2x12" bass guitar cabinet

[boneless]

hi everyone,

I'm about to embark on a diy construction of a bass guitar cabinet. it's going to be a 2x12" vented cabinet with a tweeter.

now, I've chosen the following speakers:

18sound 12W500

(site seems to be down at the moment, you can see the specs anyway here)

or maybe a pair of these:

FaitalPro 12PR300
Monacor SP12-200PA

although I'm more sold towards the 18sound drivers, as they seem to have better efficiency, the FaitalPro look nice, with a decent xmax and a flat response, but I'm actually after a "bright", voiced response, and the 2k peak in the response seems to be similar to what I actually try to dial in on my amp. the monacor drivers seem nice as well, with a touch more bass (at least, on the simulations) compared to the 18sound drivers. I'm quite undecided between the two, actually.

and no, please, no eminence drivers, it's kind of a requirement for my project, since SO MANY cab manufacturers use eminence drivers, and I'm actually looking for something that may be maybe a bit different

cabinet size, I'm thinking at 120 L @ 45Hz tuning frequency, as it seems a good compromise for all the drivers I've been considering (actually, the cabinet will be quite large, but it's not a big deal). the cone excursion actually exceeds xmax at 350W, but considering I won't be using the cabinet to output sine waves, but bass guitar, I think I'm quite safe (as a rule of thumb, I'm considering the average excursion of the first 4 harmonics of a given note, namely the low E @ 41Hz, and trying to keep this average value under xmax, but then again, I'm not after perfect linearity, and actually I like speaker break-up, many bass players overdrive their speakers far beyond their xmax as a choice)

do you think it's a sensible project? or are there areas for improvement? obviously the cabinet will be braced and I'll put foam on the sides (most projects I've seen avoid putting much foam in vented cabinets, opting for padding just the sides or the rear panel). regarding foam, is it true that it "artificially" increases speaker volume by about 20% (meaning that, in practice, a 120 L simulated cab will have to be 25 L smaller)?

as a last question, I was thinking of installing a fabric dome tweeter, but most fabric dome tweeters seem to have low sensibility (around 93-94dB SPL), are there any fabric dome tweeters around with a higher efficiency?

thanks

[leadbelly]

My 2 cents: you seem to be thinking about it as a sub + tweeter project. A bass cabinet is most definitely not a sub. You need a LOT more clean upper end, and it doesn't need to go as low as a sub. Also, you point out that commercial cabs use Eminence drivers, but fail to mention that they use Emininence bass guitar drivers, not just PA drivers as you are looking for. If you want something different, that's fine, but be prepared for disappointment if you haven't thought of this yet and taken it into account. Also, you haven't given details on the tweeter and crossover, so it's hard to comment on the whole picture.

[tinitus]

Just remember that the Xmax of the Faital is P-P
In your sim it will be half of that

btw, theres a couple of Beyma SM series 12" with quite good Xmax(+/-), and cheap

My choise will still be PrecisionDevices PDN.15BR40, +/-8mm Xmax, and a cheap compression driver
previous plan was to mate it with PDN.12MH25
but it gets complicated, and expencive

[boneless]

Originally Posted by leadbelly

My 2 cents: you seem to be thinking about it as a sub + tweeter project. A bass cabinet is most definitely not a sub. You need a LOT more clean upper end, and it doesn't need to go as low as a sub. Also, you point out that commercial cabs use Eminence drivers, but fail to mention that they use Emininence bass guitar drivers, not just PA drivers as you are looking for. If you want something different, that's fine, but be prepared for disappointment if you haven't thought of this yet and taken it into account. Also, you haven't given details on the tweeter and crossover, so it's hard to comment on the whole picture.

actually, I'm actually trying to AVOID a sub+tweeter cabinet. I've specifically chosen a pair of 12" drivers that are more suited for a PA top, not subwoofers, since bass drivers are more similar to mid-woofers than to subwoofers. the 18sound drivers have an adequate xmax of 4mm (keep in mind that many cabs mount drivers with a much lower xmax, OTOH the Eminence Delta 12's xmax is only 2.5mm, and it's a driver that many DIYers use in their cabinets), but at the same time the predicted response is quite "bass-shy" (compared to a sub, at least), since the f3 is around 65Hz, moreover, the frequency response of the drivers reaches 3-4K with ease. in fact, the 12W500 look very similar (to me, at least) to the Eminence Delta 12s, but with a greater xmax.

I'm going to center the crossover frequency for the tweeter at around 3.5KHz, I'm not sure about the slope, maybe 12dB/octave is enough?

Just remember that the Xmax of the Faital is P-P
In your sim it will be half of that

are you sure? it doesn't seem peak-to-peak to me

[kenpeter]

Yeah, there are more efficient domes, called compression drivers...
Slightly more helpful answer, even though not dome in any way:
http://www.parts-express.com/pe/show...number=264-360
Much bigger than looks in the picture, at least size of a softball.

