13cm Subwoofers

[Simon Dean]

Ok,

You can call me crazy

<crazy space>

I am DIYetically challenged. I couldn't fit any great big subwoofer
stuff to my car - I wouldn't know how to chisel the bits out of my car
and make the necessary custom brackets to ensure a nice finish and yet
still leave room for my shopping in the boot/trunk.

I just want a nice sensible solution and have drop in replacements,
because, well, my, well my fiber-glass-mould-making skills are none
existing.

If you think 4x6 inch speeakers in the front is bad, 5.25 inch speakers
in the back just leaves you with no room for manoeuveure.

Few questions if I may?

1) My right rear speakers keep blowing! Any ideas why?
All my speakers are JBL, and while I setup the amp my self (JBL 75.4), I
only have a problem with the right rear.

I wouldn't mind, but the rears are technically capable of more RMS
wattage than the fronts.

2) The sound from the rear even with working speakers is atrocious. Is
this because the front speakers are door mounted and resonate more? The
rear speakers are mounted in this flimsy metal trays. What can be done
to improve the sound? I keep hearing about dynamat? Incidentally,
they're all full range speakers.

3) This brings me onto... Is it possible to get 5.25inch or 13cm
subwoofers, something more boomy. No, it seems everything is full range
speakers. I just want something a little meatier to give a bit more bass.

Snip the wire to the enclosed tweeter?

Ta
Simon

[KU40]

are you using a high pass crossover on the amp for the speakers?

try tangband, they make some small yet good subs.


--
KU40

[Simon Dean]

KU40 wrote:
> are you using a high pass crossover on the amp for the speakers?
>
> try tangband, they make some small yet good subs.
>
>

Ugh?

Sure why not.

Im using a crossover on the amp with a statistical markup resoluting
rj45 wan to the lan miniport adapter with male scsi interface socket...

:-)

High pass crossover?

In basic terms, that's the thing that cuts out high frequencies? I
believe my amp does have that feature in place. I'd have to check the
docs...

Will try tangband though.

Cheers
Simon

[Matt Ion]

Simon Dean wrote:
> Ok,
>
> You can call me crazy

Okay... YOU'RE CRAZY, SIMON!

> I am DIYetically challenged. I couldn't fit any great big subwoofer
> stuff to my car - I wouldn't know how to chisel the bits out of my car
> and make the necessary custom brackets to ensure a nice finish and yet
> still leave room for my shopping in the boot/trunk.
>
> I just want a nice sensible solution and have drop in replacements,
> because, well, my, well my fiber-glass-mould-making skills are none
> existing.

There are some things where you may actually need to bring in professional help.
It's alright to do that, we won't think any less of you!

> If you think 4x6 inch speeakers in the front is bad, 5.25 inch speakers
> in the back just leaves you with no room for manoeuveure.
>
> Few questions if I may?

You may...

> 1) My right rear speakers keep blowing! Any ideas why?
> All my speakers are JBL, and while I setup the amp my self (JBL 75.4), I
> only have a problem with the right rear.

Are they screwing down flat? If the surface they're mounting to is uneven, and
you're cranking the speaker down tight against it, you could be warping the
basket, causing the voicecoil to go off-center in the gap. That's about the
only thing I can think of that would cause a single speaker to keep dying.

There's also an outside chance that the one channel of the amp is bad; you could
test this by switching the two rear speakers on the amp (and then swap their
inputs to maintain proper left/right setup), and see if the left-rear blows instead.

> I wouldn't mind, but the rears are technically capable of more RMS
> wattage than the fronts.

So... put some lower-wattage speakers in the back, and then you won't mind :)

See, there's an easy fix for everything!

> 2) The sound from the rear even with working speakers is atrocious. Is
> this because the front speakers are door mounted and resonate more? The
> rear speakers are mounted in this flimsy metal trays. What can be done
> to improve the sound? I keep hearing about dynamat? Incidentally,
> they're all full range speakers.

Full-range... as in, single-cone? No coaxial tweeter? If you have no tweeters,
there's part of your sound problem.

