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Old 24th May 2007, 02:55 PM   #101
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Join Date: Dec 2005
Location: Singapore
Hi Paul,

I don't have TC2+ in the list of drivers, do you think you could mail me the WinISD file for it? Also for my Coral Beta 8, what should I enter for the parameters? I'm a little confused on the terminology here...

So I guess to plot multiple curves, just open more 'projects' will do correct?

thanks for helping!
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Old 28th May 2007, 03:07 PM   #102
terry j is offline terry j  Australia
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funny, it seems quite a few aussies are interested in this thread!!

Have been tossing up whether I need to get a sub or not, only listen to two channel not HT, and if I were to go for subs have been seriously considering something from the servo rythmik line.

The positive feedback seen over the last few pages is encouraging!

My big conceptual question is-do I need it?? I get a very flat response down to 30 hz (well 29 actually) after which it drops like a stone.

Sooo, for the remaining small bit of the frequency band I am missing the question has to be asked, does it matter?

I quickly threw together a Thor a la Seigfreid Linkwitz, just had a driver sitting around and to be honest it didn't seem to make a hell of a difference. Of course, it must be said that that sub would not be approaching one of these in quality, but none the less the doubt remains.

Of course, if I had one (or two) subs like this you would lessen the load on the mains by cutting them of higher and letting the sub do the hard work lower, the benefit there may not be in increased extension but maybe lessened distortion overall, in in effect end up with a four way.

I realise that I haven't asked anything here, so how about this. Accepting that these subs are of good quality (as seems to be the case) what argument could be mounted about getting one/pair given that I already get flat to 30 hz?? It would be a different question if I used it for HT, how much music is there down to say 20 hz??

In any case, if this post goes thru to the keeper, am enjoying this thread and will watch developments with interest.

thanks all
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Old 28th May 2007, 03:23 PM   #103
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It's not that the actual music goes into subsonics, but you start to notice subtle things like wind on the mic and a general increase in 'you are there' quality.

I'm 110% satisfied with my Rythmik
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Old 28th May 2007, 03:27 PM   #104
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Perhaps this can help you answer the question?
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Old 29th May 2007, 04:54 AM   #105
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My Rhytmik can hit 16hz with authority. It can probably go lower, but 16hz was the lowest tone on the test CD I used.

I think it's the best thing I ever did for my home theater.
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Old 29th May 2007, 05:58 AM   #106
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Quote:
Originally posted by terry j
My big conceptual question is-do I need it?? I get a very flat response down to 30 hz (well 29 actually) after which it drops like a stone.

Sooo, for the remaining small bit of the frequency band I am missing the question has to be asked, does it matter?

I quickly threw together a Thor a la Seigfreid Linkwitz, just had a driver sitting around and to be honest it didn't seem to make a hell of a difference. Of course, it must be said that that sub would not be approaching one of these in quality, but none the less the doubt remains.

Of course, if I had one (or two) subs like this you would lessen the load on the mains by cutting them of higher and letting the sub do the hard work lower, the benefit there may not be in increased extension but maybe lessened distortion overall, in in effect end up with a four way.

I realise that I haven't asked anything here, so how about this. Accepting that these subs are of good quality (as seems to be the case) what argument could be mounted about getting one/pair given that I already get flat to 30 hz?? It would be a different question if I used it for HT, how much music is there down to say 20 hz??
Terry,

my mains also go to below 30Hz. And no, I don't listen to test CDs, and have perhaps grand total of 3 CDs that will go below that (one is gimmicky Time Warp and other two are classical with low organ pedals used). Sorry, make that 4, Kunzel's '1812' uses real cannons supposedly hitting 8Hz!
Bottom line, I'll never need subs if I was only to use them for below 30Hz duty.

BUT ! As you have observed, most drivers will distort dramatically less if relieved of high excursion duties. Just look at just about any driver's distortion specs - once you go below 100Hz they ramp up like a tsunami wave ! Dedicated subs are different beasts, and with servo feedback they are even better.
So that is the idea for me ... the question remains about integration. Matching phase shift, delay and combined acoustic and electric filter characteristic on both sides is no child's play. I still have painful memories of searching for that elusive sub to match Quad's incomparable ESL 57's.
I have failed miserably ...

That's the scary bit for me anyway.
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Old 29th May 2007, 06:47 AM   #107
terry j is offline terry j  Australia
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hi all

thanks for your feedback, I guess it's fair to say that for sound quality everyone agrees that it's better if you can to have the subs.

I'm certainly leaning that way, if only as Bratislav says (how was your trip Bratislav??) to lessen the load on the mains.

Integration would be my biggest concern, at the moment my mains are a three way using the deqx to tri amp them. Add the subs (if I bit the bullet I think I'd go the whole hog and get one each side) and in effect it becomes a four way, and in addition to whatever eq I'd apply to the mains bass the subs would need eq as well, BUT I'm not sure I could justify the expense of a second deqx for that role!!

