question for soundman or anyone ?

[la Huerta]

i all...been busy trying to get my business rolling along so hav'nt been here for a while...

would someone be able translate this attachment into simple english for me, i have the jv60 loadspeakers from jaycar and this sounds like just the mod. i am looking for to improve there average performance...

[masoth]

I'm not sure this is the "translation" you want, but by removing what (I think) are unnecessary words for the conversion, you are left with less to take your attention. Someone is sure to take you through the technical stuff (and correct me at the same time) but I hope my effort is helpful. The underlined section too, I think, might be ignored - in fact, the entire second paragraph seems to tell only the result:confused: .
I sincerely hope the originator is not insulted/angered by this re-write.

soth


'The jv60 system can be improved by making it into a specialist satellite system. This can be done:
* with a box volume of 40l tuned to 60Hz which results in a bass peak; and
* If these speakers are subsequently driven from the high pass outputs of a sub-woofer amplifier, and the crossover adjusted to around 70Hz the bass peak is removed . The result is a "QB5" alignment.

Over a badwidth extending down to 40Hz the jv60 cannot produce much more than 96dbm.
Using the outlined scheme Smalls, "kp" parameter increases from 3 up to 34. This results in the drivers being able to accept their full voice coil power rating.
Over the band from 65Hz this gives 114dbm average for one speaker, this is about 400Watts "rms".

This system should be complimented by a sub-woofer that goes down to a genuine 20Hz at a sufficient level.'

[la Huerta]

cheers mate, that does help see the fact a bit better...but still don't really know how to go about this project, is there enough info above to do it. ?...that's all i have on the subject...

[la Huerta]

ok , i'll ask some questions related to the above...

"with a box volume of 40l tuned to 60HZ" how do i do this ?

"driven from the high pass outputs of a sub amp" does this mean the speakers are connected to a powered sub in some way ?

"the crossover addjusted to 70HZ", how do i modify the original crossover, i built these speakers, and one of the crossovers was replaced at one time with one i built as jaycar would only supply components, so i have a llittle knowledge (maybe)...

[Harry72]

To tune the box to 60Hz you would alter the port dimensions either by changing its diameter or lenght, use a program like bassbox pro(buy for about $200)or freebee download Winisd.(both of these will do your crossover calc's too...)

"driven by from the high pass outputs of a sub amp"
Most sub woofer amps connect to your mains/fullrange speakers by the speaker wires from your system, basically the sub amp is "inline" between your main system amp and the main/fullrange speakers on the speaker wires.
In doing this the sub amp can cross over the signal ie filter the sub bass from your main speakers(about 80hz down) and filter all other frequencies from the subwoofer itself(about 80hz upwards).

[Master Splinter]

That email appears to be taken verbatim from a post from one of the Jaycar forums...there is no other information in the thread about it...so you are out of luck if you want more details from the author.

"with a box volume of 40l tuned to 60HZ" how do i do this ?

A 40 litre ported box. The tuning is done by the selection of the diameter and length of the port. Ported box designs can have 'one note boom' as indicated in the post, but by using the output from a high pass filter (only lets frequencies higher than a specified point - 70hz in this case) you never get down to the frequency of the box so you avoid the boom!


"driven from the high pass outputs of a sub amp" does this mean the speakers are connected to a powered sub in some way ?

Yes. Sounds like they are being used as the main speakers in a HT setup. So you will need either a HT amp that gives you the ability to dial in the cutoff frequency for the main speakers, or you need a high pass filter. Oh, you'll need a subwoofer too, as the modified speakers won't play lower than 70hz.

"the crossover addjusted to 70HZ"

This isn't the speakers crossover, this is the HT amp crossover - at this point the amp sends frequencies lower than 70hz to the subwoofer.


The modification as described increases the power handling ability of the speakers (they don't bottom out - or hit the 'linear excursion limit' of the drivers), however, this won't address the problem of the amp running out of power during the 'thud bang crash boooom!' parts of movies, unless you add a seperate powered subwoofer.

Personally, I wouldn't touch this modification unless I was happy to consign it all to the junk bin if it turned out to be some self proclaimed expert's theory, and not an actual tested design. (lets face it, most people think the sound they get through their $2.50 earphones is just great...which doesn't say much for their listening abilities!<img>)

I think it would be easier to just add a powered subwoofer first, and see how you like the sound. Your HT amp should let you set the cutoff point for the main speakers.

[la Huerta]

thanks guys, think i'm starting to understand...

