Live-End Dead-End in a Small Room?

[boom3]

Hi,

My restored study is 11 x 14, and before the storm I had Dahlquist DQ-10s in there. They were very good in the study for close listening, but they are history now. I have thought about Klipsch products to replace them,  but I also have several drivers laying around that need to be put into service, so I will home-build a pair of speakers. My desk will only be 7 feet away from the speakers at best. The room has 8 foot ceilings.

 

My question is: In a room of this size and shape, is there any point trying to implement live-end dead-end (LEDE)? The floor is now tile (no more carpet for us!) and as you might expect, the room is very lively. Pre-storm, I rarely cranked it up beyond about 90 dB and usually listened in the 70-85 dB range.

Thanks for any ideas

 

 

[PrestonTom]

Interesting project, but you should tell us more. For starters, are these horn loaded speakers? Are there constraints on how large they can be?

[wvu80]

There are several interesting things going on in your post.

 

I had to look up LEDE.  That likes like a very specific procedure so I can't offer an intelligent comment on it, but in general room treatments are a good idea. Is your restored study a converted bedroom as mine is?  Having clothing or some other item, even a towel in the closet helps to break up reflections..

 

Re: your DIY speaker drivers, let me ask without being snippy, do you know what you're doing?  Have you made DIY speakers before?  Do you have knowledge and skill how to put together a proper enclosure or do you need a flat pack?  If you do, I'm jealous.  I am a flat pack kind of guy myself.

 

Do you know how to properly design and make crossovers?  That is a very high level skill IMO and again, if you can do that your knowledge and skills are above my ability to help.  Still, I'd like to hear what you have in mind.  Big speaker, little speaker?  What drivers do you have?

[Chris A]

There are three immutable requirements in my experience to achieve outstanding imaging and soundstage when you constrain the listening distance to 7 feet and the room size to something like 11x14x8 feet:

1. all drivers within 1/4 wavelength at their crossover frequency (implying time alignment to within 90 degrees of phase).
2. (very) controlled early reflections--such as having a "reflection-free zone" that achieves -15 to -20 dB first reflections from around the loudspeakers down to ~200 Hz or lower.  This can be achieved through a LEDE control room-type of design with lots of absorption in the front of the room and lots of diffusion one the remaining walls at the back of the room--probably effective down to below 500 Hz. It can also be achieved through using full-range controlled directivity loudspeakers that can be placed in the room corners.
3. having loudspeakers that exhibit very low phase distortion--less than 360 degrees of phase rotation throughout the audible band.

The easiest way to achieve all three conditions in my experience is to use full-range controlled directivity loudspeakers--such as multiple entry horns (MEHs) with fairly narrow coverage (~60 degrees horizontal, vertical), and absorption just around the mouth exit of the MEHs to control early midrange reflections.  You can look at Bill Waslo's spreadsheet-based approach to do the parts layout and cuts for a full-range-sized MEH.  You'll probably need a DSP crossover to make the crossover EQ problem tractable--but that really goes for any DIY loudspeaker having more than one way, IMO.

 

Dipole loudspeakers will all have backwave issues that will force you to move to a somewhat contorted position near the rear wall and the loudspeakers about 1/3 of the way from the front wall to the back wall, and positioned almost in the middle of the room in order to get reasonable imaging (and I wouldn't wish that kind situation on anyone). 

 

Your idea to use a LEDE approach is about the only way to use non-MEH (i.e., without full-range directivity) loudspeakers, but it will require covering almost all of the front and side walls with absorption and the remaining walls with diffusers (see page 495 of the book Recording Studio Design (3rd ed.) by Philip Newell). This is a lot of room treatment, but one that I've experienced as necessary in a listening room of the size that you mention.

 

Chris

[boom3]

On 7/7/2019 at 8:09 AM, wvu80 said:

There are several interesting things going on in your post.

 

I had to look up LEDE.  That likes like a very specific procedure so I can't offer an intelligent comment on it, but in general room treatments are a good idea. Is your restored study a converted bedroom as mine is?  Having clothing or some other item, even a towel in the closet helps to break up reflections..

 

Re: your DIY speaker drivers, let me ask without being snippy, do you know what you're doing?  Have you made DIY speakers before?  Do you have knowledge and skill how to put together a proper enclosure or do you need a flat pack?  If you do, I'm jealous.  I am a flat pack kind of guy myself.

