Large ported subwoofer

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sploo

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Thanks for quick response ------ About 8ins - I have some poss longish throw drivers already, my Q was rather about the frequency splitting options given a standard 2 channel stereo output.
Ah right. In terms of frequency; anything much over 120Hz will allow the sub location to be identified, so unless you can position it in the middle of the loudspeakers then a crossover of 100Hz or lower is probably best.

You definitely want a lowpass for the sub; don't try to send a full range signal to it as it'll just cause distortion.

Ideally there would be a highpass filter for the loudspeakers (so the low frequencies only go to the sub); though it can work without.

If you have two subs then you can have the left and right signals go into each separately; though generally you don't get much benefit with a low frequency crossover (as the sub location can't be identified by your ears anyway). With a single sub you can use an adapter to combine both channels to a single mono input for the lowpass filter + sub amp.
 

johnbb99

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Nice project and great techniques [the router jig, eg]. [Loved the description of your cable!] If anyone is running any length of cable from amp to driver, I'd recommend something beefy - say 13A mains cable - as the resistance starts to get significant. My understanding is that panel resonances do contribute to colouration [of the sound]. If you can put a second layer on the cabinet walls of different thickness, material, or density so much the better. I built some 'no-trouble-too-much' small cabinets in the 1980s [to handle 100Hz up] out of 1"mahogany. I even melted down some old lead pipe [in a well ventilated area!!], poured it to make sheets, and glued that to the insides of the cabinets!
 

stefan szoka

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I have always thought best to use high density material for speaker cabinets. Thick sheets of lead, concrete, and of course many old speakers were double skinned with sand filling the void. Many years ago when I was in the hi fi trade we sold townshend glastonbury loudspeakers, which were heavy metal cabinets. Must be in the early 70's when the old Belfast sinks were being pulled out of school kitchens and replaced with stainless. I had the idea of fibre glassing a thick sheet of birch plywood into a sink as the baffle board. The wire connections through the plughole. Never got around to building a pair, but some years later there was an article in Hi Fi News building a speaker from a Belfast sink !!
 

Amateur

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In my ignorance can you explain some basics

When you design a speaker how do you know what sort of sound will come out of it?

Why do some speakers cost hundreds of thousands of pounds and are similar looking ones a fraction of the price?

I know it's a huge question but the basics would be help me understand how you arrive at a given design and material selection.
Thanks
 

sploo

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In my ignorance can you explain some basics

When you design a speaker how do you know what sort of sound will come out of it?

Why do some speakers cost hundreds of thousands of pounds and are similar looking ones a fraction of the price?

I know it's a huge question but the basics would be help me understand how you arrive at a given design and material selection.
Thanks
That's a question :)

On a 2-way loudspeaker, the internal volume of the cabinet is essentially for the bass speaker (the treble is a closed unit); so consider it a bit like a subwoofer cabinet.

Based on that - it's generally considered that a larger bass driver will output more lower frequency energy. A sealed cabinet "tunes" the bass driver by acting as an air spring - with smaller volumes generally giving a leaner "tighter" sound, with larger volumes allowing more low frequency extension at the expense of a "looser" sound.

Porting the bass cabinet is more complex, but makes use of the energy coming from the rear of the bass driver to give more output. Depending on the tuning you can get a moderate amount of low bass extension, all the way up to a large spike at a particular low frequency (the kind of "one note" bass you often get in cheap car subwoofer systems).

Audio reviews are like wine reviews frankly (and contain a lot of "plums"), but ported systems are sometimes criticised as sounding "slow" (due to group delay); but there's an argument that it's an invalid perception - just created by the fact there's more low end bass.

The blending of the bass or mid-bass into a treble (for 2-way speakers) is complex; with many different types of filter slope and choice of crossover point. Often one or both drivers will have limitations (e.g. a resonance in the upper part of the mid-bass range) that dictate where you try to blend out one driver in favour of the other. E.g. I'm currently using the sub from this thread with a pair of small bookshelf type speakers - and in reality neither unit is best suited to playing in the 100Hz-200Hz range; so the blending is far from perfect.

The placement of the drivers on the front baffle also matters, as once you get above the lowest bass frequencies the sound energy ceases to radiate all round (like a lightbulb) and starts to beam towards the listener (like a torch). This effect is related to the width of the front baffle, and must be taken into account with baffle step compensation in the crossover - otherwise you'll hear a step up in volume at the baffle step frequency.

As a general rule of thumb; speakers with smaller drivers will produce little low end bass, but with good quality drivers will produce an excellent sound across the midrange to high frequencies. Pushing them hard to create more volume will easily drive them to distortion.

Larger speakers can reach lower (and fill a larger space) but may "boom" in a smaller room.

Cheap drivers tend to produce a lot of distortion - both linear (in that an input frequency sweep at a fixed volume level will produce a varying output volume level at different frequencies) and also non-linear (resonances causing harmonics; e.g. if the driver plays 100Hz there will be some sound produced at 200Hz, 300Hz, 500Hz, etc). Cheap drivers also tend to have very different frequency responses off axis, and because so much of what you hear is sound reflected off walls, floor and ceiling, the quality of the sound produced off axis is really important.

