very dependant on on their complex impedance behavior. This is why "off-the-shelf" crossovers are a garunteed disaster. Driver impedance is always changing so we need to optimize every crossover for every individual driver. Active crossovers are more forgiving, but require multiple separates amps.

Then there's still a matter of sensitivity. If the old woofer was 93db sensitive, you can't just swap it out with a 85db sensitive woofer without padding down the rest of the frequency range.




> And I would absolutely love to build a new set of front towers, but I just can't afford it right now. Car insurance and college comes first ! Haha.


No, I meant something _much_ simpler, like a 2-way bookshelf with that 8" woofer mated to a full range driver like 

http://www.creativesound.ca/pdf/CSS-EL70-data-080909.pdf or http://www.creativesound.ca/details.php?model=WR125ST or http://www.madisoundspeakerstore.com/approx-4-midrange/scan-speak-discovery-10f/4424g-4-midrange/
It can sound surprisingly great - many times better than many of the traditional speakers we're so used to, even in the upper ranges.



> What I would really like to do for my towers would be a MTM design, and a 10" subwoofer (sealed or ported) in both of them, just with the box sealed off between the MTM and sub. About how much do you think it would cost to do something like that ?


You're probably looking at around $700-1200 for such a tower. It's not an MTM, but Dennis Murphy's MBOW1 3-way

http://murphyblaster.com/content.php?f=MBOW1_3-WAY.html

Is a 3-way with a 10" woofer, that I think will surprise you in how good it is. That peerless woofer is also a great choice in the above 2-way I discussed, although it does likely increase box size.



> Since there would be a sub in it, the midwoofers wouldn't have to have the best extension, but I would like the tweeter to be really clean and clear. I really like excellent mids and highs.


A passive 3-way imo should have drivers with really good bandwidth and dispersion and shouldn't be forced to play the lowest octave, which I still think is sub territory. A 3-way that is forced to play down to 20hz, should be active/bi-amped in order to keep sensitivity higher. THe woofer is not a subwoofer, but rather needs to be able to cover up to around 400hz (and thus have clean bandwidth all the way to 1khz for a smooth transition). There are some excellent 12" woofers that fit this criteria and that's definitely what i'd do. Acoustic Elegance, Peerless, Seas, Scanspeak, and Eminence in particular are great woofer brands. I don't think metal cones are appropriate for passive crossovers, because it's so easy to miss the breakup frequency with notch filters, especially at higher power levels where heat causes the impedance characteristic to change.

You then need a midrange that also has a wide bandwidth. You want it to be able to blend seemlessly to the tweeter. Some people will tell you that off axis response tends to be optimized by using small midranges with 2nd order acoustic crossovers to flush mount tweeters. Others will tell you that larger midranges (IE 8") should be used to minimizes dispersion width and output. If using a larger midrange, you want to use a waveguide for the tweeter, in order for the dispersion to be consistent. Again, if metal cones are used, I recommend active crossovers to make sure you're always getting the cone breakup no matter what temperature the driver is operating at. Nothing sounds worse than a missed metal cone breakup from a midrange, and this is what causes people to think some tweeters sound poor.

For a tweeter, I'm of the opinion that many tweeters sound rather nice. The biggest differences, come in the ability to blend to the midrange. Many revered dome tweeters like a Seas Millenium, Scanspeak 6600, and Scanspeak 9500, (and a Dayton RS28F) don't have as much top octave air as smaller tweeters (Hiquphons, and Ribbons) but make up for it greatly because they can play so low with higher power, that their blend to the midrange means a seamless transition.

Our ears are most sensitive, from around 100hz to around 8khz. The midrange, especially where crossovers tend to exist, around 2khz, is especially difficult to integrate well.

That's why the full range driver + woofer bookshelf I suggested above, I think will work surprisingly well. No, it won't have the top octave air of a speaker with a tweeter, but it will be great in the following respects:

Consistent dispersion pattern with no "off-axis bloom" from going from a near-beaming woofer to a virtually omni tweeter. the dispersion pattern will be a bit narrow in the higher octaves, so cross their axes just front of you to get a wide sweet spot.