 

Do you know how to properly design and make crossovers?  That is a very high level skill IMO and again, if you can do that your knowledge and skills are above my ability to help.  Still, I'd like to hear what you have in mind.  Big speaker, little speaker?  What drivers do you have?

Yes to all questions

I have pair of Great Heil AMTs and two Visaton 12 inch woofers, plus a couple of Phillips AD5060 series mids from the dear departed Dahlquists. Final config not decided. The Heils like sharp crossovers so if I go 2 way I will probably go with 4th order L-R, served me well before.

[boom3]

On 7/7/2019 at 10:24 AM, Chris A said:

There are three immutable requirements in my experience to achieve outstanding imaging and soundstage when you constrain the listening distance to 7 feet and the room size to something like 11x14x8 feet:

1. all drivers within 1/4 wavelength at their crossover frequency (implying time alignment to within 90 degrees of phase).
2. (very) controlled early reflections--such as having a "reflection-free zone" that achieves -15 to -20 dB first reflections from around the loudspeakers down to ~200 Hz or lower.  This can be achieved through a LEDE control room-type of design with lots of absorption in the front of the room and lots of diffusion one the remaining walls at the back of the room--probably effective down to below 500 Hz. It can also be achieved through using full-range controlled directivity loudspeakers that can be placed in the room corners.
3. having loudspeakers that exhibit very low phase distortion--less than 360 degrees of phase rotation throughout the audible band.

The easiest way to achieve all three conditions in my experience is to use full-range controlled directivity loudspeakers--such as multiple entry horns (MEHs) with fairly narrow coverage (~60 degrees horizontal, vertical), and absorption just around the mouth exit of the MEHs to control early midrange reflections.  You can look at Bill Waslo's spreadsheet-based approach to do the parts layout and cuts for a full-range-sized MEH.  You'll probably need a DSP crossover to make the crossover EQ problem tractable--but that really goes for any DIY loudspeaker having more than one way, IMO.

 

Dipole loudspeakers will all have backwave issues that will force you to move to a somewhat contorted position near the rear wall and the loudspeakers about 1/3 of the way from the front wall to the back wall, and positioned almost in the middle of the room in order to get reasonable imaging (and I wouldn't wish that kind situation on anyone). 

 

Your idea to use a LEDE approach is about the only way to use non-MEH (i.e., without full-range directivity) loudspeakers, but it will require covering almost all of the front and side walls with absorption and the remaining walls with diffusers (see page 495 of the book Recording Studio Design (3rd ed.) by Philip Newell). This is a lot of room treatment, but one that I've experienced as necessary in a listening room of the size that you mention.

 

Chris

Thanks Chris. The problem I have is that a lot of wall space its already spoken for for bookshelves. Bookshelves are mediocre absorbers and lousy diffusers. I have resolved not to have any more "dead storage" in my study but that may only be dream, it may only be possible to reduce the unused items and not eliminate them. The room is now tiled so it is very lively. 

 

Another pal suggested that in that room I might be happier with flat panels, he was suggesting Maggies.I have not heard any in years and with the drivers I have I would prefer not to spend a lot of money on store-bought speakers. My initial design has footprint of 17 x 19 inches (100 liter class bass box). That footprint is about the largest I can tolerate in free-standing speaker. I will look at the links you provided,thanks for all ideas!

 

[billybob]

Know about space constraint but little about advising on your endeavor other than, keep simple and of course minimalist, lol

Good fortune...

[boom3]

On 7/7/2019 at 7:01 AM, PrestonTom said:

Interesting project, but you should tell us more. For starters, are these horn loaded speakers? Are there constraints on how large they can be?

No, these area not horn loaded. The first draft has footprint of 17 x 19 inches (100 liter class bass box) and that is the largest free-standing size I can tolerate.

[wvu80]

1 hour ago, boom3 said:

Yes to all questions

 

Should you have asked me the same, it would have been "no" to all questions. 

 

Seriously, since you have the knowledge and skill going into this with both eyes open then you are ready to go.  You are obviously not a rookie.  Good luck with your build. 

[billybob]

Can second that. There is much to hear from near field type of...

Of course ...