Porting cabs

[LITTLEWING]

I've just acquired an Ashdown Mag 810 and although it needs a bit of driving and I have a good 'scooped' sound with my Ashdown Evo2 300 head, I can't help thinking the cab could be upgraded with a couple of ports in the front of the sealed cab. I need the bass knob on full to get decent bass out whereas my old Peavey 410 TVX with bottom vent would have rattled the windows out. Would this ruin a perfectly good tuned box (Ashdown must know what they're doing!) or is it worth a couple of hours sweat?

[Bill Fitzmaurice]

[quote name='LITTLEWING' timestamp='1352643566' post='1865467']
I can't help thinking the cab could be upgraded with a couple of ports in the front of the sealed cab. [/quote]In order to vent the cab you must have the driver T/S specs and use speaker modeling software to see if it will work, and if so determine the required vent configuration, if the drivers have specs compatible with a vented cab to begin with. [quote]Ashdown must know what they're doing![/quote]Don't be so sure. As often as not drivers are chosen based on their price, not how well they function.

[LITTLEWING]

Cheers for that, Bill. I think I'll leave things just as they are and keep my tools locked up in the garage!!

[Guest bassman7755]

porting a cab is a very exact science, most likely outcome is that you trash the drivers due to resonant peaks you've inadvertently created.

[Mr. Foxen]

Ha, cab makers got away with unscientific porting for a pretty long time.

[Protium]

[quote name='Bill Fitzmaurice' timestamp='1352654617' post='1865658']
Don't be so sure. As often as not drivers are chosen based on their price, not how well they function.
[/quote]

Not everyone can afford to buy cabs with the most expensive speakers in... Imagine Ashdown's entry range cabs costing the same as a barefaced, they'd never sell any
By the way, their amps/cabs are present on almost every major festival stage in this country. By that standard I reckon they know [i]exactly[/i] what they're doing

[PlungerModerno]

[quote name='Protium' timestamp='1352674208' post='1866064']
Not everyone can afford to buy cabs with the most expensive speakers in... Imagine Ashdown's entry range cabs costing the same as a barefaced, they'd never sell any
By the way, their amps/cabs are present on almost every major festival stage in this country. By that standard I reckon they know [i]exactly[/i] what they're doing
[/quote]

I think there's a big gap between the BFM, barefaced and greenboy designs - which are modern, carefully calibrated designs often matching the leading PA and other high-end cab makers (and even besting them by a significant amount on price) - and an entry level cab that has obvious flaws in design that could be solved with inexpensive tweaks (eg. lack of bracing, tuning totally off for the drivers etc.) These tweaks would make sense given the scale at which production takes place - and while they might shave a little off margins, the improved performance would compensate with helping sales - AFAIK of course.

I think also that manufacturers may be complacent as their competitors are doing the same thing - perhaps it's to sell more of the more expensive ranges of cabs, where even more profit is to be had. Seems like a good way to damage your reputation as a maker of cabs though.

[Bill Fitzmaurice]

[quote name='Protium' timestamp='1352674208' post='1866064']
By the way, their amps/cabs are present on almost every major festival stage in this country. By that standard I reckon they know [i]exactly[/i] what they're doing
[/quote]Perhaps. That doesn't mean they don't cheap out on drivers, just that they're no worse than most other companies in that respect. And you're assuming that they design their own cabs. Most companies do not, farming that job out to independent speaker designers, like me. That gives me the unique opportunity to know exactly what manufacturers do to maintain the highest possible profit margins, and that seldom includes using the best drivers available.

[JohnFitzgerald]

I've tried my best to like Ashdown stuff. I just find the sound indescribably wooly and unresponsive.

I regularly have a play through a 6x10" ABM cab with ABM 500. It may be almost industry standard, but I'm afraid I'm just not seeing the logic.
Plenty of woof, no mid, indifferent top.

Not for me.

On the flip side, a 2x10" Markbass wedge style combo that I used at Summer's End was everything I ever wanted a bass amp to be.
Costs less too but just has a far more audible sound.

