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Old 17th March 2002, 04:22 AM   #11
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Default hey...

what impedance is each coil, because if each coil is 4 ohms, wiring them in paralel would make a load of 2 ohms, and this is too low for most home amps. but if theyre 8 ohm coils, that will be cool, as it will present a 4 ohm load to the amp. and by the way, the way you said you'd wire it above ^^^ is correct.
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Old 18th March 2002, 08:28 AM   #12
Wizard of Kelts
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Javaman:

I haven't forgotten you. I have been meaning to answer you since the other thread. I think I have another subwoofer that gives better performance in a 1.4 cu ft or 2.0 cu ft box than the Dayton Titanic 10. It's the Peerless XLS 10 inch tuned to 25 in a 1.4 cu ft box or 22 in a 2.0 cu ft box.

www.peerless.dk

The delay is that I have difficulty getting Boxplot's graphs to get into an image format that this forum can print. Working on it. Will be back.

Peerless is sold by Madisound and I think Parts Express has started carrying them. About the same price as the Titanic, I think.
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Old 18th March 2002, 10:18 AM   #13
Wizard of Kelts
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Looks like I wrote too soon. I was dealing with the old Titan. The Titan II is down 3 dB at 27 Hz and 5 dB at 25 Hz when tuned to 25 Hz. This is excellent performance.

In a 2 cubic foot box, the performance is even better. The 12 inch would have too high a cutoff in a 2 cubic foot box, I think.
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Old 18th March 2002, 04:59 PM   #14
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Many thanks kelticwizard

I had looked at the Peerless - in fact I build a sat/sub setup many years ago using their CC line drivers for the mid and a Madisound
1250 (I think it was) in a huge sub box. Didn't sound half bad for a first effort. Anyhow I digress......

The Titanic 12 MKII in the 2ft^3 sealed does rolloff early ( F3 at around 38Hz) but I was hoping with some fairly aggressive EQ boost, say 5-6dB round 22-25Hz, I could get some serious bass and still have all the inherent advantages of a sealed design. What do you think? I know, I know no free lunch........

My application is primarily music and this is why I was also attracted to the EBS alignment. It looked like a smoother rolloff than most ported designs for a nice blend with some room gain and still met the <= 2ft^3 box limitation. Would it be wise to use any EQ with this type of design?

Also I noticed Peerless has a small PR alignment in their 10 inch XLS docs that seems to go really low but I am a little reticent to use a PR design for a music application. Do you think is would sound good? I am afraid it would be a little tricky to tune just right.

adios
peter
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Old 18th March 2002, 11:48 PM   #15
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I lied. It's the Peerless XLS 12 inch application notes that detail a 35 liter box tuned to 20Hz with 625g on a passive radiator. Their sim. with BassBox Pro (sounds like a fishing program to me) shows an F3 around 25. I don't get anything remotely like that using plain old WinISD.

Is a PR simulation that much different from a regular vent?

I'd fire up the table saw tonight if I really felt I could get that kind of performance from such a small box and have good musicality as well.

Don't PR designs have the worst transient response and worst group delay? And how much does it matter?? I can't think of any high-end products that use PRs.

Geez I've gone all the way around the horn and I am back to the basic "what's the best 2ft^3 sub I can build?" question again! Help!
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Old 19th March 2002, 01:22 AM   #16
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Default hey

I like using BassBox Pro, its a good program, and no, there are no fishing simulations in there...

Simulating in BassBox Pro the Peerless XLS 12 8ohm with the matching passive radiator does indeed show that group delay is all over the place, it actually looks worse than any ported group delay I've seen...

You may be right Javaman, but I have not had any real experience with passive radiators.
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Old 19th March 2002, 03:01 AM   #17
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Javaman:

Have not built passive radiators. Essentially they are "vent substitutes". They should sound similar to vents.

Any difference with "drone cones"and vented systems is possibly due to the fact that the drone cone itself has a resonance, and this resonance detracts, not adds to the bass output of the speaker, forcing it to roll off at a greater slope. Looking at some charts, it seems that the slope of the effect of the passive radiator tuning starts about an octave and a half below the tuning frequency of the system, or Fb. So if your drone cone resonance, (as opposed to your enclosure resonance, or Fb), is 2 octaves below Fb, there probably should be no effect worth worrying about.

The Peerless drone cones are tuned to 6 Hz, I believe, and adding mass to them should tune them even lower. After, all, adding mass to a normal loudspeaker cone lowers it's resonance frequency, so this should be the same. This might be why Peerless tirelessly promotes these drone cones to go with their XLS systems.

I should add that Pioneer makes a drone cone that is very inexpensive. It is just Styrofoam with a foam surround attached to the frame. Theoretically, this should be all you need in a passive radiator, but web sites have stated that drone cones with a spider are superior. Why, I don't know. Maybe it has something to do with the weight-drone cones can get fairly heavy if you use more than one and you want to tune low.

