Ideas for a dynamic speaker that isn't affected much by room acoustics

[fjhuerta]

The ZDT3.5 taught me a lesson... at first I thought it was aggressive sounding at high levels, since my Neo8 / Neo3 design sounded better at any listening level.

Here's the room they were in.



Not as much a room as a huge, open space with hardwood everywhere.

Then, I decided to move the ZDT to a room with some carpet, lots of furniture, etc. The speakers sounded a lot better.

I took out the Liberty RTA to see I wasn't imagining things. Here's what I found (sadly, I didn't save the screens).

• The smaller room had a bigger bass boost
• The smaller room had a nice drop-off starting at 1 KHz
• The bigger room had a nasty peak at 2 ~ 4 KHz.
• The bigger room also had a dip from 250~600 Hz
• When measuring the speaker at 1 meter using Liberty, FR was basically flat.

So, I guess the problem in the bigger room is an excess of midrange energy, plus not enough bass reinforcement.

I assume the Neo8 / Neo3 design doesn't have this problem (it measures really well using Liberty) because of their limited vertical dispersion.

There's no way my wife will let me buy a carpet for that place. She loves the floor.

So, what kind of design would you attempt that would minimise floor reflections and the overall contribution of the room to the sound? The Neo8 / Neo3 design did it pretty well - I suppose a combination of big woofers and drivers with limited vertical dispersion would do the trick.

I'm thinking about a design with a pair of woofers (8"), vented, with an MTM array using the TB Titanium. I suppose that would limit vertical dispersion. I don't know whether to go with an open back baffle for the mids, or doing a sealed box. The tweeter would be a Seas 27 TAFN.

Do you think this would help?

[ThomasW]

Ideas for a dynamic speaker that isn't affected much by room acoustics

Ideas for speakers that defy the laws of physics....

AFAIK, the only way around this is to buy one of those very $pendy digital processing units that map the room and EQ it.

I heard the one below at the 2008 RMAF. What it could do was impressive, but it lowered the ultimate SQ/sound staging to obtain flatter in-room response..

http://www.lyngdorf.com/index.php?option=com_content&task=view&id=66&Itemid=35

[fjhuerta]

Ideas for speakers that defy the laws of physics....

AFAIK, the only way around this is to buy one of those very $pendy digital processing units that map the room and EQ it.

I heard the one below at the 2008 RMAF. What it could do was impressive, but it lowered the ultimate SQ/sound staging to obtain flatter in-room response..

http://www.lyngdorf.com/index.php?op...d=66&Itemid=35

The other alternative is changing my wife, but I'm not willing to do that! :B

[dlneubec]

Probably a line array would be something to consider. They are said to limit vertical dispersion to a great degree, while maintaining normal horizontal dispersion. Theoretically, you're supposed to get a wall of sound the hieght of the speaker, at least within the nearfield. I don't kjnow much about them, but I was just talking with Jim Griffin about them at the Lexington DIY this past weekend. He does know what he is talking about in regard to line arrays.

The other benefit is that using multiple drivers can significantly reduce distortion within a given spl level. Of course, they have their own inherent problems, I'm certain.

[dlneubec]

Another posibility is to try and design a speaker that uses room boundary reinforcments as part of the design, rather than fighting them. I've got something like this in mind for a future design.

If interested, I suggest you review the articles by Roy Allison on "The Influence of Room Boundaries on Loudspeaker Power Output" from the 70's. Allison had some very popular and well thought of speakers based on this concept back in the 70's and 80's. Here is a link to where you can download the article above:

Roy Allison Article

Also, later Roy was involved with RDL Acoustics. At the link below, toward the bottom of the page, there is a link to download a software called BestPlace.exe that simulates the boundary gain accordin to driver placement in regards to the front and sidewalls and floor. It is based on Roy Allisons theories.

BestPlace

Look for Bestplace Speaker Placement program by RDL inc.

[kevinp.]

large pro woofers (think 15", the bigger the better for directionality) and horn/waveguide tweeter? Hmm... sounds like a Geddes speaker

[Jonasz]

Dipoles! Should work like a charm in that room...

Look at these for example: http://home.wanadoo.nl/dezaire/OB3W/OB3W_nl.htm

[JonP]

You might give some thought to "artful" wall hanging absorbers... There are many web articles out there (think there was a recent thread on this here) basically making a shallow frame filled with a layer of fiberglass or rockwool board, covered with cloth. Some have been able to find cloth with an interesting picture or pattern, then its "Art"!