If you got money to throw at it...
http://www.usspeaker.com/beyma%20tpl150-1.htm

I suggest you drop the 2x12 plan, get you an Emenince DeltaPro 15.
http://www.parts-express.com/pe/show...number=290-512
If there's any other model or off-brand that bright? I've not found any.
In Karlson K15 cabinet (plans 1955 Radio Electronics) will destroy all.
Ask Freddi if you need build details. BK115 might be smaller option.

Pair of 12's costs more, weighs more, all other factors being similar.

[tinitus]

Originally Posted by boneless

are you sure? it doesn't seem peak-to-peak to me

FaitalPRO - Neodymium Professional Drivers

look in electrical specifications
winding depth 12.5mm
magnetic gap depth 8mm

thats 4-5mm P-P Xmax
and equals 2-3mm +/- Xmax

[leadbelly]

Originally Posted by boneless

actually, I'm actually trying to AVOID a sub+tweeter cabinet. I've specifically chosen a pair of 12" drivers that are more suited for a PA top, not subwoofers, since bass drivers are more similar to mid-woofers than to subwoofers. the 18sound drivers have an adequate xmax of 4mm (keep in mind that many cabs mount drivers with a much lower xmax, OTOH the Eminence Delta 12's xmax is only 2.5mm, and it's a driver that many DIYers use in their cabinets), but at the same time the predicted response is quite "bass-shy" (compared to a sub, at least), since the f3 is around 65Hz, moreover, the frequency response of the drivers reaches 3-4K with ease. in fact, the 12W500 look very similar (to me, at least) to the Eminence Delta 12s, but with a greater xmax.

I'm going to center the crossover frequency for the tweeter at around 3.5KHz, I'm not sure about the slope, maybe 12dB/octave is enough?

Well, you've thought this out, that's good You have some other comments to think about too, so I guess the only thing I would add is forget the dome tweeter, that's just begging for problems, I would go with even a piezo before that, and I would cross over higher than 3.5 KHz for sure, especially if you're only planning a HP and no LP.

[boneless]

I was looking for a fabric dome tweeter as I've never had the chance to use one and I've been told they have a very pleasant, natural and "soft" response, compared to compression drivers which can sound harsh, keep in mind I'm going to use lots of distortion and effects through the tweeter as well. I was looking at a Ciare PT383: CIARE - Produzione speakers, woofer, tweeter, driver e car audio (you can find it under "tweeter"), I've read great things about it.

as for the single 15" instead of the double 12"s, I'm actually after a 2x12" configuration. yes, I know that from a "hi-fi" point of view, there's nothing to gain and much to lose from a double 12 inch speaker, but I actually like the response of the 12" drivers, punchy yet warm, on bass guitar. considering that there are very few 12" cabinets for bass, and they're all expensive, I decided to fill this void on my own

anyway, any recommendation for a tweeter? I'd prefer to stay among european products.

[kenpeter]

Not from hi-fi standpoint. I play bass.

I like domes, but none loud enough for what you want to do with it.
From a dispersion standpoint, slot tweeter is the next best thing.
And slot tweeter is better match for your power and efficiency.

I like DeltaPro12 and own many, extremely similar spec to what you
want to use. I tell you to use DeltaPro15, cause it weighs less than
2x12, and better mate with Karlson enclosure.

Why Karlson? Cause you say dome, and that implies even dispersion.
Both the 12" you specify, and the 15" I would suggest, have rising
response and beaming polar pattern. Terrible direct radiator match
to dome or slot tweeter. But Karson is an indirect radiator, and will
disperse from its front slot much more similar to tweeter you want.
Not so much worry where you and/or mic stand on or off axis...

Anyways, much easier to fit 15 in Karlson than 2x12, I've tried...

There is no neodymium with bandwidth of DeltaPro15, else I'd go
something Neo. Unfortunately they all seem to chose the next
bigger 3" coil former... Heavier coil isn't helping this application...

And let me repeat it again:
Why Karlson? Cause you say dome, and that implies even dispersion.

European Mfg, maybe Celestion offers something like DeltaPro15?
They tend toward the bright MI side, good in this circumstance.
Beyma also makes a slot tweeter (they are both copies of JBL), but
more expensive than Selenium (metal vs plastic), and crosses higher.
http://www.usspeaker.com/beyma%20CP21F-1.htm

How bout BN15-300S? Thats neo with the smaller 2.5" voice coil!
http://professional.celestion.com/bass/orange/index.asp

[tinitus]

Originally Posted by boneless

anyway, any recommendation for a tweeter? I'd prefer to stay among european products.

Beyma actually makes a 100db hornloaded dome tweeter

http://www.beyma.de/fileadmin/seiten...MC2012N_1_.pdf

and monacor/stageline have a couple of cheap options

MONACOR INTERNATIONAL:Pagina con particolari dei prodotti


anyway, I thought a "harsh/rough" tweeter would be of no concern with bass guitar, would it