[LawrenceH]

The speakers Ashdown use have really varied over the years. My old and very humble entry-level Electric Blue model (150 watt, made in UK) had a very respectable large heavy magnet Sica 12" driver that was rated at 250 watt RMS and had quite a reasonable excursion capability. Not the brightest speaker, probably started dropping off above 2k, but it was overspecced compared to most entry level combos. I am sure they don't use the same model on the modern Chinese versions.

[Bassman62]

Many loudspeaker cab manufacurers use the least expensive speakers that they can get away with whilst charging phenominaly high prices for the finished product.
Some few short years ago two of the most popular cabs from a leading UK manufacturer retailed at £499 each, these being a 4x10 and a 1x15, the 10" & 15" speakers left the actual speaker manufacturer for approx £9.50 (10") & £32 (15") each which equated £461 £467 for the empty cabinets which were basic tuned cabinets, nothing complex.

[Mr. Foxen]

[quote name='Bassman62' timestamp='1352996423' post='1870320']
Many loudspeaker cab manufacurers use the least expensive speakers that they can get away with whilst charging phenominaly high prices for the finished product.
Some few short years ago two of the most popular cabs from a leading UK manufacturer retailed at £499 each, these being a 4x10 and a 1x15, the 10" & 15" speakers left the actual speaker manufacturer for approx £9.50 (10") & £32 (15") each which equated £461 £467 for the empty cabinets which were basic tuned cabinets, nothing complex.
[/quote]

They had to pay BFM for designing the cab though.

[Protium]

[quote name='Bassman62' timestamp='1352996423' post='1870320']
Many loudspeaker cab manufacurers use the least expensive speakers that they can get away with whilst charging phenominaly high prices for the finished product.
Some few short years ago two of the most popular cabs from a leading UK manufacturer retailed at £499 each, these being a 4x10 and a 1x15, the 10" & 15" speakers left the actual speaker manufacturer for approx £9.50 (10") & £32 (15") each which equated £461 £467 for the empty cabinets which were basic tuned cabinets, nothing complex.
[/quote]

All loudspeaker cabinet manufacturers do: Barefaced for example charge ~£525 for a compact. A £125 speaker, equating to £400 for a bit of plywood

Edited November 15, 2012 by Protium

[Bill Fitzmaurice]

[quote name='Bassman62' timestamp='1352996423' post='1870320']
Many loudspeaker cab manufacurers use the least expensive speakers that they can get away with whilst charging phenominaly high prices for the finished product.
Some few short years ago two of the most popular cabs from a leading UK manufacturer retailed at £499 each, these being a 4x10 and a 1x15, the 10" & 15" speakers left the actual speaker manufacturer for approx £9.50 (10") & £32 (15") each which equated £461 £467 for the empty cabinets which were basic tuned cabinets, nothing complex.
[/quote]Look at what Orange charges for their 410, then see what retailers get for four Eminence Beta 10s. For the price one would expect the 410 to contain premium drivers, especially as Orange doesn't pay the retail price.
[quote]All loudspeaker cabinet manufacturers do: Barefaced for example charge ~£525 for a compact. A £125 speaker, equating to £400 for a bit of plywood [/quote]OTOH that bit of plywood doesn't assemble itself. Rule of thumb for any manufacturer to stay in business they must make no less than the cost of all materials, labor, marketing and distribution plus 40%. Since BFB has lower marketing and distribution by selling direct they're a bargain.

[RandomBass]

Yes I've always considered BFB to be a bargain, considering what you get. Expensive compared to mainstream? perhaps. But still a bargain.

[Bill Fitzmaurice]

[quote name='RandomBass' timestamp='1353047389' post='1870872']
Yes I've always considered BFB to be a bargain, considering what you get. Expensive compared to mainstream? perhaps. But still a bargain.
[/quote]Expensive? Not at all. BFB uses premium drivers, none of the 'mainstream' manufacturers do. For that matter neither do most boutique brands.

[Protium]

[quote name='Bill Fitzmaurice' timestamp='1352755376' post='1867145']
Perhaps. That doesn't mean they don't cheap out on drivers, just that they're no worse than most other companies in that respect. And you're assuming that they design their own cabs. Most companies do not, farming that job out to independent speaker designers, like me. That gives me the unique opportunity to know exactly what manufacturers do to maintain the highest possible profit margins, and that seldom includes using the best drivers available.
[/quote]

Let's be honest, there's not a great deal of designing involved in making a rectangular box is there.

