Hey guys...we need a little rallying here... - Page 118 - AVS Forum
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post #3511 of 11031 Old 04-04-2012, 01:21 PM
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It's supposed to be in phase for an LR xo. The xo may change the phase, but then measures should be taken to correct it. Typically this includes physical offset of the driver, polarity change, or phase delay network.

Model it and you'll see. Like I said though, a steep slope is less relevant.
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post #3512 of 11031 Old 04-04-2012, 01:44 PM
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Quote:
Originally Posted by noah katz View Post

Doesn't matter; my question was about the range past the -6 dB points.

It's still a more gradual transition past there. that means that you have to work harder to get phase aligned. Having good phase alignment, over roughly a 3 octave span on either side of the crossover, lets the speaker dissapear more easily.
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post #3513 of 11031 Old 04-04-2012, 03:35 PM
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Quote:
Originally Posted by tuxedocivic View Post

It's supposed to be in phase for an LR xo.

I know LR is in phase right at the XO freq, but does it maintain that on the downslopes?

If so, how far?

Pretty slick if it does that.

Noah
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post #3514 of 11031 Old 04-04-2012, 03:48 PM - Thread Starter
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"but does it maintain that on the downslopes?"

yes. noah, the phase of the two will be identical across the full spectrum. however, both will have 90 x 4 phase rotation. so while the phase will be the same between the two speakers, the phase will not be the same at all frequencies. there is a 360 roll from the mids to the bass. linkwitz indicates that this is not audible though.

Listen. It's All Good.
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post #3515 of 11031 Old 04-04-2012, 04:00 PM
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LTD02, it's 180d for an LR2 and 360 for LR4.

The phase alignment is the hardest part of an LR2. Because of the very wide bandwidth and need for phase alignment. 4th order and up are much easier because driver interaction is over a short bandwidth. Which is why I started by saying that the higher order cross overs don't need as much attention past the knee. BW crossovers seem to have more flexibility, because if 90d out of phase, there is still flat on axis summation. If its in phase, then there is a 3db hump, but power response will be flat (in theory, I've never done it personally).
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post #3516 of 11031 Old 04-04-2012, 04:11 PM
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Back to my original question and why is it not better to extend beyond crossover so the slopes and phase shift and attenuation is EQUAL!?

Seems like a bad idea to me to muddle whats going on in that region with the roll off of the box. Not to mention each AVR/processor's crossover implementation may be a little different.
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post #3517 of 11031 Old 04-04-2012, 05:56 PM - Thread Starter
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"LTD02, it's 180d for an LR2 and 360 for LR4."

right. and when combined with a sealed cab that has a natural second order rolloff, you get an lr4. together, these give a flat frequency response through the crossover region and matched phase response everywhere. this is why thx spec'd it this way.

all that said, bwaslo makes a good point about the practicality vs. theoretical aspect of these things. there are many designs and crossover points that will be 'good enough'.

Listen. It's All Good.
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post #3518 of 11031 Old 04-04-2012, 06:09 PM
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Yup. Down in the sub region, to much going on to try and use theory. I agree with LTD that sealed roll off usually only helps here.
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post #3519 of 11031 Old 04-04-2012, 06:31 PM
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Thanks.

Interestingly, some of the more sophisticated EQ systems like Trinnov and Dirac claim to fix, or at least improve, the phase response.

I don't believe it's generally agreed (i.e. Tom Danley) that the phase shift is inaudible.

Quote:
Originally Posted by LTD02 View Post

"but does it maintain that on the downslopes?"

yes. noah, the phase of the two will be identical across the full spectrum. however, both will have 90 x 4 phase rotation. so while the phase will be the same between the two speakers, the phase will not be the same at all frequencies. there is a 360 roll from the mids to the bass. linkwitz indicates that this is not audible though.


Noah
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post #3520 of 11031 Old 04-04-2012, 06:51 PM - Thread Starter
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"I don't believe it's generally agreed (i.e. Tom Danley) that the phase shift is inaudible."

agree. iirc, bag end employs a second order cross on their subs in order to keep the phase of the bass as close to the phase of the mains as possible. dr. g. also does something similar (sealed mains full range and acoustic 2nd order low pass subs).

most folks have much more to worry about though, but your point is well taken.

