Hybrid H-Frame, OB and nude driver

[ErikdeBest]

I saw these yesterday, looks quite allright I think?!

Dayton Audio ES104AMT-4 AMT Esoteric Series AMT Tweeter 4 Ohm

[Pano]

Having built and heard quite a few Open Baffle speakers over the past 15 years, it looks to me like you are really making this much more complicated than it needs to be. Of course, overly complicated and edgy might be your goals.

I think it time for me to take my leave, as my advise will have little effect on this project.

[CharlieLaub]

Originally Posted by iamvalheru

Yesterday I drafted on my CAD a quick 18" H-frame - nude 15" - nude 6" - nude Ribbon and it the 15" over the 18" pushes the tweeter way to high to be useful.

Therefore, and to try and keep the speaker assembly as small as possible, using nude drivers, and with the tweeter around 40" off the ground, how would one of these two other configurations fair at providing good sound quality, directivity and SPL output?

1. MMTMM all nude divers using SB17CAC35-4;

2. MMTMM all nude drivers, using a suitable 10" (e.g. Peerless 830668) and SB17CAC35-4.


Thank you

I have encountered the same problem. When you try to use too many bands the physical size of the drivers pushes the tweeter location too high.

One way around this is to have a mono subwoofer in the center, and then a 3-way WMT stereo pair, one on either side. The concept of a large, deep H-frame works well for the mono sub. For example, I have an H-frame that has a 24"x24" mouth opening and is about 36" deep. I use a high excursion, high Qts 18" driver in it, and that provides plenty of bass output down to 25Hz or 30Hz.

I use the large H-frame sub up to 100Hz, where I cross over to the mains. If I use a 15" high efficiency pro audio woofer there is no need for a baffle for the woofer, and I can make an all-nude main speaker.

This is the concept I am pursuing now with my current build. Unfortunately the build is stalled because it is deep winter here and I do not have a shop or heated garage to work in.

[iamvalheru]

@Pano

Your advise is well appreciated, I am trying to achieve as big a range of constant directivity as possible, but the fact that the TB full range has so poor rear radiation kind of screws this up as it was my intent to use it to keep my project KISS.

[iamvalheru]

Originally Posted by CharlieLaub

One way around this is to have a mono subwoofer in the center, and then a 3-way WMT stereo pair, one on either side. .

Stupid question, as I never played with mono subs; what signal do you input a single 18" H-framed mono sub when your have 2 channels?

Originally Posted by CharlieLaub

If I use a 15" high efficiency pro audio woofer there is no need for a baffle for the woofer, and I can make an all-nude main speaker.

Any recommendation for such a 15" nude driver?


Thank you

[iamvalheru]

Originally Posted by Pano

Eminence Beta-8 Super easy to use up to 5K and needs just a small inductor to flatten it.

Would the Eminence DeltaLite II 2510 - 8 ohm 10" woofer be a better choice to bridge between the 18" H-frame and the ribbon tweeter?

It looks like it would offer better rear radiation than the Beta-8.

Eminence DeltaLite II 2510 | 8 ohm 10" 250W Neodymium Pro Audio Woofer

[CharlieLaub]

Originally Posted by iamvalheru

Stupid question, as I never played with mono subs; what signal do you input a single 18" H-framed mono sub when your have 2 channels?

You mix (add) the stereo left and right channels to get the mono bass signal.

Originally Posted by iamvalheru

Any recommendation for such a 15" nude driver?


Thank you

I use the Eminence Deltalite 2515. It has very high sensitivity and low distortion. The basket is very open. It can use used to a relatively high frequency and it is not all that expensive. Xmax is not high (around 4.5mm) but if you only need to use it down to 100Hz that is plenty, even at high SPL.

[diypole]

An 8" crossed to a 4" fullrange will maintain excellent directivity through the most difficult point in a dipole implementation.

Use a Scan 10f/4424 on top, crossed around 1000hz and you'll likely not miss a tweeter. It measures close to the same from the front or the back. A good 8" with minimal baffle will get you down under 200.

Linkwitz crossed at 120hz in his design. I've done just under 200hz with a Scan 22W 4534. Could have gone lower but did not want to sacrifice the headroom.

If you want super simple, you could mtm a scan 10F with 2 of those 10" peerless 830668 you referred to in parallel on a minimal baffle and get down to 60hz easily.

Although beaming with an 18" or 15" is going to cause directivity issues above 250-375hz respectively, even if you have one that sounds decent up there the limiting factor with the H frame will be it's resonance, and that will likely keep you wanting to use it under at least 150Hz.

The first serious dipole I ever built as a newbie 17 years ago used 2 peerless 10" in parallel, giving 93db of sensitivity, crossed to a BG Neo8 around 700hz (they had just come out) on a baffle about 11.5" wide by 2.5" deep and I flattened them to 60Hz passively...they were actually 3db down at 50hz and I still had 86 or 87db sensitivity overall.

DSP was not an option back then.

I would not put the neo 8 on a baffle that wide nowadays, but back then we did not understand the relationship of baffle size to driver size in producing the dipole null, and there was one narrow dip in the measurement. Couldn't hear it and other than that it was flat from over 10khz to 60hz and is still being played extremely loudly at the owner's house.

Actually I would never use an 8" planar at all knowing what I know now. They sounded great when you were sitting at listening height, however when you stood up you could hear the change due to the narrow vertical directivity of the planar, but I learned a lot and they sounded excellent for a 2 way dipole.

John K also used those peerless 10" as a less expensive option for the dipole subwoofer in the last speaker he offered for sale.

So anyway, in my opinion use a good 3 or 4" fullrange down to 1000hz or so and cross it to an 8" with decent x-max to get you down to 200, or a 10" to under 100, or two 10" paralleled all the way down to your 18".

[diypole]

A single nude Scan 22W/4534 with an sd of 235cm squared and 5.7mm x-max is capable of 108db at 200hz, and 99db at 141hz conservatively. Add 6db to those numbers from the subwoofer at the crossover point.

2 nude peerless SLS-P830668 in parallel are capable of 104db at 100hz conservatively. They are capable of 95db at 70hz, but below 80hz the signal will be coming out of both speakers, so really it's 101db for all 4 of them playing. If crossing over to a sub at 70hz add 6db at the crossover point and you've got 107db capability and if you're using stereo subs down there in monaural land it will be another 6db...this is a conservative estimate with a nude driver and at those frequencies it will likely be more depending on how close to other surfaces they are.

I would use at least a bit of rectangular or oval baffle personally, an inch or two on each side will not affect the response and may improve it. At the very least they will start rolling off a bit lower and require less compensation, retaining headroom.

[CharlieLaub]

diypole has some good suggestions, above.

I looked into the 10F several years ago, when I thought that smaller drivers would be best for dipole midranges. It's an excellent driver all around, and not bad as a tweeter used as diypole suggests. You will definitely need to take the response into account, as 1kHz is just below the dipole peak and it's changing fast in this FR region.

I have attached the on and off axis responses I measured for the driver, nude, from the front. Unfortunately I no longer have my rear response measurements, but I recall that there was a significant deviation from the front response starting just above the dipole peak. Most drivers deviate to the rear in this region, and the 10F was just not what I wanted at the time. It would probably work just fine, nonetheless. The sharp dipole peak was another turn off, although it can be tamed a bit with EQ. Unfortunately the peak shifts in frequency as you move off axis, so you can't really "fix it" on all axes.

These days I prefer something that is a little smoother in the 2kHz region, and/or wherever I want to cross it over, and I find that drivers in the 6" class are best in this regard. That's why I suggested the SB17 as a dipole mid.