DIY Speakers tailored for small room

[ppataki]

What are the downsides of bigger diameters?

Bigger diameter = narrower dispersion and beaming (= less reflections in a room but very small sweet spot - I love it, other people hate it)
The advantage is bigger cone surface which can move more air = can be pushed to lower bass and/or higher SPL

 

[ppataki]

(= less reflections in a room

take a look at the IR curve of my 15" Fane system:

Fane 15-300TC 15" full range speaker based project

... of course... now the problem is that I want a pair of these Fane drivers (or at least a chance to hear 'em), and they're NLA. :rolleyes:;)

audiosciencereview.com

Practically no reflections.....(all are below 10%) in an untreated room

 

[Salt]

Rising diameter means narrowing dispersion, so if you want wide (constant) directivity, the smaller is the better.
But if you aim at narrow beaming (to avoid, for example, reflections/echoes from sidewalls), greater diameter may fit your needs better.

 

[Duke]

... and building 4 small subs to handle everything below 100hz.

I resemble that remark!

What pops into my head when I see all that space behind your speakers is, bipolars. The spectrally-correct output from the rear-firing drivers will have a long reflection path and imo this is desirable.

You can do a test run with the speakers you already have, in effect comparing a single monopolar speaker with a single bipolar speaker:

Place one speaker in the middle of the room at your normal speaker distance, facing you. Place the second speaker maybe six inches behind it, facing the opposite direction. Ideally send a mono signal to each speaker. If you have a balance control, you can use that to effectively turn the rear-facing speaker off. Anyway the idea is to compare monopole (signal only going to the speaker facing you) vs bipole (signal going to both speakers). You may want to turn down the volume for the bipolar configuration a little bit so that it doesn't get an unfair advantage from the slight increase in SPL from the extra reflection energy contributed by the rear-firing drivers.

Of course this won't be a controlled blind test but imo such is not always needed in order to make a sufficiently informed evaluation.

If you find the bipolar configuration to have some promise, here's a link to an article I did for an online magazine about thirteen years ago. Some of the ideas are outdated but some of them may be useful to you:

The Controlled-Pattern Offset Bipole Loudspeaker

 

[Svarog98]

I resemble that remark!

What pops into my head when I see all that space behind your speakers is, bipolars. The spectrally-correct output from the rear-firing drivers will have a long reflection path and imo this is desirable.

You can do a test run with the speakers you already have, in effect comparing a single monopolar speaker with a single bipolar speaker:

Place one speaker in the middle of the room at your normal speaker distance, facing you. Place the second speaker maybe six inches behind it, facing the opposite direction. Ideally send a mono signal to each speaker. If you have a balance control, you can use that to effectively turn the rear-facing speaker off. Anyway the idea is to compare monopole (signal only going to the speaker facing you) vs bipole (signal going to both speakers). You may want to turn down the volume for the bipolar configuration a little bit so that it doesn't get an unfair advantage from the slight increase in SPL from the extra reflection energy contributed by the rear-firing drivers.

Of course this won't be a controlled blind test but imo such is not always needed in order to make a sufficiently informed evaluation.

If you find the bipolar configuration to have some promise, here's a link to an article I did for an online magazine about thirteen years ago. Some of the ideas are outdated but some of them may be useful to you:

The Controlled-Pattern Offset Bipole Loudspeaker

Great idea to incorporate the acoustically unused space! After reading both toole and your article i came up with 2 ideas. If very early reflections are less or even undesirable in this particular case then absorb the whole listening area as much as possible (should increase imaging) and let the other half of the room be very reflective and let it work as a reverb chamber:

Here is a variant with the front firing speakers being further apart for a wider image, but then of of the bipolar have to be separated, is that bringing me trouble?

or maybe full range drivers with narrow dispersion instead of heavy absorbtion?

For the swarm subs: would 4 x 8" be enough for this small room or is it not going down to 20hz?
3 x 10" and one 12" would be optimal i guess...

 

[Duke]

Great idea to incorporate the acoustically unused space! After reading both toole and your article i came up with 2 ideas. If very early reflections are less or even undesirable in this particular case then absorb the whole listening area as much as possible (should increase imaging) and let the other half of the room be very reflective and let it work as a reverb chamber:
View attachment 317891
Here is a variant with the front firing speakers being further apart for a wider image, but then of of the bipolar have to be separated, is that bringing me trouble?
View attachment 317890
or maybe full range drivers with narrow dispersion instead of heavy absorbtion?

For the swarm subs: would 4 x 8" be enough for this small room or is it not going down to 20hz?
3 x 10" and one 12" would be optimal i guess...

I'd suggest trying the cobbled-together "single monopolar speaker vs single bipolar speaker" test before investing in another pair of speakers.

And I'm not really confident that back-to-back or splayed monopole speakers, two per channel, would work as well as purpose-built bipolars. But it may be more practical.

 

[Svarog98]

I'd suggest trying the cobbled-together "single monopolar speaker vs single bipolar speaker" test before investing in another pair of speakers.

And I'm not really confident that back-to-back or splayed monopole speakers, two per channel, would work as well as purpose-built bipolars. But it may be more practical.

I performed the test today:

1. Having one revel speaker in the middle of 2 side walls makes it sound very decent ( even though only one was playing )
2. Having the second one as a virtual bipolar made it make sound fuller, without messing things up too much
3. Hard to come to a full conclusion without the stereo imaging, which i really missed BUT i often hear to the revels from the other side of the room and enjoy it very much

(Performed without subs/DSP which made a real decision even harder)

From what i heard the diffuse/reverberant field is most likely what i was looking for when buying speakers, funny (or sad) enough, that i discarded all bipolars because i thought they're no real speakers...

 

[Svarog98]

I’ve read the article again (a good read btw) and I realised that I misunderstood a lot of things in the beginning.
I initially thought that the front and backfiring side of the cabinet are adjacent but they’re not, otherwise it would mean front and side firing…

With my setup the right speaker is very next to the wall.
Even worse: the left speaker has an angled back wall with would result in reflecting its rear output directly back to me…
Is it possible to build a speaker with this kind of approach but with a front and side baffle?

 

[Duke]

Is it possible to build a speaker with this kind of approach but with a front and side baffle?

Yes! In fact my "bucket list" includes building something like that; it's not at the top of my bucket list but it's on it.

I think it would be called a "splayed array".

Here is a commercial design with that sort of configuration, and as you'll see it impressed me enormously:

Sean McCaughan of ESP's killer new design

The best speakers I heard at RMAF 2015 were ESP's new "Double-Bass" speakers in Room 510. Sean McCaughan is the designer and this just might be the most intelligent speaker design I've ever seen, a statement that I will try to explain shortly. Here's what one looks like: It's not as big...

www.whatsbestforum.com

And here are Amir's photos of the room, post number 29 of this thread if the link doesn't take your straight to it. (Ignore the caption in the box below, it's referring to something else):

Amir RMAF 2015 Picture Thread: Part 1

Note how this $1,000 system had speakers on stand but not the one at $1,500! Sadly it still sounded poor. Why do they insist on putting an LP in such low cost rooms??? I mean who is so constrained in budget but is willing to invest in buying LPs? Take that out, make it all digital and...

www.whatsbestforum.com

 

[Svarog98]

The shape if the hotel room looks very familiar to mine. If this system sounded incredible then I hope that building them will be worth it .
I will build the 4 subs first. I heared it’s not hard to do and I can get some experience first.