Flimsy baffles will mostly affect bottom end, as in, lack of it. Dynamat will
help, if you cover the rear deck with it. You also need to make sure there's no
"leakage" between the top and bottom of the deck - the lower the frequency, the
less "directional" the sound waves become, and bass frequencies from the back of
the cone will simply "loop back" and cancel out those from the front. If you
Dynamat the rear deck, do ALL of it, and make sure you have a flat area to screw
the speaker frame to so it seals all the way around.

> 3) This brings me onto... Is it possible to get 5.25inch or 13cm
> subwoofers, something more boomy. No, it seems everything is full range
> speakers. I just want something a little meatier to give a bit more bass.
>
> Snip the wire to the enclosed tweeter?

All that will do is get right of the high end; it won't improve the bottom end
at all. It's really simply a matter of physics: the more bass you want, the
more air you need to move, and the smaller the cone, the less air it can push.
You might be able to get something with a little more excursion (in-out movement
distance), which will help a little, but there's only so much a structure that
small will take.

You might be able to step up to 6" speakers by creating a solid wood panel that
fits under the entire rear deck, then cut out 6" holes under the existing
speaker holes in the deck, and mount the speakers from behind the board (use at
least 1/2" material, preferably 3/4", and MDF is preferable over plywood).

Or you could have someone build you a small sub box - I've seen some pretty tiny
ones using a pair of 8" subs in an isobaric configuration - and tuck it away a
corner of the trunk.

What kind of car is this, anyway?

[Matt Ion]

Simon Dean wrote:

> Im using a crossover on the amp with a statistical markup resoluting
> rj45 wan to the lan miniport adapter with male scsi interface socket...

Ahh, an IT geek :)

> High pass crossover?
>
> In basic terms, that's the thing that cuts out high frequencies?

Nope... as the name suggests, a high-pass crossover PASSES the highs and blocks
the lows.

> believe my amp does have that feature in place. I'd have to check the
> docs...

Your amp should have a variable crossover and bass boost. First, DON'T use the
bass boost, it's just gonna kill your speakers that aren't designed to produce a
lot of bass. Check the crossover settings - you probably don't want anything
below 60Hz getting to any of those speakers. It may not kill them outright, but
it will surely sound like crap.

You could try setting the high-pass to 60Hz, then bringing up the bass boost a
bit, to increase lows above 60... but do this carefully, as again, it will be
easy to drive them into the "crap" region.

[Simon Dean]

Matt Ion wrote:
> Simon Dean wrote:
>> Ok,
>>
>> You can call me crazy
>
> Okay... YOU'RE CRAZY, SIMON!


> What kind of car is this, anyway?

We're talking Nissan Primera 1994, Im in the UK, hence I think the
closest match is something like a Infinity g20 or something.

It's hatchback, so there's no rear deck as such, just a parcel shelf
that lifts up when I open the "trunk" and literally two six inch at best
wide metal plates that screw into the car which has the plastic trim
over the top and the parcel shelf sits on that.

Trying to remould quite substantial bits of my car, isn't really
something I want to look at with this car.

Sooo....



>> If you think 4x6 inch speeakers in the front is bad, 5.25 inch
>> speakers in the back just leaves you with no room for manoeuveure.
>>
>> Few questions if I may?
>
> You may...
>
>> 1) My right rear speakers keep blowing! Any ideas why?
>> All my speakers are JBL, and while I setup the amp my self (JBL 75.4),
>> I only have a problem with the right rear.
>
> Are they screwing down flat? If the surface they're mounting to is
> uneven, and you're cranking the speaker down tight against it, you could
> be warping the basket, causing the voicecoil to go off-center in the
> gap. That's about the only thing I can think of that would cause a
> single speaker to keep dying.

Yeah. They're flat... Im pretty sure the voice coil is as central as it
can be.

>
> There's also an outside chance that the one channel of the amp is bad;
> you could test this by switching the two rear speakers on the amp (and
> then swap their inputs to maintain proper left/right setup), and see if
> the left-rear blows instead.

Worth a try. To be fair, when I said it "keeps" blowing, I mean it is
the only one that blows, and I've replaced it about 3 or 4 times over
the past couple of years.


>> 2) The sound from the rear even with working speakers is atrocious. Is
>> this because the front speakers are door mounted and resonate more?
>> The rear speakers are mounted in this flimsy metal trays. What can be
>> done to improve the sound? I keep hearing about dynamat? Incidentally,
>> they're all full range speakers.
>
> Full-range... as in, single-cone? No coaxial tweeter? If you have no
> tweeters, there's part of your sound problem.