Now is the perfect time for me I suppose to make the decision, as I intend very soon to rebuild my mains into their final form (unashamedly based and inspired by the SF stradivari) and so should actually build them into the box at the outset.

That I feel is a bit off topic, so to bring it back on topic anyone up for some sort of group buy in Aus to help with freight costs?

Will re-read th rythmik site and perhaps send an email or two, must first talk to the 'boss' I suppose, she controls the purse strings ha ha.
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Old 29th May 2007, 07:54 AM   #108
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terry, a sub can be a backward step in SQ. This is true of many subs, and normally without a servo I'd expect woofers to be better than subs in SQ. When I added subs to my TL mains, I found the SQ dropped and the bass was less defined. This was true even when the subs were running at 1% of their xmax compared to the TLs using half their xmax. (I think a lot of DIYers over-emphasize the importance of flat BL curve).

What I noticed about my Rythmik is that it sounds very much like the bass from high end woofers. I recall liking the sound of some focal audiom 13" woofers. As I recall, they cost about $1k each which is more than the cost of the Rythmik 12" kit shipped with an amp included.

If 30 Hz is all you need, then there could be an argument for some reasonably priced hifi woofers, like Peerless SLS with an active xo and dedicated power amp. Still, by the time you include an amp and active xo and a box that is going to be bigger, the sub starts looking more and more attractive.

Also, I find the result is not the same. There is more to it than freq resp. There is more authority with a sub. I calibrate it to flat with and without the sub and the sound is not the same. In the past, the difference was the sub made the bass less defined. Now, it just has more authority.

Bass goes deeper than you think. I use a RTA all the time and there is always action down to 20 Hz. Often more than you think.
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Old 29th May 2007, 09:07 AM   #109
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Terry, trip was -er- exhausting. But it's good be be home !

Paul, yes, there could be "things" below 30Hz but they aren't produced by instruments (not usually anyway). Even if the lowest note on some instruments can go lower, it is seldom played, if ever.
Now, HT sound effects are different kettle of fish altogether, but I'm not into that sort of thing.
As far as SQ, I know for sure that Seas Excel bass drivers in my VAFs, despite having all the modern wizardry incorporated, struggle when pushed hard (or even not so hard). Their distortion figures go into whole percents as soon as you give them more than 1W at say below 60-70Hz.
Now, some may argue that distortion isn't heard easily at low frequencies, but contrary is true. Because our hearing (look how Fletcher-Munson curves bunch up at low frequencies!) even relatively small amount of harmonics will be heard as coloration. Big bass drivers don't have to work as hard. I can tell you that there is no small difference in bass quality between ATC's ('proper' 12" driver) and VAFs (so called 8" but in reality more like 6") in a large room when volume goes up. Now, I don't normally listen at those volumes, but knowing it now, it bothers me
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Old 29th May 2007, 09:55 AM   #110
terry j is offline terry j  Australia
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Thanks guys

I guess I should say that the bass drivers I'm using are 18" PHL's (7030) which I marry up with a PHL 1660 mid, at 300hz.

The 18's have real authority, but being pro drivers don't really go that low, and to get them down to 30 hz takes an awful lot of boost. They don't seem to mind however, but of course theoretically it would seem that it would be less 'strain' if I only took them down to say 40-50hz and filled in the bottom with some quality subs, with an added benefit of going lower anyway. And by all accounts it seems that these rythmiks will do it with good sq.

Thinking on it further today, the integration of the subs is looming as the bigger problem, given my self-imposed restraints of not wanting the extra expense of using another deqx.

Whilst I could possibly use an external unit such as the behringer deq 2496 to handle the eq duties, I would be losing the huge advantage the deqx gives of being able to eq via the remote (this allows me to compensate for a bass heavy/shy recording via the remote). In the case where the sub is seperately eq'd then the remote would only affect the main bass driver, the sub will stay untouched.

One possible way around it would be to put a passive network between the mid and the tweeter, then allowing the deqx to treat the combined two drivers as a single unit (called upper say), then the main bass units could be the 'mid' leaving the subs as the 'bass'.In this case the remote eq functions would then operate on the system as a whole.

That of course means I have to design the passive network, something for which I am totally ill-qualified!!aarrggh.

An alternative would be to put an aftermarket active unit as the x-over, but it would have to be of reasonably high quality given where in the frequency scale it is being inserted, which starts back towards expensive.

Does anyone know of a quality unit that would suit for this application?? The trouble with a passive network would be to match the steep slopes I currently use between the drivers, cause from memory the mid's response goes a bit wonky up around 5-6k, which I avoid at the moment with 200 db slopes.

Having said that, maybe the problems I'm envisaging with a passive network aren't as bad as I imagine.

What to do, what to do.
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