12" Driver recommendation, please

[stevie]

I think Phil's sealed cab idea is worth a try. I'd go with rear porting personally, but 4 Strings himself is the only one who can say whether a sealed cab is useable. It might also be a useful interim solution that can be easily and quickly implemented – certainly quicker than building another box, which he has said he doesn't want to do.

[4 Strings]

Thanks so much, everyone (and to our Barefaced friend Alex Caber for helpful pms) all great stuff, I have learned a lot and have come up with a cunning plan;

Sealed box would appear to give too lightweight a tone for the purposes. I need efficiency, so I don't have to put too much load on the speaker, and depth (coz I like it) and so I'm going for porting.

Internal dims are 380x380x250(ish, it curves) deep and I've calc'd the internal volume to be 33 litre. The ports may go in the side (could be one in each side - the air will be confused!) as this gives more length (~340mm as I'd like to keep at least half the tube dia space at the end) but I am also aware that the internal tubes will take up volume.

I found this: [url="http://www.linearteam.dk/default.aspx?pageid=ventcalculator"]http://www.linearteam.dk/default.aspx?pageid=ventcalculator[/url] which tells me that for a volume of 33 litre I can have 2 x 80mm x 170mm long ports and tune for 53Hz and I almost get to the non-whistling (chuffing?) threshold if I put 100W through it. (I know the amp will do a lot more than that but it rarely goes above 1/3 for rehearsals.)

If I go for the 66mm tubes I can tune the cab lower (50Hz) and they are shorter (200mm) but the air velocity goes up further and chuffing may still result. I'm not too worried compromising this last part a bit as the site this calc comes from is for hi-fi and so the threshold level of acceptable chuff (tee-hee) might be very low compared to what a bass guitar cab can get away with.

The compromise will be low chuff vs depth. I'm going to go for chuff and depth (66mm) first, if its too bad I can always open the holes for the larger tubes.

The down side is irreversible changes to the cab, but then it'll never be original again anyway. The upside is, as someone suggested, I get to put the tweeter back! (not too much point as there is loads of brightness from the Beyma - but there is an attenuator for it).

What do you think?

[Phil Starr]

Stevie's graphs show just what you'd expect with the sealed box rolling off earlier and giving more power low down, below bottom E unfortunately. 5 stringers should be interested.

For me the middle graph is significant. It shows extreme excursion below 50Hz at high power which I think may be part of the problem. Certainly this will be well beyond the excursion limit of the speaker if these frequencies get set off by room resonances/feedback.

I also question the extent to which you will hear the differences at these frequencies. I've been experimenting with just this at the moment with a low Q driver in an optimum box a high Q driver in a smaller than optimum box and running A/B comparisons with and without ports. Playing recorded music through them you get to hear all the things you'd expect. Earlier roll off and slightly reduced but cleaner bass from the sealed cab and warm woolly bass from the undersized cab, but you have to choose the source carefully to hear this. With bass guitar I can hear a difference but my guitarist can't and with the full band playing I'd be dishonest to say it makes a whole lot of difference. We just aren't very good at hearing deep bass and if you can't hear it it doesn't matter.

The other factor is the room acoustics, if the room is much less than 10 metres in it's longest dimension then it won't be possible to propagate sound at the frequencies we are worrying about and if you are trying to record deep bass is just going to be a nuisance for any mics you use.

I think we all agree though. You've got a nice speaker which would work better in a bigger box, your port is too small and incorrectly tuned and you need to move the ports to get a bigger one in. You could simply try blocking the ports and will get the result shown in Stevie's graph which may give you a sound you'd like, or not.

[stevie]

[quote name='4 Strings' post='1035918' date='Nov 25 2010, 09:22 AM']What do you think?[/quote]
You're right about the mach levels being very conservative on that calculator, but that's no bad thing. It's good to see you now have a handle on what's going on. I think you're well on your way.

