Highest frequency that cannot be "localized" by the ear?

[Sir Terrence the Terrible]

So am I corrrect to assume then for the best two channel system in which I cannot place the subwoofer inbetween the speakers (becasue of a tv), it is best two have a pair of subwoofers in which they are located near each monitor speaker. In other words I should not have a singe subwoofer in the corner of a room?

Tom Nousaine has measured many subwoofers in many positions including multiple subs(2,3,4,5 close to mains) and according to his measurements a single sub in a corner still measures the best. A subwoofer sitting between two main speakers is not likely to excite any of the rooms modes efficiently which will cause some some suckouts in the frequency response at the listening position. According to his testing, a subwoofer SHOULD excite all of the rooms modals to measure and sound good. While placing a sub between the mains may assist in better integrations with the mains, it will likely cause the frequency response of the sub to be uneven.

[kexodusc]

Tom Nousaine has measured many subwoofers in many positions including multiple subs(2,3,4,5 close to mains) and according to his measurements a single sub in a corner still measures the best. A subwoofer sitting between two main speakers is not likely to excite any of the rooms modes efficiently which will cause some some suckouts in the frequency response at the listening position. According to his testing, a subwoofer SHOULD excite all of the rooms modals to measure and sound good. While placing a sub between the mains may assist in better integrations with the mains, it will likely cause the frequency response of the sub to be uneven.

While it completly contradicts some reading I've done, this sounds like more great info from Mr. Nousaine...would you have any links to a discussion or anything? I'd be curious to read.

I'd like to know why exciting all the room modes is critical, and why it's considered more important than integrating with the mains, in particular. Is this just a taste preference, or is there something too it.

And is corner placement always preferable in every room no matter the size/shape?

[3db]

While it completly contradicts some reading I've done, this sounds like more great info from Mr. Nousaine...would you have any links to a discussion or anything? I'd be curious to read.

I'd like to know why exciting all the room modes is critical, and why it's considered more important than integrating with the mains, in particular. Is this just a taste preference, or is there something too it.

And is corner placement always preferable in every room no matter the size/shape?

Although my sub is located in a corner, its at the opposite end of the room to where my mains are located. That postion was found by putting the sub where my seating psotion was and crawlign around like an angry dog until I found the spot where the bass seemed the loudest. This room is 12'x16' with a 7ft drop ceiling, and burber carpet.

Now in my other house, the best bass response I achieved was smack dam in the middle of the short wall againsgt the wall. My speakers flanked the sub on either side. This room (family room) was open to the kitchen however. I can't help but think that room shape and size plays a huge roll into where the sub should go.

[Sir Terrence the Terrible]

While it completly contradicts some reading I've done, this sounds like more great info from Mr. Nousaine...would you have any links to a discussion or anything? I'd be curious to read.

Tom Nousiane papers are VERY difficult to find on the internet. Most of them are articles in audio magazine, or sound and vision back in the 90's. However as a memeber of AES, I am able to aquire quite a few of his papers through it, and CEDIA and THX use his work on subs to a great degree.

I'd like to know why exciting all the room modes is critical, and why it's considered more important than integrating with the mains, in particular. Is this just a taste preference, or is there something too it.

And is corner placement always preferable in every room no matter the size/shape?

Most experiments with room acoustics and standing waves have been on rectangular rooms only. I think the reason why it is important to locate subs in corners has more to do with maximum volume, low frequency extension, and most even measurements. Also consider that it is easier to cut a room mode(which corners stimulate all boundary related modes evenly) than it is to fill in a node which cannot be done without extreme penalties on amplifier headroom and overall output

[Pat D]

While it completly contradicts some reading I've done, this sounds like more great info from Mr. Nousaine...would you have any links to a discussion or anything? I'd be curious to read.

I'd like to know why exciting all the room modes is critical, and why it's considered more important than integrating with the mains, in particular. Is this just a taste preference, or is there something too it.

And is corner placement always preferable in every room no matter the size/shape?

Some years ago, Stereo Review published an article on subwoofer placement by Mr. Nousaine. Unlike so many critics, he actually did the measurements and his work is widely accepted by the likes of Dr. Hsu, Tom Vodhanel, and others. Unfortunately I am not at home. If you want the reference, ask me next year.

Corner placement works best in most rectangular rooms giving the flattest and deepest response. Also, since the horn loads the sub, it requires less gain and can provide greater output levels.

There is a more general method. Place the sub in your listening position, preferably at your sitting level, and play some bass heavy music. Now, crawl around on your hands and knees to find those points in the room where the bass is loudest (probably close to the corners!). Next, place the sub in one of those places. Alan Lofft, who now answers questions on the Axiom site, describes this method in an article there. I'd link it except this silly computer I'm using makes it difficult to use multiple browsers.

