8" midbass dilemma

[edouble101 314]

I am in the process of redoing my front stage. It will be an active three way. My head unit is a Pioneer DEX-P99RS and my amplifier for my front stage is an Arc Audio KS900.6. My goals for my front stage is to have excellent mid bass and to create a realistic soundstage with excellent imaging.

To kick of my install I started with the midbass. I currently have a Viper 650.2 component set (running active) installed for midrange/tweeter duties. I will be replacing the Viper set. My midbass install consists of Dayton Audio RS225-4 drivers mounted in very tiny (.2-.3^3ft) sealed enclosures with ScanSpeak flow resistors. The ScanSpeak flow resistors are AP mats about 4" in diameter. I made a huge design error with making the enclosures this small. I have always read to make enclosures as small as possible when using AP mats, well that isn't true.

My xover points for the RS225-4 are 50hz@24db and 400hz@12db. I will be using Dayton Audio RS100T-8 midrange drivers mounted in the a-pillars.

In this picture you you can see the AP mats behind the enclosure baffle.

Here is another in-process picture of the 8" RS225-4 install.

I stuffed the enclosures with poly fill and made under dash covers. My dash is also stuffed with poly fill and I have CLD tiles/CCF/MLV on the floor and enclosures. My frequency response after the install was pretty horrible.

With a lot of equalizer adjustments I was able to smooth out the fr a bit.

After all of the install work I am still very disappointed with my midbass response. There is no real "kick" or any impact from the midbass. My pant legs vibrate a little from the 8"s but it is no where near what it should be. The sound "muddy" and not very "fast". I have been searching for a better 8" midbass driver for my install. I am not willing to tear out my enclosures. I could very well take out the AP mats and run IB in this setup.

What I am asking is what driver would be more suited for my install? I can keep the AP mats or run IB. I want to keep my midbass crossed at 50&400hz.

[Impious 1,476]

A few potential problems I see.

First, where does the AP mat vent to? It should vent into a large open area, just the same as IB. It looks like it simply vents into the floor of the car, which would be far less than ideal and cause it not to function properly.

Second, AP isn't as simple as using a predesigned mat/vent, such as that Scanspeak piece. The amount of resistance provided by the AP mat needs to be "tuned" to the loudspeaker just like any other enclosure. The goal of AP is to flatten the impedance peak, and the thickness/resistance of the mat needs to be designed specifically for the driver and it's particular impedance peak.

Last, I personally think you have insufficient AP mat area. That AP mat you have is designed to be used with smaller diameter drivers.

Also, what was the reason for going AP? What were you hoping to gain?

I think your driver selection is probably fine. I think the problem is the implementation of the AP.

[ssh 924]

A few potential problems I see.

First, where does the AP mat vent to? It should vent into a large open area, just the same as IB. It looks like it simply vents into the floor of the car, which would be far less than ideal and cause it not to function properly.

Second, AP isn't as simple as using a predesigned mat/vent, such as that Scanspeak piece. The amount of resistance provided by the AP mat needs to be "tuned" to the loudspeaker just like any other enclosure. The goal of AP is to flatten the impedance peak, and the thickness/resistance of the mat needs to be designed specifically for the driver and it's particular impedance peak.

Last, I personally think you have insufficient AP mat area. That AP mat you have is designed to be used with smaller diameter drivers.

Also, what was the reason for going AP? What were you hoping to gain?

I think your driver selection is probably fine. I think the problem is the implementation of the AP.

The APs vent out into the fenderwell.

Edited June 29, 2012 by stefanhinote

[lithium 358]

thought that was his install. not to hijack but what would be the advantage of ap over ib?

[ssh 924]

thought that was his install. not to hijack but what would be the advantage of ap over ib?

IIRC they act as a larger sealed enclosure, which can be beneficial in this case when you want more volume, but are restricted to the kick panel area.

[///M5 2,833]

Agree on all points so far, except one. The RS225 is not much of a midbass driver and has great upper midrange for an 8, but is seriously lacking in midbass. For a 3 way it doesn't make a whole lot of sense. I was a bit disappointed when I unboxed mine as well, but bought them for a 2 way which they did pretty well. As for what midbass to run, that'll depend on your mids. Typically midbasses that perform well in your scenario fall flat on their face above 200-300Hz as it generally is best to use a sub if you are looking for the impact that it sounds you are. Of course at those frequencies there is no need to have them as on axis as your install either so if you did rebuild you could save a lot of space.

That being said, what is the rest of the install? I would always first focus on the majority of the audio spectrum and then make the rest blend and match. That portion you havent' shared.

[95Honda 486]

Any idea what volume the enclosures are? I would try and seal up the Aperiodic vent and stuffing the box. It would have a high Q, but may get you the sound you are looking for...

I only make this suggestion as the high system Q and ripple in response may help the region you feel you are lacking in...

I have used the Variovent in the past. But not for at least 10 years. The advantages never seemed to outweigh the cost of them considering I never had a box that was too small or an usable impedance peak. I also built a few Aperiodic boxes with 3/8" holes drilled in the rear baffle. I never got the results people talked about in places like Speaker Builder and Audio Ametuer. I could also hear air chuffing when I was near-field

[edouble101 314]

A few potential problems I see.