[StevieD_FenderP2009]

I can honestly say I'd recommend the Celestion G12-65 speaker. I have them loaded in my Marshall JCM 800 4x12 Bass series cab and they really do pack a really warm punch as well as delivering a crystal clear top end

[Bill Fitzmaurice]

[quote name='Phil Starr' post='1035927' date='Nov 25 2010, 04:27 AM']For me the middle graph is significant. It shows extreme excursion below 50Hz at high power which I think may be part of the problem.[/quote]Loaded in 50L tuned to 50Hz excursion is at a minimum at 50Hz, and with 200w input only exceeds xmax below 43 Hz, so save for extreme drop tuning excursion is no concern. However, where excursion is at a minimum port output is at a maximum, seen in a port velocity chart, and that's what attention must be paid to where chuffing is concerned.
[quote]I also question the extent to which you will hear the differences at these frequencies. I've been experimenting with just this at the moment with a low Q driver in an optimum box a high Q driver in a smaller than optimum box and running A/B comparisons with and without ports. Playing recorded music through them you get to hear all the things you'd expect. Earlier roll off and slightly reduced but cleaner bass from the sealed cab and warm woolly bass from the undersized cab, but you have to choose the source carefully to hear this. With bass guitar I can hear a difference but my guitarist can't and with the full band playing I'd be dishonest to say it makes a whole lot of difference. We just aren't very good at hearing deep bass and if you can't hear it it doesn't matter.[/quote]All true from the standpoint of what you're hearing on stage, where more often than not boundary effects severely limit audibility below 60 Hz or so. Combined with the masking effects of the other instruments you can eliminate much, if not all, content below 60Hz and not notice the difference when the band's playing. But in the audience the situation can be very different. You can be totally unaware of high output in the lows where you're standing, whilst 40 feet away patrons are contending with drinks falling off their tables. It's the 40 to 60Hz bandwidth that large PAs pound out with authority that can define good concert sound, or for that matter ruin it when there's a ham-fisted idiot at the FOH console.

Edited November 25, 2010 by Bill Fitzmaurice

[4 Strings]

Ok, first thing will be to put the tweeter back in and seal it for rehearsal next Monday and see what the difference is. I must admit it was a bit boomy, I rolled the bass back a bit. I'll give it a try for exhaustive comparison.

But, I have played with some big, bassy cabs, I have the celebrated Monster even now, and the sound is affected throughout the fret board. Even playing up high on the 'G' sounds different with a big bottom end attached, it is fuller and, I think, more powerful. Its wrong to say that because I have a 4 string I don't need anything below the sine wave frequency of bottom 'E'. The strings give out frequencies across a wide band including rumbly lows and piercing highs (depending on your eq, string type etc) even if the majority of volume comes from the expected range.

If I'm not happy with the sealed cab because the sound is not deep enough, then its butchery time!

[Phil Starr]

[quote name='Bill Fitzmaurice' post='1036418' date='Nov 25 2010, 02:46 PM']Loaded in 50L tuned to 50Hz excursion is at a minimum at 50Hz, and with 200w input only exceeds xmax below 43 Hz, so save for extreme drop tuning excursion is no concern. However, where excursion is at a minimum port output is at a maximum, seen in a port velocity chart, and that's what attention must be paid to where chuffing is concerned.
All true from the standpoint of what you're hearing on stage, where more often than not boundary effects severely limit audibility below 60 Hz or so. Combined with the masking effects of the other instruments you can eliminate much, if not all, content below 60Hz and not notice the difference when the band's playing. But in the audience the situation can be very different. You can be totally unaware of high output in the lows where you're standing, whilst 40 feet away patrons are contending with drinks falling off their tables. It's the 40 to 60Hz bandwidth that large PAs pound out with authority that can define good concert sound, or for that matter ruin it when there's a ham-fisted idiot at the FOH console.[/quote]
I've found that spurious sounds from sources other than the strings (such as banging the guitar) can creep into the signal chain and cause some alarming excursions with some set ups. Obviously I've no idea whether this is a factor or not in this case, its just a possibility. In any case this speaker is in an undersized poorly aligned cab so the situation will be worse.
I absolutely agree with you about the PA but this speaker is for use in a practice room where I think the long slower tail off of the sealed cab could work well, especially since the sound is described as a bit boomy.

