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bootsy666

Custom 8x15 bass cabinet

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[quote name='planer' timestamp='1429391151' post='2751089']
This is turning into an epic build thread :-)

I can't wait to see and, given our apparent proximity, probably hear the finished beast!

Good on you for building something wild, it's a corker.
[/quote]
Do you live near shoreham?

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[quote name='bootsy666' timestamp='1429469807' post='2751693']
Besides technical stuff, I've brought some good quality black leatherette, I used the same stuff to wrap my vba400 in and it came out quite nice.
I did plan on using it on the front baffles only before the speakers go in, but I'm having second thoughts now.
I guess I could always remove it if it doesn't look right.
[/quote]

Tuffcab is your friend (or even black paint on the baffle).

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[quote name='bootsy666' timestamp='1429469857' post='2751695']
Do you live near shoreham?
[/quote]
I work at Shoreham airport. Sometimes it just [i]feels[/i] like I live there!

Edited by planer

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[quote name='bootsy666' timestamp='1429375182' post='2750945'] Someone told me once that a 200 watt valve amp was the equivalent of a 1000watt solid state. If that's true then the vba could handle a 2000 watt cab, that's one of the reasons for making the cab 2000watts. I currently have a quad of 6550A valves in it, but u also have a set of brand new sovtec KT88 Russian valves sat in my garage waiting to be used. I wanted to hear the 6550's with this cab before changing them tho. [/quote]

It isn't true. As far as the speakers are concerned the valve watts are the same as any other watts, a measure of the electrical energy going into your speakers, nothing magical about them. The reason for valve amps sounding louder is well understood, simply put valves and transistors can both be driven into overload, the loudest bits of your bass are easily 20dB (100 times) the average you are playing at so if you are playing an average 10W then the loudest bits will be distorting. With valves the distortion sounds Ok and you can turn the amp up even more, with more nice distortion. Transistor/solid state amps sound poor and worse as you turn them up from this point and so in practice you don't. The upper power is still 200W or whatever but the average power is reduced because of the horrible distortion.

I'm probably one of the 'experts'. I hadn't commented because the advice you've been getting is good. Now I'm on I cant resist any more :)

Your design is bonkers from a practical and technical point of view but looks like fun. Your speaker will work though and give you a different sound. With all those cones it is going to be very loud and very bassy sounding. There wont be as much deep bass as high bass but with a restricted top end and a fairly sizeable peak around the 100-150Hz range you won't be disappointed with the perceived response. You really aren't going to have to worry about power handling though 200W through these guys is going to be too loud for the band and audience to bear in any enclosed space.you are likely to play. That's 25W per speaker which means they'll probably outlast you and certainly outlast your hearing!

The only poor advice is from Celestion, I wonder if you spoke to the Saturday staff. The ports will make almost no difference to speaker cooling as the air in them just vibrates back and to at most frequencies, very little air flow will occur when they are being used so no worthwhile cooling will happen. The ports are there to tune the cab, since you've not done anything else technically correct why bother with an added complication which won't cool your speakers. I'd block the ports. If you are going to keep them then put them on the back and make them big, at least as big as Alex (I think) said. Lots of 4" pipes.

Some 'experts' forget that a technically optimised speaker isn't necessarily going to sound the best. You are going to end up with a huge speaker that will sound like almost nothing else but be a talking point at every gig you take it to, people will come just to see the mad speaker, not a bad thing for any band. you could doubtless achieve a very similar sound at a fraction of the cost with a couple of 15's in a well designed cab using eq for the tone and a more powerful amp but this is a fun project which will give you a massive retro sounding cab, if you can afford it and are happy to move the thing then enjoy. Just because you can :)

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[quote name='Phil Starr' timestamp='1429513615' post='2752003']
people will come just to see the mad speaker
[/quote]

This is true...I would go and see your band just to see it in action.

I think it's clear from the advice of Bill, Alex and others who really know their sh*t with cab design (you can disagree as much as you like with them but that won't change the fact that they are right) that this cab isn't going to be functioning at anything like optimum perfomance levels. But... as proposterous as it is it will be a talking point and I think you should just go ahead and make it anyway :) its all very spinal tap...

