Dispersion, narrow, controlled, or bi?

@phusis wrote:  "I prefer a large radiation area and front firing, tall horn or horn hybrid design with a controlled, narrow and fairly uniform dispersion pattern."

Me too!  But I haven’t done anything as large as your speakers (yet), so you are getting good radiation pattern control down lower than I am.  What are the radiation patterns of your big horn and tweeter, if you don’t mind?

Phusis again:  "Why isn’t the power response of the main speakers of a primary concern here?"

Well I suppose the NET in-room power response is the primary concern, and what I was suggesting to @erik_squires was a way of CORRECTING the in-room power response by adding correctively-EQ’d speakers whose response arrived late enough that it was only contributing to the in-room reflection field.  To put it another way, the main speakers’ power response is essentially unchangeable without also changing the direct sound, so if we want to leave the direct sound unchanged but improve the in-room reflection field, adding a pair of dedicated-to-reflections speakers is one way to do that.

Phusis once more:  "Introducing a reflective sound field "actively" with additional speakers is also an additional measure to get right. Isn’t that a degree of complexity that can invite more problems than what it tries to solve?"

Yes!  That’s why I was making a few suggestions to Erik in response to him having "often wondered what the results would be of using a separate preamp/amp/speaker pair to reflect sound." 

Tying back in to the topic of this thread, "dispersion":  Reflection-field-correcting rear-firing drivers are something I’ve been doing passively, as an integral part of the loudspeaker system design, for many years. 

@audiokinesis wrote:

Me too!  But I haven’t done anything as large as your speakers (yet), so you are getting good radiation pattern control down lower than I am.  What are the radiation patterns of your big horn and tweeter, if you don’t mind?

The large format Constant Directivity EV HP9040 diffraction horn (as the model number implies) has a 90 and 40 degree horizontal and vertical coverage (down to about 500Hz, it seems), and the dispersion pattern of the JBL 2405 Alnico tweeter sits at 90 and 30 degrees horizontally and vertically - in both cases according to the specs linked.  

Well I suppose the NET in-room power response is the primary concern, and what I was suggesting to @erik_squires was a way of CORRECTING the in-room power response by adding correctively-EQ’d speakers whose response arrived late enough that it was only contributing to the in-room reflection field.  To put it another way, the main speakers’ power response is essentially unchangeable without also changing the direct sound, so if we want to leave the direct sound unchanged but improve the in-room reflection field, adding a pair of dedicated-to-reflections speakers is one way to do that.

I see. So these measures being corrective are a compensation for what the main speakers are typically able to, or rather incapable of doing in and by themselves. In principle however it ultimately follows - or so it could be deduced - that the power response of that produced by the main speakers alone DOES matter as a primary factor - insofar it can be uniformly achieved in a given listening space?

From your chair: is it even possible for main speakers as standalone units to get the NET in-room power response right (front firing, di- or bipole or otherwise), or is this a matter that can be at least partially alleviated with the design approach (i.e.: from the likes of horns) and through sheer physics/size as I implied earlier? 

Tying back in to the topic of this thread, "dispersion":  Reflection-field-correcting rear-firing drivers are something I’ve been doing passively, as an integral part of the loudspeaker system design, for many years. 

Why isn’t this a more widely addressed field of concern from other/more speaker manufacturers?

What I meant by "actively" (i.e.: not how the speakers are configured crossover-wise) was to point to the corrective measures being done additionally with extra speakers to aid the reflective field as an actual, actively addressed area by its designer.  

@phusis wrote:  "The large format Constant Directivity EV HP9040 diffraction horn (as the model number implies) has a 90 and 40 degree horizontal and vertical coverage (down to about 500Hz, it seems), and the dispersion pattern of the JBL 2405 Alnico tweeter sits at 90 and 30 degrees horizontally and vertically - in both cases according to the specs linked."

Sweet! 

I really like your radiation pattern choice, it’s wide enough and consistent enough to give very good coverage of the listening area, but not so wide that you have an excess of early-onset reflections. And you will have a good directivity match between your woofers and the horn in the crossover region. Those big woofers in their bigfaced box will have useful pattern control probably down to the Schroeder frequency just from their sheer size.

@phusis:  "So these measures being corrective are a compensation for what the main speakers are typically able to, or rather incapable of doing in and by themselves."

Yes!

@phusis:  "In principle however it ultimately follows - or so it could be deduced - that the power response of that produced by the main speakers alone DOES matter as a primary factor - insofar it can be uniformly achieved in a given listening space?"

Yes. There are definitely limits on how much correction one can do to the in-room power response via secondary rear-firing drivers.

@phusis:  "From your chair: is it even possible for main speakers as standalone units to get the NET in-room power response right (front firing, di- or bipole or otherwise), or is this a matter that can be at least partially alleviated with the design approach (i.e.: from the likes of horns) and through sheer physics/size as I implied earlier?"

Absolutely!   There definitely are other approaches than the one I use which “get the NET in-room power response right”, and imo YOUR approach (big horns and big woofers) is one of them!

