Aperiodic boxes with aperiodic TL's - an idea.

[Shoog]

Hi all,
I have had my current speakers up and running for a few years now. They are Bigger is Better cabs with some 8"x10" Alnico Isophon drivers and Alnico Isophon helper tweeter. I love the sound of them and am generally very happy with how they perform. Early on I Mass loaded the ports to tighten and tidy up the choppy bass.

The thing is I listen to quite a bit of electronic music which has tight deep bass, and quite frankly the BIB goes deep, but not tight. Other than that I just love the sound of the Isophons. I have a pair of 10" Isophon woofer, which I was contemplating trying to mate with a nice pair of Foster FHT-5 tweeters, but last time I tried that with some big Tannoy's I failed. I really don't want the misery and expense of tunning a crossover from scratch. So I thought - why bother when I have some really nice full range speakers which do almost everything perfectly.

So my idea is take the tuned Isophon combo of Fullrangers and helper tweeter and mount them into a aperiodic box. This will probably lead to a smooth drop off of bass from about 500hz down, but should let the Isophons breath adequately. So I have been messing about with the idea of some TL's for the Isophon woofers. My idea is to build a set of TL's with the Woofer firing vertically into an Aperiodic box. the box is vented on all four faces ie back,front and sides. the aperiodic vents will take care of rolling of the 7K response to meet the top Aperiodic box, and should be easily tuned via the aperiodic vent stuffing. The back transmission line can be tuned to take up where the vents leaves off. I have included a sketch to help you visualise the concept.

So what would be the advantages of this approach;
-the top aperiodic box would be easily tuned and optimised independently.
-the aperiodic TL can be tuned independently, and the TL response can also be tuned independantly.
-because the aperiodic TL is firing from all four faces in phase it should take care of baffle step losses.
- there are no inductors in the system so phase shift and inductive loading of the amp should be less of an issue.

As usual this is purely a thought experiment at this stage and so I may have missed some essential reason why this whole idea just won't work, but i would appreciate any input on this idea.

Shoog

[Nikolas Ojala]

I know this is an old and long thread (yawn) but I got this mental association. The loudspeaker Esa Meriläinen built to demonstrate current-drive resembles a transmission line, although it is closed, so it does not breathe out of the box.

I refer to this page:
Clean-current speaker project | Current-Drive - The Natural Way of Loudspeaker Operation

That is one way to save some space and achieve good damping without expensive stuffing (such as angel hair, steel wool, etc.)

I also refer to another writer, and I add a quote here:

What makes woofers good candidates for AP boxes? Well, as you guessed, not all woofers will work correctly in this enclosure. While several physical factors affect AP performance (you need a lightweight, stiff cone, good power handling, and SVC subs seem to work better too), the single most important spec to look for is the Q factor of the sub. While Qes (electrical Q) and Qms (mechanical Q) can vary widely, and either by itself won't "make-or-break" this decision, it is...drum roll please...the woofer's Qts (total system Q) that determines the AP candidates! ANY WOOFER WITH A QTS OF .45 or LESS CAN WORK VERY WELL IN AP DESIGNS! I made that bold so it will stick with you guys. So, if you want to try your hand at this type of enclosure, seek the Qts spec of the woofer. If it is less than or = to .45, you have a winner. You will find that it is mainly the subs designed for ported enclosures that fit the bill, as subs designed for small sealed boxes (you know the ones...massive, heavy cones, stiff suspensions, heavy voice coils, etc) have a Qtc of .6 and higher. These subs tend to have a boominess that cannot be overcome with resistive damping and frankly, they sound like *** in an AP, so forget about em.
 

Source: AP Enclosures-The Aperiodic Cookbook | Tutorials | Team Audionutz

I quoted the most interesting paragraph.

Mr. Meriläinen used a speaker driver Scanspeak 15W/8434G00 with Qts = 0.25.

There are many real full range speaker drivers with sufficiently low Qts, such as:

Dynavox LY401F Qts = 0.26

Markaudio Alpair 12P Qts = 0.29

Markaudio Alpair 10P g1 Qts = 0.33

Tang Band W5-2143 Qts = 0.38

These all look like fine candidates.

[Nikolas Ojala]

On the other hand: The aperiodic enclosure could be constructed traditional way, with a small enclosure and an aperiodic vent on the back. Besides being aperiodic speaker that could also save space, and produce a subcardioid sound radiation pattern, which may be better than a conventional omnidirectional.

I was thinking about something resembling Gradient 1.4 but such way that it would be a woofer assisted wideband, completely aperiodic design.

Gradient 1.4 is a three way speaker with a coaxial tweeter + midrange in a resistance enclosure, and the woofer is in a bass reflex enclosure.

[Shoog]

This is the way I add woofers to my OB fullrange driver projects. Done it twice now, one with Isophon bass drivers with rear firing leaky vented small enclosure and another with a larger cab and again rear firing.
They integrate very well and extend well.

Shoog

[Scottmoose]

Originally Posted by Nikolas Ojala

I know this is an old and long thread (yawn) but I got this mental association. The loudspeaker Esa Meriläinen built to demonstrate current-drive resembles a transmission line, although it is closed, so it does not breathe out of the box.

It is a transmission line. Sealed 1/2 wave line. Most famously employed by B&W with their Nautillus, but there are many, many other examples.

[planet10]

by B&W with their Nautillus

Prototype (before damping):



dave

[GM]

Let's not forget arguably the most 'famous' of all, the plane wave tube [PWT] used to test various [multiple] devices :




GM

[Scottmoose]

That too.

[Squeak]

Originally Posted by GM

Let's not forget arguably the most 'famous' of all, the plane wave tube [PWT] used to test various [multiple] devices :

What is that? An reverse image search didn't turn up anything conclusive.

[GM]

It's the late great real Altec Lansing's multiple entry PWT for testing [16] horn drivers at once.

GM