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post #61 of 79 Old 12-10-2013, 04:34 PM - Thread Starter
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Originally Posted by BeeMan458 View Post

Just saying, the Linkwitz is way beyond my personal experience.

Using our room measurements, the graph is telling me the gain on your subwoofers is set a bit high by 5dB to 10dB when compared to the gain of the center channel.

Yea, that was pre-EQ. The post EQ graphs are in post #28. What's your thoughts on those?

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post #62 of 79 Old 12-10-2013, 04:41 PM
 
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eek.gif Those are about the sweetest graphs I've seen. eek.gif

In your question to me, what are your worrying about?
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post #63 of 79 Old 12-10-2013, 06:23 PM - Thread Starter
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Well, sealed subs roll off at 12 dB/octave, so I just don't know how much steeper an HPF should be implemented in a situation where dissimilar subs are integrated and the goal is to use the lesser sub higher up in the driver's range in the hope of preserving headroom so they can keep up with the more capable drivers they're paired with. My CHT subs give me extension to 25-30 hz naturally in my room and my thought was to high pass them so they have more headroom in the critical 50-70 Hz range where the mid-bass kick seems to really get you in the chest.

So, that's why smile.gif. Should I be implementing a shallower rolloff for reasons related to the sealed subs native box rolloff? Am I introducing some potentially audible anomaly by rolling off so steep? And am I really gaining any headroom by high passing the lesser single 18's?

If I wasn't thinkin' of something I'd be bored to tears biggrin.gif

Oh, and thanks for the kind words there on the FR. I'm really liking what I hear. But I'm still open to potential areas of improvement. wink.gif

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post #64 of 79 Old 12-10-2013, 06:33 PM
 
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My understanding, contrary to popular dictum, it's about the stronger sub, not the weaker sub.

When the weaker sub drops out (the weak link) one is left with the stronger sub. The question becomes, in the case of the lower octave where the weaker sub drops out; what happens? In my opinion, two thing will happen, a null can develop because not as many subs are filling in the voids room acoustics create and second, the question morphs, will the stronger sub be able to stand alone during the moment it's called upon to carry the sound track by itself? At the time the weaker sub drops out, one loses the synergistic addition of the weaker subwoofer and then, the sonic chain becomes about the stronger subwoofer as the graph collapses accordingly.

Yes, the weaker sub will fill in the mid-bass range but as to which HPF setting to use, will depend on the phase alignment of the ported vs the sealed, and what distance each is placed from the MLP: not to mention the affect of cabin gain on the left side of the graph. Stating the obvious, the user wants everything to arrive at the same time.

I see mixing sealed with ported being a case of dealing with phase alignment issues as I would suspect one would want the HPFs to be set equally.

I'd run a series of sweeps, using a continuous phase correction (make fifteen degree changes, measure and repeat) to see how changing the phase affects the graph. REW will pickup and display a change of a few degrees. It's surprisingly sensitive in this way.

What's the purpose of the exercise? What is it you don't like about the graph? And forgive my above if you're already onto what I was going on about.

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post #65 of 79 Old 12-10-2013, 07:49 PM
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Quote:
Originally Posted by Gooddoc View Post

Well, sealed subs roll off at 12 dB/octave, so I just don't know how much steeper an HPF should be implemented in a situation where dissimilar subs are integrated and the goal is to use the lesser sub higher up in the driver's range in the hope of preserving headroom so they can keep up with the more capable drivers they're paired with. My CHT subs give me extension to 25-30 hz naturally in my room and my thought was to high pass them so they have more headroom in the critical 50-70 Hz range where the mid-bass kick seems to really get you in the chest.

So, that's why smile.gif. Should I be implementing a shallower rolloff for reasons related to the sealed subs native box rolloff? Am I introducing some potentially audible anomaly by rolling off so steep? And am I really gaining any headroom by high passing the lesser single 18's?

Play a worst case scenario disc (eg. WotW - Pod emergence scene) at the max volume you would ever listen to it. If the CHT subs are able to keep up you probably don't need to be concerned about headroom. If they can't keep up however you could just lower the gains on the CHT's a few dB and raise the gains on the S2's to compensate. Adjusting gains seems like a better method of optimizing headroom than playing with HPF's.
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post #66 of 79 Old 12-10-2013, 07:59 PM - Thread Starter
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Quote:
Originally Posted by BeeMan458 View Post

My understanding, contrary to popular dictum, it's about the stronger sub, not the weaker sub.

