Constraints
I wanted to run curves on each, it would have been a piece of cake, but the wife wouldn't have it. I'll give you a response variation making one sounding "better," but they were pretty darn close. Qtc was 0.6 empty, but I added fiberfill bundled in cheesecloth for something between 0.5 and 0.6. Used factory TS parameters and neglected the BR Ql as 7. I did break them in. So yes, there was ripple in the BR, I couldn't call it aligned with a straight face.
But the subjective result remains - despite lining the ported box on 3 inside walls, facing the port to the rear, and hanging a curtain on the wall behind the test boxes, there were affects above the bottom couple octaves, specifically in mixes of percussive notes like piano or plucked strings on top of extended notes. It seems this is more of an intermodulation or phase issue than frequency response.
These drivers are going in a center channel speaker with bohlender graebener mids and a heil AMT - - I would really like to have that extra octave of bass but I'm concerned any phase or IM will stick out. The few TLs I've done seemed like the best of both worlds. My next challenge is to cram two TLs into the volume behind my test baffle and leave some space for the mids and the crossover. I can't tear out the wall behind it, it's brick!
I wanted to run curves on each, it would have been a piece of cake, but the wife wouldn't have it. I'll give you a response variation making one sounding "better," but they were pretty darn close. Qtc was 0.6 empty, but I added fiberfill bundled in cheesecloth for something between 0.5 and 0.6. Used factory TS parameters and neglected the BR Ql as 7. I did break them in. So yes, there was ripple in the BR, I couldn't call it aligned with a straight face.
But the subjective result remains - despite lining the ported box on 3 inside walls, facing the port to the rear, and hanging a curtain on the wall behind the test boxes, there were affects above the bottom couple octaves, specifically in mixes of percussive notes like piano or plucked strings on top of extended notes. It seems this is more of an intermodulation or phase issue than frequency response.
These drivers are going in a center channel speaker with bohlender graebener mids and a heil AMT - - I would really like to have that extra octave of bass but I'm concerned any phase or IM will stick out. The few TLs I've done seemed like the best of both worlds. My next challenge is to cram two TLs into the volume behind my test baffle and leave some space for the mids and the crossover. I can't tear out the wall behind it, it's brick!
Attachments
You know what I should have done for the theme of this thread? Whacked together a standard TL, but I didn't have enough scrap wood and the Wf factor would have zeroed out. How about it, guys? Does anyone have three or more identical mid woofers and a man-cave to put together temporary sealed, ported and TL enclosures for each? If you have time, maybe for the sealed one try for Qtc below 0.707, for the vented measure the driver and adjust the alignment at least once, and for the TL adjust the fill for flatest impedance. Then just test them - square waves, tone burst, distortion, Holm Impulse, and of course the bass F3.
I think bass ports only sound good if tuned around or below 30hz, in a largish box, higher tunings and small boxes just sound rubbish with ports. and usally higher tunings means the woofers unload easly when you get a lower frequency threw the speakers, they flap about and mess things up. lower tunings, dont seem to suffer from this problem.
I think this is due to the kick of ports being useless, but for low notes there fine. so with a low tuned port the kick 40-70hz is comming mostly from the driver, and the low resounding bass is coming from the port.
Just hope a woofer can do both, for example when a note playes a resounding 30hz note and the port tuning where driver excursion is minimal, it is like the driver and port are locked into some push pull, tug of war , would a kick drum at this point be able to break the coupling for a moment and still kick right whilst letting that note at 30hz still play?
like the air in the box is literally forcing the driver to move less. so if it is ordered by the amp to play a 50hz kick at the same time, how does the poor woofer cope? when its magnetic force is being over taken my controll from the port?
will have to observe cone motion when i test my new speakers, and hear for my self. then i can do a sealed v ported by stuffing the ports. but with ports stuffed the woofer moves more, whick confuses me and makes me contemplate the above question....
I think this is due to the kick of ports being useless, but for low notes there fine. so with a low tuned port the kick 40-70hz is comming mostly from the driver, and the low resounding bass is coming from the port.
Just hope a woofer can do both, for example when a note playes a resounding 30hz note and the port tuning where driver excursion is minimal, it is like the driver and port are locked into some push pull, tug of war , would a kick drum at this point be able to break the coupling for a moment and still kick right whilst letting that note at 30hz still play?
like the air in the box is literally forcing the driver to move less. so if it is ordered by the amp to play a 50hz kick at the same time, how does the poor woofer cope? when its magnetic force is being over taken my controll from the port?
will have to observe cone motion when i test my new speakers, and hear for my self. then i can do a sealed v ported by stuffing the ports. but with ports stuffed the woofer moves more, whick confuses me and makes me contemplate the above question....
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That is the case though. At the vent frequency the vent does the work and cone motion reduces greatly. As long as your program material is in the high pass of the system, the woofer excursion is lower with the vented system than twhe sealed system.
Don't worry about the woofer being expected to follow various notes at the same time. That is just another way of saying the input waveform can be complex and it makes no particular difference to the woofer, as long as the various frequencies fall under the maximum excursion profile (vs. frequency) of the system.
David S.
Why not build a bass-reflex and tune it really low?
About 25Hz?
I like to use slotted ports for this.
You have some low end bass and not a lot of excursion.
With room gain, it can sound almost flat.
Actually I don't like flat FR in the top or the bottom.
Well I like a ton of bass, but it's hard to achieve and have it sound good.
For BR you need a professional woofer with stiff suspension and strong magnet and large cone area and also large box.
About 25Hz?
I like to use slotted ports for this.
You have some low end bass and not a lot of excursion.
With room gain, it can sound almost flat.
Actually I don't like flat FR in the top or the bottom.
Well I like a ton of bass, but it's hard to achieve and have it sound good.
For BR you need a professional woofer with stiff suspension and strong magnet and large cone area and also large box.
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