Choosing drivers for a given enclosure and desired sound.

[nat8808]

I've a little project to get on with.

Been enjoying my Celestion SL700s - nice natural sound, great feeling for soundstage - but my Acoustic Energy AE2 Pros have a tactility (speed of driver?) that I miss..

So, in the vein of the SL700s, I saw some Celestion Kingston cabinets for sale and bought them! The Kingstons were supposed to improve upon the SL700s in many areas whilst keeping some of their strengths.

Anyway...

How does one go about choosing drivers for a given cabinet design, shape, construction and volume?

Does it end up as a case of taking a chance on some that have worked in other designs and the rest is down to the cabinet design (fixed) and crossover? And a lot of trial and error?

Or is there a way of working out what will work?

When I read threads on say DIYaudio.com, it seems people have some idea of a pair of drivers they want to use together first, then come up with a cabinet and cross-over design afterwards - like geek gear lust over the drivers happens first.

Also, what kind of driver property will give a "tactile" sound? What I mean by this is that something sounds so real in terms of immediacy of sound that it could be there in the room - kind of no veils infront. Is it it a dynamic ability, an ability to push the air quickly from a standstill without flapping about - stiff cones and big magnets/coils? Or simply it's down to everything - the overall result and can't be attributed to drivers alone?

Having said that, it would be best to find a mid at least that fits the mounting holes that are already there - might restrict things quite a lot.

Anyway, any help would be appreciated.

Easy way out would be to buy some Celestion A100s as I think they have the same drivers.. but I'd like to push them further, treat the cabinets to modern drivers.

[Toppsy]

How does one go about choosing drivers for a given cabinet design, shape, construction and volume?

It aint as simple as that.
First you will need to get to grips with the likes of WinISD or similar free download speaker design software. http://www.linearteam.dk/ Or you could start here: http://www.mh-audio.nl/spk_calc.asp You will need to input all the theile parameters into the program for your drivers to get a suitable cabinet volume after choosing which type of cabinet alignment you want.

If you are intending on a multi-way design you'll then have to get to grips with crossover designing. A minefield in it's own right. Again there are free software download programs on the web. try here http://www.diyaudioandvideo.com/Calculator/XOver/ or for a 3-way design here: http://www.diyaudioandvideo.com/Calculator/APCXOver/

Good luck. It has taken me about 3-years to get confident with speaker design and then I'm still a relative novice at it.

[Welder]

http://www.speakerworkshop.com/

http://www.linearteam.dk/default.aspx?pageid=winisd

my preference
http://www.gedlee.com/speak.htm

Good quality drivers are expensive and yes you can notice the difference.
For Bass and mid-range my preference is still for paper cone with fairly steep angle, long pole, narrow coil to pole gap with minimum voids and powerful magnets.
For high range, I much prefer silk domes with ferro fluid cooling, they just seem easier on the ears.

You can’t just swap drivers around in a pre built enclosure and expect to get a decent sound. If you change the driver, the probability is you’ll need to adjust the crossover.
You can’t do this by ear, you have to measure and there is a lot to measure, including the impedance curve of your driver.

Once you’ve built the speaker and achieved the best measurable performance then comes the listening and adjustment bit. A completely flat response does not necessarily make for the best listening experience.

Proper cabinet construction will make a much larger difference to a driver’s performance than the average loudspeaker design would have one believe. For drivers in a box you just can’t have an over build enclosure. Yep, I know what those who are fans of the floppy BBC style resonating cabs believe. In the vast majority of builds I think they are wrong; the physics just doesn’t make sense.

[Daniel Quinn]

Whilst I wouldnt disagree with anything said above , I do think there is a tendancy to overcomplicate , part of the fun is trust trying things . There are plent of reasonably priced drivers on ebay you could look at and not so inexpensive that a mistake would matter much . I did exactly like you bought a cabinent and then set about placing drivers in . The crossover was a ball ache to my none technical brain , again I bought completed crossovers and parts of ebay and just experiemented by ripping then apart and swapping and changing , in the end -thanks to a suggestion from Mr Dunn , I foresake a crossovers except capacitor and resistor on the tweeter and blocked up the port and wired in series not parrallel the results were excellant .

