tweeter advice

[NED 209]

hi all . i recently won a set of beyma 102nd speakers on ebay. im gonna build a diy boombox (another one ) with them.
theyre rated at 103db, so i was tryina find tweeters to match them. im a novice at this stuff. i liked these, because theyre light, 600 grams or so, which is ideal.

http://cgi.ebay.com/Eminence-Supert...ZWD1VQQ_trksidZp1638.m118.l1247QQcmdZViewItem

theyre rated at 105db. is this a total mismatch, or, will a decibel or so in the difference affect how they sound together?

big thanks,
ned .

 

[Cal Weldon]

Hi Ned,

The Beyma is a mid bass unit so you will need a woofer to go with it. The only frequency chart I could find only went to 2kHz so we can't be sure of the overlap with the tweeter. Also being 10" means the beaming and cone break up might be a problem below the intended XO point of the tweeter.
The sensitivity rating of the tweeters is with their particular horn so it might be lower with whatever horn you choose.
The difference in level can be adjusted with a L-pad.
The sensitivity rating of the mid bass might be fudged a little but again the tweeter can be adjusted to suit.

I trust this is for some sort of PA or outdoor use? This isn't Hi-Fi stuff, it's designed for volume, not accuracy.

 

[NED 209]

that is correct. thanks for the advice

 

[Cal Weldon]

No problem, I misunderstood. I thought you were going to try and use the Beyma for a boom box, my mistake, good luck with the project.

 

[NED 209]

no no, sorry, you were correct, im going to build a nasty boombox, ghettoblaster, portable radio. hook an mp3 player into an amp32. i was thinking with this speaker i could produce lots of volume for a long time, on one battery charge. but you reckon ill need another woofer, im hearbroken it just wont put out enough bass?

 

[Cal Weldon]

No sir. It's called a mid bass but I question that. It's already down about 27 dB at 100 Hz so this I believe should be thought of as a midrange even though it has an Fs of 57 Hz. That means you would need a huge amplifier and an EQ to get any low end from it, but with a 2mm Xmax, it ain't gonna happen.

 

[NED 209]

damn. thanks for the info

 

[ScottG]

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=294-600

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=270-310

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=300-560

 

[NED 209]

Thanks for that Scott. im always apprehensive about starting threads on here cos my level of knowledge is very poor. so far its been unfounded though cos ye've all been super helpful.

ok, scrap those woofers. i want low end, i want xmax.

can anyone suggest 10 inchers that would suit this project? ive noticed that drivers made for several hundred watts have huuge heavy magnets, whereas, some drivers made for only 20 - 80 watts are pretty efficient with only small magnets.

i guess, maybe the 102s were a good place to start, because i had braced myself for their 3.5 kg weight, so now the field is pretty open


id like to keep it a two way system

 

[ScottG]

I wouldn't scrap those woofers.. but for this project its perhaps a no-go.

Start off with Hoffman's Iron Law for your design to recognize your basic trade-offs with respect to efficiency, cabinet size, and low freq. performance:

http://ldsg.snippets.org/appdx-a.php#HOFFMAN

 

[NED 209]

cool, thats well written, ill get into it. in the meantime, i wanted to mention that i have a set of these too

http://www.wholenote.com/item--MF.660266

would they be any more suited?

 

[Cal Weldon]

Those are better as they are a bass guitar speaker. They will still need some EQ to fill in the bottom end though, and you're not likely to get much below 75 Hz.

 

[NED 209]

is there a computer program that'll let me listen to the difference between 40 and 80hz?

thats good news.. i have the dimensions from celestion to build a box for them -

A suitable size for the BL10 is 25 litres tuned to 60Hz using a vent
with diameter 63mm and length 60mm. 25litres gives you a good compromise
between bottom end and portability.
Regards
The Doctor

 

[ScottG]

cool, thats well written, ill get into it. in the meantime, i wanted to mention that i have a set of these too

http://www.wholenote.com/item--MF.660266

would they be any more suited?

again, nice drivers - but not really suitable for what you want here (..and I don't think you will find anything suitable for what you want).

Try playing with the basic version of WinISD (freeware).. placing in the drivers T/S parameters to see what kind of low freq. performance you can get for your interested driver.

I think you'll find that high efficiency with low freq. performance requires a LOT of cabinet volume.

