12" Driver recommendation, please

[4 Strings]

I have a little Portabass 112 which needs a beefier driver. The speaker in it is not the original but works well, bit sensitive to signal (needs a good strong one with plenty of bass in it to get an deep tone, which can go nice and deep).

However, I'd like to use it for rehearsal for a particular band but it needs a bit more volume without breaking up.

Can anyone recommend a 12" that's not going to cost me too much which is going to punch out a good volume with plenty of depth that I can use as a substitute.

The cabinet is around 13cu in (ie about 14 x 14 x 12) with a 3" port - don't know the tube length, could measure it if necessary - in place of the tweeter.

I've been looking at the Celestion BN12 300X or the BL12 200 (bit heavier) and the LOOK suitable but I'll never know what they sound like unless I buy one and put it in. Fane Sovereign looks good too.

Any ideas?

[Lozz196]

Fairly sure my Marshall VBC 412 has Celestions in - don`t know which mind you - but they are very beefy indeed. I read a review somewhere re someone changing their speakers in a Laney cab over to Celestions and being blown away by the improvement. Celestion are also quite good at offering advice re their products, so may be worth an enquiry direct to them. At least you`ll find out which of their products they advise will suit your requirements better.

[Bill Fitzmaurice]

[quote name='4 Strings' post='1030142' date='Nov 20 2010, 03:53 AM']The cabinet is around 13cu in (ie about 14 x 14 x 12)[/quote]
That comes down to about 1 cu ft net, and no driver is going to give [i]"plenty of bass in it to get an deep tone, which can go nice and deep"[/i] from a box that small. IMO it's not worth replacing the driver, put the money in a better/larger cab, used if $ is an issue.

Edited November 20, 2010 by Bill Fitzmaurice

[LawrenceH]

[quote name='Bill Fitzmaurice' post='1030477' date='Nov 20 2010, 02:54 PM']That comes down to about 1 cu ft net, and no driver is going to give [i]"plenty of bass in it to get an deep tone, which can go nice and deep"[/i] from a box that small. IMO it's not worth replacing the driver, put the money in a better/larger cab, used if $ is an issue.[/quote]

This is true, but the OP is talking about the tone they already get being nice and deep if they put enough power in, so presumably they're satisfied but the problem is break-up. It really depends what the original driver is, whether it's worth replacing or not. Is it possible to find out?

[stevie]

[quote name='LawrenceH' post='1030495' date='Nov 20 2010, 03:10 PM']It really depends what the original driver is, whether it's worth replacing or not. Is it possible to find out?[/quote]
4 Strings says it's not the original - so he is likely to know. I'm also wondering if it's a 4-ohm driver.

[icastle]

[quote name='4 Strings' post='1030142' date='Nov 20 2010, 08:53 AM']I have a little Portabass 112 which needs a beefier driver. The speaker in it is not the original but works well, bit sensitive to signal (needs a good strong one with plenty of bass in it to get an deep tone, which can go nice and deep).

However, I'd like to use it for rehearsal for a particular band but it needs a bit more volume without breaking up.

Can anyone recommend a 12" that's not going to cost me too much which is going to punch out a good volume with plenty of depth that I can use as a substitute.

The cabinet is around 13cu in (ie about 14 x 14 x 12) with a 3" port - don't know the tube length, could measure it if necessary - in place of the tweeter.

I've been looking at the Celestion BN12 300X or the BL12 200 (bit heavier) and the LOOK suitable but I'll never know what they sound like unless I buy one and put it in. Fane Sovereign looks good too.

Any ideas?[/quote]

Couple of things spring to mind here.

In a tuned cabinet, which this is, the cabinet dimensions, port size and pipe length were all selected to match the original driver.
You can probably get away with just swapping drivers in bigger cabinets but in a cabinet this small the margins are going to be so much tighter.
The dimensions (volume of airspace used up by the cone and magnet etc.) of the driver are taken into account in the cabinet design so just sticking something else in there may cause problems.

If the speaker isn't the original then I'd be more inclined to go and find an original driver to replace it with - thats the only way you're going to get the whole thing back to the original spec and give it a chance to perform in the way that the manufacturer intended.

If you do decide to swap the driver then a BL12 200X is no good - the amp is rated at 300W into 8Ω and you need a speaker that can match this.

[Musky]

[quote name='icastle' post='1030631' date='Nov 20 2010, 05:23 PM']Couple of things spring to mind here.