I do however note the cabinent you have bought is a special polymer [alpha crystal ] and I wouldnt have thought there was to much scope for additional bracing or modificiations . So you couild contact Wilmslow Audio with the dimensions of the cabinent , internal volume etc and they will offer a suggestion of drivers and appropriate crossovers at various price points or a design schemaitc for a charge . Drivers are fairly standard in size so I wouldnt have thought you would have to mcuh trouble find appropraite sizes .

[nat8808]

Whilst I wouldnt disagree with anything said above , I do think there is a tendancy to overcomplicate , part of the fun is trust trying things . There are plent of reasonably priced drivers on ebay you could look at and not so inexpensive that a mistake would matter much . I did exactly like you bought a cabinent and then set about placing drivers in . The crossover was a ball ache to my none technical brain , again I bought completed crossovers and parts of ebay and just experiemented by ripping then apart and swapping and changing , in the end -thanks to a suggestion from Mr Dunn , I foresake a crossovers except capacitor and resistor on the tweeter and blocked up the port and wired in series not parrallel the results were excellant .

I do however note the cabinent you have bought is a special polymer [alpha crystal ] and I wouldnt have thought there was to much scope for additional bracing or modificiations . So you couild contact Wilmslow Audio with the dimensions of the cabinent , internal volume etc and they will offer a suggestion of drivers and appropriate crossovers at various price points or a design schemaitc for a charge . Drivers are fairly standard in size so I wouldnt have thought you would have to mcuh trouble find appropraite sizes .

This is my take but comes from my technical ignorance but being practically minded and being bogged down in thoughts too often that just make you freeze - "am I making the right choice here?" etc.

This 'Alpha Crystal' is kind of Celestion's way of making it sound like they'd invented it... In the real world it is called Jesmonite (the trade name) and can be bought from art and theatre suppliers - good for making sets look like marble for example and is non-toxic too. I bought some cos I wanted to make both a turntable plinth from it and design a speaker like the Kingston.

Thanks for the tip about Wilmslow Audio - they might have something they can run the dimensions into and advise drivers.

[nat8808]

http://www.speakerworkshop.com/

http://www.linearteam.dk/default.aspx?pageid=winisd

my preference
http://www.gedlee.com/speak.htm

Good quality drivers are expensive and yes you can notice the difference.
For Bass and mid-range my preference is still for paper cone with fairly steep angle, long pole, narrow coil to pole gap with minimum voids and powerful magnets.
For high range, I much prefer silk domes with ferro fluid cooling, they just seem easier on the ears.

You can’t just swap drivers around in a pre built enclosure and expect to get a decent sound. If you change the driver, the probability is you’ll need to adjust the crossover.
You can’t do this by ear, you have to measure and there is a lot to measure, including the impedance curve of your driver.

Once you’ve built the speaker and achieved the best measurable performance then comes the listening and adjustment bit. A completely flat response does not necessarily make for the best listening experience.

Proper cabinet construction will make a much larger difference to a driver’s performance than the average loudspeaker design would have one believe. For drivers in a box you just can’t have an over build enclosure. Yep, I know what those who are fans of the floppy BBC style resonating cabs believe. In the vast majority of builds I think they are wrong; the physics just doesn’t make sense.

I do actually have some tweeters - Scanspeak 97000s. I picked up 3 for £80, used on ebay about 4 years ago to replace the tweeters on some Kef 107s as they have the same mounting as a Kef T33 and similar impedance plots (as if they were designed as a direct replacement). I also have a pair of ribbon tweeters, same as would be on a pair of ProAc Future 1s. Both I think may be too deep for mounting area on the cabinets - the original speakers would have had a slightly curved front baffle (not on these empty cabs) so perhaps I could make something to accomodate the Scanspeaks.

Cabinet is already built but despite the claims of innertness by Celestion, it is still a uniform material and bongs - slightly like a damped ceramic pot. There is room for improvement and I'm sure bracing could be set up inside.

