Bookshelves, passives and a thought...

[kfa888]

So I have my 3rd set of passive radiator equipped speakers and am scratching my head. The latest ones are my newly refoamed EV Interface 3's and I am simply loving them. Deep bass, crisp highs and excellent mid range. It is a surprisingly good speaker. My first passive was a set of Genisis II's the really surprised me with deep bass you could feel out of a smallish cab and 8" woofer (10" passive) and an inverted tweet. The next surprise was my EV Interface 2's. Those are my daily office speakers and displaced a set of BA A60's and KLH17 and sound better than both IMHO. I snapped up these EV Interface 3's because of how much I liked the Interface 2's.

Blah Blah Blah what's your point Kelly... Well i have found the common denominator in these three similar designs is massive deep bass you can feel and thick rich presentation. Keep in mind these are all 8" 2 ways. These 3's are flat flooring me. After refoaming them and being more than impressed with what I heard I moved them into the living room today and was pretty surprised at what i heard. These are room filling speakers. They sound huge and have a lot of dynamics. The tweeter is also excellent. I would pick these over my BA A150's and JBL L100's EZ.

So my thought is the combo of a small robust driver lets the mids and high end shine while and massive radiating area of the passive really supported the bottom end. Combine that with a good tweeter and you have a successful speaker.

A while back many of you were arguing with me that a passive is just a port in another configuration. I think there might be one big factor that changes all this, radiating area of a speaker. An 8" 2 way ported design might displace the same amount of air but it does so through a port that is much smaller area than a passive. if you look at a 8" 2way with a passive the radiating area takes up a good 70% of the front of the cab. i wonder if the large radiating area and possibly the interaction of the woofer and passive on the outside of the cab have anything to do with the sound that i love coming from this design.

I am really struggling to understand it and put my finger on it but just like my Gensis II's did and now these EV's to a larger degree, i like this design. As simple a design that EV 3's is I just LOVE how it sounds. It is one of the best speakers i have heard of it's size. IMHO better than my EPI 201's, A150's, Wharfedale E50's, LA's, EPI 120c's... etc.

Thoughts?

 

[Sir.Byrd]

Buy more speakers with passives.

 

[Zilch]

There's no denying passives have a unique sonic character. Look up Small's seminal study of them in the AES anthologies for some insight.

If I were really into liking them, I believe I'd build a pair of speakers, one vented and one PR, with the same drivers and identically tuned, to see if the difference I was perceiving is real, what it is, and why it is.... :yes:

 

[kfa888]

If I were really into liking them, I believe I'd build a pair of speakers, one vented and one PR, with the same drivers and identically tuned, to see if the difference I was perceiving is real, what it is, and why it is.... :yes:

I have been thinking just that. :yes:

 

[JJJimmy]

There's no denying passives have a unique sonic character.

Absolutely...and in the right room, can sound spectacular! I've moved my CR-1020 / Polk 7b setup around to differrent rooms, and it's now finally settled in the third bedroom (my daughter's). It's a PERFECT fit, with incredibly detailed highs, sweet filling mids, and yes...depp rich REAL sounding bass.

 

[hypertone]

My Polk 7's really go deep. I'm positive that the single 6" could not go as low or have as much punch in a ported box.

 

[Zilch]

Easy. Replace the passive with the correct-size equivalent port and learn how right (or wrong) you are.

[Assuming you care to actually know.... :yes: ]

 

[RayW]

The not-so-easy part is that you have to match the moving mass of the PR with the air in a port so the port will probably be a monstrous thing looking like it walked out of a Dr. Seuss story.

 

[Zilch]

Are we getting down to it then, Ray? It's not just a matter of tuning the box to same frequency, PR and vent?

And I have to go read Small again myself?

[This COULD be dangerous.... ]

 

[tarior]

I like PRs myself! Keep the faith, bruthah!!

 

[RayW]

You've got it, Zilch. But it's a lot easier to say than to do. If you have a speaker/box combo that lends itself to a realistically sized PR then the port to get the same tuning will most likely be extremely long. Usually* a PR is used when you want to shoehorn a ported type alignment into a box that's "too small". It's easy to add mass to a PR but not so easy to add a couple of feet to a port.

