Hi from Cambridge, UK

[peteaphid]

Hot on the heels of Oxonjohn, I've just registered with BFM, partly out of a general interest in speaker design, and partly because of a specific requirement. So you've picked up Oxford and Cambridge inside 24 hours!

I'm looking to put together a small PA system for use at parties, both indoors and outside. For outside use, I plan to be able to run it from a leisure battery/car amplifiers, so efficiency is paramount. I recently bought a Carlsbro Slammer II, along with a pair of NlightN flat panel distributed-load loudspeakers, in part because of what I read about the relatively slow dB fall-off with distance of this type of speaker,but also because they're so light and easy to pack. I''m very happy with the NlightNs - they sound very crisp and musical, and have the nice feature of radiating sound in all directions, while only consuming 100W per side:

http://www.gear4music.com/PA-DJ-and-Lig ... r-Each/5X9

Which brings me to my requirement. What I'd like to do is build a couple of BFM folded horns to act as the bass end when running off my van's leisure battery, and be able to put them in the loadspace under the bed to carry them about. This space is just over 17 x 40 x 72" in size, so in a perfect world I'd like the horns to be 16 x 20 x X" in size. looking at the different designs, it would seem the T24s would be ideal, but are a little too wide to fit side by side...which led me to the Tall Auto Tuba (20 x 20 x x16")

So I have 2 burning questions!

1. Can the T24 be built in a different format, say 20 x 30 x 16"?

2. Would the TAT be up to it? If I'm having fun, I might build 4 and array them to get a larger mouth area - perhaps that's the solution?

I'm not in a hurry, and will probably start my build in the spring of next year.

Any thoughts and suggestions welcome!

Pete

[bjm362]

I am new here myself, I can still say hello and wish you the best!
I actually was just about to ask another question in my introduce yourself thread when I saw this!

I haven't built any BF designs yet so I can't add any advice there, but as a former DJ dealing with pro gear in lots of situations I can add my immediate concerns about that advertisements.

1) It does not give you any kind of efficiency rating. The part about very little SPL drop off may be correct, but that is true of my headphones as well. You need to know how loud it is at 1watt/1meter to get an idea of how much space audience size you can play to with it.
2) The description about where it is intended to be used is essentially the same as the smallest version of the Fender Passport system, which by now must people are aware is going to be overstressed at a party in your average living room.
3) They Look similar to planar drivers, which can sound great, but are known to be very power hungry!
If you do purchase that and it turns out to be incredibly amazing I would be interested to know, but it has the look of Buyer Beware written all over it to me personally!

[peteaphid]

Hi there!

I've actually already bought the panel speakers - second-hand - and tested them out in the garden. I'm really impressed, they don't produce the punchy , high-SPL sound of a conventional direct radiator, but the sound fills the space around them and is clear and musical, not at all "foggy". But they're high-passed at 100Hz, so I need some efficient bass bins - BFM folded horns, I hope! - for use when I'm not using the mains-powered Slammer II bass bin which came with them.

I made a mistake in my first post - they're distibuted mode loudspeakers, not distributed load: http://en.wikipedia.org/wiki/Distribute ... oudspeaker and use technology from a company called NXT, although it says "designed and manufactured in England" on them.

Pete

[bjm362]

Hi there!

I've actually already bought the panel speakers - second-hand - and tested them out in the garden. I'm really impressed, they don't produce the punchy , high-SPL sound of a conventional direct radiator, but the sound fills the space around them and is clear and musical, not at all "foggy". But they're high-passed at 100Hz, so I need some efficient bass bins - BFM folded horns, I hope! - for use when I'm not using the mains-powered Slammer II bass bin which came with them.

I made a mistake in my first post - they're distibuted mode loudspeakers, not distributed load: http://en.wikipedia.org/wiki/Distribute ... oudspeaker and use technology from a company called NXT, although it says "designed and manufactured in England" on them.

Pete

Thank you for replying back with both additional theory info as well as corrections! They do look more intriguing now! I still think a 1watt/1 meter efficiency rating to know just how big a space/audience size you can play to with them however.

Like I said though I am new around here, so I don't want to be giving to much advice on a specific build. I can tell you that the audience size ratings Bill Fitzmaurice lists with the info for his plans look pretty appropriate for the types of horns plans they have around here. That is based on actual experience with a variety of similar designs. Good horns used appropriately with an appropriate driver/drivers can reduce the total size and weight of cabinets required to play a space very dramatically. I would expect that at some point very soon some of the guys who have built these and are using them will be around to advise you. Best wishes!

[peteaphid]

I've just found this: http://www.mydukkan.com/urunler_detay.a ... AruSaMzIt0 which includes a slightly mashed up SPL rating - is that 1W or max? - but may give you some idea. My impression is a lot of "presence" for little power.

All the best - and good luck with your builds also!

Pete

[bjm362]

I've just found this: http://www.mydukkan.com/urunler_detay.a ... AruSaMzIt0 which includes a slightly mashed up SPL rating - is that 1W or max? - but may give you some idea. My impression is a lot of "presence" for little power.

All the best - and good luck with your builds also!