Something like that, or even wall hangings, will go a ways in cutting down the reflections in the room...

[jkrutke]

Indeed, I think more control over your vertical polar response would help your situation with the hardwood floor, and you're on the right track. It probably comes as no surprise that most of my designs have a tonal balance that works better in carpeted rooms - because that's what I design for and listen in myself.

There's something to be said for a larger MMTMM 2.5 way in a situation like that, using 5" or 7" woofers. I toyed with that concept myself and built one using smaller woofers, but it was too close to a point source to make a difference. But with larger woofers and/or greater spacing, you get a wider frequency range to control, particularly if you go a little higher and shallower with the tweeter crossover point than you normally would in an MTM. I have a larger MMTMM simmed which I could post some polar plots if you want. I haven't built it yet, mostly because I didn't like a 50" tall speaker. I may still give it a try someday though, possibly based on my waveguide TMM design.

[cjd]

Well, you lose the dynamics perhaps, but those little Bose cubes don't care about room acoustics... they sound equally terrible in almost all situations. (and in fairness, if they're absolutely superbly perfectly set up they can almost sound good, so even this stupid little dig isn't quite right...)

[DeathMonk]

(and in fairness, if they're absolutely superbly perfectly set up they can almost sound good, so even this stupid little dig isn't quite right...)

BLASPHEMY!

[Russ_L]

DIY Events

Hi all- slight diversion. I recently got the DIY speaker bug and would love to attend some DIY events. I noticed above that Dan N. mentioned the Lexington DIY. Is there a link to upcoming events? I live on Long Island but I can travel. Thanks.

Russ

PS- The Mission Impossible DIY site is incredible; love it.

[---k---]

I haven't built it yet, mostly because I didn't like a 50" tall speaker.

Wuss!

Hopefully next month, my speakers will be traveling from my carpeted room with 2 large sofas and chairs to a room with hardwood and less furniture. It will be interesting to see how they react.

[jaron]

Simple suggestion

All the suggestions (line array, dipole, large woofer and horn) for minimizing off axis energy should help. Here's an easy one (it's cheap, too):

Move the speakers closer to you. The direct radiation becomes relatively louder than the reflections.

[kevinp.]

All the suggestions (line array, dipole, large woofer and horn) for minimizing off axis energy should help. Here's an easy one (it's cheap, too):

Move the speakers closer to you. The direct radiation becomes relatively louder than the reflections.

Hey thats an easy one. Instead of just closer, how about right against your ears? Maybe build some kind of strap to go hold them over your head.... :

[Jim Griffin]

I'll try to expand the line array idea as a speaker to minimize off axis energy so that room effects are minimal. We know that within their near field line arrays radiate in a cylinder of sound (along their height) that extends outward parallel to the floor and ceiling. In other words very little sound impringes onto the floor and ceiling. Hence, floor and ceiling reflections are minimal. You can read my line array white paper to get more info on that subject.

A few years ago McIntosh introduced line arrays that feature two rows of midwoofers symmetrically arrayed on each side of the central tweeter line. Hence, you have what amounts to a horizontal stack of elemental MTM's. A MTM is known to a symmetrical lobe pattern with directional nulls off axis to the right and left of the on-axis radiation. (In the normal vertically standing MTM the nulls are above and below the on axis position.) Thus, in the McIntosh line array speaker those nulls are directed toward the sidewalls of the room so that by proper horizontal spacing of the drivers, one can minimize the sound that reflects from the sidewalls. The spacing of the drivers will determine the off axis angle of the nulls. Hence, the designer has a way to reduce the energy that strikes the sidewalls in addition to the advantages of minimal floor and ceiling radiation.

Robert E. Greene reviewed the McIntosh XRT-28 speaker in his review in The Absolute Sound in Feb.-Mar. 2005 magazine. There is a link to his review on the McIntosh site See:

XRT28-AbsolouteSound.pdf

A little later he did additional measurements with the XRT28 and noted how this speaker had clean impulse responses which tended to minimize the impact of the listening room. Those measurements are referenced on REG's site at:

https://web.archive.org/web/20171003012734/http://www.regonaudio.com/McIntosh%20Supplement.html

REG states: "The listening room is essentially out of there for generating any kind of reflection sonic signature."