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post #3521 of 11031 Old 04-04-2012, 07:22 PM
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I'm interested in the smaller waveguides and don't want to wait for the plastic versions of the SEOS 6 or 8. I've been looking at the Denovo DW-654S (6 X 4.5 X 3.75 deep elliptical) that has been ordered and takes a standard screw-on driver (1 3/6 - 18 TPI). I think all of Erich's drivers are bolt-on so I'm ruling those out (correct me if I'm wrong here).

Any recommendations out there for a screw-on driver? The xover would be in the 2.5 - 3.5 KHz range so going low isn't a requirement. My comfort range is $50-$75 per driver.

Regards...
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post #3522 of 11031 Old 04-04-2012, 07:34 PM
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An SB29 dome in the Dayton 8" round horn (doesn't thread, requires modification) hold directivity down to 1500hz and only needs two small components to get flat to 1500hz LR4. I've power tested it to 128 watts and it didn't flinch. Only issue is sensitivity, but there aren't many woofers with much more than 90db sensitivity that are 8" anyways, and after baffle step I'm not sure there are any.
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post #3523 of 11031 Old 04-04-2012, 11:02 PM
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Quote:
Originally Posted by ernperkins View Post

I'm interested in the smaller waveguides and don't want to wait for the plastic versions of the SEOS 6 or 8. I've been looking at the Denovo DW-654S (6 X 4.5 X 3.75 deep elliptical) that has been ordered and takes a standard screw-on driver (1 3/6 - 18 TPI). I think all of Erich's drivers are bolt-on so I'm ruling those out (correct me if I'm wrong here).

Any recommendations out there for a screw-on driver? The xover would be in the 2.5 - 3.5 KHz range so going low isn't a requirement. My comfort range is $50-$75 per driver.

Regards...


There will be a very small neo magnet compression driver coming that will do nicely on those little waveguides. Not sure how loud you need things to go though. Hoping they will be here in about a month or so.
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post #3524 of 11031 Old 04-05-2012, 01:59 AM
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Thanks for the useful feedback, Ribaudio. You say that less is better. For me it is hard to imagine that the 1" driver will cover the range from 800 Hz up. I will recalculate the box as a 2-way design. It will be easier to balance 2 instead of 5 speakers. have a nice day - Marc
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post #3525 of 11031 Old 04-05-2012, 10:25 AM
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Quote:
Originally Posted by tuxedocivic View Post

An SB29 dome in the Dayton 8" round horn (doesn't thread, requires modification) hold directivity down to 1500hz and only needs two small components to get flat to 1500hz LR4. I've power tested it to 128 watts and it didn't flinch. Only issue is sensitivity, but there aren't many woofers with much more than 90db sensitivity that are 8" anyways, and after baffle step I'm not sure there are any.

Someone once said "Turns out the SB is a freakin' TANK!!!" I just don't have the real estate for the 8" guide Ryan. I'm pretty much stuck to the small Denovo elliptical (retrofitting an existing cabinet). I love the SB29's and have a pair of the neo's, but they're slated for car use.


Quote:
Originally Posted by Erich H View Post

There will be a very small neo magnet compression driver coming that will do nicely on those little waveguides. Not sure how loud you need things to go though. Hoping they will be here in about a month or so.

Eric - will this be a a different driver than the Denovo Mini-Elliptical horn? I have that and it's nice, but I was looking for a "step up" screw on.

Thanks to both of you .....
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post #3526 of 11031 Old 04-05-2012, 01:41 PM
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Oh, you saw my compression testing thread on TT I see! Ha, ya it is a tank. My sweeps with a single cap filter were insanely loud. I can't kill it. I accidentally did a very high volume full range sweep on it outside a while ago. Made an absolute racket. Was just fine though

Good luck finding what you're looking for. Sound fun. I like small speakers.
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post #3527 of 11031 Old 04-05-2012, 01:42 PM
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Quote:
Originally Posted by Toscano View Post

Thanks for the useful feedback, Ribaudio. You say that less is better. For me it is hard to imagine that the 1" driver will cover the range from 800 Hz up. I will recalculate the box as a 2-way design. It will be easier to balance 2 instead of 5 speakers. have a nice day - Marc

You'd be surprised! When I first started using compression drivers in home speakers I was skeptical about using them that low as well. I tried horn/8/15 crossed at 2k/300 and then horn/12/15 crossed at 1.4k/200 but ultimately ditched the midrange for horn/15 crossed at 900. I have had pretty serious power on the setup (100x2 to comp drivers and 400x2 to 15s) and even very loud the power handling of the compression drivers has never been a problem.