Well what do we really have then... two tweeters in the A-Posts (by the
windshield), and the rest of my four JBL speakers each are advertised as
"full range", this means though that it's a woofer cone and coaxial tweeter.

Six tweeters all round. The sound is a bit bright at times.

> Flimsy baffles will mostly affect bottom end, as in, lack of it.
> Dynamat will help, if you cover the rear deck with it.

Got no rear deck.... as I say just two tiny cramped little pods that you
can barely fit a 5.25" speaker into - barely as in little height and
little width.


> You also need to
> make sure there's no "leakage" between the top and bottom of the deck -
> the lower the frequency, the less "directional" the sound waves become,
> and bass frequencies from the back of the cone will simply "loop back"
> and cancel out those from the front.

That could actually be the problem. There's a gap around the speaker...

so er, stick some dynamat in there and get rid of the gap? Or should I
with this 10x10 inch sheet I ordered, somehow try and stick it round the
back of the speaker, folding it over on top and screwing down with the
speaker?

From what I think you were saying, you need a bit of air to drive the
speakers? So, just get rid of the gaps and things should be better?

I mean, I don't want to be encasing the speaker in a bag, just sealing
the gaps around the outside of the speaker frame and the mounting plate
by using some dynamit and maybe some, silicone sealant or something?


> If you Dynamat the rear deck, do
> ALL of it, and make sure you have a flat area to screw the speaker frame
> to so it seals all the way around.
>
>> 3) This brings me onto... Is it possible to get 5.25inch or 13cm
>> subwoofers, something more boomy. No, it seems everything is full
>> range speakers. I just want something a little meatier to give a bit
>> more bass.
>>
>> Snip the wire to the enclosed tweeter?
>
> All that will do is get right of the high end; it won't improve the
> bottom end at all. It's really simply a matter of physics: the more
> bass you want, the more air you need to move,

So no to enclosing the speaker in a bag made from dynamat with the top
exposed?

> and the smaller the cone,
> the less air it can push. You might be able to get something with a
> little more excursion (in-out movement distance), which will help a
> little, but there's only so much a structure that small will take.
>
> You might be able to step up to 6" speakers by creating a solid wood
> panel that fits under the entire rear deck,

Yeah, no deck to mount any wood panels to.


Thanks for the thoughts.

Simon

[KU40]

So I guess I should have asked in my first post- Are the speakers
blowing thermally or mechanically? As in.....are the voice coils
melting and freezing the cone, or is it overexcurting and ripping glue
joints or jumping the voice coil out of the gap?

Try switching the outputs for the speakers on the amp from the left to
the right side and vice-versa. If the left speaker blows, then you
know it's a problem with the amp or anything before it in the signal
chain. My bet would be on the amp at that point. But if the right
speaker blows, it's a problem with the speaker or its environment.

Granted we'd like to nail the problem before another speaker blows, but
just in the meantime......


--
KU40

[Matt Ion]

Simon Dean wrote:
> Matt Ion wrote:
>
>> Simon Dean wrote:
>>
>>> Ok,
>>>
>>> You can call me crazy
>>
>>
>> Okay... YOU'RE CRAZY, SIMON!
>
>
>
> > What kind of car is this, anyway?
>
> We're talking Nissan Primera 1994, Im in the UK, hence I think the
> closest match is something like a Infinity g20 or something.
>
> It's hatchback, so there's no rear deck as such, just a parcel shelf
> that lifts up when I open the "trunk" and literally two six inch at best
> wide metal plates that screw into the car which has the plastic trim
> over the top and the parcel shelf sits on that.

Sounds not unlike the rear speaker locations in my '87 Accord hatchback. In
that instance, I put 6.5" Quart woofers (from a 2-way separates set) in the
rings, and built up the space under them with stick-on weatherstrip foam to seal
them to the plastic underneath. It's not the best seal, but it works alright.
I have a 10" JL sub in a box in the spare tirewell, though, so I don't need a
lot of bass out of the Quarts.

> Worth a try. To be fair, when I said it "keeps" blowing, I mean it is
> the only one that blows, and I've replaced it about 3 or 4 times over
> the past couple of years.