In terms of cost; about 20 years ago I was told (by someone in the industry) that if you saw a £1000 pair of floorstanders in a shop, there would probably be less than £150 in drivers and crossover in the system. The cabinet would also likely be built to a price (using thin chipboard with little bracing).

In theory then, you could increase the retail cost by just a few hundred £ by using a £300 set of drivers and a fairly dense and braced MDF cabinet. However, you wouldn't then sell many of the £1000 speaker, so that better unit would likely be given a wood veneer (for a much more expensive look) and sold for £2000+.

My first set of floorstanding speakers (about 20 years ago) were based on a model from ProAc. All the parts cost around £600, with the ProAc original being in the £3000+ range. Some years ago I spotted a pair of small monitor/bookshelf speakers (at £1000) almost identical (in size and drivers) to a DIY version I'd made for £300.

Down at the budget end it's hard to save money with DIY, as mass produced cheap drivers in little boxes can be made for very little cost, but going up the scale can really save money.

I've barely scratched the surface with that - ignoring passive radiators, 3-way systems, horns, electrostatics, or the single biggest effect on a speaker; the room. But hopefully it was useful.
 

Amateur

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That's a question :)

On a 2-way loudspeaker, the internal volume of the cabinet is essentially for the bass speaker (the treble is a closed unit); so consider it a bit like a subwoofer cabinet.

Based on that - it's generally considered that a larger bass driver will output more lower frequency energy. A sealed cabinet "tunes" the bass driver by acting as an air spring - with smaller volumes generally giving a leaner "tighter" sound, with larger volumes allowing more low frequency extension at the expense of a "looser" sound.

Porting the bass cabinet is more complex, but makes use of the energy coming from the rear of the bass driver to give more output. Depending on the tuning you can get a moderate amount of low bass extension, all the way up to a large spike at a particular low frequency (the kind of "one note" bass you often get in cheap car subwoofer systems).

Audio reviews are like wine reviews frankly (and contain a lot of "plums"), but ported systems are sometimes criticised as sounding "slow" (due to group delay); but there's an argument that it's an invalid perception - just created by the fact there's more low end bass.

The blending of the bass or mid-bass into a treble (for 2-way speakers) is complex; with many different types of filter slope and choice of crossover point. Often one or both drivers will have limitations (e.g. a resonance in the upper part of the mid-bass range) that dictate where you try to blend out one driver in favour of the other. E.g. I'm currently using the sub from this thread with a pair of small bookshelf type speakers - and in reality neither unit is best suited to playing in the 100Hz-200Hz range; so the blending is far from perfect.

The placement of the drivers on the front baffle also matters, as once you get above the lowest bass frequencies the sound energy ceases to radiate all round (like a lightbulb) and starts to beam towards the listener (like a torch). This effect is related to the width of the front baffle, and must be taken into account with baffle step compensation in the crossover - otherwise you'll hear a step up in volume at the baffle step frequency.

As a general rule of thumb; speakers with smaller drivers will produce little low end bass, but with good quality drivers will produce an excellent sound across the midrange to high frequencies. Pushing them hard to create more volume will easily drive them to distortion.

Larger speakers can reach lower (and fill a larger space) but may "boom" in a smaller room.

Cheap drivers tend to produce a lot of distortion - both linear (in that an input frequency sweep at a fixed volume level will produce a varying output volume level at different frequencies) and also non-linear (resonances causing harmonics; e.g. if the driver plays 100Hz there will be some sound produced at 200Hz, 300Hz, 500Hz, etc). Cheap drivers also tend to have very different frequency responses off axis, and because so much of what you hear is sound reflected off walls, floor and ceiling, the quality of the sound produced off axis is really important.

In terms of cost; about 20 years ago I was told (by someone in the industry) that if you saw a £1000 pair of floorstanders in a shop, there would probably be less than £150 in drivers and crossover in the system. The cabinet would also likely be built to a price (using thin chipboard with little bracing).

In theory then, you could increase the retail cost by just a few hundred £ by using a £300 set of drivers and a fairly dense and braced MDF cabinet. However, you wouldn't then sell many of the £1000 speaker, so that better unit would likely be given a wood veneer (for a much more expensive look) and sold for £2000+.

My first set of floorstanding speakers (about 20 years ago) were based on a model from ProAc. All the parts cost around £600, with the ProAc original being in the £3000+ range. Some years ago I spotted a pair of small monitor/bookshelf speakers (at £1000) almost identical (in size and drivers) to a DIY version I'd made for £300.

Down at the budget end it's hard to save money with DIY, as mass produced cheap drivers in little boxes can be made for very little cost, but going up the scale can really save money.

I've barely scratched the surface with that - ignoring passive radiators, 3-way systems, horns, electrostatics, or the single biggest effect on a speaker; the room. But hopefully it was useful.

Thankyou.
I will have to read another couple of times to digest what you have written but I understand the basics a little better.
Again thanks for taking the time to reply.
 
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