When the weaker sub drops out (the weak link) one is left with the stronger sub. The question becomes, in the case of the lower octave where the weaker sub drops out; what happens? In my opinion, two thing will happen, a null can develop because not as many subs are filling in the voids room acoustics create and second, the question morphs, will the stronger sub be able to stand alone during the moment it's called upon to carry the sound track by itself? At the time the weaker sub drops out, one loses the synergistic addition of the weaker subwoofer and then, the sonic chain becomes about the stronger subwoofer as the graph collapses accordingly.

Yes, the weaker sub will fill in the mid-bass range but as to which HPF setting to use, will depend on the phase alignment of the ported vs the sealed, and what distance each is placed from the MLP: not to mention the affect of cabin gain on the left side of the graph. Stating the obvious, the user wants everything to arrive at the same time.

I see mixing sealed with ported being a case of dealing with phase alignment issues as I would suspect one would want the HPFs to be set equally.

I'd run a series of sweeps, using a continuous phase correction (make fifteen degree changes, measure and repeat) to see how changing the phase affects the graph. REW will pickup and display a change of a few degrees. It's surprisingly sensitive in this way.

What's the purpose of the exercise? What is it you don't like about the graph? And forgive my above if you're already onto what I was going on about.

-

I like my graphs, but sometimes the graph doesn't tell the whole story. Btw, they're both sealed subs, it's just the JTR's are more capable.

Edit: also, thanks for the well thought post! My post below has some graphs that show the system holds together well at least up to reference level soundtrack SPL.

JTR Noesis 212HT x 3 (LCR) powered by Lab Gruppen 10000Q amp
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post #67 of 79 Old 12-10-2013, 08:03 PM - Thread Starter
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Quote:
Originally Posted by henrich3 View Post

Play a worst case scenario disc (eg. WotW - Pod emergence scene) at the max volume you would ever listen to it. If the CHT subs are able to keep up you probably don't need to be concerned about headroom. If they can't keep up however you could just lower the gains on the CHT's a few dB and raise the gains on the S2's to compensate. Adjusting gains seems like a better method of optimizing headroom than playing with HPF's.

The gains on the CHT's were dictated by the nulls they were filling. They were added to the system in a Geddes like fashion to fill nulls, so reducing their gains introduces the nulls again. I high passed them because the nulls I needed filling were 50 Hz and above.

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post #68 of 79 Old 12-10-2013, 09:41 PM
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Geddes' goal, as I understand it, is smooth frequency response across a wide seating area. From what I've read he doesn't seem too concerned with maximizing SPL (headroom) or optimizing low frequency extension. My goal is high performance audio at the MLP. Two good, well positioned subs and some PEQ are sufficient to achieve that. To achieve Geddes' goal involves more subs, more effort, and a different set of challenges & compromises than what I've had to deal with.

You said "If I wasn't thinkin' of something I'd be bored to tears". I think optimizing your HT using the Geddes method should keep your mind occupied for quite some time... wink.gif
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post #69 of 79 Old 12-10-2013, 10:34 PM - Thread Starter
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Quote:
Originally Posted by henrich3 View Post

Geddes' goal, as I understand it, is smooth frequency response across a wide seating area. From what I've read he doesn't seem too concerned with maximizing SPL (headroom) or optimizing low frequency extension. My goal is high performance audio at the MLP. Two good, well positioned subs and some PEQ are sufficient to achieve that. To achieve Geddes' goal involves more subs, more effort, and a different set of challenges & compromises than what I've had to deal with.

You said "If I wasn't thinkin' of something I'd be bored to tears". I think optimizing your HT using the Geddes method should keep your mind occupied for quite some time... wink.gif

Well said. My approach is not really Geddes, but maybe a Geddes/Welti hybrid. I share his goal of excellent uniform FR across my seating positions, but I want headroom and extension as well.

What I really want is a Welti/Harman approach, but I'm currently stuck with disparate subs that makes their approach, well....complicated.

At this point I've measured and have a consistent full range FR response up to 105 dB.


I have sufficient sub headroom to at least 115 dB, but the disparate subs start causing some anomalies above the HPF.


So until I get me a couple more JTR subs or build some equivalent DIY, I think I'm as good as I'm going to get, but I do want more bass headroom than I have now, that's for sure.

The "if I wasn't thinking of something" comment was a bit facetious. I'll be glad to be done with it and just enjoy for a while. biggrin.gif

I do still wonder about that 48 dB HPF though...