In a tuned cabinet, which this is, the cabinet dimensions, port size and pipe length were all selected to match the original driver.
You can probably get away with just swapping drivers in bigger cabinets but in a cabinet this small the margins are going to be so much tighter.
The dimensions (volume of airspace used up by the cone and magnet etc.) of the driver are taken into account in the cabinet design so just sticking something else in there may cause problems.

If the speaker isn't the original then I'd be more inclined to go and find an original driver to replace it with - thats the only way you're going to get the whole thing back to the original spec and give it a chance to perform in the way that the manufacturer intended.

If you do decide to swap the driver then a BL12 200X is no good - the amp is rated at 300W into 8Ω and you need a speaker that can match this.[/quote]
By the sound of things the cabinet wasn't originally ported.

[quote]The cabinet is around 13cu in (ie about 14 x 14 x 12) with a 3" port - don't know the tube length, could measure it if necessary - [b]in place of the tweeter[/b].[/quote]

[icastle]

[quote name='Musky' post='1030945' date='Nov 20 2010, 10:42 PM']By the sound of things the cabinet wasn't originally ported.[/quote]

I misinterpreted what I read there and it just gets worse.

So, if I've interpreted it correctly this time:
Instead of the correct driver and a HF unit, it now has an incorrect driver, a hole where the HF unit used to be and a length of tubing in it's place that may or may not be the correct length to allow for volume displacement changes inside the cab which was originally a sealed unit anyway...

My advice to the OP would be: put everything back the way it was when it left the Ampeg factory - at best it may start to perform the way you want it to, at worst you'll get the market value for it if you decide to sell it on and buy something different.

[4 Strings]

Thanks everyone, just to clear up a few things;

No its not the original driver, nor is the port original.

Yes it sounds fine, (of course not big and deep like a bigger cabinet, but then its a little 1x12) but breaks up a bit too early.

I'm not too phased by whether its 200 or 300W rated as the amp is 350W anyway but won't be turned up too much (my very regular cab is a 200W 2x10 which, bless it, never complains even for very noisy gigs).

Just looking for a suitable upgrade in driver and wondered if there was any experience in suitable .

Turns out the current driver is a Beyma K-200, not familiar with it myself. Has a huge magnet but no impedance marked.

Thanks again

Edited November 21, 2010 by 4 Strings

[stevie]

I've checked out the Beyma. It's a nice driver. A bit old but good quality. You're not really going to get anything better from Celestion of Fane.

However, unless it's faulty, the driver is not your problem. It models OK in your cab - up to its power rating it is comparable with the JBL 2026, which is known to work well in a small box. There is not a lot of low bass, but power handling is good and you can always eq. It is likely to give you lots of slam.

From the information you have supplied, my guess is that your port is causing the problem. IMO, what you are describing as breakup is actually your port overloading because it is not big enough. You can check for this by putting your ear up to the port and playing a bottom E at high power. You will hear 'chuffing' / wind noise coming from the port. A 3-inch port is not much use in a cab this size because port overload will happen quite early on. The alternative is to increase the size of your port. If you can increase it to 4in diameter (or add a second 3in port), it should help with the problem. Unfortunately, doing this increases the port length to 300mm, which is quite substantial. It will probably need a bend, and will rob you of some of your cab volume.

This is a constant problem with small, high power cabs.

Edited November 21, 2010 by stevie

[Bill Fitzmaurice]

[quote name='4 Strings' post='1031039' date='Nov 20 2010, 07:11 PM']Turns out the current driver is a Beyma K-200, not familiar with it myself. Has a huge magnet but no impedance marked.[/quote]
The 12K200 is a premium driver. There's nothing wrong that putting it into a well designed and built cab wouldn't cure.

[4 Strings]

Thanks again everyone, interesting thoughts about port chuff. There is certainly plenty of air coming out that tube. I'll have a listen tomorrow (bit late now!). I'm certainly not putting 200W through it so it but it is a bassy signal to compensate for the cab size.

I read somewhere about the K-200 having a low Qts reduces its bass response. I don't know what that is.

I'd be grateful not to have to buy a new driver (but would still like to know any experience with the Celestion BN12 300X)

Its a great little cab, nicely made and I'd be prepared to accept its well designed.

I read here: [url="http://db.audioasylum.com/cgi/m.mpl?forum=hug&n=42234&highlight=jdruley"]http://db.audioasylum.com/cgi/m.mpl?forum=...ghlight=jdruley[/url] that someone had worked out a 4" dia tube around 3" long. I have no idea about ports, would I need one a foot long?