[Sir Terrence the Terrible]

Some years ago, Stereo Review published an article on subwoofer placement by Mr. Nousaine. Unlike so many critics, he actually did the measurements and his work is widely accepted by the likes of Dr. Hsu, Tom Vodhanel, and others. Unfortunately I am not at home. If you want the reference, ask me next year.

Corner placement works best in most rectangular rooms giving the flattest and deepest response. Also, since the horn loads the sub, it requires less gain and can provide greater output levels.

There is a more general method. Place the sub in your listening position, preferably at your sitting level, and play some bass heavy music. Now, crawl around on your hands and knees to find those points in the room where the bass is loudest (probably close to the corners!). Next, place the sub in one of those places. Alan Lofft, who now answers questions on the Axiom site, describes this method in an article there. I'd link it except this silly computer I'm using makes it difficult to use multiple browsers.

I have that issue. He actually measure a sub in a L shaped room, and room with a loft, a regular rectangular room, a box shaped room, and a room with walls that jut in and out into the room. He stated that no sub should be located closer than 5ft to an opening. Corner loading provides 18db of boundary reinforcement at low frequencies.

[E-Stat]

Tom Nousaine has measured many subwoofers in many positions including multiple subs(2,3,4,5 close to mains) and according to his measurements a single sub in a corner still measures the best.

Perhaps with all the qualifications RG stated, that would be the case. I suspect the modest 12" powered subs I use in my HT system do not utilize such a steep slope. Even when I set the sub's crossover to 70 hz sourced from the LFE output, I find two blend better than one.

Returning to the original question, I believe than unless you have largely full range speakers to begin with, buy a serious sub with an unusually steep crossover slope, you would be better off with a pair.

BTW, TtT - I notice you use a pair of 15 inchers.

rw

[Sir Terrence the Terrible]

Perhaps with all the qualifications RG stated, that would be the case. I suspect the modest 12" powered subs I use in my HT system do not utilize such a steep slope. Even when I set the sub's crossover to 70 hz sourced from the LFE output, I find two blend better than one.

If you have read the writings of both Richard Greene(who comes here sometimes now) and Tom, according to both of them the ideal crossover point for subwoofer invisibility would be around 60-80hz with a VERY steep 24dbpo crossover. This is the parimeter that Tom Nousiane followed during his measurement of those many rooms.

Returning to the original question, I believe than unless you have largely full range speakers to begin with, buy a serious sub with an unusually steep crossover slope, you would be better off with a pair.

BTW, TtT - I notice you use a pair of 15 inchers.

rw

If you place full range speakers where the bass response is augmented(closer to the walls) then imaging suffers because of the added and early arrival of nearfield reflections. If you place full range speakers to acheive maximum imaging, it is likely to roll off early, and create peaks and valley in its freqeuncy responses do to late arriving reflections combining with early arriving reflections. That is why subs are so important no matter which kind of speaker you use.

You are right, I do use a pair of 15". Not for any reason other than to fullfill my audio requirements that the LFE speakers have 6db headroom over the loudest peak within that channel. A single of my subs could easily reach the loudest potential of the LFE channel(115db peak acousticall). Two subs located in each of the front corners on the floor reaches my goal of 6db. I otherwise would have used a single sub in my room if I didn't have these requirements. I require that all speakers in my system be able to handle at least 6db of headroom over the highest peak in that channel. Consequently I use VERY big speakers all of the way around, although I wouldn't consider my surrounds full range as they only go down to 50hz. Considering that there is not always alot of deep bass in the surrounds, that is low enough IMO to run full range. Only in the rarest of occasions have I seen bass at very high levels below 50hz in the surrounds. In the dubbing stage the surrounds are band limited at 80hz anyway, except if its being mixed at Skywalker sound which have surrounds that go down to 50hz or so.

[E-Stat]

... the ideal crossover point for subwoofer invisibility would be around 60-80hz with a VERY steep 24dbpo crossover. This is the parimeter that Tom Nousiane followed during his measurement of those many rooms.

I think we're on the same page. Unfortunately, I would venture to say most reasonably priced subs intended for HT use do not have that steep a slope.

You are right, I do use a pair of 15". Not for any reason other than to fullfill my audio requirements that the LFE speakers have 6db headroom over the loudest peak within that channel.

That's also why Harry Pearson uses five in his Magneplanar based HT system! The waves crashing in the movie Blue Crush were quite convincing.

rw

[gonefishin]

Tom Nousaine has measured many subwoofers in many positions including multiple subs(2,3,4,5 close to mains) and according to his measurements a single sub in a corner still measures the best. A subwoofer sitting between two main speakers is not likely to excite any of the rooms modes efficiently which will cause some some suckouts in the frequency response at the listening position. According to his testing, a subwoofer SHOULD excite all of the rooms modals to measure and sound good. While placing a sub between the mains may assist in better integrations with the mains, it will likely cause the frequency response of the sub to be uneven.

