choice of drivers - 15" + compression driver + waveguide

ScottG

Member
2003-02-04 12:23 am
US
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.)
 
Last edited:

audiothings

Member
2005-08-21 7:17 pm
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...
 
Last edited:
... 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.
 
- 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.

finishedosguides3.jpg
 

Attachments

  • 2426h impedance correction.JPG
    2426h impedance correction.JPG
    17.2 KB · Views: 181
Last edited:

ScottG

Member
2003-02-04 12:23 am
US
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.)
 

audiothings

Member
2005-08-21 7:17 pm
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.
 

Sangram

Moderator
Paid Member
2002-09-25 11:01 am
India
http://profesional.beyma.com/ingles/pdf/15XA38Nd.pdf

I'm working on a design using this driver and a Selenium 15SW800. Project ambition is to create a product that will do 120dB/1m so it can fill huge rooms.

The Selenium in a sim will do 114dB at 35Hz per box (-10dB) with 400W, so 120dB seems achievable in a stereo pair. Planning crossover at 120-150Hz to the Beyma and then onwards at 700Hz to the coaxial.

I'm aware of the issues with moving waveguides (which I hope is somewhat ameliorated by the Beyma not handling any lower bass at all), but also wanted a compact design for higher WAF as it's a consumer product.

The trouble (personally speaking) getting the correct amount of power to the drivers and ensuring they stay within parameters, specially in a one-box solution.
 

doug20

Member
2009-03-22 9:38 pm
http://profesional.beyma.com/ingles/pdf/15XA38Nd.pdf

I'm working on a design using this driver and a Selenium 15SW800. Project ambition is to create a product that will do 120dB/1m so it can fill huge rooms.

The Selenium in a sim will do 114dB at 35Hz per box (-10dB) with 400W, so 120dB seems achievable in a stereo pair. Planning crossover at 120-150Hz to the Beyma and then onwards at 700Hz to the coaxial.

I'm aware of the issues with moving waveguides (which I hope is somewhat ameliorated by the Beyma not handling any lower bass at all), but also wanted a compact design for higher WAF as it's a consumer product.

The trouble (personally speaking) getting the correct amount of power to the drivers and ensuring they stay within parameters, specially in a one-box solution.


JTR 12" designs and Seaton Catalysts come to mind when you talk about high sensitivity, high SPL designs with Coaxial drivers in the consumer market.

Are you going to be competing against those two?? I have heard the JTRs they kick some major A$$ and the Seaton Catalysts are even a bigger step up in quality because they are full active and customized for each room.
 

Sangram

Moderator
Paid Member
2002-09-25 11:01 am
India
No, neither. This is a product that we will probably only offer to Indian customers and that too only to a very small number of people who actually have a room that demands such big speakers.

I consult with a company that is in the business and has Indian distributorship for some brands, and those will take precedence over house products unless drastic changes happen.

Anyway these will be fully active too with about 600 watts of amplification per channel though we won't be using any room correction as of now. We would look at a future integration with Spatial Computer for customisation (we are already well connected with Emerald Physics) and room correction.
 
I would go for B&C DE250 + TD15M + woofer or sub.

I have the B&C and with my prototype, it sounds excellent. It's one of the better regarded units, and in a blind test against a much more expensive TAD performed by Geddes, it was not found to be inferior.

TD15M has higher efficiency and the accordian surround is better than a half roll surround for midrange.

Much better to choose a driver for it's midrange and use dedicated bass drivers. It's often an advantage to overlap the bass and put bass sources where they work best.

Why give up all the efficiency to try to get one driver do mids and deep extension? You can get down deep enough with the TD15M in a vented box, then add some subs if you want more extension. I also find it's better to have active bass separate so you can set the level as desired.
 
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.

finishedosguides3.jpg

Badman I know this is an old post but I was wondering if you could post some details on your speakers. I am considering something similar here and could use some input.