Porting cabs

[LawrenceH]

Depends a lot on the exact size of the box - a 90 litre cab with 2x7cm holes comes in about 60Hz. With that particular Celestion it'll still give a hefty 4dB hump centred around 100Hz. More than I'd want but it's not such a bad sound for a lot of scenarios and it makes the box able to go very loud without too much power and it will sound bassy - an old-school solution. Don't forget a lot of mixing desk shelving bass EQ shelves/cuts are set around 80-100Hz, the extra octave below requires a BIG size/cost premium. 42Hz is a lot deeper than most people think!

I find it odd that Bill is always so down on other people's non-flat designs, when his own Jacks are very deliberately designed this way with a massive hump in the low mids, a BIG drop between 1 and 2kHz and comparatively little deep bass. I imagine they really suit a certain P bass vibe, but it didn't work for me - it's always a compromise and different people prefer the sound of different solutions. Even damping in cabs is something of a personal taste thing for bass, it's not always meant to be hifi.

Edited November 19, 2012 by LawrenceH

[Bill Fitzmaurice]

[quote name='LawrenceH' timestamp='1353335721' post='1873744']


I find it odd that Bill is always so down on other people's non-flat designs, [/quote] I have [i]never [/i]said flat designs are superior. If I thought they were that's what I'd offer. [quote]when his own Jacks are very deliberately designed this way with a massive hump in the low mids[/quote] That gives a strong low mid presence to offset the accentuation an octave below typical of most rooms, quite the opposite of having a midbass hump in the same region where stages/rooms also contribute to response, adding to the problem of boom. [quote]comparatively little deep bass [/quote] Compared to what? They better most commercial cabs. Just look at the SPL charts for commercial cabs... oh, yeah, right,[i] there aren't any. [/i]
[quote] it didn't work for me [/quote]And some prefer Lexus to Mercedes. To each their own.

[voxpop]

[quote name='LawrenceH' timestamp='1353335721' post='1873744']
Depends a lot on the exact size of the box - a 90 litre cab with 2x7cm holes comes in about 60Hz. With that particular Celestion it'll still give a hefty 4dB hump centred around 100Hz. More than I'd want but it's not such a bad sound for a lot of scenarios and it makes the box able to go very loud without too much power and it will sound bassy - an old-school solution. Don't forget a lot of mixing desk shelving bass EQ shelves/cuts are set around 80-100Hz, the extra octave below requires a BIG size/cost premium. 42Hz is a lot deeper than most people think!

I find it odd that Bill is always so down on other people's non-flat designs, when his own Jacks are very deliberately designed this way with a massive hump in the low mids, a BIG drop between 1 and 2kHz and comparatively little deep bass. I imagine they really suit a certain P bass vibe, but it didn't work for me - it's always a compromise and different people prefer the sound of different solutions. Even damping in cabs is something of a personal taste thing for bass, it's not always meant to be hifi.
[/quote]



This is exactly the sound of my cab, very old school with a big hump around 100hz. It's not bad at producing a good stage sound but sometimes the hump can interfere with the room, that why I block up the holes / ports.

Thanks to all that have stepped in and given their points of view,I've taken on board all ideas and opinions.

[stevie]

Massive humps and bumps have no place in any speaker system. They are usually caused by bad design or skimping on cost. The 100Hz bump that is common in bass guitar cabs is usually caused by using an undersized magnet to save money.

[bremen]

[quote name='stevie' timestamp='1353344836' post='1873987']
Massive humps and bumps have no place in any speaker system. They are usually caused by bad design or skimping on cost. The 100Hz bump that is common in bass guitar cabs is usually caused by using an undersized magnet to save money.
[/quote]

My preference is also flat, but humps and bumps in the right places can add to the character of a sound in a positive way, wouldn't you agree?

Like your sig btw.

[LawrenceH]

[quote name='Bill Fitzmaurice' timestamp='1353338082' post='1873776'] I have [i]never [/i]said flat designs are superior. If I thought they were that's what I'd offer. [/quote]
That's not quite what I said. I was pointing out that your criticism of a design for having a built in hump was apparently at odds with your own design philosophy, you just have a different preference.
[quote name='Bill Fitzmaurice' timestamp='1353338082' post='1873776']
That gives a strong low mid presence to offset the accentuation an octave below typical of most rooms, quite the opposite of having a midbass hump in the same region where stages/rooms also contribute to response, adding to the problem of boom.
[/quote]
I was at pains to point out that it works for a lot of people and I was not criticising the design. However, that assertion of where you find boom is at odds with my own experience doing a lot of FoH work in small/medium venues - the range where I've encountered the most trouble is between 200 and 300Hz, the point where the horn loading of your Jacks kicks in. Sub-150 is much easier to control with placement by comparison.
[quote name='Bill Fitzmaurice' timestamp='1353338082' post='1873776']
Compared to what?
[/quote]
Compared to themselves in the higher register - if you needed much true bass for volume perception then there would be no benefit to a low-mid horn loading that didn't increase the low power handling, since that would already be the limiting factor. As it is, it's a question of voicing preference.