FYI, A few things make this possible. Even though the exit of the compression driver is 1" the actual diaphragm is 1.75" which has about 3 times the area of a 1" dome. Going down 1 octave at the same SPL requires 4x the displacement, so just by that factor you could take the compression driver down almost an octave lower than a 1" dome. Also 1" dome on a baffle is radiating it's sound roughly into a half sphere (front of the speaker). Suppose you have a waveguide that directs sound into a 90 degree cone. You will be dissipating the same power over roughly 1/3 of the area which means 3 times the intensity or +4.8 dB SPL for the same power coming out of the speaker. This effect will be greater for the SEOS because it's 90x60. There are some other effects like horn loading, but just from these two you can see how a 1" exit compression driver on a horn can play an octave lower at 6 dB louder than a 1" dome tweeter. The real problem is making a good compression driver and a good horn but here all of this is done!
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post #3528 of 11031 Old 04-05-2012, 03:41 PM
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Quote:
Originally Posted by Toscano View Post

There are some other effects like horn loading,...

That's actually the most significant, increasing the output for the same excursion by at least 10 dB.

Noah
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post #3529 of 11031 Old 04-07-2012, 04:53 PM
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Looking for suggestions on what would be the best 15" woofer to pair with the SEOS 18. Please don't suggest the AE TD15M because I'm part of the Group Buy which may or may not be consummated.

I've thought of just going with the same B & C drivers that Geddes used in the Summa. Do I really need the high extension of the TD15M since with the SEOS 18 you should be able to cross in the 800hz. to 900hz region.

If my TD25Ms finally appear, I could easily sell them or pull a switch with the B &C's. I'll most likely be using an active crossover.
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post #3530 of 11031 Old 04-07-2012, 05:14 PM
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Quote:
Originally Posted by rajacat View Post

Looking for suggestions on what would be the best 15" woofer to pair with the SEOS 18 ...

I suggest that you take a look at the RCF L15P200AK. Parts Express has them. This is a grand 'ol driver that keeps getting overlooked.

Or snag a pair of used JBL 2226H drivers off of EBay. They can usually be had for under $200 each if you are patient.

The GPA 416-8C is another good driver. This one is a remake of a classic by Altec Lansing.
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post #3531 of 11031 Old 04-07-2012, 05:33 PM
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Thanks Carl,\\
I'm going to keep my eyes open for a pair of the JBLs. The RCF L15P200AKs are a little out of my price range. BTW I'd like to keep the cost under $250/ea. Too bad the new Dayton Audio DS315-8 12" Designer Series Woofers aren't made in a 15" version although I'd like to see a few reviews first they might be good enough. Perhaps they'll introduce a 15 incher. It would be nice to save a few $'s.

I sure wish the AE Group Buy would work out.
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post #3532 of 11031 Old 04-07-2012, 11:25 PM
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Quote:
Originally Posted by rajacat View Post

Thanks Carl,\\
I'm going to keep my eyes open for a pair of the JBLs.

If you want to do something crazy, I've got some of the 16 Ohm versions of the JBL. You'd need 2 per cabinet though if you wanted 8 Ohm.



Update:

All the parts have now been shipped to one location and are being packaged up. Shipping is suppose to be April 16. In the future it won't take this long for the compression drivers. The reason it took extra time was because I had to figure out how to get everything shipped to one place, and then set up all the international shipping info. So it will be quicker when it's done again. Some of this is new to me which took extra time to figure out.
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post #3533 of 11031 Old 04-08-2012, 12:14 AM
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Quote:
Originally Posted by Erich H View Post

If you want to do something crazy, I've got some of the 16 Ohm versions of the JBL. You'd need 2 per cabinet though if you wanted 8 Ohm.



