New design - A Seas all metal 3-way

[Zvu]

My cabinets are now at the paint shop but as soon as they are finished, i'll give it a listen.

[Dave Bullet]

An epiphany!

The Seas 27tdfc hates a 2KHz crossover.

This is much much better. I feel I am finally getting somewhere with this design.

This is what i have in my parts bin. May optimise for flat on axis response.

Funnily enough - this "flatter" response is less forward than the BBC dip version I had before.

This seems a funny test. but I put my ears < 1 m in front of the tweeter / midrange - in the middle. BEfore, the tweeter was drowning out the midrange. Now - they are balanced.

[Zvu]

At what frequency is the crossover now ?

Did any off axis measurements ?

[Dave Bullet]

3khz. no off axis measurements as weather here has been awful and I prefer to measure outside to get a longer gate.

However walking around the room it doesn't matter where I listen from. These have far less fatigue. Question is am I missing any detail or bringing the L15 breakup into play?

[Zvu]

I don't think break up will be the issue but distortion might. Not saying that it will, but it might.

[Dave Bullet]

Thanks - yes breakup inducing harmonic distortion lower down. It's hard to say. More listening is required. Maybe that might be the next problem (and a midwoofer / midrange driver swap is the only solution), however the tweeter was definitely the problem before. I could live with this system, but time will tell.

My distortion measuring ability in the past has been poor. I blame technique. I'll try again when I can get outside.

[Dave Bullet]

The 27tbfcg also benefits from a higher order and higher xo. If you are going to spend Megabucks on woofers and midrange drivers my recommendation would be to go forvpistonic midrange and very steep slope to attenuate breakup and push the mid to tweeter xo as high as possible to relieve the tweeter of any stress and keep it open sounding. I think those that crossover a 1" some tweeter below 2.5khz ... Any order
..are compromising the systems potential

[Dave Bullet]

The 27tbfcg also benefits from a higher order and higher xo. If you are going to spend Megabucks on woofers and midrange drivers my recommendation would be to go forvpistonic midrange and very steep slope to attenuate breakup and push the mid to tweeter xo as high as possible to relieve the tweeter of any stress and keep it open sounding. I think those that crossover a 1" some tweeter below 2.5khz ... Any order
..are compromising the systems potential

Well I'm going to eat my own words. Humble pie tastes nice.

Anyone crossing over the L15 above ~ 2KHz is limiting the systems potential :-) There's no getting away from the H3 peak of the L15 ~ 2.7KHz.

I was playing some classical guitar (Stanley Myers, Cavatina) and with the higher ~ 2.8Khz crossover, it sounded as if the midrange box had no fill and the backwave was muddying the sound / exciting the cone. There's a lot of sub 3KHz content and not a lot above in that track allowing the tweeter to be silent and the midrange to show its potential.

Moving the xo point down (still same steep slopes) to ~ 2.1KHz really cleans this up. I think the L15 should cross lower, but I think the tweeter starts to sound compressed to me as the volume goes up.

I think I've found my "compromise" spot.

[Zvu]

I think it's time for waveguide loading

https://heissmann-acoustics.de/test-wg148r-noferro-900/

Then you can cross it as low as you want without tweeter being stressed.

[Dave Bullet]

Thanks Zvu. I think you're right that would solve a lot of problems and also Z align the voice coils

However it would require a cabinet redesign for the waveguide and also a little more skill and daring to fit the waveguide. In any case I've started the front. I have bugger all tools. Not even a table saw so it's slow progress and not very accurate.

The photos are of red cedar I'm putting on the front

[Juhazi]

Carved waveguides look just fantastic! But there is the devil in details - throat should match the faceplate seamlessly.

[Zvu]

@Dave:

I've just checked the looks of your front and it looks like there is a room for 14.8cm waveguide (Visaton WG148R). Coupling Seas TDFC tweeter to a waveguide shouldn't be a problem since Noferro 900 from the link i posted has the same front plate. TBFC/G has metal grill so that won't fit without some modifications.

[sdl2112]

Hey Dave, have you considered the SEAS DXT tweeter...might just fit the bill if you have the budget.

[Dave Bullet]

@Dave:

I've just checked the looks of your front and it looks like there is a room for 14.8cm waveguide (Visaton WG148R). Coupling Seas TDFC tweeter to a waveguide shouldn't be a problem since Noferro 900 from the link i posted has the same front plate. TBFC/G has metal grill so that won't fit without some modifications.

Thanks Zvu that's good to know. Yes a 14.8cm waveguide will fit :-)

A dumb question.... I presume the waveguide loading boosts the mid - lower treble frequencies (~ 800 - 2KHz), therefore you are targeting a high FR crossover and thus do not loose any amplitude but lower distortion / excursion?

If so - that might be just the ticket. I also have a pair of 27TDFC (no grille) drivers I could use.

I was trying to use the 27TBFC/G as it seems (completely subjective) to resolve a little more detail than its fabric dome counterpart.

[Dave Bullet]

Hey Dave, have you considered the SEAS DXT tweeter...might just fit the bill if you have the budget.

I will look into that.

My concern is *any* (sweeping statement) 1" dome tweeter @ 2KHz Fc sounds a little harsh / forward, so I might be in the same boat.