First, where does the AP mat vent to? It should vent into a large open area, just the same as IB. It looks like it simply vents into the floor of the car, which would be far less than ideal and cause it not to function properly.

Stefanhinote posted pictures of my install. They AP are venting to the outside of the vehicle.

Second, AP isn't as simple as using a predesigned mat/vent, such as that Scanspeak piece. The amount of resistance provided by the AP mat needs to be "tuned" to the loudspeaker just like any other enclosure. The goal of AP is to flatten the impedance peak, and the thickness/resistance of the mat needs to be designed specifically for the driver and it's particular impedance peak.

The only instructions ScanSpeak has for these is to add more of them for larger drivers. The use the rule to divide the driver size in a half for each flow resistor. My midbass is 8" and the flow resistors are 4". My install was not thoroughly thought out and my composure volume is indeed too small. At this point I am trying to sacrifice my install.

Last, I personally think you have insufficient AP mat area. That AP mat you have is designed to be used with smaller diameter drivers.

Also, what was the reason for going AP? What were you hoping to gain?

I attempted an AP istalll because I knew I do not have sufficient volume for these divers for a sealed enclosure. I have always read to make the enclsoure volume as small as possible and throw an AP mat in there and everything is good. After completing my install an realizing it doesnt sound good I did further research and concluded that my enclosure volume was too small for this driver.

I think your driver selection is probably fine. I think the problem is the implementation of the AP.

Agree on all points so far, except one. The RS225 is not much of a midbass driver and has great upper midrange for an 8, but is seriously lacking in midbass. For a 3 way it doesn't make a whole lot of sense. I was a bit disappointed when I unboxed mine as well, but bought them for a 2 way which they did pretty well. As for what midbass to run, that'll depend on your mids. Typically midbasses that perform well in your scenario fall flat on their face above 200-300Hz as it generally is best to use a sub if you are looking for the impact that it sounds you are. Of course at those frequencies there is no need to have them as on axis as your install either so if you did rebuild you could save a lot of space.

The on-axis install was a by-product of the minimum-enclsoure-size-install. The mounting depth of the drivers forced the install to be what it is.

That being said, what is the rest of the install? I would always first focus on the majority of the audio spectrum and then make the rest blend and match. That portion you havent' shared.

As I noted above, I have not started my midrange and tweeter install yet. I will be using Dayton Audio RS100T-8 (two per a-pillar) and Dayton Audio RS28F-4 silk dome tweeter. mounted in the a-pillar.

Any idea what volume the enclosures are? I would try and seal up the Aperiodic vent and stuffing the box. It would have a high Q, but may get you the sound you are looking for...

Volume is around .2-.3^3ft.

I only make this suggestion as the high system Q and ripple in response may help the region you feel you are lacking in...

I have used the Variovent in the past. But not for at least 10 years. The advantages never seemed to outweigh the cost of them considering I never had a box that was too small or an usable impedance peak. I also built a few Aperiodic boxes with 3/8" holes drilled in the rear baffle. I never got the results people talked about in places like Speaker Builder and Audio Ametuer. I could also hear air chuffing when I was near-field

I am starting to realize that tuning is key.

My enclosure volume is too small. I have been searching for a different midbass but I am unable to find on that fits my install. I was looking for high QTS, low fs, high QES and small VAS. Preferably 4 ohm and has a mounting depth of less than 3". I am hoping to run my midbass setup from 50-400hz.

My subbass cosist of a single Sundown 18" Z.3 and a DDM3a. I will be changing that in the future to two Sundown 15" Z.3 and a AB VFL450.1. I do not like to run my sub above 50hz.

Should I try and run the RS225-4 as an IB? I could remove the AP mats for an IB install. IS there a better midbass driver available for my install?

[edouble101 314]

If I take out the ap mats and go IB and swap out the RS225-4 for JL Audio ZR800-CW drivers will this improve my midbass response?

[///M5 2,833]

Do you already have the other Dayton's? Using 2 midranges is going to completely defeat the whole purpose of a 3 way install. You also could get by with a much cheaper tweeter as the one you have works in a 2 way with the RS225 if you can use exotic slopes or actually get an RS28 that meets spec. Surprised you haven't given us a dissertation on how the RS28 is the same as the Usher.

The JL might be better, no experience with that driver; however, no matter what the ONLY way to salvage those kicks is to change them to IB. While Honda's idea in general can help, it'll create to narrow of a FR peak with those drivers and they really aren't at all midbasses but midranges that due to their diameter have some reasonable extension.

If you don't have the drivers we'll have a lot more liberty to help as for a car install the ones you've chosen so far don't really work out so well for a 3way. If you do, I'd contemplate flipping/returning and starting over.

