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Multi-Way Conventional loudspeakers with crossovers

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Old 20th October 2001, 04:58 PM   #11
Wizard of Kelts
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Jteef:

You mentioned cost as the reason you did not want a sub/satellite combo. Two Peerless 260's and one Shiva cost about the same. With two 8 ohm voice coils, crossing over at 200 Hz will cost the same, passive crossover wise, as to the Peerless or any low frequency speaker. Even a 150 Hz crossover would not be that much more.

The maximum box size you mentioned-48" high, 15" square-will yield an internal volume, (assuming 1" building materials) of 4.5 cubic feet. Enough to put a Shiva into and go way down into the low twenties for a 3 dB cutoff.

The sub/satellite idea, using the Shiva, might be posible within your budget.
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Old 20th October 2001, 05:40 PM   #12
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Wiz...

Of course the plot is free-air, ever seen a mfgr's plot that wasn't?

Oh, and thanks for the box design tutorial. I'd appreciate your learned assistance for our next project, it's a klone of the Krell MRS sub.....

BTW, cone breakup can easily occur at lower frequencies, depends on how hard the unit is being driven. Poly is the least rigid of any of the commonly used cone materials.

Regards
ThomasW
http://www.Klone-Audio.com


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Old 20th October 2001, 09:16 PM   #13
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ThomasW: Would you happen to be one of those who runs the Klone-Audio site? If so, when are we ever going to see some SLAMM Klone updates?

Sorry for the inconvenience.

Oh, and Keltic: When you said that the Shiva would be -8db at 21 hz, you are referring to the free air resonance, right?
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Old 21st October 2001, 12:34 AM   #14
jteef is offline jteef  United States
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The shiva kit281 doesn't appeal to me. Mostly because of the crossover. I think I can do better.

Although it isn't essential, I would like to stick with active xovers. I think the speakers I was referring to above might work fine in a TM design if I can notch out the large peaks that many of these drivers exhibit around 2khz before they really break up. This way I can still use nicer drivers and stay within budget.

I'll probably end up building a sealed test enclosure to see if the bass is satisfactory in the room

I will wait to see how the LM3886 amp turns out before I decide to go 3 way. Although, I kinda wanted to keep my leach amp on the midrange.

What about something like the Seas T17RE in an MTM design? Vented it would have an F3 of about 45 hz and be pretty cheap. sealed F3 is a high 75hz. Any comments on the series filters that are shown on Tony Gee's page ? I've never used anything like them before, but they seem to work well.

keep the ideas coming!

thanks a lot

jt
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Old 21st October 2001, 01:25 AM   #15
Wizard of Kelts
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Super:

Yes, that is for a free air woofer. The formula for the output of any free air woofer at resonance is given by: 20 Log Qts. So in free air, the Shiva, at .39 Qts, is down 8.18 db from the midpoint when it hits it's free air resonance of 21 Hz. The Peerless, at a Qts. of .34, is down 9.4 dB from the midpoint.

For illustration, check out the output of the Swan 12 inch at http://www.madisound.com. Also, a Skaaning woofer response can be found at http://www.flexunits.com Click flex units-specification for 12"-. Note the specs page: Fs=25 Hz, Qts=.3, sensitivity=92 dB. Then click Frequency Scale.

Note that the speaker is 84 dB at 25 Hz resonance. The sensitivity is listed as 92 dB, but it sure looks like 94 dB from that chart.

In both the Skaaning speakers and the Swan speaker, the output starts rolling off around 60 or 70 Hz. Any speaker with a Q lower than 1 will do a gradual rolloff down to it's resonance frequency.

However when enclosed and ported, the story changes entirely. No more rolloffs from 70 Hz down.

The Shiva, for instance, when enclosed in a box equal to it's Vas, and tuned to it's free air resonance, (21 Hz), will be 3 dB down from it's midpoint.

PS: The chart on the Shiva white paper is for an enclosed woofer. It is not a free air chart, (I am not saying you thought it was).

[Edited by kelticwizard on 10-20-2001 at 08:33 PM]
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Old 21st October 2001, 02:06 AM   #16
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Super

Yes Klone-Audio is my site. The projects are a collaborative effort between JonMarsh and I. We've been designing and building speakers as a team for more than 30yrs.

Jon's finally frozen the X-1 top module XO design, I'll be uploading that data later this weekend. He decided to forgo a Audio-X-Press article for the SLAMM's, so everything will be posted to the website as the documentation is finished.

There will be an Audio-X-Press article published for the latest M8 project. Actually jteef might find these of interest, Focal 8V4211, combined with a MBQuart TT1. There's a thread about them on the DIY section of
http://www.htguide.com/CFBoards/index.cfm?CFB=1

Click the image to open in full size.
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Old 21st October 2001, 02:08 AM   #17
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Thomas W:

I freely bow to your superior audio knowledge as displayed at your excellent and informative website.

However, you did claim in your post that the Peerless has a rolloff below 70 Hz, and used the free air response as evidence.

Are you saying that this rolloff will occur if the Peerless is enclosed in a 2 cu. ft box and ported to 30 Hz?

If it does not occur in the enclosed box, why post the free air response as an illustration that it will?

Not all readers of a discussion forum post there. The enthusiastic novice unfamiliar with the way ported and sealed boxes work, when searching for his low frequency driver, may well be doomed to examining free air response chart after free air response chart, 70 Hz rolloff after 70 Hz rolloff, until he throws his hands in the air. Indeed, he is likely to conclude that flat response down to 30 Hz and below is a myth, as any examination of the manufacturer's free air response chart will show!

Surely, we don't want that to happen.

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Old 21st October 2001, 05:00 AM   #18
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jteef: Seas drivers are an excellent value for the money. Personally, I'm pretty much a Scanspeak only man nowadays, but I don't exactly have the funding for a few pairs of carbon fiber/paper cone drivers. However, for electronica, I'd more than likely sacrifice optimal midrange "warmth" for 2 drivers if cost permitted me to go with 4 good quality drivers for an MTM. In any event, it sounds like your going to be needing a sub, so I wouldn't fret too much over the f3 of your midrange drivers. In fact, considering the low, fast beats often found in electronica, you may want to consider the use of a multi driver sub, or better yet, stereo sub (or, theres always the "Grey option" of 12 subs, heh heh)
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Old 21st October 2001, 06:16 AM   #19
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Wiz

Items people should consider for subwoofer design include, cabinet/alignment, baffle shape/baffle size, cabinet construction, effects of room gain/room placement, size of room and desired SPL's.

For those designing subs on a budget, Unibox is a very good and accurate freeware modeling program, it doesn't have the glitches inherent in WinISD. For those with some disposable income, LspCAD/LspCAD Pro are extremely accurate and powerful modeling tools.

Hope this eliminates any possible confusion that was created

Regards
Thomas

BTW, guys what's wrong with using 12-12" subs?

[Edited by ThomasW on 10-21-2001 at 01:52 AM]
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Old 21st October 2001, 02:37 PM   #20
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My guess is your trying for something like Tony Gee's Proteus design. Try emailing him if you have a question.

I think I agree with Super, a sub might be essential for the low range. Being the bass head I am ! Something like the Seas P25REX might be good without killing you budget.

But as to the limited amount of knowledge I have, I think the rest of these guys in here could recommend some other(probably better) drivers.

Cheers
Jeremy Hopkins

BTW There is absolutly nothing wrong with 12-12" subs!
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