[quote name='4 Strings' post='1036626' date='Nov 25 2010, 05:18 PM']Ok, first thing will be to put the tweeter back in and seal it for rehearsal next Monday and see what the difference is. I must admit it was a bit boomy, I rolled the bass back a bit. I'll give it a try for exhaustive comparison.

But, I have played with some big, bassy cabs, I have the celebrated Monster even now, and the sound is affected throughout the fret board. Even playing up high on the 'G' sounds different with a big bottom end attached, it is fuller and, I think, more powerful. Its wrong to say that because I have a 4 string I don't need anything below the sine wave frequency of bottom 'E'. The strings give out frequencies across a wide band including rumbly lows and piercing highs (depending on your eq, string type etc) even if the majority of volume comes from the expected range.

If I'm not happy with the sealed cab because the sound is not deep enough, then its butchery time![/quote]

Good call, the physics of sound is pretty well worked out but the way we perceive it is complex and the language we have for describing it is inadequate so in the end the test that matters is how it sounds. Let us know how it works out.

Cheers

[4 Strings]

For those who remain interested, things will not be getting more interesting, I'm afraid.

Put the tweeter in and connected it up (works still, even the attenuator but not really a useful addition, definitely prefer more bass than glitter) and gave it a try indoors. Sounded fine. took it to rehearsal (not a loud time - electronic drums and the noisy keyboard player replaced by the original jazzy one) and it was great.

If I could describe it I would say more punchy and better defined. True, not much deep bass but enough punch to compensate. I would add that it was on the edge of its performance. Turn up a fraction and it complained. However, it was fine and will now stay like this until I feel the need to bore two large holes into the side of the cab because things get noisier.

Thanks all who have taught me stuff in this, sorry it didn't end up with any real experimentation, but it sounds fine within its limits while I can get away with it. We may be joined by another guitarist which may push it over the edge ...!

[Phil Starr]

Sadly I find this interesting.

Good result. If you get overwhelmed and your guitards are unable to find the volume controls try cutting the bass a bit before you turn up.

Good luck

[Bill Fitzmaurice]

[quote name='Phil Starr' post='1037460' date='Nov 26 2010, 04:50 AM']I've found that spurious sounds from sources other than the strings (such as banging the guitar) can creep into the signal chain and cause some alarming excursions with some set ups.[/quote]
The downside of a vented cab is that excursion rises below the tuning frequency, and below bandwidth string thump noise can be a major problem. That's usually compensated for by a high pass filter in the amp, most have them, but not all. This thread explains:
[url="http://www.talkbass.com/forum/showthread.php?t=714170"]http://www.talkbass.com/forum/showthread.php?t=714170[/url]

With sealed cabs excursion decreases as frequency decreases, so high passing is seldom required. But sensitivity and therefore output also decreases, so it's not the best route to eliminating below bandwidth noise and driver over-excursion.

[Phil Starr]

[quote name='Bill Fitzmaurice' post='1043214' date='Dec 1 2010, 12:51 AM']The downside of a vented cab is that excursion rises below the tuning frequency, and below bandwidth string thump noise can be a major problem. That's usually compensated for by a high pass filter in the amp, most have them, but not all. This thread explains:
[url="http://www.talkbass.com/forum/showthread.php?t=714170"]http://www.talkbass.com/forum/showthread.php?t=714170[/url]

With sealed cabs excursion decreases as frequency decreases, so high passing is seldom required. But sensitivity and therefore output also decreases, so it's not the best route to eliminating below bandwidth noise and driver over-excursion.[/quote]
Hi Bill,
as usual I agree with pretty much all that you say. The one word that I question is 'best' I'm not sure that there is a single engineering solution to the problems of amplifying bass guitar. We all know how to model the behaviour of cone speakers and the advantages and disadvantages of sealed versus ported are clear. Ported enclosures give an extra 3db at resonance and almost that around the bottom octave. Porting doesn't raise the resonant frequency in the same way as a sealed box. Below this the Ported cab cuts off at 18-24dB/octave depending upon the exact alignment and the sealed cab at 12dB/octave depending upon Q. All this is reflected in Stevie's graphs.