Low crossover frequency around 300hz (ultimately would be decided with modeling n measuring) means we're less sensitive to its issues and this is already a bass region where the room is starting to be a big factor in what sounds we hear anyways.

No mid/tweeter crossover right near 2khz where our ears are most sensitive. You also save money compared to a 3-way, because you don't need to buy crossover components or a tweeter. 

I think if you build the speaker I suggest above, you'll be rather impressed :T

In fact, Given the acoustic rolloffs, sensitivity, and easy-to-work-with clean response of the Scanspeak 10F and the JBL 804, getting a good 2nd order acoustic crossover should only require minimal (albeit large) components! I think I've convinced MYSELF to make something like this. Use at least a steel LAMINATE core inductor, or preferably an air core. Have the JBL woofer handle baffle step compensation rather than a "true" 2-way crossover.


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## JCD (Apr 20, 2006)

Just a few quick thoughts...

I completely agree with GranteedEV about the ability to simply swap out an old driver with a completely new one. It can be done, but the chances of it sounding good without any further modifications is EXTREMELY low.
Some questions that would help me recommend a direction for you..

Understanding that money is tight, how much did you have to spend?
What tools do you have available?
What is your ultimate goal for the speakers? I.e., where are they going to be? Do you want clarity of sound over the ability to play loud? Is size a limiting factor?

JCD


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## sub_junkie (Apr 14, 2009)

GranteedEV said:


> I think if you build the speaker I suggest above, you'll be rather impressed :T
> 
> In fact, Given the acoustic rolloffs, sensitivity, and easy-to-work-with clean response of the Scanspeak 10F and the JBL 804, getting a good 2nd order acoustic crossover should only require minimal (albeit large) components! I think I've convinced MYSELF to make something like this. Use at least a steel LAMINATE core inductor, or preferably an air core. Have the JBL woofer handle baffle step compensation rather than a "true" 2-way crossover.


Wow, thanks for that reply. Very interesting stuff.
As for the speaker with no tweeter...I'd rather skimp on bass extension to be able to have excellent quality. I won a pair of wireless Aperion Audio Zona's, and I love the mid and high quality from them. If I could get my front speakers to match that, I'd be very happy. 



JCD said:


> Just a few quick thoughts...
> 
> I completely agree with GranteedEV about the ability to simply swap out an old driver with a completely new one. It can be done, but the chances of it sounding good without any further modifications is EXTREMELY low.
> Some questions that would help me recommend a direction for you..
> ...


Budget would probably be around $200 for now, sadly. 
For box building tools, I have a table saw, router, nail gun, pretty much everything. My uncle is a carpenter, and my grandpa built houses, they both have a vast amount of tools I'm able to use.
The front speakers right now are on top of my wall unit, 71" off the ground, but I have an area 13" wide, 22" deep (would be touching the wall though) and about 52". That height would barely put the tweeter above eye level at listening position
I would like it to be very clear, while maintaing some loudness to them. The loudest that I ever listen to music is -20 on my receiver, and the Bose start loosing some of their mids' quality there. The highs still remain fairly clear though. If possible, I would love to be able to have these speakers take some bass away from the sub, as it's getting quite the workout right now. Lol. Only problem is the sub is permanently crossed at 90hz with this receiver. Pre amp is my best friend  haha

EDIT : the distance between the two speakers if they were placed on the ground would be 43" from edge of box to edge of other box. 

Sent from my iPhone using HTShack


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## GranteedEV (Aug 8, 2010)

If you use a quality full range driver, like the scanspeak 10F i mentioned, you won't need a tweeter, and that's not a matter of just being cheap at all! The difference from adding a tweeter would be subtle at best. You really have to hear a well executed full range before you write them off. Tweeters introduce as many problems as they solve, so it's best not to write off the fidelity of any design based on your preconceptions :T

These ain't the weak wide range drivers you'll find in commercial speakers. I think i've read of some people using the 10Fs, as tweeters . If they lack anything, we're talking about some VERY minor ringing around 11khz where our ability to hear is limited at best and our sensitivity to any issues is VERY low. In fact, I don't even know if such an issue would be audible.