[stevie]

[quote name='4 Strings' post='1032011' date='Nov 21 2010, 10:35 PM']I have no idea about ports, would I need one a foot long?[/quote]
3in will tune much too high in your cab. You could get away with one that is 200mm long, but any longer is a bonus.

Edited November 21, 2010 by stevie

[stevie]

[quote name='4 Strings' post='1032011' date='Nov 21 2010, 10:35 PM']I read here: [url="http://db.audioasylum.com/cgi/m.mpl?forum=hug&n=42234&highlight=jdruley"]http://db.audioasylum.com/cgi/m.mpl?forum=...ghlight=jdruley[/url] that someone had worked out a 4" dia tube around 3" long.[/quote]
That cab size is 46 litres and he's tuning it to 62Hz. Your cab is only 28 litres - and you really want to tune it lower than 62Hz for bass guitar. As you reduce cabinet size, you have to make the port longer if you want to keep the port diameter and tuning frequency the same. Lowering the port tuning frequency also means lengthening the port. That's why my suggestion is longer than the one you've quoted: it's because your cab's smaller. A 100 x 200mm port will tune your cab to about 55Hz (and reduce the vent air speed considerably).

[Bill Fitzmaurice]

[quote name='4 Strings' post='1032011' date='Nov 21 2010, 05:35 PM']I read somewhere about the K-200 having a low Qts reduces its bass response. I don't know what that is.[/quote]True, although that's offset somewhat by the low 35Hz Fs. You can get more low end out of a driver with higher Qts, but not in a 1 cu ft box.

[4 Strings]

So, it seems I'm not going to improve things too much by changing the driver but might do so with adjustments to the port.

Bit difficult to tell if the port is 'chuffing' or the speaker complaining. Assuming we do have 'chuff', what to do?

There's not really space to make the port larger in diameter, what if I made the tube longer? How long would be best?

What if I made another 3" port (say, in the back). What length tubes would be best?

[stevie]

You're thinking along the right lines. What I suggest you do is this.

Close up the hole at the front of the cab using a piece of plywood (or put the tweeter back in). Then fit two of these ports to the back of the speaker: [url="http://www.falconacoustics.co.uk/cabinet-parts-accessories/bass-reflex-port-tubes-loudspeaker-grille-mounts-dowels-calculation-sheet/bass-reflex-port-tube-standard-reflex-66mm.html"]http://www.falconacoustics.co.uk/cabinet-p...eflex-66mm.html[/url]

The theory says that you should leave a gap equivalent to the diameter of the port between the end of the port tube and the back panel of the box. I'm not sure quite how rigidly you need to stick to that, but the ports are adjustable in length anyway - so if you want to experiment you can. Moving the port close to the back panel will drop the tuning slightly but will also cause turbulence. The ports I've suggested are just under 3 inches in diameter and will therefore give you a usable tuning at around 170mm long while still maintaining a reasonable vent air velocity.

The benefit of doing it this way is that the cabinet will still look good when you've finished. One port at the front and one at the back would be a bit of a bodge.

[stevie]

I did a similar conversion with a 2 x 10 Laney cab not so long ago. I swapped the drivers for better ones and put a 4" rear port in the back where the crappy input panel had been. I then fitted a Speakon input socket on the back. It completely transformed the cab, as its new owner will testify. And it looks professional.

Edited November 23, 2010 by stevie

[Bill Fitzmaurice]

[quote name='4 Strings' post='1033517' date='Nov 23 2010, 03:48 AM']So, it seems I'm not going to improve things too much by changing the driver but might do so with adjustments to the port.

Bit difficult to tell if the port is 'chuffing' or the speaker complaining. Assuming we do have 'chuff', what to do?

There's not really space to make the port larger in diameter, what if I made the tube longer? How long would be best?

What if I made another 3" port (say, in the back). What length tubes would be best?[/quote]Catch-22. A 3" port is too small in diameter to not chuff. A 4" would probably relieve the chuffing, 5" is better, but both require far longer ducts. The larger duct volume subtracts from the net cabinet volume, which raises the cabinet tuning and leads to boomy response. IMO you have a nice driver deserving of a new home. I wouldn't invest any more in the old one.

[stevie]

I think we have an echo in here.