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

Then you have the problems associated with 2 ways and center-to-center distance between your tweeter and your driver.. for that problem look to coaxial drivers.

Finally you have baffle step loss.

http://www.t-linespeakers.org/tech/bafflestep/index.html

..you can model for free with the Edge.

http://www.tolvan.com/edge/

The best solution I could find was:

Beyma 8BX in just over a cubic foot of cabinet volume tunned to 40 Hz, (3 inch diameter vent about 9 inches in length), with just about every aspect taken care of ..i.e. no substantial need for baffle step compensation with this driver and that reflex design. (..and I think they have a recommended crossover).

 

[NED 209]

very nice of you! i was liking the idea of 10 inch drivers... i know a lot of you put mad workmanship into the appearance of cabinets, well in this case im gonna go all out to make this look... egotistical... like the 80's boxes. and bigger drivers = more visual impact.


ill look into the beyma 8BX's

did i mention i also have ciare ch250's in transit,

 

[ScottG]

very nice of you! i was liking the idea of 10 inch drivers... i know a lot of you put mad workmanship into the appearance of cabinets, well in this case im gonna go all out to make this look... egotistical... like the 80's boxes. and bigger drivers = more visual impact.


ill look into the beyma 8BX's

did i mention i also have ciare ch250's in transit,

I looked at the 10 inch variety, but all require more volume. OR require significant "padding" in the network.

At a fairly budget friendly price is the Eminence Beta 10CX. After baffle step compensation it may well have a fairly extended response (but at a loss in efficiency).

There are also 12 and 15 inch coaxials to choose from, in fact there are a LOT more choices in the 12" grouping.

Again, work through them in WinISD and see what you come up with.

..and to keep that 80's pimped look you could always add a super tweeter with a shiny metal face plate or a deep inset horn (or both).

 

[NED 209]

ahh man, ive got the cosmetics tied uuup im gonna (faux) mirror plate the front panel, with a faux tape deck and knobs, and take the chrome bits off existing ghettoblasters. itll look prettymuch from the 80's.

so you think the beyma 8bx would put out decent volume? my simple little brain's concluded efficiency = volume, so its all at odds with the 92db rating on them...
chances are im wrong.

12 inches is too big for a hand portable box, i gotta carry that sucker so im aiming for around 8kg

 

[jwmbro]

is there a computer program that'll let me listen to the difference between 40 and 80hz?
Regards
The Doctor

Audacity lets you generate tones in all sorts of frequencies (between 1Hz and 18KHz I think....). And it's free.

 

[ScottG]

ahh man, ive got the cosmetics tied uuup im gonna (faux) mirror plate the front panel, with a faux tape deck and knobs, and take the chrome bits off existing ghettoblasters. itll look prettymuch from the 80's.

so you think the beyma 8bx would put out decent volume? my simple little brain's concluded efficiency = volume, so its all at odds with the 92db rating on them...
chances are im wrong.

12 inches is too big for a hand portable box, i gotta carry that sucker so im aiming for around 8kg

yup.

the beyma 8bx.

..efficiency doesn't equal volume ..unless you don't have the power to supply the driver.

Ultimately the driver's maximum linear volume/spl on average is predicated on linear excursion vs. sd (driver size) and thermal handling.

Here the only problem you would have is with a low freq. at high spl's below the tunning freq. of 40 Hz (..IF you don't have a high pass filter around just below the tunning freq.). The cheapest quick fix in such a situation would be heavily stuffing the vent and accepting the lower spl.s at those low freq.s.

The driver isn't a "subwoofer" so don't expect ultra low freq.s. This of course goes for most drivers. Most 80's gettoblasters couldn't do more than about 70-60 Hz, whereas this design will go quite a bit lower and louder.

In the configuration I spec.ed - with a fairly small cabinet volume and a moderately high tunning freq., yes it should be able to play loud.

btw, this may be a viable crossover here:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=61682&perpage=25&pagenumber=2

 

[kepa1]

I trust this is for some sort of PA or outdoor use? This isn't Hi-Fi stuff, it's designed for volume, not accuracy.

Hi, I wouldn't be so sure about the actual quality of this driver; in fact, lots of people use such drivers in home installs with high efficiency in their mind. And this particular unit is quite the high end of the Beyma line; actually I saw a folded horn design for it that claims to cover 35 to 400hz.