Here is Zaph's measurements of the 10F:
CSD:








The distortion plot is very clean as well:








The on and off axis response is also very controlled. Getting this kind of smooth off axis in the upper midrange and lower treble, is very difficult from a tweeter/midrange crossover... in fact that's almost ideal behavior all the way up to 10khz (which is essentially the upper limit of musical notes, everything higher is generally perceived as "air" or cymbal harmonics). I suspect it's got more controlled off axis response, than your Aperion speakers. The slightly rising on-axis response can probably be fixed with a tiny small inductor, or kept the way it is to augment the aformentioned air.










I think a two way with these drivers, would result in an extremely high fidelity speaker. Dispersion would be moderately narrow, which means the room would have less effect on what you're hearing, than the usual speaker. Some toe-in is necessary to make sure you're in the listening window, but past that I'm getting excited just thinking about this speaker...

The fact that it would have deep bass (and excellent midbass), I think would be just a ridiculously awesome bonus; not at all a choice compromising fidelity. If you do want to sacrifice some deep bass (and perhaps output) to save money though, the Dayton RS-225 way to go:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-356


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## sub_junkie (Apr 14, 2009)

GranteedEV said:


> If you use a quality full range driver, like the scanspeak 10F i mentioned, you won't need a tweeter, and that's not a matter of just being cheap at all! The difference from adding a tweeter would be subtle at best. You really have to hear a well executed full range before you write them off. Tweeters introduce as many problems as they solve, so it's best not to write off the fidelity of any design based on your preconceptions :T
> 
> These ain't the weak wide range drivers you'll find in commercial speakers. I think i've read of some people using the 10Fs, as tweeters . If they lack anything, we're talking about around 11khz where our ability to hear is limited at best and our sensitivity to any issues is VERY low.
> 
> ...


That does look really good :T
About how much would this kind of speaker cost ?

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## GranteedEV (Aug 8, 2010)

sub_junkie said:


> That does look really good :T
> About how much would this kind of speaker cost ?


JBL GTO 804 will be ~110/pr
Dayton RS 225-8 will be $88/pr 
scanspeak discovery 10F - $200/pr - this is a higher end, expensive driver.
the CSS full range drivers, would cost around $80/pr

I can't truly conclusively give you a truly accurate estimate on the crossover parts without at least modeling a mock crossover. You'd need to know how steep a slope, and what crossover frequency, is necessary, but I'm guessing

~60 to ~140 dollars. on air core inductors or ~30 to ~100 dollars if you go for laminate cores
~30 to ~120 bucks on capacitors

Plus the cost of wood/glue etc of course.


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## sub_junkie (Apr 14, 2009)

GranteedEV said:


> JBL GTO 804 will be ~110/pr
> Dayton RS 225-8 will be $88/pr
> scanspeak discovery 10F - $200/pr - this is a higher end, expensive driver.
> the CSS full range drivers, would cost around $80/pr
> ...


Wow, would all of those drivers be used, or a few of them?


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## GranteedEV (Aug 8, 2010)

sub_junkie said:


> Wow, would all of those drivers be used, or a few of them?


Sorry, I was giving you two choices between wide band drivers(the affordable and nice CSS EL70 and the more expensive, even nicer, Scanspeak 10F), and two choices between woofers(I'd get the JBL over the Dayton for the extra 30 bucks personally), to choose from...


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## sub_junkie (Apr 14, 2009)

GranteedEV said:


> Sorry, I was giving you two choices between wide band drivers(the affordable and nice CSS and the expensive Scanspeak), and two choices between woofers(I'd get the JBL over the Dayton for the extra 30 bucks personally), to choose from...


Ahh, ok. Thanks for the options though! I just wanted to make sure.
So I should go with the CSS and the JBL? Hopefully crossovers won't push this to be too expensive...what size of box should I expect to see with these? Ported, or sealed, and do you have an estimate on the cu.ft or external dimensions for them? Thanks for the help!