Edited by CamdenRob

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[quote name='Phil Starr' timestamp='1429513615' post='2752003']


It isn't true. As far as the speakers are concerned the valve watts are the same as any other watts, a measure of the electrical energy going into your speakers, nothing magical about them. The reason for valve amps sounding louder is well understood, simply put valves and transistors can both be driven into overload, the loudest bits of your bass are easily 20dB (100 times) the average you are playing at so if you are playing an average 10W then the loudest bits will be distorting. With valves the distortion sounds Ok and you can turn the amp up even more, with more nice distortion. Transistor/solid state amps sound poor and worse as you turn them up from this point and so in practice you don't. The upper power is still 200W or whatever but the average power is reduced because of the horrible distortion.

I'm probably one of the 'experts'. I hadn't commented because the advice you've been getting is good. Now I'm on I cant resist any more :)

Your design is bonkers from a practical and technical point of view but looks like fun. Your speaker will work though and give you a different sound. With all those cones it is going to be very loud and very bassy sounding. There wont be as much deep bass as high bass but with a restricted top end and a fairly sizeable peak around the 100-150Hz range you won't be disappointed with the perceived response. You really aren't going to have to worry about power handling though 200W through these guys is going to be too loud for the band and audience to bear in any enclosed space.you are likely to play. That's 25W per speaker which means they'll probably outlast you and certainly outlast your hearing!

The only poor advice is from Celestion, I wonder if you spoke to the Saturday staff. The ports will make almost no difference to speaker cooling as the air in them just vibrates back and to at most frequencies, very little air flow will occur when they are being used so no worthwhile cooling will happen. The ports are there to tune the cab, since you've not done anything else technically correct why bother with an added complication which won't cool your speakers. I'd block the ports. If you are going to keep them then put them on the back and make them big, at least as big as Alex (I think) said. Lots of 4" pipes.

Some 'experts' forget that a technically optimised speaker isn't necessarily going to sound the best. You are going to end up with a huge speaker that will sound like almost nothing else but be a talking point at every gig you take it to, people will come just to see the mad speaker, not a bad thing for any band. you could doubtless achieve a very similar sound at a fraction of the cost with a couple of 15's in a well designed cab using eq for the tone and a more powerful amp but this is a fun project which will give you a massive retro sounding cab, if you can afford it and are happy to move the thing then enjoy. Just because you can :)
[/quote]
Thanks!

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[quote name='Phil Starr' timestamp='1429513615' post='2752003']
Just because you can :)
[/quote]

I have read the whole thread, and this line sums up my thoughts completely.

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[quote name='amnesia' timestamp='1429531093' post='2752270']
I have read the whole thread, and this line sums up my thoughts completely.
[/quote]

I have to say it sums up quite a lot of things on here as well.

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[quote name='bootsy666' timestamp='1428956031' post='2746457']
I've built a custom 8x15 bass cab over the last 2 weeks. I'm very happy with it, but I'd like some advice on venting. it has six 2" holes in the front, anyone think I should add a few more?
The speakers that I've ordered are celestion TF1525.
[/quote]

You are my new Hero.

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That looks like a whole lot of fun!! Go for it bootsy! I'm in the "Do it because it's fun and you'll learn a heap from doing it" camp. Think the cab looks great and will definitely be a major talking point at any gig, plus it's obvious your heart is really in this project and you should see it through.

Having seen how sometimes threads like these in recent times can go a bit south, I just feel it's important to mention that when people like Bill Fitzmaurice or Alex Claber or anyone else at an "expert" level comes on to a thread like this and contradicts what you are doing, try to remember that even though some of the advice may sound a bit harsh or critical, they are giving professional advice for free that they don't have to give. It doesn't mean that they should be treated like Royalty and we should doff our caps to them, but they don't really have time to spend composing their posts to give it a non-offensive feel. We do need to remember they actually know and understand what they are talking about and giving that advice for free.