[edouble101 314]

Do you already have the other Dayton's? Using 2 midranges is going to completely defeat the whole purpose of a 3 way install. You also could get by with a much cheaper tweeter as the one you have works in a 2 way with the RS225 if you can use exotic slopes or actually get an RS28 that meets spec. Surprised you haven't given us a dissertation on how the RS28 is the same as the Usher.

The JL might be better, no experience with that driver; however, no matter what the ONLY way to salvage those kicks is to change them to IB. While Honda's idea in general can help, it'll create to narrow of a FR peak with those drivers and they really aren't at all midbasses but midranges that due to their diameter have some reasonable extension.

If you don't have the drivers we'll have a lot more liberty to help as for a car install the ones you've chosen so far don't really work out so well for a 3way. If you do, I'd contemplate flipping/returning and starting over.

I do have all of my drivers other than the JL Audio ZR800-CW. I will be use two RS100T-8 per a-pillar, same axis, same plane. What is wrong with that?

I will be switching to IB by removing the AP mats. I agree the RS225 is a poor midbass. Bad decision on my part to use them to begin with.

If both the Dayton are Usher are identical drivers, so be it. Since you brought it up, feel free to elaborate about it.

[edouble101 314]

I changed the view of the graphs which I believe is easier to see.

I removed the AP mat to convert the enclosure to IB. Very interesting results. Overall the graph is similar but not quit as smooth as the AP install. Generally the AP mat install peaks higher. It looks as if the AP mat is a benefit.

Base graph taken on 6.26.12, no EQ, AP mat installed.

AP mat removed, no EQ

I was expecting very different results. Any idea what is going on here? I am curious if my protective cavity that I installed inside the inner fender well is being resistive to air movement.

This is the bottom of the cavity that the AP mat fires into. I have a protective gill at the base to help prevent water and debris from going into the cavity.

Edited June 29, 2012 by edouble101

[edouble101 314]

I still have a 20db peak!

[lithium 358]

how are you taking the measurement? at the head rest,etc?

filters still on?

could be that it's not venting enough air through the grilled vent.

edit: read first post

i'm curious why they are rolling off so early on the top end too.. are they out of phase?

Edited July 2, 2012 by lithium

[edouble101 314]

how are you taking the measurement? at the head rest,etc?

what are the filters set at?

could be that it's not venting enough air through the grill.

Measurements are taking at the driver's side head rest.

What filters are you talking about?

I did some testing to find out if my perforated vent was interfering with the performance of the driver.

With the grill removed the overall response was about 2db higher. That tells me that the grill is slightly affecting output. The removal of the grill also created a nasty dip at 320hz.

No AP mat, no grill

AP mat, no grill

[edouble101 314]

Even after heavy doses of eq I am not satisfied. I can get the RTA curve fairly flat but it still isn't sounding as good as I want it to. I ordered JL Audio ZR800-CW. The driver parameters are much different. I am anxious to see the results.

I am wondering if the huge 100hz spike is cause from the mounting location?

[lithium 358]

50hz@24db and 400hz@12db?

you measuring both left and right together?

[edouble101 314]

50hz@24db and 400hz@12db?

you measuring both left and right together?

Yes those are my crossover settings. I am measuring both left and right together, no t/a. All settings at the amp are flat.

[edouble101 314]

I did switch the polarity of the driver side midbass to see if there was some weird cancellation. The graph after that was not pretty. Lost all output under 100hz.

I looks as though the enclosure size is way to small for this driver. I am seeing about a 24hz/oct roll-off on either side of 100hz.

To convert this setup to IB I am wondering if the hole cutout in the fender well needs to be larger (it is 4 3/8" now). Maybe I am creating a weird resonance in the enclosure with it being the way it is now?

[lithium 358]

i think the problem on the bottem end is enclosure related.

the shit at 300hz might be car acoustics.

edit: are you measuring with doors closed?

Edited July 2, 2012 by lithium

[lithium 358]

measure each side individually once. im just curious, it probably wont show anything

[edouble101 314]

i think the problem on the bottem end is enclosure related.

the shit at 300hz might be car acoustics.

Why the peak at 100hz and the rapid fall-off on either side of it??? I just don't understand that.

[edouble101 314]

measure each side individually once. im just curious, it probably wont show anything

I will do that tomorrow, hopefully.

[lithium 358]

i think the problem on the bottem end is enclosure related.

the shit at 300hz might be car acoustics.

Why the peak at 100hz and the rapid fall-off on either side of it??? I just don't understand that.

i'm not really sure because you have filters on and i cant tell what is a peak.

disable the lpf @ 400hz so we can see establish if the peak at 100hz is a peak. It could be that its fine at 100 and down at 300 and down <100.

[ssh 924]

i think the problem on the bottem end is enclosure related.

the shit at 300hz might be car acoustics.

Why the peak at 100hz and the rapid fall-off on either side of it??? I just don't understand that.

I could be wrong, but it might be from the mounting location being in the kick area. *Cabin characteristics at play*

I haven't modeled your drivers, but the small enclosure volume might throw that peak in.

How thick are your enclosures? Are they deadened inside with any clay, or just fiberglass? Reason I ask, is resonance.

Edited July 2, 2012 by stefanhinote