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## GranteedEV (Aug 8, 2010)

sub_junkie said:


> Ahh, ok. Thanks for the options though! I just wanted to make sure.
> So I should go with the CSS and the JBL? Hopefully crossovers won't push this to be too expensive...what size of box should I expect to see with these? Ported, or sealed, and do you have an estimate on the cu.ft or external dimensions for them? Thanks for the help!


The nice thing about the JBL is its natural rolloff - it's a healthy 3db down already by 360hz, so I suspect the cost of inductors will stay low. 

As for box tuning, it's tough to say, although this driver with qts = .42, is well suited to either alignment just like your maelstrom 

In a vented box, you can tune this to 22hz in 1.0 cu ft. It will be -3 by about 32hz and -6db by about ~19hz. This shallow rolloff should result in nice coupling to the room. 

For a sealed box, I'd put it in 0.7 cu ft. -3db point is 49hz, and it should still produce usable bass down to its -10db point of about 26hz. The nice thing about this is, that it will have an excellent ability to blend to a subwoofer, and there's no vent resonance or port noise to bother you.

Or you could make a stuffed, tapered transmission line for nice deep extension, and the same sound quality as the sealed, but this will probably be a large tower.

The main thing I recommend, is to offset the fullrange driver, to round over corners by 3/4" to 1" if possible, and to brace it well because main speakers excite panel resonances more in the 250-400hz region, and for the full range driver, to be in its own sealed internal enclosure rather than share the space.


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## sub_junkie (Apr 14, 2009)

GranteedEV said:


> The nice thing about the JBL is its natural rolloff - it's a healthy 3db down already by 360hz, so I suspect the cost of inductors will stay low.
> 
> As for box tuning, it's tough to say. In a vented box, you can tune this to 22hz in 1.0 cu ft. It will be -3 by about 32hz and -6db by about ~19hz. This shallow rolloff should result in nice coupling to the room.
> 
> ...


Wow, that sounds really good.

How large of a tower are we speaking of here ?


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## GranteedEV (Aug 8, 2010)

sub_junkie said:


> Wow, that sounds really good.
> 
> How large of a tower are we speaking of here ?


I am not sure. It would need to be modelled, and I'm actually at work right now :innocent:

But I'd guess, probably 36 to 42 inches tall, at least. Transmission lines are more about length, than about volume. Although with the right labynth and deep dimensions, you can make it shorter. You still want the full range to be at ear height, no matter what, so I like ~40" to 42" height because that normally puts the full range at ear height.

The main thing I have to say is, that it's best to design a crossover based on measurents IN a test enclosure, rather than infinite baffle simulations. So the plan of action would be, to build one test enclosure (or two, I guess), and measure the drivers' frequency response :in: the baffle. If you lack measurement equipment, I think the first thing to do, would be to find someone semi-locally, who can help you in this regard, to whom you can take the speakers for measurement... or you could just get measurement equipment yourself ;P :O


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## sub_junkie (Apr 14, 2009)

GranteedEV said:


> I am not sure. It would need to be modelled, and I'm actually at work right now :innocent:
> 
> But I'd guess, probably 36 to 42 inches tall, at least. Transmission lines are more about length, than about volume.
> 
> The main thing I have to say is, that it's best to design a crossover based on measurents IN a test enclosure, rather than infinite baffle simulations. So the plan of action would be, to build one test enclosure (or two, I guess), and measure the drivers' frequency response :in: the baffle. If you lack measurement equipment, I think the first thing to do, would be to find someone semi-locally, who can help you in this regard, to whom you can take the speakers for measurement... or you could just get measurement equipment yourself ;P :O


Ok. I'm fine with 42 inches tall.

I do not have measuring equipment, so I would have to find someone near me as you stated. If I'm going to build test enclosures, I would like for them to be the final ones, to save on wood costs, if that would be possible.


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## GranteedEV (Aug 8, 2010)

sub_junkie said:


> If I'm going to build test enclosures, I would like for them to be the final ones, to save on wood costs, if that would be possible.


