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#1 of 31 Bryan Michael

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Posted November 02 2004 - 05:45 PM

ok i am bulding a new theater. it will be 16 ft by 30 with 9 ft celing i will be having a 160 in screen and my front seating will be 17 ft back with 2 more rows. i have dual av15 for a sub and it is fine but i want a good diy speaker to replace my speakers. i have the sunfire sig 7 with 400 a channel for a amp.

what would you recomend for a 7 channel setup. and stay under 7k for all 7 speaker kits.
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#2 of 31 Jeff Elliott

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Posted November 03 2004 - 12:08 PM

I built the GR-Research AV-3's for left, center, right. I'm still working on side and rear surrounds, but will likely be building a variant of the AV-1RS.

They sound great so far and I'm pleased with the purchase. They're reasonably laid back and easy to listen to. They play low and integrate well with my two AV-15's.

Staying under $7K will be no sweat with this line from GR Research. Here's a link to their site.

Good luck with your search!
Jeff

#3 of 31 Bryan Michael

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Posted November 03 2004 - 02:31 PM

i was looking at them i just hope the size of the theater will not be to bog for them.
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#4 of 31 Paul Spencer

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Posted November 03 2004 - 02:48 PM

At that price you can get something VERY impressive. High up on my shortlist would be BESL. You can also get the series 2.5 version which is suitable for a centre channel.

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Also consider North Creek Vision kit - designed for HT in particular.

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If you want more low end, then look at the Rhythm kit ... North Creek kits
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One thing to keep in mind is that drivers are often not consistent enough to build a speaker based on someone's crossover design. This is why a little extra service is better - like with North Creek where they match the drivers . Otherwise it can be a little hit and miss. If you don't get good service, then you might as well source the drivers and crossover parts yourself and go with a design, such as those found on the Seas website, or copy the crossover for some kit. I suggested the above as they seem to offer good service.

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#5 of 31 Paul Spencer

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Posted November 03 2004 - 02:50 PM

You could also get bookshelf pairs and put them back to back to get dipoles.
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#6 of 31 ThomasW

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Posted November 03 2004 - 02:55 PM

Bryan,

There is a limit to the output available from smaller midwoofers. It's called radiation resistance.

Larger drivers don't have to work as hard, so they can play louder and still keep the distortion low.

Your room is quite large. You might want to consider some speakers that utilize drivers with larger radiating area, particularily if you like to turn it up.....

#7 of 31 Paul Spencer

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Posted November 03 2004 - 03:38 PM

Hmmmm, I wasn't thinking about the large room.

17 ft = 5m

Typical floorstanding speakers = 88dB 1w 1m
>>> 82dB 1w 2m
>>> 76dB 1w 4m
>>> 73dB 1w 5m
>>> 71db 1w back row

10w >>> 83 dB front row
50w >>> 90 dB front row

To achieve 105 dB at your seating position would be a fair challenge. Did you say you have 400w RMS for each channel? If the "typical floorstanders" could handle this much power, you could get 99dB, but they almost certainly can't. Instead a small array of midbass drivers would suit better.

An 8 driver array gives you 4x power handling and +6dB of efficiency (compared to a typical MTM floorstander). This means

200w >>> 102 dB front row

Double the SD (say go up to 8" drivers) and you can probably get

400w >>> 108 dB front row

But you have to then cross lower and increase the demands on the tweeters.

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#8 of 31 ThomasW

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Posted November 03 2004 - 04:41 PM

Below is a pic of a DIY design (not a kit) using the famous Vifa XT-25 ring radiator and 8" alu-magnesium woofers from Hi-Vi Research.

The raw parts cost excluding cabinets is approx $350/speaker.
These have enough radiating area and power handling to do a good job in your larger room.

Posted Image

There are several pairs built and lots of info about them available.

If you're interested shoot me an email and I'll put you in the loop.

Here's another version, they haven't been veneered yet

http://www.htguide.c....achmentid=1205

#9 of 31 Paul Spencer

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Posted November 03 2004 - 04:55 PM

Wow! Those are fantastic looking drivers!

They do seem like a difficult mix though - 8" woofers and the XT tweeter. I can imagine a xo would be difficult. What crossover point and slopes were used?

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#10 of 31 Paul Spencer

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Posted November 03 2004 - 04:56 PM

Do you have a link to info on those drivers?
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#11 of 31 ThomasW

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Posted November 03 2004 - 05:16 PM

This is a variant of a TM design my friend Jon designed and published in the Sept/Oct/Nov 2003 issues of AudioXpress.

The XO point is 1.25kHz and uses a very sophisticated high-order cauer/elliptical filter.

Here's a link to the spec sheet for the 8"s

#12 of 31 Paul Spencer

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Posted November 03 2004 - 05:35 PM

What is the slope? I heard of those filters some time ago. How sensitive is the design to driver to driver inconsistencies? It always seems a concern that this will mean a copy will be sub-optimal without measurement ability on the part of the constructor.
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#13 of 31 ThomasW

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Posted November 04 2004 - 02:09 AM

Quote:
What is the slope?
The slope varies with frequency. It's starts as a standard 4th order L-R, then works like an 8th order L-R in the transistion region.

Quote:
How sensitive is the design to driver to driver inconsistencies?
No more sensitive than any 4th order L-R which is what it's based on.

Here's a link to the schematic drawing for the XO's

#14 of 31 Bryan Michael

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Posted November 04 2004 - 04:39 AM

thomasw so you think the speaker with the vifa will do better than the av series from gr? on the sides i want a di poll on the sides and direct on the back. my true goal of the theater is 3 rows of confe seating and a 160 in screen. i am bulding a house next year and i took over the basement.
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#15 of 31 ThomasW

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Posted November 04 2004 - 06:46 AM

The output level from a standard cone type loudspeaker attenuates (drops) 6dB for every doubling of distance from the speaker.

