help building speakers

[la Huerta]

i hope this is the right section...

i have a pair of jv60 floorstanding speakers i got as a kit from jaycar a few years back , i used to listen to a lot of music, then discovered home theatre and now i's just all movies...i'm building a set of very large antique style bookshelves and matching tv cabinet, i would like to get a set of large bookshelf speakers, but i'm saving for biger things at the moment (my own property one day) so i want to use the vifa drivers in the jv60's design new enclosures and crossovers, 3 speakers in total L-C-R , and team them with a monster sub

does someone here have good speaker design knowledge that could point me inthe right direction...i have some experieence in speaker and crossoover building but only to a diagram, not actually starting from scratch....


la H

[Wood Butcher]

Send a PM to Soundman. His name partially dictates his occupation!! He would be a great start to your endeavours!

[Max Ripper]

Go see these folks they beyond serious audiofiles. http://www.diyaudio.com/


Max Ripper

[Spelunx]

Have a look at www.theloudspeakerkit.com (http://www.theloudspeakerkit.com)

There is probably enough info on the site to make your own speakers from their design.

[Pulse]

JV60s are great speakers, are you thinking of removing them and making bookshelf speakers?

Pulse

[Master Splinter]

I'm presuming you want to build smaller speakers (just one woofer in each instead of two) and use the two 'spare' woofers to build a centre channel. This is probably a bit of a waste, as the center channel really does not need to carry a lot of low frequency information. You'll end up with two spare woofers (they aren't really big enough to use to build a subwoofer from), and you'll have to buy a couple of 5 inch midrange drivers and some tweeters from Jaycar anyway...

However, if you want to do it the long way...

1) Dig up the Thiele-Small parameters of your existing drivers.

2) Download something like WinISD. Here's a site for it - http://www.linearteam.dk/default.aspx?pageid=help

3) Use your Thiele-Small parameters to calculate appropriate box volumes for your redesigned speakers.

4) Jaycar has crossover design info, as well as pre wound inductors, capacitors and PCBs, however you should be able to use the existing crossovers and just get one to suit the speakers in your center channel.

And for a subwoofer, a jaycar plate amp and either a 12 or 15 inch Shiva subwoofer from adire audio will get your teeth rattling, and annoy your neighbours no end!

[stolar]

You will need to look at one of the programs to calculate the volume of the box.
Do not be tempted to make box bigger to get deeper bas or to get bass frequencies raised. It will produce more waffle then music.

The LF speakers will dictate if the box needs to be compression or BR design. More compliance in driver suspension tends to work better with compression boxes. As a rule of thumb compression desings tend to cut off little bit higher but produce clean and tight bass.

Few tips,
* make sure the box is air tight and the speakers are mounted air tight (do not use silicon for mounting speakers you will have hard time taking them out)
even if you are making BF box it needs to be airtight (other then the port obviously)
* make the front baffle as small as possible,
* round off edges on the front baffle,
* use at lease 19mm MDF, 25 is better
* brace all panels internally
brace a lot and brace off centre (as in, do not create equal division with bracing
* make sure that you separate the speaker centres by the wavelength of their crossover frequency (l=c/f , l - wavelength in m, c - speed of sound - 343 m/s, f -frequency in Hz)
* put HF driver off centre if practical
* use good quality components for cross over, do not use electrolytic capacitors and do not use iron core inductors. Use only air wound inductors.

Paying attention to details makes a huge difference and combined with decent speakers and a good design is a good start for great speakers.

[la Huerta]

yes it's a jv60 makeover, there ok speakers , i like the idea of 3 equal satilite speakers and a monser sub, the jv60 don't like he low end that well and are a little harsh if your to close, and it's a lot of boxes , 2 floor standing , a center, and a sub, having bookshelf speakers keeps it neat and wires can be hidden behind the shelves...i was actually hoping to keep both woofers in the smaller box design to keep the power handling up, perhaps a sealed enclosure to give tighter sound , it's does'nt have to be bassy as the sub will handle that...basicly the jv60's in a small package, if it can be done...if it can't then they'll have to stay the way they are...

[la Huerta]

another thing on the subject of speaker building

real wood v mdf...

thoughts anyone ???

[Master Splinter]

This is one area where MDF is better than real wood. It has a consistant density, which helps keep internal reflections similar in tone. Its also nice and heavy, which helps.

Trying to rebuild both speakers to fit into a smaller box...is likely to end up in tears unless you play around with speaker box design programs for quite some time; even then your speakers are probably at their smallest box volume anyway.

[la Huerta]

yeh i had a feeling it might be more trouble than it's worth, i played around with speaker design before with the centre channel, and yes lots of tears involved...

ok...they will stay the way they are, i'm not prepared to stuff around and make a mistake ...so these ones will get a new finish, i built these from 25mm mdf, but the black finish is a little outdated now, my new plan is to overhaul the boxes and grill cloths...

still on the subject of these speakers, 'clipping' is this when the bass bottoms out and the woofer starts sound distorted, this happens at slightly higher volumes with say an action scene like an explosion or something, so i turn it down a notch as soon as i hear this till the bass is tight again, and so no dammaged will acure...but could this be the amp's fault, it's an onkyo reciever, very nice model but only 60watts/ch , speakers are 150watts each...

[Master Splinter]

Yep, its the amp, going into clipping. It's the sign that it's running out of puff at high volume levels.

The Onkyo's are reasonable amps, but you might like something with more ooomph-ability if its just not quite loud enough in the noisy bits.

Avoid anything which proudly states its PMPO or "Peak music power output". This measure is generally some sort of quick n' nasty extrapolation of 'what's the maximum it can produce without instantly turning the power transistors into an expanding cloud of smoke".

When clipping, the speaker is looking at a DC voltage across its terminals which means the cone is slammed to the limit of its travel, and held there. Do this enough, and you may overheat the voice coils, melt some copper wire, and lose a speaker and maybe even take out the amp, too.

Keep in mind that decibels are a logarithmic measure - it only takes about one watt of power to get an average pair of speakers to produce 80-90 decibels of noise; to increase a single loudspeakers output by just three decibels (double the volume) takes 10 watts of power; to increase it again by three (so you have a six db increase in total) takes 100 watts of power, increase it by 3db again and ...yup, 1000 watts.

You may find that an amplified subwoofer (that loudspeakerkit link is a good place to look) keeps the pressure off your main amp. See here for a review (http://www.dansdata.com/s250.htm) of their sub.

[Petebass]

I was going to dig up the T/s data and do some maths as the the ideal enclosure size and porting. I did some hunting around for some hard specs on the JV60's. Apparently they use two Vifa P17 speakers. Further investigation shows Vifa have several 6.5" speakers that start with the P17 model designation, and they all have different Thielle/Small paramaters.

Can anyone point my wild goose chase in the right direction? does anyone know exactly which Vifa drivers are in the JV60's?

If we can't get T/S parameters, you could always reverse engineer Jaycar's design. By that I mean replicate their design but break it dow into a "per/woofer" calculation. For example if the current box is 20 litres, then that's 10 litres per speaker. The hard part is finding out the tuning frequency of the porting. There's a couple of ways to do that, and neither of them is overly difficult if you've got some basic electronic tools (multimeter & resistors mainly). I can talk you through it if needed.

[la Huerta]

crickey i'm an iddiot some times, forgot i started this thread way back and did'nt check it, so i'll continue from here...

Petebass...all the above sound interesting...

i think the drivers in the jv60's are the p17 wj...and the tweeter is the 25ag...

details on this sitehttp://www.essentialaudio.com.au/index.html?lang=en-us&target=d108.html