I wish I knew where the articles I had read were. I can't remember the specifics...but I thought that in one test (regarding placement of single and double subs of different types) he had concluded that there was better response not only just in the corner...but also concluded that two perform better near a corner than near each main speaker. Again...I'm going from memory...but I thought that was what he had said. I'll see if I could find it.

dan

[Sir Terrence the Terrible]

I wish I knew where the articles I had read were. I can't remember the specifics...but I thought that in one test (regarding placement of single and double subs of different types) he had concluded that there was better response not only just in the corner...but also concluded that two perform better near a corner than near each main speaker. Again...I'm going from memory...but I thought that was what he had said. I'll see if I could find it.

dan

This is true, and I cannot disagree with this. This follows along with a single sub in a corner. I believe he found that two subs stacked in the same corner provided 6db more output, and a smoother overall response from the combination than what you get my locating subs at each of the 5 speakers.. However if even bass coverage(at more than one seat) is what you desire, two spaced subs in opposite corners do this best.

[gonefishin]

This is true, and I cannot disagree with this. This follows along with a single sub in a corner. I believe he found that two subs stacked in the same corner provided 6db more output, and a smoother overall response from the combination than what you get my locating subs at each of the 5 speakers.. However if even bass coverage(at more than one seat) is what you desire, two spaced subs in opposite corners do this best.

Like I said...I was just trying to recall from memory what the article had said. Many of us...don't have the luxury of placement all the time...or we are limited in how flexible we can be with placement. But it's still nice to read what we may want to achieve in a similar shaped or sized room.

Pat (or others) if you've got any links...I'd like to read them...whenever you find them is fine...even if it's next year

I decided i will swim with the stream of fish since that is the only way to get accepted. I'll stick with my non-box anywhere in the systems policy

Oh...I would hardly say that I'm accepted.

I'm sorry for the rude comment I made (stats are fast comment)...I did know what you were trying to say. You would do very well by sticking exactly with what you have...but you know that

dan

[Florian]

Oh...I would hardly say that I'm accepted.

I'm sorry for the rude comment I made (stats are fast comment)...I did know what you were trying to say. You would do very well by sticking exactly with what you have...but you know that

dan

Thats ok Dan, i didn't take it in a bad way. I am not able to express myself exactly as i want to in writing, i mostly come across quite cold and with a huge EGO. My friends tell me that i am a different person when writing as oposed in real life. Personally i have never heard any subwoofer that could blend in with a panel perfectly and like SirT said the 30Hz wavelenght is longer then most rooms anyways but there are chairs, couches, furniture etc..that help you notice the subs direction. So the question is what we want to discuss, do we discuss the subwoofers localisation in a normal living surroundings or on a wide open field with emptyness. And to the Quad lover, most Quad people buy them for the reproduction of voices and string instruments just like with the Martin Logan CLS series. They do the midrange absolutly wonderfull, also the 988 and 989 are a bit better in this regard. Playing a pipe organ on a Quad is pretty out of place and will not show off their best side, thats just a fact. You will never get a perfect integration with a subwoofer across the board, you can go with a linesource subwoofer, one in each corner and and go fully active on the subwoofer and speakers with digital room correction where you can also adjust the phase and time delay issues that will come up.

-Flo

[kexodusc]

Personally i have never heard any subwoofer that could blend in with a panel perfectly and like SirT said the 30Hz wavelenght is longer then most rooms anyways but there are chairs, couches, furniture etc..that help you notice the subs direction. So the question is what we want to discuss, do we discuss the subwoofers localisation in a normal living surroundings or on a wide open field with emptyness.

-Flo

Hey Flo...

This caught my eye a bit,not sure I understand what you're getting at. I haven't known couches, chairs, etc to produce such an effect that a subwoofer could be localized because of the furniture interactions in a room. If anything those interactions frequencies have with furniture would do just the opposite, randomize reflections and make it even harder to localize a sub, wouldn't it?

As for panels and subs, well, I think this all comes down to proper integration. While panels do have a sweet sounding "speed" to them, there are plenty of traditional woofers with measured transient responses that are on par and even better. I think there's just a lot more budget/entry-level woofers and tweeters that people hear, and not many panel speakers at the same price points.

Some subwoofers have pretty good transient response. However, that said, low frequencies aren't very transient to begin with and a lot of the "speed" disadvantages you hear with subs has more to do with human perception and physics than the subs being "slow". Without a lot of technobabble, you can hit a barrier for speed in low frequencies much earlier than you hit it in the midrange. This happens regardless of how speakers are produced. It then becomes more of a question of how slow can you tolerate the subwoofer being. Lots of high output subs have terrible transients.