Normally a 10 inch speaker is fine with a 3 inch vent, but the Dayton and Peerless XLS are not ordinary 10 inch speakers. If you want to go to a 4 inch diameter vent, it will be about 32 inches to tune at 2 cu ft box to 22 Hz or a 1.4 cu ft box to 25 Hz. Both vents take up less than a quarter of a cubic foot . You might wish to negotiate your size limits up slightly to accommodate.

Madisound sells 3 inch ports, flared at both ends, which should bring the vent volume down to less than 10% of box volume, yielding a negligible increase in Fb. A flared pipe is equivalent to a larger pipe, unflared. Apparently, from what I can see, the flared ports are designed to fit over a straight piece of PVC pipe.

If you use a 4", at 30+ inches, you will most likely want to use an elbow, easily obtained from building supply stores. If you use the flared 3" pipe, it will be shorter.

If I were building it, I would go with the Dayton Titanic 10 inch Mark II in a 2 cubic foot box. If it is already established that you can go to 2 cubic feet for a 12 inch, it seems to me that you ought to be able to go that high for a 10 inch.

For a long time, a .25 inch throw, either way was considered a very long throw woofer. With more than .5 inch excursion, the Dayton or Peerless really is equivalent to an old 15 inch, only with cubic foot requirements equivalent to a regular 10 inch. If these speakers can do that, the least you can do is give them a LITTLE extra room, LOL.

I am obviously not in a position to know your space requirements. But going down to the low twenties in a 2 cubic foot box is quite an accomplishment, in my opinion.

Let me know how this turns out.

There is another possiblity. The Blueprint 1001. The webpage is down, but you can Email for specs. As I recall, it had specs similar to the Dayton, but it cost only 79 bucks. At least that was the old price. The Email address is:www.blueprintdrivers@hotmail.com. Blueprint invites inquiries.

Hope to hear from you soon.
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Old 19th March 2002, 03:10 PM   #18
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Well.. Tanks for all the answers and informations...!!!

You guys know a lot more than me!!

So I think I will do a front firing sub, vented.

I will let you know when the project will be on his way.

MisterB
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Old 20th March 2002, 03:52 PM   #19
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kelticwizard

I thinks I'll take you advice and go with a ported Titan 10 inch design, thanks.

Did you like the 2 cubic foot box for it's smoother rolloff, rather that something smaller?

Also I was also wondering about the port diameter. Seems Unibox recommends an air speed < mach .08 while WinISD and older programs seem to draw the line at around .16. Who's being too conservative/optimistic?

Using the .16 number I could get away with shortening the Madisound 3 inch flared port. With the 17 inch long 4 inch port I'd be splicing in some extra length and I am sure the interior would end up with ridges. Wouldn't this cause turbulence and noise?

Thanks again for your help.

regards
peter
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Old 21st March 2002, 03:29 PM   #20
Wizard of Kelts
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Quote:
Originally posted by Javaman

Did you like the 2 cubic foot box for it's smoother rolloff, rather that something smaller?
I like the 2 cubic foot box for a couple of reasons.

Sometime during the eighties, an article was published in the Journal of the Audio Engineering Society where all the bass content of videotapes and CD's were analyzed in an exhaustive search to find the lowest notes your subwoofer would actually have to play. All of the lowest notes were on CD's, (the present-day DVD might change that, I don't know), and it was found that there were only FIVE CD's that had usable bass content below 16 Hz.

Unless you are a millionaire building a room specially designed for music listening, it makes little sense to design your system to cover the 5 CD's out there-somewhere-that might actually use it's capabilities. So, 16 Hz is the sensible goal.

And what kind of subwoofers actually can go down to 16 Hz? Big ones. With big price tags. That take up a LOT of space in your listening room, and leave a lot of empty space in your bank account. Four, five cubic feet or more, that cost thousands of dollars. That is what kind of subwoofer is 3 dB down at 16 Hz.

In a 2 cubic foot box, the Titanic 10 Mk II, assuming the numbers are correct, will be 3 dB down at 23 Hz. That is only half an octave above 16 Hz, (the sensible goal for even a shoot-the-moon subwoofer). And it accomplishes this in a "standard" 2 cubic foot box.

A "standard" 2 cubic foot box? Well, I have been following audio since the seventies, and even at that time, the normal size for a "full-size" speaker was 2 cubic feet. Advents, AR's, and a host of others. It seems that early on, designers discovered that 2 cubic feet was the best combo of enclosure volume and unobtrusiveness. And people had 2 of those speakers per room, not one. Those speakers did not go down to 30 Hz, let alone 23 Hz.

Here, you have the capability of generating bass only a bit behind the best subwoofers out there, in a box size that for decades has been considered "standard", even for 2 units in a room. If you go to the 1.4 cu ft box, your 3 dB down point will just nudge below 30 Hz, which is very good. But there are a lot of speakers out there now that go down to 30 Hz, albeit in bigger boxes. There really aren't that many that go down to 23 Hz.

Heck, it's your place, it's up to you to decide what is visually acceptable and what is not. But since you asked, those are my thoughts on the matter.
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