I'll freely admit I'm trying to pick your brain here. Clearly sealed cabs offer better transient response and subsonic behaviour and, with a given driver, smaller size. The ports create problems of wind noise and manufacturing spreads in drive units mean that unless each driver is tested individually the tuning is a bit hit and miss. Despite all this most current bass speakers are ported designs.

Add in the psycho-acoustics. We can't hear the bottom octave at all well and our brains construct what we hear from a partial pattern of information giving rise to auditory illusions similar to optical illusions. Then add in the effect of floors walls and ceilings and the rest of room acoustics and my question is how audible are these things in practice.

Your own designs exploit all this of course, so why shouldn't another designer exploit the same things in developing a sealed design?

[MoonBassAlpha]

would that be where sfx's Thumpinator would come in handy?

[Bill Fitzmaurice]

[quote name='Phil Starr' post='1043367' date='Dec 1 2010, 04:27 AM']Clearly sealed cabs offer better transient response and ... with a given driver, smaller size. The ports create problems of wind noise and manufacturing spreads in drive units mean that unless each driver is tested individually the tuning is a bit hit and miss.[/quote]That's the conventional wisdom, but it's not true. For every driver where that scenario does apply you'll find six where it doesn't. IME the only drawback to a vented box in general is the potential for driver over-excursion below the intended passband, and that's cured with a couple of capacitors in the signal chain to limit the LF bandwidth of the amp.
[i]"would that be where sfx's Thumpinator would come in handy?"[/i] Or that. Not mentioned yet is that, while a sealed cab naturally controls below bandwidth excursion, it does nothing to relieve the amp of the load that amplifying below bandwidth content creates. Even with a sealed cab the sound will be cleaner and the amp will have more headroom when below bandwidth content is filtered.
[quote]why shouldn't another designer exploit the same things in developing a sealed design?[/quote]The main obstacle is the lack of suitable drivers.

Edited December 1, 2010 by Bill Fitzmaurice

[4 Strings]

The Thumpinator sounds great but for that price I could buy a pretty good speaker.

Is there a cheaper way to hit the rumble? If I wanted to put a cap in line I could solder something to the crossover board.

Any ideas on values etc? Also, would it be in parallel across the speaker?

[Bill Fitzmaurice]

[quote name='4 Strings' post='1044469' date='Dec 1 2010, 06:07 PM']The Thumpinator sounds great but for that price I could buy a pretty good speaker.

Is there a cheaper way to hit the rumble? If I wanted to put a cap in line I could solder something to the crossover board.

Any ideas on values etc? Also, would it be in parallel across the speaker?[/quote]
A cap alone won't work, you need at least cap and coil, and the price would be far more than a Thumpinator.

[LawrenceH]

[quote name='Bill Fitzmaurice' post='1044482' date='Dec 1 2010, 11:26 PM']A cap alone won't work, you need at least cap and coil, and the price would be far more than a Thumpinator.[/quote]

Agreed, you'd be far better sorting this at line level in the FX loop or similar. But I'd suggest you beg, steal or borrow something like an active crossover unit to play with first and seeing if you've actually got a problem with these frequencies before you spend actual money on something you then have to cart around everywhere.

I'm still very intrigued to know which amazing vented box PA cabs will give equivalent bass roll-off and group delay characteristics to a simple sealed box based around the same driver, whilst retaining the excursion benefits of the vented design...

[Phil Starr]

[quote name='4 Strings' post='1044469' date='Dec 1 2010, 11:07 PM']The Thumpinator sounds great but for that price I could buy a pretty good speaker.

Is there a cheaper way to hit the rumble? If I wanted to put a cap in line I could solder something to the crossover board.

Any ideas on values etc? Also, would it be in parallel across the speaker?[/quote]
It is not sensible to try to put a filter in between the speaker and the amp, it needs to go earlier in the signal chain, either the effects loop or between the guitar and amp. It's not absolutely clear if this is a problem though, it is just one possibility, your amp may already be filtering out subsonics. Most do to some extent.