Follow this link for a JBL cab that is just a bit bigger than yours: www.jblpro.com/pub/obsolete/4646a.pdf. It's 34 litres compared with your 28 litres - a difference, but not a deal-breaking one. It contains a JBL 2206 driver which models very closely to yours in the same-size box. You'll notice there are two 70mm ports at the front.

JBL built thousands of these and it is a well-proven, compact sound reinforcement bass cabinet, specifically designed to accept bass boost. JBL fitted this particular 12" driver to smaller cabs (the Soundpower 1725 was only about 20 litres if I remember correctly) as well as to bigger ones. I happen to have one of these cabs at home - it's a nice size for tucking under the piano. I have the original JBL speaker but have also fitted a number of other 12" drivers, including a Celestion neo, which is in there at the moment and which sounds great.

You are, of course, free to build another cabinet to put your Beyma into as Bill seems to be insisting ad nauseam that you do. But if, as you say, you're happy with the sound of your present cabinet, adding a second port will allow it to go louder before the onset of nasties.

[4 Strings]

Ok, all god advice, I'm sure. I think Ampeg know a little about cabs, and this one is nicely made (even with a handle hidden underneath to make it even easier to pick up) and that I'm not likely to improve on it ... apart, maybe from a port or two.

On the link to Falcon Acoustics there's an 80mm version with bell mouths. I'm thinking of two of those.

[stevie]

[quote name='4 Strings' post='1034384' date='Nov 23 2010, 08:29 PM']On the link to Falcon Acoustics there's an 80mm version with bell mouths. I'm thinking of two of those.[/quote]
Yes, I agree they look good. Unfortunately, the design constraints on your cab are so tight, that two 80mm reflex ports would be too much: the combination of the flaring and the extra diameter would require a port length of 300mm (or more).
However - and the choice is yours - a single 80mm flared port (170mm long) would be noticeably better than what you have now (because the flaring at each end helps reduce turbulence), but not as good as two 66mm ports.

Edited November 23, 2010 by stevie

[Phil Starr]

You've been getting good advice so I'm not contradicting it, just suggesting an alternative approach. If the problem is port chuffing. (I also think it could be lack of loading below the cabinet resonance which is currently too high, this will cause the speaker cone to flap around like a plastic bag in the wind at the frequencies below the cabinet resonance) then get rid of the ports and make it a sealed cab. Since Thiele/Small and computer modelling made the design of ported cabs so easy we have forgotten the alternatives (OK BFM hasn't forgotten the hybrid/horn)

Sealed cabs have better power handling and much better transient response than reflex cabs. With no ports there is no chuffing and no tuning problems. For a given speaker the cab will be smaller. The trade off is that the ported cab gives an extra 3dB of bass around the resonant frequency and the f3 roll off point will be raised in a sealed cab. Having said that there is often more deep bass from a sealed cab ie deeper but not so loud.

You can try temporarily sealing the cab by blocking the ports with a bit of wood screwed on with a bit of mastic or a bit of draft proofing foam as a seal. If you like the sound hey presto! If not then just take it off.

I haven't done the maths so I can't tell you what the Q would be for cab/speaker combination or how it might sound but it might be worth a try as it is so little effort. I've got some Beyma SM212's, lovely sound with bass but need a bigish cab for 12's.

[stevie]

That's a nice bit of lateral thinking and certainly worth a try, as it will completely bypass the port turbulence problem.
Here is a comparison of the performance of the sealed and ported versions of this cab (yellow is ported and pink is sealed):



Notice that the sealed version loses quite a bit of sensitivity between 60 and 200Hz, which will make the bass sound thinner. A tweak of the graphic eq could compensate somewhat. The downside of the sealed version is that it will not go as loud as the ported version between 50 and 100Hz. It could be loud enough though.

[Bill Fitzmaurice]

[quote name='Phil Starr' post='1034915' date='Nov 24 2010, 06:40 AM']Sealed cabs have better power handling and much better transient response than reflex cabs. For a given speaker the cab will be smaller. The trade off is that the ported cab gives an extra 3dB of bass around the resonant frequency and the f3 roll off point will be raised in a sealed cab. Having said that there is often more deep bass from a sealed cab ie deeper but not so loud.[/quote]Those observations do apply in a few cases, depending on the driver specs, but only a few. For the vast majority of drivers, no. In this case, a very low Qts driver, a sealed cab is totally inappropriate. It models very well in 50 liters net vented.