Update:

All the parts have now been shipped to one location and are being packaged up. Shipping is suppose to be April 16. In the future it won't take this long for the compression drivers. The reason it took extra time was because I had to figure out how to get everything shipped to one place, and then set up all the international shipping info. So it will be quicker when it's done again. Some of this is new to me which took extra time to figure out.

you might consider doing the pre order give away before every thing arrives just to get it done to not hold up the shipping on the other stuff.
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post #3534 of 11031 Old 04-08-2012, 01:01 AM
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Quote:
Originally Posted by rajacat View Post

Too bad the new Dayton Audio DS315-8 12" Designer Series Woofers aren't made in a 15" version although I'd like to see a few reviews first they might be good enough. Perhaps they'll introduce a 15 incher. It would be nice to save a few $'s.

From what I read about the designer series at parts express, they don't seem to employ any attempt at demodulation in those motors. The thread indicated a good bit of audible distortion at higher drive levels.

Quote:


Looking for suggestions on what would be the best 15" woofer to pair with the SEOS 18. Please don't suggest the AE TD15M because I'm part of the Group Buy which may or may not be consummated.

This one:

http://bmsspeakers.com/fileadmin/bms...320_t_data.pdf
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post #3535 of 11031 Old 04-08-2012, 06:46 AM
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Quote:
Originally Posted by Eternal Velocity View Post

From what I read about the designer series at parts express, they don't seem to employ any attempt at demodulation in those motors. The thread indicated a good bit of audible distortion at higher drive levels.



This one:

http://bmsspeakers.com/fileadmin/bms...320_t_data.pdf



Where can you buy BMS stuff in the US?
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post #3536 of 11031 Old 04-08-2012, 07:00 AM
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http://www.assistanceaudio.com/assis...bms_cones.html
They are the North American distributor. Their area code maps to Utah.

Price for the listed item is not too bad. I like the triple shorting rings in the design.
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post #3537 of 11031 Old 04-08-2012, 09:33 AM
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Erich,

I might be interested in those 16 ohm JBLs. My current speakers are running 16 ohms with a pair of modded Heathkit W5M's with no strain at all. The trannys have 4-8 & 16 ohm taps. They output 25 strong tube watts. I rarely reach 12 o'clock on my AVA T7 pre.

-Roy

What would I gain other than higher efficiency by running the JBL in series? Space, cabinet size, isn't a limiting factor for me but I don't regularly play at high volumes. As they say, there's no substitute for displacement. Would I get lower distortion, a greater sense of musical texture or what?
90% 2 channel music, 10% home theater.
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post #3538 of 11031 Old 04-08-2012, 11:43 AM
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Originally Posted by cookieattk View Post

you might consider doing the pre order give away before every thing arrives just to get it done to not hold up the shipping on the other stuff.

Not necessarily a good strategy. First he should ensure people's commitment to the purchase by either including the giveaway with the shipping or shipping it later. Otherwise he may receive unexpected cancellations after people receive "their" giveaway.

Ignorance more frequently begets confidence, than it does knowledge. Charles Darwin
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post #3539 of 11031 Old 04-08-2012, 12:28 PM
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Quote:
Originally Posted by GRBoomer View Post

http://www.assistanceaudio.com/assis...bms_cones.html
They are the North American distributor. Their area code maps to Utah.

He's infamous for not returning calls or emails. I actually rang to place an order for several 18" drivers that he said he had in stock. It took several calls before he answered (not machine) and he needed to find out shipping costs. Multiple more calls and emails went unanswered so I thought, sod him and bought other drivers.
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post #3540 of 11031 Old 04-08-2012, 02:29 PM
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Quote:
Originally Posted by rajacat View Post

Erich,

I might be interested in those 16 ohm JBLs. My current speakers are running 16 ohms with a pair of modded Heathkit W5M's with no strain at all. The trannys have 4-8 & 16 ohm taps. They output 25 strong tube watts. I rarely reach 12 o'clock on my AVA T7 pre.

-Roy

What would I gain other than higher efficiency by running the JBL in series? Space, cabinet size, isn't a limiting factor for me but I don't regularly play at high volumes. As they say, there's no substitute for displacement. Would I get lower distortion, a greater sense of musical texture or what?
90% 2 channel music, 10% home theater.

if u go active with 2226 u can go from 35-1300hz f3 of 30ish flat to about 100db before thd spikes in the 30-40 range.
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