A friend of mine in the local DIY group here finished a large Bohlender Graebener/Aurum Cantus design (the AC's did just the highest frequencies in his design), and built in a pair of 15" woofers into a sealed box design. The subs had a relatively low xmax compared to most of the woofers you see these days. The low excursion and sealed cabinet resistive pressure made for a very fast attack and decay that had no problem keeping up. These speakers are tall and ugly looking, but damn they sounded nice. Total project cost him about $2400 or so.

[Florian]

Interesting. Well a sealed design is very preferable when matching it with a panel. Maybe its not only speed but the simple lack of a box and the different sound characteristic that sets almost all of us panel users in a position where we cannot tollerate a subwoofer in our systems. Panel bass is different from box bass, eventough they measure exactly the same. If you look at such high design like the Alon Grand Exotica or the IRS-V and chat with their owners (my friend owns a Alon Grand Exotica) they will telll you that even with digital room correction etc.. they cannot get that last nth of a percent of integration. Like i said in my above post, it was a close call but if you really tried you can hear the subwoofer. What i mean by the furniture is that the subwoofer will make the local surroundng resonate and they introduce noise. If you place a subwoofer near a cabinet then the cabinet will introduce its own noise which is audible and could be mistaken for the subwoofer. I agree that if done 1000% right with the matching time delay, slopes and positioning a subwoofer can be a nice addition if your speaker cannot reproduce a fullrange signal. For me its not only a integration issue its also a issue about character and the way music is reproduced. My speaker for instance moves air with a over 6ft tall area. It loads the room equally and the bass is very different that from any box, unless you go all the way and build a 6ft tall subwoofer that will load the room equally. But then you have to make sure you cross it low enough and correct the unequal room loading effect. Since most rooms are not perfectly symetrical the sound will be reinforced differently and the sides will not match which will make the subwoofer stand out from the system sonically. If done right, and in my case i think it would look something like this. A subwoofer, 6 feet tall in a dipole configuration driven actively with room correction to reduce the different loading effects of the room and the time delay that occurs between the main panels and the subwoofer. Combined with another subwoofer at the oposite side of the room run out of phase would give me the most evenly loaded room with matched timings and a even responce that is soncially very hard to locate. When a bass drum hits in my room the entire air vibrates over the entire height of the room, if i add a conventinal subwoofer to it, it will stand out because it loads the room differently. I agree with you, that if done right and taken the correct aproach they can be a nice addition. But they have to match the sonic characteristics and match the room loading actions of the main towers plus have to be matched by a digital room correction device since the room loads them differently.

Cheers

Flo

[theaudiohobby]

And to the Quad lover, most Quad people buy them for the reproduction of voices and string instruments just like with the Martin Logan CLS series. They do the midrange absolutly wonderfull, also the 988 and 989 are a bit better in this regard. Playing a pipe organ on a Quad is pretty out of place and will not show off their best side, thats just a fact. You will never get a perfect integration with a subwoofer across the board, you can go with a linesource subwoofer, one in each corner and and go fully active on the subwoofer and speakers with digital room correction where you can also adjust the phase and time delay issues that will come up.

-Flo

To Florian the Apogee lover,

You need to recheck your facts , Why? Cos they are wrong , I have already successfully interested a single 'cone' subwoofer with my Quad ESL 57 without need for digital room correction etc, What is required is a bit informed knowledge about room interaction, crossover slopes etc. And every now and then, I touch the subwoofer cone or put my ear to it to confirm that it is still operational, why, because it is sonically invisible. The subwoofer is lowpassed at 63Hz, the ESL is highpassed at the same frequency, the ESLs are also raised about 17'' from the floor to minimize floor reflections, The subwoofer is placed a couple of inches away from the right speaker. I play a lot of acoustic music, primarily jazz and orchestral music and I do not experience any of the issues that you mentioned, neither have any of the more knowledgeable sources made such observations, so I can safely conclude that your comment on subwoofer integration with planar speakers are erroneous.

Also, I hope your comments about Pipe Organs, Martin Logans, the 988 and 989 etc are simply just your opinion. Cos after some extensive listening I prefer the Quad ESL to the 988, IIRC a fellow over at AA specifically mentioned that he went from the ESL 57 to the 988 to the 989 and back to ESL 57, so it is all about preferences and for my musical preferences, the ESL 57 works much better for me.

[Florian]

Well i dont need a subwoofer

But i disagree, we are not talking about facts. Your small ESL is very different from my planar and trust me i can hear it out. If you like it, thats cool.