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post #70 of 79 Old 12-11-2013, 02:11 AM
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Geddes did not say you could not use a more powerful sub or should sacrifice extension, lol. He just said 3 subs will give a more even FR.

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post #71 of 79 Old 12-11-2013, 04:02 AM - Thread Starter
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Lol, I agree. As is often the case though, positions are polarized to make a point. biggrin.gif

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post #72 of 79 Old 12-11-2013, 04:39 AM
 
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Reads like it's time to sell the lesser two subs and bring a matching third sub into the picture. Selling the two weaker subs should keep your mind and body busy for about a month. tongue.gif
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post #73 of 79 Old 12-11-2013, 06:08 AM - Thread Starter
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I've not been able to get a flat response across all my listening positions with 3 subs. Very close, but not quite. There always seems to be a null that requires that 4th sub. I can get two subs to look just about the same as three.

Kind of strange, I know, but that's my room.

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post #74 of 79 Old 12-11-2013, 06:15 AM
 
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The idea being, get rid of the two lesser subs as that's always a "HUGE" hassle. With the recooped monies, add a third, better sub to match the two greater subs that you already have and when able, add the much needed fourth sub.

Doing it this way, you're moving forward in a positive direction as opposed to playing dinky-doo with what you currently have.

Just saying, the CHT 18.1s aren't even close to the output capability of the S2s. If I'm reading online information correctly, in comparison, the 18.1s are a drop in the bucket and don't dig anywhere near as deep as you're pushing water uphill with a broom by trying to meld these two, "vastly" disparate systems together.



images?q=tbn:ANd9GcRjHG2on9HTVEau_0KIoaMjZPBfl8KajYt6a2xOM3Rj6T42uUx9ZQ

Just saying. tongue.gif

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post #75 of 79 Old 12-11-2013, 06:47 AM
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If the CHT's are running out of steam before the S2's, I don't know how to fix that other than to lower their gains and let the S2's carry the heavier load or replace the CHT's with S2's. PEQ can fix irregularities at the MLP but may make it worse for other locations.

There's nothing wrong with a goal of having a flat FR across a wide area. It does involve more work & expense to get right however. In many situations there's only one person who truly cares about optimal performance and that's the person sitting in the MLP chair. If a secondary location has a high Q null or a FR that's a bit less flat than the MLP, will the person sitting there know or care? Friends who stop over for movie nights at our place listen to movies on TV speakers when they go home, so they're not critical listeners. They're thrilled with the sound here even though it's not quite as flat as it is in the MLP. Everyone's situation is different however and I don't mean to sound critical of anyone who wants to persue the goal of flat response everywhere. It's just that when the suggestions turn to buying additional expensive subs to accomplish that goal it may be worth pointing out that the people who would benefit from that expenditure may not care.
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post #76 of 79 Old 12-11-2013, 07:00 AM
 
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Quote:
Originally Posted by henrich3 View Post

It's just that when the suggestions turn to buying additional expensive subs to accomplish that goal it may be worth pointing out that the people who would benefit from that expenditure may not care.

Just saying, my recommendation is well within the poster's budget as they would be selling two CHTs so as to buy a third S2 in which to compliment their already existing pair of S2s. In my defense, the recommendation is not to someone who has a pair of budget minded subwoofers.
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post #77 of 79 Old 12-11-2013, 01:10 PM - Thread Starter
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I like to sit wherever I want when I'm watching a movie. So my goals are that I can. No doubt it's harder and more expensive, but that's why I consider it a hobby. biggrin.gif

It's correct that most people don't listen critically enough for it to make any difference and my worst seat smokes anything most people have ever heard outside a good theater, so it's really not so much for them as it is me. But most people also have no idea that they could be sitting right next to someone and be having a different audio experience. They might be asking where the MLP is if they did wink.gifbiggrin.gif

In the end, low seat-to-seat variability is just another priority, like many other facets of audio from aesthetics to amps.

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post #78 of 79 Old 12-11-2013, 02:34 PM
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It's correct that most people don't listen critically enough for it to make any difference and my worst seat smokes anything most people have ever heard outside a good theater...

Based on the charts you posted, your worst seat smokes anything most people have ever heard INSIDE a good theater as well! biggrin.gif
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post #79 of 79 Old 12-11-2013, 07:01 PM - Thread Starter
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Based on the charts you posted, your worst seat smokes anything most people have ever heard INSIDE a good theater as well! biggrin.gif

Lol, thanks man! I'm lucky to have found my way to the JTR/Seaton/Danley/DIY, etc., etc. world. These products are built to exceed expectations. smile.gif

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