I do imagine that the cross-over/driver interaction will be the most fiddly bit.

I could cop out and find a pair of Celestion A100s - I believe they use the same drivers in a wooden cabinet, like SL6s were to the SL600. Wanted to improve things though if possible.

[nat8808]

It aint as simple as that.

Aarrgh! Don't say that...

First you will need to get to grips with the likes of WinISD or similar free download speaker design software. http://www.linearteam.dk/ Or you could start here: http://www.mh-audio.nl/spk_calc.asp You will need to input all the theile parameters into the program for your drivers to get a suitable cabinet volume after choosing which type of cabinet alignment you want.

If you are intending on a multi-way design you'll then have to get to grips with crossover designing. A minefield in it's own right. Again there are free software download programs on the web. try here http://www.diyaudioandvideo.com/Calculator/XOver/ or for a 3-way design here: http://www.diyaudioandvideo.com/Calculator/APCXOver/

Good luck. It has taken me about 3-years to get confident with speaker design and then I'm still a relative novice at it.

Fortunately the cabinet is already built... That would involve too many variables otherwise.. although I would like to make some curved floorstanders one day.

Thing is, I see people like Hart Audio finding a brass speaker enclosure (I started a thread about it) on ebay, ex-B&W design, taking just a few weeks to stick some drivers in with a cross-over and then ask £10,000 for them. Now that could just be BS but there must be a certain level of sound quality to even consider the possibility of selling them at a price higher than others in your range. Therefore, perhaps you don't need such complexity and over-thinking?

Will the programs you've mentioned above do things the other way around? Enter enclosure details and get a range of Theile / Small parameters (I added in the "Small" as it rang a bell in this context - a bluff!)

[nat8808]

As an additional question - on the revelation that I alread have some Scan Speak 97000 tweeters (should they fit) will Scan Speak already have a mid/bass driver that suits their own tweeter and so much easier to integrate?

Are drivers from the same manufacturer the best bet?

[Reid Malenfant]

As an additional question - on the revelation that I alread have some Scan Speak 97000 tweeters (should they fit) will Scan Speak already have a mid/bass driver that suits their own tweeter and so much easier to integrate?

Are drivers from the same manufacturer the best bet?

You could go that route, some manufacturers go to reasonable lengths to get a mid/bass unit to integrate with a tweeter using as simple a crossover as possible by building it to roll off it's upper response in a controlled way.

Dynaudio drivers spring to mind in that category.


Overall it sounds like you want to take a few factors into account when you choose a driver. You say you want "immediacy" so I'd tend to steer clear of polypropylene coned drivers. Your best bet if you like what the AEs do is to look for a good quality metal coned driver as that is what the AEs use.

Scanspeak make some very high quality Magnesium coned bass/mid drivers, though they aren't exactly cheap. Another alternative & cheaper, but still rather good may be take a look at some of the aluminium coned drivers made by either Visaton or dare I say it HiVi.

The problem you may well have using a metal cone is you'll probably need to use a steep low pass filter for the crossover to avoid the effects of cone breakup & the resultant resonances that tend to be produced.


At the bass end don't consider any bass/mid with a total driver Q (QTS) of above 0.4 0.4 & below will mean the driver can be used in either a sealed box or a reflex without too much overhang. It'll be well damped, though if you do intend to make some kind of reflex enclosure I'd suggest you look for a driver with a QTS of no higher than 0.33 in reality. The lower the QTS, the more control the amplifier will have over the cone & it'll start & stop faster.

As it's likely to be small, 5" to 7" or maybe 8" at a push with a two way speaker I'd suggest you don't go below a QTS of 0.3 as you'll lose too much deeper bass due to it rolling off.

Clever enclosure design can help out here though, you can use room boundaries to incease the deep bass you'd get from the port to create a flatter in room response.

[nat8808]

In brief though, could I choose any tweeter/woofer pairing (that work well together) and adjust the crossover for the cabinet/driver combo or do I have to match the drivers to the cabinet?

Is it only bass resonance that I need to match up with the drivers?

The Kingston cabinets are sealed designs with a tapered rear.