Master Splinter, i will take your addvice first, get a sub, and see how it goes, the problem i am having with these speakers is they bottom out in the action scenes, and if i like a extra bit of volume they tend to sound all like one big speaker instead of 2...perhaps the driver installation is not right, ie:should they be recessed , what other factors can contribute this problem, it is not likely to be the amp (onkyo reciever) as i have listened to this amp with high end speakers and it was really something...

oh, and it hasn't got any crossover addjustments on the amp, but could i run the powered sub inline to take the low frequencies before they get to the jv60's...

another question...sealing the ports on the jv'60's, what will this do?



many thanks in addvance for all you help...

la H

[Harry72]

Sealing the ports.... errr sealed box!
Should increase their power handling... and decrease the output of the lower octaves(unless you boost them), one drawback that may happen is these vifa drivers are ment for vented boxes sealing them may induce bad responses making the response curves peaky.
Sealing them may achive what you want, just do to one of the pair to temporarily to hear the difference put them next to each other and feed them a mono signal(identical signal)and use the balance knob to fade between them... see which you like better, but keep in mind you'll be using a sub.
Dont fall into the mistake of substituting the lower midbass from your mains speakers with the subwoofer(thats what all those all in one box systems do... sounds crap).

[la Huerta]

Harry22...so you think that a large pair of floorstanding speakers like the jv60 along with a monster sub would sound better than satelites with a monster sub, because the floorstanding speakers help 'fill' the soundstage more rather that just having highs from satelites and lows from sub...

this sound right ?

[lnt9000]

la Huerta I have heard the jv60's in action and was very Impressed by their performance, however I did not have the opportunity to hear them at high volume, from memory they had a fairly linear response down to 40hz with a dip at around 3khz, are yours constructed correctly?, that mod basically tells you not to use them below 70hz , If they are bottoming out at high volume then backing off the bass and adding a sub would probably be the go, dont know about modifying the box though as It has been designed with the drivers vas specs and should be pretty close.

[la Huerta]

hey i'll leave them alone for a while and save for a sub first...was looking at the top of the range sub amp from jaycar and a 15in driver from them too, how good a quality driver should i get, there is a $100 and a $300 double magnet, both are 4,ohm

[Harry72]

I would'nt call the Jv60's large floor standers, yes floor standers sound awsome with sub reinforcement, sub bass IMHO dont sound right without lower midbass to back it up... just sounds like a sloppy fart!(bit like comparing a Hyundi excel with the 5" exhaust to V8 supercar... balls)

[Harry72]

I wouldnt grab that Jcar 15", they are jc's cheap range and the price reflects it(compared to their other models they sound floppy/muddy), the cs2228 double mag is a very good speaker but its not 4ohm its dual 4ohm... either 2ohm or 8ohm dont run single coil, your wasting half of its motor!(grab 2 instead...)
You could get fancy and build those jv60's with a sub in each... Jcar have the 10" 8ohm cw2137 for $99ea they need a ported box of around 40-50ltrs and 2 of them would give you a fair amount of air displacement(what SB is all about)for under $200... they are a reasonable driver and have won magazine reveiws(By D Duprez)against many others. I have heard and thrashed these 1st hand... definately bargin bass.
Another brand to consider is Adire Audio they make some of the most awsome subs in the world without exuberant prices... on a buget the shiva range is good my own HT sub is a 12" model in a 100ltr(tuned to 25hz!), just ask the neibours across my street how well their windows vibrate.
If you want to go absolutey extreme their "TUMULT 18" will kill any HT sub around period... you know ACDC's song shake your foundations... lets just say you better have good foundations
Adire's aussie source is www.aranmaracoustics.com.au a shiva 12" sould be about $300ish... tumult 18 will be over $1k easy

[la Huerta]

thanks for tthe info Harry22, i definly would like to go with a quality 15in,(acttually had a 10in once, but it was too small for the room, then the wire poped off and blew the sub and sub amp, i was a younger then and did things in halves)...th jaycar 15indouble magnet looooks good and is max price that i would pay, with there 350w amp that's around $600 , not too bad...the loadspeaker kit has http://www.theloudspeakerkit.com/sho...&ProcessType=1has a sweet 15in that they say is thx level but they sell the cabinet with the kit so it's too pricey, if i could find just the driver that they use would be good, not sure who has them...yeh installing subs within an enclosure of the jv60 would be cool too, but who knnows i mighht be able to afford to upgrade from the jv60 one day and a seperate sub would be easier...

[GraemeCook]

Hi La Hueta and all

Wow, you certainly generated an informative series of posts. Well done everyone.

I built some speaker boxes twenty years ago and am currently thinking about upgrading them and possible adding supertweeters. Not being an audio technocrat I have had a fairly long and steep learning curve.

Your posts have also helped me and confirmed some of what I had already discovered.

Besides the web, one useful reference I have used is the "The Loudspeaker Design Cookbook" that I got from Jaycar.

Cheers

Graeme