Search found 66 matches

by MJK
Thu Nov 22, 2018 1:26 am
Forum: Speakers
Topic: Another PAP inspired OB job
Replies: 31
Views: 21710

Re: Another PAP inspired OB job

If you have the driver T/S parameters then it will only take an hour or two of playing to get some decent results. It is not that hard, just jump in. It is free, what have you got to loose other than a little time. Faster and cheaper than trial and error building.
by MJK
Wed Nov 21, 2018 1:19 am
Forum: Speakers
Topic: Another PAP inspired OB job
Replies: 31
Views: 21710

Re: Another PAP inspired OB job

Simulate the different 15" woofers (high and low Qts) in the baffle you have in mind with either a passive or active crossover in BASTA and see what you get. No guessing or assuming, you design the speaker to meet you goals and select the driver that works best. No "experts" needed. h...
by MJK
Mon Nov 06, 2017 11:59 am
Forum: Speakers
Topic: MY own OB speaker project
Replies: 95
Views: 76428

Re: MY own OB speaker project

The low fs and relatively low Qts of the 15" woofers being used is going to make it difficult to get a flat extended bass response. The baffle is rolling off the low end below 100-200 Hz at 6 dB/octave combining with the woofer rolling off due to the Qts, the lower you go in frequency the more ...
by MJK
Sun Jul 02, 2017 2:58 pm
Forum: Speakers
Topic: OB with Alpair 12P and Eminence Beta 15
Replies: 99
Views: 81078

Re: OB with Alpair 12P and Eminence Beta 15

OK, your plots make sense now. Looking at your final plot, which produces the deepest bass output, you are using two Beta 15A woofers with a lower crossover point producing about 95 dB/2.83 V/m down to about 50 Hz. I have a very similar simulation that produces a little more output (96 dB/2.83 V/m) ...
by MJK
Fri Jun 30, 2017 1:36 am
Forum: Speakers
Topic: OB with Alpair 12P and Eminence Beta 15
Replies: 99
Views: 81078

Re: OB with Alpair 12P and Eminence Beta 15

Over the past two evenings I exercised my latest MathCad worksheets for the Alpair 12P combined with one or two Alpha 15A or Beta 15A woofers. For two woofers I looked at a parallel connection for the Alpha 15A's and a series connection for the Beta 15A's. There are definitely workable solutions wit...
by MJK
Thu Jun 29, 2017 12:12 am
Forum: Speakers
Topic: OB with Alpair 12P and Eminence Beta 15
Replies: 99
Views: 81078

Re: OB with Alpair 12P and Eminence Beta 15

I don't think changing a passive low pass filter in the 200 to 400 Hz will have that big of an impact on the shape of the low frequency roll-off. Looks like a modeling error to me.
by MJK
Wed Jun 28, 2017 11:53 am
Forum: Speakers
Topic: OB with Alpair 12P and Eminence Beta 15
Replies: 99
Views: 81078

Re: OB with Alpair 12P and Eminence Beta 15

The software does not account for cone break up, it assumes a rigid piston motion for the cone.
by MJK
Wed Jun 28, 2017 1:39 am
Forum: Speakers
Topic: OB with Alpair 12P and Eminence Beta 15
Replies: 99
Views: 81078

Re: OB with Alpair 12P and Eminence Beta 15

Something does not look right. I would have expected the series and parallel connected woofers to have essentially the same shape for the SPL frequency response curves but just at different output levels, the parallel connection producing +6 dB more output for the same input voltage. Seeing the sign...
by MJK
Sun May 28, 2017 7:40 pm
Forum: Speakers
Topic: OB with Alpair 12P and Eminence Beta 15
Replies: 99
Views: 81078

Re: OB with Alpair 12P and Eminence Beta 15

There is no magic in a series crossover. I have modeled many series and parallel crossovers and the parallel crossover has always given excellent results. Smooth linear SPL response both for magnitude and phase. Measurements have confirmed the modeled results. Once you have the baffles built and the...
by MJK
Sun May 28, 2017 5:34 pm
Forum: Speakers
Topic: OB with Alpair 12P and Eminence Beta 15
Replies: 99
Views: 81078

Re: OB with Alpair 12P and Eminence Beta 15

I do not see options in BASTA to do a passive series crossover or to convert the frequency domain response into the time domain.
by MJK
Thu May 18, 2017 12:58 am
Forum: Speakers
Topic: OB with Alpair 12P and Eminence Beta 15
Replies: 99
Views: 81078

Re: OB with Alpair 12P and Eminence Beta 15

Try the BASTA program to simulate OB speakers.

http://www.tolvan.com/index.php?page=/basta/basta.php

It is free, easy to use, and will handle baffle size, shape, driver placement, and passive or active crossovers.
by MJK
Fri Apr 14, 2017 6:21 pm
Forum: Speakers
Topic: Open Baffle Project
Replies: 47
Views: 28743

Re: Open Baffle Project

Martin, I'm currently using one of your OB designs - B200 and twin Alphas per side. I'm looking for a bit more detail in the bass. Would It be a good idea to go for Betas, or would you have another suggestion? I have never used the Beta 15A woofers so I can't provide an absolute answer. People seem...
by MJK
Fri Apr 14, 2017 5:25 pm
Forum: Speakers
Topic: Open Baffle Project
Replies: 47
Views: 28743

Re: Open Baffle Project

I would recommend two 15" Eminence drivers per side (Alpha 15A or Beta 15A depending on your bass needs/preferences) to better match the efficient Fostex FE-167E. I would also recommend simulating your design using the free BASTA program from Tolvan research to get a better idea of the response...
by MJK
Fri Apr 07, 2017 2:05 am
Forum: Speakers
Topic: A Question of Right and Wrong.
Replies: 95
Views: 52455

Re: A Question of Right and Wrong.

They are all wrong. If one speaker system got it exactly right we would all be able to hear and tell it was the best, we would all be listening to it in own homes, none of these debates would take place, and the forums would go silent. Speakers at best try and provide an illusion of real music, and ...
by MJK
Mon Dec 05, 2016 7:41 pm
Forum: Speakers
Topic: Something stirs in the Undergrowth
Replies: 2802
Views: 1147650

Re: Something stirs in the Undergrowth

Is what you have designed a horn or a TL? You need to answer this question to plan your path forward. If the mouth is too small for it to behave as a horn you are probably getting TL standing waves and a ragged SPL response, stuffing with fiber may help. If it is a TL then the bends probably do not ...