Horn+TL DIY w/Scan-Speak 10"

I tried searching for "horn scan speak", which didn't turn up anything of relevance, so I'm making my first post here (go easy, right? ;)

Anyway...

I'm looking to make a transmission line subwoofer tuned to 19Hz, with horn loading in front, using the Scan Speak 10" paper cone sub driver. Unfortunately, I have very little experience in designing speaker enclosures, and could do with some pointers, or even a project drawing, if someone has already trodden this particular path.

Space isn't the biggest concern (obviously), but I would like, if possible, to keep the volume to 8 cubic meters at most, with an outer height of about 225cm or so.

heeelp. =)
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
suiram said:


Space isn't the biggest concern (obviously), but I would like, if possible, to keep the volume to 8 cubic meters at most....

I don't know if that was typo or not, but an enclosure of 8 cubic meters is about 280 cubic feet. With something that size, I would suggest forgetting about transmission lines and go for a set of super-efficient PA speakers.

Something to fit the bill would be a set of four Fane Colossus 24 inchers in 2 X 2 arrangement, tuned to 16 Hz. The four together raise the sensitivity to 107 dB @ 1M/1W, and if you pump 1,000 Watts through the whole system, you arrive at 140+ dB at 16 Hz. Surely, those figures constitute horn-like output and sensitivity. That is not even counting room gain, assuming there is a room still standing at the completion of the test.

Just set 'em up in your 8 cubic meter enclosure, and get ready to blast the bejeezus out of your neighbors. Which is only fair, since they are certain to want to come over and blast the bejeezus out of you.

The following is the response for 4 Fane Collosii in an 8 cubic meter enclosure:
 

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Er. I think you misunderstood.

My aim is not to obtain a colossal bass response; I want controlled resonance (hence the 19Hz transmission line), high efficiency (hence the horn loading) and effortless reproduction.

The space I have available to place such a subwoofer in is large enough that an 8 cu.m. (280 cu.ft.) enclosure would fit, but beyond that it's really taking up too much space. Considering that I would have to actually move this enclosure, as well as the fact that I don't really want it that big, the 8000 litre (apx 2000 gallon) enclosure is way over the edge. But if that's necessary to tune the TL and horn deep enough without an overly complex folding (I would like to keep the folding to a minimum for the horn section), then I would be willing to sacrifice that much space.

Nothing would please me more than to see some genious figure out a way to beat physics into fitting all this in a cubic foot that's easy to build =)

I'm used to the bass response from the new generation of Stax earspeakers, and they have a pretty decent response below 10Hz, so I guess I'm a bit spoiled..
 
Marius--What you want to do is weird and probably won't work. Horn woofers work best with the rear of the driver enclosed in a compression chamber. Also, you can't horn-load just any woofer and get good results, horn-loading calls for drivers with a high fs and a very low QTS, in the .20s---light cones and BIG motors which is why guitar amp speakers like the EV 15L and 12L work well. Resonance control with a basshorn is superior to that of any other enclosure, the air load in the horn provides excellent damping for the driver. A well done basshorn will have very little overhang, the driver pretty much just stops dead because of the airload and the overdamped nature of suitable drivers. Hell, I don't know, maybe a t-line behind a basshorn would work, never heard of anyone trying it though. Seems like a complicated solution to a problem already solved more simply.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
Just to be sure of what we are talking about here. Are you proposing:

A) A horn in front of the Scan-speak for mids and highs, and a transmission line behind the Scan-speaks?

or

B) Scan speak conventionally mounted in front of cabinet with the rear radiating into some kind of transmission line-horn combination?

There is quite a difference between these two concepts.

Just a few things I thought I would mention.

While I have never heard of a "horn in front, transmission line in back" arrangement, years ago a "horn in front, bass reflex in back" was not uncommon. From this forum, I have noted that drivers that are suitable for bass reflex,(ported), cabinets are pretty much the same ones that are suitable for transmission lines. So if choice A is what you want, I would think you have a fighting chance of getting it done successfully. You would just be substituting a transmission line for the bass reflex enclosure.

I have come across the "rear horn" principle, where the woofer is mounted conventionally but the back radiates into a bass horn. So if choice A is what you are seeking, it would seem to be a combination of these two types which were produced commercially years ago. The book I read about these was written in the early sixties, and talked about some of the models in the past tense even then.

Finally, the Altec Voice Of The Theatre used the "horn in front, reflex in back"principle and was for years considered one of the best loudspeakers available at any price. I wouldn't know how to approach constructing a model, but the idea might work.

Here is a link to somewhat related enclosures:
http://www-user.uni-bremen.de/~carnivor/horn/hornfolds.html
also
http://www.beauhorn.com/pages/frame.html

Good luck!