Yeah, I understood that :)

>> Full-range... as in, single-cone? No coaxial tweeter? If you have no
>> tweeters, there's part of your sound problem.
>
>
> Well what do we really have then... two tweeters in the A-Posts (by the
> windshield), and the rest of my four JBL speakers each are advertised as
> "full range", this means though that it's a woofer cone and coaxial
> tweeter.
>
> Six tweeters all round. The sound is a bit bright at times.

Yeah, it would be :)

>> Flimsy baffles will mostly affect bottom end, as in, lack of it.
>> Dynamat will help, if you cover the rear deck with it.
>
>
> Got no rear deck.... as I say just two tiny cramped little pods that you
> can barely fit a 5.25" speaker into - barely as in little height and
> little width.

Okay...

>> You also need to make sure there's no "leakage" between the top and
>> bottom of the deck - the lower the frequency, the less "directional"
>> the sound waves become, and bass frequencies from the back of the cone
>> will simply "loop back" and cancel out those from the front.
>
>
> That could actually be the problem. There's a gap around the speaker...
>
> so er, stick some dynamat in there and get rid of the gap? Or should I
> with this 10x10 inch sheet I ordered, somehow try and stick it round the
> back of the speaker, folding it over on top and screwing down with the
> speaker?

Hmmm... hard to say without seeing the actual layout of these things. Maybe I
can find some pics online...

Dynamat is intended to reduce the resonance of large areas of metal, more than
actually blocking the sound. You need something solid to fill the space.

> From what I think you were saying, you need a bit of air to drive the
> speakers? So, just get rid of the gaps and things should be better?

Speakers don't require "air to drive them". They generate sound waves from both
sides - when the cone moves out, it pushes a pressure wave forward, while the
back of cone creates a lower pressure area, and vice-versa when the cone moves
inward. Without something to keep the front and back of the cone separated,
those alternating pressure zones can cancel each other out. The effect is more
pronounced the lower the frequency goes, which is why you lose more bass than
you do mids.

> I mean, I don't want to be encasing the speaker in a bag, just sealing
> the gaps around the outside of the speaker frame and the mounting plate
> by using some dynamit and maybe some, silicone sealant or something?

Silicone might work, for a small gap. A bag won't, because it moves with the
air, and just "transmits" the sound waves right through. Your baffle - the
surface that separates the front and rear of the speaker - needs to be as solid
and inflexible as possible. It doesn't necessarily have to be a flat plane that
the speaker mounts through, like a board - a tube the same diameter as the
speaker performs the same function (although there are then other issue to
consider - again, its walls would need to be somewhat thick and inflexible to
prevent simply transmitting the sound). The critical thing is that the
low-frequency waves are isolated from one side of the cone to the other.

>>> Snip the wire to the enclosed tweeter?
>>
>>
>> All that will do is get right of the high end; it won't improve the
>> bottom end at all. It's really simply a matter of physics: the more
>> bass you want, the more air you need to move,
>
>
> So no to enclosing the speaker in a bag made from dynamat with the top
> exposed?

Not so much. Dynamat won't block sound. All it does is increase the mass of
whatever surface you attach it do, reducing its resonance and thus its tendency
to vibrate and transmit the sound.

Ideally, what you really want is a small sub, since you're really not going to
get much bass out of 5.25" drivers no matter what you do. There are a number of
pre-built designs (often called "truck boxes") that would tuck neatly to one
side of the hatch area, or you could have a local shop custom-build something to
be unobtrusive. One or two 8" subs won't take up too much space, and will round
out your bass nicely. You're not building a boom car, so you don't need
anything bigger than that, really.

Actually, my first car was a 1980 Mazda GLC hatchback - I built a sub enclosure
by bolting down a plate of 3/4" MDF over the spare tire well, and put two 8"
Orion subs in it. Wire grilles to protect the drivers, flip the carpet down
over it, and you'd never know they're there... until I turned it up and shook
the car. Great bottom end, no loss of cargo space. Rear speakers were 5.25"
Kicker woofers in the side panels, fronts were 6.5" Alpine 3-ways in custom
solid-wood door panels. All in all, a pretty decent-sounding setup.