My friend Rick Craig of Selah Audio has also used the symmetrical line array design with small midwoofers and a line of high quality ribbons. His array is pictured at:



In theory another way to achieve similar results is to use a dipolar (or open baffle) near field line array which would have minimal energy directed toward the side walls.

Bottom line is that a symmetrical line array or a dipolar line array you can provide a virtual room free listening experience without DSP EQ or room treatments. Sounds like a nice thing to have.

Jim

[Paul Ebert]

It seems to me that what Jim is recommending is probably the best you can do. But, if you need something more practical (or cheaper, or with, possibly, more WAF), you might consider some of the design aspects of the Gradient Helsinki. In particular, the waveguided tweeter, cardioid midrange angled up, and angled dipole bass. That said, it seems to me that you don't have much free space for the speaker in the reflective room, given the placement of the speakers with respect to the furniture. I suspect that these design aspects may only be effective with more free space around them.

The angled cardioid midrange might be something to consider in this application. Someday, I'd really like to experiment with a Helsinki clone.

http://www.gradient.fi/helsinki15/

[fjhuerta]

Thank you all for your answers! John, it's good to know my ideas aren't too far off what I'm looking for.

Jim, your ideas are very interesting - but a bit expensive, especially now that our currency has lost approximately 40% of its value compared to the dollar. :s I'll definitely see what I can do, in a smaller scale. This time I'll take a couple of months before I start building something; I'm a bit tired from the last two projects, so I'll just enjoy what I've built for now.

Paul I think I could fit a speaker like that. That speaker looks incredible!

Thanks all for your help. I truly appreciate it.

[cotdt]

You need carpet, and some wall and ceiling dampening. Me, I listen nearfield in a heavily dampened medium-sized room so I can confirm that everything sounds wonderful. Actually the room is a benefit as it adds low-end gain. When I listened to the speakers outdoors they actually sounded worse.

[Paul Ebert]

Paul I think I could fit a speaker like that. That speaker looks incredible!

Yeah, that's what I think, too. The wife thinks the Avalon style speaker looks better, so that's what we'll have (for now). In fact, she thinks the Helsinki looks weird.

[augerpro]

I listened to that Helsinki at RMAF. Nothing special. As you would expect there is no bass/midbass/lower midrange sitting in front of the speaker. As you move around to the side it begins to pick up. Pretty questionable design choice. If there was supposed to be some good sonic reason for this I sure didn't notice. Oh yeah, those woofers were moving a lot for the nearly non existent bass.

[AJINFLA]

I'll try to expand the line array idea as a speaker to minimize off axis energy so that room effects are minimal. We know that within their near field line arrays radiate in a cylinder of sound (along their height) that extends outward parallel to the floor and ceiling. In other words very little sound impringes onto the floor and ceiling. Hence, floor and ceiling reflections are minimal. You can read my line array white paper to get more info on that subject.

A few years ago McIntosh introduced line arrays that feature two rows of midwoofers symmetrically arrayed on each side of the central tweeter line. Hence, you have what amounts to a horizontal stack of elemental MTM's. A MTM is known to a symmetrical lobe pattern with directional nulls off axis to the right and left of the on-axis radiation. (In the normal vertically standing MTM the nulls are above and below the on axis position.) Thus, in the McIntosh line array speaker those nulls are directed toward the sidewalls of the room so that by proper horizontal spacing of the drivers, one can minimize the sound that reflects from the sidewalls. The spacing of the drivers will determine the off axis angle of the nulls. Hence, the designer has a way to reduce the energy that strikes the sidewalls in addition to the advantages of minimal floor and ceiling radiation.

Robert E. Greene reviewed the McIntosh XRT-28 speaker in his review in The Absolute Sound in Feb.-Mar. 2005 magazine. There is a link to his review on the McIntosh site See:

XRT28-AbsolouteSound.pdf

A little later he did additional measurements with the XRT28 and noted how this speaker had clean impulse responses which tended to minimize the impact of the listening room. Those measurements are referenced on REG's site at:

https://web.archive.org/web/20171003012734/http://www.regonaudio.com/McIntosh%20Supplement.html

REG states: "The listening room is essentially out of there for generating any kind of reflection sonic signature."

My friend Rick Craig of Selah Audio has also used the symmetrical line array design with small midwoofers and a line of high quality ribbons. His array is pictured at:



In theory another way to achieve similar results is to use a dipolar (or open baffle) near field line array which would have minimal energy directed toward the side walls.