It's not a matter of distortion or powerhandling... it's the sound. Hard to explain. The 27TBFC/G looks fine on paper, but sounds nicer crossed higher... and that's playing on a system where the L15 is introducing 3rd order HD!

[Zvu]

Here's the same tweeter measured without waveguide:

https://heissmann-acoustics.de/test-seas-noferro-900-h1025-06/

... and with waveguide:

https://heissmann-acoustics.de/test-wg148r-noferro-900/

Here's my measurement of Morel DMS30s without (blue) and with the waveguide (red).




As you can see, it adds quite a bit under 10KHz. That makes crossover electrically higher or acoustically lower, depending on your reference point. Look at the transfer function at my Technocracy thread. Electrically the crossover frequency is at about 2.4KHz but acoustically it is around 1650Hz.






Distortion of Noferro-900:



Distortion Noferro-900 in Visaton WG148R waveguide:

[Dave Bullet]

Let me state this simply. If a waveguide boosts the above range, allowing you to effectively apply a XO at a higher Fc (such as 3KHz) then I think that would off load the tweeter and be beneficial.

If the waveguide primarily provides only really helps sensitivity, low end shaping or dispersion - then it won't help me.

Its lowering the amount of power you have to put into the tweeter sub ~ 2.5KHz for the same acoustic amplitude that will help.

[Dave Bullet]

Cheers Zvu - I missed your post - you've answered my question thanks!

[Dave Bullet]

Ok - my latest rambling (and hopefully final). I've settled on a ~ 2.1KHz xo. The more I listened to these speakers, the more I have learned to listen for the right and wrong things.

I'm happier now with these. They tame the brightest recordings whilst not sacrificing the detail of good ones. There are still recordings that need further equalisation - but that is not a function of the speaker.

I've decided not to up the level of a waveguide. I might well do this for my next project when I build some more confidence or experience. I could retrofit one here and have no issue with redesigning the crossover. But the thought of tweeter disassembly / modification is a step too far for me. Even if it means just removing a faceplate

I've overlaid traditional LR4 slopes (pink colour). I've been aggressive with the slope between mid and tweeter and very subjectively, I think the Tweeter 5th order and 6th+ order slopes pays off. It allows me to play the L15 as high as I dare before the H3 junk creeps in. It also allows me to play the 27TBFC/G as low as I dare without feeling the upper mid and any excursion is robbing the detail of the treble.

Impedance is also healthy. A 4.5 minimum across the board above woofer box resonance and max of 11.6 ohms.

[TEK]

Seems like a good plan. Looking forward to follow the build process as well!

[Dave Bullet]

Making dust = making progress. I don't have much in the way of tools, so a lot of this is very time consuming. I'm using my plunge router with this half spacer thing bolted to the bottom so I can "nibble away" at the MDF to flush trim the odd angles. Seems to work fine.

The baffles have sanded up nicely. Going to start routing the driver holes and then add bracing to the cabinets.

[Zvu]

Patient guy can do something that looks nice with great tools.

Only skillful guy can do something that looks nice needing only basic tools.

The path of skill you have chosen - young padawan

[Dave Bullet]

Progress....boxes lined inside, baffles finished. Just morecoats of varnish and paint the rest and build the crossovers

[TEK]

Looking nice.
Wooden front baffel. What is the plan or the sides and back?
Are you going to paint them? If so, make sure to seal off the mdf ends before painting. Easiest way is probably buy adding a thin layer of wood-glue (maybe thinned with some water) before base coat.

[Dave Bullet]

Looking nice.
Wooden front baffel. What is the plan or the sides and back?
Are you going to paint them? If so, make sure to seal off the mdf ends before painting. Easiest way is probably buy adding a thin layer of wood-glue (maybe thinned with some water) before base coat.

Thanks - yes - just painting. I've ended up using some chemical setting filler (pink stuff) as I made a few mistakes ;-).

In the past I've just applied several undercoat layers and sanded until smooth and non-porous.

[sdl2112]

I'm glad to see you making progress. They are looking very good. A unique shape that has function and pleasing to the eye.

[Dave Bullet]

There be more progress! I better order the final crossover parts (getting close!). Undercoat on

[Dave Bullet]

Nearly there. Final XO parts have been ordered. Cabinet complete apart from XO wire up and installation. Foam seal on the driver recesses and installation of the binding posts at the back

[sdl2112]

They turned out great Dave. Your long journey and dedication has really payed off. I look forward seeing you crossovers too!

[Dave Bullet]

They turned out great Dave. Your long journey and dedication has really payed off. I look forward seeing you crossovers too!

Thanks. They won't be as professional as yours. I sprung for Clarity CSA caps in series for the tweeter, but everything else is more budget. Whatever Madisound stocked for a reasonable price. I could try and get cheaper shipping elsewhere I suppose, but Madisound provide good service. I have gone a bit overkill on notch filters and the like the deaden the L15 and L26 breakups. Also gone steep on the tweeter which I think pays off as you turn up the volume.

[Dave Bullet]

Here's the exciting picture of the crossover boards and where they will mount (rear wall). In 2 pieces so they easily fit through the woofer hole.