[Bill Fitzmaurice]

[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]It's still beyond the skill set of marketing departments and executives. And even a seemingly simple box on the outside if well designed is anything but simple on the inside. Then there's the matter of crossovers, which are not the least bit easy to design properly. If it was as easy as it seems you wouldn't find so many cabs with inadequate or non-existent bracing and damping, nor any with horizontally arrayed drivers.

[Mr. Foxen]

Not designing them, and making them anyway, is easy.

[Phil Starr]

This is all getting a bit unreal. When I used to make speakers I paid rent on a workshop, paid bills, bought machine tools etc etc. There's labour costs including the fact that only a fraction of your time is spent making speakers, You have to factor in design time, marketing effort, paperwork dealing with customers etc.etc.

You don't go to a good restaurant and expect to pay for just the ingredients, you know that a team of highly skilled people have spent all day prepping ingredients to serve a couple of hundred meals and that the posh surroundings don't come cheap. there's probably nothing to cooking the meal that you couldn't do at home. It would just be a lifetime's training to reach the skill level needed.

You probably could build a cab like the Barefaced for £75 but calculate how long it takes and add in the labour costs (what do you pay your plumber or to get your car fixed) and you'll realise there isn't a lot of profit in that £450. You'll need to sell a lot of speakers to make a living.

[voxpop]

I have a cab the contains a Celestion BL15-400X driver.
The cab has two 7cm holes cut into the front of the cab.
To my ears it sounds better with the holes blocked with foam. It gets tighter and more dynamic.
Why cut the holes into the front as it is clearly not tuned to any frequency as there is no tubes behind them.

Seems to me it's a crazy design, or maybe there is no design or thought put into it.

Just put a driver into a box, cut to holes and charge a fortune.

[bremen]

Doesn't have to have tubes to be tuned to a particular frequency; the thickness of the baffle is part of the resonant system.

Agreed that many cabs are better off with the ports blocked though.

[Balcro]

[quote name='voxpop' timestamp='1353316061' post='1873435']
I have a cab the contains a Celestion BL15-400X driver.
The cab has two 7cm holes cut into the front of the cab.
To my ears it sounds better with the holes blocked with foam. It gets tighter and more dynamic.
Why cut the holes into the front as it is clearly not tuned to any frequency as there is no tubes behind them.

Seems to me it's a crazy design, or maybe there is no design or thought put into it.

Just put a driver into a box, cut to holes and charge a fortune.
[/quote]

Has the foam been stuffed into the holes or has a piece of foam been properly cut to fit and set into the hole?

Balcro.

[Bill Fitzmaurice]

[quote name='voxpop' timestamp='1353316061' post='1873435']
I have a cab the contains a Celestion BL15-400X driver.
The cab has two 7cm holes cut into the front of the cab.
To my ears it sounds better with the holes blocked with foam. It gets tighter and more dynamic.
Why cut the holes into the front as it is clearly not tuned to any frequency as there is no tubes behind them.

Seems to me it's a crazy design, or maybe there is no design or thought put into it.

[/quote]That porting would tune a typical 1x15 sized cab to 70-80Hz, making it a one-note boom machine.
I once ported a sealed cab in that fashion. I was 15 years old, hadn't the slightest notion of how speakers worked, never having even seen a ported cab, so the error of my ways could be forgiven. That forgiveness shouldn't be granted to a company that should know better.

Edited November 19, 2012 by Bill Fitzmaurice

[bremen]

[quote name='Bill Fitzmaurice' timestamp='1353331017' post='1873667']
That porting would tune a typical 1x15 sized cab to 70-80Hz, making it a one-note boom machine.

[/quote]

So there IS method in their madness. A one-note boom machine with loads of output at 70Hz sounds great in a music shop when you try it out 'loads of bass! what's not to like!'

Of course, it sounds sh*t on stage, but that's probably the fault of the acoustics of the venue, or the sound guy, or the guitarists...can't be the cab, it sounded great in the shop.