Bottom line is that a symmetrical line array or a dipolar line array you can provide a virtual room free listening experience without DSP EQ or room treatments. Sounds like a nice thing to have.

Jim

Hi Jim,

It was a pleasure meeting and speaking with you at Lex. I would be remiss not to point out that if you are going to reference REG and speakers that interact well with real rooms, you might want to look at this as well Revolution. A speaker that fits my design philosophy a bit closer :W (not to mention the speaker that I like to remind Earl, at least equalled his Summa...in his own living room : ).
I have yet to hear a line that I like (this includes practically all the McIntosh models over the years via the local dealer). John (auplater) did not do them much of a favor either with his music selection and what he said turned out to be a faulty set up. The primary suspect in my mind might have much more to do with time domain than frequency. What the line might provide is the 20+ db headroom than Earl claims he has...and is lacking in the Gradient. Of course there is a solution to that, as you heard an inkling of in Ky. :W

cheers,

AJ

[Jim Griffin]

AJ,

Robert E. Greene does write about the Gradient and and dipolar speakers in general in some of his articles on the www.regonaudio.com site. He also has several articles on room acoustics and digital processing to EQ speakers within the listening environment. Others will find a lot of good reading that address these subjects.

Yeah, the McIntosh line arrays suffer from their use of less than top notch midranges and tweeters in the models that I have heard. Many commercial line arrays (and most DIY versions as well) often are less than well implemented so their sound quality suffers.

As you know dipolar speakers do have the potential to minimize room/speaker interaction because of sidewall reflection. How dipoles interact with the rest of the room is of importance as well.

Your loudspeaker design that we heard in Lexington is exceptional in how you use a cardiodal woofer arrangement which minimizes any in-room front wall reflections. The open baffle coaxial mid provides the signature dipolar sound. Your speakers were dynamic and clean sounding. Having heard Earl's Summas I'll agree that your speakers are superior.

Jim

[Jonasz]

AJ: What kind of speakers are you using nowadays?

[CraigJ]

You mean these?

[Paul Ebert]

Which coaxials are you using?

[AJINFLA]

AJ,
Yeah, the McIntosh line arrays suffer from their use of less than top notch midranges and tweeters in the models that I have heard. Many commercial line arrays (and most DIY versions as well) often are less than well implemented so their sound quality suffers.
As you know dipolar speakers do have the potential to minimize room/speaker interaction because of sidewall reflection. How dipoles interact with the rest of the room is of importance as well.

No question that the line format has quite a lot of potential benefits, including control of directivity in the vertical plane as well as dynamic headroom/sensitivity from the multiple motors. Perhaps I should clarify here and say that I have heard exceptional sounding lines, but the one achilles heal that I cannot ignore (due to my range of music listening) is imaging on solo instruments, which I find not so real. Large orchestral works are splendid due to the oversized image (distortions making things sound more realistic...next thing you know I using tubes and such :W ).

Your loudspeaker design that we heard in Lexington is exceptional in how you use a cardiodal woofer arrangement which minimizes any in-room front wall reflections. The open baffle coaxial mid provides the signature dipolar sound. Your speakers were dynamic and clean sounding. Having heard Earl's Summas I'll agree that your speakers are superior.

Jim

You'll get me in trouble if you don't throw in the IMHO part . I'll withhold any such judgement until I hear them side by side in the octagon...or Earl's untreated room .
Although no more forays north until things warm back up a bit. Maybe March or April, we'll see how the weather is in Michigan.

cheers,

AJ

[AJINFLA]

AJ: What kind of speakers are you using nowadays?

The fullrange Sony's that came with my brothers HTIB

Which coaxials are you using?

I'm keeping it a secret. I don't want priori knowledge to further skew the sighted listening. Or maybe I do (remember, audiophiles are going to be hearing these things too ).
So intentional vagueness and possible disinformation could also be at play. Did I mention I'm using ClarityCap MRs in the XO and Cardas internal wiring?

cheers,

AJ

[fjhuerta]

Zaph published the info on his MTM at his blog... Thanks Zaph!

His project looks tempting and not extremely expensive, considering the drivers he's suggesting - smooth sounding and apparently there's no need for extremely complex x-over work. The woofers are well priced, at $20 a piece.

At 50" tall, they are not for everyone, though.