I think it's good that they offer their honest advice as there is no point them coming on a thread and cheering you on as you spend a fair chunk of money, whilst they might chuckle to themselves thinking "this will never work". I think it's really good that they are offering their honest opinion, whilst their idea of what a cab should be might differ greatly from what you have imagined with this project.

It's great that you are seeing this through and wish i lived close enough that I could come and hear it and feel what it's like as my internal organs all rupture at the same time!

I really hope this hasn't come across in a patronising way, I just thought it was important to say in a friendly way.... God forbid this thread would go in the direction of the fabled "compression" thread of doom!

Edited by The Badderer

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[quote name='The Badderer' timestamp='1429834030' post='2755497']
That looks like a whole lot of fun!! Go for it bootsy! I'm in the "Do it because it's fun and you'll learn a heap from doing it" camp. Think the cab looks great and will definitely be a major talking point at any gig, plus it's obvious your heart is really in this project and you should see it through.

Having seen how sometimes threads like these in recent times can go a bit south, I just feel it's important to mention that when people like Bill Fitzmaurice or Alex Claber or anyone else at an "expert" level comes on to a thread like this and contradicts what you are doing, try to remember that even though some of the advice may sound a bit harsh or critical, they are giving professional advice for free that they don't have to give. It doesn't mean that they should be treated like Royalty and we should doff our caps to them, but they don't really have time to spend composing their posts to give it a non-offensive feel. We do need to remember they actually know and understand what they are talking about and giving that advice for free.

I think it's good that they offer their honest advice as there is no point them coming on a thread and cheering you on as you spend a fair chunk of money, whilst they might chuckle to themselves thinking "this will never work". I think it's really good that they are offering their honest opinion, whilst their idea of what a cab should be might differ greatly from what you have imagined with this project.

It's great that you are seeing this through and wish i lived close enough that I could come and hear it and feel what it's like as my internal organs all rupture at the same time!

I really hope this hasn't come across in a patronising way, I just thought it was important to say in a friendly way.... God forbid this thread would go in the direction of the fabled "compression" thread of doom!
[/quote]
Much appreciated mate. The advice on here has been very helpful.

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[quote name='VTypeV4' timestamp='1429827094' post='2755453']
Can we have some more pix, please? :rolleyes:
[/quote]
Soon. I've made a few alterations to the ports and apearance.
It's just finding the time to get it done, I'm mega busy at work right now.

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[quote name='alexclaber' timestamp='1429371641' post='2750912']
You're only using a 400W amp with them and the drivers will each handle 250W thermally - so 2000W total. Heat definitely isn't an issue, whatever Celestion say!

You can definitely rear port them but you need to get the size/lengths right or you'll end up tuned too high which will kill off your deepest lows. As soon as you make the holes bigger you have to add length to keep the tuning frequency the same.
[/quote]
I'm still in decided on front or rear porting after reading all the useful advice on here? I Might break the rules even more and try front and rear porting together.
I've never seen or heard a cab with both, and I'm guessing there's a reason for that?
I think I will find some trong thick foam and use it to plug some while testing to see which ports I should keep?

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You can put the ports wherever you like, it doesn't change the sound once you're anywhere other than right next to the cab. The Acme Low-B4 has front and back ones. On our Super & Big 12XN cabs we have them at the front whilst on our Retro 10CR cabs we have them at the side or on the bottom.

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[quote name='alexclaber' timestamp='1429881150' post='2755950']
You can put the ports wherever you like, it doesn't change the sound once you're anywhere other than right next to the cab. The Acme Low-B4 has front and back ones. On our Super & Big 12XN cabs we have them at the front whilst on our Retro 10CR cabs we have them at the side or on the bottom.
[/quote]
How do they sound when stood next to one? I find that un like most people I can realy hear the diffirence between front and rear ports, I think that front ports sound a lot better for the style of music I play.
I'm going to try four 2" ports on the front, one between each set of speakers. And four 3" on the rear panel across the bottom with long tubes. Or maybe they should be 4"?