Of course! lol!

But before you do anything like ordering, I want to run the driver combination through an expert, so wait for me to get back


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## sub_junkie (Apr 14, 2009)

GranteedEV said:


> Of course! lol!


What I mean by that also is like what's the benefit to build a test enclosure if it's probably the same design that you would use anyways? lol


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## GranteedEV (Aug 8, 2010)

sub_junkie said:


> What I mean by that also is like what's the benefit to build a test enclosure if it's probably the same design that you would use anyways? lol


heh, yeah.

That's one place where having a test enclosure that isn't the final enclosure, can prove really useful. Heavy towers are tough, but with bookshelves, you could mail the test box to someone far away, for measurements and crossover design.


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## sub_junkie (Apr 14, 2009)

GranteedEV said:


> heh, yeah.
> 
> That's one place where having a test enclosure that isn't the final enclosure, can prove really useful. Heavy towers are tough, but with bookshelves, you could mail the test box to someone far away, for measurements and crossover design.


Ahh, I see. It could be extremely handy in that situation. haha.
I hope making a crossover isn't too difficult; I haven't made one before :O


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## jackfish (Dec 27, 2006)

At the most I would replace the woofer foam surround and leave it at that. This task should bring it back to close to the original. You might be surprised how much bass a Bose 301 actually can produce with new foam surrounds.

http://wooferrepair.com/bose.html


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## sub_junkie (Apr 14, 2009)

jackfish said:


> At the most I would replace the woofer foam surround and leave it at that. This task should bring it back to close to the original. You might be surprised how much bass a Bose 301 actually can produce with new foam surrounds.
> 
> http://wooferrepair.com/bose.html


Thanks for that link. Surprisingly, the surrounds and speakers seem to be in perfect condition (the surrounds are still malleable, no cracks or splits, and are soft to the touch) and so do the boxes themselves, except for one corner on the left speaker. Part of the finish is peeling off, but they still look great.


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## jackfish (Dec 27, 2006)

If they have been sitting for twenty years, no matter what the surrounds look like, they have to be deteriorated. I'd replace them first, for $20 you won't be out much and you can see if it makes an improvement or not.


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## sub_junkie (Apr 14, 2009)

jackfish said:


> If they have been sitting for twenty years, no matter what the surrounds look like, they have to be deteriorated. I'd replace them first, for $20 you won't be out much and you can see if it makes an improvement or not.


That's true. What's a good way to tell if they are ? I'd rather not tear up these speakers if I don't have to haha. I don't have any others laying around that I could use for replacement fronts


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## jackfish (Dec 27, 2006)

Take your thumb and index finger and pinch a substantial portion of the rounded foam surround. This will not harm a healthy surround which will bounce back when released but will cause a deteriorated surround to tear or crumble.


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## sub_junkie (Apr 14, 2009)

jackfish said:


> Take your thumb and index finger and pinch a substantial portion of the rounded foam surround. This will not harm a healthy surround which will bounce back when released but will cause a deteriorated surround to tear or crumble.


The surround is fine when I pinch it like you said to do. I tried it on many different parts of the surround, and all were fine.


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## Mauritzvw (Sep 19, 2010)

Would love to see the outcome of this. I like the idea of a full range coupled to a woofer. Been thinking about the Dayton RS225-8 and the Dayton RS100-8


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## isaeagle4031 (Feb 5, 2011)

I've got a pair of these sitting in my shop. Everything is in good working order, but the sound is compared to other stuff I have heard and have. I paid almost nothing for them. There is really no actual crossover in these things. A simple cap for the 2 tweets and the woofer running full-range. If I were to reuse the cabinets, I would consider using something along the lines of the Dayton aluminums and a TB 2" full-range with a cup behind the 2". The cabinets def need some attention in the form of bracing and sealing around the port. 

Really the biggest issue for me is that the cabinet shape is a pain. Not really big enough for an 8" driver, but adapting it to a 6" would be a real pain. Plus its horizontal orientation can make crossover design a real fight in trying to deal with all of its issues.


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