[fjhuerta]

By the way,

I listen to the pseudo ZDT's every day of the week, and I'm surprised at how much I've been enjoying them. The piercing midrange I used to listen to when these drivers were in an MTM is completely gone.

An interesting observation is that the midrange level may even be subjectively louder at my listening position - probably due to the better dispersion of the RS-52. But it's never bothersome. The ZDT's are, IMHO, far easier to listen to than any RS180-based MTM I ever built.

[jkrutke]

Zaph published the info on his MTM at his blog... Thanks Zaph!

His project looks tempting and not extremely expensive, considering the drivers he's suggesting - smooth sounding and apparently there's no need for extremely complex x-over work. The woofers are well priced, at $20 a piece.

At 50" tall, they are not for everyone, though.

I'm trying to find a way to fit those into my schedule. Maybe over the christmas holiday I can sneak into the garage for a while.

Another thing about the Peerless 830656 SDS woofers - If I'm going to be cutting 8 woofer holes, surface mount in some rough cut holes sure beats the hell out of countersinking.

[fjhuerta]

Yeah, I noticed that - no countersinking!

I thought about two options - trying to do something similar with Dayton RS150s woofers (since I already have four). But a 2nd order crossover to the tweeter is out of the question.

The other one is buying the 8 Peerless drivers, and using a pair of 27TBFC/G tweeters I already have.

Slight problem - our currency has lost around 38% of its value in the last month compared to the dollar, so things suddenly got very expensive around here...

[dwk]

Returning to the 'horn' idea, I can attest to their ability to play extremely well in small rooms when set up properly. It's probably not a particularly practical setup for multi-use rooms, though.

I have the Yorkville U15's, which are 60x60 conical horns topping a 15" pro midbass/woofer. I have the U15's placed directly in the corners of a very narrow (slightly under 8') room, using the Geddes setup where the main axes cross somewhat in front of the listener. This arrangement works with the U15's due to two reasons
a) very narrow pattern control keeps sidewall reflections down (even the Summa at 90x90 probably wouldn't work too well in this setup)
b) no baffle step compensation built in, so they don't boom due to corner loading

The two keys to this I think are removing most of the early boundary reflections which are unavoidable in any setup where the speakers are 'out in the room', and having a setup where the radiation pattern gently broadens from 60x60 to 90x90, providing pretty nice overall power response without any other manipulations.

I still need a bit of treatment on the sidewalls and between the speakers (probably wouldn't need the sidewall treatment if the room were 2-4' wider). The results IMHO are great. I've certainly heard better systems, but I don't remember having heard a better system in this type of room.

[DS-21]

Perhaps I should clarify here and say that I have heard exceptional sounding lines, but the one achilles heal that I cannot ignore (due to my range of music listening) is imaging on solo instruments, which I find not so real. Large orchestral works are splendid due to the oversized image (distortions making things sound more realistic...next thing you know I using tubes and such :W ).

It's not just you, though the height thing bothers me on orchestral stuff, too. All of the lines I've heard have done that, including the ur-Linus at Gordon & Rob's DIY ATL gathering what was now a bunch of years ago. It was most striking when going from the Linus to a set of Tannoy D500's (8" Dual, 8" woofer) that Gordon brought as a control.

Now, I have no doubt designs have improved since then, and certainly many DIY lines are using better parts than those original Linuses did. But other line-sources (including big Sound Labs and Maggies) do that, too.

[cotdt]

Instead of line source, which never sounded any good to me, try a wall source.

[peter_m]

By the way,

I listen to the pseudo ZDT's every day of the week, and I'm surprised at how much I've been enjoying them. The piercing midrange I used to listen to when these drivers were in an MTM is completely gone.

An interesting observation is that the midrange level may even be subjectively louder at my listening position - probably due to the better dispersion of the RS-52. But it's never bothersome. The ZDT's are, IMHO, far easier to listen to than any RS180-based MTM I ever built.

Does this include the Modula MT or MTM?

What do you mean by "pseudo ZDT"?

Cheers,
Peter

[fjhuerta]

Nope, I never tried the Modulas. I tried the Natalies, then I went for a 6th order acoustical at 1.8, 1.5 KHz, then a 4th order acoustical with a notch filter at 1.6, 1.4 KHz. I must have tried at least 10 variations in total.

It's a "pseudo" ZDT because the tweeter is a Vifa D25Q, not the Dayton Neo.