Circlotron said:
Go for a look in your nearest Spotlight store. They have some bags of polyester or Tontine stuff meant for making cushions out of, but is just the ticket for box damping. I bought a bag the other day for ~$12 and 60% of it easily filled a 100 litre box. I used the rest for two smaller ones. they have smaller amounts (for smaller cushions, no less!) for about $8 and ~$5 so there is one for every budget and every bottom. http://www.spotlight.com.au/
P.S. Take your mum and make it look like she is forcing you to be there. It's like a hardware shop for women. (Imagine sound like Sideshow Bob groaning...)
OTOH, you could always go there by yourself and act totally helpless while letting one of those salesgirls spend ages fussing over you helping you decide what you already know you are going to buy.
Bahh.. stuff it.. lol I'll worry aout it once I have painted the boxes..
for now I'll just leave the piece of foam/sponge in each box.. lol I mean... it almost seems that the speakers sound WORSE now that the baffels are glued on... they really need a midrange... 
SkinnyBoy said:
LOL (hehe) no boobs here...
Yes.... I need to know the actualy difference.. someone said that connecting 2 drivers in series resulted in a 3dB gain.. while connecting them in parallel resulted in a 6dB gain.... Thats all well and good, it would mean that the woofers are like 91dB 1w/1m and the tweeter is 92dB at 2.83 1metre.... so.. how does that compare..
So..... do I need the tar based type dampening material? or do I need like fibreglass stuffing?
Hi Skinny boy. I think probably you really need to model them in something, since you can't use unibox, speaker workshop would probably do the trick (It has provision for two drivers). The thing I found weirdest was that unibox actually showed slightly higher efficiency when wired in series (probably between 1 and 2 db), but it also changed the box volume/tuning and the F3 point.
Sorry about the tar dig
I have seen recommendations about using scraps of roofing ashphalt before, thougt I'd make a joke....... My existing speakers have some stuff from Jaycar (polyester mats). Circlotrons suggestion is a good one, I'm glad he said that cause I suggested spotlight to someone else even though I hadn't checked to see if they actually had the stuff. His comments about taking your mum, or looking helpless are spot on too, you will probably feel like your the only guy there (You could take your girlfriend too, if you've got one, but you may never get her to leave)........With regards to your midrange problem, have you considered running the woofers as dedicated subs, and making a separate small two way for the top end. You could probably get away with using just a low pass on the sub (I know your current budget wouldn't stretch to a separate amp for them), and just using a 2 way xover on the small box, letting the natural rolloff take care of the low end.
Regards,
Tony.
wintermute said:
Hi Skinny boy. I think probably you really need to model them in something, since you can't use unibox, speaker workshop would probably do the trick (It has provision for two drivers). The thing I found weirdest was that unibox actually showed slightly higher efficiency when wired in series (probably between 1 and 2 db), but it also changed the box volume/tuning and the F3 point.
Sorry about the tar dig
With regards to your midrange problem, have you considered running the woofers as dedicated subs, and making a separate small two way for the top end. You could probably get away with using just a low pass on the sub (I know your current budget wouldn't stretch to a separate amp for them), and just using a 2 way xover on the small box, letting the natural rolloff take care of the low end.
Regards,
Tony.
I tried speaker workshop...
umm.. I have no idea what I am doing.. heheThanx for the suggestings about the stuff from a fabric shop... I'm not going to take my mum, and I don't have a gf..
perhaps I can also purchase one from spotlight??I was actually considering triamping these... one amp for each woofer, and one for the mid and tweeter together with a passive crossover.... the reason for this is that my current amp gives about 50watts into 4 ohms.. it clips with the bass, and you can hear it thorught the tweeters... seperate channel for each woofer means the amp will be driving a 4ohm load, and giving more power, and there will be no need to bridge the amp..
(which would be bad if someone then tried to run a 4ohm speaker off the bridged channels..) I was thinking 70 or so watts per channel into 4 ohms, 40 or so watts into 8 ohms... just right for the woofers.. and its 3 times what they are getting now.. ohh... BTW.... I nearly blew one of my Peerless tweeters.. lol
basically... feeding it straight from the amp with no crossover results in a dome tweeter getting about 3mm of dome excursion in the form of the dome flexing in and out... you learn something new everyday.. lolI would really like to use the LM4780 amplifier ICs... only problem is my voltage rails have to be either +-25 volts, or +-38 volts... one of which is really too low.. the other too high... any suggestions? I can afford the inefficiencies of regulating the supply rails, but would really like to avoid this if I could...
Thanx in advance..
James Stanley
OHH!! and I added mroe pics to the website.. lol
http://home.iprimus.com.au/jlstanley/Speakers/Speaker_Box_Construction.html
Hey Skinnyboy,SkinnyBoy said:
ohh... BTW.... I nearly blew one of my Peerless tweeters.. lol
How did you forget your x-over? Maybe you need something jug your mammary.
Oh puh-lease....roddyama said:
Hey Skinnyboy,
How did you forget your x-over? Maybe you need something jug your mammary.
BTW, the $12 bag at Spotlight was 1kg.
It has a picture of Humpty Dumpty on the front. True!