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[quote name='bootsy666' timestamp='1429884439' post='2755988']
I'm going to try four 2" ports on the front, one between each set of speakers. And four 3" on the rear panel across the bottom with long tubes. Or maybe they should be 4"?
[/quote]

From a pragmatic point of view, if you do decide to tune them 4" gives readily available drainpipe. This then makes changing the length a cheap proposition if 'bought' port tubes are not long enough. Marshall DBS 2 x 15 that I once had for a while had 2 x 4" ports on the back (from memory).

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Go for it! Just take in consideration this advice from Alex, regarding the ports:

[quote name='alexclaber' timestamp='1429101737' post='2747988']
I just quickly modelled your 8x15" cab: From 100Hz downwards it's of pretty much equal sensitivity to our Retro Six10, which can do fairly offensive levels of bass! :)

[b]It does need bigger ports[/b] - at the moment they'll start distorting pretty badly with about 50W.[b] Six 4" ones 6" long will be fine.[/b] If you want maximum bass then replace the slanted baffles with one straight baffle for four 15"s and build another box the same size for the other four 15"s. One cab that size with four 15"s will do more bass than the 8x15" - the speakers have room to 'breathe' like that.
[/quote]

I hope i'll be able to hear it over here, ahaha ;)

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[quote name='3below' timestamp='1429892549' post='2756122']


From a pragmatic point of view, if you do decide to tune them 4" gives readily available drainpipe. This then makes changing the length a cheap proposition if 'bought' port tubes are not long enough. Marshall DBS 2 x 15 that I once had for a while had 2 x 4" ports on the back (from memory).
[/quote]
Drainpipe? How would I seal it to the surface?

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[quote name='bootsy666' timestamp='1429884439' post='2755988']
How do they sound when stood next to one? I find that un like most people I can realy hear the diffirence between front and rear ports, I think that front ports sound a lot better for the style of music I play.
I'm going to try four 2" ports on the front, one between each set of speakers. And four 3" on the rear panel across the bottom with long tubes. Or maybe they should be 4"?
[/quote]

No-one can hear the difference between port placement when they're done right - the frequencies are so low that they blend seamlessly with what's coming out of the woofers. Done wrong and you get mids & even treble coming out, and port air noise and so on, which you hear.

Have a read of this if you want to understand what ports are for and what they're actually doing: http://barefacedbass.com/technical-information/the-mysteries-of-ports.htm

Silicone sealant (neutral cure) is pretty effective at holding a plastic port tube in place if the joint is nice and tight and has plenty of surface area.

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Just so you know.

You need big ports because they need to shift a certain amount of air, equivalent to the air moved by all the cones put together. Moving that much air through a tiny hole will make wind noises.

The ports are there to tune the cab to something close to the resonant frequency of the speakers. Just putting in random holes might tune the cab to a frequency which is pointlessly too high or too low. You might as well not bother which is why I suggested leaving them out. If you do want to tune the cab and get a bit of extra bass then use ports the size Alex has suggested. 4" drainpipe ( actually soil pipe) is easy to cut and you can fix it in place with silicone or other mastics, even if the hole you cut is a bit iffy.

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[quote name='Phil Starr' timestamp='1429900666' post='2756238']
Just so you know.

You need big ports because they need to shift a certain amount of air, equivalent to the air moved by all the cones put together. Moving that much air through a tiny hole will make wind noises.

The ports are there to tune the cab to something close to the resonant frequency of the speakers. Just putting in random holes might tune the cab to a frequency which is pointlessly too high or too low. You might as well not bother which is why I suggested leaving them out. If you do want to tune the cab and get a bit of extra bass then use ports the size Alex has suggested. 4" drainpipe ( actually soil pipe) is easy to cut and you can fix it in place with silicone or other mastics, even if the hole you cut is a bit iffy.
[/quote]
Ok. I think for the first time on this project I will use the advice given to me and go with 4" ports. I'll block the ports in the front and only use the rear. I'll have a look at some drainpipe tomorrow and see if it's worth doing.
I've found some adjustable 4.5" screw fixed ports on eBay that I can buy if not.

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