choice of drivers - 15" + compression driver + waveguide

[audiothings]

I am planning to build a two way loudspeaker with the AE speakers Lambada series TD15H as woofer and a JBL 2426H with an Azurahorn AH-550 for the high frequencies. I aim to crossover @ 1KHz.

As I am very new to this, I seek your opinion on the driver selection... would something else be recommended at around the same price point?

[454Casull]

Depends. Are you looking for a customized solution or you just don't want to buy a turnkey system?

[ScottG]

At a 1 kHz crossover the JBL is rather costly. Also because it's titanium with a titanium surround, they tend to sound a bit more "bright" and a little "clearer".. which *can* make matching with a midrange a bit more difficult.

The rubber surround of the AE driver might have a trailing resonance lower in freq. (and higher in amplitude) than one of their drivesr with a pleated fabric surround.


For that kind of money I'd suggest the 18 Sound 1460A and either the AH-425 or the 18 Sound XT1464, while ALSO lowering the crossover point. (..Horn differences: they have different directivity patterns and the AH-425 can be used even lower in freq. or with a less steep filter. With the AH-425 you might want a super tweeter, with the XT1464 probably not.)

Here is Paul W's Raptor that uses both 18 Sound driver and horn:

HTGuide Forum - The Raptor ... a 10" MTM

Note that the response becomes much more uniform off-axis once he lowers the crossover for the driver and horn. (..Horizontal plots on post 21 and post 26 of that thread.)

[audiothings]

Originally Posted by 454Casull

Depends. Are you looking for a customized solution or you just don't want to buy a turnkey system?

By "turnkey system" do you mean a fully built system or a parts kit? If it is the latter, may I have a link...

I am in India and getting a fully built system would be cost prohibitive... besides, I will use an external digital loudspeaker manager, giving me some flexibility with the crossovers and also the scope to tune to the room.

The rubber surround of the AE driver might have a trailing resonance lower in freq. (and higher in amplitude) than one of their drivesr with a pleated fabric surround.

That would be the TD15M. Has the problem been noted specifically with the speaker I pointed to or is it endemic yo all speakers with a rubber surround? What exactly does the problem sound like, please? The model I pointed to has a much lower Fs and an lower end extension of almost 15 Hz below the model TD15M, and I am looking for as much extension as I can get, into the lowest octave ...

For that kind of money I'd suggest the 18 Sound 1460A and either the AH-425 or the 18 Sound XT1464, while ALSO lowering the crossover point.

Thank you for the suggestion, looking into it now...

[head_unit]

Originally Posted by audiothings

... I am looking for as much extension as I can get, into the lowest octave ...

- Just be sure to look at the -6 and -10 dB points, which are more relevant to the REAL low frequency cutoff in a room. - 3 dB is not too meaningful, it was just a mathematical convenience. A more slowly reducing output (which can mean a higher -3 dB point, but lower -6 and -10) often works better in real rooms.

- Note that many pro woofers' parameters seem to indicate sealed boxes smaller than the cone volume, and ported designs which seem nuts. This is because they are designed to work at high SPL, meaning high continuous power input, meaning the voice coils constantly hot (i.e. like in a 24/7/365 German disco, or a rock concert). When the coils are hot, the parameters shift and work in the big boxes the woofers go in. But at home levels, yeah, ya gotta work with the low level parameters given, so many pro woofers may not work so well.

- Digital crossover can give you a lot of flexibility, and active amplification is really good for horns since their impedance can be messy making passive crossovers difficult. Try to get a constant directivity horn. Most horns "beam" to keep on-axis response flat, but going active means you can EQ the on-axis no problem. Also the woofer should have a smooth response. Not necessarily flat-gentle bumps can be EQd out. But ugly bumps or dips won't really EQ out so well, regardless of calculations on paper.

[badman]

Originally Posted by head_unit

- Just be sure to look at the -6 and -10 dB points, which are more relevant to the REAL low frequency cutoff in a room. - 3 dB is not too meaningful, it was just a mathematical convenience. A more slowly reducing output (which can mean a higher -3 dB point, but lower -6 and -10) often works better in real rooms.

- Note that many pro woofers' parameters seem to indicate sealed boxes smaller than the cone volume, and ported designs which seem nuts. This is because they are designed to work at high SPL, meaning high continuous power input, meaning the voice coils constantly hot (i.e. like in a 24/7/365 German disco, or a rock concert). When the coils are hot, the parameters shift and work in the big boxes the woofers go in. But at home levels, yeah, ya gotta work with the low level parameters given, so many pro woofers may not work so well.

- Digital crossover can give you a lot of flexibility, and active amplification is really good for horns since their impedance can be messy making passive crossovers difficult. Try to get a constant directivity horn. Most horns "beam" to keep on-axis response flat, but going active means you can EQ the on-axis no problem. Also the woofer should have a smooth response. Not necessarily flat-gentle bumps can be EQd out. But ugly bumps or dips won't really EQ out so well, regardless of calculations on paper.

Agree with everything you said. My own 2 way uses JBL 2226h 15" and a diy Oblate spheroid waveguide with the 2426h. I had to use quite a bit of impedance compensation per below to get the 2426h smooth sounding.

[John Sheerin]

I'd try the JBL 2435 with an appropriate horn if you can find some used for reasonable prices.

[ScottG]

Originally Posted by audiothings

That would be the TD15M. Has the problem been noted specifically with the speaker I pointed to or is it endemic yo all speakers with a rubber surround? What exactly does the problem sound like, please? The model I pointed to has a much lower Fs and an lower end extension of almost 15 Hz below the model TD15M, and I am looking for as much extension as I can get, into the lowest octave ...

You can look at some of the measurements of AE 15" drivers (and other driver's) linear decay from their CSD plots (under the "freq.") section here (courtesy of Augerpro):
15" - drivervault

That ridge of delayed energy at 1.6 kHz is likely due to interaction with the surround.

The smaller 12M you can find here:
12" - drivervault

Consider a bass reflex design for high amplitude at lower freq.s. (vent or passive radiator), or a transmission line. (..or a combination like Martin J. King likes to do.)

[Flaesh]

http://www.eighteensound.it/staticCo...ound_kit15.pdf
xover freq. seems too high for home using (?..)

[audiothings]

Thanks to all.

That ridge of delayed energy at 1.6 kHz is likely due to interaction with the surround.

Will this affect us even if the crossover is 24 dB at 800 Hz? Is it a mechanical problem that will create some kind of resonance around 1.6 KHz regardless of the frequencies being played back?

I had to use quite a bit of impedance compensation per below to get the 2426h smooth sounding.

How/can impedance matching be accomplished digitally, through a loudspeaker management processor? And how do they perform now, with the compensation circuit?

- Note that many pro woofers' parameters seem to indicate sealed boxes smaller than the cone volume, and ported designs which seem nuts. This is because they are designed to work at high SPL, meaning high continuous power input, meaning the voice coils constantly hot (i.e. like in a 24/7/365 German disco, or a rock concert). When the coils are hot, the parameters shift and work in the big boxes the woofers go in. But at home levels, yeah, ya gotta work with the low level parameters given, so many pro woofers may not work so well.

Is this true of the TD15 specifically?

Thanks again.