I just did a "quickie" sim. I grabbed a random driver (old NHT 1259 which popped up in the library) figured a ported box for it and then cut the box size way down. The PR was realistic, if a bit heavy at 456g. Then switched to a port to see how it would compare. The minimum suggested diameter was 3.8" and the length was >47". Going up to a standard size of 4" made the port 52". If you're going to do that you might as well go with a Daline (kind of a cross between a transmission line and ported box).

I'm sure we could probably find a happy medium somewhere that we could compare but I fear it would be a compromise of both topologies instead of them showing off their respective strengths.

Ray

* - note, I said usually. If you start from the beginning designing for a PR then things go differently, a la Polk.

 

[kfa888]

You've got it, Zilch. But it's a lot easier to say than to do. If you have a speaker/box combo that lends itself to a realistically sized PR then the port to get the same tuning will most likely be extremely long. Usually* a PR is used when you want to shoehorn a ported type alignment into a box that's "too small". It's easy to add mass to a PR but not so easy to add a couple of feet to a port.

I just did a "quickie" sim. I grabbed a random driver (old NHT 1259 which popped up in the library) figured a ported box for it and then cut the box size way down. The PR was realistic, if a bit heavy at 456g. Then switched to a port to see how it would compare. The minimum suggested diameter was 3.8" and the length was >47". Going up to a standard size of 4" made the port 52". If you're going to do that you might as well go with a Daline (kind of a cross between a transmission line and ported box).

I'm sure we could probably find a happy medium somewhere that we could compare but I fear it would be a compromise of both topologies instead of them showing off their respective strengths.

Ray

* - note, I said usually. If you start from the beginning designing for a PR then things go differently, a la Polk.

Thank you for that information. When the boxplot program calculates this stuff does it also figure in that a 4x52 inch port is taking up a lot of internal cab volume and hence make the cab bigger as well. Seems from your findings that a passive radiator can produce more bass response for a given sized cab than a port?

When my speaker tester arrives I'll measure the EV Interface 3 woofer and the cab and see what it would take to make a ported system tuned to what this measures. I might be able to remove the passive and make a blank to cover the hole and add a port to if feasible and then measure the response. Should be fun.

Any further thoughts on the same air volume being rifled out a small port at high velocity verses the air moved by a large radiator over a large area with much less velocity (and possibly more in line with what the woofer is doing)?

It looks to me like we are finding significant differences.

 

[RayW]

Thank you for that information. When the boxplot program calculates this stuff does it also figure in that a 4x52 inch port is taking up a lot of internal cab volume and hence make the cab bigger as well. Seems from your findings that a passive radiator can produce more bass response for a given sized cab than a port?

I haven't used Boxplot since last century and don't really recall but most programs that I've used will adjust the volume to account for port size. As for the box size, you can always keep it the same and make the port external. That's what I meant when I mentioned the Dr. Seuss contraption.

When my speaker tester arrives I'll measure the EV Interface 3 woofer and the cab and see what it would take to make a ported system tuned to what this measures. I might be able to remove the passive and make a blank to cover the hole and add a port to if feasible and then measure the response. Should be fun.

:thmbsp:

Any further thoughts on the same air volume being rifled out a small port at high velocity verses the air moved by a large radiator over a large area with much less velocity (and possibly more in line with what the woofer is doing)?

I've never really thought about it until you started this thread. Intuitively I'd say moving air is moving air in this case. Usually when you get down to the tuning frequencies of a PR or port you're into the realm where you're pressurizing a room and not projecting a longitudinal wave so as long as the air is moving the objective is accomplished. However, you might be right about the radiating area above the room gain cutoff. I don't know, I never got into PRs that deeply. Guess there's no time like the present.

Ray

 

[kfa888]

As for the box size, you can always keep it the same and make the port external. That's what I meant when I mentioned the Dr. Seuss contraption.

understood (Minus the speaker in the end of it)...