[quote name='Bill Fitzmaurice' timestamp='1353338082' post='1873776']
They better most commercial cabs. Just look at the SPL charts for commercial cabs... oh, yeah, right,[i] there aren't any. [/i]
[/quote]

There's no question horn loading makes them louder per woofer employed. Whether that's better is a matter of opinion. There are plenty of charts in the sound reinforcement arena where your cabs are competing. I actually liked the sound of your Jacks once (heavily) EQ'd, up to about 1kHz, but found them very troublesome beyond that point and could not correct it with digital EQ. I imagine the more broad-band omnitop designs would serve me much better. For many people though box size is more of a limiting factor than number of woofers, and that's where a 'compact' hybrid design relying on reflex loading for the bottom 2 octaves loses out at the low end, as it's necessarily bigger per woofer unit. It's no accident that horns are near-ubiquitous for treble and rare for lower frequencies, and it's not just a question of build complexity.

[quote name='Bill Fitzmaurice' timestamp='1353338082' post='1873776']
And some prefer Lexus to Mercedes. To each their own.
[/quote]

Exactly, hence me wanting to point out that actually those old-school 'thoughtless' designs aren't chosen purely at random or just to 'trick' people, they have their place from a price/size/performance perspective just as your own designs do.

[voxpop]

[quote name='stevie' timestamp='1353344836' post='1873987']
Massive humps and bumps have no place in any speaker system. They are usually caused by bad design or skimping on cost. The 100Hz bump that is common in bass guitar cabs is usually caused by using an undersized magnet to save money.
[/quote]

Would I be better off perminatly blocking off the cab ports / holes and making a sealed cab with the celestion driver.

[LawrenceH]

[quote name='voxpop' timestamp='1353345096' post='1873998']
Would I be better off perminatly blocking off the cab ports / holes and making a sealed cab with the celestion driver.
[/quote]

If the sound works for you and is still loud enough then why not?

[quote name='stevie' timestamp='1353344836' post='1873987']
Massive humps and bumps have no place in any speaker system. They are usually caused by bad design or skimping on cost. The 100Hz bump that is common in bass guitar cabs is usually caused by using an undersized magnet to save money.
[/quote]

For PA I agree, but not necessarily for an electric instrument where 'flat' is somewhat arbitrary. The massive resonance peak in a magnetic pickup respose is an example of a bump that's desirable to many electric guitar/bass players. There's nothing that says you have to EQ only at a given stage in the signal chain. I often find myself bumping up around 80-100Hz on my (smooth roll-off, relatively flat) speakers to give a bit more authority to the sound in a small venue.

[stevie]

[quote name='bremen' timestamp='1353344945' post='1873992']
My preference is also flat, but humps and bumps in the right places can add to the character of a sound in a positive way, wouldn't you agree?
[/quote]
If you're lucky, yes. The problem is that the frequencies with humps and bumps are often accompanied by other problems that you don't want (like resonances, distortion, suckouts). Better to have a clean, smooth (though not necessarily flat) frequency response that lets your 'tone' shine through. Then dial in your 'character' before it gets to the speaker.

I know others take a different approach, and that's fine, but I don't want my speakers to add colour.

[stevie]

[quote name='voxpop' timestamp='1353345096' post='1873998']
Would I be better off perminatly blocking off the cab ports / holes and making a sealed cab with the celestion driver.
[/quote]

As Lawrence says, you'll reduce power handling a bit, but that Celestion driver has a very high Qts which is more suited to a sealed system. The undersized magnet syndrome strikes again.

[Bill Fitzmaurice]

[quote name='LawrenceH' timestamp='1353344951' post='1873993']
That's not quite what I said. I was pointing out that your criticism of a design for having a built in hump was apparently at odds with your own design philosophy, you just have a different preference.[/quote]Intentional response humps to achieve a desired response have their place. Unintentional humps caused by poor design and/or inferior components do not, especially when situated at frequencies that are problematic.

[voxpop]

[quote name='stevie' timestamp='1353348173' post='1874065']


As Lawrence says, you'll reduce power handling a bit, but that Celestion driver has a very high Qts which is more suited to a sealed system. The undersized magnet syndrome strikes again.
[/quote]

Would it be better to use this driver, I could do with a 16 ohm replacement instead of the current 8 ohm celestion.

http://www.lean-business.co.uk/eshop/eminence-delta-15-16ohm-15-400watt-speaker-p-774.html

Edited November 19, 2012 by voxpop

[Bill Fitzmaurice]

[quote name='voxpop' timestamp='1353351661' post='1874136']
Would it be better to use this driver, I could do with a 16 ohm replacement instead of the current 8 ohm celestion.

[url="http://www.lean-business.co.uk/eshop/eminence-delta-15-16ohm-15-400watt-speaker-p-774.html"]http://www.lean-busi...aker-p-774.html[/url]
[/quote]It specs best with a sealed cab, and the 1.6mm xmax renders it almost useless for bass with much more than a 30 watt amp.

[Balcro]

[i][b]Voxpop: "This is exactly the sound of my cab, very old school with a big hump around 100hz. It's not bad at producing a good stage sound but sometimes the hump can interfere with the room, that why I block up the holes / ports."[/b][/i]


By sticking the foam in the hole you may have created a happy accident that cleans up the sound. Some early audio pioneers did the same in the fifties. The result is a restricted "port" through which the speaker breathes. Basically the restriction smoothed out the hump/boost in the response linked to an ordinary port (with a tube) and theoretically gave you a little more extended bass.

Balcro.

[Guest gazzatriumph]

[quote name='Protium' timestamp='1353272527' post='1873177']
Let's be honest, there's not a great deal of designing involved in making a rectangular box is there.
[/quote]

lol

[3below]

[quote name='Protium' timestamp='1353272527' post='1873177']
Let's be honest, there's not a great deal of designing involved in making a rectangular box is there.
[/quote]

The challenge is designing the holes correctly