Imo there can also be a spatial quality benefit arising from the contribution of rear-firing drivers, even if "correction" of the reflection field’s spectral balance isn’t really needed.

@phusis:  "Why isn’t this a more widely addressed field of concern from other/more speaker manufacturers?"

Manufacturers tend to embrace paradigms which they have found to work well, and presumably for most of them rear-firing drivers don’t offer something they place a high priority on.

For instance, most manufacturers make cone-n-dome speakers that have wide radiation patterns, so they are already getting a lot of reflection energy out into the room. They may not see much potential benefit to adding more reflection energy even if it is corrective.  (The idea that rear-firing energy CAN be corrective may not be very widespread.)

And some manufacturers deliberately have rather narrow radiation patterns, which results in a high direct-to-reverberant sound ratio. For these manufacturers, reducing the direct-to-reverberant ratio via the addition of rear-firing drivers probably seems counter-productive.

Then there’s the question of cost/benefit: Even if there is some benefit from adding rear-firing drivers, could the same amount of money spent elsewhere make a bigger improvement?  And, perhaps the most practical question:  Will having rear-firing drivers make a worthwhile difference in sales?

My own paradigm goes something like this: “A speaker should get two things right: The direct sound, and the reflections”. Getting the reflections “right” is the hard part, and imo it’s worth a fair amount of effort, but clearly I’m in the minority.

@phusis:  "What I meant by "actively" (i.e.: not how the speakers are configured crossover-wise) was to point to the corrective measures being done additionally with extra speakers to aid the reflective field as an actual, actively addressed area by its designer.  

Got it, thanks.

Are your speakers "active", crossover-wise? 

Duke

@audiokinesis wrote:

Sweet! 

I really like your radiation pattern choice, it’s wide enough and consistent enough to give very good coverage of the listening area, but not so wide that you have an excess of early-onset reflections. And you will have a good directivity match between your woofers and the horn in the crossover region. Those big woofers in their bigfaced box will have useful pattern control probably down to the Schroeder frequency just from their sheer size.

Initially I bought the EV system with the smaller HP940 horn (it uses the same compression driver, the DH1A, regardless), and though I was offered the larger HP9040 horn at the time I feared it would "overload" the listening space and thus opted for the smaller horn. It became clear however that the HP940 horn didn’t load the very powerful DH1A driver (2.1 Tesla flux density) properly, sounding too hot in the upper presence region, whereas the HP9040 horn made for a much smoother, more fully fleshed out, relaxed and physical presentation.

It goes to show that while the larger horns might at first be deemed crazy, too up front sounding, overloading the room etc. (a classic case of "listening" with the eyes or one’s preconceptions), they’re typically the more well-balanced, relaxed and smoother sounding variants over the smaller ones. A bit like large panel speakers on steroids.

It was apparent as well that the larger horn made for a more coherent and of-a-piece sound, which confirms a good directivity match at the crossover to the woofers, as you point to. Indeed size matters here :)

For instance, most manufacturers make cone-n-dome speakers that have wide radiation patterns, so they are already getting a lot of reflection energy out into the room. They may not see much potential benefit to adding more reflection energy even if it is corrective.  (The idea that rear-firing energy CAN be corrective may not be very widespread.)

I’m wondering if the typical "cone-n-dome" speakers are so popular with the manufacturers from the perspective of a deliberate design choice or more a reflection of a smaller size factor being a better business proposition? Perhaps I’m assuming more than wondering here, but I’m guessing power response and reflection field isn’t at the top of their agenda, or at least something they’re less likely to be successful with the typical designs choices of front firing only, direct radiating smaller woofers/mids and dome tweeters. 

Then there’s the question of cost/benefit: Even if there is some benefit from adding rear-firing drivers, could the same amount of money spent elsewhere make a bigger improvement?  And, perhaps the most practical question:  Will having rear-firing drivers make a worthwhile difference in sales?

I’m not sure most manufacturers even considers the alternative of adding rear firing drivers (with the exception of tweeters, perhaps, which seems to be about something else than getting the reflection field right per se).

Are your speakers "active", crossover-wise? 

Yes they are, with the exception of the JBL Alnico tweeters that use a simple 1st order high-pass filter with Mundorf Silver/oil caps coming in at ~11.5kHz. The Alnico’s are 105dB sensitive, but match wonderfully with the ~110dB large EV horn with a rather natural sloping here - indeed a lucky match. I don’t like the top end to come across as "lively" but rather prefers it blends in smoothly as a natural extension of the mids. I’m more of a "based around the midrange"-sound kinda guy, even though I’m not british :)

Obviously in my case the configuration is outboard actively with a Xilica DSP and the great british MC² Audio amps (S800’s for the EV’s, vertically bi-amped, and a T3500 for the subs). 

What are your thoughts on active configuration, and is it something you have considered for your own designs?

I think that for the best, "pinpoint" imaging you want a narrow dispersion and little to no reflection to "smear" the locations of the various "instruments" in the room.

This would provide the best "They are here" experience.

Experimentation with the Heil AMT shows the best imaging is attained when the rear signal is blocked off.