If you turn down the bass control a little it will remove some of the subsonics, which is why I suggested it earlier. It will also change what you hear so you need to experiment to get the best out of this. If you have a graphic rather than conventional tone controls then just use the lowest one and the results should be fairly good. Lots of subsonics gone but not too much signal.

Take all our techie squabbling with a pinch of salt. If it sounds good then it is good.

[Phil Starr]

[quote name='Bill Fitzmaurice' post='1043840' date='Dec 1 2010, 02:33 PM']That's the conventional wisdom, but it's not true. For every driver where that scenario does apply you'll find six where it doesn't. IME the only drawback to a vented box in general is the potential for driver over-excursion below the intended passband, and that's cured with a couple of capacitors in the signal chain to limit the LF bandwidth of the amp.
[i]"would that be where sfx's Thumpinator would come in handy?"[/i] Or that. Not mentioned yet is that, while a sealed cab naturally controls below bandwidth excursion, it does nothing to relieve the amp of the load that amplifying below bandwidth content creates. Even with a sealed cab the sound will be cleaner and the amp will have more headroom when below bandwidth content is filtered.
The main obstacle is the lack of suitable drivers.[/quote]
I'm sorry to disagree with you but this is a bit silly. The differences between transient responses of different boxes (second order Bessel, second order Butterworth assorted Chebychev, QB3, BB4 etc) are all described perfectly adequately in the mathematical models and born out by measurement. Have a look in Dickason or a look at Gunther J Krauss, AES Mar1990. "Low frequency Transient Response Problems in Vented boxes". This isn't really a matter of opinion but of measurement. OK the worst sealed cab with a tiny magnet in a small box might have worse transient behaviour than a well designed QB3 but 6:1 in favour of ported cabs?

The [u]only[/u] drawback? You've already said yourself about the noises associated with the ports but the real problem is that of ensuring correct alignment. Vas, fs and Qts are subject to manufacturing spreads QL is usually an assumed figure and there are problems with the pressure changes around the ends of ported tubes that lead to us using approximations in Thiele/Small calculations. As well as the transient, noise and tuning problems there are numerous other issues confronting the designer of a reflex system. All speaker design is a compromise as I am sure you know.

I'm sorry if that comes across as a tetchy rant, but I am really interested in your ideas. Your 'Jack' for example uses a horn to boost efficiency (and transient response), but as you know it cuts off well above the bottom octaves. You reinforce this with a reflex port but this is going to be a lot less efficient than your horn in its pass band. You also advise using floors and walls to reinforce the bass but still your design depends upon the way we perceive sound. I'm sure your design sounds good with bass guitar because upper bass and lower mids are handled well and deep bass is less important and yet you don't allow the same leeway to sealed cabs.

High efficiency has advantages. Flat frequency responses aren't a guarantee of good sound especially when talking about instrument cabs. Most of my designs are reflex designs for what I hope are good reasons. Ported, sealed and horn cabs have advantages and disadvantages which are all well known and I am hoping that you can add to the debate with your experience of how these theoretical problems work out in practical situations.

[Bill Fitzmaurice]

[quote name='Phil Starr' post='1044858' date='Dec 2 2010, 06:37 AM']Have a look in Dickason or a look at Gunther J Krauss, AES Mar1990. "Low frequency Transient Response Problems in Vented boxes".[/quote]
We've gotten a fair bit along since 1990. The very notion of different alignments (second order Bessel, second order Butterworth assorted Chebychev, QB3, BB4 etc) has been rendered obsolete. They date to the days of hand calculation; with modern software an infinite number of 'alignments' are easily realized, including vented which virtually duplicate sealed within a desired passband.
[quote]I am hoping that you can add to the debate with your experience of how these theoretical problems work out in practical situations.[/quote]
I have no time for debating, I'm too busy designing speakers. I offer the benefit of my professional expertise. Accept it or reject it as you see fit.