I think the idea was that if he had of fallen onto one of the cushions you could make from this stuffing he would have been ok.
Circlotron said:
Oh puh-lease....
BTW, the $12 bag at Spotlight was 1kg.
It has a picture of Humpty Dumpty on the front. True!
I think the idea was that if he had of fallen onto one of the cushions you could make from this stuffing he would have been ok.
I think the stuff from Jaycar costs like $23.08 for a KG.. lol
Okay... I'm getting a bag of the stuff from spotlight or wherever... putting half in each box... with a piece of foam in each as well directly behind the drivers.... and... I am putting terminals on the back to I can connect the drivers in either parallel, series, to seperate channels of the amp, or only connect one driver... OK!!! the boxes are at school now...
OK!!! the boxes are at school now...
I forgot the crossovers because the crossover was a single capacitor on the tweeter... I had tried a different crossover, the same one my friend was using, to see what difference it made to the tweeter and midrange... when I disconnected this crossover, I forgot to reconnect the other crossover again... soo.. I was feeding the tweeter the same amount of power as the woofers... and the woofers were getting about 5mm of one way cone excursion.... lol okay.... I dunno what to do for an amp... I am now considering running each woofer, each mid, and each tweeter off a seperate channel... so.. 8 channels all up.. the reason for this is that the transformers will be able to do it no problem.. and it means I could run 4 pairs of speakers off the amp if I needed to.. lol
should I regulate the voltage rails down to +-30 volts from +-38 volts?? with +-40 volts, the LM4780 will give 80watts into 8 ohms... with +-30 volts, it will give 75 watts into 4 ohms... with +-25 volts, it will give about 55 watts into 4 ohms, or 30 watts into 8 ohms... let me make that abit easier to understand...
+-40 volts 80watts @ 8ohms (graph doesn't go this high for 4ohms)
+-35 volts 60watts @ 8ohms (graph doesn't go this high for 4ohms)
+-30 volts 45watts @ 8ohms 75watts @ 4ohms
+-25 volts 30watts @ 8ohms 55watts @ 4ohms
SO..... do I run with +-38 volts and risk running the chips at too high a voltage?? do I run at +- 30volts with regulation on the voltage rails, and get a good amount of power? or, do I run +-25 volt rails, only have a 6 channel amp, and not drive the speakers to their fullest potential??
lol okay.... I dunno what to do for an amp... I am now considering running each woofer, each mid, and each tweeter off a seperate channel... so.. 8 channels all up.. the reason for this is that the transformers will be able to do it no problem.. and it means I could run 4 pairs of speakers off the amp if I needed to.. lolshould I regulate the voltage rails down to +-30 volts from +-38 volts?? with +-40 volts, the LM4780 will give 80watts into 8 ohms... with +-30 volts, it will give 75 watts into 4 ohms... with +-25 volts, it will give about 55 watts into 4 ohms, or 30 watts into 8 ohms... let me make that abit easier to understand...
+-40 volts 80watts @ 8ohms (graph doesn't go this high for 4ohms)
+-35 volts 60watts @ 8ohms (graph doesn't go this high for 4ohms)
+-30 volts 45watts @ 8ohms 75watts @ 4ohms
+-25 volts 30watts @ 8ohms 55watts @ 4ohms
SO..... do I run with +-38 volts and risk running the chips at too high a voltage?? do I run at +- 30volts with regulation on the voltage rails, and get a good amount of power? or, do I run +-25 volt rails, only have a 6 channel amp, and not drive the speakers to their fullest potential??
SkinnyBoy said:I forgot the crossovers because the crossover was a single capacitor on the tweeter... I had tried a different crossover, the same one my friend was using, to see what difference it made to the tweeter and midrange... when I disconnected this crossover, I forgot to reconnect the other crossover again... soo.. I was feeding the tweeter the same amount of power as the woofers... and the woofers were getting about 5mm of one way cone excursion....
should I regulate the voltage rails down to +-30 volts from +-38 volts?? with +-40 volts, the LM4780 will give 80watts into 8 ohms... with +-30 volts, it will give 75 watts into 4 ohms... with +-25 volts, it will give about 55 watts into 4 ohms, or 30 watts into 8 ohms... let me make that abit easier to understand...
+-40 volts 80watts @ 8ohms (graph doesn't go this high for 4ohms)
+-35 volts 60watts @ 8ohms (graph doesn't go this high for 4ohms)
+-30 volts 45watts @ 8ohms 75watts @ 4ohms
+-25 volts 30watts @ 8ohms 55watts @ 4ohms
SO..... do I run with +-38 volts and risk running the chips at too high a voltage?? do I run at +- 30volts with regulation on the voltage rails, and get a good amount of power? or, do I run +-25 volt rails, only have a 6 channel amp, and not drive the speakers to their fullest potential??
Hi Skinnyboy I did a bit of a search on this IC the other day and I'm pretty sure it said it could handle up to +-84V (just checked again and one of the features is Wide supply range 20V - 84V http://www.national.com/ds/LM/LM4780.pdf
So I don't think that +-38V is going to be a problem somehow!
Regards,
Tony.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.