If you're sitting 12' from the speakers, the sound at the listening position will be 12dB lower than a measurement 3' from the speakers. Note that a 10dB change in output level, means 10 times more amplifier power is needed.

5.25" midwoofers have roughly 95sq cm of surface area and 3mm of Xmax.

A typical 8" midwoofer will have roughly 220sq cm of surface area and an Xmax of 6mm.

It's pretty obvious which driver or drivers will be capable of moving the greatest amount of air, and therefore able to play louder with lower levels of distortion.

For smaller rooms with closer listening positions this isn't a issue. In your room, I think it's something to take into consideration.

#16 of 31 Greg Monfort

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Posted November 07 2004 - 04:25 PM

I recommend the same as I usually do in larger rooms where cost is an issue, Adire HE12.1s since they're ~96dB sensitive, have better controlled/narrower polar responses to interact less with the room, ergo getting more of their output to the listening position than typical cone/dome speakers. They are fairly efficient, a must in apps where there's not much/any room gain, and last, but not least, you listen to horn loaded systems in the theater and they give you a bit of their performance 'flavor' to make it a more cinema-like experience at ~dirt cheap prices.

Really, at your budget level, available space and listening distance, it's tempting to recommend some higher quality/priced co-axes with a helper woofer, or even a full tilt boogie large short throw horn/15" or 18" two-way small cinema design to get the 'sound' and vanishingly low distortion of a true HE system.

I don't quite follow some of what's already been posted WRT power requirements, but as already ~noted, sound pressure falls 6dB/doubling of distance in free space, though in your room probably only a portion of the upper BW will actually do it due to some reverberation, but I figure it's best to calc things based on a ~worst case scenario.

Since speakers are normally rated at 1m and yours will be near enough to a wall to put them in half space, then 17ft back there's a max theoretical loss of 20*log10(17/3.28084) = ~14.3dB, so to reach DD/DTS reference levels requires (~14.3+105)-96 = ~23.3dB, or 2^(23.3/3.01) = ~213.9W max required with this speaker, well within its electro-mechanical ~linear rating, so distortion should be acceptably low even in the last row once the room's effects are factored in.

Anyway, with the formulas you can figure the requirements for other suggestions if you don't like mine.

GM
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#17 of 31 Danny Richie

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Posted November 08 2004 - 12:43 PM

The very idea that a woofers output across the board is limited by its size is false.

This line of thinking is only valid in regards to low frequency signals.

If a sub-woofer is used to cover the first octave and a half then driver size verses output capability is a non issue (within reason).

Quote:
on the sides i want a di poll on the sides and direct on the back.


A dipole design will not accurately reproduce the signal that is sent to it. It gets "rear" info. Reflecting part of that "rear" signal to the front of the room to be heard reflecting from the front wall, and part of it coming back to you reflected from the rear wall is messed up (to sum it up bluntly).

There is a better way.

Danny Richie

#18 of 31 Hank Frankenberg

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Posted November 08 2004 - 12:55 PM

Quote:
A dipole design will not accurately reproduce the signal that is sent to it.

Quote:
Reflecting part of that "rear" signal to the front of the room to be heard reflecting from the front wall, and part of it coming back to you reflected from the rear wall is messed up (to sum it up bluntly).

So THAT'S the bone of contention I've been wondering about!

It's been peaceful between Danny and the Poohbahs for a long time, and I've enjoyed the peace, but I do see the issue. Danny, is your point related to the Bose 901 Direct/Reflecting speaker that was all the rage, but ignored by the audiophiles because of it's huge percentage of reflected sound, which was, indeed unnatural?

Thomas, I've never thought of this question, but what percent of its sound does a dipole direct rearward?

I just know I'll regret fomenting this "discussion". If only egos could be checked at the door like pistols.

#19 of 31 Danny Richie

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Posted November 08 2004 - 01:38 PM

Quote:
Danny, is your point related to the Bose 901 Direct/Reflecting speaker that was all the rage, but ignored by the audiophiles because of it's huge percentage of reflected sound, which was, indeed unnatural?


There is nothing wrong with utilizing reflected energy so long as when the signal reaches your ear it accurately reproduces the signal that it was supposed to.

Obviously sending high frequency in one direction, mids one way and lows another will not be accurate and could indeed be called unnatural.

For example, many times in movies an effect will be that you are in the middle of the action and whatever is a main focus is supposed to make a lap around you in a circle motion.

For the system to accurately play this back then a rear set of speakers will be needed to produce a signal that will match the sound from the front speakers and make you believe that it passed behind you.

Sound must be localized from behind you in some way.

A side mounted dipole design will not do this.

It will create a big spacious sounding sound field with effects happening all around and some like that, but it is not accurate.

Danny

#20 of 31 Hank Frankenberg

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Posted November 08 2004 - 02:05 PM

Okay, I knew that, and of course a dipole midrange/midwoof coupled with a bipole high end would not be right, but I was referring to the original Bose 901 that "made" Bose. It had like 9 rear-firing and two front-firing "full-range" drivers. If my count is off, I'm sorry - it's been many years, but the point is that speaker was UNNATURAL sounding. WAY too much rear-directed sound that didn't mimic anything in nature or on a symphonic hall soundstage or a small jazz club, BUT it was impressive because it "enveloped" the listener in sound. It was a new sound experience, and with all the marketing hype, many people bought into the concept (just like Bose marketing $$ influences consumers to this day).


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