H-Frame Design for Delta-15LFA

[thunk303]

Hello all.

Purchasing woofers for my OB project is the last step in this year long build. The idea is to have the woofers in a H-Frame with the mid/tweeter in a frame swinging nude above it.
But as usual, I have no idea how to design one so would appreciate any advice on this. I am happy to go as large as possible but really the WAF will be a limiting factor.

Is there a program for designing H-Frames?
Has anybody already done the hard work and wants to share the dimensions?
Are there any simple rules of thumb to remember.

The setup is all active using 6 x LM4780's and mini-DSP's. The amp is almost finished and the mids/tweeter are ready to go.

Cost has been limited to around AU170 per woofer and local availability.

Eminence Delta-15LFA
http://www.eminence.com/pdf/delta-15lfa.pdf
Essential Audio - Loudspeaker Kits, Hi-Fi Loudspeakers, Guitar, Bass & PA Loudspeakers! Eminence, Celestion, Jensen, Scan Speak, Vifa, Peerless, SB Acoustics, Fountek

These seem to be a safe/well used choice for the price. I have chosen the LFA because I don't need the extended HF output and they have a little more XMAX over the standard D-15.

Woofer sensitivity will be around 10dB higher than my mid/HF combo which should allow plenty of room for EQ'ing.

Cheers
Dean

PS. The link to the site of sale doesn't work as intended.... Sorry.

[Jim Griffin]

Dean meet Martin J. King.

Quarter Wavelength Loudspeaker Design

Originally Posted by thunk303

Hello all.

Purchasing woofers for my OB project is the last step in this year long build. The idea is to have the woofers in a H-Frame with the mid/tweeter in a frame swinging nude above it.
But as usual, I have no idea how to design one so would appreciate any advice on this. I am happy to go as large as possible but really the WAF will be a limiting factor.

Is there a program for designing H-Frames?
Has anybody already done the hard work and wants to share the dimensions?
Are there any simple rules of thumb to remember.

The setup is all active using 6 x LM4780's and mini-DSP's. The amp is almost finished and the mids/tweeter are ready to go.

Cost has been limited to around AU170 per woofer and local availability.

Eminence Delta-15LFA
http://www.eminence.com/pdf/delta-15lfa.pdf
Essential Audio - Loudspeaker Kits, Hi-Fi Loudspeakers, Guitar, Bass & PA Loudspeakers! Eminence, Celestion, Jensen, Scan Speak, Vifa, Peerless, SB Acoustics, Fountek

These seem to be a safe/well used choice for the price. I have chosen the LFA because I don't need the extended HF output and they have a little more XMAX over the standard D-15.

Woofer sensitivity will be around 10dB higher than my mid/HF combo which should allow plenty of room for EQ'ing.

Cheers
Dean

PS. The link to the site of sale doesn't work as intended.... Sorry.

[natehansen66]

The LFAs are great on OB with active filters........I'm running 2 right now. Real similar deal, only mine are in "open" U-frames that are about 6-7" deep. They're angled so the depth gets smaller to the top. On top I've got a "nude swingin'" 3-way panel, all xo'd and filtered by 2 miniDSPs. Killer setup! Gonna make a post about them one of these days..........

Anyways, use the various calcs that are available online to figure out the dimensions. Martin's that was posted above is good but not free. John K has an excellent one available I think for free on Music and Design.

I'm getting solid output with my u-frames down to the high 30's (with a good bit of eq)........perfect for music. I low pass them at 275 to an 8" vifa woofer.

[thunk303]

Great to hear somebody is on the same path.

I have 2 Peerless 850439 running in push/pull as mids, not great but all I have for now. And the XT25TG-30-4 with the back cup removed.

Thanks for the links, I have the MJK H-Baffle Math Cad sheet open, but just cant make sense of the input fields. a step by step guide may be needed.
Checking the other links as we speak.

Did you end up using REW with a mic for your setup Nate?

Any setup advice you have sounds like it could be very helpful, since we are following such similar paths.

What was your main reason for choosing the D15's over other woofers??

Cheers
Dean

[thunk303]

Does anybody know the exact location of the specific software on the Music and Design site?

Dean

[thunk303]

Ooops, found it at the top of the page

A, B, C, Dipole

[john k...]

Martin's worksheets are considerable more complex that the ABC dipole H and U frame tools. In ABC dipole the H and U frame calculations are just to be used as a guide to assess the low frequency performance of the configuration. They do not consider cavity resonances of the additional air mass load on the driver. For woofers with high moving mass (such as the Peerless XLS and XXLS woofer) the added mass load is insignificant. But for lower moving mass woofers the added mass load can have an effect on the driver parameters.

As indicated in the written part of the guide, you really need to build the H or U and then measure the response and then design the crossover filters/eq based on the measured results.

[thunk303]

Cheers for the input John.

It sounds like that will work out well, I have all the measurement gear ready to go, so its just a matter of getting the woofers and building the H frames.

This will be my first decent system in 2 years. But the potential for tuning it to any room with any XO should keep me happy for a while

Dean

[john k...]

Originally Posted by thunk303

Cheers for the input John.

It sounds like that will work out well, I have all the measurement gear ready to go, so its just a matter of getting the woofers and building the H frames.

This will be my first decent system in 2 years. But the potential for tuning it to any room with any XO should keep me happy for a while

Dean

If you download my guide just follow the procedure outlined under the Designing a Dipole Speaker, The Woofer System, H frame woofer design. I don't really address Qts>1 and I'm only addressing active EQ, but you can generate the active eq transfer function, LP filter and then you will have a good idea of the "shape" of the transfer function you need if you go passive on the woofer.

[natehansen66]

Originally Posted by thunk303

Did you end up using REW with a mic for your setup Nate?

What was your main reason for choosing the D15's over other woofers??

Cheers
Dean

Yep, I'm using REW. Until a couple days ago I was using a RadShack spl meter.......got a decent mic put together so now I can get serious

Prior to the LFAs, I had some cheap high qts 15s.........the bass was flabby and they didn't play into the midrange very well. I thought these looked like a good choice, given that I was going active.....so far they haven't disappointed! It was either the Delta's or the EMI 1550s from Madisound. I ended up going with the Deltas, as the 1550s are labeled as subwoofers and I was doubtful they could go up into the midrange very cleanly. This guy thinks otherwise!: The "Audiosyncrasy". If I did it again, I'd get the 1550s.