Pete

That is the rating we were looking for. With an 1w/1m rating of 90db and a power rating of 100 watts your peak spl should be no more than 110 db. I will post a link to a sound pressure comparison chart. That chart uses a chainsaw at one meter as a comparator for 110 db. If you get 30 people talking softly in room their total volume can be about that loud as well. I am not saying those can't be used at any gig, and adding good subs underneath will help you quite a bit too. However, as far as pay gigs are concerned I hope you are planning to play at some small coffee shops that the audience doesn't talk to each other a lot. They should be wonderful in your living room, or even a backyard gathering of up to about a dozen people or so.
I hope you don't hate me for me being the bearer of bad news. I do think you would be wise to stick around here and learn more before parting with any more cash. The more you know the better decisions you can make. While I am sorry that was bad news, I still hope I was able to help you though. You may have some of the nicest bookshelf speakers made if that is any consolation!
This may be a strange way to try and cheer you up. I will explain why I am here at this forum. I have some bad ass cabinets that work well in many situations. I also am desperately trying to recover from a back injury and I cannot move them. With my life experience in sound, I know that the only way I am going to be able to get out and play again, either as a DJ or as a musician is using horn loaded technology. Since I am injured my finances are going the wrong way, the only way I am going to get suitable components that I can move around is if I build them.This site looks to me to be the most legit thing going. These are tried and true designs and Bill Fitzmaurice publishes actual response curves. He rates the cabinets and combos here to the size of the audience and the skill level required for each one to build. Even provides links to suitable suppliers and a forum for users to exchange information. Either way though, with what you are trying to do, I think you are in the right place too!

Edit: OOPS, I forgot to post the link! http://en.wikipedia.org/wiki/Sound_pressure

[peteaphid]

Thanks again for your interest and advice. I think, in practice, the panels will be fine for my purposes, as their omnidirectional output and slow dB falloff is ideal for outdoor environments. As I mentioned, I've checked them out in my garden and think they're fine. I just need some efficient bass. I too have done my back in, and can't carry my own kit around - a few K's worth of conventional gear. And none of this is commercial, it's just me and friends making a noise and dancing the night away!

[bjm362]

Thanks again for your interest and advice. I think, in practice, the panels will be fine for my purposes, as their omnidirectional output and slow dB falloff is ideal for outdoor environments. As I mentioned, I've checked them out in my garden and think they're fine. I just need some efficient bass. I too have done my back in, and can't carry my own kit around - a few K's worth of conventional gear. And none of this is commercial, it's just me and friends making a noise and dancing the night away!

I, didn't say they wouldn't gig at all. You and I are both saying the same thing essentially ....I think. I was just going in long form explaining the why's ! My bad! I may have overstated the limitations just a bit, but how you use them can also dramatically effect the size of audience. Vocals only or light music in the back yard they should be awesome! Especially with good subs for support in the music situation!
P.S. Please do let me know how they wind up performing in live situations! I hope they wind up working not only better than I expect, but also better than you expect!!!! Please pardon me for being skeptical about the long throw ability of the design. It is just I have experience being able to rely on the efficiency standards, so it is hard to just toss it out the window!
Again, best of luck!

Edit, I am surprised that some of the more experienced builders haven't responded to this yet. Hopefully they will SOON, but I believe you mentioned you were not in a hurry. That can be a very good thing in itself!

[peteaphid]

No need to say sorry - no offence taken! Once it's all up and working I will, no doubt, let everyone know how it sounds. I'll primarily be using it to play old psychedelic/post-punk/krautrock and the like, with some electronic music thrown in, but I'm not expecting to rinse out breaks for hours at a time - that's for the bigger kit.

Yes, has anyone got any thoughts on my original post, re: T24s or TATs?

[Chris_Allen]

Hi and welcome to the forum.

To change the dimensions of the T24, you would have to refold it which is a mammoth job.

The problem with the TAT is the driver and the amount of displacement, you can't get one that can take the punishment intended for non cabin gain environments (not in your front room and not in the car).

The dimensions you mention do lend themselves to the T39 @ 39" x 19.5" x width.

[DJPhatman]

T45.

[Grant Bunter]

Hello and welcome

in part because of what I read about the relatively slow dB fall-off with distance of this type of speaker

You can't change physics.
The rate of fall off is 6dB with each doubling of distance.
So, at 2 metres, you are 6dB down from the reading at 1 metre. And so on.
Nothing can slow that down.

A 16" wide T24 is 16 wide x 24 high x 24 deep.
If you have 17 x 40 x 72", then 2 x T24 side by side would be 16 x 24 x 48" more or less.

If your tops have 90db/1m response, then no need to go with the 3010lf driver option either.
BP102 loaded would be fine and require less power at max output...

[Bill Fitzmaurice]

The rate of fall off is 6dB with each doubling of distance.

It's 3dB with a line array, based on the height of the line, frequency and distance from the line. But flat panels aren't line arrays, and will adhere to the usual 6dB rule.

[peteaphid]

Thanks everyone for all your suggestions - i'll have to work through them now...

Chris - a bit gutted about the TAT unsuitability, but very glad I now know

DJPhantom - I think the T45 is overkill for me, as the thing will have to live in my small house most of the time, and I can't pick up heavy speakers due to having a duff back. The same could be said for the T39, although its taller profile is attractive.

Grant - I'm coming around to the idea of building just one T24 to start with, and leave the second till later, if ever. The problem with two would be using so much of my loadpace up, leaving little room for the panels, stands and other gear we'd be taking to the party.

And finally there's the issue of dB fall-off - irrelevant to my build, perhaps, but interesting! I can't claim to know much about these things, but I was basing my belief on this from Wikipedia:

Less fading with distance. (For example, at 3.5 meters distance, whereas fading would be 4dB for a DML, a comparable dynamic moving coil loudspeaker would exhibit 11dB fading, compared to the signal level at 1 meter.)

Unreferenced, I know...but I wonder, could it be that the v large radiating dimensions of my panels (26 x 18") means that near field behaviour extends to a much greater distance, giving them quasi-line array behaviour? They certainly sounded different when I tried them in the garden, but maybe I was kidding myself, due to what I'd read. I'm happy believing the wavefront is somewhere between cylindrical and spherical

[Bill Fitzmaurice]

could it be that the v large radiating dimensions of my panels (26 x 18") means that near field behaviour extends to a much greater distance, giving them quasi-line array behaviour?

No more so than any other speaker of similar dimension.