2-Way open baffle/baffless?

[rich31td]

I am designing a small 2-way dipole speaker for use on a desk.

I plan on mounting an 8" inch driver (Seas L22RNXP) on an open baffle measuring 330mm/400mm and a 3" wide band driver (Fostex FE83En) in a baffless configuration.

I have simulated this in "The Edge" measuring off axis at 15degrees.

The first dipole peak for the 8" woofer ends at around 1500hz which is where the first peak starts for the 3" wide band driver.

I could set crossover here but am under the impresion this is a bit high to run an aluminum cone driver of this size?

So I am going to set the crossover in the middle of the woofers first dipole peak at 700hz and notch both dipole peaks and low shelf the wide band driver which is 5db down at the x-over point. I am using a MiniDSP which makes this fairly easy. The HF starts to roll off around 7K and I will have to low shelf the woofer quite a bit as well.

Bellow is a screenshot of the plot in "The Edge".

Am I along the right line with this idea?


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[Rudolf]

Originally Posted by rich31td

So I am going to set the crossover in the middle of the woofers first dipole peak at 700hz and notch both dipole peaks and low shelf the wide band driver which is 5db down at the x-over point. I am using a MiniDSP which makes this fairly easy. The HF starts to roll off around 7K and I will have to low shelf the woofer quite a bit as well.

Bellow is a screenshot of the plot in "The Edge".

Am I along the right line with this idea?

Edge is only giving you the response of the baffles, nothing of the drivers. Be prepared to find the dipole peak of the FE83 more "peaky" than Edge suggests. You don't notch the dipole peak of the woofer. Decide the frequency were you want the bass to become linear/horizontal, and put a 6 dB low pass filter there. The frequency of the woofer dipole peak will now become the start of the "real" acoustic low pass slope of the woofer. Join the FE83 at that frequency. You will need to add a high pass filter there to keep the FE83 from bass frequencies. If you are lucky, you can notch the dipole peak of the FE83 with the same filter too.

[adason]

I think you would be better off by putting that 8" in small closed box and make an open baffle on top with little fulrange
than optimize crossover according to the fr response with holm impulse
this way you may end up with compact good looking speaker with decent sound
in comparison to the ugly monster with no bass and peaky response
just my opinion

[rich31td]

That makes sense, I have ARTA installed an a microphone ready to measure.

I have read your document on Baffles, very interseting and informative.

Am I on the right track with this then?

[gainphile]

The dipole peaks are less relevant when you listen nearfield

I have something similar and love it!

[rich31td]

Have now decided not to use them nearfield but instead as floorstanders, a bit like Gainphiles speakers.

I have ordered a Tangband W2-800SL 2" driver which I will use baffle-less and the Seas L22RNX/P is mounted on 22mm pine board 290mm/875mm, I have allready cut them to size and used a roundover bit on the front and back edges. Here is the edge plot.

[Rudolf]

Originally Posted by rich31td

I have ordered a Tangband W2-800SL 2" driver which I will use baffle-less

I have tested a clone of the Tangband (steel basket instead of ABS, everything else equal), and it is not usable without a baffle. You will get a VERY strange on axis response. No hope to fix that.

Rudolf

[rich31td]

Ah, okay, in that case I shall make a small baffle, round or square and no larger than twice the cone diameter. That also means it will require less eq'ing to achive a lower x-over.

[adason]

so...where is the result? pics?

[rich31td]

havn't got any further, it is snowing outside so will have to wait for it to warm up a bit. Need to use the router to flush mount the seas driver and that is it.

Will post pics when done.