[LawrenceH]

[quote name='Bill Fitzmaurice' post='1045081' date='Dec 2 2010, 01:51 PM']We've gotten a fair bit along since 1990. The very notion of different alignments (second order Bessel, second order Butterworth assorted Chebychev, QB3, BB4 etc) has been rendered obsolete. They date to the days of hand calculation; with modern software an infinite number of 'alignments' are easily realized, including vented which virtually duplicate sealed within a desired passband.[/quote]

The design methodology has changed with the advent of modelling software but the underlying electromechanical principles haven't. Plus the benefit of things like LEAP, winISD, hornresp and the like are that anyone can have a play with the various parameters in fairly clueless fashion and quickly see how these characteristics will vary, so get a feel for what is and isn't possible. With your favoured Eminence drivers I've never seen a single vented box model that gives both frequency and time-dependent characteristics that match a sealed cabinet based on the same drivers (much less heard one). It's pretty clear from both looking at the maths and playing with the model that with essentially only two parameters to play with it's not going to happen. Unless you think TS-based model is drastically wrong (which it isn't). Obviously for many real-world applications the vented box will outperform the sealed, but for some people volume isn't everything.

[stevie]

[quote name='Phil Starr' post='1044858' date='Dec 2 2010, 11:37 AM']I'm sorry to disagree with you but this is a bit silly.[/quote]
It's not only silly - it's complete bollocks. The output from the vent is delayed in time compared with the output from the front of the speaker cone. Thus, a reflex speaker cannot by definition have a transient response as good as that of a sealed speaker - because that delay is always present when there is output from the port. [url="http://en.wikipedia.org/wiki/Bass_reflex"]http://en.wikipedia.org/wiki/Bass_reflex[/url]
Let us listen to what a real speaker designer has to say about this, shall we? Cue Mr. Siegfried Linkwitz. The name may be familiar to you if you have an interest in loudspeaker design.

([i]On his decision to use a sealed cabinet for his state-of-the-art subwoofer[/i]) -
"I did not consider alternate approaches to subwoofer design as [i][b]acceptable for meeting my goal of accurate sub-bass reproduction[/b][/i]. This includes [b][i]vented[/i][/b], passive radiator and acoustic bandpass woofers. They all rely on [b][i]resonant energy storage[/i][/b] to increase efficiency and to reduce size.
([i]On his choice of a sealed alignment for his Pluto speaker[/i]) -
"Finally, most box speakers use [b][i]vented [/i][/b]enclosures which means [i][b]stored energy[/b][/i] to increase otherwise insufficient or distorted bass output. PLUTO+ is sealed with a Q = 0.5 roll-off at the low end of its frequency range for [b][i]optimum highpass transient response[/i][/b]."

I'd be very interested to see anyone attempt to prove Linkwitz wrong on this. Over to you Mr Fitzmaurice - or are you too busy designing loudspeakers

[4 Strings]

Well, what a journey this as been.

Started off wanting a suggestion for a replacement speaker as mine distorts when I turn it up too much. Went through the fact that it had a port instead of a tweeter, to putting more and bigger port in, to not replacing the speaker as its actually quite a good one, even though some parameters I'd never heard of were not suitable, to me putting the tweeter back in and being ok with the result. Totally opposite result to that expected. All because of some good advice from those who know way more than me.

Thanks all, been a great ride, I hope to continue it if I need more power and dig holes in my little Ampeg cab, and I'm really grateful for the advice.

Please don't fight about it though.

[LawrenceH]

[quote name='4 Strings' post='1047018' date='Dec 4 2010, 01:28 AM']Thanks all, been a great ride, I hope to continue it if I need more power and dig holes in my little Ampeg cab, and I'm really grateful for the advice.[/quote]

Glad to hear it's sounding better - if you do decide you need to get the most out of this driver at the low end then I /think/ everyone would agree that, as BFM and others have said, the best way would be a slightly bigger box. The advantages are twofold - first you get extended bass response anyway from the volume increase, second you don't need such a long port to tune it. You're probably at the performance limit of a box that big at the moment and won't gain anything by changing it around further.

Edited December 4, 2010 by LawrenceH

[redstriper]

[quote name='4 Strings' post='1047018' date='Dec 4 2010, 01:28 AM']Well, what a journey this as been.

Please don't fight about it though.[/quote]

Spoilsport - this is what I call entertainment